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

[jamie furman]

EXEC not trying to give you a hard time but you probably do have to rev those tiny motors so when you shift you have enough rpms because the torque isn't there, and we were talking about street cars not race cars.But there are a few well paid viper drivers as well who won daytona and lemans 24hrs with these lower reving engines and I am sure they were not overeving them.I don't claim to be a high paid racing driver but I do have some race experience as a matter of fact there was a time in the late 80's and early 90's that I got paid about 500 dollars a second when I won a race, the only problem with it was I occasionally lost and they made me pay them back.

 

[WCKDVPR]

There are two generally accepted conventions for optimizing shift points; 1) maintaining the same horsepower before and after the shift, and 2)maximizing the area under the horsepower curve.

Dyno your car and plug your numbers into this handy calculator and I think you will find the results very interesting - especially if your car has any engine/exhaust performance modifications.

Calculator link: http://www.bgsoflex.com/shifter.html

I do not have access to a dyno sheet from a stock car (my car has a few mods) but I think it would be helpful if someone could run the calculator with numbers from a stock setup and post them.

I hope this helps.

 

[Dan Vargus]

The Viper engine will live longer if you shift the car at 5200 rpm. Accelleration is a product of max torq. The viper engines can generate what ever hp You want. BUT let us not forget the cost of insurance of super exotic high hp cars. More hp more premium. DC had it right by limiting the hp to what would sell and satisfy the insurance people.
Dan Vargus / Blue-White RT/10...............

 

[onerareviper]

I'm no engineer, but I think there is diminishing returns with cubic inches. For example, F1 car with around 1.7 liter make 900HP+. Around 1 Liter Hayabusa motor makes 170 (I think). 2 Liter S2000 Honda makes 240HP. Let me do the math:

*If F1 was 8 liters, would it make 4235 HP?
*If Hayabusa was 8 liters, would it make 1360 HP?
*If S2000 was 8 liters, would it make 960 HP?

I guess my point is this: If you could magically scale up a S2000 motor times 4, making it 8 Liters, I don't think it would produce 960 HP. But I may be wrong. Engineers, where are you?

Later

 

[Mike Brunton]

Ding ding... we have a winner.. lilredz07 hit the nail on the head.

torque is a force, HP is work done. You can make all the torque in the world, but if the car isn't moving, no HP is being made. As soon as the car is moving, it's the HP that matters. By definition of HP, if you maximize it, you're pretty much maximizing the torque *at the wheels*.

As for revving the Viper engine - Jamie Furman said it right - go ahead and raise your rev limiter to 6500... the guys who know how these engines work and are shifting closer to 5,800 will be passing you.

As for the cars of the old days, you're dreaming if you think they made more HP/liter... they were GROSS rated which is about 35% higher than net. A gross rated Viper would be closer to 650hp. Show me an 8L car from back then rated at 650hp??? The 427 Vette was a nice car, but even the 435hp edition is way, waay, waaaay behind a Viper in any sort of acceleration test.

Sorry, but them's the facts. If you used to get paid a lot of $$'s to drive cars, just think how much more $$'s you could have gotten paid if you knew how to make them go even faster by maximizing the power you're putting down! Lost opportunity....

 

[Mr Hemi Head]

How about warranty costs!The owners manual for my 69 Hemi Charger states... the Hemi Engine was designed for Maximum Acceleration Trials ,the 5yr 50K mi warranty does not apply.The driveline warranty is 1yr 12K miles" How many Vipers would be sold with this exclusion??
Rick 2001GTS

 

[WCKDVPR]

I tried to keep it simple but that didn't work so here is the math:

Horsepower is a measurement of Power.

Power (P) is the time rate at which work is done.

Starting with the definition of work -

Increment of Work (dW) = Force (F) * change in distance (dx)

If the car moves a given distance in a time t, then

dW/dt = F * dx / dt

In the limit as dt approaches 0, the time rate at which work is done is called Power.

P lim t0 = dW/dt

Therefore

P = F * dx / dt and we all know F = mass (m) * acceleration (a)

Substituting (m * a) for F we get

Power = mass * acceleration * change in distance / change in time

If we assume the mass of the car is constant and we look at either a change in distance (say a 1/4 mile) or a change in time (say how fast your car can accelerate in 10 seconds) you will see <u>that to increase acceleration you need to increase Power </u>.

Please don't forget that to get to Power from Torque you need to take into account the rpm component - thus horsepower and torque are not directly interchaneable when discussing acceleration.

Jason,
If you really are shifting to maintain the same torque before and after the shift, and if you were driving a stock '01 GTS, you would be shifting at approximately 5100 rpm from 1st to 2nd and 4850 rpm from 2nd to 3rd and 3rd to 4th. Probably not the fastest way down the track.

No flames intended as I think these are great discussions, just trying to provide useful information for those who care to use it.

Please don't force me to get Treynor involved in this......

 

[WCKDVPR]

I found a dyno sheet for a bone stock '01 GTS (418 RWHP), here you go:

Same HP before and after the shift method: 1-2 shift at 6200 rpm, 2-3 and 3-4 shifts at 6050 rpm.

Maximum area under the horsepower curve method: 1-2, 2-3, and 3-4 shifts all at 6300 rpm.

Note: I rounded these numbers to the nearest 50 rpm.

Just the facts..........

 

[Eddie N]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>There is a reason that big rig trucks don't run high RPMs, it to save the engine. They run mid range RPMs and use a gear box to compensate for the lack of RPM range.<HR></BLOCKQUOTE>

not necessarily.. big trucks run low rpm because they have such long strokes in order to make the massive amounts of torque needed to pull a 20 ton load...

good thread...

WCD,

cool link...

- eddie -

 

[Dan Vargus]

The Viper engine is NOT designed to turn high RPMs. The engine suffers from oiling deprevation along with crank shaft wiggle problems. If you modify these engines to turn up the RPMs you'll be buying engines every week. Any of you tuners out there think the Viper engines should be turning 6500+ RPMs???
Thanks, Dan Vargus