Mass Air versus Speed Density

[LNorton]

I have been trying to find more consistency in the car recently. The thing is deadly 60' and deadly fron 330' to 1/8. But between there it will move around 4 or so.

I feel like I may be able to get a better handle on the tuning if I change and go to Speed Density. Just curious to know what you guys have to say for pros and cons of each way to tune.

Not even sure how many guys in stock with EFI are tuning in Mass Air.

[Rob Petrie E395]

I run a mass air sensor on a 95 lt1 bracket car. I took my car down to Ed Wright in Dec and he tuned it on his chassis dyno. I was fighting a inconsistant car as well. The tuning is the only thing I changed over the winter. So far out of 5 races this yearI have been down to 4 or less cars in every race, compared to last year where I went more than 4 rounds in a race 3 times the whole year due to not being able to get a handle on consistancy. The car now runs dead on the dial in and whatever the weather station says is what it runs every time. I highly recommend Ed he is the most knoledgeable person I have met when it comes to fuel injected GM engines.

[Ed Wright]

Lee, your car won't be on bit more consistent in Speed Density mode. It seems most of the kids on internet EFI tuning forums seem to think it only measures cfm. It helps correct for air density changes, it actually measures the air's mass. If it is not an air flow restriction, you would be better off keeping it. If you remove it you will be a while working on the correction tables the PCM relies more on in Speed Density mode every time the weather changes. Those tables don't carry as much weight when the MAF is used.

Rob, I may need to put you in mine. My lights are killing me this year. I may be getting too old.

[LNorton]

The main deal is that sometimes this thing seems to have a mind of its own.

I have been looking at Simple Digital Systems (SDS) and MegaSquirt. The factory PCM just has way too many variables that I can not get to with HP Tuners. Have also talked to a lot of guys running the stock PCM and none of us can find a solution to turn the thing past 6400. All of our factory tables end there, and no matter what we try it will just flat line.

I know that Speed Density wont exactly make the car more consistent, but from a tuning perspective will it be easier to deal with than Mass Air?

Also, have you guys dealt with stock PCMs?

[LNorton]

Originally Posted by Ed Wright

If it is not an air flow restriction, you would be better off keeping it.

It actually is a big air flow restriction. I will have to call and ask, but the original throttle body for 02 is an electronic throttle body. If I am allowed to make some linkage on it I can have a ton more flow. The linkage TB has a big bar up the center that is holding it back a ton.

[Rob Petrie E395]

Originally Posted by LNorton

Also, have you guys dealt with stock PCMs?

Yes my car has the stock pcm in it. it is the same one that it rolled off the showroom floor with. I will be 100% honest with you, I gave up trying to tune my car. I now just send it to ED when I make a change in the engine and need the pcm worked on. A while back I had been pulling my hair out trying to get faster/ more consistant, it did not matter what I tried in tuning the PCM I could not get there. Sombody suggested letting Ed tune it by mail so I got another pcm and sent it to him. To make a long story short he picked up the car 3/10 over the best I could do with a MAIL ORDER tune up. I have heard there are some limitations on what you can do in the higher RPM tables but I do not know exactly what they are. I also have thought about going aftermarket with a Holley or FAST XFI system but the car is so damn consistant and the driver has finally started to act right that I am afraid to change anything.

[Ed Wright]

Originally Posted by LNorton

The main deal is that sometimes this thing seems to have a mind of its own.

I have been looking at Simple Digital Systems (SDS) and MegaSquirt. The factory PCM just has way too many variables that I can not get to with HP Tuners. Have also talked to a lot of guys running the stock PCM and none of us can find a solution to turn the thing past 6400. All of our factory tables end there, and no matter what we try it will just flat line.

I know that Speed Density wont exactly make the car more consistent, but from a tuning perspective will it be easier to deal with than Mass Air?

Also, have you guys dealt with stock PCMs?

If you change systems, I would (and do) use FAST myself. Holley is very popular, but I'm not crazy about it. Big Stuff3 is pretty popular, but I haven't worked with it as much as the FAST. Sems to be a very good system. The aftermarlet systems I have dealt with don't use a MAF. I tune GM vehicles all day, every day, with factory computers. That's how I make my living. Most GM PCMs (computers) will run past the RPM for last row in the tables, but you can't make tuning changes past that. The factory LT1 boxes' tables extend past 7000, but the injector drivers give up there. It sounds like the rev limiter when you hit that point. The '96/2000 Vortec truck (old body style) boxes won't run past 5500 or so, even though the tables go higher.

Good luck, Ed