WHAT IS THE MAX ENGINE RPM ON A 2001? 56 HP PER LITER SEEMS VERY LOW...

[EXECMALIBU]

WHAT IS THE MAXIMUM RPM A 2001 VIPER ENGINE SHOULD BE REVVED TO AFTER BRAKE IN?

MOST MANUFACTURERS PUT A VERY CONSERVATIVE REDLINE ON THE TACH..

MANY CARS I OWN PULL HARD WAY PAST THE REDLINE AND NEVER HAVE SUFFERED ANY DAMAGE...SOMETIMES AS MUCH AS 1,500 RPM OVER REDLINE.(1973 911S.. REDLINES AT 7,200 PULLS HARD TO 8,500+ RPM, 58 SPEEDSTER REDLINES AT 6,000 PULLS EASILY TO OVER 7,500 RPM )

WHAT IS CONSIDERED A SAFE OVER REV ON THE V-10 WITH SMOOTH TUBES/K&Ns?


IT SEEMS LIKE THE D/C RATING OF 56HP PER LITER FOR THE V-10 IS VERY LOW FOR A HIGH PERFORMANCE ENGINE..

MOST OF THE OTHER CURRENT HIGH PERFORMANCE CARS ARE RATED AT 80-110 HP PER LITER.. LIKE THE VETTE,NSX,PORSCHE FERRARI ECT... HELL EVEN SOME OF THE CHEAP ECONO-BOXES ARE AT 60-70 HP PER LITER..

BACK IN THE SIXTIES MOPAR,GM AND FORD WERE ALL RUNNING AROUND 70+HP PER LITER ON 2 VALVE CARBURETED STREET MOTORS..

IN 1966 THE FERRARI 3 LITER WAS AT 100HP PER LITER AND THE PORSCHE 906 2 LITER WAS AT 120HP PER LITER!!.. BOTH HAD NORMALLY ASPIRATED 2 VALVE HEADS..

IT SEEMS LIKE THE INJECTED AND COMPUTER CONTROLLED V-10 SHOULD EASILY PUT OUT MORE HP THAN 56HP PER LITER..WAS THE POWER INTENTIONALLY LIMITED BY DODGE?

 

[Craig 201 MPH]

Well other exotics have 8 or 12 cylinders and don't run as many litres as the 8.0 liter v-10. Secondly How many stock big block cars are built stock to go above 5500 RPM? The reason the smaler displacement engines can rev that high is less rotating mass first off, the crank in a viper compared to a flat 6 porsche is huge. Of course if you want to scream an engine 1500 RPM past the limiter daily it isn't going to last very long. The viper doesn't need to be howled out that high anyways, it makes peak power and torque well below the limiter. Going out of the power band is slower. If you want a car to scream it to 9,000 RPM get a honda S2000, they are a fun drive if you hate torque, you have to drive it like you hate it to make it fast.

As for HP/litre, that's just a ricer excuse for not being interested in domestics.

I'm sure somebody with more knowlege will add to it.

 

[Snakester]

HP/Liter is a justification to have a tiny engine with no torque.

A S2000 is a great example. It's a fun, zoomy car, but the Viper makes more torque just off idle than the S2000 does at peak!

And peaky, low torque engines will give you decent performance only when you drive them like you are trying to kill the car, revving the engine to 8500PRM and dropping the clutch.
Otherwise you are looking at 15 second 1/4 mile times. Oops.

A high-horsepower, high-torque, normally aspirated, big block engine is never really off of it's power, and can pull from any gear.

And because the engine is so understressed, it's not going to blow up at 20K miles when driven hard.

Plus peak HP and TQ are made before redline on the V10, so there is no point in over-revving the engine, just grab the next gear and the ample torque will pull you to amazing speeds.
Right on past all of the high-hp/liter technically "superior" cars.

Drive a Viper and then you will understand.

-Dean.

 

[Craig 201 MPH]

side note, my car makes more hp/litre than the viper, I'll trade it for your viper if ya want....

