Hi, I just noticed my 93 k-plate WRX isn't boosting as high as it was before. Its only hitting between 0.6 bar and 0.7 bar. Where as I'm sure it was up at 0.8 bar before. I guessed at it being a bad batch of fuel causing the ecu to not allow full boost, but after adding a tank of optimax and octane booster its still the same. The only things that have changed are I fitted an HKS SSQV BOV recently. Does anyone have any ideas? I was concidering reseting my ecu.

 

i'd take a guess its the heat mate, mines down by about 25% on boost on hot days compared to cold. (peaks at about 1.1bar on hot and about 1.4bar on cold)

 

Ok, hopefully its just that then. If I had been getting some knock from 97 ron fuel thought and the ecu reduced the boost. How long would it take the ecu to re-learn that the new tank of fuel is fine and thust allow full boost again?

 

i dont think an ecu on a 93 will relearn or if it does it is very slow. Best bet is to just reset it.

 

Could be the heat, or you could have connected the pipework incorrectly (done away with the boost solenoid or similar by tee-ing into the wrong pipe), and the wastegate is opening at it's pre-set pressure, can't remember for sure what that pressure is on your motor, but probably around 0.5-6 bar.

 

I'm pretty sure that the pipe work is all correct from the BOV installation. The SSQV came with a connector to join its vacume pipe to the original one (I take it thats the boost solonid connection) and the recirc inlet on the induction pipe is sealed up properly. If there was a leak from the small vacume pipe would that effect the boost then? I may run a new piece of pipe to make sure its not that before i try an ecu reset.

 

I'm pretty sure the normal boost for a 93 WRX is 0.7 bar.
The ECU should re-learn after a bad batch of fuel, but you could speed this up by doing a reset.

 

Yup 0.7 bar is pretty standard on a 93WRX.

 

I'd try it without the VTA dump valve!

 

Thats the thing it seems to be slower since I fitted the HKS SSQV. If the pipes are fitted correctly surely the VTA type cant effect anything. I'm sure it used to boost at 0.8bar.

 

Well, I am not sure if fitting a different dump valve, particularly a vent to atmosphere dump valve can afffect the total boost level you see, but the VTA's do dump air that the MAF measured to atmosphere when you lift off and so the ECU puts in too much fuel ... may well make sooty exhaust, pops and bangs on lift off from exhaust, so don't give overall performance improvements ...

Since the ambient temp is a bit high at the moment - 31 - 33 degree C as the radio says, you will likely see lower boost.

Don't worry, unless it stays that way when the weather gets colder!!

 

ok thanks. I'll try and stop being so paranoid. Why would the ambient temperature effect the boost level?

 

Due to inlet air temps, the ECU wants to keep the engine safe so cuts back on ignition timing and boost to stop it blowing up ... that's why people go to better / bigger top mount intercoolers, front mount intercoolrs, water sprays, water injection etc. - to keep inlet charge temp down.

So maybe ECU is letting some boost pressure go to keep engine safe.

In my case, my 18 psi became 16 psi tonight as it was so hot ... same gear, same right foot! That's on an apexi PFC with boost controller ... felt slower and boost gauge confirmed it. Maybe my explanation was wrong but same efect here in hot weather !!

 

ditto on hot weather and lower boost