Gen 3 Roe Blower ready by VOI 10

[BlueGTS]

A displacement supercharger like the Roe tends to increase the torque substantially more at lower rpm than a supercharger like the Paxton. That torque for the same peak power will probably be in the 10-20% range. That stresses the driveline that much more. Period! Plus, since it is available during normal driving, there is a tendency to apply that torque more often. Anyone who thinks, even for a minute, that additional torque does not decrease the life of the drivetrain just plain does not understand physics. I do not care about an example here or there. Physics is physics. There is a reason the SRT changed the transmission, clutch and differential for 2008. That reason is TORQUE. Torque is the force that fatigues shafts, bearings and the like. Horsepower increases the frequency of the loading, thus also reducing the life. But if you ever looked at an S/N curve you will note that frequency and stress do not have equivalent impact on fatigue life spans.

No one that I saw mentioned stress on the engine. But if it continues to be a non-interecooled supercharger it can indeed induce more thermal stress. But the simple fact is that torque is made by the force on the piston, pushing the connecting rod through the crankshaft journal. That MUST increase the loading on each component in the system. What is okay with a Gen 2 forged connecting rod engine may not be okay with a powder metal 2005+ rod.

Ron,
The first post in this thread, CONs list: 3. More stress on engine

That is what I was talking too. You typed a lot about driveline stress but I did not see where anyone mentioned that. When people talk about stess on an engine I think of valve train etc. I still believe that not having to go to redline to get your HP will reduce engine stress. I doubt many Viper engines have been blown at lower RPMs. With my ROE I can shift anywhere around 5k and it feels very similar. I know the Paxton is great and is capable of making much more power than the Roe. However, I believe it also requires redline pulls which is where the stress on the engine is the greatest.

 

[Sean Roe]

No incorrect.
The adiabatic efficiency of the 2.4L shown in this graph is over 90%. It's the scale on the left.
I put that up for the general info. I'm actually using a 2.8L compressor. The 2.4 was too small and one of the biggest reasons I never released the kit. Wait until later tonight and I'll put up more info. I just had to stop and look to see if any other engineering types looked at the graph.

I'll make one comment about stress on the engine for now, the Viper motor is not built to handle upper RPM's. When has anyone heard of a Viper engine failing at WOT and 4,000 RPM? I never have. Anything I ever hear of is over 5,000 RPM, but more on that later tonight.

Regards,
Sean

 

[Bobpantax]

Regardless of the actual answer, the Paxton kit comes with a three year limited warranty and an optional three year drivetrain warranty. Will the GenIII Roe system come with an equivalent warranty with an equivalent optional warranty? To me, the proof is in the warranty. The rest is an interesting engineering debate. Please advise.

 

[BlueGTS]

Regardless of the actual answer, the Paxton kit comes with a three year limited warranty and an optional three year drivetrain warranty. Will the GenIII Roe system come with an equivalent warranty with an equivalent optional warranty? To me, the proof is in the warranty. The rest is an interesting engineering debate. Please advise.

There are a lot of good things to debate with the twin screw versus centrifugal but I do not think reliability is a problem that the Roe blower has. You have to remember that Roe is a smaller operation than Paxton so his warranty might reflect that. Are you saying that you believe the Paxton blower is more reliable than the Roe due to the warranty?


Chris Farley in Tommy Boy:
Because they know all they sold ya was a guaranteed piece of ****. That's all it is, isn't it? Hey, if you want me to take a dump in a box and mark it guaranteed, I will. I got spare time. But for now, for your customer's sake, for your daughter's sake, ya might wanna think about buying a quality product from me.
Just a funny quote from Tommy Boy.

 

[Bobpantax]

There are a lot of good things to debate with the twin screw versus centrifugal but I do not think reliability is a problem that the Roe blower has. You have to remember that Roe is a smaller operation than Paxton so his warranty might reflect that. Are you saying that you believe the Paxton blower is more reliable than the Roe due to the warranty?

No. I am saying engineering discussion aside, assuming that they are both good, I prefer the one with the better warranty. And, since you mentioned it, issued from the company with the deeper pocket. But visually, nothing beats the Roe - at least on the Gen II. I got more "Wow - that's insane!" remarks with my Roe. My point may be partially moot. Perhaps Sean plans on issuing a three year limited warranty on the Gen III system.

 

[99 R/T 10]

No incorrect.
The adiabatic efficiency of the 2.4L shown in this graph is over 90%. It's the scale on the left.
I put that up for the general info. I'm actually using a 2.8L compressor. The 2.4 was too small and one of the biggest reasons I never released the kit. Wait until later tonight and I'll put up more info. I just had to stop and look to see if any other engineering types looked at the graph.

Sean,
Can you clarify: the GenI/II S/Cs are 2.8s and not 2.4?

