My car is a UK MY99-turbo with Tek3 custom remap,full decat,panel filter,uprated fuel pump and Forge recirc dump valave. While cruising at a steady 80 mph(2900 rpm) for a few minutes any slight increase/decrease of speed brings about severe lurching of the car. If you ease off the throttle or indeed put your foot down it seems to sort itself out! It maybe lurches back and forth 3-4 times.
My thinking is the dump-valve as it didn't do this with the standard item and i'm thinking of returning to this but i'd like to understand what's happening.I've dismantled the dump-valve and regreased it and checked the o-ring condition is ok.I've also done the check they suggest on the Forge website,ie push plunger and hold finger over hole to see if it stays which it does.My current thought is the strength of spring is too high and the valve slams shut with any small easing of the throttle but why would it do it if you depress the throttle as well? Also why does it do it only after holding a steady speed for a little while? It's almost as if it gets itself stuck but as i've said i've regreased it and the o-ring looks ok.
Hope someone can help

PeteS

 

Anyone?

PeteS

 

I am running a Forge recirc on a modded motor with no problems. I have seen reference to the symptoms you've described on this forum but can't remember the outcome, sorry.

 

What sort of spec is your car and what colour spring have you got?

PeteS

 

The Forge recirc is running a gold spring but I wasn't aware that these needed tuning. I also have a Forge VTA that I use depending on how I feel and that is using a blue spring. Both have been great.

Spec:

UK MY95 Turbo
TD05 @ 1.25bar
Apexi Power Fc and Apexi Boost Control kit
Revolution 3" Decat Downpipe and system
Walbro 255 pump and FSE reg
K&N Panel filter with cold air intake
MRT Inlet Plenum Pipe
AVOTurbo TMIC

And probably stuff I've forgotten.

 

Your MAF (Mass Air Flow sensor) is down. Try cleaing it with some brakes cleaning product. If doesn not help you must get a new one.

 

Hi I've got a similar spec car, had the same problem maybe not so severe though. Car seemed to pulse when putting foot down at motorway speeds - I cleaned the boost solenoid with brake cleaner and it runs alot better now.

Greegs

 

what is a boost solenoid?

 

You could try a weaker spring, but it could well be MAF related. Does it have any hiccups at light load and low engine speed? I would say the red spring can be quite harsh.

Paul

 

This is quite a useful thread, even though Paul (Zen Performance) told me
off!

http://bbs.scoobynet.co.uk/showthrea...highlight=FMIC

 

Don't believe it's the maf as i don't have any other dodgy-maf symptoms. Do the different colour/strength springs apply to the recirc dump-valves as well as the vta ones then? Bought it second-hand of a scoobyneter so not sure if it came with the default colour spring (which is what by the way?).

PeteS

Thanks for the replies so far!

 

Forge is a good DV. Change, of spring on customer car transformed fast cruising

 

I believe the order of the springs are

green (weakest)
yellow
blue
red (strongest)

You can also get shims to tune them further.

 

Pretty sure we fitted a yellow spring (paint was mostly gone) with 2 thin shims, replacing the red with 2 thin shims.

Paul

 

Right had it apart today and it's got a yellow spring.Also cleaned it out and used a different high-temp grease in it.
Was able to rig it up to a pressure/test type tool and it seemed to slowly open as you increased the pressure and then would suddenly fully-open. After cleaning and regreasing it seems to open more progressively.
Does any of this make sense as haven't been on a long motorway type trip to test it.

PeteS

 

Zen are you there?

PS

 

Anyone?

Is the yellow spring appropriate for my level of mods? (tek3 custom remap,full de-cat,panel filter,high-flow fuel pump-270/280ish bhp)

TIA

PeteS

 

No-one know?

Any help greatly appreciated.

PeteS

 

Was there a reason for replacing the std item?

If not, and assuming you still have it, put it back on. I'm running a MY00 with similar figures and have had no issues whatsoever with mine.

I tried a Forge VTA once but the jerk coming off throttle/boost was just plain annoying.

 

The OEM one broke(the nipple bit cracked at the base)so i had a choice of second hand forge off sn or a new oem one for about the same price.

Pete