3000gt VR4 and Dodge Stealth TT Boosting 101
These cars only ready to make more HP that what it came with from the factory. The Japanese had a silent agreement to limit the factory HP numbers. those number were a little higher for the USA models but still far below what they can handle. This 6G72 engine can hold 600HP on stock internal if air fuel ratios are managed properly.
Boost is built during acceleration. The factory max is 9lbs on a 1gen and 12lbs on a 2nd gen vr4. Your engine blows out the hot waste from the combustion chamber. So to put it to good use it turns a wheel in a turbo on its way back to your tail pipe. Well that also turns wheel on the compression side of the turbo. That wheel is used to build up air pressure. It is run through the inter-coolers to cool the temperature down. Then it’s fed into your Y-pipe and into the intake plenum.
The more air and fuel you can shove into your combustion chamber the bigger the explosion will be. Thus producing more horse power! This is how you can make a V-6 have more horse power than a much larger but naturally aspirated engine. You are forcing air into the chamber at higher than atmospheric pressure. AKA forced induction. On these and most turbo cars if you add more air than what the factory presets then you can increase your horsepower even more. However your are getting close to a very disastrous situation. You see you have to add air and fuel together in the right ratios or you will not have a proper explosion.
With a boost control mod you bleed off or withhold pressure from going to your waste-gate solenoid. They open later, thus letting the turbo pressure right out the exhaust system. Or some dump straight out via their own piping. However most guys have found out the hard way, that with the stock fuel injectors you can only run about 14lbs to 15lbs of boost before the the stock 9bs dump too much hot air. Since the air/fuel ratio mix is off it detonates at the wrong time. It can detonate when the piston is on the way up. OUCH!!! There is a very good chance that when this happens that it will break your piston or a valve.
The most likely place is the piston ring landing.
So one way to safely increase boost is first to get an after market boost gauge. The factory boost gauge is very inaccurate. Then you keep an eye on the gauge at wide open throttle (WOT) and make sure it does not go above 1bar (14.7psi ) on the gauge. The best test is a third gear pull, this will produce the highest sustained boost test. I like the blitz dual turbo timer because it has a peak boost hold function. So if you miss it you can hit a button and it shows you the max boost you hit. Far more accurate than trying to watch a gauge and the road at the same time.
You should also choose to use higher octane gas to help detonation happen later. Octane lets the fuel explode at a higher temperature thus allowing more air to be shoved in before it goes boom. Also to help again predetonation. Also very bad. The pistons can get very hot and can ignite the fuel without spark.
The stock 9B turbos can only push so much air at a certain RPM. The 13g or the 15g turbos have bigger wheels on the compression side, so they can push more air at a lower rpm. However you still have to keep the fuel ratios in line. Every pound of boost is roughly 10 HP. So get a boost gauge and a boost controller and you can increase your system past factory boost and gain an additional 30 to 50 horses!