Gen V dyno - New Vid

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Makara

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Agreed. Question is why do people believe that the amount of power loss to the drive train is proportional to the amount of power (or torque if you prefer) generated by the engine?

Read posts 51 and 55. If a Gen IV viper at it's power peak has a driveline loss of 90 hp, that does not mean that to spin the driveline at all power levels 90 hp is consumed. It only consumes (and consume is incorrect, it actually converts the energy to another type of energy) 90 hp when 600 hp is being driven through it. If the engine is only producing 100 hp in a given moment, a far lower amount of energy would be required to spin the transmission.
 

Stealth

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Yup the Gen 4 ACR Viper is the meanest looking viper period. If I park my ACR next to a Gen V . It would make the Gen V disappear.:)

+1

My Gen IV was my first viper and the first viper for which I liked the looks and performance. Have you [peerblock] ever heard the reference to earlier vipers as a "Clown Shoe"? (See Ronald MacDonald's shoes).

I have never before heard anyone refer to the Gen IV Viper as resembling a Honda 2000 (great little car, but really different).

Many of us wanted the Gen V to evolve more in the direction of the Volado concept with 700hp vs. going back to Gen II looks and Gen IV.1 performance. The fact that you (Peerblock) and others are enamored with the Gen V is great for SRT and supports continuation of the proud Viper line--a great result because it support developlment of future Vipers. This does not mean that others of us who had hoped for more power and progressive styling will part with $130k--$150k (including taxes) for the Gen V. Again, glad you like it, but each to his or her own.
 

PeerBlock

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Only if those $14,000 paint jobs weren't holding the Gen V's back, then the VTEC could really put down some powers.

According to honda guys, a slicker paint job improves aerodynamics and top speed potential.

We are talking about vipers and 4th gear is 1:1

No, we are talking about dyno numbers and whether or not the Gen 5 is posting numbers that are too low for its factory ratings. This discussion is more about the accuracy of dynojet figures, as well as how useful they are in comparing cars.

But the higher rate at a reduced torque should equal it's self out when calculated into power unless less power is actually being delivered.

There is a formula for calculating HP from torque and RPM. It has already been posted so you can work it out yourself.

Umm, no, it's about heat. Remember conservation of energy? That energy lost between the engine and the wheels goes somewhere, and that is mostly heat. Energy doesn't just disappear, it is transferred to another type of energy.

Nobody is suggesting that the energy is not dissipating as heat; but it's not heat itself that is responsible for the driveline power loss. That loss comes from the inertia of the engine and driveline.

Actually, you can't infer that at all. Tricky of you to put in a torque value rather than power, but either way, the parasitic loss of a transmission is not the same at full power as it is at low power. The greater the power, the greater the loss. Drive your car lazily and see how hot the transmission tunnel gets. Now drive the crap out of it at the race track and see how hot it gets. Where is that heat coming from? Transference of energy, from kinetic to thermal. Conservation of energy...

How is it tricky? Power is a calculated figure; it's an abstract concept that we use to determine the ability of a machine to do a certain task efficiently. Torque is what we measure as far as output from an engine's crank. The heat from the transmission is due to friction, and while the coefficient of friction should remain fairly static the faster the driveline spins the more friction it incurs, and thus more heat is produced. This isn't what we're talking about here.

You are dead right, it doesn't magically increase, it increases because of physics which it turns out isn't magic at all. Let's say that engine is outputting the same power with the turbo as it did without under the current load, the parasitic loss would be the same as before it had the turbo on it. Once the load is increased and power output rises, the losses will be greater, mostly due to heat.

No, the driveline is the same as it was before. The apparent loss is a result of the engine having to work harder to rotationally accelerate itself and the driveline faster. The load does not increase because you improved the engine's performance; the load is a function of the rate of acceleration in RPMs.

You started off correct. It isn't a fixed percent of power loss. There is a certain amount of power required to turn a transmission and beyond that, a portion of the power produced will be lost, but a fixed percentage seems to be a rather decent guideline to work off of. You don't want to calculate your stock driveline loss and assume that at all loads and all power outputs it will be the same because that is quite inaccurate. If a viper engine required 100 hp just to spin it's transmission at any speed, our engines would be working a heck of a lot harder when pulling into a parking spot.

Actually it is. It takes a specific amount of torque to twist the crankshaft, and the driveline connected to the crank. There is a "bare minimum" amount of torque that must be applied when the transmission is in a 1:1 gear.

Your final sentence is incorrect because you forget that we shift gears while driving for the very purpose of torque multiplication. Reverse gear is typically at or near 4:1, meaning that the engine crank spins 4 times for every 1 revolution of the driveshaft, effectively multiplying the engine's torque by 4 while dividing its power by 4.