 

[EXECMALIBU]

I GOT THE 56HP PER LITER RATING FROM THE BACK OF A D/C VIPER INFO SHEET!

SINCE THE V-10 IS NORMALLY REFERRED TO AS A 8 LITER I THOUGHT THAT IT WAS CORRECT TO USE THE HP PER LITER DATA..

OK.. A 1967 426/427 CUBIC INCH DODGE OR GM/FORD V-8 MOTOR IS 61 CUBIC INCHES LESS THAN A 488 DODGE V-10... BUT THE V8 MAKES MORE HORSEPOWER PER CUBE! THOSE MOTORS WERE THE HI-PO STREET ENGINES OF THE DAY AND THEY WERE CARBURETED...WHY DOES THE 2001 488CI INJECTED V-10 MOTOR MAKE LESS HP PER CUBIC INCH THAN A 1960s MOTOR?? IT DOES NOT MAKE SENSE! THEY HAVE THE TECHNOLOGY..

IT WOULD BE A NO-BRAINER FOR THE D/C ENGINEERS TO BUILD A MONSTER 8 LITER V-10 THAT WOULD RUN ALL DAY AT 7,000 RPM AND PUT OUT OVER 750HP...

IN THEORY IF SOMEONE WERE TO DESIGN A 4 OR 5 VALVE HEAD AND REDESIGN THE CAM AND INDUCTION/EXHAUST SYSTEMS. THE MOTOR SHOULD EASILY PUT OUT 75HP PER LITER WHICH TRANSLATES TO 600HP!

IT HAS PROBABLY ALREADY BEEN DONE!

WE ALL KNOW THAT THE CHRYSLER ENGINEERS ARE AMAZING! THEY DESIGNED THE 426 HEMI!

30+ YEARS AGO THEY RACED THE BIG BLOCKS! HEMI 426 CI AND 427 GM/FORDS.. (OVER 7 LITERS) THEY WOULD RUN AND MAKE OVER 500+ HP WIDE OPEN AT 7,000+ RPM FOR 500 MILES! ALL OF THOSE BIG BLOCK MOTORS HAD HUGH CRANKS! THEY WOULD EVEN RUN AT 7,000 RPM FOR 24 HOURS STRAIGHT AT LEMANS WITH NO PROBLEMS..

WHAT ABOUT THE HUGH 1972 CAN-AM MOTORS (500CI AT 700HP =7.5 LITERS) THAT ALSO RAN 7,000-7,500 RPM..

THE 1966 450+HP 427 FORD CAMMER MOTORS WOULD ALSO RUN AT 7,500 RPM..

SINCE THE TECHNOLOGY AND METALURGY WAS THERE OVER 35 YEARS AGO TO HANDLE THE "ROTATING MASS" OF A 7+ LITER AT 7,000 RPM FOR A 24 HOUR RACE.


I AM VERY CONFIDENT THAT THE 8 LITER ENGINE IN A VIPER WAS OR DEFINATELY COULD HAVE BEEN DESIGNED TO HANDLE A MUCH HIGHER HP RATING THAN 56HP PER LITER..

PS..

THE REASON THE STOCK V-10 ENGINE MAKES PEAK HORSEPOWER AT 5,600 IS MAINLY BASED ON THE CAM TIMING ,INDUCTION,EXHAUST ECT.. THE V-10 RACE MOTORS EASILY MAKE MORE HP AT MUCH HIGH RPM USING THE SAME ROTATING MASS!

THE ORIGINAL GEN-II MOTOR WAS UP BY 50HP WITH A SMALL COMPRESSION BUMP.. THE NEW SRT V-10 MOTORS ARE UP BY ANOTHER 50HP TO OVER 500HP WITH MORE TORQUE..

 

[Craig 201 MPH]

My whole point is that they don't NEED to run that high RPM what's the point running that high to make less power? Those V-8's you mentioned were built to run at high RPM for extended periods of time, and were RACE engines. What street hemi's were fine to run to 7K?.They made peak power at 5K. I'll have to see what my dad says about me borrowing the hemi cuda and run it up to 7K.

