My dyno run before exhaust

[Roadster]

Here is a dyno of my '91 NSX with DC Sports headers. Everything else is stock. Unfortunately I wasn't able to do a dyno run before the headers as my car was purchased with them already installed.

I will post another dyno run after I install an aftermarket exhaust system. I am considering the Taitec GT lightweight or doing a custom flowmaster.

The dyno was done on a dyonjet. Max HP, 244.1. Max torque 186.3. See anything out of place on my HP, torque or air/fuel?

Roadster

 

[Boris_DBD]

Isn't the VTec suppose to kick in somewhere? And I thought NSX suppose to have close to 270HP? Sorry I'm new to Prime so these might be stupid questions...

 

[POWERED by HONDA]

Hi Roadster... thanks for doing that. Looking forward to your dyno charts after the exhaust installation. Are you still going with the Flowmaster?

 

[nsxtasy]

Isn't the VTec suppose to kick in somewhere?

VTEC doesn't cause the torque to rise; it keeps it from falling off. This is a very common misunderstanding.

The first misunderstood fact is that acceleration is a function of torque at the wheels, which is engine torque times gearing, less any drivetrain losses.

The second misunderstood fact is that variable valve timing does not increase torque (or, as a result, acceleration) at higher revs. Its objective is to prevent torque from dropping as revs increase. When you look at the torque curve for a VTEC car like the NSX:

you can see that it's quite flat from roughly 3500 RPM to about 7500 RPM, and there is no huge increase above the VTEC crossover point of 5800 RPM. Yes, there is more "power" (horsepower) but that is a mathematical result of the higher revs, and does not represent more acceleration. Acceleration is fairly constant across most of the revband.

The advantage of a wider, flat torque curve like this is in gearing. Cars without VTEC would be forced to upshift by around 6000 to 6500 RPM for optimal acceleration, and when they upshift, they lose acceleration because of the loss in gearing. This is why VTEC cars are so much faster than their torque numbers would imply - because they gain an acceleration advantage from their ability to stay in a lower gear before upshifting.

If you would like a more lengthy explanation, including how horsepower numbers reflect this, read this excellent article about the difference between torque and horsepower, and how gearing comes into play.

I thought NSX suppose to have close to 270HP?

The NSX has 270 hp, measured (as most published power figures are) at the crankshaft (engine). There are losses in the drivetrain (transmission, etc). 244 hp measured at the rear wheels (as most dyno power figures are), net of those drivetrain losses, is a typical figure for a car with headers. Stock, it's usually around 235-240 hp.

Sorry I'm new to Prime so these might be stupid questions...

Welcome,

! Don't worry, we understand; after all, we all had those questions at one time.

 

[ac011]

How many miles on your car when dyno?

 

[Roadster]

Approx. 47,000 miles.

 

[NCC-1701D]

hey 244HP with just a header and stock everything is great


i got this from F.A.Q

Manufacturer Claims
Stock NSX : - 235 hp

With Comptech Header/Airbox/Exhaust: - 245-250 hp
With Comptech Header/Airbox/Exhaust/Cams/Heads : - 265-270 hp
With Comptech Header/Airbox/Exhaust/Supercharger: - 300-305 hp
With Comptech Header/Airbox/Exhaust/Supercharger/Cams/Heads: - 315-320 hp


you are 9HP above stock..i think that great for just a header...

 

[MvM]

hi Roadster,

Thanks very much for posting the dyno.
Did you not install the Cantrell air intake as well or did you dyno the car without it?
I think that your dyno is about right for a stock car with just headers. Probably, with the headers already on it is now the exhaust that becomes the limiting factor.
SoS dynoed their test-car with both Taitec headers AND exhaust and came up with a 22 RWHP plus. So adding a more open exhaust might get you some extra power (and loose some weight too). The link is here:
http://www.nsxprime.com/forums/showthread.php?s=&threadid=20353

The stock NSX in that comparison dynoed at 240 RWHP. However, that difference could be the difference between cars. Not all engines are the same.

I've read the NSX looses about 12% from engine to the wheels. With that in mind your 244 RWHP would translate to 277 HP fro mthe engine.
You might consider the Dali-chip to replace the OEM one. Cheaper than putting on an exhaust and also much easier to undo when you want it. Would be interested to see the results from that.

 

[Smoothaccel]

I had mr car dynoed after headers and saw an increase of 11.1 with headers only. There was no increase with aftermarket filters and the exhaust gave me about 3 or 4 RWHP. Currently I am running DC headers and taitec exhaust and stock intake.

 

[Roadster]

Sorry MvM. Yes, when I dyno'd the car I did have the Cantrell air intake and a Unifilter (stock airbox). I forgot to mention them because I figured they'd have no impact on the dyno numbers.

I should have an exhaust system soon and will post another dyno report.

Roadster

 

[ScienceofSpeed]

Dyno numbers look right for a Dynojet. I've noticed in two separate dyno pulls that headers only contribute about 2-4 hp when used with the factory exhaust. I tend to think that with the early exhaust system especially, the exhaust system is like an electrical circuit. No matter where the resistor/restriction, the net output is affected. However, contrary to this, I have seen some strong numbers with only the headers. There is a lot of variability if the dyno is not run consistently. We offered a $50.00 gift certificate to any one customer that does the dyno before and after installing the GT Lightweight previously, and I can extend the same to you if you're interested. E-mail if interested.

Happy motoring,
-- Chris

 

[Viper Driver]

I tend to think that with the early exhaust system especially, the exhaust system is like an electrical circuit. No matter where the resistor/restriction, the net output is affected.

Sorry to take this off topic, but wouldn't the cats also be a part of this? I was wondering if high-flow cats would need to be installed along with headers & exhaust to get the most out of the system.