There is a 1:1 (technically 1.00) gear ratio in just about every transmission ever built. In most 4-spd manuals, it is 4th gear. They had no overdrive. In every T56 and TR6060 (Viper Transmissions) it has always been 4th gear. I've not seen any transmissions use 3rd 1.00 except for the 3-speed TH350/TH400 GM automatics. In the GM 2-spd Powerglide, it is 2nd gear 1.00.

You can say this - just about every transmission does have a 1:1 gear especially popular american transmissions. But it is wrong for Jack B to say that all transmissions do, and I'm not talking about esoteric race-only tranmissions. Certain import vehicles with close-ratio transmissions from the factory do not have a 1:1 drive.

Your statement is correct, if we are discussing turning the driveline at a constant speed. But, we are accelerating the driveline, not simply turning it. The quicker the rate of acceleration, the more power it requires to turn the driveline. For a similar example, consider a vehicle travelling 200+ mph, and the wind resistance that it sees. In order to accelerate from 200-220 mph, a car with more power can do so in a quicker amount of time. You may compare two vehicles that both can reach 220 mph, but the more powerful one would achieve it sooner, and fight the wind resistance (drivetrain loss) better.

Yes, you need more power to accelerate the engine's crank and driveline at a faster rate, but that doesn't mean that the driveline has developed a higher coefficient of friction or increased inertia than it had before the engine performance was improved. This again highlights the flaws of using a dynojet's method of measuring engine torque since it is allowing the inertia of all the rotating components from the engine to the wheels affect the measured numbers.

To your example with cars going from 200 to 220 MPH, both cars can reach that speed but one can do it quicker because it has a stronger engine. Its engine will have to overcome a higher degree of wind resistance but that doesn't mean that the higher powered engine is "losing" power for attempting to be faster. It's just that as you accelerate, you need more power to do so more quickly - this is well-known and the reason people want to improve their engine's performance in the first place.

Peer Block:

Maybe this will help

1. All manual transmissions have a direct drive and it is not dependent on gears.

No they don't. Many do, but not all.

2. That direct drive has nothing to do with gears, I feel like I have to be redundant.

If the power of the engine is being transmitted through the transmission then the gearing does matter. If you can't explain yourself any better than making a generalized statement and expecting everyone to simply accept it as truth then you probably don't understand what you're talking about.

3. When you are in direct drive the input and output shaft are COUPLED together. The only other gear that is rotating is the cluster gear, therefore, losses are at a minimum.

Sure, in transmissions that have a direct drive feature this is true.

4. Virtually all manual transmissions have 4th gear as direct drive. If you disagree, name me three (4/5/6 speeds) that are not. BTW -what started this thread tangent was your claim that all dyno pulls are in 3rd gear.

LOL you can do your own research bro. Maybe do a little before posting again so you can stop being wrong. The internet has enough self-proclaimed "experts" who get to be experts because their statements largely go unchecked. You're being checked and you're not making the grade.

5. I have seen uninformed dyno operators use third gear - they just did not know better, therefore, their offspring think 3rd gear is the correct gear.

Much like you think all transmissions have a direct drive that entirely bypasses the gearbox...

6. I do not know if this was mentioned, but, the dynojet dyno does not directly measure HP, they measure torque, we then calculate the HP - I believe that is an accurate statement, if not, let me know..

Finally, you got one right...except that I already stated this several times before.

Sorry about the tongue and cheek, but, you are are hard person to get to admit he was wrong. As far as my background, two engineering degrees, I have participated in well over 100 dyno pulls and I have a T56 torn apart right now and most important, I use the viper for its god given purpose - to race.

And if this were a conversation about politics you'd no doubt be a war veteran who "knows better" because he was on the front lines....and if we were talking about space travel you'd be Scotty, a warp field expert.

Most of what you're saying seems to be limited to a fairly narrow subsection of the automotive community as a whole. This thread is about dyno jet efficacy. Attempting to say it's "just about the viper" so your statements hold true is a sign of ignorance. My point was and still is that dyno numbers are perhaps one of the least credible ways of comparing different cars to each other to the many variables that can affect the numbers you end up with.

My post was not in relation to your prior comments. It was more or less calling out PeerBlocks ridiculous and uneducated S2000 rant, which happened to be mixed in with his other long winded nonsense.

Who else thinks the older Viper and S2000 share a common origin?
 

ViperGeorge

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Read posts 51 and 55. If a Gen IV viper at it's power peak has a driveline loss of 90 hp, that does not mean that to spin the driveline at all power levels 90 hp is consumed. It only consumes (and consume is incorrect, it actually converts the energy to another type of energy) 90 hp when 600 hp is being driven through it. If the engine is only producing 100 hp in a given moment, a far lower amount of energy would be required to spin the transmission.

