No Boost

[RyanN]

why do factory turbo setups don't make boost when reving in idle? when in N or P does the ecu fully open the wastegate or something?

[OFENSV]

the engine needs load on it to make boost

[RyanN]

what do you mean by load? a turbo should generate boost if it has enough exhaust gases passing through the turbine. If you rev the shit out of it while its sitting then boost should be made. A mates WRX makes enough boost while sitting (only average revving) to make quite a loud BOV sound.

[(B1) MR_fanny]

when you mean boost u mean the turbo spooling yeah? might be a safety thing for auto's. mines manual and it spools up in neutral.

[RyanN]

yep spooling/boosting. i tried to bypass the stock boost controller (maybe with autos the ecu opens the wastegate right up) with a turbosmart T-controller but with no luck. I installed it correctly(i think) but i wouldn't make any boost over 1 or 2 psi. When installing a manual boost controller what needs to be modified from the r34 stock hoses? apparently the stock setup has a tube coming from the vacume and the intake, shouldn't it just be vacume?

[Yorik]

It is impossible for the ECU to open the wastegate before the Actuator allows it, so there is no way for this to happen. You need to get your turbine wheel spinning fast enough for the compressor to creat positive manifold pressure. If you build your revs up to about 3000rpm then kick it, the turbine will already be spinning and you will create 'some' boost.. You essentially need to get the turbine spinning with some hot loaded exhaust gases.. I too cna create enough boost to get the BOV's to make some noise, but this is dependant on too many other factors to comment on..

I suggest that you do some research into the operation of Turbochargers before expecting anything out of them. A very very good book for this is Maximum Boost by Corky Bell, has enough of the basics so that the beginners can learn and enough of the good stuff so that the more seasoned of us can gain knowledge and fill in the gaps. If you don't want to buy it, download it...

[RyanN]

yeah i would like to know alot more about turbo setups but im a bit of cheap skate so i'll need to find some "free" online info. Another problem i came across was when i removed the Turbosmart manual boost controller and connected the stock soilinoid back up; the stock boost goes up just below the halfway mark (on the factory boost gauge), now only does half that. How the hell did i lose half of my precious boost?

[(B1) MR_fanny]

yeah i think when ur free reving u wont get full boost...the only way to get full boost is under load as someone else has stated, or so i understand.

as for the missing boost...did you plug the solenoid back in? if you didnt ur car would only be runnin 5psi which is half of half..LOL. double check the pipework again.

[RyanN]

solinoid is plugged back in (wiring and hoses), everything has been checked and doubled checked. Makes no sense, should go back to stock boost once reconnected.

[55Nat]

Free reving will give you boost, but this depends on:

Turbo size & the engines compression ratio.

If you have a huge turbo say GT3040 it won't make anyboost at all while free reving, only when under full load.

But if you have a stock turbo with lower compression its not going to make as much boost when free reving, otherwise stock compression you can get the turbo to spool a fair bit when free reving the engine.

[someonestolecc]

I have sr20 with small trust turbo and it doesn't make any pressure on the boost gauge free revving.

If I had a BOV however it would be enough to vent it if the spring wasn't tight.

I don't know what causes this but you don't want boost when free-revving or you'd kill your engine

[RyanN]

hmmm, i bought it up since my mates WRX can make the bov go off while giving it small revs at the traffic lights (don't ask why )

[Oosh]

My stock RB20 will go from ~20psi vacuum to 0psi in neutral so there IS a difference being made, but as mentioned there's not enough exhaust gases (to drive the turbine) being generated when free revving to produce "boost", they aren't directly related to RPM but load.

Try www.howstuffworks.com for basic turbo info. and to gain an understanding of basics physics (relationships between power, energy, etc.) .

Edit: For comparison a Supercharger WILL make boost when free revving, because it's hooked up to the crank and therefore affected by engine revs, it is consuming engine power (typically 10-20kw) to produce that pressure. But it WONT raise the pressure with load, which is why Turbo's are typically more efficient, giving you more power when you need it (when under greater load). HSW has plenty of info. on them too.

[RyanN]

My biggest problem at the moment is to get my stock boost back, would the ecu need a reset after connecting the stock soilinoid back up?

If a BOV can go off when revving in idle then has to be positive pressure, therefore some was made. On that subject, has anyone here installed a Mach 1 GFB BOV on an R34? whats up with the stock "mitsubishi" plumback.