Hi all.

Apologies if this question has been answered before/previously (I did search, but didn't find anything directly answering this). My interest is in the D17 engines in the 2001+ Civic EX models.

As I understand it, (all?) modern Hondas use a speed-density EFI system which relies on a MAP sensor and Volumetric Efficiency-based tables in the ECU to determine the amount of fuel to be injected. When you install bolt-ons such as the common I/H/E, the VE is increased over a stock configuration. How is it that the engine doesn't end up with an overly-lean condition using these parts? Is it because:

-the VE increase is not sufficient to make a difference?

-the closed-loop control is enough to compensate for the change? If this is the case, what about at WOT or any other condition where the ECU goes open-loop?

-there's something else I'm missing?

Thanks.

 

Bump, hope someone knowledgeable will answer this.

 

with obd2 it rearrages itself, so it ends up like it was before. obd1 and before doesn't, so as the exhaust flows out the exhaust the o2 sees the a/f ratio is skewed so it adjusts the fuel to compensate for the increased airflow, thus more combustion & more power.

 

I'm not sure I understand this. If the VE is higher than stock for equivalent atmospheric conditions, throttle position, and engine speed, then either the ECU has to compensate for it, or the engine is leaner than stock. Period. If it compensates, you should make some more power (obviously not big gains with simple bolt-ons). If it doesn't you should run hotter than stock. From what I know these things do make power on the OBD-II engines.

This would be the closed-loop control I was talking about. Still not sure what happens when you go open-loop, like I assume it does at WOT.


[Modified by torquesteer, 1:13 AM 3/24/2003]