Na4now

My car is a 97 coupe, 6 speed w/ stock 3.42s.

Has:
-ls3 swap (from a camaro)
-227/239 .614 .624 115 +3 VR (stage 2) cam
-ported stock heads
-FAST 102
-ported ls2 tb
-vararam elbow w/ a big haltech filter
-doug rippie 1.75" long tubes
-unknown x pipe
-b&b bullets
-powerbond 25% crank pulley
-stock 42lb injectors on fast rails, and a racetronix fuel pump.

I just started driving the car again, after fixing a bent valve (valvespring broke)...and then banging up and fixing the front bumper and radiator support.

Here's what Im trying to decide. Right now I have ported 821 heads, fast 102 manifold, down to a ported ls2 tb, down to the stock 1997 75mm maf. It essentialy bottlenecks down.

The bought the car with these mods done already...except the fuel pump, rails, intake elbow and filter, and cat back (had borla stingers). I want to have it re-tuned, and figure itd be a good time to change the restrictive 75mm maf. I already have a brand new 85mm truck maf to install....but Im considering going with a card style, in a 90mm or 100mm housing.

I talked to the person at a very reputable local tuning shop, and he recommends NOT switching to the card style and bigger housing. He says it'll be a waste of money, ...and that they have 9 second cars running 75mm maf's.

Others have told me that I'd be holding back 10-15hp, by NOT going switching to the larger maf and housing. That 5mm less, is supposedly a restriction. The cost of the newer card style and 90mm housing, is not a concern. I mean hell....I just spent $400 on FAST fuel rails and fuels lines, cause I thought they looked perty.

It'd be neat to be able to say my car makes 500rwhp on pump...and if there might be a 10-15hp difference on the top end, seems like it'd be worth it.

Opinions from any experienced tuners?

0tom01ss

hey i have a complete 102 setup on my car. tunings a snap 102maf is worth it.

CTD

If you have some dyno runs, drag or track look @ the vacuum data. If it builds you have restriction.

Na4now

Of course I dont have that. I dont have access to a dyno, where I can test parts out.

I have to decide to either use the 85mm truck maf, or use a card style maf with a 90mm housing.....THEN pay to have it put on the dyno and tune it.

Im hoping that someone who has experience with these parts, can weigh in and give me an educated opinion. The guy thats going to tune the car, says its a waste. A different tuner I spoke with says I should change to the card style.

It SEEMS to me, that the 75mm maf would be the choking point...and the 85mm maf would help, but might still be a bit restrictive. If an extra 5mm opening at the intake of the engine, allows it to make 10-15 more up top, I definitely want to get one coming.

0tom01ss

look on the forum chuck cow has shown the 102 ls3 card style maf to make power. it allows for better adjustment via larger window for the pcm to look through. any questions call me as im a tuner/builder 610 931 7384 names tom

tblu92

OK no matter which MAF you use the limit point of the MAF HZ range is installled in your ECM and NOT CHANGEABLE

A 75 mm MAF ECM has a MAX HZ level of 11250 HZ
A "newer style 4" bodied MAF ECM has a MAX HZ level of 12000 HZ
The lastest "card style " LS3 MAF ECM has a MAX HZ level of 15000 HZ
So it's the ECM that dictates wheteher or not you outgrow your current MAF--
If your engine uses fuel/air flow beyond its MAF range it simply uses the last entry in your table which can make it go very LEAN and cause destruction
To do it right and to use exactly what it needs ( not to small -not too big) you simply need to data log your ECM with a data logger or even most any scanner that reads in real time---They all show where on the MAF table you are when its using the most air
On my 98 ( same MAF as your's) with 475 crank HP my MAF goes all the way up to 10500 HZ----So I am just under my ECM's limit of 11250-- If I modded any more I would get too close to the end and would need to make a change--BUT my ECM would need to be changed as well to a newer year to acccomdate the 4" 12000 HZ MAF
Basically an early MAF and ECM are limited to apprx 500 HP
the newer plastic 4" MAF higher --like 600 HP
And the new card type as high as 800 HP
That's why many heavily modded 97-99's replace their ECM to a 2000-2004 ECM so they have more MAF table
PS: I tried running a 4" MAF on my car and spend days and days of data logging and tuning and I felt i could never get it just "perfect"--and saw no HP gains at all---just many driveability issues !!! I ditched it and re-installed my stock 3.5
If you are worried about losing HP by the turbulance and restriction of the smaller size AND are still under 11250 HZ you can replace the MAF ends and remove the screen (I did this) and it made some xtra power but also got me closer to 11250 HZ !!! And MAF ends and screen removal absolutely requires a retune
Confused yet ???

