i'm a heads up nitrous guy researching building a turbo street/strip car. my question would be, how much can the stock pcm be changed before you have to get something like a F.A.S.T piggy back/or whole system. the motor i would be building would make between 900 and a 1000 hp.

 

At that power level and forced induction a F.A.S.T. system or something comparable would be required.

The stock PCM can only drive high impedence injectors (the largest I believe are 55's), does not recognize boost, and the MAF sensor maxes out at around 475rwhp. Some people have used an impedence converter to run larger low impedence injectors, but the tune is then only accurate in the weather it was originally tuned for since as previously mentioned, the PCM cannot read boost or airflow at high hp levels.

A nitrous car (with a wet system) can run more horsepower with the stock PCM because it's not relying on the injectors for fuel enrichment.

 

I am pushing some pretty big power and am still using the stock PCM, admittedly with the Acceleronics Low-Z impedance converter. I see no reason that a setup like mine wouldn't be fine for a 1,000hp turbo car, unless you wanted a computer controlled wastegate or something like that.

In what way would it be a limitation?

Rich Krause

 

I think the only way you could use a factory PCM with a turbo car would be to utilize an FMU..

We all know that with turbos, boost is load dependant.

MAP vs. RPM and PE ain't going to cut it with a turbo...


At the 1000 hp level, a $1600 FAST is cheap (that's what I paid for mine).

 

You might wan to look at this thread for extra comments.

http://web.camaross.com/forums/showt...highlight=FAST

 

http://para.noid.org/~lj/

He's using a stock PCM, I believe.

 

Tune it for max load, and you'll be safe. If your only partially in it and seeing some boost chances are the MAF isn't maxed and is still adding fuel as the airflow is increased. Worse case you may run a little rich if not under full load. Most times when I'm driving past 4K rpm I'm at WOT anyway. My MAF maxes at around 4700 Rpm

Bill

 

your site is the one i have been watching and is giving me ideas. i'm out of topeka, i found your site through the MO street racing board, from a guy named "XXX". you won't happen to be going to the street machine nats would you?

 

you could just buy my motor/turbo setup

I don't have plans to go to the street machine nats, when is it?

 

it's the weekend of the 13th and 14th in springfeild mo. i saw XXX's post on your motor and i would like to have it, but i run out of cash. i have a limited 10.5 firebird, and it's eating me out of house and home. we aren't really going for the show, the plans are to compete in the race, but someone here is intrested in the car and i want out of the heads-up stuff for now. ('till money gets better) if the car gets sold, i have and I-ROC that will get either a turbo LT-1 or an D-3 procharged BBC. either way it has to make a lot of power and be on pump gas so i can go back to driving/street racing.

 

Jeff also, isn't turbocharged.

Also, Brady mentioned the FMU. Consider this patchwork primarily for mediocre boost (turbo). This I consider an amateurish approach, considering you are converting a dry intake manifold into a wet one. Anyone that gets by with the oem pcm managing a turbo, doesn't know what he is missing, by not using a turbo boost dedicated ecm, as far as good driveability and correct A/F ratio metering is concerned.

 

this is true his cars blown but his car is making a lot of boost,and i've been on his sites and his ideas do make sense. so what would the tuning differances be?

 

As stated above, there is a diff metering fuel for boost that is rpm dependant, and boost for turbocharging that is load dependant. The amount of boost is secondary here.

One can adjust fuel based on rpm, but the oem pcm can not provide turbo fuel enrichment/meter fuel, cuz it cannot recognize boost that is load related. IOW, the oem pcm cannot recognize varying levels of boost pressure.

 

Really, Someone better tell me that my driveability isn't like stock anymore then, because I haven't noticed. A MAF car will usually out perform a SD car with part throttle driveability unless one has spent many hours tuning the SD system. And I have no problems with my A/F at WOT. Tune it to whatever you want. A portable Wideband does the trick.

 

how does an FMU turn the intake into a wet one? All a FMU does is increase fuel pressure on a ratio per boost pressure, at least every FMU i have seen does it this way. Maybe you are confused with the Carrols Superfueller, which is BTW a nice peice and works well, but isn't really ideal for turbo cars, more for supercharged cars.

What are all these varying levels of boost and loads that your referring to on turbo cars? You floor it, you get max boost rather quickly and it stayes there. I routinely see boost at partial throttle, but like I said the MAF is far from maxed out and is adding fuel as the airflow increases. All the MAP sensor does in closed loop is pretty much tell what timing to run, which you can't change past 100kpa, which really isn't that big of a deal.