Question regarding stock turbo efficiency and boost control (X MR)

617G · Jul 29, 2009, 09:36 AM

After finally getting tuned, and speaking with the tuner regarding boost on my X MR, I have a couple questions. At first, boost was somewhat erratic, but the tuner was able to stabilize it, but the drop-off towards redline is pretty bad. This is the tuner's first MR, and big thanks to Jon at HB Speed; we couldn't have done it without him!

Stock turbo cars and ecu control boost is new to me. I'm coming from a TT G35 with an EBC and piggyback.

Mods:
ARC FMIC
ARC Intake
Cobb Catted DP
Greddy Ti-C
Restrictor pill removed

1. Why is it that as soon as I hit peak boost (24psi or so), boost begins to fall drastically 1000 RPM's later to 16.5 at redline. Is this the nature of the turbo or the stock boost control? I noticed GSR's have similar tendencies, but taper to 18psi and hold boost longer; is this related to the MR? The tuner mentioned that it seemed like something (perhaps the transmission) in the ECU was fighting his settings and that he could not raise boost at all.

2. What other methods are there of controlling boost aside from an MBC or EBC? I would like the ECU to control boost. I have heard talks of a GM boost solenoid that gets rid of the stock solenoid system with pills and is able to hold boost much better. Good example of this is an FP Red that the tuner did and the GM solenoid held boost almost until redline. Unfortunately I do not have a comparison of stock boost solenoid vs GM boost solenoid so that may just be the nature of the turbo.

3. For those of you running FP Red's, GT30's, etc, etc...what are you using to control boost?

Please discuss. Thanks.

kwanza · Jul 29, 2009, 09:41 AM

1. boost taper

2. yes, 3 port with ECU mod, i think they are doing it on the 10s now

Clipse3GT · Jul 29, 2009, 10:31 AM

Quote:

Originally Posted by kwanza

1. boost taper

2. yes, 3 port with ECU mod, i think they are doing it on the 10s now

Yes, I have a 3 port on my car, not as much boost taper as stock.

Crazy K · Jul 29, 2009, 10:34 AM

I run a gt30r on my evo and I just use a good ol'MBC from hallman its been working great and I run 25psi and it tapers to like 24psi at redline

newcomer81 · Jul 29, 2009, 11:47 AM

the stock turbo runs out of breath and huffs a lot of hot air when you hold high numbers to redline. stock ebc & possibly a new pill and you can expect high 20's peak tapering to 17-20 redline. on the stock ebc semi-recent 4th gear pull i had 26@3300rpm falling to 20@7000rpm. 3rd gear this morning i did 27@3400 falling to 18@7000 which is typic of what you would expect to see

617G · Jul 29, 2009, 12:51 PM

interesting...so is the stock boost control system tapering the boost because Mitsu knows that the stock turbo is not efficient past a certain point? It appears as though the tq curve follows the boost curve. If I can stabilize boost towards redline, I can get a more linear tq curve.

If I swap it out to a gt3076R turbo, will the tapering still be the same if I use the stock system?

Clipse3GT · Jul 29, 2009, 01:06 PM

Quote:

Originally Posted by 617G

interesting...so is the stock boost control system tapering the boost because Mitsu knows that the stock turbo is not efficient past a certain point? It appears as though the tq curve follows the boost curve. If I can stabilize boost towards redline, I can get a more linear tq curve.

If I swap it out to a gt3076R turbo, will the tapering still be the same if I use the stock system?

*cough* Don't get the 3076R *cough*

No the the stock is a 2 port bleed style and the 3 port is a interrupt system which is more precise at holding boost.

GST Motorsports · Jul 29, 2009, 06:09 PM

Upgraded boost pill will help. I just tuned a MR to have a much flatter curve than what you are showing.

I don't have the logs in front of me but I will try and post them tonight.

617G · Jul 29, 2009, 06:33 PM

If you could post that I'd appreciate it. Where did you get the boost pill from? I vaguely remember vendors selling them.

GST Motorsports · Jul 29, 2009, 08:59 PM

Here you go.

