Hey everyone.

It's a new but old problem.

New because its on my new four...old becuase it's an issue many have had in the past, but i cant find the info o need easily.

Ive recently fitted a aussie d/p and boost controller. this has been added to a mongoose full 2.5" system and with a blitz sus on the intake.

Im not seeing boost pressures of well over 1.2bar (im nto doing it regularily i must add. Only saw it when testing).

It appears the lack of back prssure has allowed significant increase in boost.

I thought from reading all the posts in the past that this was a common issue with the aussie blitz system (being 2,75") or other 3" systems. Never heard it on a 2.5 inch system.

Well what do i need to do...never had this problem before and the car is booked in for mapping on wednesday ...doh

Matt

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1995 ST205

Is this a spike or a creep issue?

If it's a spike , alter the gain on the boost controller.

If it's creep you either need a different turbo, or a different DP, or a different exhaust, or shove a restrcition in the exhaust - kinda defeats the object of opening up the exhaust side though, eh?

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Kris
95 ST205 - slept for 10 years, now waking up...
Avensis
http://www.gtfours.co.uk
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Turbocharging - the replacement for displacement

What turbo?
As Kris has said really -
boost spike (peaks in mid range rpm then falls)= boost controller or sticky actuator.
Boost creep (boost rises with rpm) = wastegate not opening fully or just cannot flow enough air.

Boost creep come about when teh turbine sees a pressure differential less than teh delta pressure differential across teh wastegate - hence basically it is easier for the air to go through teh turbine wheel than out of teh wastegate port! Shows just how poor teh wastegate is.

I know some say that a 2.5 or 3" exhaust is OTT but I strongly disagree - reducing pumping loss' and assisting teh burnt gases escaping from teh cylinder chamber mean you can dial in more timing and hence more power - also means your turbo will spool earlier.

The ways to sort out teh problem are :-
1) get a turbo that flows well through the wastegate - either external gate the CT26 or go the modified Turbo Technics turbine housing route.
2) Add exhaust restriction of some sort - adding a cat, additional silencer or a 2" restriction normally reduces boost creep to an acceptable level.
3) Add inlet restriction

No. 2&3 will reduce your spool up and power.
No. 1 will cost money and time.

even with a 2" restrictor on my old turbo it woudl creep to 1.35 bar at peak rpm from 0.8 bar @ 4000rpm! This meant it was almost impossible to run higher than 0.8 bar at low rpm and made teh car feel un responsive at low RPM.

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JP
GT4DC Treasurer

Grey St185 RC
Silver BMW E46 M3
Multicolour yawn Honda VFR400
Silver Honda Civic Type-R

Hmmm

Stock turbo me thinks.

Looks like i'll be investing in another TT stage 2 tubby then... lol

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1995 ST205

Cheers guys

Oh and its definately creep.

Matt

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1995 ST205