[NooNoo]

I've been Upsoluted and Forge DVed for about 6 weeks now and I still have a quirk! I have just tried Optimax and the problem still exists.

When easing off slowly in 3rd/4th gear and between 2500-3500rpm I get

a learch/snatch (like sudden engine breaking but worse). It's really off-putting and annoying. I noticed a few of you guys out there are Upsoluted and Forge DVed, anyone else have this problem?

It was previously so smooth to drive, now I'm just waiting for the "learch". [:O]

Its not a condition that lasts. It still accelerates really hard and smooth after these "stutters". They are very brief.

Any possible causes?

Its an 1998 AGU with 30000mls on the clock and has had a very easy life until now []

It is due for a service, not oil, I do Mobil 1 myself every 6 months.

Please help!

Thanks

 

[Si_1.8_GTI]

Mine does exactly the same since I had it Upsoluted. I've also fitted the N75J and the DV off the 225TT. I've got used to driving 'around' it if you know what I mean but I agree with you its very annoying and can't be doing the car any good. I'd be interested to hear if anyone has managed to solve this problem.

 

[david1.8t]

Mine is the same, AGU, Upsoluted with Forge DV. I did have a N75J, i took the off and it seemed to make it slightly better.

 

[PJ]

Me too. AGU, Upsolute, Forge, N75J. I've just got used to it as well but I suspect the N75J.

 

[NooNoo]

I have emailed Upsolute directly about this problem.

I thought I was alone with this issue, obviously not.

Hopefully they may be able to shed some light on it.

If anyone else is suffering, please post a reply here,

the more people that have the problem the more likely

we will get an answer!

I've sent them a link to this forum topic.

Overall though I like the Upsolute solution. My car is now

"interesting".

[?]

 

[cage]

I habe '99 AGU, Upsolute, N75J valve, Baileys DV, Stroeve Induction kit and don't seem to have this problem and I only use Optimax every few fill ups.

 

[NooNoo]

Unfortunately "Upsolute" are on hols until 22nd Aug, they

will be in touch! Hmmmmmm.

Maybe it the Forge DV / Upsolute combination.

Please others comment if you have a completely smooth throttle

response with the Upsolute map and a different DV to Forge.

I really want to sort this.

[]

 

[Starry]

my 1999 agu car was a1 smooth when i got it,if a little slow. so i got it revo'd after doing this it started to suffer this problem, it was not to bad neither was it all the time so i just got on with it and put it down to the revo. since then i have changed the turbo to a k03s and had a jabba costom map and the car still does it.so my thinking is, maybe its more to do with chipped agu's than just upsoluted cars.

Starry.......

 

[Malky]

Well mine does it, see here...

http://www.uk-mkivs.net/forum/topic.asp?TOPIC_ID=25813&whichpage=1

Sound familure???

As mine does it in stock code, it's not chipping that causes it... Maybe the dual mass flywheel??!!?? Mines going in for a service next month where I shall be demonstrating it to the master tech and want it evaluated...

 

[NooNoo]

My "stuttering" definitely occured after the Upsolute / Forge mod.

It was absolutely perfect before the mods 6 weeks ago.

Its ceratinly not the "surging" problem mentioned in the above thread.

Its a "jolt" when easing off (also mentioned).

There has to be an explanation and cure. When it happens its at very low boost levels so I don't understand why the car should behave any different from stock when easing off.

Need answers []

 

[Jonmurgie]

It's obviously not the Forge valve causing a problem though... stacks of people with Forge valves and no problems... guss you'll have to see what Upsolute say... me, I have my AGU AmD's and Forge'd and it's smooth all the way []

 

[PJ]

Quote: posted by Jonmurgie on 12/08/2004 23:03:11

It's obviously not the Forge valve causing a problem though... stacks of people with Forge valves and no problems... guss you'll have to see what Upsolute say... me, I have my AGU AmD's and Forge'd and it's smooth all the way []

Do you mean stacks of people specifically with Upsolute and Forge? Because there seems to be quite a few with Upsolute and forge who do have this problem.

 

[Mo]

Guys,

I did mention before that this is a common problem with many turbod cars that run higer than standard boost and a recirculating dump valve.Dumping hig volumes of boost back into the system can cause surging by disturbing the flow of the turbo.

