You might want to try the recent "V4" Boost Control thread.

Looks like he has it working based on the logs posted there.

Obviously the ECU controls boost as one of it's designed functions. It has a map (or maps?) containing wastegate duty cycles to achieve boost targets. Modifying the targets in this map to raise boost is functionally the same as editing fuel and ignition maps.

The only real problem that I'm aware of comes in the fact that the stock system of vacuum hoses and restrictor pill causes the wastgate duty cycles to be maxxed out (100% duty cycle) at a pretty low peak boost (no idea what it is in the 9, maybe 20-21psi??). So somehow the restrictor pill or hoses need to be changed such that the same boost is made at a lower wastegate duty cycle setting in the ECU in order to then be able to raise the boost to where we want it.

At least that's how I understand it, which could be totally off base

So, as long as he has the proper amount of restriction figured out (not trying to trivialize this ... I'm sure it takes time to get right) , editing the map via the flash to set desired boost should work just fine.

Up to a point, since the stock pressure sensor will max out at some level of boost and send the max voltage to the ECU, above which point you will no longer be able to control boost ... again I have no clue what that is on the Evo. At that point, you need MBC/EBC/piggyback/stand-alone ....

could be wrong on that too ... just feeling wordy

 

D'oh. I'm slow. I bet he's a faster driver too

 

I think what Al has in regards of controlling the boost via the ECU is great. I'm sure it holds boost better with an MBC in place, but without one it does a superb job as well and I'm very pleased with it.

 

Awesome, thanks. This is still a very interesting thread.

I just have to say the amount of expertise on this site continues to impress me. I'm coming over from ClubWRX.net, and it doesn't even approach the amount of knowledge on this site. Also, what sets this site apart is the fact that vendors/techs post regularly over here so we get an insight into their thought processes and decision-making. I love it.

 

Just to clear that up a little... boost is not controlled by wastegate duty cycle. Duty cycle is usually refered to when talking about something that is designed to either be on or off, such as a solenoid valve... or something that's being used in an on-off mode. The boost control solenoid is turned on and off at some frequency(I don't know that frequency). The duty cycle refers to how long the solenoid is on(open) during one cycle. Pnumatically(sp) this results in variable flow dependant on duty cycle and pressure differential across the solenoid valve.

Said variable flow bleeds off pressure from the wastegate actuator, thus affecting boost. It get complicated when you throw in restrictor pills and pressure on the wastegate itself.


As far as I know the ECU doesn't control pressure directly. It "calculates" pressure from RPM and MAF. Basically it knows what flows to it should have at various RPM points.

Feel free to correct me if I am in error.


Robbie Nelson - Spreading Evo facts

 

Cool, I was hoping someone would clarify if I said anything inaccurate. Thanks.



So there's no MAP sensor? I know in the Suby system (doesn't necessarily mean anything for Mitsu) there is still a MAP sensor that the ECU uses to regulate boost, even though airflow for fueling is calculated from the MAF, RPM, and temp, etc. Said MAP sensor maxes out somewhere around 24 psi (forget exactly where) and beyond that, you need some other means of boost control ...

 

Al,
can't wait to get you out here to the great state of Hawaii!!
Anyway, in preparation for your arrival, I'm trying to get some last minute things together since there is no telling when you will be back out our way.
Correct me if I'm wrong anywhere along the way, but what I've read/learned about the IX and tuning it so far is:
- Stock fuel pump is sufficient if the car is under 400 whp, over that...upgrade it
- You now have the v4 boost hose figured out, but if warranty concerns are not an issue...go for the MBC
Can you talk a little about the tune you just did on the 2.3l w/cam. I know you have posted up quite extensively about the car, but no too much has been said about the pros of upgrading the cam or just keeping the stock in place. I remember not too long ago a IX with TBE on race gas put down similar numbers as far as whp. As far as the cam goes, I'm looking at JUN (272 or 264) or HKS 272 and maybe a adjustable gear for the the new cam too...any opinions?
Thanks for the time

 

Aloha, Evo:

1) Right
2) Right
3) You need to wait until cams are released. No testing has been done on just the single cam with a regular IX, and no set of cams has been released by any manufacturer. Be patient, although I know you don't have the luxury of getting Al out to you very often.

 

You may want to wait for the WORKS cam that is coming out soon. It will be close to the 272 but much better for the street, from talking to the guys in Cali., and putting out serious power...

Just my $0.02....