Best I can tell by doing all kinds of research on this point is that the correct answer is neither a set percentage nor an absolute power figure. While there is a constant amount of force required to spin a given mass of gears, other factors such as oil shear and tire deflection can cause the actual absolute power required by the driveline to increase as torque increases. However, it is not a linear relationship and will not stay at the same percentage as power increases. It also will not stay at the same absolute HP figure either.
 

chorps

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Heh that was cute. Too bad the end result of the search showed only 2 links (out of all the main page links) comparing the two vehicles in styling. The first was a refutation filled with busted image links, and the second was a single post claiming what you thought on a honda forum, and then everyone else asking him what kind of crack that he was on so they could get some.

Granted there is some passing similarity but they are really nothing alike, especially when seen in real life. Sure is fun ribbing Gen III and IV vert owners though.
 

SLViper

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Heh that was cute. Too bad the end result of the search showed only 2 links (out of all the main page links) comparing the two vehicles in styling. The first was a refutation filled with busted image links, and the second was a single post claiming what you thought on a honda forum, and then everyone else asking him what kind of crack that he was on so they could get some.

Granted there is some passing similarity but they are really nothing alike, especially when seen in real life. Sure is fun ribbing Gen III and IV vert owners though.
Well they both have 4 wheels, a windshield and are Verts? Spooky
 

Jack B

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PeerBlock

You are very good at diversion, however, I will concede that you are the almighty if you can name me TWO conventional transmissions where direct drive is 3rd gear and two conventional transmissions that do not have a direct couple path from input to output? When you started in on this thread, it was about 3rd gear being the correct gear for a dyno pull, where did you pull that from, that is the reason for this discourse - by the way I am not your bro, far from it!

i think all that myself and a host of others were trying to do was point out an obvious error, it seems like you are always right even when you are wrong. Lastly, your comment on veterans of a war, is way out of place. that tells us a lot about you. I am bowing out, there is no further reason for a one way discourse. I have to leave, going racing, I am sure you will be busy also, on your keyboard doing research.
 

elanderholm

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I had an s2000 for five years and the acr now for a couple. They overall shape and feel of the cars are similar. But, it's not like they look like twins or anything, but their shape and some design cues look similar.
 

Makara

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There is a formula for calculating HP from torque and RPM. It has already been posted so you can work it out yourself.

Yes, I know the formula. I imagine anyone who has a basic understanding of cars knows it and that it was derived by how much power James Watt estimated a horse could generate based off of what he observed a pony could generate. At any rate, my point is that the different gearing in the differential has a small effect on the efficiency of the power transfer from the drive shaft to the wheels. This is not because the dyno spins at a different rate, as you suggest as if the differential were to be 100% the same in efficiency from on ratio to another, the torque decrease due to lower numerical gear ratio would be offset by a higher rate in the same proportion, which would end up with the same value in power once rate and torque are multiplied, then divided by 5252. Like others, I'm done beating my head into a wall trying to just provide some insight as to where the power goes when run through a transmission. Flipping through some physics books and reading about conservation of energy and how to calculate friction should shed some light on some of what is going on.
 

Steve M

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No, we are talking about dyno numbers and whether or not the Gen 5 is posting numbers that are too low for its factory ratings. This discussion is more about the accuracy of dynojet figures, as well as how useful they are in comparing cars.

Is that what we are talking about here? This seems to have gotten lost in your rambling.

Let's do a quick recap...looking at the post below, you'll note that the Gen IV and Gen V were on the same dyno on the same day.

I've been too busy with work this week to post my own thread, but last weekend I had mine dyno'd (on a Dynojet) with 600 miles on it. The results were odd, the first pull was 506 and pull #2 increased to 529. It seems like something caused timing to be pulled on run 1 but I have no idea what, the curves are similarly shaped with no odd drops (just a gradual difference) so I do not think it was slippage anywhere (tires or clutch). Maybe if my first run would have gone right before some heat soak set in I would have seen 535-540, but who knows.

For comparison there was a 08 Viper there, the only mods being the 4 stock cats swapped to 2 high flow cats and different mufflers. He dyno'd 535 on run 1 and 526 on run 2. So it appears this dyno naturally is lower than other dyno's (I thought this 2 years ago when my G8 dyno'd a solid 20 less than I was expecting). But what I think this definitely proves is that our 40 hp increase is on paper only, the 08-10s were under rated and the 13+ are rated correctly.

Was it truly apples to apples? No, because the Gen IV wasn't 100% stock, and the Gen V was. Minus the high flow cats on the Gen IV, the only other differences are the lighter clutch/flywheel combo on the Gen V (advantage Gen V, but doesn't always show up on a dyno), and as noted below, the ring and pinion as noted by Nine Ball:

A car will also dyno higher with the 3.07 gears, compared with the 3.55 gears in the Gen 5.

