Trebor69

Hello All

I have a MY93 WRX Import with the following mods

HKS Air intake system
HKS exhuast system, with full decat etc
HKS 3 port Boost solenoid
HKS EVC Pro 4 Boost controller
HKS FMIC
HKS SSQV Dump Valve
HKS FCD Unit
HKS Boost Gauge
Uprated Fuel pump (new) Warbro
7D ECU
VF34 Turbo (brand new!!)

I have only had this car 3 months which has been great fun..albiet expensive and it is going into Powerstation next week to have the Uni-chip of which I am just fitting mapped. I have a question about dump valves.

At the moment my car is dumping to Atmos, I do have a love/hate relationship with this!! I know that I can get an adaptor to go on end of dump valve of which I can fit a 1 inch pipe and re-circ air into system, what I want info on is:

Where do I re-circ air into.. Between Air filter and MAF, Or between MAF and Turbo inlet ( I have a silver housing here with a very small tube blocked off and another hose 3/4" approx going to engine block i think)

Will this mean less lag after changing gear?

Will I still get a noise or will it be completely silent?

I also wonder how does it affect fueling for the first second of putting foot back down, as I see it that the MAF has sensed what air has gone in and is fueling to suit, but I have just dumped all that air from system so i have to fill it up again.. I am finking daft here or what??

I have just got the car going very well, so hence now the time for Uni-chipping to get fueling/timing right for mods fitted. And am wondering wether to change dump method before having it mapped!

All info in detail will be greatly appreciated ...

And this isn't a thread for dump valves to atmos are gay chatter ok LOL

Cheers
Trebor69

Trebor69

Anyone....

In hunt for quick info as will have to get recirc adaptor ordered asap!!

Cheers

Pavlo

re-circ is best when using with maf based car

Trebor69

Cheers Pavlo, thanks for replying to my other post in General about gitting my car mapped on unichip next week ..P.S I have asked you another question on that thread!!

http://bbs.scoobynet.co.uk/showthrea...7&goto=newpost

Any ideas on where i would recirc it into as stated above and will it improve spool up?

Cheers

Rob

Kepp them coming!!

Brit_in_Japan

Trebor69, you're not being daft.

The MAF measures the mass air inlet, so it calculates the required fuelling using that sensor data. With vent to atmosphere (VTA) you are dumping a mass of air to atmosphere, but the fuel injected is calculated based on what the MAF has sensed. Result: the AFR will be rich. It will be rich until the lambda control system kicks in and leans off the mixture. Then when you open the throttle again you suck in new air, but the lambda control system initially thinks that you are still running rich, and has told the AFR controller to lean it off a bit. So the likelyhood is you get a period of lean running (maybe fractions of a second). I can give you the theory, but to what extent this lean running may cause damage I can't say. I have tried to get some info about long term effects of running a VTA dump valve, but not had any feedback. Greasemonkey was going to try and find out for me, but I guess he's not found anything yet.

In terms of lag, I would guess there won't be much difference. With VTA when you open the throttle again, the AFR will momentarily go from rich to lean to correct, instead of being more accurate throughout. If anything I guess a recirc would improve the responsiveness after gearchange because it's getting correct fuelling.

There will be some noise, but compared to a HKS SSQV you'll think your ears aren't working.

The recirculated air comes in between the MAF and the turbo.

HTH

Trebor69

Cheers matey, that makes sense to me

When I was talking about lag, I was meaning time to fill intercooler etc up to get to 1.1bar pressure again, If I re-circ all the air in before turbo inlet, obviously the FMIC etc will fill up quicker as compared to when I have VTA'd because the air is dense/compressed. Does this make sense

Cheers for all the replies that keep coming :O)

Would like to hear Greasemonkeys thoughts on this and my other thread cos he's full of good stuff!

Tone Loc

iTrader: (1)

I've now had VTA and recirc (MAP and MAF based ecus).... if your using a MAF based car i'd say that the recirc is best as my car got a bit jerky on and off the throttle mid corner with the VTA. However with regards to VTAs causing rich running etc i'm not convinced. Using VTA and recirc on a MAF based car i saw the AFR increase releasing the throttle on both, reason being that the ecu has determined what fuel to inject given the amount of air passing the MAF. However when you lift off the throttle the ecu is fueling for a split second air that is not where it was expecing it... i.e in the engine. For VTA this is now in the atmosphere for recirc it's now pre turbo/intercooler. So although the recirc valve keeps the air in the 'system' it isn't where the ecu expects it so you see this slight rich blip on the lambdalink/logs etc.

Lean running due to the VTA.... not sure your right on this one Brit-in-Japan. Reason being when you start to move the accelerator no matter what the ecu is doing with regards to the lambda sensor it will now ignore it and go open loop from closed loop fueling. Also as soon as you move the accelerator the ecu will also add a percentage of fuel to cover this initial period of accel. If it's running lean during this initial accel period i'd be looking at the fuel pump etc not the DV.

Tony.

Trebor69

Lots of info... luvely!!!

So my final question which needs answering still is:

When I was talking about lag, I was meaning time to fill intercooler etc up to get to 1.1bar pressure again, If I re-circ all the air in before turbo inlet, obviously? the FMIC etc will fill up quicker as compared to when I have VTA'd because the air is dense/compressed. Is this correct or will I notice no difference in time it takes top get back to max boost between recirc and vta.

Cheers Again

Rob

Tone Loc

iTrader: (1)

I'd say no difference... or none that you can actually detect anyway.

Tony.

Trebor69

Okey Dokey thats all my questions answered... thanks all

Wouldn't mind having a read of another thread i got here and giving me your views

http://bbs.scoobynet.co.uk/showthrea...7&goto=newpost

cheers

Rob

Brit_in_Japan

Hi ToneLoc, you may well be right about the lambda control system not being in-the-loop when the throttle is opened again. It's all a question of degrees. When does the ECU switch-out the lambda control ? How much of a transient is needed to make that happen ? I don't know the answer, but if you do then I'm all ears

Tone Loc

iTrader: (1)

The ecu will switch from closed loop fueling to open loop depending on the load the ecu sees and also as said before if it's adding acceleration fuel (TPS). As soon as you make any sudden movements on the throttle it will switch to open loop, if your are only accelerating gently (i.e still in vacuum not positive boost) then it could well stay closed loop (my ecu seems to switch to open loop at load values above 15). If this is the case the AFR will be swinging all over the place anyway so you will not see any 'lean' running as such as it goes from rich to lean as it rocks around stoich anyway.

Tony.

mart360

if the grey stuff still works,

the clever way is to recirc (aka saab + others)

the dare i say it (chav) (flame suit on and working) way is to vent to air...

i believe by utilising the recirc method it provides better spool up, as the returned air gives that little edge with pressures, fueling etc...

quick Q why do you want people to know you have a turbo ???

surlely just owning a scooby is qudos enought??

could you imagine if every trucker fitted a bov to there rigs???

Mart

SilverTurboWagon

The M25 would be deafening