Boost Spike GT4

[The Red Baron]

Good morning

The GT4 I recently purchased had one of those cheap ball and spring manual boost controllers... and no Boost Gauge!

I've turned it right down and it's fine during the day runs great. On a cold night I still seem to be getting Boost Spiking and Fuel Cuts.

I'm going to get it removed on my next service. Until then I've read removing the ball and spring would take it back closer to standard psi and reduce boost spiking. Is this true?

[Fodder]

If you just wind the boost controller to it's furthest 'out' position it should take it back to stock boost.

Most of the ones I've seen (admittedly not many) need to be wound a fair way in before they have any impact.

[The Red Baron]

If you just wind the boost controller to it's furthest 'out' position it should take it back to stock boost.

Most of the ones I've seen (admittedly not many) need to be wound a fair way in before they have any impact.

Cheers, i’ve wound it all the way out (less boost) direction.

Hmm maybe it has another underlining issue. It’s just odd during the day its fine, smooth even delivery the problem only ever occurs on a cold night.

I’ll have the mechanic take a good look over it when servicing it next week.

[Fodder]

It's not unheard of - colder weather = denser air = higher boost = boost cut.

What mods does it have besides the boost controller? I guess it would be possible with a free-flowing enough exhaust and some other mods that boost is raised enough to hit cut whether it has a boost controller or not - you can't use one to lower how it's set from factory.

Taking the spring out might help, can't hurt I guess! But removing it completely will be the best way to go.

[The Red Baron]

It's not unheard of - colder weather = denser air = higher boost = boost cut.

What mods does it have besides the boost controller? I guess it would be possible with a free-flowing enough exhaust and some other mods that boost is raised enough to hit cut whether it has a boost controller or not - you can't use one to lower how it's set from factory.

Taking the spring out might help, can't hurt I guess! But removing it completely will be the best way to go.

I pretty sure the only modification apart from Boost Controller is a 3 inch Aussie Down Pipe.

Now I’m still a beginner when comes to cars, oil change, orbital buffer and wheel change is my limit. I’ll remove the spring in the meantime and give that a go.

Removing it completely will I need to order any parts to replace, or is a more a buy a mate a cartoon of beer and counter meal at the pub job?

[Draven]

they usually just tee in to a vacuum line - buy new length of hose, or a join, and connect.

I don't know about the GT4, but on jz engines going to a bigger dump pipe often results in a jump in boost - but get rid of the boost controller first, as that's a really cheap way to eliminate is as a source of the problem

[privatealpha]

Boost cut is 1bar i dont think a 3inch down pipe would increase boost so much to hit it.
Probably 2-3psi maximum.

Get rid of the boost controller, and plug in a boost gauge.

[Fodder]

*nod* Full aussie exhaust raised boost ~1.5psi for me, so if that's all should still be well shy of the cut.

As Draven said, eliminating the boost controller is pretty easy - just need to replace it with a join, or (preferably) the hoses that connect to it with one longer hose.

If you're not confident, see if a mate or someone off the forums in your area will give you hand. Do it yourself, just have them watch and check - best way to learn is to get stuck into it!

[punkture]

mine is 3" TBE on my 185 gt4, hits 13psi-14psi and fuel cut..free flowing exhaust will do it. install a FCD

[Fodder]

Wow - with just the exhaust on mine I was lucky to hit 10psi on a cold night

[The Red Baron]

Looks like I got it all wrong. The MBC seems to be a screw type.. Turboxs

The directions on the control tell me to down the fine screw down to reduce boost. Sounds like on the website I shouldn't have had the screw turned down all the way (at least two turns from closed position)

Is the gold screw ontop of this model also an adjustment? I've tried to find the manual online.. can't work if it's an old model.

Some seem to have two adjustment methods, course adjusting screw and fine adjusting screw.

Thanks for all your help, sorry for giving you a bum steer about it being a spring/ball boost controller!

[punkture]

fodder, i was surprised too lol

[privatealpha]

Just try it, cant hurt.
If its too much boost, it will just hit the boost cut.

[The Red Baron]

True, i'll give it one last chance and see if it does anything to tone down the overboosting. Otherwise it can go in the bin.