 

[black mamba1]

Sean, I yanked the graph below off your Roe website. It shows about a 152 hp increase at 6.5 lbs of boost. Is this what we should still expect to see or have you modded your system since this graph was produced? Also, I hear there are two versions, one required a different hood. Does the version of your super charger requiring the new hood produce more power? If so, how much more?

You must be registered for see images

 

[Bobpantax]

Hi MB1. You are already at 528/557. Are the projected results above 587/604 on a stock SRT10? If not, what are the mods? If stock, what would the projected results be with your mods? Also, would the proposed Gen III kit work well with your mods? I seem to recall Dimitrios having a terrible time with his mods and a Roe on his Gen II. You might want to discuss this point with Sean and Chuck.

 

[black mamba1]

Hi MB1. You are already at 528/557. Are the projected results above 587/604 on a stock SRT10? If not, what are the mods? If stock, what would the projected results be with your mods? Also, would the proposed Gen III kit work well with your mods? I seem to recall Dimitrios having a terrible time with his mods and a Roe on his Gen II. You might want to discuss this point with Sean and Chuck.

My engine was actually built up by Chuck in anticipation for the new Gen 3 Roe. Chuck had Sean's input on the build up. I dont know what my end numbers would be w/ the Roe, b/c my engine was built for high boost. I imagine I would be close to 750 or so rwhp max on a Roe, around 800 rwhp or so for Paxton. I can go higher, but I dont think that makes any sense.

I dont know how I feel about that kind of power at low rpm. I know you prefer your Paxton set up b/c the power seems more controllable, amonst other reasons. I agree w/ everyone that says that SRT's biggest problem is traction, no need to make that much worse.

However, the novelty of having one of the few SRT's w/ a Roe is very attractive!

 

[BlueGTS]

I seem to recall Dimitrios having a terrible time with his mods and a Roe on his Gen II.

I believe Dimitrios had the stock fuel pump and lines in his car. If he can confirm this I think it was more of a fuel problem versus a blower problem.

 

[Red Snake]

I dont know how I feel about that kind of power at low rpm. I know you prefer your Paxton set up b/c the power seems more controllable, amonst other reasons. I agree w/ everyone that says that SRT's biggest problem is traction, no need to make that much worse.

However, the novelty of having one of the few SRT's w/ a Roe is very attractive!

The Roe power is NOT a problem at lower rpms. That's actually what makes it so much fun to drive. Hooking up is not that hard if you have any driving skills.

 

[plumcrazy]

yeah D had the stock system and BAP in his gen2. that had to be part of that problem.

 

[GR8_ASP]

No incorrect.
The adiabatic efficiency of the 2.4L shown in this graph is over 90%. It's the scale on the left.
I put that up for the general info. I'm actually using a 2.8L compressor. The 2.4 was too small and one of the biggest reasons I never released the kit. Wait until later tonight and I'll put up more info. I just had to stop and look to see if any other engineering types looked at the graph.

I'll make one comment about stress on the engine for now, the Viper motor is not built to handle upper RPM's. When has anyone heard of a Viper engine failing at WOT and 4,000 RPM? I never have. Anything I ever hear of is over 5,000 RPM, but more on that later tonight.

Regards,
Sean

Sorry Sean but you are incorrect. I was talking about adiabatic efficiency (the thermal efficiency of converting rotating energy into pressure energy) . The red line. Not volumetric efficiency. Volumetric efficiency is where centrifugal chargers really fail, thus the resulting non linearity of the flow curve. 78-80% adiabatic efficiency is generally regarded as the peak efficiency of the twin screw charger. 90% would get you a Nobel prize. Yours is showing a peak of about 65% which seems a bit low. Maybe the test pressure is outside of the optimal characteristics for that particiluar device. I would prefer to see a 3-dimensional map of efficiency versus flow and pressure and determine the correct size based on the best thermal efficiency. Especially if an intercooler is not included and the inefficiency results in increased inlet temperatures.

I could tell it was not a workable solution - too little flow for the consuming engine. It would probably work well for a 7 liter though.

As far as the stress and engine life. Please do not mix up combustion, valvetrain dynamics and stress. Stress is the translation of force into mechanical elements. The factors that cause things to fatigue. RPM only increases the frequency for the compression side of it. RPM does increse the inertial side of the equation (tensile direction), which does indeed increse the component stress as it is the delta from max to min that causes fatigue (note the S in an S-N curve is not the peak stress but the stress range from minimum to maximum). And in this case the minimum would be a negative value when, say for example, the rod is in tension, and positive when in compression. And yes, the tension forces may exceed the compression forces. That is why missed shifts resulting in very high revs fail the conn rods. In tension if you analyze the fracture.

