Just gone BPU - Not sure it's boosting fully

Hi guys,

Just picked up my BPU'd Supra today from the garage. Firstly it's definitely an improvement on the stock the turbo's are spooling faster and it's definitely pulling to the redline better.

..... However I have a greddy boost gage which reads in kg/cm2 (which is pretty much the same as bar) and it's only reading 0.7 when the 2nd turbo kicks in which is pretty much stock levels. So I'm looking for some advice on where a potential problem could be

I'm not 100% confident in the boost gauge that's installed. Is it a common problem old for boost gauges to read incorrectly??

The setup is:

JSpec Auto

1.2 bar restrictor ring

Decat pipes

Fuel Cut Defender

Iridium Plugs

Walbro fuel pump

Cheers

Johnny

how old is the boost gauge?? I had one that started to read incorrectly...

lol just did an edit to the original post saying I'm, not 100% confident in it. Not too sure on the age of it as it was installed when I got the car.

What was your reading at when faulty compared to what it should have been showing?

What did the gauge read before you went BPU?

Which exhaust do you have?

0.7 but it definitely feels quicker and more responsive since decatting.

What exhaust do you have?

That's probably another thing I should have mentioned in the first post it's an Apexi catback but my mate did say it was in need of replacing when he fitted the decat pipes.

I also expected the exhaust to be a lot louder since decatting but it's not. Do you think the exhaust may be the problem?

This is the backbox currently fitted:

http://www.jwwebdev.co.uk/Supra/Exhaust.jpg

There isn't such a thing as a 1.2bar restrictor ring, it isn't really an exact science. A restrictor ring that allows 1.2bar of boost on one car, may allow less on another, depending on how restrictive the exhaust is that's fitted

Verify first that there are no leaks and the boost reading is correct. If it is, then increase the diameter of the hole in the ring until you reach the desired boost level.

As Nic says, the restrictor ring will vary from car to car. Tryt it without it (carefully) to see if the turbos will boost over 0.8. If so, you will need to enlarge the holw, probabaly by about 2mm all the way around (ie increase the diameter by about 4mm).

You should feel a real wallop in the back when T2 comes on at 1.2Bar

It sounds like you have a restrictive exhaust and I'd bet you can get away without running a restrictor ring at all. Give it a go and if the boost looks like it's climbing above 1.2bar then refit it but enlarged a good bit.

Cheers,

Brian.

Thanks guys, I'm thinking the exhaust is the problem now especially with the lack of any real note change since decatting. I'll try removing the RR and see how it goes.

Cheers

Johnny

Thanks guys, I'm thinking the exhaust is the problem now especially with the lack of any real note change since decatting. I'll try removing the RR and see how it goes.

 

Cheers

 

Johnny

Welcome to my world:) I thought mine would be alot louder too but was left disappointed and i'm not hitting fuel cut either.

take the ring out mate i have a j spec had the same problem tooks the 1.2 bar ring out and it holds solid if the weather is hot or cold make sure you have got a good set of plugs in there

lee

Mine has no restrictor ring at all, and still won't go above 0.8 bar because of the exhaust

Mine has no restrictor ring at all, and still won't go above 0.8 bar because of the exhaust

is it uk or a j spec ?

is it uk or a j spec ?

It's j-spec, thats why no-one can quite understand what's going on. The exhaust is restrictive, so Nic advised me to fit a boost controller - I did...nothing happened.:(

OK bit of an update to this I fitted a new catback exhaust as my old one was fecked looked like someone had attacked it with an axe!

Anyway it's not had any real affect on the boost pressure so still not hitting above stock levels and I'm a bit stuck as to what to do now.

Anyone got any suggestions as to what may be stopping me from achiving higher boost levels. It's really bloody annoying me now

you certain your not hitting fuel or boost cut?

Definitely not fuel cut, as it pull consistently to the readline when you floor it.

It's got a greddy FCD fitted.

could be boost leak. its easy for something like a vaccum pipe to perish or go adrift. my dads turbo diseasel had a pipe no bigger than the diameter of ya lil finger perish and lost all performance.

other thing to try would be to have the restrictor ring out altogether and go for a poke. keep an eye on the boost gauge to make sure u dun go over 1.2.

would be easiest way to rule it out.

Did you try without the RR?

Not sure that removing the RR would make any difference. As I've gone from having both cats in to decated and new exhaust with pretty much no difference in boost levels.

Would having a really crap air intake stop you from getting bpu levels of boost? I've got some cheap looking thing that came with the car. Not sure of the make it is, the logo is an "X" have posted up some pics so hopefully someone will be able to name it.

Thanks again for the responses

Johnny

Your restrictor ring is too small by the sounds of things, regardless of the exhaust in use, the ring is still the restriction. Take out the ring and go for a drive and see what happens please be careful in case it spikes too high !

If it does boost higher then you know you need to enlarge the ring.

Ok I'll try it without the RR in. I know as was mentioned previously that RR's aren't an exact science. But it's a 1.2 bar Envy RR that's in place so thought I'd at least see it hitting 0.9 of full boost.

That filter looks way to small, also the foam looks to fine, i would get a decent one and try that, and then try without the RR.