have purchased all the burning equipment and a hypertech chip to simplify things(already had a slp) have read these proms(using tunercat)and printed out the tables to compare them.i need to add fuel form approx 2000 rpm up to compensate for the supercharger(6.5 psi@5500rpm.also think that a little more inital spark and less overall should help.have been running 65 psi fuel pressure.and no fmu.and the slp chip along with 1.5 degree boost retard per psi using the msd-btm.this setup seems to still be running lean.now i have a set of 30 lb svo's setting on the shelf that need to be installed.i'm guessing now the best thing to do is change the injecter constant to 33lb an hour and lower the fp back to approx 45psi and then see if the car will run before changing anything else.dont want to start by changing too much.this sound good or what have or would some have you done?
thanks-
pete

------------------
1990 Trans Am,350 TPI(L98),WS6suspension ,bridgestone RE71's /245/45/zr16
paxton supercharger,afr heads,edelbrock manifold, alston sfc's,msd 6AL-BTM,
8.5 superconductor wires SLP 1-3/4 headers,duel cats,3"slp exaust, lakewood LCA's,T.B.Bypass
160 degree stat,alum driveshaft,fiberglass wing, secret mods

"if you cant win fair CHEAT"

[This message has been edited by blowen90ta (edited December 31, 2000).]

 

blowen90TA,

I take it you are running the stock 22lb injectors at 65PSI with the stock chip? If so, here is what I would do: First, I would calculate the theoretical flow of the 24lb injectors at 65PSI using the appropriate formula. I would then install the 30's, burn an EPROM for 33lb injectors, and then set the fuel pressure as necessary to achieve the same flow rate. That pressure will not be 45PSI. To make it easier I'll do some calculations for you....

22lb GM injectors at 65PSI are equivalent to 26.9lb/hr GM injectors (and 25lb/hr SVO injectors). This is approximately a 22.3% change as compared to what the ECM thinks you are running.

If you install 30lb SVO injectors with a PROM constant of 33lb/hr and then set the flow rate to 45 PSI you will not have this 22.3% difference and therefore, you will be running lean in comparison to what you were running before. You have two options ....

1) Run a higher pressure from the start.
2) Understand that you will be running lean and be ready to make changes to the VE tables to compensate.

However, with all of this said, you must understand the limited scope of the 730 ECM in its stock form for supercharged applications. This ECM can only register up to 100kpa. That means that whenever you are in boost ... the ECM does not know. It just pegs you at 100kpa. This is extremely tricky. The safest bet is to go with a different ECM like the SyTy ECM. Another option is to rework the microcode to support a 2 bar MAP sensor. Yet another option is to junk the Delco ECM and go Accel DFI or Speed Pro.

If I were tuning my car with a SuperCharger I would first nail down the fueling curves for part throttle driving. Again, this is extremely tricky for anything over 100kpa. You could always bump up the pressure to around 50PSI and then realize that you will be subtracing fuel (decreasing VE) from the lower MAP / lower RPM region and then adding fuel (increasing VE) in the upper MAP / upper RPM region. This will give you more room to work. I would then use the WOT %Change to AFR table in order to adjust the AFR for WOT operation. You might find that you still don't have enough room to work in the fueling areas. At this point you could reburn a PROM with a lower injector constant and then retune the VE tables again. Very tricky and very time consuming.

Let me emphasize that I DO NOT have a supercharger and I have not tuned a car with a supercharger before. But, if I installed a supercharger on my car that is how I would start if I were to keep the 730 ECM in its stock form. However, I would probably install a SyTy ECM or a FelPro SpeedPro unit.

Tim



------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's after installing Hooker LT Headers and reducing weight.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

tim, thanks for the advice guess for right now will be sticking with the 730 even though there are other computers better suited to the combo.(just dont have the time to swap to the ty/sy setup)the car runs pretty well right now just looking to work the injecters out a little less and get the wot afr closer as my stock pump is running out of fuel pressure at anything over 70 psi.
think for now will burn a chip for the 30 lb injecters using the 33 lb constant and see if it will run.
one thing i don't get abouit your math though is that if the injecters are rated at 30 lb at 37 psi how will i be getting less fuel at 45 psi than the 22's at 65 psi?
is it because of the 33lb computer setting instead of the 30 lb the injecters are rated at?

 

Yes, that's it.

Right now your computer thinks you are running 22lb/hr injectors but you are really running 26.9lb/hr injectors (at that pressure). When you install the 30's at 45PSI with an injector constant of 33lb/hr the computer will think that you are running 33lb/hr injectors and you will be running 33lb/hr injectors (with a pressure of 45PSI).

Your best bet is to probably just start off with an injector constant of 30lb/hr instead of 33lb/hr and a pressure of 45PSI. Realize that you will definitely be rich in the lower RPMs. You will have to adjust the VE map accordingly.

With a supercharged engine you want to create as much 'room to work' as possible in the standard 20kpa-100kpa Region of the VE maps. This means that you want to be able to add fuel at 100kpa if you need it. Well, you can't add fuel if you have already maxed out your VE 100kpa region. So, what you do is lower the injector constant (or bump up pressure) and then lower your entire VE curve so that you now have more room to work in the upper RPM region. However, let me point out that this is basically fudging the VE curves. This is definitely not what you would normally do but you don't have a choice if you are going to stick with the 730 in its stock form.

