Hello scoobynet,

my Impreza WRX 2001 came with a HKS Blow off valve. Just now I've read that Blow off valves could *potentially* damage the engine. Because for a split second when lifting off the gas the car runs too rich. So how do I come to assume I may have a problem with the car? What I noticed is, sometimes when shifting and I lift off the gas and press the clutch the RPM stays very shortly. Its very hard to explain, but imagine driving and while shifting you stay for a few milimetres on the gas pedal and while the clutch is engaged the RPM stays for a short period of that shifting time.

*RPM goes to 3000, lifting throttle, engaging clutch, RPM still 3000 after split second RPM going down, degaging clutch, giving throttle*
It's very hard to explain but I hope someone gets what I mean. Thing is my Subaru before (2000 Bugeye) did *not* have it. And it didn't have a HKS Blow Off Valve too. So is it possibly caused by the BOV? Running rich and still giving it gas for a split second?

You can imagine the shifting as like staying on the gas for a split second while engaging the clutch...
I really hope that someone understands what I mean.

 

I seem to recall getting this pause when I ran a Bailey blow off valve years ago but can't remember well enough to definitely say that it was the cause.
You're much better off with a re-circulating valve and that's the way I would go, OEM or aftermarket.
Trev

 

I had an HKS SSQV on my hawk STI and the revs were sticking when changing gear...swapped it for the standard recirculation valve and could not believe how much better the car ran and no more revs sticking!
throw the thing in the bin mate

 

If it's the sqv type sumo power sell the part to convert it to a recirculation valve

 

Interesting - recently bought a car with a BOV on it and noticed the revs seem to hang a bit when changing gear.

Is swapping back to recirculating valve easy enough?

 

This is the job, but in reverse.


http://www.subaru-impreza.org/forum/...preza-wrx.html

 

Ok so I'm probably better off without it... alright then

 

I had this in a Corsa and it was caused by a faulty clutch switch. There was no warning lamps but clutch switch DTCs were live when I used the OBD diagnostic tool.

Basically when you disengage the clutch to change gears it cuts the fuel to cause the engine revs to fall very quickly. If the switch is faulty the ECU does not know you've dropped the clutch and keeps fueling in that split second you still (partially) have your foot on the gas.

Worth checking I reckon.

 

thats also worth checking. But how can I do that? Ecuviewer?

on a side note: If i may dump
the bov, what is the best alternative. Thing is bypass valves don't make such a nice sound and I'd like to have a sound like a blow off... Bypass valves are a bit quiet for my taste.

maybe a good alternative in form of another bov?

 

I'm not sure what software that is, but if you have a laptop and OBD adapter there are plenty of freeware apps for DTC reading and clearing.

I have a generic stand alone unit that I keep in the car if I have trouble and don't have my tuning laptop with me. It was cheap, ~£10 on ebay, but the does the job of reading and clearing codes no problem!

 

i won't put all the BoV in this pot. Is your car mapped properly is the first question I would ask. Been running HKS SSQV for 3 years now, never had any rev hangs or funny business going around the bov. Note car always been mapped and tweaked every time I changed an important part.