Must not be making enough power

PCM here, maxing MAF out!!!

 

Sorry to ask a question related here but off original topic;

Didn't LPE (Lingenfelter) create something that helped combat maxing out the MAF's for the LT1's?

 

Just wondering because I'm a little confused as to why I'm not showing signs of maxing.

1. What indication does your car give you when it maxes?
2. Is your MAF descreened?
3. Are you still OBD2 or did you convert to OBD1?

My PE tables are smooth and don't have any points where I have to begin adding excessive fuel. I've seen guys claim on here they are maxing at 460HP and I know I'm making more than that. Dynojet Wideband Commander and Tuner cat for OBD2 has the AFR at 11.8 and very smooth. No signs of maxed MAF.

 

I guess the only way you are going to be able to tell if you are maxing the MAF is to use a scan tool. Mine maxes right around 4700 rpm. The stock table maxes at 471 gps, I have mine doctored to max at 510 gps, so it's adding a little more fuel when it maxes (still maxes at the same frequency). After the MAF maxes, all additional fuel is added via the PE table.

Bill

 

I'm trying to find out the difference between our computer and fueling setups so I can track this down.

Steve

 

Stock MAF (with screen), Converted to OBD1.

Bill

 

With your setup: 97 WS6 Trans Am, 10psi P1SC FMICw Mondo Bypass, 224/232ex 113 LSA Comp XE Cam, Ported Lt1 heads, 60# Mototron injectors, 58mm Holley TB, Custom Dual Walbro, Harlan Sharpe 1.6RR, Cloyes True Roller, Rebuilt Stock rods and crank with ARP bolts, -20cc dish TRW forged blower pistons, Delteq Ignition, Meziere Electric WP, Pacesetter LT's, Dual 3" Cats, Hooker Catback, Bilstein shocks, BMR SFC's, C5 Brakes you are almost certainly maxing the MAF. And so what?

Rich

 

You may not really have any "signs" of it if you're not scanning it (since you won't go lean if the PE vs RPM has enough fuel to compensate and it may not require a big spike to make up for it). If you are scanning then what is your MAF reading to?

SMOKIN'Z ...how'd you "doctor it" to read higher?

 

He adjusted the MAF tables (last 4 tables in Tunercat). For X grams of air the MAF will produce Y frequency. You just alter the X value. Anything much over 500 gps and the computer will freak out though so be careful. My old combo was maxing the MAF around 4500-4600 with the table set to around 490 grams max.

 

Hmmm, interesting ...so he just increased the values in the table (if it's like LT1 Edit) to get more fuel. I thought GPS was just a fixed thing, as in ..it measures the air coming in (grams per second) and adds x-amount of fuel based on the frequency selected for a given grams per second. That being said, I haven't even tuned for like a year ....so I'm only using limited memory resources lol.

I have messed with the MAF table in LT1 Edit before, and yes, it is very sensitive to changes. I had no idea it could alter max GPS displayed though ...I guess I thought I was altering the frequency ....oh well, arghhh, been too long ago.

 

No, the MAF still produces the same frequency, you're just telling the computer to interpret it differently. But, like I said, the computer can only be pushed so far before it says no.

 

ok, so it thinks it's seeing more air as a result of the alteration and adds more fuel as a result. For purposes of defining power output (some say GPS is usually ~ 1:1 with rwhp on the M6 cars) this change wouldn't be appropriate then.

Anyone have any data that concurs or differs with the ~ 1:1 theory? (just wondering if my little Powerdyne is really capable of ~471 rwhp with this 355)

 

I adjusted the MAF high threshold setting so that I would not get a PCM error. Many have commented that OBD2 PCM systems will cut injector pulse in half of the MAF high freq. threshold is exceeded. I think I had this problem with my 383 - D1. LT1 edit version 2.2 had a new feature to set this value @ 60+K over the stock setting of 10.7K. I think it works based on WOT runs. Also, I used a Dynojet WB O2 system to calibrate the closed loop MAF (stock MAF cal lower by 2%) to fuel closer to 14.7:1 AFR. The stock MAF cal fueled very rich with the D1 @ low speed closed loop. Now it runs much better (13.7 to 14:1 - AFR) since I used the WB O2 sensor. Also, since the PCM continues to adjust the BLM values, I have found that setting the BLM update to higher MAP value (60 kpa) helps with maintaining the AFR @ lowspeed and idle (with my set-up).
Hope this helps.

 

I'll scan it this week when I get home from my trip. I just figured that maxing the MAF would be noticeable on my dynojet wideband O2 guage. I thought maybe since I'm one the few that still use OBD2 that I had a freak MAF/computer or something.

Ya, I guess I should be happy. Thats been an expensive problem of mine. Fixing stuff that ain't broke.LOL

 

I scanned for a maxed MAF and sure enough it is maxing. It doesn't happen until 6000 rpm though. 471 gps at 6000 rpm on the Autoxray scanner. It was so close to my redline that it was barely noticeable on the wideband. I guess I will have to upgrade to a D1SC so it will happen much earlier in the rpm band.