lower rpm won't run lean:(

[pgfpro]

I have been doing some testing and found out that with my setup anything below 2000rpm with a lean burn of 16:1 or greater and light load my engine starts to miss fire?

I think this has to do with my injectors size 780cc/min and or my low compression 7.4:1

I'm stuck with this because I need the injectors to be the size they are for racing reasons.

I'm glad I did this test because I was going to add a taller 5th gear.

Anyway I thought I would share.

[greasemonkee]

I don't think there's any doubt the injector size can be attributed to a portion of your problem as the fuel never breaks apart and atomizes, but pass out the exhaust as hydrocarbons; you'll never see it on your O2. However, I'd say the atomizing abilities of your precision injectors are far superior to RC's since you've achieved the numbers you have. Upping the pressure may aid to a small extent.

Also, remember that flame speed is somewhat proportional to rpm due to increasing turbulence with rpm. This is the reason why many engines require no or very little timing ramp-up with rpm and actually achieve MBT and peak power thereafter by simply using a flat timing curve. By a simple observation of most stock Honda maps you'll see that, which I'm sure you've noticed.

A stock vtec-e doesn't even engage leanburn until the rpm's come up off of idle.

What gear are you running in 5th at the moment? There may still be room for increase by using an HX 5th - I believe that generation is interchangeable.


Edit: Ahhh, 7.4:1? static compression... Might be worth mentioning that may be a notch low due to today's standards on a turbo app. Even 8.5 is sufficient for 30-40 psi. Personally, I would have issues with going lower than 10:1 because pre-boost torque is golden to me. With high turbulence pistons, we are able to now run moderately high CR ratios, with a matching head chamber to accommodate it of course. Nevertheless, 7.4:1 and those numbers already!! - think of the possibilities...

[pgfpro]

Originally Posted by greasemonkee

I don't think there's any doubt the injector size can be attributed to a portion of your problem as the fuel never breaks apart and atomizes, but pass out the exhaust as hydrocarbons; you'll never see it on your O2. However, I'd say the atomizing abilities of your precision injectors are far superior to RC's since you've achieved the numbers you have. Upping the pressure may aid to a small extent.

Also, remember that flame speed is somewhat proportional to rpm due to increasing turbulence with rpm. This is the reason why many engines require no or very little timing ramp-up with rpm and actually achieve MBT and peak power thereafter by simply using a flat timing curve. By a simple observation of most stock Honda maps you'll see that, which I'm sure you've noticed.

A stock vtec-e doesn't even engage leanburn until the rpm's come up off of idle.

What gear are you running in 5th at the moment? There may still be room for increase by using an HX 5th - I believe that generation is interchangeable.


Edit: Ahhh, 7.4:1? static compression... Might be worth mentioning that may be a notch low due to today's standards on a turbo app. Even 8.5 is sufficient for 30-40 psi. Personally, I would have issues with going lower than 10:1 because pre-boost torque is golden to me. With high turbulence pistons, we are able to now run moderately high CR ratios, with a matching head chamber to accommodate it of course. Nevertheless, 7.4:1 and those numbers already!! - think of the possibilities...

Thanks for the great input!! Much appreciated!

I'm not to sure what my 5th gear is? I'm running 58mph@2400rpm.

I hear you on the compression. I'm actually considering giving this engine to my son and running his old D15 non vtec. Then going with dsm 450cc/min injectors and keep my current turbo setup.

I'm so pleased with the outcome of this setup now and the FE concept. I know with a stock Honda engine I could even gain a whole lot more FE.

[SVOboy]

If you had a second chassis to play around with just for FE that would be fun

Just for reference, the stock VX injectors are 190cc and during lean burn are loaded at <5 usec usually, so I would say injector size plays a big role in your troubles.

[pgfpro]

Originally Posted by SVOboy

If you had a second chassis to play around with just for FE that would be fun

Just for reference, the stock VX injectors are 190cc and during lean burn are loaded at <5 usec usually, so I would say injector size plays a big role in your troubles.

I'm going to look at a 88 CRX today. This would be a much better FE car.