limitations of stock pcm for boost levels under 15psi

[firebird_1995]

im getting close to receiving my settlement for a back injury i got in an MVA. that being said i would like to begin planning for a build on my 85 monte carlo ss. the budget is $5K on powertrain. i would like to see 500 to the rear wheels through a 4l60e or possibly a t56. i plan on building my own turbo piping. the car will see zero track time so im not overly concerned at beefing up the suspension or rear end at this point. its a fair weather dd. id like to retain some fuel economy and am strongly considering building a 4.3 "baby lt1" i currently have to cut my teeth on tuning a FI lt1. my concerns are with the stock pcm. what are the limitations that some of you have seen when going FI and retaining the stock computer? any suggestions? thanks in advance

[popo8]

im procharged rather than turbo... but boost is boost... and im on the stock computer its all about having the right tuner/tuners.

[95ImpySS]

I have always heard that the main limiting factor of the stock pcm is that it cannot accurately register RPM after 7000-7200 RPM. As for boost IIRCC the PCM is reliable up to 2 bar with a 2 bar MAP.

Quick question, does your budget include the price of the turbo(s)? FWIW there is a reputable company in Sunrise FL that has been trying to sell a twin turbo kit for a 2nd gen F Body for quite some time... might be worth looking into if it fits. http://miami.craigslist.org/brw/pts/2987650112.html

Depending on what you can find a L99 could be a good and cheap starting point. They are plentiful and rarely built up. Would be neat.

[firebird_1995]

I've been looking into the "on 3 performance" line of turbos. $350 for a 76mm. I have an good l99 sitting in the garage next to 2 lt1s with bad bottom ends. I plan on re-ringing the l99, putting an lt1 cam and heads on and let the turbo do the rest of the work. This is really a sort of entry level FI build. I have read the true cost of going FI sticky but because I don't intend on trashing the car on a regular basis so I hope to prolong some of the extra costs involved. If it all goes south I should have less than a grand in the engine and turbo alone. Shouldn't be too hard to walk away from and start over with high end parts if need be. Thanks for the clarification on boost. I don't plan on spinning above 6500 so I should be good to go!

[firebird_1995]

As far as sizing the turbo goes, do you guys think I should see what the the 4.3 v6 crowd runs since the displacement is the same? Single or duals?