Trebor69

Hello All

Currently running a MY93 WRX with following mods

HKS Downpipe with Decat 3" Exhaust
HKS FMIC
HKS FCD
Dawes Device at 1.1 bar
HKS Air intake system
VF34 Turbo
Z4 ECU

Until recently I was using a HKS SSQV Dump valve but was didn't like the sound, Too loud and when coming of throttle on lowish rpms I got a Fud dud dud dud dud dud noise... Very Annoying. I even tried the re-circ adaptor and fed it back into air pipe between turbo and MAF. Still noisey due to Powerflow Air intake

So I removed the HKS SSQV and fitted a Forge Re-circ dump valve. This dumped ok, bit of a hissy sound though, but was causing the car to stall when coming of throttle, So from advice here tried diffo springs, fitted stronger springs and shimmed until it idled ok when coming of throttle.. But i ended up with the fud dud dud dud dud dud sound again...

So decided to give the Forge dump to atmos one a go, this has two valves to keep the DV shut on idle, this did cure my idle problems. but got the Fud dud dud thing again. so tired stiffer springs, noise was worse, so fitted softer springs until the Fud dud dud noise went.... Now when coming of part throttle I get a quiet hiss... Not bad... When coming off full throttle, I get more of a whistle then a hiss...

So all seemed ok... but.. when driving on motorway and coming of throttle a little bit to slow down a little I get a little hiss then it keeps going like its sucking in/letting out air..... If I come of the throttle more it stops but then the car slows down a lot (no throttle)

Am i right in saying this can't be good for the engine?

Is the fud dud dud noise I get because of having a FMIC fitted?

All I want is a Dump valve... Pref Re-Circ that sounds good, more low freq than high and opens and closes properly...

Anyone got any ideas for me.. I am getting bored of playing with springs n **** now...

I know the dump valve is always going to be fairly loud as air intake system fitted

Do I need special one to work properly with FMIC, more air to dump??

Looking forward to your replies.. hopefully in depth.. No one word asnwers please :O

Trebor69

One idea I have had is:-

Where the smaller sping is in forge dump valve to keep shut at idle, maybe if I shimmed this spring it should stop the primary valve opening to easily?

Maybe I'm talking poo, but if anyone knows the workings of the Forge Atmos DV please let me know

Cheers

Rob

Jake

I had similar problems with my hks fmic, I started off with a forge and the car run like ****e coughing and jerking on liftoff [maf jerk]. Then fitted an SQV and it ran better but not how I wanted it.

I then fitted a Link and dumped the MAF and now it runs like a dream with the sqv no jerk at all.

Trebor69

Hello

I don't have any running problems appart from the valve staying open under light throttle decrease when on motorway...

Just want a Dump valve that works well with FMIC

StickyMicky

doesnt the standerd valve work?

Scoty

Rob, had the same problems when running without a dump valve and APS FMIC
The noise and response coming off throttle spoiled it.
I fitted the standard dump valve back on and vented it back into the inlet.



I now get a very small quite breeze when coming off throttle and no more fud dud dud dud dud dud
The type of hose you use to vent the dump valve back into the inlet will play a big part in the noise it makes; the first stuff I used had no noise at all, but had a burst pressure of 1.3 bar so it didn't last long, the green stuff I've got just now will take 40 bar, but there is a slight noise when the dump valve is venting back into the inlet, probably becuase of the small ribs on the inside wall of the hose.

Trebor69

Hmmm Didn't think of that!!

Is the standard dump valve 1 inch inlet and outlet?

Is the standard dump valve more quiet than the Forge,Bailey, HKS etc? As I have a powerflow air filter it doesn't hide the dump noise when re-circing compared to a Panel filter

I currently use a samco 1 inch internal bore silicone hose.. it is slightly ribbed.

Is the standard dump valve one or two valve? I.E will it shut properly when coming of throttle down to idle... hence no stalling!!

Anyone got a standard dump valve going spare???

cheers

Rob

Scoty

Without messuring it, think it's about 32mm?

Yes, it's almost silent compaired to the likes of Bailey, Forge (unless recirc), HKS and Blitz etc
I've got an APS cold air kit (K+N filter) and there is no blow back through the filter on lift off, none that you can hear anyway.
With no dump valve, the noise through the filter is unbearable, it sounded a bit better when I had a Blitz induction kit fitted, but comin off throttle after full boost the car's response was also unbearable.

98 standard dump valve is one valve, operates on vacum, valve is hard to open but easy when there is a vacum if that makes sence?
It's only when you start to fit after market dump valves that you start to get idle probs and stalling, I know there is plenty of cars running out there with no probs on after market dump valves, but I havent yet heard of someone having to replace the original dump valve because it wont close on idle, all have been with aftermarket ones.
Fit an after market VTA dump valve if you want a noise comin off throttle, it will do nothing else apart from possibly cause idle probs, stalling, worse throttle response, higher fuel consumption and collect dirt

Suppose it depends what you want, think the ideal set up is no dump valve so your not bleeding the boost pressure away as quickly.

Standard dump valve= no stalling, good idle, and no noise boost dumps

Scoty

What size is the dv spout from your FMIC pipe, you could probably adapt any MY standard dump valve with some silicone hose reducers or something?

Trebor69

My outlet to dump valve is 25mm and inlet back to air bock is 25mm too

I can easily fit a reducer if the O/E valve is 20mm or so

Just got to find an O/E dump valve now..

Rob

AndrewC

Scoty,

1. How have you attached the DV return and ISCV hoses to your inlet pipe (assuming that it's not a samco inlet hose but an elbow as part of a custom inlet) ?

2. How much boost are you running?

Andrew...

Scoty

Andrew

I cut a hole in the elbow to allow a t-peice to be fitted (made sure it was a very tight fit so as not to suck in unmetered air, the T peice has got barbs on it?)

1.4 bar on a 20G.

Scoty