This is the heart of the discussion here...so the Gen IV had 3.07 gears, high flow cats, presumably dynoed in 4th gear (1:1) and put down 535 RWHP on its best run. The Gen V has stock 3.55 rear gear and was also presumably dynoed in 4th gear (1:1), and put down 529 RWHP on its best run.

And then you come in with this wonderful post:

Third gear is usually 1:1 if no changes were made to the vehicle, and that's the gear used in a dyno test. If your car comes stock with 3.07 and you change to 3.55 or 4.10 gears then 3rd gear would no longer be 1:1 and you'd see higher dyno numbers, which would have to be compensated for to get accurate HP/TQ figures.

...and that's where everything fell apart, and where everyone (including me) disagreed with your logic. To your credit, comparing a Gen III/IV Viper to an S2000 was nice and classy...why admit you were incorrect when you can just make fun of how something looks?

So to be clear, third gear in a Viper has never been 1:1, so your statement that it usually is is not true, especially not in this context...after all, we are on a Viper forum, and we are talking about Vipers here. As for the last part of that statement, that is not only false, it is so wrong that I'm not even sure what you were thinking. Since when do a ring and pinion change have an impact on transmission gear ratios? If your answer is "sometimes", please stop before you hurt yourself.

Are you talking about 1:1, as in one tire rotation per one engine revolution? Oh hell...let's do some math.

The Gen IV Viper dynoing in 4th gear (1:1) with a 3.07 ring & pinion combo will still net you a 3.07 final drive ratio (1 x 3.07 = 3.07). That's certainly not 1 tire rotation per 1 engine revolution. Let's put that ***** in 3rd gear (1.30:1). That will net you a final drive ratio of 3.991 (1.3 x 3.07 = 3.991). Holy crap...that's even further away from a 1:1 ratio. 5th gear perhaps? That gives us a 2.30:1 final drive (0.75 x 3.07). Well...maybe we need to change the rear gears out. Let's see here...if we drop a set of 3.55s in there, third gear is still 1.3:1, and 4th 1:1. That didn't work. How about 4:10s? Nope...3rd and 4th gear still haven't changed ratios.

So...what exactly were you thinking? I'm trying hard to figure it out.
 

mnc2886

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PeerBlock, I have owned a couple of performance cars at my younger age (not really that long ago :)) and with the same car, same dyno, a change from 3.42 to 4.10 resulted in a loss of 17 HP. The next rear gear I went to was a 3.73 and I gained about 9 horsepower back. That was a starting point of 415 rwhp. Significant percentage change. Let's put this in perspective. The gear change I had from 3.42 to 4.10 is close to a change from 3.07 to 3.55. Given that I saw a 4% decrease in the dyno reading due to increased parasitic loss, a average Gen IV Viper that dyno's 545 rwhp will dyno at 523. Now we add the claimed 40 horsepower increase (net 38 since we are losing 4% in this hypothetical scenario) we end up at 561 rwhp. That is pretty damn close to what the dyno readings are coming back at.

I work in engineering with industrial engines and our packages have two factors of parasitic loss. In both of those factors, the faster we spin the object, the more horsepower it takes. You are correct in saying it takes 'x' horsepower to spin the drive-train. However, you are forgetting that the rate at which you reach that speed factors into the horsepower used to rotate the object. Let's put it in the simplest terms. How can you argue that a car accelerating from 0-100 MPH in 10 seconds takes the same horsepower it takes to accelerate the same car 0-100 in 7 seconds? It is simple, it doesn't. In other words, a 3.55 will have greater resistance to spin than a 3.07, but that is a performance advantage given the fact that the engine will enter its power-band at an earlier time frame thus resulting in quicker acceleration at lower speeds. Conversely, it results in slower acceleration at higher speeds once you get to a certain point.
 

VENOM V

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Not only has this horse been beat to death, but it is now just a gooey glob of glue, lol.

The only thing I will add is that the Gen IV is a beautiful machine, as are all gens. Tolerance, gentlemen.
 

I Bin Therbefor

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Osamu Shikado, ex Toyota designer, under the tutorage of Freeman Thomas, ex Audi designer (TT) both of whom were then at DiamelerChrysler, is generally credited with the design concept for the Gen III. Freeman Thomas picked that design from an internal competition. The change in design direction was very contraversal within Chrysler and within the Viper community, VCA included. Shikado was quoted using the term clown shoe in a very disparaging manner about the Gen I/II. Lutz is credited with saying, "I think the styling has become what I like to refer to as "sanitized for your protection". . . I don't think it has the boldness, and the presence and uniqueness of the original Viper and Viper GTS." The action on the forum become so strong and negative that the moderators had to step in and stop the threads that were anti Gen III styling. Ralph took the original styling theme and added an organic element.

