mn_vette

Hi guys, I running a forced induction system right now and it uses a Vortech FMU to increase fuel pressure to compensate for boost. My question is can I program my '93 LT1 computer to do the compensation by reading my MAP sensor??? I've got a '93 so there is no MAF it's speed density. I would think this is possible, but I've never messed with my ECM programming before. Thanks.

dgoodhue

The problem is your 1 bar MAP sensor doesn't read boost it only reads vacuum. GM makes sensor to read 14.7psi and 29.4psi off boost but it would take a lot of recalibration to make it work on your ECM (not for a novice), a MAF system is much easier in that respect, because it is reading air flow not pressure. You could convert to a 749 ECM (GM's Syclone/Typhoon/Turbo Sunbird ECM), again this isn't for a novice.

Now that I have discouraged :D ... You could still program your stock ECM and see some gains, I am not familliar with the 92/93, but I imagine you could add or remove fuel under WOT at rpm intervals to fine tune your fuel curve (still with the FMU providing most of the fuel enrichment) as well as you spark advance table (timing). You can fine tune part throttle drivability with a custom program, change the fan temps, Torque Converter lock up, etc.

mn_vette

Actually I was going to have Doug Rippie Motorsports do my dyno tuning. I've herd bad things happening with FMU's on high HP applications. It's something I want to get away from without dumping huge dollars into an aftermarket ECU setup. But if it is possible, I'll have to ask them if they can do it I guess.

I thought about switching over to a cyclone computer, but the wiring harneses are way different, I think I might be better off trying to steal the program off of it and putting it onto my computer. Would something like that be possible???


[Modified by mn_vette, 3:27 PM 2/28/2003]

JoBy

SATURN5 on the thirdgen forum just verified that the 730 ECM ( Camaro non Weatherproof version of the 727 ) works with the 749 syclone/typhoon ECM calibration. You need to replace the MAP sensor with a 2-bar unit.
http://www.thirdgen.org/techbb2/show...hreadid=164704

Internally all these three ECM's are almost identical. The 749 has a different injector driver for the syclone/typhoon low impedance injectors but as long as you keep the stock Corvette injector type you should be fine.

You MIGHT have to rewire some cables in the ECM harness but SATURN5 can probably provide you with more information about that. ( The 749 calibration might use a few inputs/outputs for different things than the Corvette )

The calibration will be way off for the Corvette but it is a starting point for a boosted MAP application.

AJR

I don't know of anyone who has interfaced the older ECMs to the LT1's Optispark distributor. As far as changing the all of the tables to support a 2 or 3 bar Map sensor, it involves major surgery to the 68HC11 code, as I have contemplated the same changes for similar reasons. The FMU is not a great device since its output is not really linear. I think it works fine for a basic stock motor that has been boosted to 6-8 lbs, but as your horsepower increases, more precise fuel control is a must IMHO. The Carroll Supercharging Super Fueler might be something to look at.

JoBy

If I understand what SATURN5 is saying you can use the stock 727 ECM with the 749 ECM calibration and a 2-bar map sensor for a boosted application. The stock ECM will stay in the car so the Optispark is probably not an issue.

dgoodhue

But if your using the 749 code, your going to be using the 749 source code, so I would imagine that the corvette only function that are tied to the ECM (for instance mpg calculation) would not be in the 749 code.

I don't know how the optispark is handled never looked in to it, is it directly control by the ECM? If it is you would need add the source code to control this.