Patrick G

iTrader: (14)

Wow, that was an exercise in futility. I take all this time bolting up the SLP 85mm MAF (screenless) and dialing the a/f ratio in perfectly with the MAFT and I show 0 gain! As a matter of fact, it was a slight loss.

Everything else was the same in testing. Air was nearly identical. O2s were .900mv in both MAFs (stock, unported, screenless MAF), timing was 26 degrees in both applications. L-Trims were at 0% for both MAFs. Everything was the same except for the physical size of the MAFs.

I guess this goes to show that a 400 rwhp motor does not need any more airflow than the stock unported MAF will give it. Any gains by running a ported MAF most likely will come from additional timing or getting a more ideal a/f ratio. Sorry for the bad news. I was hoping for at least 5 rhwp gain. Good thing I borrowed the 85mm MAF and MAFT from Judson. I would be pissed to spend all this money to go the same speed or slower.

Phil

Good results Patrick...MTI has tested this before and found zero gains also. I do think if I rember correctly that it does work on the stroker motors. <img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

Dave

I suppose that's why they come that size from the factory...

how much gain (if any) did you get from the coolant bypass mod?

Patrick G

iTrader: (14)

No gains from the coolant bypass mod (measurable anyway). I just like keeping the intake charge as cool as possible while keeping the shortblock hot.

Straight Line Performance

I would have expected a few hp too. Very interesting.

Thanks for the info.

McRat

We got the same results on bolt-on cars.

At the same A/F ratios, with the same timing, stock engines do not need anything other than the stock MAF.

All of this came about because the 98 cars ran better with leaner fuel curves. Mod'g the MAF showed gains NOT BECAUSE of better flow, but better jetting.

Starting in 2000, the stock fuel curves are leaner to achieve SuperLowEmissionsVehicle rating SLEV.

GMAF's and ported MAF's lose power on 2000 and up cars in most cases. 85mm aren't much if any better. On Steve2000SS (?) car, we ran both the SLP 85mm and the stocker. I believe the loss was 3hp on the SLP unit.

Skelton

My gmaf gave me consistant .1 better performance than my stock meter. On the dyno, I show 12.8 across the rpm range under WOT which is probably close to 13.1 at the track(more load). For some reason it works for my 01. My 11.44 @ 119.59 bolt on car shows that I'm making the hp. When I try a stock maf, bam 11.50's every time. Gmaf, bam, 11.40's. I haven't tried them on a dyno though. Just track tested on 2 seperate days with the same result, lost .1 every time.???? I need to get some atap readings for some possible answers. <img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

Patrick G

iTrader: (14)

Yes, I would not have been surprised about no gains on a stock '98 LS1, but my car has Stage II heads/cam and pushes out over 400 rwhp uncorked. I would have expected SOME kind of gain. Live and learn.

Patrick G

iTrader: (14)

Y2K Blackbird,

No doubt you picked up from a better tune-up...either more timing or a better a/f ratio...it certainly wasn't from airflow, I assure you. Remember, on my car, the only variable was the airflow. Timing, a/f ratio, L-Trims, and testing conditions were identical between the MAFs. It was about as controlled a test as possible.

Jason99T/A

iTrader: (21)

My car made 442rwhp w/ the stock, umported MAF with the screen removed. I was thinking about trying the SLP 85mm MAF, but I'm glad I didn't. <img src="gr_stretch.gif" border="0"> Timing was 29* w/ 0 KR and 02s in the 910mV range. I was using Thunder Racing custom tuning.

Jason

Supertrapped

Great work Patrick <img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

wizkid

iTrader: (3)

Wouldn't it make sense that the HP gain seen by people with ported MAFH would come from the bump in timing some see since the crossectional area not correct anymore and the sensor is not calibrated?

When Onfire and I flowed the induction pieces on the flowbench, the stock unit with screen was not far behind (very close) the GMS unit (it is wide open for those that don't know). Just a little fyi.

Eric

Skelton

I agree with you 100 percent on that Patrick. Your test was done under exact conditions and proves its not an airflow issue. I was just stating that the gmaf works for me on my current setup. I'm sure it has something to do with timing and not airflow since it seems more responsive with the gmaf.

McRat

Just a little off the subject:

I'm a "dyno *****" <img src="gr_images/icons/wink.gif" border="0"> I've dyno'd my internally stock 2000 LS1 engine 31 pulls. I've watched/helped roughly 100 other LS1's dyno, mostly bolt-on cars. #1 problem with poor performance? MAF/MAFT issues. They are always fixed by a stock MAF. We keep one handy or swap from another car.

Some things I learned:

GMAF's seldom work for LS1's. At least on the dyno they don't.

Leaning the mixture ADDS timing, and increases HP up to .87 02 readings, then KR starts kicking in.

Rich mixtures pull timing, and HP.

No HP is to be found by changing the timing from 25-30(stock) to 29-31(programmed). The motor SOUNDS better, and gets better part-throttle response, but no gain in peak HP.

Racing gas DOES NOT increase HP on stock engines with less than 2.9° KR. It will eliminate KR, but not increase HP. Again, the engine sounds better and feels better.

No Airlid has EVER made 17rwhp. Neither has a K&N <img src="gr_images/icons/wink.gif" border="0"> .

WICKED SS

iTrader: (36)

I have A descreened SLP maf and when I first put it on I didnt really notice anything, but one time at the track I wanted to try out the stock descreened maf to see if there was A difference and my car felt slower? Is this cause I just put it on and it didnt have time for the computer to relearn? The only thing the slp maf has done for me is make my car run lean and when using nitrous I notice my car runs A little funny from being lean.
How do you think maf ends would do for A car putting over 450 to the wheels or maybe even the pace, I know the pace is the same size as the slp but different sensor? This maf stuff is driving me crazy <img src="graemlins/gr_guns.gif" border="0" alt="[guns]" />

Crazyquik

Ok Patrick, so what kind of MAF rate of flow do you get? At what point would the 75 mm MAF start to be a restriction, and at what point would it max out?

Ragtop 99

iTrader: (7)

Sorry to hear no gain. I was thinking if you got 5 HP above 5000 it would be worth it.

Did you solve your top end breathing issues?

Ragtop 99

iTrader: (7)

[quote]Originally posted by Crazyquik:
<strong>Ok Patrick, so what kind of MAF rate of flow do you get? At what point would the 75 mm MAF start to be a restriction, and at what point would it max out?</strong><hr></blockquote>

Jason at MTI told me he sees about 10 HP on a 422 and had the same results as PG on a stock cube motor. Looks like you need more cubes or maybe FI.

J'sRamAir

Maybe this has been subtley stated already, but a good direct answer would be helpful to me. So you guys are saying that on my mostly stock '98 (the 'rich' year) that I would benefit just as much from a MAFT (to adjust a/f ratio) as I would MAF ends or another MAF? I'm not going to go out and buy a MAFT and A-tap just to tune my 'stock' car, but I was just wondering (will be buying MAFT after headers and cam). If this is true, buying MAF ends would be pointless. Correct?

99 Black Bird T/A

iTrader: (4)

J'sRamAir,

If your at dyno day in Belmont with the fbody club, we can switch on my SLP 85 MAF and/or MAFT and see if they are worth anything for you WS6.

Email me.