Ok guys I have search the forum and read a couple post about this topic. I just want to know Do us EVO owners have to worry about this PTFB issue or no or is this just for WRX ? ? ?
I am getting confused with all the post can someone clear this up for me thank you.

 

Also... could someone please confirm that

1.27-1.28 bar is the usual peak boost for lower gears...
and
1.32-1.39 is rare peak boost for higher gears??

Thanks,

 

you can try doing this with 4th gear very easy to make it happe.
Try going down half way in 4th I think u can hit pretty close to full boost.

 

Uh... the reason why you se the so called PTFB is because turbos dont decide how fast the go... the time the exaust from the header is pushing on it and how hard it is pushing on it is what makes a turbo spool up. What I'm trying to say is that your waste gate controls how fast the turbo spins. RPM only matters in an evo at like 2800 to 3000 rpm. thats when the exaust has enough power to spin up the turbo to 19 psi. You can prove this by watching your boost gage. See how it drops after 5000 rpm. the turbine slows down at high rpms because the waste gate opens up to limit boost to 16 psi... get it?

 

I am currently using a EBC, and I was just worrying about the part on PART throttle not giving enough fuel for 17 18 PSI of boost. So can you tell me is it safe to have 17 18 psi when only using half of the Throttle in 4th gear.

 

why wouldnt it be? What are your settings on your safc? ie 1000 rpm/2000 rpm/ 3000 rpm/ etc?

 

Hi,

I think he's referring to a lean condition when you have full boost with part throttle. There was a lot of talk about this with MBCs on NASIOC and the WRXs. My wife has a WRX and I skimmed the articles, but I never installed boost control so didn't pay much attention. In short, people experienced engine damage from PTHB.

On my car with an MBC, I do get full boost at part throttle. I basically avoid it and either go WOT or back out. I believe the problem is that stock the car doesn't run full boost at part throttle, so the maps aren't rich enough, which also may explain why part throttle "feels' faster (and may in fact be faster).

Anyway, can someone confirm that the EVO has the same problem? At part throttle doesn't the car read from the MAF? If so, can the car compensate enough?

Thanks,

FB

 

I have no SAFC yet, so do we evo owners have to worry about the PTFB or is it just WRX ? someone please confirm this before we start to hear someones engine blows.

 

If you were at full boost and part throttle as you say... you would more than likey be in a higher gear.....IE 4 or 5 and pressing down the gas to accelerate as stated in a previous post....instead of downshifting.

This may be a problem if you have your booost set to high and the car is tooo lean. This is normally where the car hits fuel cut to prevent detonation and has higher temps in the engine due to the lean conditions......

if you boost too high in these conditions yes you can blow your motor...

Set the boost to a lower setting..................get a fuel computer and an EGT.

 

The Evo goes into open loop control (using the MAF) whenever the TPS is over 25-30 percent. I don't think that PTFB can happen below like 50 percent.

When do the WRXs switch to open loop control???? Thats what you need to find out.

 

WTF are you talking about.....tps has nothing to do with full boost at part throttle...

if your doing 50mph hour in 5 gear you can maintain your speed under 25% throttle.....now start accelerrating at the like 40% throttle.....yourt turbo is gonna spool wo being over 50% throttle and if you having your boost set to high it can jump to full boost way easier than if you were going 5 mph and then mashed in the gas to 80% in 1st gear;

yes you can over boost in higher gears with only part throttle causing a lean condition in your engine.

this has nothing to do with open loop or closed loop; it has to do with the amount of exhaust gas running through your turbo.....the ability of your wastegate regulating boost pressure and the lean condition is directly realted to how you have your AFR tuned in these conditions.

this is generally called boost creep; it is not as prevelant in the evos but yes it is possible in any turbo application.

search and read it has nothing to do with wrx or evo it is inherent to turbo motors; differnet designs have different amount of creep but it is still possible.

 

Ok thanx guys I got it so basically when we are in HIGH gears dont do part throttle to accelerate either u floor it or just downshift to get the power u want. Now is 17 18 psi consider high BOOST in 4th gear with 50 percent throttle ?

 

Well youve only really got part of the story....do some more reading on dsm.org about boost creep and youll get plenty of info on this and many other related subjects.

If your car is completely stick you probably wont see this issue...and you may see it if you mod your exhaust and intake etc....

17-18 psi is not high boost in this situation as mitus engineered the car for all type of drivers and conditions so you really shouldnt worry about this unless you start to mod your car....

if you encounter this issue you will know it casue fuel cut is very apparant....and if you do you just turn the boost down and adjust your afr accordingly.

 

I have a SAFCII, so if I pick up a boost controller and just hold 19psi to redline, will I have to worry about boost creep?

 

I think from others are saying as long as u dont go past 20 psi
doesnt matter what throttle you at you should be safe. But with a SAFC leaning out the fuel then I am not sure again.