Have fun revving the he_ll out of the Viper, I can't wait till you throw a rod and complain about it and blame the car.

It's not all about hp/litre, Would you rather have the 4.7litre V-8 making 102 hp/litre? in your Viper? I sure wouldn't.


Those V-8's of the 60's were nascar engines not what you could get in your charger or coronet, surely beefened up over a street hemi.

Furthermore. Lamborghini had ALOT to do with getting the V-10 to make the numbers it does. Read up on it. I'm sure they know what they're doing.

Lastly getting a 750 horse engine from the factory would be literally impossible for use in a street car, little issue of emissions and fuel efficiency. Gas would be costly (moreso)if you were running the V-10 to 7K on a regular basis.

<FONT size="7"><FONT COLOR="red">ALSO.. WHY IS IT SO HARD TO TURN YOUR CAPS LOCK OFF???</FONT c></FONT s>

 

[EXECMALIBU]

You are missing the point!

Other manufactures as you point out can build 102hp per liter engines that are fuel efficent and are enviromently friendly!

Just because you can rev to 7,000 RPM does not mean that you have to!

My 427 Cobra had a 427 sideoiler motor that was offered stock in a 1967 ford station wagon! It would rev to 7,000 RPM

Granted they were designed for Nascar but they were also sold for the street! I pushed the motor to the 7,000 redline on occassion with no problems!

Bad example!..Lamborgini only builds 4 valve 500hp 5.5 liter high revving motors! If Lambo was given a free hand I think we would have a MONSTER MOTOR!!!

If there was a limited Viper option for a 102HP per liter 750HP motor are you saying that you would not take it??

What I think you are saying is that D/C is afraid to offer a 750HP car to the public!

IF YOU READ MY ORIGINAL POSTING YOU WILL SEE THAT IT ASKS "WAS THE POWER INTENTIONALY LIMITED BY DODGE?"

 

[Craig 201 MPH]

well....

you can't honestly think a automotive corporation would put out a 750 horse motor in this car from the factory, enough people mess them up in stock form (ie people that bump the limiter in the wet) can you imagine it comming stock with 750 horses I can't. Sure there are tuners to do it. Just becasue it's possible doen't make it right or feasible for the manufacturer to do so. An engine that makes 750 horses as opposed to 450 horses is going to use more fuel which will pollute more, subsequently raising that manufacturers total emissions output (not sure what the tecnical name is) which forces even higher gas guzzler taxes etc... Why do you think the corvette still has a 5.7 litre. It's becasue their making all those gas hungry ghetto buses that bring that level up. If their largest SUV was durango size then maybe it would get the 427. GM has strict corporate policy about total emissions and I'm sure all other manufacturers do as well. I think 450 horses and a pathetic 56 hp/litre is a good place to start. I bet I can find at least 15,000 people to agree.

Craig

Intentionally limited? Read the history, the TARGET was for 400 HP back in 1989. Toyota could make a 600 horse corolla with a CART engine in it but they aren't going to. What's so hard to understand?

 

[Martin D]

The stock oiling system will not support more than 6200 rpm for any extended period of time. Further more, the intake is a limiting factor to breathing beyond those RPM's.
If you choose to correct those situations, you will sacrifice low end torque.

The car in it's current form, is just not intended to be reved beyond redline. Every action will have a reaction.

My heads and cam are about as radical as you can get. Can I make power above 6k? Yes. But not for long.

Regards,

 

[VEETENN]

Don't forget 1960's power ratings were Gross Rated, todays power ratings are Net Rated. Hp/liter of the 60's motors based on NET RATING of today would be much less.

 

[Bill Pemberton Woodhouse]

Brad said it all. Gross ratings and Net ratings are completely different. I don't have the formula, but I am sure some Engineer out there could help us and you can see some based on a more equal basis. Keep in mind also, that the debate here on an OHV that will go to 6200 ( very few got over 5,000 in the old days ) is that this really is a TORQUE motor. The biggest reason no one can understand why Vipers are so fast is our mentality is based completely on horsepower and we don't relate or talk about torque. 500 ft lbs of torque with smooth tubes and K&Ns is another chapter, and probably well worth reading. I am thoroughly amazed at the HP/Torque ratings considering all the pollution requirements, unleaded fuel , etc. compared to the beasts of old.
Technology has gotten us there, and even carrying all this baggage.