You pays your money and takes your pick. However I dont think you have to defend your pick by making disparaging remarks about someone else's pick. Personally, I very much appreciate the results of the addition of the organic element to the original styling direction. Ralph came to Chrysler because of the Gen I Viper, I'm glad he stayed and very much approve of what he is doing with the Viper and the SRT brand.:2tu:
 

PeerBlock

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Granted there is some passing similarity but they are really nothing alike, especially when seen in real life. Sure is fun ribbing Gen III and IV vert owners though.

Ya'll are way too sensitive and lacking in the sense of humor department. I guess it's just the jealousy that all the people are loving my big red clown shoe, especially the ladies, because they know what a big shoe means.

PeerBlock

You are very good at diversion, however, I will concede that you are the almighty if you can name me TWO conventional transmissions where direct drive is 3rd gear and two conventional transmissions that do not have a direct couple path from input to output?

If by diversion you mean sticking to the facts...

Ratios for Evo 8 & 9
http://www.jackstransmissions.com/pages/evo-8-9-transmission-gear-ratios

Ratios for SRT-4 (second post down):
http://www.turbo-mopar.com/forums/showthread.php?16051-T-850-(SRT-4-trans)-gear-ratios

Ratios for Toyota Supra (use ctrl+f and search for "Transmission Types"):
http://mkiv.supras.org.nz/specs.htm

The supra does have a 1:1 drive, but it's in 5th gear on the Getrag trans (the 6-speed manual). Throwing that in there to counter the derpness of claiming that it's always 4th gear.

All of those tranmissions are what you get from the factory, stock and all but the supra are LACKING in a 1:1 drive gear.


When you started in on this thread, it was about 3rd gear being the correct gear for a dyno pull, where did you pull that from, that is the reason for this discourse - by the way I am not your bro, far from it!

Which is often the case if you're dynoing an automatic transmission...although I did not specify which car I dynoed so to claim I was wrong for saying it is 3rd once again highlights that you're going to be assumptive rather than simply acknowledging that you know what I meant - that dyno pulls are typically done in the gear that yields 1:1 or closest to it. The reason for this discourse is that you and anyone else who disagreed with me is trying to save face rather than simply learning something new and moving on with life.

i think all that myself and a host of others were trying to do was point out an obvious error, it seems like you are always right even when you are wrong. Lastly, your comment on veterans of a war, is way out of place. that tells us a lot about you. I am bowing out, there is no further reason for a one way discourse. I have to leave, going racing, I am sure you will be busy also, on your keyboard doing research.

Except that the only ones in error were you and "the host of others" blindly agreeing with you.

I had an s2000 for five years and the acr now for a couple. They overall shape and feel of the cars are similar. But, it's not like they look like twins or anything, but their shape and some design cues look similar.

Yes. The body lines look very similar, especially the headlights, the windshield and the overall stance.

Like others, I'm done beating my head into a wall trying to just provide some insight as to where the power goes when run through a transmission. Flipping through some physics books and reading about conservation of energy and how to calculate friction should shed some light on some of what is going on.

Never disagreed with you that excess energy was being dissipated as heat - that is essentially correct; I disagreed with you that the heat itself was causing a driveline loss on the dyno readings.

Is that what we are talking about here? This seems to have gotten lost in your rambling.

Let's do a quick recap...looking at the post below, you'll note that the Gen IV and Gen V were on the same dyno on the same day.

Was it truly apples to apples? No, because the Gen IV wasn't 100% stock, and the Gen V was. Minus the high flow cats on the Gen IV, the only other differences are the lighter clutch/flywheel combo on the Gen V (advantage Gen V, but doesn't always show up on a dyno), and as noted below, the ring and pinion as noted by Nine Ball:

I was never concerned with the comparison of the Gen 5 and Gen 4 dyno numbers - my point was and still is that dyno numbers are not something that should be taken too seriously. They are useful for tuning a car and getting a rough idea of what to expect when you take the car out to the race track or drag strip, and the numbers you get should be within 10-20% of the factory ratings assuming nothing has been done to the car...but let's reiterate that 10-20% is a pretty wide margin of error.


This is the heart of the discussion here...so the Gen IV had 3.07 gears, high flow cats, presumably dynoed in 4th gear (1:1) and put down 535 RWHP on its best run. The Gen V has stock 3.55 rear gear and was also presumably dynoed in 4th gear (1:1), and put down 529 RWHP on its best run.

I've already established the context for which I was posting. You can say that is the heart of your perspective on this discussion, and to that I'd say the difference between 529 and 535 less than 2%. If you think a dyno has such a narrow margin of error I'd like to offer you some beachfront property right outside of Las Vegas.

...and that's where everything fell apart, and where everyone (including me) disagreed with your logic. To your credit, comparing a Gen III/IV Viper to an S2000 was nice and classy...why admit you were incorrect when you can just make fun of how something looks?

Funny how easy it is to jump on a bandwagon believing that "groupthink" is on your side, only to discover that you and the others were wrong.