Another aspect to keep in mind is that there is only so low that you can go in the VE table in the lower kpa / lower rpm region before you reach a static point. At some point the ECM will command the injectors to remain open for such a small period of time that the injectors can't be open for that period of time. Remember that the injectors take time to open and close. Once the sum of this time becomes equal to the pulse width commanded by the ECM then the injectors basically cannot open at all.

Now, I'll let you know that this is all theory. I don't know firsthand and I don't have experience with tuning supercharged engines. This is just how I would start after I did a lot of research on the web. I would recommend going to the GMECM archives and searching in there for entries that relate to supercharging in order to get more information.

Tim



------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's after installing Hooker LT Headers and reducing weight.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Tim, this might be a place where a person can use a relocated MAT to further "fudge" the ecm. In doing all my analysis of the relocated MAT, I found the ecm tended to over compensate at the higher MAP readings.

Thus, to create a VE table that would work with the relocated MAT, I had to "flatten" the VE curves. At low MAP readings, the INT readings with BLM forced to 128 were very close to 128. But as the MAP readings got higher, my INT readings got quite low. As low as 80 when I started to have MAP readings above 50 kpa.

I just thought that by using a relocated MAT, this might help in this situation. If I understand what you're saying, you can only lower the low end of the VE kpa tables so low before you hit a threshold where the PW is too low. Conversely, you can only raise the high end of the VE kpa tables to 100 (I am assuming).

Since a relocated MAT tends to add too much fuel at higher kpa (and lower temperatures), this might help "broaden" the VE table range.

It still looks like a "cludge" no matter how you look at it. Sure doesn't look like the stock 730 ecm is "supercharger" friendly.

 

For all the effort to bandaid this, you'll be farther ahead to to do some more research and go with the 749.
I do beleive Intech has BTDT. Might look him up.
You can't afford not to do this correctly.
While 7 PSI is only .5 bar, and the 2 will kinda be overkill, you can turn off the timing if for somereason you get more then you expect.
One set of blown headgaskets is alot more then a ecm.

 

thanks everyone for the info--glen i was thinking the same thing the more i read your other posts.traxton,what your saying is how i will start to get the beast running after the injecter change.and grumpy i'm shure that i'll plan on going to the 749 in a couple of years when i have more time and knowlage of what is all intaled in the swap.i'm shure that it involves more than a simple repinning and map swap and right now it's around 0 degrees outside.will be building a 30x40 garage/workshop this spring that should allow me to work on the car all next winter in 70degree comfort.
thanks'ill post results when i get i get it running
pete

 

I was tuning a mildly hopped '92 305 with a Vortech supercharger a few weeks ago. You will definately have to change the fuel pump to a larger capacity(I used AC Delco EP367) and had to install 30 lb injectors. Fill me in with more specifics and I can probably get you a good safe starting .bin. The only forgiving thing about supercharging and a 7730 processor is that you have a centrifugal supercharger. Most of the time if you are going to get it into boost, it will be racing, mapping for that doesn't require as much resolution. There is no way to cover up the fueling problems you will encounter when at a low boost high(~2500-5000) RPM, the computer fueling doesn't know you are at low boost since you are above 100kpa. The only way, mechanically, to help with this is to use a boost compensating regulator. I am attatching a picture below along with a link to another site so you can read a little more about this(so I don't have to type so much )

http://www.enteract.com/~mikew/ubb/F...ML/000012.html
There is a decent discussion about some of the stuff on the market. Never, ever use that crappy controller paxton,vortech, others use, there is very little fuel control with it. The nice thing about a true boost compensating regulator is it will give your better resolution over the fuel tables. hth's
-Carl
btw That little 305 ended up making over 380hp at the tires when we were done.


[This message has been edited by InTech (edited January 04, 2001).]

 

Goto this site and email shalin. he has bee nprogramming SC'c vettes and LT f body for some time now wit hthe stock ecm and map.
The 92-93 LT1 is very similiar with the 7730 in that they bot hare SD. the LT1 seem to have higher RPM tables 7500 fuel maps table etc.

His site is Http://www.geocities.com/blownc4/

 

intech-are you saying that i need some sort of fmu in the system regardless of the programming?i was under the assumption from my research that the 30lb svo's would be fine with a properly tuned prom.but am very interisted in what you are saying as i im only speculating at this point and your knowlage is based on experienace.i already have a 8-1 fmu and a walbro 225 lpr hp pump that i will be installing this spring.was hoping not to use the fmu as it installs another variable into the mix.but if needed can install.at this point i know that the 1.5 rockers and the stock cam are really holding this combo back but hate to pull the moter with only 26000 on it.still think that i wont invest too much more money in this setup until i see what all is involved in the 749 swap,as it still seems the best way to go.especally since when the paxton die's as everyone on this board has had happen i'll shurly be getting another but bigger supercharger.
thanks for the replys
pete

 

You don't have to use a boost compensating regulator but it is the only mechanical way I know of to help when using a 1 bar map sensor and code. The supercharged 305 I spoke of above did not have a boost compensating regulator and amazingly had pretty good drivability. Biggest problem you see is when you creep into the throttle at freeway speeds, the engine gets really rich until boost is maximized vs rpm. So I guess to answer your question, No you do not HAVE to have the regulator above, just makes for a better drivability tune.
-Carl