Just my 4 cents. Well this is so **** long, I figured 2 cents wasn't enough, ha.

 

[EXECMALIBU]

Craig,

I totally that agree that 400 hp was a great place to start!

But I guess the D/C engineers felt that 450HP was a better place because they increased the HP and the Torque..With the same Advertised milage figures

Now they must feel that 500HP is an even better place to start so they are offering the SRT with 500HP and even more Torque! In a much lighter car!

I seriously doubt that that any new SRT owners are going to be upset because their cars have an extra 50HP!

"Excuse me.. Mr.Service Advisor.. I have a complaint.. My new SRT is a little to fast!.. Can you please do something to fix it???"

I also wonder if you asked the same 15,000 people if they would like more than 450HP and more torque how many would refuse it!!

Maybe you can explain why virtually every viper owner instantly adds the smooth tubes and K&Ns at a minumum??

It could NEVER be because they want the extra power!! only 15HP..

The amazing thing about todays engine technology is the fact that they can add HORSEPOWER and TORQUE while actually reducing emissions and fuel consumption at the same time!!

Some of todays Hi-Po cars put out over 35% more power with lower fuel consumption and emissions than they had just 5 years ago!!!

Simply by adding another bump in Compression would add HP and Torque.

I guess you are from the same group of people that decieded a handgun with 12 bullets is much more dangerous than a one with 10 bullets! So they passed a law! We are all much safer!! Now if you drop a handgun on your foot you wont get bruised!..

Offer the cars with differant levels of HP and let the public deciede! Build one with as much HP as it can handle and still be reliable.

Hell they sell those 200MPH super bikes to any kid that walks in with the $$$$...

I AM JUST ONE OF THOSE GUYS THAT THINKS THERE CAN NEVER BE TO MUCH HP!!

PLEASE DONT TRY AND PROTECT ME FROM MYSELF!

I KNOW THAT I AM NOT ALONE!!!

 

[Craig 201 MPH]

I'm not trying to protect you from yourself, I'm simply saying that you're never gonna see a 750 horse viper from the factory that's what tuners are for. If you want that, go get it from them, they provide warranties. I agree with the loving horsepower and you can't get enough of it, but from a corporate standpoint I just don't see it happening. Sure they COULD make it happen but they won't. Who knows, is it becasue of liability? or whatever else? So you are proposing different levels of power. So is it safe to assume you'd pay more $$ for more power? If so, what are we arguing about then? Call a tuner and be done with it.

Craig

 

[Tom F&L GoR]

If we really get technical, here's a little info from a paper written by Masatoshi Akagi, Honda R&D Co., Ltd entitled "JAMA Activity for 4-Stroke Engine Oil for Motorcycles - Introduction of Today's Technical Consideration in Japan." It shows the horsepower (actually Pferdestarke) per liter over various engines, including motorcycles.

You must be registered for see images

It would indicate that moving (roughly) from 5500 to 6500 RPM should add another 100 HP to an 8L engine. How about a little discussion on how to do this ... anyway?

My interest is that I always get stuck on the bigger throttle body and manifold driveability question. Since they both only flow dry air, there shouldn't be any risk of fuel dropping out, or not vaporizing, or causing problems, since the fuel is injected at each valve head. The distribution and volatility problems inherent with carbureted engine manifolds are gone. The air flow speed through the carburetor greatly determined fuel mixture and quality thereof; the injectors take care of all this for you now. I can see how a larger TB opens less to flow the same air, and therefore the TPS signal is incorrect, but that is an electronics issue and not a flow issue. In fact, the new BMW 740 has no TB at all, it has an infinitely variable valve lift system.