So to be clear, third gear in a Viper has never been 1:1, so your statement that it usually is is not true, especially not in this context...

Except that the context is cars in general, not "viper only", and since the point was that the transmission should be at or near 1:1 for a dyno pull I was never wrong about that.

after all, we are on a Viper forum, and we are talking about Vipers here. As for the last part of that statement, that is not only false, it is so wrong that I'm not even sure what you were thinking. Since when do a ring and pinion change have an impact on transmission gear ratios? If your answer is "sometimes", please stop before you hurt yourself.

We're on a car forum focused on vipers where we can and do talk about vipers as well as how it compares to other cars. Is this a weak attempt at moving the goalposts since you never had a reason to disagree with me in the first place?

Are you talking about 1:1, as in one tire rotation per one engine revolution?

So...what exactly were you thinking? I'm trying hard to figure it out.

Woops, you got me there. I did make an error regarding the relationship of the engine speed to final drive. Go give yourself a high five!

PeerBlock, I have owned a couple of performance cars at my younger age (not really that long ago :)) and with the same car, same dyno, a change from 3.42 to 4.10 resulted in a loss of 17 HP. The next rear gear I went to was a 3.73 and I gained about 9 horsepower back. That was a starting point of 415 rwhp. Significant percentage change. Let's put this in perspective. The gear change I had from 3.42 to 4.10 is close to a change from 3.07 to 3.55. Given that I saw a 4% decrease in the dyno reading due to increased parasitic loss, a average Gen IV Viper that dyno's 545 rwhp will dyno at 523. Now we add the claimed 40 horsepower increase (net 38 since we are losing 4% in this hypothetical scenario) we end up at 561 rwhp. That is pretty damn close to what the dyno readings are coming back at.

I don't have a problem with anything you said here, except that you're putting a lot of faith in the readings you get from a dynojet, readings which should include a disclaimer that they are calculated using a healthy dose of fairy dust. If you went from a theoretical 3.00 rear axle gear to 4.00 and had the driveshaft spinning 1:1 with engine crank, every 3 turns of the engine with 3.00 gears would cause one complete revolution of the rear axle. With the 4.00 gears it would be 4 driveshaft revolutions to turn the rear axle one complete revolution.

You're not losing engine power; the dyno shows a lower reading because for any given RPM, the taller gears require more revs to spin the drum, which means that the time it takes the engine to accelerate the drum increases. In other words, since power is the rate at which torque can be applied by the engine, more power is used to turn the taller gears due to the difference in ratio.

The most relevant factor with gearing is keeping the engine revs in its powerband, and depending on how the transmission is geared, the rear axle should also be geared accordingly. For instance, if you tune the engine for mid to high RPM power, there is a benefit to using taller rear axle gearing >4. But if you're running a broader power band with more low and mid range, you can go with shorter gears to gain better overall utility while driving "normally". I think 3.55s are just right for the Viper.

I work in engineering with industrial engines and our packages have two factors of parasitic loss. In both of those factors, the faster we spin the object, the more horsepower it takes. You are correct in saying it takes 'x' horsepower to spin the drive-train. However, you are forgetting that the rate at which you reach that speed factors into the horsepower used to rotate the object. Let's put it in the simplest terms. How can you argue that a car accelerating from 0-100 MPH in 10 seconds takes the same horsepower it takes to accelerate the same car 0-100 in 7 seconds? It is simple, it doesn't. In other words, a 3.55 will have greater resistance to spin than a 3.07, but that is a performance advantage given the fact that the engine will enter its power-band at an earlier time frame thus resulting in quicker acceleration at lower speeds. Conversely, it results in slower acceleration at higher speeds once you get to a certain point.

Well, the using those theoretical ratios again, 3.00 and 4.00, going from 3 to 4 is a 33% increase in revs required to spin the rear tires once.

With 3.00 gears and 3,000 RPM engine/driveshaft speed, the rear axle should be spinning at 1,000 RPM.
Same thing, but with 4.00 gears and the rear axle spins at 750 RPM, a loss of 250 revs at the wheels or a 25% loss in rotational speed.

Using 4.00 gears in the rear axle, the engine would have to be at 4,000 RPM to match the the speed of the 3.00 gears, and wheel revs are what is used to calculate horsepower with a dynojet.

Scale that up to 6,000 RPM and with 3.00 gears the wheels spin at 2,000 RPM while 4.00 gears only get 1,500 RPM - the 25% loss in revs remains constant since the gear ratios are fixed, but that's 500 fewer revs reaching the wheels which are correctly calculated as a power loss as far as what's getting to the wheels - and that's without factoring in inertial or frictional losses (which I would say play less of a role than they are often credited for in this case).
 
