Wastegate dilema....

[legvw 0]

Right, i'm having a bit of a think about my set-up.

I went to emerald to get my car tuned, and because my boost controller (n75 valve) wasn't working they could only tune it to 0.5 bar of boost. They also said i'd need a bigger wastegate (mine is 38mm turbosmart) as i was getting boost creep when on boost.

I've heard a few rumours about smaller wastegates being better for higher boost, and larger wastegates being better for lower boost, is this true??

My question is;

Do i keep the wastegate i've got, buy a new n75 valve and hope when i wind the boost up it works...

Or buy a new bigger wastegate, n75 and then hope it works?

[Dazdub 0]

Dont know if this helps at all mate http://www.boostvalve.com/1.8info.html

[matty.vrt 120]

i have 38mm waste gate .5 bar fine 1 bar fine 1.5 bar fine 1.7 bar fine oops there goes my drive shaft. Try using a 1 bar wastgate spring instead of using the emerald to control the boost.

[CALICO 130]

what size is the one you sold me you can borrow try that

[legvw 0]

i have 38mm waste gate .5 bar fine 1 bar fine 1.5 bar fine 1.7 bar fine oops there goes my drive shaft. Try using a 1 bar wastgate spring instead of using the emerald to control the boost.

Yeah that was the other thing, whether to junk the n75, and just run off of the spring.

[legvw 0]

what size is the one you sold me you can borrow try that

I think its the same size mate, with the same spring in it, 7 psi, thanks anyway rog.

[FishWick 21]

I've heard a few rumours about smaller wastegates being better for higher boost' date=' and larger wastegates being better for lower boost, is this true??

[/quote']

Yeah that's true. High boost on most turbos bypasses very little exhaust gas, so WG sizes can be smaller. Some race engines use the turbo's maximum boost pressure all the time, so they don't have wastegates at all.

Low boost bypasses a lot more exhaust through the WG and big gates therefore cause less of a restriction (compared to small ones) when dumping it all back into the exhaust system, so you get less back pressure in the manifold. And less back pressure in the manifold means less of the intake fuel/air is contaminated with exhaust and you can run more advance, which = more power :-)

I'm with Matty actually. I just run a 13psi spring with no boost control and it works for me :-) I use a Tial 44mm though, which is quite a large fella. But it gets to and holds 13psi perfectly with no spikes or creeping etc.

If you are running into creep issues, that means your WG or associated pipe work can't shift the bypassed gases quickly enough, so perhaps upgrading to the 44mm might help that. What turbo are you running?

Electronic boost control is OK for controlling boost in the lower gears and holding the spring shut for as long as possible, but I prefer the simple approach. It's a lot more reliable and predictable!

[legvw 0]

I'm running this http://www.gt3turbo.com/Merchant/product.php?productid=29&cat=0&page=1

with a divided t4 exhaust housing,

It makes sense to just run off of the spring, and its cheaper than buying another n75 valve!

[FishWick 21]

I would run a 44mm with the 60-1 personally, especially if you're running under 1 bar boost.

[legvw 0]

Well the thing is i want to run more boost, 1 bar or more, so would it best to stick with what i've got, and buy a 14psi spring?

[FishWick 21]

Yeah give the spring a whirl first but if it still creeps, you'll need the 44. It's all V band and 1.75" bore tubing, so flows plenty :-)

[legvw 0]

Sounds good to me, yet again, thanks for your help Kev ;-)

[matty.vrt 120]

Kevs a turbo hero he always has the answer.

[AJmk2 2]

Just out of interest what exhaust manifold are your running ? It seems like 38mm should be able to handle at least 450bhp from what i have read else where.

[legvw 0]

I'm using the original vr6 cast headers, onto a custom manifold i've made.

I'l try the spring and go from there, might have it by spring fest :-)

[matty.vrt 120]

Its not about bhp, its about being able to bypass the exhaust gas that the turbo dosent need when its reached the desired boost level.

[FishWick 21]

/\ Yep and he's got a divided T4, so that's a lot of exhaust gas that needs to go somewhere on low boost, and the T60-1 is quite a big turbo!

I'm no hero though, LOL! :-) Just things I've learned from c0cking about with this stuff!

[legvw 0]

Lol! I'm going to buy a 7psi inner spring to go in with the 7psi outer thats in there and see what happens! I'l put my afr gauge in my car first, just to see whats going on ;-)