As far as the rest of the driveline the primary component of fatigue failure is indeed torque. Added rpm, or horsepower, is a significant factor for differential bearing failure but not much else. Compare a 200 hp Honda with a 200 hp anything else and you will see the difference. Torque is the twisting force that the mechanical bits must handle. I will avoid the reflected inertia side of the equation which also leads to driveline failure as it does not pertain much to this audience.

I will leave the valvetrain comment aside. I studied valvetrains in college and had valvetrain engineering responsiblity for about a decade. Including several published documents on the topic of valvetrain dynamics. We could have a very interesting conversation if you wish to go that direction.

 

[ViperTony]

Keith...I think that based on the way you drive the Roe kit seems to make the most sense for you. I know first-hand how you like those roll-ons and stop light starts . If you install the Roe kit and decide you don't want it I'm certain someone here will gladly take it off your hands. Not to mention that Sean will be with you every step of the way. Go for it.

 

[GR8_ASP]

BlackMamba1 the power curves you show are almost a perfect match for my Paxton equipped SRT. 590-620 lb-ft from 3500 to 6000 rpm. Hmm My performance curves are shown in my media gallery.

Here is the torque graph of a dyno day last year. Guess which one is the Paxton and which os the Roe? Note the Roe in this case is a Gen I so the power curve is low rpm biased even more. In this case almost the same maximum torque but far differing hp. Same day, same dyno, same dyno operator.

 

[ViperTony]

The Roe power is NOT a problem at lower rpms. That's actually what makes it so much fun to drive. Hooking up is not that hard if you have any driving skills.

Trust me...Mamba has skills which is why I believe the Roe will suit him very well especially with his NA buildup with the Roe in mind. Keith is not one for being king of the dyno numbers but rather likes to drive in the real world.

 

[black mamba1]

Hey Gr8,

Nice graphs. The comparisons give some credence to the Roe argument I think. Overall, your car has 683 rwhp, and the Roe has 587 rwhp. But the two are VERY closely matched all the way up to 5000 rpm when your car really takes off and makes another 100 rwhp. So, although your car is rated at 683, the Roe car is right there with you until 5000 rpm. So, what happens in that last 1,000 rpm? The Roe has to shift while you are still pulling and you will really walk the crap out of him then I think. If you are coming from the dig, that would be when you make up the jump the Roe will get from his advantage in power and torque from the dig up to say 3700 rpm?? This would be a very close race in the 1/4 mile and all the way to 140 mph.

So, what do Roe guys do in the last 1000 rpm when they have nothing left? If they are shifting to the next gear while the Paxton is at peak power in a lower gear it seems as if the Paxton would shine and have the advantage. Or does it? I can say this, it does seem to take the Paxton another 100 rwhp to offset the Roe power curve.

 

[black mamba1]

Trust me...Mamba has skills which is why I believe the Roe will suit him very well especially with his NA buildup with the Roe in mind. Keith is not one for being king of the dyno numbers but rather likes to drive in the real world.

Thanks Tony! Hey, when are you gonna be up so we can terrorize these Vettes and Ferrari's and Porsches around here?? These graphs does make the Roe system look very attractive!

I just want to be able to compare both overall systems. From water/****, to tuning, to warranty to actual availability before I decide.

 

[black mamba1]

Keith...I think that based on the way you drive the Roe kit seems to make the most sense for you. I know first-hand how you like those roll-ons and stop light starts . If you install the Roe kit and decide you don't want it I'm certain someone here will gladly take it off your hands. Not to mention that Sean will be with you every step of the way. Go for it.

It would be neat! Hey, you considering a Roe too?

 

[RTTTTed]

When I wear this Gen 2 Viper out ... I may think about replacing it with a Gen 3 as long as it comes with a Roe blower and PS2s.

Ted

 

[GR8_ASP]

Hey Gr8,

Nice graphs. The comparisons give some credence to the Roe arument I think. Overall, your car has 683 rwhp, and the Roe has 587 rwhp. But the two are VERY closely matched all the way up to 5000 rpm when your car really takes off and makes another 100 rwhp. So, although your car is rated at 683, the Roe car is right there with you until 5000 rpm. So, what happens in that last 1,000 rpm? The Roe has to shift while you are still pulling and you will really walk the crap out of him then I think. If you are coming from the dig, that would be when you make up the jump the Roe will get from his advantage in power and torque from the dig up to say 3700 rpm?? This would be a very close race in the 1/4 mile and all the way to 140 mph.

So, what do Roe guys do in the last 1000 rpm when they have nothing left? If they are shifting to the next gear while the Paxton is at peak power in a lower gear it seems as if the Paxton would shine and have the advantage. Or does it? I can say this, it does seem to take the Paxton another 100 rwhp to offset the Roe power curve.

