I'm not an ingenier and it can be a silly question , but
I have read some mail that claim that running lean gives
HP...

I wonder how it is possible (I thought that less fuel = less explosion = less HP )
Is that because the mixture is not completely burned when the piston goes up
and then it brakes it ?

 

I always heard lean is for fuel economy, and rich is for power.

 

Everything is relative in the lean VS rich game. It is not running lean that gives you HP, it is running leaner when the mixture is too rich. The theorytical optimum A/F ratio is 14.7:1 (going on memory here) but because this ratio is a little risky for detonation and manufacturer are conservative they usually program a richer fuel curve (around 13:1).

 

The P73 ecu is rather rich in the upper rpm range.

Taking out 'some' fuel will help produce better power.

 

(or english major)

Running lean doesn't actually give you more HP. It does make the engine run hotter due to the smaller cooling capacity of the lesser mass of fuel.
Running leaner puts the engine closer to it's stochiometric (perfect) fuel to air mixture so the engine tends to run more efficiently. However, too lean and you’ll have a detonation condition form pre-ignition caused by too hot an engine. Too rich and you’re just wasting gas.

 

Would you rather he post the question in French?

 

s'il vous plaît



[Modified by sackdz, 8:24 AM 10/28/2002]

 

Yeah, ideal stoichiometry A:F ratio is what you want... but due to liability & repair cost, most manufacturers run rich (and, waste your gas money).

Speaking of A:F... those who have tuned w/ V-AFC, what A:F curve (using wide-band O2 sensor) is ideal without being risky? Would getting a J&S help in preventitive measure, in case things go ape-****?

 

I ran at the strip with an a/f ratio in the mid 14's at WOT (it was a hondata mischip)and the spoon oil shield that protects the oil pan from heat burnt to a crisp. A/F in the constant 14's at wot is too hot and I lost up to 12 hp all through vtec because of it. In my tuning experience with my car an a/f ratio in the low 13's give the best power.

 

Thanks to all reply (even on my spelling mistakes... )

Another question : I have read that JDM 4-1 header lean the mixture.
Then, when I'll put my DC JDM Header on my R, do I have to increase
the fuel pressure or let it lean for best performance (I'm also at 19° ignition
timing...) ?

 

Mine ranges from 12.1 to 13.8 in others...just depends upon what the car liked when we tuned it.

Austin