Vladimir L

I wonder if I can run this on my stock ECU?

Will I need a V-AFC for now at least?

Wisconsin S2k

Your ECU has nothing to do with compression....

Vladimir L

The fuel though.....Thats why im wondering if I'll need an AFC?

Wisconsin S2k

what about the fuel.... you use just as much fuel on 9:1 as you do on 11:1 or 11.5:1

you dont use more fuel just becuase your CR goes up. you may have to use HIGHER OCTANE fuel to prevent from detonation.

you *could* use an AFC to richen the mixture to prevent detonation, but that's pointless, because you'd basically negate the gains you just made from the higher compression. not to mention that's not the brightest idea, because the ECU will "learn" the AFC an eventually lean out the mixture closer to stock again.

Vladimir L

Thanks Wisconsin comes through for me once again. I can get up to 95 octane here and have a racetrack 5 minutes away.

Wisconsin S2k

you're going to need something that can datalog anyways. if your ECU picks up detonation, you'll likely never know because it will pull timing to compensate and you'll lose power. you WANT to know if your car is detonating, so please, think this through before you go doing this.

pushinlsteg

I believe what he's trying to imply is there enough margin with the setup of a stock ap1 to handle that much compression IN the factor that the A/F ratio is bound to change slightly, does the car stock, have enough fuel to compensate to still run a safe A/F ratio with that little bit more compression.

For instance to solve our problem with a simple question. Does a JDM F20C ECU and a USDM F20C1 ECU have different fuel maps or ignition tables?

I insist a wideband o2 sensor to be safe.

Me personally I think 93 octane fuel and that much more compression should be fine, as you can run a leaner A/F ratio with an NA car.

I tune mostly boost applications and our key A/F under full boost, full load is 11.5:1 A/F ratio to be on the safe side, considering an all motor car you could bump this up to somewhere around 13:1 without an issue probably.

Asura

The stock ECU doesn't like fuel being added with a VAFC. Atleast that was my experience. It caused the ECU to go into limp mode.

Wisconsin S2k

Well the answer here is NO. chaning your CR has very little to no effect on A/F. I thought i was pretty clear on this before....

The ECU does NOT base your a/f ratio on compression. It bases it upon several sensors and inputs, such as tps, map, etc. If compression causes detonation, your car WILL NOT turn up the fuel in the a/f ratio. It WILL pull timing, which will make you lose power. That's a temporary fix to something you need to figure out how to solve permanently.

Our cars do not have a programmable ECU. There is nothing you can do to the car to compensate for higher compression, unless you either install an aftermarket ECU or use higher octane fuel, such as 100+ octane.

Yes. And NONE of those maps will be affected by increasing your CR. I think one problem here is that you need to understand that CR and a/f have ZERO to do with each other in terms of the ECU. You're looking for a correlation that does not exist.

Once again, running a leaner A/F has NOTHING to do with upping your compression. Just because an n/a car can run leaner, doesn't mean a higher CR car can run fine just the same. There is no correlation between the two.

If you have a stock S2000 with 11:1 CR ratio, it's fuel map is going to be the EXACT SAME as it would if you have 11.5:1 CR. If it's an A/F of 12:1 at WOT on a stock car, it's going to be 12:1 at WOT on a car with higher compression.

If you think 93 octane would be fine, you're probably incorrect. Even a stock S2000 will have the ECU pull timing slightly on WOT above 6000rpm. Our knock sensors are almost paranoid about it.

wrong again. the S2000 is a different beast. in fact, the S2000 tends to get near 11.5:1 a/f above 6000rpm and the ECU still will pull timing slightly.

Wisconsin S2k

That was probably a bad install/bad wiring, unless you had it up so rich that the ECU was getting confused and thinking something was wrong with the car.