Tunning question

Gravy · 05-18-2009

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** · 05-18-2009

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** · 05-18-2009

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 · 05-19-2009

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 · 05-19-2009

Quote:

Originally Posted by 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.

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** · 05-19-2009

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 · 05-19-2009

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** · 05-19-2009

Quote:

Originally Posted by 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.

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 · 05-25-2009

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 · 05-27-2009

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.

**Shane@DBPerformance** · 05-27-2009

Too lean at cruise and too rich at WOT usually means a boost leak.

Gravy · 05-27-2009

Yeah, i'll run though it tonight, but i've got a feeling it's been there the whole life of the car while i've had it. The AFR also jumps alot, and after reading Josh's tuning bit on 3si.org, i have much to work out.

niterydr · 05-28-2009

Quote:

Originally Posted by Gravy

Yeah, i'll run though it tonight, but i've got a feeling it's been there the whole life of the car while i've had it. The AFR also jumps alot, and after reading Josh's tuning bit on 3si.org, i have much to work out.

It is much better to tune a solid vehicle versus trying to tune around mechnical problems and limitations. I always recommend boost leak tests, spark plug tests, and vehicle inspections for all "tuners" atleast once a year. Saves on headaches.

Gravy · 05-28-2009

Cracks around my waste gate lines on both sides, fixed the leak and now the afr is much more stable. Took it for a few spins and got 111% and 115% IDC on e-85. Either i'll have to stick to 92 or upgrade to the 550's again.

One thing i have noticed, and i'm not sure if it's something i havn't been able to find or just isn't out there. But both of my 02 sensors cycle the way they should, but on the wideband, since the day i've had the car/wideband in there. It will start off cruising fine at around 14.5-14.9 and than as i've heard nytrider describe in the tuning post on 3si, it "Switches" from 14.8 or so down to 11.4-11.5. It will continue to run at that range untill i let off the gas and register 0.0% on the tps, than it resets and runs there for a minute or so, than will switch back. I tried tuning for the higher afr range and the lower. But it still switches no matter what.

So if i try and tune it to run on the "High" setting as i'll call it, it runs great for a minute or so after getting in gear. When the minute is up, it switches to the "Low" setting. If i tune for the low setting, it starts off in the high, than switches to the low and runs great. The problem is it is runing super lean to start with and i can't get on the gas at all without terrible knock and a heavy miss. Everything on the logger looks fine, i throw no codes and the only lite on the car is the SRS for the airbag.

The only thing i can think of, and it still doesn't make sense, is the car is set up to vary the voltage to the fuel pump, but i have a rewire done. So it just sees a higher voltage than it probably wants to see. I've tried re-setting the ecu(pulling the battery over night) and trying to get the car to relearn the fuel curves but with no luck. The EGR system is removed from the vehicle, but i've had that on and still had the same problem as i do now.

Any ideas on what to check? Full out boost leak test is coming, i just have to get a couple 1 3/4" caps to put on the turbo's and tap a tire valve into them.

niterydr · 05-28-2009

Quote:

Originally Posted by Gravy

Cracks around my waste gate lines on both sides, fixed the leak and now the afr is much more stable. Took it for a few spins and got 111% and 115% IDC on e-85. Either i'll have to stick to 92 or upgrade to the 550's again.

One thing i have noticed, and i'm not sure if it's something i havn't been able to find or just isn't out there. But both of my 02 sensors cycle the way they should, but on the wideband, since the day i've had the car/wideband in there. It will start off cruising fine at around 14.5-14.9 and than as i've heard nytrider describe in the tuning post on 3si, it "Switches" from 14.8 or so down to 11.4-11.5. It will continue to run at that range untill i let off the gas and register 0.0% on the tps, than it resets and runs there for a minute or so, than will switch back. I tried tuning for the higher afr range and the lower. But it still switches no matter what.

So if i try and tune it to run on the "High" setting as i'll call it, it runs great for a minute or so after getting in gear. When the minute is up, it switches to the "Low" setting. If i tune for the low setting, it starts off in the high, than switches to the low and runs great. The problem is it is runing super lean to start with and i can't get on the gas at all without terrible knock and a heavy miss. Everything on the logger looks fine, i throw no codes and the only lite on the car is the SRS for the airbag.

The only thing i can think of, and it still doesn't make sense, is the car is set up to vary the voltage to the fuel pump, but i have a rewire done. So it just sees a higher voltage than it probably wants to see. I've tried re-setting the ecu(pulling the battery over night) and trying to get the car to relearn the fuel curves but with no luck. The EGR system is removed from the vehicle, but i've had that on and still had the same problem as i do now.

Any ideas on what to check? Full out boost leak test is coming, i just have to get a couple 1 3/4" caps to put on the turbo's and tap a tire valve into them.

Do you see the vehicle bounce around on the tuning software (forgot what you are using)? Is it grabbing two maps possible? How do the plugs look? A really good wideband can actually show a missfire, I've see them show as lean or rich, depends upon the load and sensitivity of the wideband.

How old are the 02 sensors? You are watching the wideband switch correct? It sounds like you are running between closed and open loop.

**asshanson** · 05-29-2009

Does the airflow signal look normal when this happens? Or is it really just the car running rich with nothing else changing? Can you log a bunch of sensors to verify nothing is changing?

Gravy · 05-29-2009

I should have over a dozen logs, and i've tried looking for anything that changes, Hrz doesn't change any that i've seen, tps doesn't move, but when it goes over the oxygen sensors do register it. Twice in the past two days now i've got it to throw a CEL. However, when i go to pull it nothing is stored. I've even tried to read it when the light was on and still shows up nothing. Happens if i cruise for a long time at the 10.1:1 or around that area, so i assume it's giving me an Oxygen sensor code... but why it doesn't stay is beyond me.

Tonight i'll be going though the logs, i have everything logged as of right now, and am going to make sure nothing is changing when this happens, but i havn't seen anything yet. Someone said it could be the alternator, and i thought long and hard about it, but that's not coresponding, neither is any extra draw or anything else. When the alternator is on, i see about 13.8-14.1 volts, and when it's off it sees high 12's. However it doesn't corespond to the switching. I'm thinking of improving a few grounds and adding a few to the engine bay to rule out that as an issue, but i've got no reason to think that's a problem.

Still quick enough to keep away from a camaro with exauhst, so performance isn't affected at all. Just runs kinda rich, and ruins my gas millage.

May have found something, front 02 is cycling MUCH quicker than the rear, rear doesn't cycle often and when it does it's only for a short time. Doesn't seem to match the symptoms of the rich/lean problem much, but it looks to be a good place to start.