Originally Posted by
peanotation
that would be horrible for a daily driver. i can't cruise at anything over 80mph without my egts taking a shit all over everything because the turbo is boosting a little by then. 3000rpm is way too low.
Just because the turbo is capable of reaching full spool at 3000 rpm does not mean that it will be building boost at 3000 rpm all the time. When you are cruising at 80 mph you are only at part throttle which means two things, one, there is not enough exhaust energy at part throttle to fully spool the turbo, and two, the b.o.v. is seeing vacuum at part throttle so it is open and recirculating any pressure that is in the system.
If you have such a small turbo that it will spool down around 2000 rpm than what I posted above does not apply. With a smaller turbo it will take less exhaust energy to spool the turbo and you may see some boost at higher speeds. At that point there can be enough pressure in the intake manifold to keep the b.o.v. closed and you'll start to see boost.
Here's an example from my ES. On the highway at 80 mph, if I ease into the throttle, or if I have the cruise control on and start to go up a slight incline, you will hear the turbo spool immediatly after you give it a little more gas than it took to go 80 mph. So the turbo is not spooled, the b.o.v. is open and the car is not building any boost at 80 mph. However, if you take the car up to 90 mph it's a different story. The turbo is spooled and you are building boost. The problem this causes is that the car is building boost at such a low throttle position that even though the fmu is raising fuel pressure, the computer is not opening up injector pulse at that low of a tps signal. If your not careful the car will detonate constantly at that speed. If it was intercooled it probably wouldnt be a problem but I don't have it intercooled. Keep in mind that I have a turbo that reaches full boost at 2000 rpm. Take that up to 3000 rpm and you will not see any of these problems. (until maybe around 120 or so, but who cruises at 120?)
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