RotorManiac

then Ford did a good job on the Focus RS, it has only 12hp loss, thus making more than 200hp on the wheels...

Charles R. Hill

iTrader: (7)

I wouldn 't consider myself "the" authority on such things but those are the numbers I use and they work pretty well for me. As for the RS, of course Ford did a good job on that drivetrain! How many of us would relish the opportunity to drive one of those machines? Especially in full-WRC gear?

CRH

01Racing

I am sorry but i cannot agree with Mr Hill on tuning carburation. You can tune a carb on a dyno in perfect air conditions, however once on the street or track elevation and ambient air conditions have a huge impact on your tuning. Most fuel injection systems now use a mass air flow sensor that will compensate for air density, altitude etc.

RochesterX8

Sometime last year, a guy I know who worked in the auto business said he read in one of the mags that the mazda ecu was SO 'smart' that it could sense that the car was stationary (not enough pressurized air flow and retarded the power.
I have also read (Car & Driver) that BMWs do something with the ABS sensors so it knows the car is not being driven.
I don't know if these issues have been regularly discussed here or not.
IMHO knowing your hp for bragging rights is one thing. However, as long as the results are consistant and you can tell a mod has made a difference in your output, you should be happy.

Fanman

A lot of times companies underrate hp. The Focus RS isn't losing only 12 hp, it is that the engine is probably running at 225 hp, but they are rating it at 200 hp. For example many of the Mustang Cobras were rated at 390 hp, but when dynoed were putting out 360-375 hp at the wheels. Porsche is notorius for this. I saw a friend's GT3 put out 365 whp for a car that is rated at 375 hp at the crank. Or their new 911 S that will run step for step with a Vette through the 1/4 mile despite being slightly heavier & down 45 hp (throw out gearing).

Unfortunately it seems we got the short end of the stick in that we seem to dyno very low compared to what our rated hp is stated as. If we were really making 238 hp we should be dynoing around low 200's (similar to the S2000's). Oh well, one more reason to get a Canzoomer or FI.

Charles R. Hill

iTrader: (7)

The reason fuel injection systems need a MAF, Baro sensors and the like are because they do not use engine vacuum to draw fuel into the engine like carbureted systems. Therefore, they must predict what the fuel needs are based on sensor measurement and not physical airflow. Also, ECU's, although fairly sophisticated, are still very limited in their abilities to adjust to all the different parameters that must be considered. The resolution in automotive ECU's is not near enough yet to render carbs obsolete, nor have all of the real-world issues of engine tuning been solved by a computer program/programmer. A horrible tuner with a laptop will still lose to a person with a complete understanding of how engines react to loads and the value of a good vacuum gauge.


No need to be sorry about disagreeing. We're grown-ups just sharing opinions and ideas. That's where the best threads come from.

CRH

superhuff

I dynoed mine yesterday and only got 171 rwhp. Seems a bit low but im definitely not surprise. Its hard for a 1.3 L engine to get that power to the wheels hehe. On the other hand my buddy Dynoed his S2000 and got almost 200 rwhp. Thought that was kinda interesting.

124Spider

Yeah, I dyno'd my S2000 the same day as a bunch of local guys dyno'd their RX-8s. They were getting 185rwhp uncorrected; I got 219 uncorrected, 210 corrected. What was especially intersting was that I got only a little higher torque than they did. These cars are rated almost identically--238/161 vs. 240/162.

Methinks Honda under-rated the 2004/05 S2000, and Mazda certainly did not under-rate the RX-8.