Reading this board: flow numbers for the TBs seem adequate for another 100 HP, the intake manifold seems to be restrictive, the heads seem OK, the oil system isn't designed for higher RPM, and the ECU has a 6200 RPM limit. Tuners, does it seem reasonable to address the manifold, oil, and ECU issues to get 1000 RPM and 100 HP?

Headwork and manifolds to get more power in the same engine speed range is hard (or expensive) since at low engine speeds the volumetric efficiency isn't as bad as at high speed, so there's not as much to gain at low speeds compared to higher.

OK, I'm done with my little brainsprinkling.

 

[EXECMALIBU]

I GUESS WE ARE ARGUING ABOUT HOW DARK THE COLOR BLACK IS...

I RECENTLY SPOKE WITH ONE OF THE ADD EXECUTIVES FOR D/C AND WAS TOLD THAT BECAUSE DAIMLER BENZ IS UNIMPRESSED WITH THE PROFITS GENERATED BY CHRYSLER THEY MAY ENTERTAIN SOME RADICAL PR MOVES..

ONE OF THE MOVES DISCUSSED WAS THAT D/C MAY UP THE ANTE ON THE VIPER.. AND GO AFTER THE OLD COBRA TAG LINE " THE WORLDS FASTEST PRODUCTION CAR"

THEY MAY ALSO SUPPORT A LARGER FULL RACE TEAM LIKE CADILLAC..

THESE ARE JUST A FEW OF THE OPTIONS AND THE PUBLIC MAY NEVER GET A 600-750HP VIPER.. BUT IN THE EIGHTIES NO ONE WOULD HAVE BELIEVED THERE COULD EVER BE A 400HP 2 SEAT ROADSTER FROM DODGE.. NOW DID THEY??

LETS HOPE!!...

 

[C O D Y]

I wouldn't be surprised if the SRT/10 will be close to that title "THE WORLDS FASTEST PRODUCTION CAR" right away.

I would think with todays better tires and brakes that the record of 0-100-0 will be ready to be broke real soon.

 

[C O D Y]

And please turn the CAPS OFF!

Thank you.

 

[John ACR]

Jeff,
Good luck with your new toy.
I can answer one question the rev limiter I believe kicks in at 6200 rpm.

 

[MES]

I haven't had time to read this entire post yet but a simple answer to your question as to why only 56 HP/L is because that's all the the HP they needed make. Could they have made 500HP, 550HP, or 600HP out of the V-10? Sure they could have, but with the Viper as the FASTEST AMERICAN PRODUCTION CAR EVER MADE (excluding pie in the sky L88 claims) why make it any faster? This is typical of US Automakers. Make it just good enough where the consumer will buy it, then don't do any improvements unless you have competition. It's the American way

 

[joe117]

Remember the 60's fuel would let you run 11.5:1 compression. I think that there is more than a little evedence that Dodge wanted to make a splash but was trying to save a few bucks here and there with the original Viper. The large, conservative, high power V-10 was probably all they could spring for at the time. Multi valves, dual cams etc would have put the project over budget. Remember, they even saved money on door handles. You think they didn't see it that way?

 

[jamie furman]

Just because a car pulls past redline doesn't mean its making more horse, probably is making less you just think it is because its making noise. They don't put those redlines in 1500 rpms early, they are there for a reason and that reason is to keep the motor together.And I have 2 hemicuda's and one hemi road runner and they are done at 6000 even though the redline is 6500.Don't want to be cocky but the guy who shifts his viper at 6200 is the guy I put on the trailor first.In almost all cases with stock motors when they reach redline they are past the point of making horsepower and if you don't beleive me take anyone to the dyno and find out for yourself.And as far as the old motors making more horsepower per litre, in dream land only, hemi's made about 325 on the rear wheels stock and vipers make about 410 do the math.I also have a csx cobra with a 427 sideoiler in it, it also is done at 6250 on the dyno even though it can rev to 7000 and it just dynoed 555 last week and 536 torque.I guess my real point here is what makes you think because a motor can rev higher it makes more horse?

