igratton

Hello Again Petrolheads...

Techie engine/ecu question for you all.

I've just fitted a Venting Piston Dump Valve onto the trusty steed.

The car also has

*Scoobysport BackBox
*Scoobysport Flowed Downpipe
*Ramair Filter.

The car has always been nice and loud since the above mods and prone to the odd backfire on overrun etc (which is nice )

Since fitting the Venting Dumper the car seems to backfire even more (i.e. on gear changes at high revs etc). If I am stationary and rev the car quickly to just less than 3K RPM the car backfires so loud it sets of car alarms etc.

In my recent post about the trackday at Donnington on Sunday 22nd August (See Events) one of you mentioned that Venting Blowoff valves deprave the ECU of a reading of an oxygen sensor (the pipe that feeds back from the original non-venting valve housing) which can cause the car to run rich - stating they should not be used with imprezas (even though the likes of Blitz and HKS produce such devices).

Is this rich running likely to cause any engine damage ? the last thing I want is an engine that goes ppppsssshhht and then BANG !

Would you reccommend going back to the standard valve - I'll be on the track and the car will be reving quite high (as is the case at such days) all the time.

Your views please

Regards

Ian

Andrew Dixon

I can't see how a 'dump to atmosphere' valve can be any better or worse than a recirculating valve. Except in terms of the amount of noise that the former makes!

Surely a recirculating valve will just dump to atmosphere back through the air filter anyway?

If anyone knows otherwise then I'd love to understand it better!

Andy

R19KET

I've tried a dump to atm' valve, and the car ran like a dog.I have an air fuel ratio meter fitted,and the poor thing didn't know if was coming,or going.When you change gear,and dump air out of the system,the lamda sensor sees,and tells the ecu you're running rich, so the ecu then reduces the fuel.Then because it's a false reading,the car goes lean,so the ecu chucks a load of fuel in.Seen on the afr meter.

The effect is ORRIBLE.Car runs fine inbetween gear changes.Now changed back to a recirculating d/v.

Mark.

Darren Soothill

The important difference with a recirculating valve is that it puts the air back into the system after the airflow meter which is just by the air filter.

If you have to draw more air through the engine then it causes the sorts of problems that Mark has had as the ECU gets confused as to how much air the engine has had go through it.

Darren

Dave Mitchell

I have a HKS SQV blow off valve on a MY93.
And i get/see no problems.

igratton

The final question...

some of you say your cars run bad with venting blowoff valves...some of you say its ok.

Is this excess backfiring and running rich likely to cause any damage ?

Regards

Ian G.