Myles

iTrader: (40)

This is for Duncan as he mapped my car back along and might be able to shed some light, and Alcazar just because I idolise him! (oh, and he has/had a forge recirc valve fitted!)
Just fitted a Forge Re-circ Valve to the car, secondhand of course (do I buy anything new?!). I can monitor boost pressure from both the PSI3 monitor that gets the value from the ECU, and a boost gauge also fitted, a cheap-assed Autometer mechanical thing but it can be useful.
Anyway, I noticed that on full chat the boost would momentarily go over the 1.55 bar level that I usually see on the gauge, and is recorded in the peak values on the PSI3. It now goes to 1.7 bar for a second before dropping back down to 1.55, but (and this is a weird one) the PSI3 shows peak of 1.55 bar even though the mech gauge shows it going higher.
Any ideas? I know the easier way is just to fit the OE recirc back on but that would never answer this question!

alcazar

iTrader: (2)

I think I'd rely on the PSI3.

Most boost gauges are OK up to about 1 bar, then they go inaccurate. the more you pay, the more accurate, but my Defi over-reads by about 5% at 1.5 bar, according to Bob Rawle's super-accurate mechanical one.

If it's worrying you, try not to use full boost before having Duncan, or someone, check the map.

Myles

iTrader: (40)

Thanks for the quick reply, I was a little concerned the first time I noticed the gauge shooting round past the 1.5 bar. I kept my foot down and it dropped back into the 1.5 area.
Not knowing anything about mapping, I presume the mapper ups the boost pressure to a good level (in my example, 1.5 bar) and the system should stop the boost increasing past this, presumably with the boost solenoid?

Jolly Green Monster

iTrader: (4)

psi3 only able to read to 1.55bar..

so it will never show higher..

Simon

Myles

iTrader: (40)

Aaah, that explains it all. What do you think of my situation, does it sound iffy?

Jolly Green Monster

iTrader: (4)

Dont know the spec or the boost it was mapped to.

It is cold now so boost is likely to be the highest it ever will be.

So you see 1.7bar and then 1.55bar on the gauge and. 1.55bar pegged on the psi3?

Myles

iTrader: (40)

Yeah, thats it really, it shoots round to 1.7 then settles back to 1.5-1.55. The PSI3 has 1.55 saved as a peak.

Jolly Green Monster

iTrader: (4)

could be a little high but dont know the spec

Jolly Green Monster

iTrader: (4)

if doing it since dump valve change maybe the other one was leaking?

Myles

iTrader: (40)

Yeah perhaps that is it. Im loath to say that it picked up more quickly as I know its the panacea effect!

Myles

iTrader: (40)

Oh, and thanks for the guidance JGM!

Jolly Green Monster

iTrader: (4)

Refit the other one and compare.

If boost is higher on the new one it needs a map tweak

Myles

iTrader: (40)

It'd be a bloody shame just for a re-circ (even more galling when it carries out the same function as the OE!), but I think you are right. Does a theoretic 0.2 bar 'spike' create issues, or is each situation different?

Jolly Green Monster

iTrader: (4)

You still havent posted the spec so I cant fully answer but if it wasnt mapped to do it then yes.

Depending on the turbo it could cause damage to the turbo if not engine.

Simon

Myles

iTrader: (40)

Its running a VF35, and all the bits to complement the turbo (pinks, STI I/C etc). WRX engine.

dynamix

iTrader: (3)

Hi Myles

as per pm conversation we need to get together to tweak it....

it shouldn't be boosting that high.

duncan