I am building a mild supercharged LT1 for my 1973 MachZ. the engine bay is custom, and the stock LT1 F body kits do not work. I have purchased a V2 head unit and am collecting other necessities for the blower setup. I have a couple questions:

Is anyone using a blower motor MAP sensor to tie into the factory PCM to allow boost retarding editing thru LT1 edit.
IE: 0V=0KPA, 5V=200KPA instead of 100 facotry and then just edit timing in the RPM vs. MAP table to get boost retard where it should be?? Whats the output on a 3800 supercharged MAP???

What kind of fuel pressure increases are needed to run stock injectors and 6psi? I see 1:1, 4:1, 8:1, 12:1 FMU's out there, what's been tried and proven?

What diameters of pulleys are stock on the 6lb. Vortech kits (crank and blower)?
Thanks for the input.

 

i dont think youll need another map sensor to try and read boost, since you have a supercharger your boost is linear with rpm you can tune it that way. im sure someone more experienced with tuning will explain how, im just going by what ive read. but id personally be interested if you could swap the map sensors and re programmed the pcm. i think with 93s its possible but the others i do not know, good luck with the project.

 

The stock PCM can't read boost can it? Just airflow...

 

No, the stock pcm cannot read boost or be reflashed to do so.

 

I have a 2 bar map sensor in mine I am testing out - I don't see any reason why you can't rescale the tables to make it work - I will know for sure in a week or so. The main downside would be a loss of resolution - but I can live with that.


Chris

 

chris b-
what MAP sensor are you using? You are following what I am talking about, you will have only half the resolution on the MAP vs. RPM table, but I don't see a ton of value in many of the 45-75 KPA tables anyway. I agree the loss in resolution should be fine.

Any thoughts on the fuel portion of the question???
thanks

 

i think racetronix was talking about this in another post. pm him and he may be able to explain it better. apparantly hes done it.

 

I picked up a 2Bar GM sensor on ebay for ~20 shipped. Figured I would give it a shot at that price.

All fueling will be handled by the maf, so shouldn't be any map related issues (on a 93 you would just need to mod the VE tables also - though the baro would read half of actual you would get funky air density values - you would probably end up compensating with the injector constant).

I wouldn't bother with trying to run on stock injectors. If you are staying high impedance just get the siemens 57's from racetronix - it will give you room to upgrade in the future, plus they idle/drive fine .

Chris

 

would this be something i should try with my 93 or am i better off with my dfi(uninstalled at the moment)?

 

Stick with the DFI.


Chris

 

Thanks for the input. Please take a moment to explain the differences in injectors. You referred to "sticking with the high impedance" injectors, what other options exist, and what are the differences? I see Bosch and Seimens, among others available, what's the difference, other than the lbs/hr ratings? Also, do are some injectors rated at different fuel pressures? Lots of questions, trying to learn quickly.
Thanks

 

Any updates on the 2 bar map sensor Chris?

 

Low impedance will open the injector much quicker than high impedance (they pull a ton more current when opening) - this gives you more precise fueling. 57lb-60lb/hr is about the biggest high-z (stock) type I have seen, though honestly after using LJ's box and some 73's - and how easy it is to tune - well, that would be my choice. I'm using the seimens 72/75's from racetronix.



Works fine. I still haven't bolted on the blower, as the car is my daily driver and between school and work I don't really have the time now for any protracted down time (fitting/fabbing for the intercooler, etc). Installed one on a friends 94Z -383/D1, ~15lbs of boost, and it worked like a charm (got rid of a MSD BTM). Need to disable a few MAP codes (the ability which to do so is included in the new version of lt1 edit) and rescale a few tables, and that's it.

Chris

 

Care to elaborate which tables and which codes to rescale?

Thanks

 

You *can* install the 2 bar MAP and program the computer to read it, but why?

Program your desired full throttle / full boost timing curve into the 100 kPa column in TunerCAT or LT1Edit. The only disadvantage of this is some lost power at 0 vacuum / 0 boost, but the lost power at ~2/3 throttle will not be missed.

Mike