SD2 tuning

[good2win22]

Jason...can you bump the boost up with SD2 and it'll automatically keep the AF at a predetermined value from idle right through to the traps?

In a nut shell.... No. The preset AF is based off TPS position. I believe it works like this, based on throttle position, SD2 goes to the a/f table and uses rpm and vacuum/ boost to target an AF based on a VE table using the same parameters. I do have mine set for closed loop at WOT so in theory I could bump the boost but would have to watch the a/f correction and adjust if I get outside the +- 5% rule of thumb.


If I explained that incorrectly, someone chime and in and school us all

[Scoobum]

If you add 1 pound of boost...do you have to manually change the fueling like I do?

[good2win22]

If you add 1 pound of boost...do you have to manually change the fueling like I do?

Depends on how much increase there is in the a/f correction. I don't have any passes under my belt to know how much to adjust for 1 pound much less for the 18-19 pounds I'm pushing now.


I can adjust the fuel via the laptop quickly in one single blm block or I can go into the VE tables and adjust a bunch of cells. Works either way as I understand it

[good2win22]

Anybody else have a look at the logs?

[Steve Wood]

I did not look at the logs as I trust in Brad But, you are running a closed loop system so it is going to maintain the A/F as long as the required correction is within the range of the chip programming.

Doesn't the PL output show how much fuel the chip is adding or subtracting to provided the requested A/F number?  If so, as long as the correction is not getting to the edge of its range, then I don't see anything to be concerned about.

As far as the actual A/F number that you program in, I would start with 10.6 and leave it there until you have achieved the boost you want to run, then you can start trying a little leaner to see if the car gets "crisper" and goes quicker.  As I have said before, I don't always that leaner is meaner but testing tells the story.  If spraying alky, my main concern would be to monitor it to be sure it is working properly each time as its function is probably more critical than the actual A/F number in my experience.

Your larger challenge may be to learn how to drive the car to get it to perform to its optimum.  I think that is harder than tuning.

[Scoobum]

I was waiting for Steve to step in for help with SD2...cuz I don't know shit about it. You're a smart guy Jason...and with Steve's help and the reading you do...you'll do just fine.

Steve hit a homerun with his last sentence. You gotta get out and practice. When I decided to bracket race the car a few years back, I had to run Sportsman class...which is 1/8th mile at my track. It forced me to learn how to launch the car...as I didn't have a clue running 1/4 mile. I was 'walking' around cars to win. Low gear tuning and setting the suspension is what gets these cars off the line...along with slicks and the correct tire pressure.

Forget trying to lean high gear out at 19 PSI...as it won't gain you much. Boost...is God. I keep saying...put the boost to it...and give it enuf high gear fuel so it won't hurt itself. Bump the boost 1 pound at a time until you hit 23 PSI...and go by Steves AF recommendation . If your fuel and alky system is up to snuff...you can run all day carefree.

Suspension. Women squat...cars don't. Not my quote...think it was Chuck Leeper. I had Dan Keller video my car from the drivers rear quarter. What I saw was this. The car was bottoming on launch...and then jumping up...unloading the rear tires. I had 90/10's up front and 50/50's out back...Lakewoo ds. I grabbed a pair of QA1 SINGLE adjustable rears...number 4 setting works best on MY car.

9 inch slicks-Try 12.4 PSI...and go from there.

Low gear timing. I run a crapload. You and I have talked on the phone...so you know what I run.

[TexasT]

I looked at em. I'm not what I'd think of as a guru or anything but I do have some questions.

In the high gear one the tps never gets about 4.34v.
 Im not sure if this is a problem or maybe you have a floor mat in there and the pedal never gets to the floor. Might be nothing as the car accelerates well.

Also in the frames starting in the 460 range the afr falls into the 10 range and drops to the 10.1x range at the frame 470 and then rebounds back up. I guess this is where the fuel rail empties a bit and the pump catches up and gets the rail full again.


I didn't get to see any shifts. I guess you got that governor situated?
I have to agree the 19* of timing is conservative and it pulls good with it. And you get to drive it more without wrenching haha.


On the idle clip the o2 sure fluctuates a lot but I think that is because it isn't warmed up yet.


