Patrick G

iTrader: (14)

I know this is a huge debate among LT1 tuners, but it seems that when properly tuned, a speed density approach custom tailored to your own particular combination would give the best results. Stock Eliminators run this way and claim the VE approach is very good at adjusting for changes in air density (density altitude).

GM cars shipped to the middle east lack MAFs and O2 sensors. They can run on full leaded gas if they want. Seems to me, that so many of our tuning problems arise from faulty/finicky O2 sensors and picky Mass Air Sensors. By taking these out of the loop (pardon the pun) it seems like we would have much more consistency, better fuel economy, cleaner idle, and more power. Am I nuts?

Godspeed

Not at all, I would agree with your assessment of speed density. The main reason GM uses narrow band O2's in the US is to make the cars pollute as little as possible. The O2's used in part throttle operation are designed to read the ideal 14.7:1 stoich AFR. The PCM reads the O2's and adjusts accordingly to make the car run as efficient as possible. During WOT operation they are not used by the PCM, we simply monitor them with Autotap or some other tool to get a vague idea of how the car is running. Quite a far cry from a true wide band O2.

[ February 13, 2002: Message edited by: Godspeed ]</p>

RyanJ

id switch over in a heart beat if i had real access (monitarily) to tuning and whatnot. now, its a moot point for me, im slow, but im speaking as one of the faster guys around here.

Ryan

ChrisB

Are you positive Gulf Spec cars don't use a MAF sensor? I was under the impression that they just lacked O2 loop feedback/control?

I personally would stick with the MAF setup until you reaached it's limits. From a pure power perspective speed density isn't very difficult to tune, but from a drivability setup SD is much more involved to get up to spec. You really need to have a logging wideband in the car with you as you drive around (or I would want one).

FWIW if you log MAF, MAP, Temp, RPM etc. you can make a go at calculating the specific VE tables for your specific setup. If you wanted to run speed density this is what I would do. It would probably be an iterative process.

On the LTx based vehicles the VE map is also a little different from what you would normally consider VE - if someone who has Ls1 edit could look at one of your VE maps (if it's there) you can check and see if the VE peaks near torque (like you would normally expect it to) or keeps going ( like it does on LT1).

I also seem to remember getting the LSx based engines to run in SD mode was not an easy task?

Chris

Speartech

iTrader: (14)

I've used the Gulf States export cals before, and the MAF is used in these. I used to set up LS1 street rods that way. It was a great cal to get rid of the cats, EGR, AIR pump, etc., and not get a check engine light. PLUS, with the 98 PCM, you could add the O2's and it would see them and go closed loop! Pretty slick <img src="gr_grin.gif" border="0">

Terry Burger

iTrader: (4)

If you have LS1 edit its not hard to do, and for those serious about every last HP it can be a good way to go. The reality of the situation is that you probably won't pick up any power with it, and you will lose a lot of "drivability", especially in a highly modified motor.

I've done it both ways in LT1 land, and I always prefer the MAF in NA applications.

ChrisB

Is it really an option to go speed density in LS1 Edit? Again, I was under the impression that the LS1 was not very easy to get to run in SD mode, as it was a much more MAF oriented program than some of the LT1 OBDI car's?


Chris