Boost Pressure Tailing Off On 5th Gen Gt4

[sweatyfox]

Hiya,

Ive been running higer boost pressures on my UK 1991 GT4 and Ive noticed the boost pressure drops as it goes thru the rev range.

Is this because the standard turbos arent up to running higher pressures? or do I have a leak somewhere?

Im running 17 psi, and at about 3,000 rpm where it all kicks off I get 17psi, but then it will drop to 13psi by the time the revs have reached 6,000 rpm.

Also the TVIS has been deactivated and boost controller fitted, but I only ever see 12psi in 1st gear? yet 17 in all others, dose any one know the reason for that?

Thanks,

Lawrence.

[Sketchy]

Hiya,

Ive been running higer boost pressures on my UK 1991 GT4 and Ive noticed the boost pressure drops as it goes thru the rev range.

Is this because the standard turbos arent up to running higher pressures? or do I have a leak somewhere?

Im running 17 psi, and at about 3,000 rpm where it all kicks off I get 17psi, but then it will drop to 13psi by the time the revs have reached 6,000 rpm.

Also the TVIS has been deactivated and boost controller fitted, but I only ever see 12psi in 1st gear? yet 17 in all others, dose any one know the reason for that?

Thanks,

Lawrence.

Mate I think you'll find that the CT26 on the 185 is well out of it's efficency island at 17psi and will more likely be blowing hot air than creating usable charge, If you had a rolling road print out you'd probably see a healthy about of torque in the low revs but it would drop of very quickly as you get higher up the range.

What sort of controller are you using?

Having said that we'll await the arrival of the 185 experts and see what they say...

[Bibbs]

on the gen2 3sgte .. anything over 17psi is pushing it .. and the boost *will* tail off on these turbo's ..

Get one off a mk3 supra, or a ST205 (or rev3+ MR2) for boost to the redline.

[GTForbes]

you'll only get 12 psi in first as there is not enough load on the engine to create a full boost

[sweatyfox]

Thanks for all ur replys :) Had a feeling the standard turbo might be a little small.

How easy is it to fit a mk3 supra one? Straight forward swap? or lots of buggering about?

[Bibbs]

I was going to do this to my MR2 (smae block).

It'll involve "buggering about" .. but then you'll have an awesome turbo, that looks stock.

It involves using the intake of the CT26A and the exhaust of the CT26B .. you'd be looking at 265+bhp and red line boost without doing anything else.