Thread: Troubles tuning setup with MAFT + SAFC

Firstly I'd like say what's up to everyone, this is my first post here at sac dsm, I usually post on dsm tuners, but havent been able to get much help there lately :?

EDIT* I wasnt sure if there was vehicle profile section so I dint list my mods. Couldnt find one so I'll list them.
open-element 3" filter
Evo 3 16G
2.5" short-route FMIC
Tial bov
650's
255 walbro (rewired)
Aeromtive AFPR (37-38psi)
3" GM MAF
MAFT
one-step-colder NGK's
Evo GT exhaust manifold
ported 1G O2 housing
2.5" catless exhaust
MBC
SAFC 2
Datalogger
boost and egt gauges
EGR blocked
FIAV bypass plate
TB vacuum lines blocked

Anyway, I've been having a tough time tuning my car ever since I installed a GM MAF and MAFT. Prior to that I was running the stock 1G MAF and tuning with a SAFC. With that setup I was able to come up with a fairly decent tune and according to the butt dyno was making good power. After the GM MAF and MAFT install it seems like no matter what I try the ECU just wants to fight and the car just wont wont run the way it should.

The trims just dont seem to want to cooperate or even show me any sort of pattern on why they end up where they do. I first tried zeroing out the SAFC and using the MAFT to establish a "driveable" tune, then using the SAFC to fine tune for power, no. The car wont even idle right without using the SAFC to coorect idle airflow. It requires at least +45% correction and the MAFT tops out at 35-40%, cant remember which. So I incorporated the SAFC along with the MAFT and my O2 trims are still going fom super rich to super lean depending on how much airflow is present.

Ok, I suppose I should let you guys know what settings I'm using.

SAFC
LO:
1k 21%
2k 14%
3k 5%
3.6k 7%
4k 19% (I dont understand the hug jump in correction needed within only 400 rpms)
4k-7k 19%

HI: I havenet even been able to do any 3rd gear pulls to set the HI.

On the MAFT I have the base/aux set for my injectors 650cc, idle is set at 25% making a total correction of 46%. I adjusted the mid control one click richer.

With that my O2 trims range between 60% up to 167% (max) during cruise conditions. Upon initial take off from a stop the O2 trims quickly dips to 60-70% cuasing the car to bog for a split second and then the trim shoots up to 120%+- and the car pulls nicely. When cruising ~45mph 4th gear the O2 trims stay close to 167% in both the mid and high trims.

Needless to say I need some help. If anyone is experienced with these tunign devices, specifically the MAFT, please chime in. Also if anyone knows of a tuner in town that knows these system well, please let me know because I will pay to be able to extract the power this car is capable of making.

I just did, thanks. I'll read through them tonight and hopefully learn something new.

First of all,

how is your valve cover breather hose and PCV valve hooked up?

Originally Posted by DROOPY209

First of all,

how is your valve cover breather hose and PCV valve hooked up?

The PCV valve is hooked up in stock configuration with a brand new factory PCV. As far as the VC breather, it is also as it is in stock form. The intake I have has a nipple on it so I can run the VC breather. I have a small catch can inline to keep the vapors out.

I don't see any aftermarket injectors or aftermarket fuel pump on your mod list, so, I would have to recommend that you remove the AFC from the equation for now. Don't just zero it out. Disconnect it from your car, and re-connect the wire you cut by your ecu. For now, Don't add unnecessary piggy-back tuning devices since it will only complicate things more then they already are. Establish the best decent tune with the GM MAF-Translator. Set it for your injectors 1st. If the Mid and High Fuel Trims are still too lean, then set the Translator to 440cc or 430cc injectors if you're running stock 450cc's. Don't worry too much about the Low Fuel Trim as 120-130 will still be able to be corrected by the ECU when you're car is on. After you do all this, Drive the car for a few days so the ECU can recalculate and establish the Fuel Trims correctly. Do this first.

