man_of_steel

I'm looking at buying a guys FD out of Miami. it has about 5K on rebuilt engine, compression is fine, I want to know what boost levels are acceptable. I know to look for 10/11 at around 4500, then a drop, and back up in second. what about at idle? and what if the boost ih higher or lower? like running 14 with no dropoff?

peejay

uh.....

man_of_steel

EXACTLY. This is why I'm confused. I was told something about negative something, and the fact that a boost at idle was even mentioned threw me off guard, and I was thinking that damn, maybe I have no idea whats going on. I just wanted to double check.

peejay

there's no boost at idle. boost is manifold pressure higher than atmospheric.

now... you should be concerned with manifold *vacuum* at idle (which is NOT boost) which is usually read on the same gauge. i think the factory spec is the engine needs rebuilt if idle vacuum is lower than 15 inches. of course if the car has a vacuum leak or a ported engine that's going to mess up the readings. also keep in mind that FDs don't have boost gauges, so you're goingto have to install one to check it.

2FAST7S

15 inches? whats that on a real boost gauge? what kind of boost gauge are you using metric/standard-rest of the world/american?
I have heard the norm is about 12(dont know what the measure is--inches or what) but a reall strong engine does about 18...again, vaccum is what you should read at idle.
If you are boosting 14psi sustained w/o fuel enrishment you may be leaning out the engine which you dont want!
be ready to have some extra cash for a rebuild just in case the guy you are buying the car from already damaged/didnt break it in correctly--or just flat out you may very well do that on your own.
its a cool car though! if you got the cash get it!!!!!!!!!!

maxpesce

US BOOST/VACUUM Guages (Like AUTOMETER) are calibrated in INCHES of Mercury for Vacuum and PSI for Boost.
A STOCK FD 5 spd should pull 15"-16" Vacuum (Automatic Trans cars will run 12-14") at Idle in neutral. On WOT (Check In 2nd or 3rd) the boost should peak at 10-11psi on the primary, from 3000-4500 rpm, dip to 8 psi during transition (for about 1/2 sec) to both turbos then hold 10-11psi from 4500-7000 rpm and drop slightly (but not less than 9 psi at redline this is called the 10/8/10 (stock) boost pattern
2-3 airflow mods can up this pattern to 12/10/12 and that absolutly is the Highest BOOST you should run on a stock ecu.

man_of_steel

so if this FD I'm looking at actually does push 14 psi, do I need to upgrade the ecu, get/improve the wastegate, or what?