I'm sure this question has been asked, but it is a hard topic to pick a term to search for. I did try to search, and didn't quite run into exactly what i was looking for. Hopefully this thread will stand out a little bit in future searches for members with the same question.

On my new gt30r the boost curve or "characteristics" seems to be a bit odd, from my perspective. Though i have a hunch that what i am witnessing is normal, i'm not sure if it's just for this turbo, or all Garrett turbos (or even large DBB turbos in general.)

Lets start with my stock turbo and Hallman MBC. On my stock turbo i had boost at 23psi via the Hallman MBC, when boost hit it would quickly spike to 23 psi at low RPM's and from there begin to taper down until redline. Seems normal here...

Now when installing my 30r w/ 44 mm Tial i turned the MBC all the way off, in order to employ a safety measure of which is smart to start from, and to see where my wastegate spring was set at. Using this method i would quickly reach (not spike) 18-19 psi and from there boost would go to 20-20.5 psi in about 1000-2000 rpm's; and stay there until redline no tapering. Not sure if these turbos are supposed to taper at all or not... But i am pretty sure they aren't. So all seems good here to, except maybe the odd way in which the wastegate controls boost; i would somewhat expect it to act the same way the stock turbo wastegate does in which it quickly spikes, and stays mostly steady from there (except when reaching redline).

Here comes the very questionable part. With the MBC on and set; the turbo SEEMS to first spool in an identical fashion to how it does with the MBC off (just wastegate controlled); meaning it quickly spools to 18-19 psi and then creeps up to 20-20.5 shortly there after (still no spike). Now with the MBC on, after it creeps up to the 20-20.5 mark it quickly jumps up at where the MBC is set (where ever i set it at, but lets use 23 for example) and holds that psi to redline. Though at the point where it reaches the MBC set boost, it is already at about 6500 rpms and only holds the boost i want it to until redline, which is about 7500... So i guess the main reason this bothers me, is that is only really boosts to what i want it to for about 1000 rpms...

This seems to remind me somewhat of how the 20g-lt's act...

Is this boost creep? Is this normal? Is it just because of the stronger wastegate?

im really tryin to pick up what your puttin down but am some what losing ya... from what im getting is that the tial 44 is controling boost way to perfect and your not quite use to it....
its alot of info and just tryin to help you get to the point

bump for a well thought out question that needs a better answer than what i provided

lol yeah sorry, it's a long read; and i can imagine it's a bit of a challenge to even pay full undevided attention to the entire time...

It proved to be quite a challenge even just trying to put what i was experiencing into writing, so i fully understand if it's hard to comprehend.

The main thing people need to key into is the last stage of my testing, in which i had the MBC set. I just added my pre-testing to show you guys that my MBC and other variables shouldn't be off, based on how they acted optimally with the stock turbo.

I guess the real question is: do all you large turbo guys with Tial WG's pause at wastegate spring pressure durring spool (whatever it may be) before climbing to MBC contolled pressure a few thousand RPM's later?

In lamens terms, my boost curve is NOW w/ the MBC set going up quickly (without a spike at the end of full spool) than slowly creeping up for a couple thousand rpm's (which seems to be indicitive of the wastegate) and then jumps up to the boost controller's pressure at the end of the RPM range?

^ This just doesn't seem right to me... Or is it normal? When is it normal? In what case/circumstance?

I dont think its normal. Boost creep is a problem, which it sounds like thats what your describing. Mabye try a weaker spring, like a 1 bar. The boost should rise right up to your target, then hold that to redline. What size a/r housing do you have on your exhaust side?

u have the ATP kit, so u have a 38mm wastegate not a 44mm.

I thought of something else, where does your boost source come from, and where does it go into the wastegate? What hole did you tee it into on the wastegate?

not trying to speak for him but if its the ATP kit, it tees off the side port and the top of the wastegate is vented.

+1

BTW is that badger milk in your avatar?

Oops, sorry. There always seems to be misinformation about. Though the stock wastegate that came with this kit did have problems and was modified/changed; so there is a chance it's not the 38 that comes with the ATP kits... I seem to remember the past owner saying 44.

If it helps at all my wastegate almost touches my radiator, it's a pretty friggin big shiny thing...

Is it boost creep though? It never goes above where i set the MBC at... Weaker spring might be a solution... Oh oh, and i was told it is the biggest hotside offered, i think .82...?

I agree though that it should go directly to the MBC set boost level and hold from there... I just wasn't sure because that is just what i "thought" i had no real proof.

Any other ideas?

no its not badger milk, haha. its not even the protein on the front of the bottle thats in it.

well the 38mm is big as well. if u do a search on my thread, i posted a bunch of pics of my brand new kit. i have the 3037s with the .82 hotside. i ported mine already and waiting install and tune on the 16th at Pruven.

Saweet! You better keep us updated so i can have a dam close comparison.

btw, search for my other recently made threads; there is some information in those that you will find usefull for your install, etc.

Well, from what I understand from your example, your boost is not holding. Its fluctuating, correct? its not reaching full boost until 6500 rpm? It should shoot all the way to 23psi, then hold that to redline. What I would try first is changing where the wastegate tees in, from the side port, to the top port. If that has no change, I would try a softer spring.

You also didnt answer where your wastegate is getting its boost source from.

Done, those are easy fixes so it's at least worth a try. My boost source if from the LICP, all ATP kits work as such.

I'm 99% sure the MBC to boost/pressure source is correct... But i am not so sure if the rest of my extra BCS lines are hooked up correctly. Does it even matter what those do? We just looped one, and plugged the other...

Edit: it's hard for me to point the finger at the MBC because it DOES hold the MBC's desired boost, and doesn't fluctuate above that...

It's like i hit full boost at 42-43 00 rpm, but then it slowly crawls up to ACTUAL full boost after that... Can't be right...

i have been and i have been posting in them religiously. come on, the feet avatar should be somewhat fimiliar.

these are my mods

Buschur 3” turbo back with test pipe
Aem intake
Forge diverter valve
Hallman mbc
255 walbro fuel pump
Megan o2 housing
Megan exhaust manifold
Custom dynoflash
NGK BR8ES or 7
780 cc Buschur injectors
20g-9-5 Buschur turbo w/10.5 hotside
Buschur deluxe FMIC with lower piping
HKS 272 Intake and Exhaust cams
ACT MB7-HDSS clutch and pressure plate
10.45lb steel Prostreet online flywheel


im adding the ATP kit.