You might wanna follow up with a boost leak test. It's pretty obvious that unmetered air is entering the cylinders. Same exact thing happened to me when I bearly installed my GM MAF-T in a blow-thru setup.

Usually, some people get rid of the PCV system all together and just run the hoses down behind the tranny to get atleast some vacuum while driving to suck out the fumes, and cover up the pvc nipple port on the IM. That is what I'm gunna do pretty soon. I just finished hollowing out a spare PVC valve last night.

This way, you would eliminate your PVC and breather lines as probable cause.

A boost leak test from the TB would be in order. Make sure your boost gauge hold the -20hg of vacuum for a while.
Just for giggles, I would do a boost leak test from the turbo also.

post back with your findings.

I just updated my mod list, forgot to mention the fuel parts :roll:

I've done many boost leak tests lately. I found a few on the TB, replaced those gaskets and added some rtv, I replaced the shaft seals in the TB as well. With pressure applied to the TB elbow I can hold 18psi. Prior to hooking up my boost tester to the TB elbo I had it hooked to the intake pipe with the VC breather niple plugged. The only leaks I had were at the TB at that time. I've been meaning to do another one but havent gotten around to it yet. If there are any other leaks they are small and only occur above 18psi so I wouldnt expect that the trims associated with cruisng would be affected by those.

As far as my PCV and VC breather setup goes I would think that they are not a problem. Like I mentioned my PCV is brand new and a factory piece. The VC breather is still hooked up like stock which from what I have read is ok.

Today I reset the ECU and changed some settings on the MAFT. I zeroed out the mid and wot settings. Set the base/aux for my 650's and turned the idle down to 3 (15%) and adjusted the idle on the SAFC. I didnt do any driveway tuning of the low settings on the safc yet but already my cruising O2 trims went down to 70-80%. I spent most of the day installing a nw thermostat and a second SPAL fan to help with my high coolant temps when stationary or in stop and go traffic. I would regularly see 209-219* and up to 230* on the logger :( So now I have a 14" and 10" fans along with a manual switch so I can run the fans whenever I want to. With both fans running I let the car aidle for about 10 minutes and the temps never went over 192* :P

Now I can much more effectively sit with car running and tune the first stage of the low settings. I'l play with those the next couple days and see what the low and mid trims do.

I appreciate all the help so far!

keep us updated, as i am getting my maft and logger set up this weekend and any inside tips help


not to mention lee's write up was GREAT!!!

Ski Bum, keep in mind that in stock form, the VC breather hose gets its air after the air has been measured and accounted for by the stock maf.

With the GM MAF-T in blow thru mode, that air entering the VC through the breather hose will not be measured by the GM MAF and when the engine is in vacuum, all that unmeasured air will make it into your cylinders without ever being accounted for.

That is your problem right there. With that setup, you're fuel trims will never be around 100%.

You're gunna have to change that VC breather hose/PCV valve setup that you have.

You're making some good progress.

post back with your findings.

Originally Posted by DROOPY209

Ski Bum, keep in mind that in stock form, the VC breather hose gets its air after the air has been measured and accounted for by the stock maf.

With the GM MAF-T in blow thru mode, that air entering the VC through the breather hose will not be measured by the GM MAF and when the engine is in vacuum, all that unmeasured air will make it into your cylinders without ever being accounted for.

That is your problem right there. With that setup, you're fuel trims will never be around 100%.

You're gunna have to change that VC breather hose/PCV valve setup that you have.

You're making some good progress.

post back with your findings.

I never thought of that. I had the VC breather setup prior to the GM MAF and never changed it. So then should I just throw a filter on the VC breather port and call it good? In that configuration wouldnt there still be unmetered air entering the cylinders under vacuum conditions? So it would seem the best configuration would be a port after the MAF? I wonder if any of the vacuum ports on top of the TB would work for that. The when there is vacuum present at the VC breather port it would be puling in metered air.

What about connecting the VC breather to PCV lines somehow?
How about something like this: