Boost creep...

The boost on my minivan will shoot up pretty high....to cutout if i let it (over 17psi sometimes). I was told this is common for the mitsu turbo. After I get the diode in there (to elimninate the cutout) will it stay that high or will it come back down? More of a spike?

[macncheese]

the diode just tricks the computer into not seeing the boost. it doesn't modify the boost at all. get a grainger!!!
tony

I understand what the diode does...... my question is more about the boost.

As it creeps up, will it stay high? Or does it spike up, then drop back down? Right now, because I don't have a cut out eliminator (diode), I don't know.

[iTurbo]

I think it will just creep higher and higher. I have 3" exhaust on my Shadow with the Mitsu turbocharger. Even with full manifold reference going to the wastegate, I get an instant 5-6 psi and it creeps all the way to cutout after 3000 RPM. I have to shift before I hit overboost! Basically, you need a turbo with a bigger wastegate.

I used to have a Garrett T2 on the Shadow and had no problem at all controlling boost. The stock Mitsu I have on there now is just temporary while the Garrett gets rebuilt.

[LancerShelby]

Quote:

Originally posted by joffficer I understand what the diode does...... my question is more about the boost. As it creeps up, will it stay high? Or does it spike up, then drop back down? Right now, because I don't have a cut out eliminator (diode), I don't know.

Are you running a grainger?

No grainger valve yet. I'll be installing a diode first (to get rid of the cut out). The work on controlling the boost.

[iTurbo]

A grainger valve will do nothing for your boost creep.

As it creeps up, will it stay high? Or does it spike up, then drop back down?


This is the question I wanted an answer for..... I'm not asking about the diode, grainger....tea in China, ect...

iturbo.... you've come the closest Thanks!

[TurboMinivan]

iTurbo was right: a grainger will do nothing to eliminate or control boost creep. Why not? It has to do with the nature of boost creep itself.

By definition, boost creep is the phenomenon wherein your observed boost level begins to rise above the target setting. It typically only happens at higher RPM (exact point varies depending on which gear you're in); once it starts it tends to rise slowly yet constantly until you let off the throttle. Why? Because the wastegate is not able to physically pass enough exhaust energy to hold the target boost level. As a result, the 'extra' energy going through the turbine raises your boost level.

A grainger valve (or any boost controller for that matter) operates by sending a specific amount of air pressure to the actuator. At your target boost level, pressure is applied and the wastegate opens... but if this opening cannot divert enough energy, too bad: you'll have boost creep.

How do you fix boost creep? There are a few ways:

1) port out the wastegate passage
2) go to a more restrictive exhaust
3) upgrade your turbo to one with a better passage
4) install a proper external wastegate

Hope this sheds more light on the subject.

Sounds good to me! I'll try 3&4 first.

[unclejemima]

1) port out the wastegate passage
2) go to a more restrictive exhaust
3) upgrade your turbo to one with a better passage
4) install a proper external wastegate
how would you go about porting out the wastegate passage? i have a 1991 daytona shelby, and only recently has boost creep been a problem. I figure if i get a brand new TEO4H with and brand new wastegate, i should be back to holding 12psi. Is it worth trying or should i just get a differnt type of turbo altoether like a super 60 or t3/t4 hybrid? I just want to elimitate the **** boost creep, its sooooooooo agrivating!!!
thanks guys

Quote:

Originally posted by joffficer The boost on my minivan will shoot up pretty high....to cutout if i let it (over 17psi sometimes). I was told this is common for the mitsu turbo. After I get the diode in there (to elimninate the cutout) will it stay that high or will it come back down? More of a spike?

Yeah I've tinkered with the line to wastegate (pluged it) and get some awsome boost and the performance is awsome, But like you said it cuts out the injectors or ign. when it hits about 14 to 15 psi . 1st gear it hits up to 17psi, then second thru 5th gear it cuts out about 13psi.....
SO, where does this diode installed at (power module or logic module ? ) or in sensor that reads pressure? I have an Garret unit... well let me know or anyone else. Thanks

The diode is soldered right at the MAP sensor. between the green/red and black/blue wire. The diode's stripe is closest to the green/red wire. DON'T forget the needed extra fuel if you haven't done that yet! Here is the page I got my info from:

http://www.thedodgegarage.com/turbo_map.html

there's a lot of great info on those pages!

Quote:

Originally posted by joffficer The diode is soldered right at the MAP sensor. between the green/red and black/blue wire. The diode's stripe is closest to the green/red wire. DON'T forget the needed extra fuel if you haven't done that yet! Here is the page I got my info from: http://www.thedodgegarage.com/turbo_map.html there's a lot of great info on those pages!

Hey Thanks, One question about what what said on dodgegarage.com about non-computor controlled wastegate...
I know a soleniod valve on the right with three other solenoids control the wastegate, (now?) does the computor control that solenoid? >>(my thought that it does, but I haven't look in shop manual yet. so I might be asking this too soon before I done my homework) But that info. helps. thanks...

[TurboMinivan]

Quote:

how would you go about porting out the wastegate passage?

1) remove turbo from car
2) remove actuator and downspout
3) examine wastegate passage exit. You should see a shiny area where the flapper valve covers the hole. See how there is lots of extra shiny area around the (smaller) hole? Get a grinder and port out the opening. DON'T go all the way out; you need to leave a small lip for the flapper to seal against. I'd leave at least 1/16" there.
4) carefully blow out all metal shavings
5) reassemble turbo, then reinstall in car.

Tah-dah! Ported wastegate passage.

BTW: if a turbo upgrade is in your future anyway, don't bother. Just buy the turbo now and do the R&R labor only one time.