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chorps

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Osamu Shikado, ex Toyota designer, under the tutorage of Freeman Thomas, ex Audi designer (TT) both of whom were then at DiamelerChrysler, is generally credited with the design concept for the Gen III. Freeman Thomas picked that design from an internal competition. The change in design direction was very contraversal within Chrysler and within the Viper community, VCA included. Shikado was quoted using the term clown shoe in a very disparaging manner about the Gen I/II. Lutz is credited with saying, "I think the styling has become what I like to refer to as "sanitized for your protection". . . I don't think it has the boldness, and the presence and uniqueness of the original Viper and Viper GTS." The action on the forum become so strong and negative that the moderators had to step in and stop the threads that were anti Gen III styling. Ralph took the original styling theme and added an organic element.

If they would have built the 2000 GTS-R concept like it was, I doubt there would have been as much hand wringing...I think they really watered down the original concept for the production Gen III vert. The rear fender swell, big wing, the long tail, roof intake and lower aero added a lot of drama that weren't on the production car.

http://www.carstyling.ru/en/car/2000_dodge_viper_gts_r_concept/images/13211/

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chorps

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Ya'll are way too sensitive and lacking in the sense of humor department. I guess it's just the jealousy that all the people are loving my big red clown shoe, especially the ladies, because they know what a big shoe means.

Big shoe = lots of toe jam?
 
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ACRucrazy

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Oh. My. God.

This is a Gen V dyno thread. This discussion is around the Viper.

Not about the S2000, the SRT-4 (transaxle), Evo (transaxle) or Supra.
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PeerBlock

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Oh. My. God.

This is a Gen V dyno thread. This discussion is around the Viper.

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Imperts!? Thisseer's the dangole dodge ... NO .... itz the SERTY ferum an we dont talk about no CHAI-neese impertz on thisser ferm... Dem cars dont count tellem cletus! Real cars have 8 cylinders an real trux dont use no daggone spark plugs.

Not about the S2000, the SRT-4 (transaxle), Evo (transaxle) or Supra.

Now ahma gon tell u bout dem transaxle types usen bold with EYE taliks.
 

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PeerBlock: You still haven't given us an example of a manual transmission that uses 3rd for 1.00 (or close to 1.00). Just admit you made a typo, it would be easier than seeing the excuses. I've dyno'd hundreds of cars myself, and generally 4th gear is used in a manual car. Only a few oddballs use 5th, but I've never seen a 3rd gear.
 

PeerBlock

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PeerBlock: You still haven't given us an example of a manual transmission that uses 3rd for 1.00 (or close to 1.00). Just admit you made a typo, it would be easier than seeing the excuses. I've dyno'd hundreds of cars myself, and generally 4th gear is used in a manual car. Only a few oddballs use 5th, but I've never seen a 3rd gear.

I haven't made a single excuse since I was never wrong. lol You need to get over that, and yourself.

Third is pretty close to 1:1 on several of the transmissions I listed for brother Jack, since they are what's known as "close ratio" transmissions.

The dyno pulls I have done were done to tune the car, not to be an entry into an internet ******* contest about how much WHP I'm putting out. Since the car that was tuned uses 1-3 most of the time in hard driving, 3rd gear was chosen as the basis for tuning.

You can do pulls in 3rd gear or any gear since the dyno is tracking engine speed as well as wheel speed; pulling in 1:1 gives you the most optimistic numbers so you can tell everyone how much more HP your car has but it is not a requirement in any way...but I'm sure you already knew that with those hundreds of dyno pulls on your resume.
 

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Keep posting, we are enjoying your clueless technical responses. Pure comedy!

I have to admit, you sure do a good job of typing all sorts of technical stuff, even if the content is technically incorrect. Some less technical people would likely believe you.

So, please enlighten us with your brilliance of tuning 3rd gear "racecars". What sort of car is this? What transmission? Why didn't you just use 1st gear to tune, if you thought 3rd was better than 4th?
 
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commandomatt

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It's amazing to me how someone can actually destroy a thread with pure arrogance and a 'know it all' attitude

Also the idea of suggesting that because you like the Gen3 and 4 design, and defend it.....you are actually just jealous !!!! Jealous of what ??....that I don't agree with someone else's taste. Plain stupid to even make a comment like that.

Fact is that I absolutely love everything about my 06 Coupe design and have yet to accept the new Gen design as one that I would consider buying. Personally I think the Gen 5 looks to much like a slightly improved 20 year old design.....not the fresh and aggressive design I was hoping for.

That's my take but I can also appreciate that some prefer the 5's. So we have different tastes.....doesn't make one right or wrong, its just the way things are. To say that everyone that doesnt agree with your opinion is insecure and jealous....well that says a whole lot about your personality.

