Dyno Question

[911-32]

Quick question: Can you change the peak hp rpm and peak torque rpm just by changing a chip and exhaust?

I always thought you could make small changes to the shape of the curve and could move the curve up but that without changing something like cams you couldn't alter the peak rpms.

Not my car but a euro 3.2 on a Maha dyno just posted these numbers with an SW chip and an M&K silencer (1-in 2-out). Numbers are flywheel (corrected) with drivetrain losses calculated on the run down. Apparently 993s and 996s tested on the same morning were making stock hp numbers - FWIW:

258.3 bhp at 6,739 rpm (126 mph)

torque figure - 207.6 lbft at 6,342 rpm.



What do you guys think? Too good to be true? What can you actually change with a chip and a muffler alone?

Thanks

[Eagledriver]

I would prefer to see RWHP. I don't trust "corrected" numbers. These numbers seem unlikely. Maybe with an exhaust update as well as the muffler and chip you could get close to these numbers.

-Andy

[JeremyD]

Yeah have to agree - that's up there for a chip and muffler - sure they don;t have 993 ss cams?? That peak looks more like a more agressive cam



me in blue, ralph's 3.5 in red and green stock carrera (US version)

[911-32]

Forget the numbers for a second, can you change the curve like this, ie., peak power at over 6700rpm?

[jluetjen]

To do that you'll need to increase your airflow. Basically the engine is at full-song at the peak torque engine speed. Above that the cylinders get incrementally less and less charge due to the mixture not being able to keep up with the engine speed.

To change the airflow you're looking at changing either cams or to a lesser degree the porting. The best results are by changing both at the same time to support your targetted curve.

[JeremyD]

Originally posted by 911-32
Forget the numbers for a second, can you change the curve like this, ie., peak power at over 6700rpm?

I was referring more to the shape and location of the peak HP - cams will determine that more than anything . Is this a stock 3.2 euro carrera? It sure looks like it has a cam profile similiar to mine (and yours) look at where the torque curve starts falling off - very similiar...

[911-32]

...which leads me to believe that there is some BS with these results!

[Steve W]

It will take a lot of cam to make a 3.2 peak at 6700. I have a several 3.2 dyno runs performed on a Maha dyno in Germany, and they also show peak power coming it at 6700 rpm, even though it is a completely stock 89 catalyist equipped motor. So there is some type of discreptancy on the order of 500-600 rpm.