Evo 10 MR

Greddy Ti-C TBE
AEM intake
AMS FMIC
Injector Dynamics 1000cc injectors
GST Boost Pill
EcuFlash tune

23.75psi @ 3500 rpm

23.46psi @ 6000 rpm

20.5psi @ 7000 rpm

HB Speed · Jul 29, 2009, 11:22 PM

Quote:

Originally Posted by 617G

After finally getting tuned, and speaking with the tuner regarding boost on my X MR, I have a couple questions. At first, boost was somewhat erratic, but the tuner was able to stabilize it, but the drop-off towards redline is pretty bad. This is the tuner's first MR, and big thanks to Jon at HB Speed; we couldn't have done it without him!

Stock turbo cars and ecu control boost is new to me. I'm coming from a TT G35 with an EBC and piggyback.

Mods:
ARC FMIC
ARC Intake
Cobb Catted DP
Greddy Ti-C
Restrictor pill removed

1. Why is it that as soon as I hit peak boost (24psi or so), boost begins to fall drastically 1000 RPM's later to 16.5 at redline. Is this the nature of the turbo or the stock boost control? I noticed GSR's have similar tendencies, but taper to 18psi and hold boost longer; is this related to the MR? The tuner mentioned that it seemed like something (perhaps the transmission) in the ECU was fighting his settings and that he could not raise boost at all.

2. What other methods are there of controlling boost aside from an MBC or EBC? I would like the ECU to control boost. I have heard talks of a GM boost solenoid that gets rid of the stock solenoid system with pills and is able to hold boost much better. Good example of this is an FP Red that the tuner did and the GM solenoid held boost almost until redline. Unfortunately I do not have a comparison of stock boost solenoid vs GM boost solenoid so that may just be the nature of the turbo.

3. For those of you running FP Red's, GT30's, etc, etc...what are you using to control boost?

Please discuss. Thanks.

You are welcome

Have Chris call me and ill set him up with what he needs to run more boost on that if you like :-p

617G · Jul 30, 2009, 07:14 AM

Quote:

Originally Posted by GST Motorsports

Here you go.

Evo 10 MR

Greddy Ti-C TBE
AEM intake
AMS FMIC
Injector Dynamics 1000cc injectors
GST Boost Pill
EcuFlash tune

Thanks. Do you manufacture your own pill? Does it replace the one Cobb wants you to take out for Stg 2 or a different one? Why the 1000 cc injectors?

Thanks.

617G · Jul 30, 2009, 07:16 AM

Quote:

Originally Posted by HB Speed

You are welcome

Have Chris call me and ill set him up with what he needs to run more boost on that if you like :-p

You the man Jon. I'll talk to Chris. I'm not looking to run a lot more boost...maybe 25psi peak. I'm more concerned about holding boost better towards redline to flatten out the tq curve. Do you have any examples of MR's with whatever it is you're referring to? I looked at your dyno database and couldn't really find any that held boost well until redline; they all seem to drop off like mine...maybe not as bad. I know Chris tried some things, but they didn't work.

Jon, a bit off topic, but I also sent you an email regarding the behavior of the SST now and how it shifts. If you could look at that and reply, I'd appreciate it. Thanks

GST Motorsports · Jul 30, 2009, 11:14 AM

Quote:

Originally Posted by 617G

Thanks. Do you manufacture your own pill? Does it replace the one Cobb wants you to take out for Stg 2 or a different one? Why the 1000 cc injectors?

Thanks.

Yes we make and sell our own pill.

It replaces the factory larger pill on the pressure side coming off the compressor outlet pipe. We leave the solenoid side pill in as we have found from testing over the years that they smooth out the curve.

1000cc injectors for E85.

617G · Jul 30, 2009, 11:19 AM

Quote:

Originally Posted by GST Motorsports

Yes we make and sell our own pill.

It replaces the factory larger pill on the pressure side coming off the compressor outlet pipe. We leave the solenoid side pill in as we have found from testing over the years that they smooth out the curve.

1000cc injectors for E85.

Interesting. Thanks for the input. I will definitely be giving it a try!