Tuning Idle with Chrome - Some confusion

[DrGonzo]

So I have gone over and over GregE's thread on tuning Idle and somethings are missing and some are contradictory to what I have found/been told in the past. So I'd like opinions, thoughts, answers, etc.

To begin I am currently working on two cars, My own and a local friend. Basic specs are

Mine: 93 Stealth

• Chrome ECU
• EVO 560's
• 13G turbo's

Friends: 96 3000gt

• Chrome ECU
• DSM 450's
• 15G turbo's
• 10:1 Engine

1.
So to begin the problem I am having with both cars is the difference in Low Trim between the front and rear bank. Now this isn't something suttle and I know they can be off, But in both cases F/R is bottomed out and the other is floating around 0 +/- "Center point depending what your logging with". So one bank is fine and the other the ECU is trying to pull fuel. I took my car out for a drive today to get it inspected and monitored the trims on my LCDBC. Rear is floating about 95 and the front is bottomed out at 50.... This was after about an hour of driving around. mids both F/R are sitting at 50 "more about that later" So should I even worry about the two banks being that far off as it looks to stabilize in the mid range from what I can see. I have pressure tested the system, made all adjustments to idle and such and the TB is freshly rebuilt. So it's not a vacuum leak or anything. The cars purrs at idle and cruise without any issues at all. O2's were also swapped out thinking it was a bad O2 sensor when I had the crappy Lucas 550's in there.

2.
Going from GregE's tuning post here: http://www.3sgto.org/tuning-engine-e...flash-ecu.html

So the first step is to tune your car so that the O2 sensors are cycling in closed loop. It's not that closed loop targets any specific AFR, all the ECU is trying to do is get the sensors to cycle between .1 and .9 volts. Unless there is something really screwy with your setup, there isn't any reason why the ECU won't operate in closed loop right out of the box with your injectors scaled.

Right now my tune consists of nothing more than disabling the periphery I need to, Scaling the injectors to 560 and setting the latency found on Injector rehab. With that my trims are pretty much bottomed out at 50 on LCDBC. So my understanding is that means the ECU is trying to pull fuel and I need to increase the injector scaling to like 580 and go from there. Am I right that the lower or negative number means the ECU is pulling fuel as it is too rich and I need to lean it out. According to GregE in his post it is opposite, a negative means it is lean and needs more fuel:

Say, for example, your Low trim Front is -10.6% and your Low trim rear is -2.8%. We want to get that front trim back above -5% but not going so far that it brings the rear trim out of spec either. What this means is we want to add at least 6% more of fuel to bring that trim within spec. Tuning Chrome to bring those trims back within that 5% range is actually quite easy.

I don't want to mess with the MAF smoothing yet as I want to get the injectors scaled overall to have the trims decent and then fine tune the trims with the Maf Smoothing. Is this the wrong approach? Should I just set and forget the injectors at 560 and adjust it all with the MAF Smoothing table?

3.
His threads also point of that in EVOScan you need to set the injector scale but he doesn't go into why/what. What is the injector scaling used for in EVOScan, it is doing nothing but displaying the data from the ECU so why should it care what the injectors scale is? If it is needed for some reason, are you setting the stock scaling of 360, or matching it to what you have the scale set to in Chrome?

4.
As for Injector Scaling how is it being used? Is it figuring the difference from stock and seeing the new value is now 30% larger so increase all fuel related stuff by 30%? I know the code is used in many different cars besides the 3S and they all use different injectors, so wanted to know if this is a formula in the code to figure out the map, or does it just use a percentage off a baseline to adjust the fuel tables.

Let me know your thoughts on the above as I may just be overthinking it all.

[Greg E]

1: did you reset the ECU when you installed the new injectors?
2: don't be afraid to play with the MAF smoothing. That's all calibrated for stock turbos, stock intake tubes and inter coolers.... It's not that there's anything wrong with playing with the injector size value, it's just a more guess/check style of tuning vs tweaking the percentages in the MAF smoothing to get everything spot on.
3: older version used that number for calculating IDC. This is done in the ECU now so don't worry about that anymore.
4: I used to have the entire formula memories from air pulses all the way to fuel pulses. I've posted it before in other threads. In the code, lowering the injector size value gives you MORE fuel and raising takes it away.

[DrGonzo]

Yeah ECU was reset. I don't leave the battery connected when I park the car in the garage as I don't want it being drained. So I always disconnect the negative terminal. Especially in the winter time. Summer when I drive it more I may keep it connected.

As far as trims, when the numbers is bottomed out that means the ECU is trying to pull fuel correct? and if the numbers is maxed then It is trying to add fuel?

So no need to set injector size in EVOScan, Good to know as I thought I was really missing something on that one when I cam across that.

Good to know my thoughts on injector scaling were correct.

[Chris@Rvengeperformance]

Did you use the lagtimes for the evo 560s that the evo guys use? They are really close.

[DrGonzo]

I used the ones I found on here, somewhere....

No clue what the Evo guys use. Too much random information out there without any actual evidence to prove. So I went with what I found and was going to adjust as needed.

[futurevr4man]

This is an evo sticky that I think Gump is referencing

How to: Get a basic tune with ECUFlash | DSMtuners

[DrGonzo]

Yeah, that is about worthless. If gives a single number not a voltage/range.

[DrGonzo]

On another note I spent most of today at a friends house working on his 96 trying to figure out the rear O2 issue that looks to be the cause of the trim problem. We though it was fuel so swapped his 390cc to my 450's, then swapped the 450's to my known good 360's thinking they all had a bad injector. Testing each injector in Evoscan turning each one on/off we found the #6 did not change so we though OK bad rear wiring somewhere. So checked wiring, ECU, Etc. My Greene MultiMeter took a dump so went and got a new one and decided to test the injector pulse at the rear bank wiring. Found out all injectors were working fine. Retested turning them on/off and found that the #6 injector test does absolutely nothing.... Now I'm pretty sure that test worked fine on my car so not sure why #6 injector test ion his 96 does not work.

So back to it being an O2 issue somewhere. now both front and rear O2's are brand new, Like last week brand new. If I plug the front O2 into the rear EVOscan gets a signal of it cycling. Plug the rear into the front and nothing. So looks like the brand new O2 we got was shit right out of the box!! He is exchanging it out but the new one won't be in till Tuesday.

[Chris@Rvengeperformance]

I used the ones I found on here, somewhere....

No clue what the Evo guys use. Too much random information out there without any actual evidence to prove. So I went with what I found and was going to adjust as needed.

Merlins guide has them.

[DrGonzo]

This is not a latency issue with my car. If it were latency then the car would idle and cruise like shit which it does not. Latency would also not cause one bank to be bottomed out and the other to be at 0 +/-. Latency would affect both banks at the same time.

Right now I need to get some seat time in mine to fine tune things as I think that will get my issues into check. Mostly this was questions in regards to tuning and everything has been answered except for clarifying:

Am I right that the lower or negative number means the ECU is pulling fuel as it is too rich and I need to lean it out. According to GregE in his post it is opposite, a negative means it is lean and needs more fuel