GT2871 boost creep??

[stevecrc]

Anyone had issue's with boost creep on 2871's?

I fitted a brand new 2871 last month and have been having problems with boost creep. to start with it was making 26psi at by 5500 rpm on actuator pressure alone! this was while with the mapper and so was mapped to this but could only go so far with the mapping due to not being able to control the boost.

Since then I have had the car back to try and resolve this and have pretty much gone through every conceivable thing but cant get to the bottom of it.

As it stands now I have managed to get it down to 18psi on actuator pressure but still need to get it down more according to my mapper.
Everything on the wastgate is ok E.G not jamming and opens fine, I have even tried it with the actuator arm disconnected and it will still make 17psi at 6k, I also tried inducing back pressure in to the exhaust but this made no difference at all, dropped it down from 3" to 2.5".

My spec is:
Nistune ecu
740cc injectors
Z32 afm
Hd Manifold
Full 3" exhaust and turbo elbo
Hmic
and fuel pump ect

Anyone seen them do this before?

[clive]

Exhaust housing?

[stevecrc]

I think its down to the W/G being to small and not being able to cope with the amount of flow. I'm starting to think the only true way of curing this is to go external gate!

[Hugh Janus]

I think its down to the W/G being to small and not being able to cope with the amount of flow. I'm starting to think the only true way of curing this is to go external gate!

why is mine able to run low boost?? do you think it might be my exhaust..knowing how much more restrictive overs yours is?

[stevecrc]

What does yours run just on actuator pressure alone?

[clive]

I think its down to the W/G being to small and not being able to cope with the amount of flow. I'm starting to think the only true way of curing this is to go external gate!

Aka, what size is the exhaust housing?

.64 do suffer with boost creap.

Larger housing not so bad...

Porting the internal wastegate to 30mm will sure help.

Going external is the true answer...

[stevecrc]

ah yeah sorry its a .64

Not sure if I should just port it out to 30mm or just go external and have done with it lol

[clive]

ah yeah sorry its a .64

Not sure if I should just port it out to 30mm or just go external and have done with it lol

Porting = free to 50quid

External = expensive wastegate, plus mani mods/change.

Imo porting will be fine, with a good healthy boost controller and set up right


But, the noise of an external is so soo tempting lol

[Hugh Janus]

What does yours run just on actuator pressure alone?

ill give it a try tomorrow, and ill let you know

i have tried it before just cannot remember what it was

[stevecrc]

May have a word with mr Battye tomorrow and see what he thinks. this is the only thing stopping him finishing the mapping

[clive]

May have a word with mr Battye tomorrow and see what he thinks. this is the only thing stopping him finishing the mapping

Battye told me gt2871's don't creep... Just takes a good mapper and a AVCR...


Pmsl

Yanks know, and love these tubbys..

http://zilvia.net/f/tech-talk/124925...-sr-motor.html


Remember there figures will probably be like on Ron 93/95 fuel

[stevecrc]

Yeah he keeps telling me that even though mine is creeping like a mofo lol

[big_mac]

Battye told me gt2871's don't creep... Just takes a good mapper and a AVCR...

Yeah he keeps telling me that even though mine is creeping like a mofo lol

[jon200]

The minimum i get is just over 1 bar with a Hdev manifold, Apex elbow and 2.75" exhaust. Whats a HMIC or is it a typo?

[Rubix_Cube]

What actuator are you using? Could you get an up rated one?

[stevecrc]

The minimum i get is just over 1 bar with a Hdev manifold, Apex elbow and 2.75" exhaust. Whats a HMIC or is it a typo?

HMIC= High mount intercooler

[stevecrc]

It did have an hks actuator on it but swapped it over to a standard one and made no difference at all. Its not the actuator thats the problem as even with the W/G flapper not conected it will still make 17psi boost.

[M.D.]

18psi that you get at the mo shouldn't be a problem as surely your upping the boost past that anyway.?

If your not then I'd 100% port the housing out to 30mm. That way you don't have to spend any more money and it'll just work. Make a nice job of it though and don't rush. Also make sure you keep everything squeaky clean when you dismantle things.

[Chriscooke]

Mine makes 15psi at actuator pressure. I'm running a gt spec exhaust as well which is 3.75 from the decat.

[stevecrc]

What the mapper is saying is that we will have problems with the duty on the boost controller and not being able to hold stable boost at high revs. Basicly if we get it to hold stable boost up high it will be laggy down low, I think lol