MB1 you will find out that tire spin will occur from the "dig" assuming that neither car is dumb enough to start in a high gear. Choose optimum gears and it should be no contest. Note also the power curves you posted are well in excess of those seen for the base Gen II Roe system. Looks like he has turned up the wick. I just hope he is keeping the inlet temps reasonable.

 

[ViperTony]

It would be neat! Hey, you considering a Roe too?

Yes...and I need you to get one so I can convince central planning that I need one.

 

[Nine Ball]

I just thought I'd mention that I'm also a mechanical engineer, but I feel no need to bench race or try and prove how intelligent I am. Bench racing *****, thanks! I'll eagerly wait for real world results instead.

Tony

 

[Steve 00RT/10]

The Roe power is NOT a problem at lower rpms. That's actually what makes it so much fun to drive. Hooking up is not that hard if you have any driving skills.

I completely agree -- minimal traction issues from a roll if using your right foot properly. PS2s made a big difference. When xcrossing, I routinely start in 2nd gear with a little tire spin for the folks

When I wear this Gen 2 Viper out ... I may think about replacing it with a Gen 3 as long as it comes with a Roe blower and PS2s.

Ted

Might take a long time to wear out.....we may not need another one. I may as well have had a 3yr/30K warranty because we'll easily get that in by season end.

MB1 you will find out that tire spin will occur from the "dig" assuming that neither car is dumb enough to start in a high gear. Choose optimum gears and it should be no contest. Note also the power curves you posted are well in excess of those seen for the base Gen II Roe system. Looks like he has turned up the wick. I just hope he is keeping the inlet temps reasonable.

Ron, it's too bad we've never had a good time, place, or the same gearing to do a little roll from say 20-125. I could be wrong, but I'm thinking there wouldn't be a whole lot of difference given your extra 100HP. There would be even less difference if you were running stock tires........2.92 ratio against my 3.45s. There is a considerable difference in 'quick' between each of our 2 cars. ...one with each of these ratios

Steve

 

[1TONY1]

Forget about it. Jm heads and cam with a DC tune and forget about it. Adding all the x-tra weight to the nose is ok for drag racers but a handling penalty on road courses and the street where you go around corners and use the brakes. GTS Bruce

Road course + street = autocross ??

A Roe car will DRAG an n/a car around the autocross even with the extra weight.

 

[Bobpantax]

I just thought I'd mention that I'm also a mechanical engineer, but I feel no need to bench race or try and prove how intelligent I am. Bench racing *****, thanks! I'll eagerly wait for real world results instead.
Tony

I thought that GR8 ASP's comments were very interesting and useful. I like the fact that he is debating with Sean. We need more debates with tuners. Too many claims are accepted on this site without any detailed questions being asked and/or answered. And, if I am not mistaken, GR8 ASP is more than a mechanical engineer. He is a mechanical engineer who specializes in drivetrains. In other words, a real expert on the subject being discussed. Also, as I understand the posts, a significant part of the discussion is which type of system places more stress on the stock components of the engine. This issue has nothing to do with race results. I hope that Sean posts a detailed response this evening as promised so that GR8 ASP can analyze it and provide us with his feedback.

 

[99 R/T 10]

Does anybody know for sure if there will be a 1/4 mile event at VOI?




I want to school all these fast Paxton cars in my stock block Roe

 

[black mamba1]

I just thought I'd mention that I'm also a mechanical engineer, but I feel no need to bench race or try and prove how intelligent I am. Bench racing *****, thanks! I'll eagerly wait for real world results instead.

Tony

Hey, I am the third guy in here to reveal my Mechanical Engineering status. Like Bobpantax said, I too enjoy Gr8's very technical discussions. I will be honest, even w/ my M.E. degree, his discussions are challenging to follow, but they are precise and accurate. Which is what we can all use. These are 100k exotic cars we are modifying to great extent and the extra engineering is greatly appreciated, especially since the SRT engineers would never discuss these things with any of us in this forum.

 

[black mamba1]

Does anybody know for sure if there will be a 1/4 mile event at VOI?




I want to school all these fast Paxton cars in my stock block Roe

If not I want my friggin money back! If the Roe is available by then for the GEn 3, lets just say VOI 10 just got a whole lot more interesting!

 

[black mamba1]

MB1 you will find out that tire spin will occur from the "dig" assuming that neither car is dumb enough to start in a high gear. Choose optimum gears and it should be no contest. Note also the power curves you posted are well in excess of those seen for the base Gen II Roe system. Looks like he has turned up the wick. I just hope he is keeping the inlet temps reasonable.

I believe Sean went with a larger super charger system for the Gen 3's than on the 1's and 2's, that might explain the higher power curve. Tire spin is definitely an issue, one I am very concerned about.