Sanity check (boost levels with Profec)
 

Hey guys,

I'm relatively new to my FD -- it came with a Greddy Profec-B already installed. Now, I suspect over winter I forgot how the dumb thing worked and turned it off. This spring, I took it out and it only boosts to ~8psi on the first turbo, then ~5psi after the transition to redline.FWIW, other mods are M2 ECU, M2 Large IC, N-tech DP, RE Amemiya TA Replica. What I would like to confirm is the following.

1, 8 (might be 7) -5-5 is "normal" with the boost controller turned off. I believe this to be true because I assume it's not generating enough boost to hit the transition. If I turn the controller on, it goes through the transition just fine and the 2nd turbo comes online and holds till redline (10 psi+, depending on setting).

2. There is no "normal" boost pattern with a boost controller installed. EG, there will be a dip during transition, but it will probably vary between cars/settings/etc.

I'm posting this because somewhere in my head, I swear this car did 10-8-10 with the controller turned off, but there's certainly a nonzero chance that I'm an idiot and forgot that I was just on the low setting.

Thanks!

With the controller off, the car is running only on the WG, about 7 lbs.

Does sound like you potentially have a minor boost leak, that will steal some top end boost.

Does sound like your boost controller is doing what it should be. I've turned mine off in wet conditions or when dropping it off at a shop where someone else might drive it (which is rare!).

The Profec B is a great, solid, dependable boost controller that's fairly easy to set up so you've got a good one there.

With a PowerFC you can dial out the transition - my car is set to about 12.5 PSI and it holds it solid to redline, no dip at all. But, the 10-8-10 rule really only applies to bone stock cars.

Dale

That's great to hear -- thanks guys! I'll have to pressurize the intake and check for leaks.. guessing UIM gaskets/etc stuff as none of it has ever been serviced.

Sorry for the thread jack but what/where is the setting to do this? I would love to dial this out or reduce it. My car is currently about 11-8-10 with PFC.

Thanks!

You have to do this with the Datalogit. You can change the RPM that the transition to the second turbo happens, typically if you lower it a few hundred RPM that will smooth out the transition. It's easy to change and try it a few times to get the right RPM.

There's really no good reason for the dip in power for the transition. My feeling is Mazda put it in there for sales purposes - you can "feel" the second turbo kick in, and that makes for a good sales pitch during the test drive.

The transition RPM settings in the Datalogit is by throttle percent and there's also an "off" RPM for when it transitions back to the primary turbo. I think there are like 6 total numbers to mess with, it's no big deal to work with it and you won't hurt anything.

Dale

Thanks Dale!

I will look into that the next time I have the Datalogit hooked up. I have been meaning to lower the secondary to primary transition RPM setting anyway but I didn't know that the primary to secondary dip could be tuned out or even improved.