D valve intake?

[BeRad]

Hi,

Ive been looking at a 3rz related forum in the US, and a few of there forced induction cars, are running these "D" valves, its just a plumbing check valve, which is mounted just before the throttle body, running on the idea of when the engine is in vacuum it draws its air through the check valve, saving the engine from sucking air from the long intake piping. As soon as positive pressure is made by the turbo the check valve shuts and the engine draws from the intercooling piping as it normally would.

Some of them are claiming a 700rpm gain in turbo response from this plumbing 1.5inch check valve, can anyone see this being a gain wheather it be a small or big increase, it seems good in theory and maybe even worthwhile for the price even if it provides minimal increase in response.

Heres a bit of a writeup someone has done on the modification

http://www.shelbycsx.com/csx321/buildup/dvalve.htm

[oldcorollas]

if you nail the throttle, do you get lower than atmospheric pressure between the TB and the IC?
if so, maybe it would help.. if not, not much difference?

[clubagreenie]

If it's just a flapper valve it'll only be made of quite thin rubber and prone to pop out the other way under pressure.
Correct me if im wrong bu from the pics hes got the airbox (with K&N installed by his own admission) then BOV/D valve and into the I/cooler. I would've thought (here's my glaringly obvious statement that I know little re turbos due my belief that they are for people who don't want to think about how to make power) that you'd draw through the airbox into the turbo (how I've seen it unless the filter is hanging on the turbo) then through other pieces of black magic. And the bov should be after turbo (which may or not be the case in the linked example)

[BeRad]

oldcorolas, im not sure, i guess a boost/vacuum guage hoooked into the piping would give some answers?


I bought up the question of the flap blowing out but they replied with that the valves can hold some ridiculous pressure, i might have to go to bunnings or something and have a look at some specs on them.

His pics look quiet confusing but from what was discussed, i took in that its mounted just before the tb in the cold charge pipe, and as soon as any sought of postivie pressure is reached it would slam shut, although most turbos spool a little boost almost instantly and hold that 1 or so psi until it can fully spool.

It was just an idea that looks like it "may" work and was just after some input.

[roadsailing]

I have heard these mentione in alan allard (is that his name?) books about turbocharging things, he seemed to think they were a great idea, and had used them.

i'd give it a go, reliability would be a big concern for me, but if they are pretty robust i cant see a downside, especially if you have lots of cooler piping and a big intercooler

[JustenGT8]

OK you lost me, how is this supposed to improve turbo response?

[roadsailing]

rather than suck air throgh the intercooler pipe, it sucks it straigght in upstream of the intercooler.

the imagined downside i see is that the vacuum of the ingine isnt "dragging" the compressor wheel to accelerate, but im not sure it does much anyway.

[BeRad]

Im not 100% sure although my guess is because the engine can suck in the air easier by bypassing the cooler etc it can spool the turbe faster, by being able to rev easier/faster, similar to having a good air filter vs a cheap air filter being a set back, by the engine having to work for air.

[clubagreenie]

the imagined downside i see is that the vacuum of the ingine isnt "dragging" the compressor wheel to accelerate, but im not sure it does much anyway.

I thought of this but do exhaust gases move faster than inlet?

[JustenGT8]

Hmmm, this is one i'd really have to see to believe. Even @ zero boost or even slightly below positive pressure a turbo is flowing more air than the engine in n/a would take so you'd think this would be a bigger advantage than drawing from atm?

[Ben Wilson]

I suppose it comes down to weather the valve provides a bigger restriction than the turbocharger and the intercooler. On cars with restrictive intercooler plumbing it might make a difference, but good plumbing would be a better way to do it.

[Mr Revhead]

why not just design a good intake system?
with a good non restrictive cooler.

[Mitchee]

Take a look at the photos on the website linked, how exactly does that system work? It looks as though the air path is Turbo > Intercooler > D-Valve > Air Filter > Throttle Body ????

[BeRad]

it is like that, but the d valve bypasses all of the shit before it when the turbo is not spooling boost

[rolleraction]

I'm with Ben & Revhead on this one.......