Strange surging ?

[newsh]

Since fitting my monster intercooler I've had a strange kind of surging happening just as I close the throttle. It doesn't happen if you floor it and let off quick, it happens when you a driving quite gently and come of the throttle slowly. I'm thinking its something to do with the extra volume of air in the big IC. If I ease off on the pedal slowly the DV doesn't open fast enough and I get this strange surge or jolt. I can sometimes get a similar thing on my ur (which has no DV) but nowhere near as big.

Anyone got any experience of this or something similar??

I wonder. Would an extra DV or an atmospheric one, fix it?

Another variable, I've also fitted the redesigned 3B maf hose which has the DV return at a different angle (aimed back up more towards the MAF)

[Acidburn]

Wonder if s2_bo has experienced anything like this, could be due to the power difference you have compared to him?

What is the difference with this set up anything good?

[newsh]

Well, the car definitely goes better, revs better, seems to breathe better. Not sure why i'm getting this surge though, I think the pressure in the system has changed and the DV is not opening so easily.

[Acidburn]

Have you lost or gained anything on the boost guage as I remember s2_bo saying iirc he did? Might not be as noticable with the rs2 setup.

[newsh]

Have you lost or gained anything on the boost guage as I remember s2_bo saying iirc he did? Might not be as noticable with the rs2 setup.

I'd say I've gained, I saw 2.2 Bar yesterday so I think I'd better back the wastegate screw out a turn.

[Acidburn]

What was you seeing before then (still getting used to bar as my guage reads in psi)

and this is on standard rods?

[newsh]

This is on SPM H beam rods. Around 1.9 Bar before.

Have this little converter.

[Jamo]

Well, the car definitely goes better, revs better, seems to breathe better. Not sure why i'm getting this surge though, I think the pressure in the system has changed and the DV is not opening so easily.

I would have thought this will be due to the increase volume in the intake tract due to the larger IC.

Now when the throttle is closed there is more air volume to remove from the system via the dump valve but your DV maybe to slow or can't flow enough of the air.

I would try a large DV or try a softer spring in the DV.

Maybe cobblers but thats how I see it.

[newsh]

I think that sounds right.

[Acidburn]

Let us know how you get on, any idea which one your going to go for? I currently run a turbosmart vent to air one which has a adjustable screw head on the top and allows me to adjust how hard or soft the spring is and helps with adjusting for idle.

[jogi730]

I think I kind of get the drift of what surge is, but what are the symptoms you experience whilst driving when surge occurs?
Cheers
Chris

[newsh]

Cured it!
This is not full on turbo surge I'm talking about, just a feeling that as you lift off the throttle the car carries on driving or even accellerates slightly, it only happens going from on to off throttle at cruise speeds, very light throttle openings, but its enough to check out how much shunt you have in the drive train as the car does a gentle lurch, annoying but not terrible.
This has now been completely cured. I've done 2 things though.. First I changed the DV to an almost new Forge item I was holding as a spare, the Bailey had been on there about 3 yrs, I cleaned it a short while ago but figured it might be sticking and or leaking. Secondly, I changed back to the original Samco 3B Boost hose. The original one had an issue with clearance between the DV return pipe and the IC pipe. Samco moved the DV inlet down to clear the IC pipe on later kits but I noticed it now aims back towards the MAF. My theory was that as the throttle was closed the DV was opening and blowing back up at the MAF. To truly prove this I'd have to swap back and see if it returns but the car is going nicely so I really don't want to