How much wheel HP does our Street Hellcat make on our Dyno?

[Unholy707]

But in this case just the headers did add power?

 

[Jack_Toepfer]

But in this case just the headers did add power?

Yes, 40whp on a 930whp car.

 

[Under-Pressure]

What supercharger is on this 426?

 

[Unholy707]

Yes, 40whp on a 930whp car.

Very nice. So it’s safe to assume my ported blower, 108mm throttle body and headers added power

 

[ostmike]

The correct answer is 931 - see the new post I made for more details.

 

[ostmike]

What supercharger is on this 426?

OEM IHI supercharger

 

[ostmike]

Very nice. So it’s safe to assume my ported blower, 108mm throttle body and headers added power

The ported blower will definitely add power.

 

[ostmike]

Maybe I read it wrong but thought this is the tired shortblock dyno before switching to new engine?

That is absolutely correct. That tired factory engine definitely impressed us. Your point is a good one since it would be safe to assume a "fresh" stock engine with the same modifications would produce more power but we cannot prove that.

 

[Jon-MooredPerformanceLLC]

OEM IHI supercharger

Maybe I missed it but what pulley combo are you running ?

 

[ostmike]

Maybe I missed it but what pulley combo are you running ?

10% lower and a 2.85 upper

 

[Unholy707]

Wonder if I can pulley down since I had the snout and bearing plate bearing plate bearing replaced on the 2.4 with “race bearings”. Have a 2.69 upper only, wondering if I can put a 10% lower on

 

[ostmike]

Wonder if I can pulley down since I had the snout and bearing plate bearing plate bearing replaced on the 2.4 with “race bearings”. Have a 2.69 upper only, wondering if I can put a 10% lower on

We have run a 10% lower and 2.65 with race fuel.
Many moons ago we started the smaller pulley journey with a 10% lower
First we ran a 2.85 - good results
Then we ran a 2.75 - better results
Then we ran a 2.65 - best results
Then we ran a 2.50 - good results for a few pulls - then very bad results.........

Now this was on a stock IHI SC about 8 years ago and we have learned much since then but still would not run a 10% lower and 2.5 upper.

 

[Unholy707]

We have run a 10% lower and 2.65 with race fuel.
Many moons ago we started the smaller pulley journey with a 10% lower
First we ran a 2.85 - good results
Then we ran a 2.75 - better results
Then we ran a 2.65 - best results
Then we ran a 2.50 - good results for a few pulls - then very bad results.........

Now this was on a stock IHI SC about 8 years ago and we have learned much since then but still would not run a 10% lower and 2.5 upper.

Very good to know, thanks for sharing. I have a chiller and run e85. Sounds like I might be able to do it (hopefully for more than just a few pulls?)

 

[ostmike]

Very good to know, thanks for sharing. I have a chiller and run e85. Sounds like I might be able to do it (hopefully for more than just a few pulls?)

I am not sure that a chiller or ethanol make a difference here.
The main issue is rotor speed.
Overspeeding these units too much, for too long will always have undesirable results.

 

[Unholy707]

Agreed, I was referencing my fuel since you had listed that the car was on race fuel. So 10% lower with a 2.65 upper is really the limit, for longevity

I am not sure that a chiller or ethanol make a difference here.
The main issue is rotor speed.
Overspeeding these units too much, for too long will always have undesirable results.

 

[ostmike]

Did they retune it for the headers?

No. In this application we did not touch the tune. Since the Hellcat platform is "closed loop" it will self adjust for any needed fueling changes.

Does that car even weigh 4000 lb?

It weighs quite a bit more than 4000#'s! I suspect the car is at least the same weight as stock or very close. We reduced weight by swapping out the front seats and a rear seat delete but added weight with a rollbar and 30# N2O bottle (which we haven't used in ages so we probably should remove it). It may be a little lighter than stock but not by much.

Here is what I have seen with headers. Just installing headers is about a 0 gain. Why, because the gain in power is lost by less boost. So you make the same hp with less boost

Manifold pressure was identical between pulls (with stock exhaust and with the headers).
The stock exhaust manifolds are extremely efficient. When the first SRT Challengers came out in 2008 we tuned a stock SRT and picked up some nice gains. The customer then installed long tube headers and a straight through 3" exhaust and the car lost about 20 whp. Same car, same dyno, different day though. This has also been our experience on the 392 vehicles - no power gain.

 

[ostmike]

Agreed, I was referencing my fuel since you had listed that the car was on race fuel. So 10% lower with a 2.65 upper is really the limit, for longevity

That is our opinion.