It is all good info to me. I'm just trying to learn. I got a nasty crack in the pass header I need to swap out.
Thanks for sharing.

[Scoobum]

Just texting with Jason about AF for that chip. It's suppose to stay within plus or minus .3. His WOT...or as close as he got is from frame 483 to 542. AF is between 10.5 and 10.83...so he's within the operating window.

[Steve Wood]

Suspension. Women squat...cars don't. Not my quote...think it was Chuck Leeper. I had Dan Keller video my car from the drivers rear quarter. What I saw was this. The car was bottoming on launch...and then jumping up...unloading the rear tires. I had 90/10's up front and 50/50's out back...Lakewoo ds. I grabbed a pair of QA1 SINGLE adjustable rears...number 4 setting works best on MY car.

LOL, I like that, Brad!

While a car is sitting down in the rear, good cars are moving down the track. You do not want super soft springs or shocks on the rear...you want just enough compliance so that the tires stay connected to the track surface to prevent the tires from loading/unloading.

Dialing in the suspension is very important as races are won and lost in the first 60' with competitive cars.  Remember that one tenth in the 60" time is usually about two tenths at the finish line on a ten second car.  That's about 20 free hp.

We know the instant center on G-Bodies is not great.  I think you bought the upper control arm relocation mod.  Spend some time playing with the IC and then leave it alone.  Don't do anything radical for a car if you are driving it on the street.  Remember that radical moves to make the car hook has the opposite effect when panic stopping. 

I don't like air bags very much, but one on the passenger side can help you make the car launch straight but it's use should be judicious.  If you have two equal stripes when you launch, leave it alone.

Educate your right foot in launching.

One last trip to spraying alky.  It can cover up a lot of sins when it is working but it may also cover up why your car is not going like it should be going.  Makes it even more important to monitor fuel pressure

[Steve Wood]

Just texting with Jason about AF for that chip. It's suppose to stay within plus or minus .3. His WOT...or as close as he got is from frame 483 to 542. AF is between 10.5 and 10.83...so he's within the operating window.

I would not touch the A/F then

[Scoobum]

Steve, I have a question. Why does the AF not stay bang on the target AF?

[Steve Wood]

I suspect the "coarseness" of the ecm's sample rate and memory size does not leave a lot of room for extreme precision.  Chip does not give him room to improve the calculation precision.  The FAST guys would argue something like that, but their results on ten second cars does not show the actual benefit that they talk about

It's only an 8 bit computer which is archaic, but it works

[Scoobum]

Thanks...was always curious. I look at countless files on the other board and the AF never seems to stay bang on.

[Steve Wood]

Brad, have you ever noticed that some of the smartest people we know never seem to go fast?

they get so hung up with theory that they ignore what works.

[good2win22]

Thanks for the replies fella's. Practice, repetition at the track is something I don't have.  That will be my biggest challenge for sure. Different car than my white t but I have the suspension set up very similiar. What I didn't do to this car is lower it an inch and when playing with the numbers, I found I could get the IC closer to the CG by leaving it at its stock ride height.  This car is about 40 pounds lighter and it may be more than that since I removed the front sway bar along with a few other lightening mods. No bags, Bilstiens with a hellwig bar on the rear with 28x9 radial slicks.


I've done a pretty good shake down of all systems this weekend. All appears to be operational but we know how that can take a turn.


As for turning up the boost, I believe I'm going to learn to drive it, launch it, stop it and keep it between the ditches. It's already a handful at this power setting.


Rich, TPS has to be above 4.2 but no higher than 4.6 according to Eric's instructions.
Also, I'm still working the tune and believe I have the acceleration enrichment to high causing the rich spike. I also think it's causing a misfire and giving me a false lean spike as well. Which is what I think the little bit of KR was on the log. Shift points are up to snuff at 5500-5600. That only took dropping the pan 4 times. I now call tranny fluid the red rain.  Let me say this, depending on your pump pressure, the weight of the governor will be different for every tranny for a specific shift point.


I'll start a thread for the trip to BG. Don't be surprised if I don't post a lot till I get back. 3 dedicated days at a track.  Going to take advantage of it