A buddy of mine is ready to install a 7lbs. blower on his 93 F-car.

He doesn't want to use a FMU and it seems like the stock map sensor would pose a big problem in driveablitly, consistancy becasue the car would have no idea what the difference in 1atm and 7lbs of boost would be.

I'm going to attempt to move the VE tables accordingly and scale down 50%. also scale down the injector constant by 50%. I'll just take a wild guess at what should be above 1atm in my VE tables and use datamaster logs to fine tune later.

anthor benifit of being able to use a 2bar sensor would be to eliminate the timing retard system that comes with the sc kit. IF i can cut the spark tables accordingly than we can also start backing off timing above 1atm.

I will have to go threw everything and make sure that nothing else is dependant on MAP referance will cause a prob. (EGR, TCC, ???)

has anyone tried this or am i wasting my time. It sounds like in theroy it would work but who knows right?

 

also does anyone have a reference chart as to see what voltage a 2 bar sensor would read at different vaccums/pressures?

 

I seem to recall that on the diy-efi site that there was a chart for 1, 2 & 3 bar maps (GM style). I think that they are in the incoming ftp directory. ftp://ftp.diy-efi.org/incoming/


BW

 

100 kpa 2 bar is 2.2 volts conversly this woul be 40-45 kpa in the code

 

Interesting idea.

The thing with going supercharged is having enough fuel around to do what you want to, and then removing as mush timing as possible when in boost.

While a normal engine is all done at 100 K/Pa, a S/C engine is just waking up. There is a huge jump in engine VE as you go to 1 PSI. In that one little moment, the engine goes from having to suck air into the cylinder, to it being FORCED in.

The other thing is you really want to add a little fuel as a function of time in PE with a blower. Your BSFC drops as the chamber get hot and more fuel will help ALOT (well at least in some cars).

 

I seem to recall discussing this with someone some time ago & there are other issues. I dont recall them right off of the top of my head.

of course you only get 1/2 the resolution that you had with the 1 bar map, & anything that uses MAP is going to have to be re-scaled. I suppose you could print out the maps & scale them down for the 0-1 bar (0-50 KPA, on map) area & then plug them back in. But I dont know where you would start with the 1-2 bar (50-100 KPA, on map).

as grumpy said, you are going to have to be carefull with timing. I would imagine that you are going to want to re-scall all your PE & AE stuff to reflect the new MAP, so that it adds more Fuel sooner.

with just about everything referenced to the MAP (or refereneced to something that is refereneced to the MAP), there are a lot of things to consider.

I would be interested in knowing how this works out for you, keep us up on it.

BW

 

okay guys, We are going to go ahead an try it. I'll let you guys know how it works out.

Anthor thing is that Tunercat is a wonderful program but i don't believe it lets you touch on or even see some tables. So the best i can do is modify everthing i see and try it out.

I plan on cutting my spark tables in half using a conservative table and back off quick after 50kpa (or actual 100kpa)

By the way the car is a 93 F- Car with no FMU and stock injectors. Injector duty count hit 101.4 the other day so we are going to at least put larger injectors in.

 

The TunerCat Definition File Editor will allow you to add any table you want. So, it CAN be used to edit all the MAP tables ... you just need to add them into the definition file (which means that you have to know where they are, etc.).

Tim

 

i know.. anthor problem.

There are not alot of information on this particular pcm.

$DA3-2

 

im gonna assume that the tb is located ahean of the blower. providing the vacum at WOT is lower than it is at idle and there is no radical swining in the vaucm reading i wouod go with a one bar mpa refrecne to the space between the tb and the blower. but this again assumes that you have less vaum at WOT than at idle and that there is no larger restriction to drive the vacum readings up.also you could keep yr map resolution and aviod having to rescale it. would help with p/t cruise.

woudl you mind giving me the vacum reading at all throttle and load postions in and out of boost ?? lets see if it could work would save a ton of trouble.

 

Ah, I thought you were going to be working on the code in addition to what you said.

If Not then you have some real problems.

The ecm looks at the MAP at Key ON to see what the Baro pressure is, and there is probably a subroutine for when you first go to WOT, it does a baro recalculation.

JUST cutting the tables in 1/2, I doubt will work.

93, Optispark?.
If so then you might get to use a 8051 with a MAF and be OK.
If distributor, then a 749 from a Syclone /Quad 4 would be an answer.

 

What does the baro calc do though.... Predict or guess at air density at wide open.

Its going to read about 50kpa before the car starts and auto reseted to the highest pressure it can. The only problem i see from that is maybe some sort of trouble code like map high map low and possibly the car driving a little funny until max kpa is set the same as when the car was tuned.

am i making any sence here?

I don't know if only seeing 50kpa is going to trip out the computer or anything. maybe GM designed the programming flexable enough to work at 70,000 feet?? hehe

 

i gave you a great option i think you should focus on using the 1 bar in a vacum mode behind the TB but in front of the blower. this will save you mucho hasles. jst make sure the TB is bigg enough to aviod restrition.also it should help you aviod having to completely redo the ve tables.

 

wouldn't that almost make the Map/ sensor/ve tables work backwards?

There would be no vaccum at idle and lots at wide open.

 

Heres another question......say i were to put a 2 bar map on a 730, would thier need to be a code change or would it just be like having half the resolution (aka 50kpa readign from the 2 bar map is 100kpa on the 1 bar map) and tuen the ve tables accordingly?

 

no yr blower is always turning suking air. as stated i would take vacum readings and see where it goes. its not a guarenteed thing but i see that it might work provided that the tb doenst restrict the airflow to the blower. like a 1000cfm tb. a stock one will for sure pull alot of vacum. if the vacum reading do go up with rpm yr gonna need to go with 2 bar. but this is a horriable option with yr ecm becuase so many things depend on the map for proper calcutlation.

 

If you really want to run a 2 BAR MAP on a 730 you may want to look into running the $58 (SyTy) code. Or swap directly to a 749 ECM with the $58 code. Do a search on the diy-efi.org site look for 749 inna 730. BTW I am running a 749 with my TPI/Eaton supercharger.

 

That would be a nice option but i'm using this on a 93 F-car. The code is a little bit different. the computers are definately different


I've often thought about switching though just to have more resources

 

so do a vacum check and see where yr at. switching to the 1227749 is a great idea for boost.

 

Saturn5-With the 749; does it still run the egr, charcoal can, tcc, smog divert. valves etc???? Thanks!

 

It will run the EGR and the TCC, but as far as I know neither the Sunbird or Syclone have the charcoal can or a.i.r. valves. I'm sure this is because the $58 code was developed for a turbo application, and the backpressure in the manifold could backfeed into the air valves and canister. This isn't a problem for me since Ohio just has a sniffer test, but you CA guys might have a problem. But I'm sure that you could sneak by, leaving the a.i.r valves and canistor intact, but non functionable. cheers, Bob