Tunning question

[Gravy]

Something i gotta admit I'm not a pro at, last year i got my A/F ratio right and drove the car, didn't worry about power but just to be safe. Now I'm not looking to put down anything great, just get the car running as best it can, and today toying with the data logger, i came by something odd.

I took it out on the first drive of the year, didn't go faster than 60, and never went above 6188 rpm. However, on that pull in second gear i hit an injector IDC of 78.9. But with upgraded injectors, is the logger seeing the expected OEM 360cc injectors or the 450's i have in there now?

Also can't seem to find the info on what i'm looking for, i know under hard driving 11-12 is a good AFR, but what does everyone shoot for while cruising at say, 55 down the highway?

I have other questions, but i gotta google them before i post up in here.

Gravy

[Shane@DBPerformance]

IDC is IDC regardless of what injectors are in the car.

The factory ECU will use the stock O2 sensor to shoot for 14.7:1 A/F during idle and cruise. If you lean it our or richen it up, the ECU will just override it and try to go back to 14.7:1, if everything is working correctly. Normally you try to get the fuel trims as close to 0 or 100(depending on how your logger reads) as possible, so that the ECU is having to compensate as little as possible.

[asshanson]

Injector duty cycle won't matter what injectors you have, it should be accurate. I believe it's based on what percentage of the time they're on, not a factor of how much they're actually flowing.

If you're just using an AFC or something like that, you can't really adjust the closed loop A/F ratio, the ECU will shoot for 14.7 automatically and adjust fuel trims to reach that.

Edit: looks like Shane beat me to it.

[Gravy]

Thanks for the info, may end up swapping the 550's back in than if i run into any more problems with the 450's. Sounded like a good idea, better control and able to make smaller adjustments but maybe not. Now i've just gotta figure out how to log the wideband 02 with the unit i have. May need a different cable.

[niterydr]

Thanks for the info, may end up swapping the 550's back in than if i run into any more problems with the 450's. Sounded like a good idea, better control and able to make smaller adjustments but maybe not. Now i've just gotta figure out how to log the wideband 02 with the unit i have. May need a different cable.

Since you are using an air flow correction you want the closest injectors to factory as possible, aka the smallest ones you can get away with. 80% IDC's is fine for most injectors, when you are constantly running them around 90+ is when you can see failures over time.

The 450's will allow for more degree of control over the 550's. Most of this has been covered on 3si.org, very specific information to the 3s.

[Shane@DBPerformance]

Most factory ecu mitsu dataloggers are off on their duty cycle calculation anyways. Some of the ECUs give out Injector Pulse Width(IPW) and dataloggers use a guesstimate calculation based on IPW, RPM, and dead time to try to give a duty cycle, but they are usually off. Like Evoscan is a good 15% off at high duty cycle. 115% duty cycle in Evoscan is more like real 100%. Systems like the AEM EMS give true duty cycle, but a box like that can do it because it is actually controlling the injectors.

The whole 80% duty cycle thing that books and injector makers recommend is BS. Even some OEMs run them well past 80% on stock cars.

As Josh said, with an airflow tricking system like an SAFC, you want as small of injectors as you can get away with. The more you have to deviate from 0% in the SAFC, the more unintended sideeffects start happening.

[Gravy]

I think tonight i'm gonna set the MAF translator to -20% across the board, i'm running around -15% to about -18% so i'll be able to run closer to 0 on the safc, but i'm pretty sure that's still gona give me the same results as setting the safc to -20.

And the reason i went with the 450's is i had to run e-85 on the 550's to prevent running around -30 to -40 to keep the AFR correct. I've almost wondered if they are larger than 550cc's but a run of the part number confirmed it twice now.

[Shane@DBPerformance]

I think tonight i'm gonna set the MAF translator to -20% across the board, i'm running around -15% to about -18% so i'll be able to run closer to 0 on the safc, but i'm pretty sure that's still gona give me the same results as setting the safc to -20.


Yea, the SAFC and MAFT trick the factory ECU in exactly the same way, so it doesn't matter which you pull 20% out of.

[Gravy]

E-85 keeps sounding better and better. Found out part of my problem, plugs gapped at .038-0.40 is giving me some MAJOR spark plug blow out. Got the knock under control, but the WOT is hard to keep happy with the blow out happening.

Got the new set of plugs, going back to the original wires that were on the car, new one's i'll hold till i need them for now.

[Gravy]

Double posting over making another thread since it's in the same ball park, but i ran into some interesting issues tonight on the stealth. To lay out a quick run down:

Car stock injectors are 360cc, i have 450's on there.

I've switched back over to e-85 and can NOT get it running right. Last year on 550's i still had the settings around -20 all the way down the RPM range. This year trying it on 450's, I'm +20 just to keep it semi happy running at low throttle or cruising. It runs at idle around 14.9-15-5 at that point, but my high settings are -10% and when i get under WOT it goes to 9.9 and i hit fuel cut even as low as -25%. For the life of me, i didn't have the logger to check IDC but does this make ANY sense to anyone else? I'm about ready to drop the 550's back in cause i know they didn't have any issues really last year on it.