 

[EXECMALIBU]

Since on numerous occassions I have been highly paid for my driving ability I feel that I may have some experiance to rely on...

Like I mentioned in my original posting..

For example..When I am racing in my 73 Porsche 911S I typically ignor the redline because the car is still pulling very hard!! I can feel when it is falling off power and shift..

It may be slightly past the peak HP but when I shift but I am in a higher RPM range in the next gear. I can continue to accelerate much faster then if I shift earlier.

In addition since I usually win races against cars with bigger motors I must be doing something right!!

 

[GR8_ASP]

Jason pretty much hit the nail on the head regarding the principle limiting factor for engine speed. This is a very simplified explanation from the limited engine experience that I have.

Valvetrain can be a limiting factor but camshaft design, valvetrain stiffness increases, valvetrain inertia decreases, etc can increase the valvetrain speed envelope within reason. Push rod type valvetrains can be made capable of in excess of 9500 rpm with geometries similar to the Viper. Cost is the primary limiting factor as most of the improvements come from costly material usage. A good example would be Nascar, who have managed that capability even with flat tappets. And I seldom if ever reference Nascar from a technical standpoint.

Piston speed is the foremost factor in limiting engine speed.
The The greater the stroke the lower the speed capability. For production engines that require long term durability the reciprocating mass effect due to stroke is very important. Note that the forces at work in this regard are based on the square of the speed, and thus the square of the stroke. In the the graph above for hp/L versus rpm if the hp/L information is normalized for stroke squared you get an almost flat line. That is to say the BMEP (the pressure on the piston to create the work) differential between performance engines is not dramatically different. The primary difference is at what engine speed does the peak occur. In general the higher the engine speed when peak BMEP occurs the higher the horsepower per L ratio. Tuning plays a part in this and that is why I stated "in general."

Another aspect is knock limitation. The larger the bore (combustion chamber) the longer it takes for the flame to propogate across. The more time for pressure and temperature increases to cause detonation or preignition. That factor allows smaller bore engines to operate with higher compression ratios and peak cylinder pressures with the same fuel quality.

The combination of the bore effect and stroke effect make the ability to make high hp/L easier with decreasing displacement per cylinder. Note in all of these arguments it is based on liters per cylinder. More cylinders does not directly reduce engine speed capability.

Hope this hasn't bored you all to tears.

But when it all comes down to it I prefer a wide torque band over a peaky high horspeower engine as it is available throughout the useful range and available anytime. I know that may not maximize performance but it does maximize performance feel. A formula 1 engine in a Viper would feel like a dog in normal driving as its low end torque is pretty low. It would be very difficult to launch without either spinning the tires excessively or stalling the engine. Can you imaging a 6000 rpm launch and slipping the clutch until maybe 20 or 30 mph to prevent stalling.

Okay, let the fireworks begin.

Ron

 

[GR8_ASP]

Execmalibu,

Depending on the overall shape of the torque curve you may indeed benefit from going past redline. Especially on boosted engines where horsepower peaks occur very near redline.

However, your experience seems to be with older engines that do not have engine speed limiters with valve float as the primary speed limiter. Modern engines all use engine speed limiters and cut off either fuel or fuel and spark at a specified engine speed. Without modifying the calibration you are stuck. Also, engines like the Viper that have the torque dropping off rapidly at high engine speed offer reduced performance by increasing engine speed well past the HP peak. You may feel like the higher engine speed shift was better, but in fact it is not. It is the stored energy in the rotating inertia (crank, flywheel, etc) that give you that seat of the pants feel. But time yourself and you will see that a high speed shift point in a Viper will slow it down.

 

[Craig 201 MPH]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by StormBringer:
As a owner of a S2000 I don't take kindly to people saying you must drive the car like you hate it, yes you have to drop the clutch above 7000 to get into the 13's but hey thats not what the car is built for. Take a average joe driver and but him in both the viper and the S2000. He will be much faster on a track in the viper no question. Take a very well deleloped driver and place him in both it gets closer. We have this fight on the S2000 boards all the time, we get the civic owners who have upgraded and expect the S2000 to be a drag car, they should have bought a domestic even I will admit that.

