rosey

iTrader: (13)

Posted this on the efilive forums, but as it would apply to any ls1 tuning software package, I'm putting it here as well.

Motor is a 2000 camaro ls1/t56, ported 5.3 heads, 227/239 113+2 cam, bolt ons, in a 89 rx7 with a 3.55 final drive.

So I made a new intake several months ago, wanted to try a credit card style maf(ls3/ls7 style). I bought the maf new from gm and a flange to mount it, had it welded into a 4" aluminum pipe as shown.


I then inserted it into an intake made of pipes and couplers, and a LS2 C6 blackwing intake, excuse the dirtyness...


Having been through the autoVE and autoMAF processes many times, I figured it would be a piece of cake to redo the maf calibration table. I started with the table bruce melton and lingenfelter both give out as a starting point for an 100mm maf on an ls1...
http://powrmax.com/PowrMAF100%20Tables.html

Set the b0120 value to 400rpm and logged mile after mile, applying BEN corrections as I go, and while the idle and WOT stuff wasn't too bad, steady cruising and low throttle would cause very jumpy fueling, nothing seemed to help. The logged maf frequency seemed to jump around a lot, so I decided to put the stock maf in place of the 4" ls7 maf pipe and compare. The stock maf worked great, and the results are precisely what I expected to see, but unfortunately I don't have much of an explanation for it.

First the ls7 maf, this screen shot is just steady ~70mph crusing. the purple line on the bottom is maf freq on a 3000-4000hz scale. Notice the yellow AFR line in the second chart, it's all over the place, remember, this is after many long driving cycles and BEN correction factors having been applied(EFIlive screen shot)...


Next is the ls1 maf, which is a stock 00 3 wire 78mm maf that has been descreened but is otherwise stock. This was with a slightly tweaked stock maf calibration table, but it could still use some tweaking. Even in its slightly rough state of tune, notice how much better actual AFR follows commanded. The purple line at the bottom is maf freq on a 4000-5000hz scale. The drop about half way through is just from a slight backing off of the throttle, but it is pretty obvious how much more steady the signal is(EFIlive screen shot)...


Has anyone else had this problem, or is there an explanation for this that I may be overlooking? I would love to figure this out and be able to go back to the ls7 style maf, seeing as the stock one is a slight restriction, but more importantly I will max it out when spraying(dry nitrous).

Thanks for reading...

carlrx7

i just did this same mod,, the problem is turbulence. ideal is 6" before the front of the sensor and 6" behind the sensor, sometimes you just cant do it.


air flow needs to be straightend out

here is a pic up mine.



i can feel the car want to buck down at low airflow grams

im going to try puttin a screen in, like this stuff,

http://www.saxonpc.com/7-inch-black-cell-honeycom7.html

Petraszewsky

iTrader: (28)

^^^Nice link and I have read about the air not being "straight" before...Sometimes in conversions where a custom CAI is made the MAF is properly positioned and has similar affects....

carlrx7

i talked with jason at SaxonPC and he sent me the 3/4 thick x 3/16 aluminum screen cut in a 4" circle, should be here on friday,, will post up some scans of the HZ. monday.

-Carl

Kaltech Tuning

iTrader: (17)

One of the other issues here is that the hz table in the ls7 computer has much better resolution than the ls1. Just look at the 2 logs you posted, the ls7 hz are 1100 lower than the ls1 maf but it should be the same airflow. What was the logged maf airflow with the ls1 maf?

I've encountered this issue when trying to put this style sensor onto and ls1 car and it's a real pita. Due to the difference in scaling you really chop down the resolution of the ls1 maf table even more.

What kind of power are you making with this setup?

I'm all for experimenting and getting more air into the motor but you'll have to figure out if the time is worthwhile or if an 85mm ls1 style maf will suite your needs.

rosey

iTrader: (13)

I am running a fairly mild (IMO) H/C ls1 in a street car. HP is likely in the 425-450whp range. The part that gets tricky, is I am running a dry nitrous kit, currently set up to use a HSW interface controller. This controller modifies the maf signal to increase fueling, and while I have yet to push the stock maf over the limit, I think a stock maf is, or will be a limiting factor. The 5hp that I am picking up n/a is a bonus, and might as well try since I already have the stuff.

The logged airflow is pretty close between mafs, aside from it being super jumpy with the way the ls7 maf is currently configured. The loss of resolution is a necessary evil based on the fact that it must cover a boarder range of airflow with the same table as stock. While the 08+ PCMs have a better table for this(brought out to support the ls9), the original 06 ls7 table is only marginally better so I do believe if I can achieve laminar flow across the element, tuning will be a piece of cake.

I hope this works for you, and can't wait to hear your results. Pics would also be good if it isn't too much trouble

I might not get to figure this out before winter, but so far I have the following things to try...
1. Replace the corvette air bridge with a 4" bend so the cross section is the same from the air filter to the throttle body.
2. Space the maf sensor out to try to find some less turbulent air closer to the outside edges of the pipe.
3. Experiment with adding a screen.
4. Anything else I or anyone else thinks of...

Petraszewsky

iTrader: (28)

What's the inside diameter of the housing??? 100-110mm??? I've also read that the LS7 maf does differently inside different diameter housing...??? I doubt this is it just throwing it out there...I think it was over on HPtuners site that I read that....

rosey

iTrader: (13)

Its just mounted in a 4" OD tube with a 0.060" wall thickness. If my math is correct that is a 98.6mm inside diameter. It may help to try slightly difference pipe sizes, but intuitively, I think having the same size pipe all the way through would be best to keep turbulence down, and building multiple intakes would be cost prohibitive for me. Because the air filter outlet and TB are both 4" OD, that size is the natural choice.

carlrx7

check this out:
http://www.hptuners.com/forum/showthread.php?t=26546

Petraszewsky

iTrader: (28)

Nice read...Just like I had read before about placement before/after bends and turbulence...^^^Keep us updated on how well it does....

rosey

iTrader: (13)

Good work, I will certainly try some of the ideas bouncing around in that thread.

Thanks.

southpaw0314

iTrader: (5)

did you ever figure out the problem?