Wanted to try atmospheric dump valve to troubleshoot an issue with the OEM ECU with FMICs on swift gearchanges, so I removed the outlet hose from my Forge recirc and capped it off. To my surprise the idle went completely off, and covering the dump valve outlet fixed it.

I don't think it should leak like this on idle? You could see the piston moving up and down slightly at idle...

The OEM dump valve doesn't do this, but I don't think it is strong enough to try as VTA?

 

No it shouldn't really. The idle vacuum should pull it open, but only with the help of boost on the other side.

Paul

 

At idle the piston is well and truly being sucked open by the manifold vacuum. What is opposing this 9.5 PSI vacuum is the (red) spring and that is it, as the inlet to the dump valve would be at or close to atmospheric at idle against only the throttle opening of the idle speed control valve? However, the spring is clearly strong enough to cause light surge compared with the OEM dump valve on lift off.

If you disconnected the manifold feed previously on this dump valve, it would open at about 18 PSI. I should test this again.

Unless this DV is faulty, this means that a Forge recirc is normally open at idle and recirculating. Under boost the manifold pressure signal and the dump valve inlet should balance each other and the spring is enough to keep it closed.

How does a VTA differ to keep it closed at idle?

Notably when I ran VTA with MAF and FMIC tonight it was a lot smoother on lift off with none of those reverse flow MAF hiccups, and I could not get it to do the power cut it used to give if I changed gear too quickly (again I think this is a lean phenomena from flow reversion through the MAF).

 

I've run the OEM DV to atmosphere before, it doesn't open at idle but does some strange things driving around on part throttle. ie opens under light acceleration in low gears.

How about tightening the spring up with a rubber insert. I'm not familiar with the insides of it but surely it would just require a little patients to load up the spring a little more.

 

I'll try some shims and I'll pay attention to how the spring feels inside.

 

Are you sure you're getting surge?

Frank's HKS SSQ vta valve is well and truly shut, and you can hear light chuffing as you change gear. If you get it up to about 0.6bar and change gear, you hear it open.

But on idle, if you leave it as re-circ, does it matter?

On boost the vac line should equalise the pressure accros the diaphragm and your net force is the spring force, I think.

Paul

 

I'm running a shortened (by 10mm) Forge recirc, with both blue and red springs together (and slightly stretched), plus a piece of rubber hose around the outside of the springs. It still opens on lift-off, and I still get the reversion thing confusing MAF. Was actualy going to try what you have John, after trying with none - let me know how it develops please

Richard

 

I have a Forge Recirc valve (on the shelf), when I put it on the car, it makes a whistling sound with every gearchange. Almost enoying for me. Forge has no explanation what it was but I thnk it wars just air passing trough the valve piston on very small openings. The piston is bullet shaped and an original valve is almost straight.

Creepy

 

Forge tell me that their recirculating valve will be open at idle, the VTA has the extra smaller piston and spring to stop it leaking on idle.

I think all my issues are flow reversions through the MAF even with the VTA, need to get rid of the MAF with this much air mass sitting between the turbo and throttle body I think.

 

My Forge recirculate is now to atmophere and I had to add shims to stop it openning on idle.

I only have the blue spring in it and three or two shims (cannot remember).

I bought the tuning kit off Forge for £10 but cost lots of postage and took for ever to get to me. But contained 4 differing rate springs and 3 shims..

You could do the same or made some shims?

Simon

 

Do you remember how thick the shims were approximately... this will sound sad, but I really like the noise of the Forge recirc when it was VTA. OMG I have just admitted I am really a rice boy

 

I thought you wrote nice boy....

 

LOL.

I'll have a look tonight..

It does sound very nice, I just would like to be able to turn it off when I want to sound respectable.. and turn the exhaust down.. lol

I think the spring rates are from weak to stronger - blue, green, yellow, red.

So you are already on the strongest..

I think you might find a 50p fits.. lol..

If you weren't already on the red spring I could have sent you it etc..

Simon

 

Excessive font kerning, or is that soft purring? I'll get my coat....

 

Thanks JGM.

50p for a shim LOL, that will come in handy when I need some money for a phonebox when I break down and my mobile is out of range.... but the phonebox only takes 10p

 

I think it is about the same size as an old 10p.. but presume the only thing near it is now a 50p.. not suggesting you use one though.. lol

I'll check the size tonight.. they are only about 1.5mm thick.

Simon

 

My bailey atmos dv was fully open at idle. It also caused loads of lag when accelerating with full throttle from low revs, hence i sold it after about a week

ian

 

You mean you let it defeat you Ian??

Simon

 

John,

I was wrong..

Springs are Red strongest, followed by blue, yellow, and green is the weakest..

Shim is 1mm thick and diameter is 35mm.

Pictures of a Shim + sexy ****

If you email me your address I can stick one in the post if you like.

Simon

edited to correct url link

[Edited by Jolly Green Monster - 12/9/2003 10:34:49 PM]

 

Thanks, I'll pop into an suitable shop tomorrow and get some 35 x 1mm shims or similar, I'll take the valve along - there is a few mm tolerance in it at least.

 

simon, yeah i did, fuel economy went noticable worse under normal driving with that dv too

ian

 

John,

Yes there will be some tollerance on it.

Ian,

If it was open on tick over it would run like a vaccuum leak which as I know too well it will then drink fuel even more than it normally does.. lol

No idea if the Bailey is shimable etc

Simon

 

So, like, how do I tell if the Recirc Forge dump valve is open on idle .. look into the outlet pipe?

I phoned Forge for the tuning kit or any tips on setting it up, and they told me the recirc valve is non adjustable?
It opens easily enough, not many bits in there - diaphragm, spring, very small plunger ....

So who has bought a tuning kit off Forge AND said it was for a recirc DV ?

Maybe I better ring 'em again...

 

I bought the kit and have used it on the recirculate valve..

Kit cam with 4 identical size springs of different rates and colours and 3 shims..

I openned my valve and the spring was the same as the blue one in the kit and one shim which was the same as the 3 in the tuning kit.

Could it be because your valve is for the older car??

Where as I have fitted a new style valve to my older car?

Simon

 

Position the dv so that the outlet to the air intake is not connected.. remove the pipe..

Block off the now hole in the intake pipe with with a cork rapped in tape, or your hand and on idle see if there is any air coming out of the dv outlet.



I have a high pitched screech from the dumpvalve now.. any ideas how to shut the bl00dy thing up?

Simon

 

Hi JGM

Didn't tell Forge it was for any particular year beyond classic pre facelift, JDM model.

The Guy was telling me about the tuning kit, and then came back to check it was a recirc and said it is non adjustable.
Maybe he got confused, I dunno!

May as well ring 'em again tomorrow and buy one anyway. Seems to have a spring, diaphragm with small plunger so worth a try.

 

John,

I think I have the same problem. When on part throttle with a little acceleration going on, but no boost, I get what sounds like a venting through the induction kit. When you ease off slightly or put you foot down a little it goes away.

Faulty DV?

 

Difficult to tell, I was going to say what you are describing is normal, but without hearing it tricky to say.

On part throttle there could well be a lot of boost pressure trapped behind the throttle plate.

The turbo could be surging, and/or the dump valve could be venting in this situation. You could add another boost gauge off the compressor outlet and test the strength of your dump valve to work out what is going on.

[Edited by john banks - 12/14/2003 10:44:56 PM]