is a MAF-T good enough for a dyno tune?

[Crazy91GSX]

Hey guys.. let me lay out my problems here...

I have noticed alot of surging lately.. the feeling of fuel cut almost.. perhaps its compressor surge.. once in awhile, in a 2nd or 3rd gear pull, the car will act as if i nailed the brakes and nose dive, power drops completely and it'll blow off, then pick right back up again.. the whole time I am a wot.

also, the egt's are climbing (even at night time) above 1600* at anything above 18psi on 93 octane. So, I tried to richen the wot setting on my maf-t a bit. But, I can't do that. Even one click and the car studders the whole time under boost. I adjusted it last night and this morning. Both times, one click rich and after boosting two full gears each time, i had to adjust it right back because it studders. so, i just dont take it past 6k to make sure the egt's dont rise.

i might want to point out that the egt probe isnt flush in the runner. the hole has some stripped threads, so I can only thread it in half way. you think this will cause an inaccurate reading?

this along with what feels like retarted timing from knock (studdering), makes me think a dyno tune is in order.. especially since it does not feel like 20psi should with the extensive amount of mods the car has..

I took it to a dsm shop here in Houston and they did a road tune with me. Had to adjust some fuel trims and such, but just did a basic tune.. so, to revert back to the original question.. will a maf-t provide enough tuning capability for a GOOD dyno tune??

Adam

 

[tstkl]

I personally would not waste the money on a dyno tune if all you have is a maft. You could probably ask your local mechanic to drive with you and tune it with a logger, which would be cheaper and just as effective since all your tuning with the maft is airflow, and your not even using it in rpm mode it sounds like.

 

[Crazy91GSX]

thats exactly what he did.. rode with me and watched the plam pilot.. changed the settings as needed..

i have no clue how to tune with the maf-t.. what is the rpm mode? is it more beneficial to tune with it?

also, the only other things I have that are helpful with a tune is the EGT and an AFPR.. I was looking into DSMLink.. but no money for that at the moment. Thus the reason for the dyno tune.. cheaper, but optimizes the setup i have now (at least I thought so)

 

[mavisky]

It sounds like you're hitting fuel cut or have a big boost leak.

Since your mod list isn't up to date I'm also going to assume you're on 450 injectors, maft, and a 14b.

The maft replicates a stock unhacked mass airflow sensor which means that anything over 17psi will result in you hitting fuel cut on it, and 18psi on 93 octane is too much for stock injectors and a fuel pump without an AFPR to bump the base fuel pressure up some. Are you knocking at all or is it just running that lean that you're seeing 1600 degrees?

Tell us a little more about your setup and we can provide a more accurate diagnosis.

 

[Crazy91GSX]

Sorry, I did forget to update my mod list. Hell, its a whole new car.. but here ya go..

block is 30 over w/8.3:1 cr, head has a mild port, a 3 anglejob on 1mm oversided valves and 3g lifters. Has a extrude-honed intake mani and ported evoiii turbo/mani/o2 housing. full 3" atr exhaust, dsmotorsports fmic w/ 2.5" pipes, GM mas, MAF-T, tial bov, dejon intake. Fuel consists of 660's, afpr, 255hp pump. I have the base idle set to 38psi w/ vacuum disconnected.

 

[GSntncT]

I would have to say no. The maf-t is a good thing to have, infact I still have and use mine. However, it will only get you close to where you need to be, as the adjustments are just too wide. For a finer, or better tune, something like a SAFC is needed imo.

 

[mavisky]

Sounds like you might have the same issue I did.

My setup is similar fuel wise FIC 650's, rewired 3kgt vr4 pump, afpr set to 38psi, maft only. I've got mine dialed in at a safe 1500 degrees right now on my 18g.

I was blowing the spark out on a set of 6es's that had somehow gotten into my motor. Switched back to a set of 7es's I had laying around at a gap of 25 and it runs a solid 20psi on 94 ocatne from Sunoco. I've only got the maft so if you'd like I can give you my base settins and you can give them a try if you'd like. My big gapped plugs were fine at 15-16 psi, but when it would spool hard straight to 20-21 then it'd stumble on what sounded like a rev limiter and dump black smoke out the back since the plugs weren't lighting.

 

[Crazy91GSX]

Sounds like you might have the same issue I did.

My setup is similar fuel wise FIC 650's, rewired 3kgt vr4 pump, afpr set to 38psi, maft only. I've got mine dialed in at a safe 1500 degrees right now on my 18g.

I was blowing the spark out on a set of 6es's that had somehow gotten into my motor. Switched back to a set of 7es's I had laying around at a gap of 25 and it runs a solid 20psi on 94 ocatne from Sunoco. I've only got the maft so if you'd like I can give you my base settins and you can give them a try if you'd like. My big gapped plugs were fine at 15-16 psi, but when it would spool hard straight to 20-21 then it'd stumble on what sounded like a rev limiter and dump black smoke out the back since the plugs weren't lighting.

I pulled the plugs just to check and they were 7es's and were gapped at 26. I dropped the boost down to 18psi, and richened up the maf-t one click at wot, but still climed past 1600.. i dont know whats goin on with my friggin car.

 

[mavisky]

Has your fuel pump been re-wired? I know that with my vr4 pump it would get lean up top, but after a re-wire it didn't, although you shouldn't have that problem with a 255, it's not a bad idea either way.

What kind of timing and knock are you seeing.

 

[Crazy91GSX]

yes, the fuel pump is hotwired.. and knock count was at 0 when we tuned it.. im not sure about the timing..

just to double check.. to richen up a maf-t, the knobs rotate clockwise, correct?

 

[GSntncT]

Well, take a look at the graphs that came with it(if you have it). I know if you go clockwise too far, you will set a seriously negative value.