zullo

I was having trouble with a boost spike after installing downpipe and catback, so I added a poor man's boost controller (to wastegate actuator only).

For the most part boost is now rock-steady at 10 psi, WOT through first 3 gears, no noticeable spike, minimal dip at 4500. However, on the highway in 4th or 5th ( ~3000 rpm), when I put my foot into it I get a steady 13!! . I haven't held it there for more than a couple seconds to see what happens at transition.

Is this boost creep? Should I be getting creep with only my exhaust mods? Would an electronic boost controller be able to handle this better? Anything else to check?

Specific exhaust mods are M2 dp, RB cb, stock cat

BATMAN

from my experience there is more load at the higher gears.

rynberg

As batman pointed out, there is more load at higher gears and more time for the turbos to spool. An electronic boost controller would be much more consistent.

You are not experiencing "boost creep", just elevated boost levels.

XSTransAm

higher load in higher gears makes higher boost. You are experiencing boost creep.

No boost controller can help you because your wastegate is set at 10psi (correct me if im wrong on this number) and a boost controller can only go up from there.

mcf

I had the same problem a while back - read this thread and it might give you some more insights:

https://www.rx7club.com/showthread.p...hreadid=105959

XSTransAm

what do you think boost creep is?

Its when your boost creeps up after the initial spike.

maybe I misread him but this is what i think hes saying he has?

rynberg

NO IT IS NOT. Boost creep is when your wastegate is all the way open and your boost is still rising. Elevated boost just requires more wastegate opening, boost creep requires a larger wastegate (ported).

Also, the wastegate actuator will operate at 7 psi, not 10 psi, so you can lower your boost to 7 psi with a boost controller.

zullo

So my question is whether, at ~3000 rpm with heavy load, my wastegate should be wide open or not. My assumption is that it should be, but that I am still not dumping boost fast enough.

Note that if there is any boost creep, it creeps lower, but I haven't held it there long enough to be sure.

Could there be an issue with the wastegate since I have only simple exhaust mods?

Trolling for an, "Oh, that could be a vacuum leak to the..." :-)

XSTransAm

well i wasent sure on the wastegate number thats why i said correct me if im wrong....

and as far as boost creep goes, i think were talking cause and effect here

911GT2

No, not cause and effect, we're talking mis-defined terms.

Boost creep is a result of there being too much exhaust flow for the wastegate to vent it all, so even if the wastegate is fully open the boost continues to rise. It would not hold steady, in fact it would climb as revs increased.

He's just experiencing a lack of control of the boost due to longer "in boost" times in higher gears. There is no convenient word for this; it isn't creep or a spike.