So this forum is littered with threads about how Subaru's don't like dump valves, and how they cause over fuelling and in turn bore wash.

But my question is doesn't getting your car mapped with pops and bangs do the same thing? Cutting your ignition off and dumping unburnt fuel into the exhaust?

Not that i'm thinking of having pops and bangs, think its abit gay lol

Like to get peoples thought and know how, as not heard anyone bring this up before.

 

Isn't it that they already have dump valves, just internal ones that don't pop and bang, and it's the external ones Subaru's don't like? I'm sure there was a thread last week that covered all this.

 

depends how its done. a bit of extra fuel in the over run wont hurt, assuming mapper isn't a cretin and puts way too much in, but systems that just leave the fuel flowing but cut the ignition are asking for trouble.

 

You've lost me there. Internal dump valves?

 

Someone posted a thread a week or more ago asking for advice on dump valves. Someone posted that Subaru's already have dump valves fitted as standard, wrx and sti's anyway. They just don't make the popping noise.

Someone please correct me if I've read that completely incorrectly or got the wrong end of the stick on something there.

 

Subaru have DVs as standard. They are recirculatory (not dumping air for attention in McD or other fast food carpark) as the millions spent on R&D said so.

You can buy after market recirculatory or others that vent to atmosphere giving you the attention you so desire (VTA).

 

Thanks trooper glad I wasn't imagining seeing that. Ill leave the young ones to the car parks and their hissy dump valves I think.

 

aren't the pops and bangs part of the anti-lag function or are they mapped in otherwise?
Trev

 

Anti-lag, there's another brilliant feature for a road car.

 

The real anti-lag on WRC cars is there for a reason. The function also wears out a turbo very quickly..
Any car can ignite unburnt fuel in the exhaust system if you know how without the needless mapping requirement.

 

Had both pops and bangs and a lot of DIFFRENT dump valves throughout my ownership of over 30 impreza’s and they all ran fine apart from an eBay d/v I tried about 11 years ago

Have to say The novelty soon wears off tho like anything else like the loud as fack blitz nur spec really entertaining but then you get bored and fed up .

 

I have a Genuine plastic Subaru recirc DV on my GC8 and it works a treat, the car also pops and pangs but does not have antilag setup. Was out in an STi 7 the other day with antilag on and after about 2 minutes the brakes stopped working as there was no vacuum left for the servo. Not a very good idea on a road car.

 

Pops&bangs are tuned in a different part of the fuel map,A VTA is generally active in a totally different part of the map,when your coming off wot on higher load.
ALS is different again,Can map it mild or aggressive but as said above it's not WRC als.

 

similar thing but not really, pops and bangs are just small amounts of additional fuel in the over run, 'anti lag' or at least what its sold as on road cars, just cuts the ignition but leaves the fuel part so you get massive amounts of fuel through. which then ignites in the exhaust.

 

Retards the ignition rather than cut it.

 

depends on the system, some aftermarket ones interrupt it completely

 

Yes you mean recirculating valves, all Impreza's have them. There not internal and sit near the intercooler. Any excess air gets recirculated back into the system. A VTA dump valve, vents that to the air.

Down sides of this is over fuelling as the engine is expecting the air back into the system though the inlet manifold. Hence why people say this can create bore wash.

As for pop's and bangs I've heard people asking mappers to map some pops and bangs in, so basically it back fires, I'm not sure how this is done though. And to create a back fire like you use to get in tuned up carburettor cars I would have thought the engine would need to dump unburnt fuel into the exhaust. I could be wrong?

 

If you are not making any real positive boost off throttle then its not really anti lag,

Just noise

Pretty sure the real deal leave the throttle jacked open and you lose a lot of braking performance.

I had the basic "Anti-Lag" on my old carberry map

that Rom allows you to have spark cut or fuel cut launch plus "anti-lag" enabled by demister

using that demister one on carberry switches you over to another timing map which can be made as aggressive as mapper chooses

 

Doubt it was because R&D said so, more likely because noise regs and/or accountants said so. All things being equal there shouldn't be any performance difference between VTA and recirculating dump valves.

 

I think if the engine was designed for a VTA cump valve then it would be fine, as Prodrive had one on there Prodrive concept car.

But as Subaru designed the car to recirculate the air back into the system, then fitting a VTA would upset the fuelling, as I've had impreza's with VTA's fitted and when you boost hard and come off the the accelerator the exhaust pops.

Showing that unburnt fuel was being pump though the exhaust.