View Full Version : MAS problems?

02-17-2006, 08:59 AM
I have been fooling with the Ebay MBC I recently threw in and cannot seem to tune this car to save my life.

Low and mid trims I can keep at 97-103% no problem (1G), and the high trim stays right at about 95%. The problem is a fuel-cut sort of feeling and a pop in the exhaust at around 6K at anything above 40% throttle.

I logged the problem a few times and here is what I know:
-Airflow only outputs a 1600Hz max signal to the logger, so I can't see what airflow is doing when the problem occurres.
-Duty cycles chill at about 75-85% at the onset of boost, hold, and then drop to 40-60% almost instantly just at 6K. This is where the knock skyrockets and I let off
-I have tried adding as much as 35% on the AFC at 6K and it barely changes anything, although duty cycles don't drop quite as far
-No intake pipe leaks or IC pipe leaks
-New fuel filter and pump (Whineboro 190) as well as new plugs (6ES)

What do you all think? MAS issue? I wish I had a wideband or a dyno pull to give you A/F but I do not. It is a 1G MAS with just the lower honeycomb and scilencer removed, I did nothing with the screw in the lower chamber.

If it is a MAS problem, should I go with a GM MAF and MAFT or a 2G MAS? I have had the 2G MAS, but have had no experience with the GM units or the translator itself

02-17-2006, 10:34 AM
Maybe you can borrow a 1G EPROM ECU and DSMLink from somebody to do a few pulls and log everything?


02-17-2006, 09:04 PM
It sounds like Maf overrun. If you went into the negatives with the safc it would probley help. The ecu would see less airflow, hitting fuel cut later then sooner. If you got bigger injectors you could lean it out alot more making the ecu seeing alot less air flow proably never hitting fuel cut.

02-17-2006, 09:28 PM
It sounds like Maf overrun. If you went into the negatives with the safc it would probley help. The ecu would see less airflow, hitting fuel cut later then sooner. If you got bigger injectors you could lean it out alot more making the ecu seeing alot less air flow proably never hitting fuel cut.

It does sound like maf over run, however changing the afc setting wont help since it will still be modifying a bad signal.

My 1g maf over ran past 1800hz. Easy to check with your afc. Switch it to line graph mode, if it gets real jagged at full throttle you are overrunning the maf.


02-19-2006, 08:59 AM
Should I go with the 2G MAS or a GM setup?

I have stock IC pipes, so I don't even think blowthrough would be an option.

02-19-2006, 10:00 AM
My 1g was doing the exact same thing at about 5500 rpms when I put an EVO16G on it and started running higher boost levels. I swapped in a 2g mas and it work fine after that. I would go with that option just because it is cheaper and you don't have to change any of your pipes out. The 2g mas has that oval shape outlet on it but you can stretch the 1g pipe over it and hose clamp it in place to make it work.

02-19-2006, 10:28 AM
My vote is for the 2G MAS. It will definitely be cheaper and since your main goal with this car is sticking to a strict budget, I'm sure spending the least amount of money to solve this problem is at the top of your priority list.

Besides, you're probably going to keep the stock piping, at least for quite a while (again, based on the budget), so doing the GM MAS swap as a draw through, rather than a blow through would partially defeat the benefits of using the GM MAS.

I'm sure the 2G MAS will be just fine for whatever turbo you end up upgrading to, if you even upgrade, or maybe you're just going to stick with what's on there now. I've rambled on long enough, but keep in mind, you don't need to go big to hit your 13-second goal.

In my opinion, keep it simple and more affordable and go with the 2G MAS.


02-19-2006, 11:15 AM
For a bone stock setup, going to a 2g MAF will be more than what you will ever need.

They flow something like 44 lb/min (IIRC) before they start to get overrun. Stock IC systems probably would never flow more than 2/3 of that.

I have a good 2g MAF sitting here if you want one. Let it go cheap too.


02-19-2006, 02:37 PM
Bone stock except for the EVOIII under the hood. ;)

Seems like a great combo, especially if Marcus will sell you his 2G unit for cheap.


02-19-2006, 04:11 PM
I think Dave/Tom on dsmlink forum stated it'll flow 50lb/min unhacked and roughly 10% more than that hacked. I'm pretty sure I read it somewhere.

02-20-2006, 10:38 AM
I'll grab the 2G MAS if it is still around marcus, i'll send you a pm later today.

04-06-2006, 12:16 AM
I'm running into the same problem...only I have a 2G maf already. Im tuning with an safc, FIC 1000s, and an sx fpr. Here is the catch,

Everything was running fine...until I changed my o2 sensor. When I tuned the car on the dyno, I tuned off of a bad o2 sensor. Then, I bought a new one. I got the Bosch universal one that is for a 1G. It only has you splice the wires into the old connector. I also took some CRC MAF cleaner and cleaned my 2g maf just to compliment the cleaned K&N.

I have been running into the same problem as the original poster. I dont have a logger yet, and no one around here has one I can borrow.

I tried to just do a base pull on the dyno, but their wideband aparently had a bad sensor in it....(I didnt find this out until after the pull). My dyno numbers before that day a couple of months ago were 379whp, 378torque. When I did the pull, as soon as I hit around 4500-5000rpms, it sounded like my clutch was slipping on the dyno and took forever to reach 7000rpms. On the drive home, the clutch was not slipping, but felt like I was hitting fuel cut and then when I push in the clutch....KABOOM out of the exhaust followed by a monstrosity of black smoke (fuel).

Some one help me...I am getting owned you tuners.


04-06-2006, 12:53 AM
First things first, did you reset the ECU after you replaced the O2 sensor? If you didn't it could still be reading kind of goofy even with the SAFC. Second thing, are you sure you spliced the wires correctly? I've always had issues with universal parts, especially when you can get an OE part for about the same price. I much prefer to just plug in and go instead of messing with wire connecting. Third thing, when you clean the MAS, sometimes it will leave a residue on the actual sensor which can cause everything to be sketchy.

Those are about the only things I can think of. Smart people will probably chime in soon.


04-06-2006, 02:48 AM
Yes, I diconnected the battery for 1 min. The Maf cleaner is not supposed to leave a residue. And yes, I wired it correctly...black to black....white to white...and grey to grey. The oe sensor is $20 more, the local checker didnt have it in stock, and my old sensor was shot. Not trying to be jerk, and not trying to ask a "noob" question. I am just stating that I am having the same problems as the original poster....only with a 2G maf. All Im asking is if I overlooked something or I made a mistake somewhere along the line, that would be why I am asking people that know a little more about overruning the maf. Thanks guys


04-06-2006, 04:33 AM
Sounds like it's too rich.

1000's are too large for the AFC to compensate for by 5% (450 / 1000 - 1 = 55%). The 2 MAS should reduce that by about 15%, so if your AFC settings at low should be in the -34 to -45 range.

A logger needs to be the *first* mod.