Honda S2000 - black smoke at WOT

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Joined: Sat Jun 29, 2013 6:07 am

Honda S2000 - black smoke at WOT

Postby surfer » Thu Apr 16, 2015 5:00 am

Having a bit of a head scratcher with my S2000. It is a supercharger F20c running a Haltech Platinum pro plugin ECU. I've extended the fuel and ignition maps to take the boost pressure and tuned it to a pretty solid 11.7 - 12.2 AFR in boost with a nice smooth transition from the 14 AFR in high vacuum areas of the maps.

However under full throttle the engine smokes with what looks and smells like unburned fuel, I'm struggling to tune it out, I've advanced and retarded the ignition a good few degrees and it does nothing to help get rid of the smoke. I'm wondering whether I need to adjust some of the less played with settings like injector firing angle, coil pack dwell time etc.

Has anyone else had similar problems? I'm going to start with firing angle and see if that helps but any advice would be gratefull received.

Posts: 127
Joined: Mon Sep 22, 2008 8:05 am
Location: Denver, CO, USA

Re: Honda S2000 - black smoke at WOT

Postby Enthalpy » Sat Apr 25, 2015 8:19 am

At 11.7 AFR, some smoke is kinda normal. This is assuming it's excessive:

My first inclination is to look at spark blowout. If your ignition is having a tough time keeping the spark alive, you will start to get sporadic misfires that will burp unburned fuel out the exhaust. This makes the AFR read leaner, causing the unsuspecting tuner to unnecessarily add fuel. Make sure your coil dwell is set correctly. Blindly increasing your dwell is a recipe for burned out coils and/or igniters especially over time. Try dropping the gap on the plugs. Make sure your ignition components are strong like the wires. One way to see if it's spark blowout is to drop the boost. If the problem very quickly goes away with a pound or two, then it could very well be ignition system strength.

The next thing I would look at would be validating the AFR you are reading with a 2nd wideband ideally WAY downstream, like near the rear of the car clipped onto the exhaust tip. The reason for this would be temps. At the high temps of WOT, the wideband can get overheated and read incorrectly. In lieu of being able to do that with a wideband, try adding 10% fuel globally. Under WOT, you should see the AFR change accordingly (assuming your injector offset is correct).

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