Tuning LT1 for Supercharger.. which way is best?

Just wondering what everyone else has found to be the best method to tuning a supercharged car. I'm going to be using a P1SC procharger system.

And btw, how would you tune the PCM for the charger? The VE tables?

I voted for PCM tuning because using a FMU is hard to get the AFR steady and consistent. The FMU is just one more thing to break and cause problems. My car was extremely easy to tune using the mototron 60 injectors.

My tune is very similar to a stock tune. I've raised the timing at idle to about 28 degrees. I then reduced the timing in 95-100KPA areas to about 27 degrees. I also changed the WOT vs RPM table to make my AFR 11.8 at WOT. I never touched my VE tables. I'm using the MAF on the pressure side and showing no signs of it being maxed out.:)

Thanks, thats what i was thinking. Just wasn't sure if the MAF would be able to adjust for the extra air when you start getting into the boost at part throttle.

PCM here too. I've really only touched timing tables and WOT vs RPM table like 97WS6 and also have 60 pounders in there. I've changed other things also like the constant for the injectors, cooling fan temps, rpm fuel cut offs and such, but mainly when tuning, timing and the WOT vs RPM table is all i touch and i've been able to get A/F's spot on, until my fuel pumps started running out of fuel...:eek: Now my A/F curve has a nice U looking signature to it. Hehe. Putting twins in this week though, so that will take care of that.

Ken R.

pcm + dyno tuning

It's not either/or. An FMU can be a useful tuning aid, but using one is only "tuning" in the crudest sense.

Rich

It's not either/or. An FMU can be a useful tuning aid, but using one is only "tuning" in the crudest sense.

Rich

That being said if you decide to go with an FMU you may consider the Vortech Super FMU (adjustable).

FWIW I ditched my sh!tty Powerdyne FMU (was only working at a 4:1 ratio when it was supposed to be 8:1) for 42# injectors and LT1 Edit. Tuning was pretty straightforward except for one thing, part throttle surge (cam surge really). It turned out to be a lean condition caused by closed loop, so I disabled closed loop and tuned part throttle via the AFR table ....no problems now.

I'm using TunerCat and dealing with the same closed loop cam surge issue. hopefully I'll get that cleared up soon.

I'm using TunerCat and dealing with the same closed loop cam surge issue. hopefully I'll get that cleared up soon.

Do a search on BLM's and max/min integrators in the computer forum, lots of discussion on it. You may be able to stick with closed loop by limiting integration. I tried lots of things and finally got fed up with it and just disabled closed loop. As long as you trim some of the fuel out of the Open Loop AFR table you will not have any problems going with open loop, I haven't anyway. I just trimmed some fuel out so I usually see mid 800mv's when cruising and low 900's for the extremely light loads (example, cruising in 4th at a steady 25 mph) as I needed more fuel to stay out of surge in those super light load areas. When I get on it the PE vs RPM table DOES kick in and I see mid 900 mv's ....so yes, the PE vs RPM table is activated even when closed loop has been disabled ...at least on my '94 it does (there are lots of arguments as to whether or not it is accessed, best thing to do is test it out for yourself. I did with extreme fueling on a test tune......I put loads of fuel in the PE vs RPM and got on it, saw .980+ mv's and rich knock so I knew for sure it was working).

Do a search on BLM's and max/min integrators in the computer forum, lots of discussion on it. You may be able to stick with closed loop by limiting integration. I tried lots of things and finally got fed up with it and just disabled closed loop. As long as you trim some of the fuel out of the Open Loop AFR table you will not have any problems going with open loop, I haven't anyway. I just trimmed some fuel out so I usually see mid 800mv's when cruising and low 900's for the extremely light loads (example, cruising in 4th at a steady 25 mph) as I needed more fuel to stay out of surge in those super light load areas. When I get on it the PE vs RPM table DOES kick in and I see mid 900 mv's ....so yes, the PE vs RPM table is activated even when closed loop has been disabled ...at least on my '94 it does (there are lots of arguments as to whether or not it is accessed, best thing to do is test it out for yourself. I did with extreme fueling on a test tune......I put loads of fuel in the PE vs RPM and got on it, saw .980+ mv's and rich knock so I knew for sure it was working).


It's funny you mention that you've disabled closed loop, because for the short term that's exactly what I've done, I do need to trim some fuel, but it sure does run better in OL. I was wondering if staying in OL, but tuned would be a problem, I'm going to play around with it some more but I think that will be my solution also.

As Rich noted, the FMU is a crude adjustment system. To insert a mechanical adjustment into a fully electronic arrangement seems retarded.

Go with the right size injectors (42#) and retune. The PCM tuners have sharpened their pencils a lot better in the last few years and their prgms are as good as you could get without your own test and tune equipment.

Another vote for PCM tuning. PCM's for less would be the direction I would reccomend. Although if you know more than me (not too hard to acheive) about the system, tuning the PCM yourself on a dyno would also be ideal. I am just lazy and have never learned, so I pay the pros to do it for me.

LT1 edit version 2.2 and Dynojet wibeband O2 sensor. Data log software and drive miles for low speed Closed loop and WOT tuning. I ditched the FMU.

Dyno tune with bigger injectors.

An FMU is like a band-aid for smaller injectors that dumps a **** ton of fuel.

Mike

Dyno tune with bigger injectors.

An FMU is like a band-aid for smaller injectors that dumps a **** ton of fuel.

Mike


Agreed. It just pinches off the return line to crudely increase pressure....hardly seems like a precise way to do things.

I'm using the MAF on the pressure side and showing no signs of it being maxed out.:)

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?

Must not be making enough power ;)

PCM here, maxing MAF out!!!

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

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?


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

Steve

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

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.:)

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. :)

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. :)

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.

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?

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.:)

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

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.;)

once you max the maf out its all a guessing game right? just have to mess with the pe tables till you get it right?

will weather and elevation cause any issues with that? will that effect when you hit peak boost, and mess with your scaling up to that?

once you max the maf out its all a guessing game right? just have to mess with the pe tables till you get it right?

will weather and elevation cause any issues with that? will that effect when you hit peak boost, and mess with your scaling up to that?

If I understand it right it's not a dramatic thing when you max it out (unless you're making huge power (650+ rwhp) because you're still getting the 471 GPS fueling (or higher if you've tweaked it some) at least (not like it's jut getting none once it's maxed). So the PE vs RPM just needs a little more from that point on to compensate. But yeah, guess with it but start out rich to be safe (like 40% more) if you're making quite a bit of power. You want low to mid 900mv's at WOT or high 11's to low 12's on a wideband.

once you max the maf out its all a guessing game right? just have to mess with the pe tables till you get it right?

will weather and elevation cause any issues with that? will that effect when you hit peak boost, and mess with your scaling up to that?

I wouldn't even think to guess. A wideband with or without a dyno is what I use to figure out what it needs to be. I surely would not go WOT just guessing if my motor will go lean or not. Way to much money to guess :eek:

I wouldn't even think to guess. A wideband with or without a dyno is what I use to figure out what it needs to be. I surely would not go WOT just guessing if my motor will go lean or not. Way to much money to guess :eek:
yeah i didnt mean plug some numbers in there then hit the track. but you are just plugging some numbers in there, making a pass with the wide band... adjusting repeat... bla bla bla

once you get it dialed in is it fine? or do you have to keep adjusting for weather?