Hondata

I am looking for some guidance on setting up the injector overrun manifold pressures. The motor being used in this particular S2000 has a few major differences over a stock F22. The engine is a custom build, with increased bore, stroke (99mm) and compression (12.5:1). Also, the head has some mild work, including larger intake valves and an aftermarket cam. The throttle body is a J37 unit, and the manifold opening has been machined to match the TB outlet.

Therefore, the amount of vacuum vs. rpm under deceleration is no longer the same as the old F22.

Here is what I have in mind to tune the Overrun Manifold Pressure tables:

1) Datalog the following condition. Run engine to redline in 2nd gear, release throttle and allow the car to decelerate on its own down to idle (no brake pedal). Repeat this procedure in 3rd, and 4th gear, in order to determine any variance due to gearing, tire friction, aerodynamic drag, etc.

2) Analyze the MAP curves over rpm for deceleration in each gear. With this data, generate a curve using the highest kPa values seen under vacuum during decel.

3) Add approximately 2 kPa to the generated curve. Use the data points from this new curve to set new values for the "Overrun Cut Off MAP Low Cam (cut)" and "Overrun Cut Off MAP High Cam (cut)" maps.

4) Set both the Low Cam and High Cam RECOVER table values approximately 3 kPa higher than their CUT table counterparts.


Please provide comments and suggestions for this plan of attack.

I'd just do a single run in 3rd and then set the pressures about 3 kpa below the value you see. There's no real disadvantage settings the pressures low - the injectors will still cut on overrun based on TPS.

Thank you for the reply.

When you say set the values around 3kPa lower than what I see, you're talking about the CUT tables, correct? I guess I would offset the RESUME tables a couple kPa above my cut values, to ensure adequate hysteresis? What would happen if I simply 0 out both these tables (since fuel cut will kick in via TPS anyway)?

From what I know, there is no TPS threshold setting for overrun fuel cut. I guess this is hard coded and not user-definable? Out of curiosity, what is the TPS value for the fuel cut? Is it let's say, 1% across the board, or does it vary by RPM?

Cheers,
Alan

Yes, the resume should be a couple of kpa higher than cut. I would not make any of numbers 0.

TPS cut is fixed across rpm at around 0.5%.

Thank you kindly, sir!

Hondata wrote:I'd just do a single run in 3rd and then set the pressures about 3 kpa below the value you see. There's no real disadvantage settings the pressures low - the injectors will still cut on overrun based on TPS.

Would choosing the "overrun throttle opening enabled" option provide the ECM with a detectable TPS reading that allows the OP's suggested changes to actually work for overrun functionality based solely off of MAP and RPM? I ask because surely the TPS would read something with the feature enabled but I'm just not sure if it would be above the 0.5% required to keep overrun cut from occurring. Thoughts???

Hondata wrote: Sun Dec 01, 2013 8:57 am Yes, the resume should be a couple of kpa higher than cut. I would not make any of numbers 0.

TPS cut is fixed across rpm at around 0.5%.

Should I set the value 3kpa lower than the maximum kpa value on overrun, in all "cut" cells? Or should I set each "cut" cell 3kpa lower than the individual value that I see at each RPM cell specifically (1800,4000,5500,8500 etc.) ?

The best way would be for the pressure at each rpm point. Also, too low tends to be better than too high.