Matt
 

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Scale that up to 6,000 RPM and with 3.00 gears the wheels spin at 2,000 RPM while 4.00 gears only get 1,500 RPM - the 25% loss in revs remains constant since the gear ratios are fixed, but that's 500 fewer revs reaching the wheels which are correctly calculated as a power loss as far as what's getting to the wheels - and that's without factoring in inertial or frictional losses (which I would say play less of a role than they are often credited for in this case).

The same gearing that causes the reduced rate also increases the torque, yielding the same power assuming 100% drive-train efficiency.

I'm with Nine Ball, this whole thing is getting rather comical.
 

PeerBlock

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Keep posting, we are enjoying your clueless technical responses. Pure comedy!

I have to admit, you sure do a good job of typing all sorts of technical stuff, even if the content is technically incorrect. Some less technical people would likely believe you.

So, please enlighten us with your brilliance of tuning 3rd gear "racecars". What sort of car is this? What transmission? Why didn't you just use 1st gear to tune, if you thought 3rd was better than 4th?

When you can't respond to the points I've made using a logical argument it's time to direct the comments toward me directly. I find that amusing, because a self-proclaimed "dyno expert" runs out of steam so fast and has to postulate rhetorical questions that, to an expert like himself, should be obvious.

You can use 1st, 2nd, 3rd or 4th but for a dyno pull - but why would you tune the car for 1st gear if your aim is to maximize performance in 3rd? Likewise, why would you tune in 4th gear if you rarely shift into 4th gear for your style of driving? Are viper owners so shallow that the only reason they dyno their cars is for bragging rights on threads like this rather than to improve performance?

It's amazing to me how someone can actually destroy a thread with pure arrogance and a 'know it all' attitude

I know right! What's with these "dyno experts" coming in here acting like their word is doctrine. Tuning a vehicle on a dyno is more art than it is science. If it were purely scientific there would be little or no discrepancies between the results you get with the various ECU tuners out there.

Also the idea of suggesting that because you like the Gen3 and 4 design, and defend it.....you are actually just jealous !!!! Jealous of what ??....that I don't agree with someone else's taste. Plain stupid to even make a comment like that.

If the comments were made to be spiteful, perhaps the "defense" would be warranted. I thought it was fairly obvious that I was joking around about that but these S2000 owners are a serious bunch, apparently. You making this comment plays into that whole "can't take a joke" vibe we're getting from people driving around in V10 hondas.

Fact is that I absolutely love everything about my 06 Coupe design and have yet to accept the new Gen design as one that I would consider buying. Personally I think the Gen 5 looks to much like a slightly improved 20 year old design.....not the fresh and aggressive design I was hoping for.

Well, that puts you in a very small minority. Enjoy your 06; I'm loving my 13.

That's my take but I can also appreciate that some prefer the 5's. So we have different tastes.....doesn't make one right or wrong, its just the way things are. To say that everyone that doesnt agree with your opinion is insecure and jealous....well that says a whole lot about your personality.

Wait, who said anything about the choice to own a Gen 4 being "wrong" now that the Gen 5 is available? I sure didn't...but maybe I did and forgot that I wrote that? Hmm... Bottom line is that anyone who is so up-tight about their toy car needs to relax and take a chill pill. Can't see the point in getting all stressed out about nothing.

The same gearing that causes the reduced rate also increases the torque, yielding the same power assuming 100% drive-train efficiency.

I'm with Nine Ball, this whole thing is getting rather comical.

Sure, but it doesn't translate quite so linearly to actual performance. Since the power band of any automobile engine falls withing a predefined RPM range, the revs that you lose with taller gearing are not recuperated even though "technically" no power is ever given up.

Let's use my 3.00 and 4.00 theoretical final drive gears:

With 3.00 @ 6,200 RPM using direct drive (1:1) wheel speed is 2,067 RPM.
Same with 4.00 gears in rear axle, wheel speed is 1,550 RPM.

You can plug the wheel RPM into the HP equation to figure out what the theoretical WHP would be:

(Estimating Viper has ~500 ft-lbs of torque at the crank @ 6,200 RPM)

3.00 Gears (2,067 RPM * 1500 ft-lbs) / 5252 = 590
4.00 Gears (1,550 RPM * 2000 ft-lbs) / 5252 = 590

Even though no power is lost, you give up 25% of your revs because you are limited by the 6,200 RPM redline of the engine. In "real world" driving this means that taller gearing reduces the top speed in each gear as well as the overall top speed of the car, but the additional torque you gain allows you to reach the redline quicker thus making the car "feel" faster while driving it.

In drag racing this would mean lower trap speeds and possibly higher ETs (as long as you do not gain an extra shift due to gearing), while in road racing it would mean that your car is not going to pull as hard and you'll have to shift more often. You would start to get counterproductive effects if the taller gearing required you to shift into a higher gear at lower speeds, dropping the engine out of its powerband due to running out of revs in the previous gear.
 
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