Turning up the boost but how high????

[KiwiMR2]

Well I am just about to turn up the boost on my GT MR2 (J-spec), the problem I have is that on another board that has VERY experienced members have recomended NOT to go any higher thans about 13 psi. I know that it is very common to run 15 psi with minor mods and people have been doing so with little or no probs. I have done my exhaust, bov, an air filter mod, and my clutch. Why is there so many different opinions and can someone give me some ideas and opinions of what to do!!

Please help!!

Cheers
KiwiMR2

[Polygon]

Hmm, that is a fine question. I am running 15psi but I have a renforced crank and I can run over 20psi on my engine the way it is.

[YogsVR4]

You dont want to turn the boost higher then your fuel system can handle. If you have stock injectors, 13psi sounds about right.

[KiwiMR2]

Yeah I think that will be my final chioce, 13 psi!

Although a lot of people get away with 15 all the time, I'll keep it a bit lower! the cars done a healthy 146,000 km's so I shouldn't push it to hard!!

Cheers
KiwiMR2

p.s I take it your name i.e VR4, is refering to the Mitsi GTO Twin turbo, not the Galant VR4?

[The Bartender]

Reliability is an issue. The more boost, the more strain you put on the engine, the more likely things are to break. This doesn't mean that something will break a week from now. But bumping the boost from 13 psi to 15 psi might cause something to break in 10,000 miles instead of breaking in 40,000 miles. Most of the people who are running higher boost pressures have either beefed up the engine or aren't as concerned about breaking something because they will just replace the engine at that point. (I know at least 2 drag racers who ran high boost levels just to give themselves an excuse to replace engines.)

The Buick GN's ran about 15 psi at max boost stock, but I've seen them handle over 20, although not for long periods of time before something in the engine, normally rods or crank, let go.

The current supercharged 3800 V6 only runs 6 lbs. of boost, so many owners have increased the boost on these by a few pounds with no noticeable harm to the engine. (The 3800 is pretty stout, though)

[MaxBoost1990]

you shold get an air fuel guage first, before doing any boost increases. Then crank away, untill you start getting lean. As long as the guage satays in the green your safe. I know my Daytona runs 12psi stock, but I can crank it to 15 before I start to lean out. Keep in mind that if you do lean out expect a thourough rebuild of your motor.

Max

[KiwiMR2]

Well it's done I have installed my fuel cut, boostvavle, and pod filter and am now running 0.9 kg/cm. Basicly an increase of about 5-6 psi over stock boost. Stock is 7 psi and now I am hitting 12.7. I think Im pretty much safe now, cars runnig great and Im getting no boost spike.

cheers
KiwiMR2