You're of course, completely right.

As soon as I posted I regretted my complete oversimplification of my answer.

Here is a good link on the operation of turbos, and will save me much typing:

http://www.1300cc.com/howto/how2/turbo.htm

 

I get about 16psi on half throttle, past 3500rpms.

 

AutoXer, The reason the WRX goes lean under PTFB is because theres a different fuel map (open loop I believe) that is used under WOT.This "open loop" map is leaner than closed loop. Its no problem if your foot is on the floor and your getting all kinds of fuel in the combustion chamber too keep things cool. So if you have a boost controller installed and you start hitting full boost at part throttle or less your ECU leans everything out thinking your at WOT, but theres not fuel getting to the engine to keep things safe. If you have an EGT guage installed you can watch temps go through the roof when all this is happening. So to answer your second question, I dunno why anyone would want PTFB situation. Also from what I'v heard the EVO ECU is set-up in a similar fashion as the WRX so I'm pretty sure it would be the same result as with the WRX.

 

Reguardless... the computer should know how much air is getting in, via the MAS, and should adjust fuel acordingly. What am I missing? I do believe you about the EGTs going high. But why do they do that?

BTW... open loop uses fuel maps based on RPM's and air flow(> 25% throttle)... Closed loop adjusts fuel acording to the O2 sensors.

 

Here you go. Right now I only have the DP on it and back to stock airbox. In 4th gear at like 55mph (3500 RPM or so) and add about 1/3 throttle and I hit 18-19 psi. My restrictor is enlarged so my max boost is around 20-21 psi. But I am getting damn close with not even half throttle.

To simplify the whole thing, in 4th the RPMs are there to build some boost with less throttle. In 5th gear at speeds of only 55 there is not enough RPM (therefore exhaust flow) to build the pressure.

 

Everytime someone talks about the open loop switch over the throttle % changes.
Does anyone really know at what point the ECU is set to change over to open loop?
Can Shiv or someone who has knowledge of the maps in the ECU tell us at where the switch is?

 

If the computer always goes into open loop control at the same throttle position, then open loop is at 25% throttle. I can post the datalogs later today to prove it.

 

AutoXer, you could be right about the 25% switchover to open loop. All i know is when I had my Subaru with an MBC installed, sometimes when cruising on the highway or some other situations I would hit full boost. Now I dunno if I was at half throttle or possibly less, but man the EGT's would start rising quik.At full throttle they would not.I assume this was due to the different fuel mixtures. Anyway, there was a big on-going discussion about it over on NASIOC and I believe Shiv from Vishnu explained it as the ECU going into open loop which means a leaner mixture reguardless of MAF readings or TPS readings. I could be wrong about that, but thats the way I understood it when it was explained. Maybe Shiv or someone else could shed better light on the subject than me.

 

SR20, i had the same expierence with my wrx. However on my GST I was hitting 20lbs at half throttle and i could see the EGTs rise through the roof, as you could on your wrx...

However, Timzcat is hitting close to full boost at partial throttle, which is excellent because that would mean the ecu is giving it enough fuel, that is if he doesnt have an mbc.

Autoxer- those logs would be most excellent! This thread is turning into a good one!

 

I may be mistaken here, but I though maximum horsepower is at 6,500 RPM? I know the torque decreases as the boost decreases so the seat of the pants feel (i.e. the force from the torque) is less, but the car is still accelerating faster due to the excess HP gains from the higher RPMs over the HP decreases from lower torque (i.e. less boost).

 

if the boost was kept up though, more torque would also be realized. If you look at some dyno graphs, hp and torque should cross at 5250 RPMs, then usually the torque tails down from there, and the hp rise.

 

Incorrect... Acceleration is directly related to TQ not HP. Thats why it feels like a rocket at 3500RPM.

 

Horsepower (which includes torque and RPM) is the more relevant measure in determing how fast a car can go:


http://vettenet.org/torquehp.html

 

My comment was clearly about torque.... and it IS correct.

Top speed is an entirely different beast, which I don't want to, or see the need to discuss. I was just clearing things up about accelerations relationship with torque.

 

You really can't have one without the other. HP is the potential to make torque. Turque is what moves your vehicle and makes it accelerate.

I like this annology: HP is how many reps you can do, torque is how much weight you can lift.