The other problem is at 120hp per liter there is not much tuning that you can do. We have thrown full exhaust intake header throttlebody systems at our cars with little to no success. FI is really the only way to get any more power.

S2000's go very very fast you just have to think ahead to get there, its not like a viper where you can simply push your right foot down.

<HR></BLOCKQUOTE>

Sorry, I wasn't bashing the S2K, I love em and I think they're a cool car. I've driven one and it's a 4 wheel motorcycle, a heck of a ride.
Craig

 

[lleone]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Jason Ward:
Here is a fact that I don't think most people know, at 5250 RPM all engines(2cycle, 4 cyl, V6, v8, you name it) have a HP reading higher than the torque reading. Don't believe it, check your dyno sheets, and see where torque and HP cross.

What this means is that the ability to accelate at peak(remember torque is accelation) declines here .
<HR></BLOCKQUOTE>

Hmmm, correct me if I'm wrong, but horsepower is a function of
torque at a rotational velocity (rpm). The definition is
horsepower = (torque*rpm)/5250, which means that at 5250 rpm horsepower MUST be equal to torque. If I've got the equation right, you'd better find a better dyno because if horsepower and torque differ at 5250, somebody's lying to you.

 

[GR8_ASP]

Horsepower and torque are mathematically related. Torque is the work that the engine is making and horsepower is the rate at which it applies the work. If you have any two of: torque, rpm or horsepower you can calculate the other. In US units the curves cross at 5252 rpm because the formula is 550 ft lb/sec = 33000 ft lb/min = 1 hp. And 33000 / (2xPi) = 5252.

The numbers only match in US units at that speed.

Peak vehicle acceleration in any specific gear will occur at peak wheel torque (neglecting drag). For any given gear that is at the engines peak torque point. For the Viper that is well below 5252 rpm. To maximize overall acceleration if you plotted the torque x gear ratio versus vehicle speed for each gear, the optimum gear change speed would occur at each curves intersection with the adjacent curve. Lots of analytical work to be sure and the shape of the torque curve is critical in finding the correct answer. Because the torque in the Viper drops off quite dramatically past the peak power point, missing a shift on the high side is much more damaging to overall acceleration than missing it on the low side (ie short shifting). That means for most of us it is better to err on the side of short shifting.

Ron

 

[VEETENN]

Dr. Speed, lots of great information Thanks. Regarding bore effect isn't this one of the main reasons newer engine designs are using twin spark plugs per cylinder? I believe the new Dodge Hemi will have twin plugs.

 

[GR8_ASP]

Yes twin plugs does improve flame propogation by decreasing the required propogation distance. But, unfortunately, it does not reduce it dramatically. But every little bit helps. Every degree of spark or compression ratio point that can be added helps performance, and in most cases fuel economy. But in my case fuel economy at WOT is low on the importance scale.

 

[Snakester]

While I certainly understand the need to crave more HP, it's pretty amusing that someone would find the Viper's power wanting.
First off, many of the factory Vipers are underrated, with 475HP not being uncommon stock.

But the two points that I think are most important are the fact that the Viper has more stock power than 99% of the new cars sold in the U.S., and that the car's performance is equal to, or better than any street legal stock car under $100K, and faster than many other cars that cost twice as much, and have all of the high technology multi-valve, high revving $$$ engines, that cost $4000 for a tune-up.

Comparing to 60's cars is not really relevent because they did not have to deal with emmissions restrictions.

With the Viper you can always add intake and exhaust upgrades, and if you really want excess power N20, or turbo/supercharging to get crazy power output, with reasonable reliability.

This is not a good option for high HP/liter, high revving cars like the S2000, or Ferrari 360 as they could not take more power adders and not quickly gernade the engine.

Sometimes getting the performance results simply is a better solution than pursuing complex and expensive technology, especially if you want to drive the car quickly more than 30 minutes at a time.

-Dean.