Intake / Exhaust mods vs ECU programming?
12-05-2003, 06:10 AM
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Intake / Exhaust mods vs ECU programming?
I've been wondering. I've seen "many" posts throughout the forum on aftermarket intake manifolds and exhaust systems. Have you folks needed to change the ECU to account for the change in the engines breathing efficiency?
My impression has been that the S2000 uses a pre-programmed mapping system to calculate fuel flow under various conditions. It seems to me that changing the intake or exhaust to improve air flow would compromise that programming. OTOH, if the car uses a "mass air flow" sensor of some kind, the ECU would be better at compensating.
Just wondering. Thanks for any info!
Drive Safe,
Steve R.
My impression has been that the S2000 uses a pre-programmed mapping system to calculate fuel flow under various conditions. It seems to me that changing the intake or exhaust to improve air flow would compromise that programming. OTOH, if the car uses a "mass air flow" sensor of some kind, the ECU would be better at compensating.
Just wondering. Thanks for any info!
Drive Safe,
Steve R.
12-05-2003, 06:16 AM
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The S2000 uses a MAP sensor (manifold air pressure) to determine how much fuel to deliver. That's not to say that changing the i/h/e wouldn't benefit from a different fuel delivery per a given sensor reading, but I don't know of anybody who's studied this. Some stock S2000s have seen up to a 10 hp increase with proper VAFC tuning, but I haven't seen much about what a VAFC can do with a modified engine...
12-06-2003, 11:37 PM
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Steve is on target here. I use an S2000 engine in a Westfield (similar to a Lotus 7) with an AEM ECU for engine management. I have experienced that intake and exhaust configuration have a MAJOR impact on fuelling. Your situation is likely substantially different (and probably better) than mine, but my experience suggests that arbitrary adustments of your intake and exhaust may have unexpected consequences.
My exhaust runs into a 2 1/2" muffler system, a straight-through, 12" long MagnaFlow followed by a straight-through, 24" long SuperTrapp with 12 4" disks and a solid end plate. 12 disks is the maximum supplied by SuperTrapp. Using a wideband O2 sensor, I tuned the system for an air/fuel ratio of 13:1 at WOT, independent of RPM. Since my fuel delivery was significantly less than the AEM base maps, I started looking for why my engine wasn't breathing well, considering both intake and exhaust. Completely removing the intake had no effect. But removing the end plate from the SuperTrapp changed my AFR from 13:1 to 15.5:1 on the high speed cam -- pretty much independent of RPM (same fuel, 15% more air). Obviously I'm going to change out the SuperTrapp. But the lesson is clear -- the fuel maps need to be coupled to the specific intake and exhaust configuration.
With the stock Honda ECU, the O2 sensor is only active at idle and cruise and the MAP sensor dictates, open loop, the amount of fuel being delivered under other conditions. I understand that a stock S2000 will probably make a bit more power if leaned out some. But how much? And how much are you leaning it out with your bolt-ons? The more effective they are, the more you're deviating from the Honda design target.
I'd suggest that if you change your stock intake or exhaust, then you should put your car on a dyno with a wideband O2 sensor and find out the effects of what you've done. It may be great as is stands. Or it may require some adjustment to your fuelling. I've damaged enough engines from lean running that I wouldn't want to fly blind again.
My exhaust runs into a 2 1/2" muffler system, a straight-through, 12" long MagnaFlow followed by a straight-through, 24" long SuperTrapp with 12 4" disks and a solid end plate. 12 disks is the maximum supplied by SuperTrapp. Using a wideband O2 sensor, I tuned the system for an air/fuel ratio of 13:1 at WOT, independent of RPM. Since my fuel delivery was significantly less than the AEM base maps, I started looking for why my engine wasn't breathing well, considering both intake and exhaust. Completely removing the intake had no effect. But removing the end plate from the SuperTrapp changed my AFR from 13:1 to 15.5:1 on the high speed cam -- pretty much independent of RPM (same fuel, 15% more air). Obviously I'm going to change out the SuperTrapp. But the lesson is clear -- the fuel maps need to be coupled to the specific intake and exhaust configuration.
With the stock Honda ECU, the O2 sensor is only active at idle and cruise and the MAP sensor dictates, open loop, the amount of fuel being delivered under other conditions. I understand that a stock S2000 will probably make a bit more power if leaned out some. But how much? And how much are you leaning it out with your bolt-ons? The more effective they are, the more you're deviating from the Honda design target.
I'd suggest that if you change your stock intake or exhaust, then you should put your car on a dyno with a wideband O2 sensor and find out the effects of what you've done. It may be great as is stands. Or it may require some adjustment to your fuelling. I've damaged enough engines from lean running that I wouldn't want to fly blind again.
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