Supercharged111

tblu I don't think the OP's concern is maxxing the reading on the MAF, rather whether or not the size of the hole is costing him power. Doesn't switching to a larger MAF make it take more airflow to hit that same 12000hz (or whatever arbitrary value we're using) as the smaller MAF? Kind of a way of cheating the software. I know sticking the same element in a bigger hole will do that (not an option on LS1/LS6 MAF I realize), but not sure if swapping an early for a late MAF would do that as well.

tblu92

YES somewhat--using a the larger MAF in a 97 may LOWER the MAF HZ reading Say it's 10000 with a 3.5 it may read lower like 9000 on the 4" However this is where you get all kinds of driveability issues---surging dying idle hunting-weird shifts on an A4 -- not worth the trouble to gain really little or NO HP and get in return a crappy driving car
I did address getting better MAF ends or screen removal as a way of decreasing restriction ,as a way to ADD HP--but only IF you are still under your ECM's MAF HZ table after doing the mods

0Chuck CoW

Absolutely correct and considering that this fellas car is an A6 TRANSMISSION the

danger of slipping it and blowing it up is a VERY REAL POSSIBILITY.

He's only changed the MAF and intake for cosmetic reasons.

He called me cause he is local and I explained that I could calibrate the car (and MAF) from

scratch and really that's the only way to do it. Simply splicing the "maf transfer function"

into his calibration would give him a starting point, but not something he could ever drive around

with any level of performance or safety. Additionally, besides changing the MAF itself, the

intake system and filter is NON STOCK which is the second reason that simply changing the

MAF calibration is not going to work.

We install a wideband and go for a good long drive and the maf can be calibrated to perfection.

The rest is easy.....and the trans don't fail either.

Stay TUNED!
Chuck CoW

Zip Corvettes

Why would have to change the ECU? I agree with your statement except for that. The larger the diameter of the MAF the slower the air traveling through it. If the MAF is calibrated correct it should not have any surging because at those speeds they occur you are still in the low speed air mode. I can tell you where you will have issues is going from the Delphi MAF to the Hitachi MAF. On a C6 is pretty easy because you can change the IAT axis to match the Axis on the Hitachi and than just cut and past your IAT transfer function over if you are using HP or EFILive. You can't do it with Diablo but there is still a work around for it. On a C5 though the IAT does not read in ohms, it reads in counts so you have to know how to do the conversion for this. If you don't touch the IAT in the ECU than you can get your temps as much as 20 degrees different which will then screw up the math on the speed density side, which could cause surging and who knows what else.

0Slowhawk

In the 97-05 cars I tend to switch to the GM 85mm setup from the 75mm setup. I like the resolution more.

The card style LS3/7 can be made to work. Transfer the tables like listed above but you have to do the tune correctly. Ve ect table's have to be correct for load tables(auto tranny) then dial in the MAF curve onto that. Most tuners just screw with the MAF curve which can work on M6 cars but can quickly destroy an auto car.

tblu92

Can't go wrong with Chuck's tunes---staying with original smaller MAF 2--------Larger MAF 0
LOL

blown81bu

i had my supercharged c5 tuned..the tuner dumped the MAF for SD tune...
My transmision has now has no 3rd and 4th gear..4l60..drove maybe 35miles
u think its related?

Cosmik de Bris

I had one of those Granatelli MAFs that are calibrated for a cold air system. I wasn't happy with it so I replaced it with an 85mm MAF, i used the MAF table from the later model C5 as a starting point and it ran very well. A little fine tuning of the table was all that was needed.

cvm

I got one of those for by BB truck & complete waste of $ on an untuned vehicle. FS: Granat#@I MAF for 454 chevy. $6 + shipping

0Chuck CoW

Very good possibility..... 4L60e needs to have proper line rise and pressure for 3/4 to hold...and that

happens to be the weak spot of that trans.

Just sayin, replacing the maf for any type of improper MAF/Injector scaling is INSTANT DEATH for most autos....

Especially the 2006+ A6 trans. More tuners kill them than abusive customers.

Chuck CoW

newcastle3

So at what point does the 75mm maf become a restriction and you need the larger 85mm or the card style?

Is it only based on the Hz, or is there a real increase in power by using the larger maf, speaking to the opening size only.

romandian

"On a C5 though the IAT does not read in ohms, it reads in counts ..."

can somebody help me understand that?