Fitting an atmospheric dump valve is not all about the noise.

It should cure this problem if you fit a twin piston type valve up front by the inlet manifold.Cage does not expeience surging and this is probably because he has an atmospheric valve.

Not sure if DBW cars can use atmospheric valves but non DBW should be fine.

 

[Malky]

Chaps, this is not a chipping problem... It occurs on cars with standard boost levels. My problem is as you describe, easing off the throttle slowly or having to come of quickly. They both can vause the jolt effect. Happens with standard VW code and chipped REvo code on mine. With hyperboost dump-valve or standard and with brand new MAF. All all combinations of these.

It's much more likely to be engine mounts issue or the clutch/flywheel I think... Come on chaps lets put out heads together and solve it... It drives me mad...

 

[PJ]

Let me sit on the fence for a while.

Malky, let's assume for a while that your problem though giving similar symptoms is unrelated to the above mentioned problems. I say this cos I'm not aware of anyone other than you that experiences this problem in standard mode. (correct me if I'm wrong).

So if we dismiss Malky's explanation for a while, then Mo's explanation is the only one so far that makes any sense to me. As he says cage is running exactly the same mods as me except that I've got a ricirc valve and he's got an atmospheric.

If this is the case is there any way to replicate the action of an atmospheric dump valve? Perhaps removing one of the pipes so that the boost is dumped rather than recirculated.

 

[NooNoo]

This is an extract from another forum I found.

It sounds feasible....

Text Quote.

I have the exact same problem, most noticeable when accelerating 60% throttle in 4th gear at maybe 3500-4000rpm, and then rolling off the throttle.

But it doesn't happen all the time... maybe because I've adapted to only use full throttle more often, and to get off the throttle more quickly instead of rolling off slowly. Over time this symptom has taught me to use the throttle more like an on/off switch, unfortunately.

I don't think it's the ECU because a friend's mazdaspeed protege turbo also does this even at stock boost.

Mine didn't do this before I was chipped, but it Feels to me like something to do with the DV (I have stock DV). Could be the DV not opening soon enough to bypass excess boost when you start getting off the throttle gently. Because the DV needs an intake vacuum "signal" in order to bypass the excess turbo boost. If the DV doesn't open soon enough and yet the throttle butterfly closes, then the turbo's boost will slam into the closed throttle and stall quickly.

Probably why this only happens when I roll off the throttle slowly--the throttle goes ahead and closes (drive by wire!) but there's not enough vacuum to pop the DV if you roll off the throttle gently. But if you get off the throttle quickly, then vacuum occurs fast enough to pop the DV in good synchronization with the throttle closure, which allows the turbo boost to be bypassed appropriately. the more I think about it, the more I'm convinced this is the case...

Regards,

I think this could be it!

Now for a solution or test.

[?]

 

[Tabs]

I had the same problem on my 1.8T. Refitted the stock bypass valve the and problem magically went away!

 

[NooNoo]

So it has to DV related.

It must be the DV behavior under partially open throttle.

As quoted it may not be venting the turbo pressure as

there is not a rapid change in vacuum pressure in the intake.

The problem is made worse by "chipping" as the valve opens and

closes on the differential pressure between the top vacuum connection

and whats in the main pipe. Maybe retro-fit valves don't gradually open but always open with a snap action, suddenly releasing 10+ psi of boost back into the intake = jolt. This "big dump" LOL could also upset the MAF.

Maybe wot is needed is a smoother acting DV at the intermediate

pressure differentials? Probably more like how the stock part performs [!] Oh dear mines broke!

Anyone think this is plausible?

[?]

 

[NooNoo]

This is worrying...

Another extract from a forum post... discussing BOV and DV function.

Both valves operate via a vacuum source, and their sole purpose in life is to protect the compressor from being hit with a "shockwave" when the throttle plate shuts. The compressed charge is traveling well in excess of 100 mph when under substantial boost, and if it suddenly has no outlet, it will create a "backwards" wave, which will travel through the IC plumbing back to the compressor wheel. When the impeller is hit by this 'wave', it can stop and/or spin in reverse. Imagine going from 150,000+ rpm to negative RPM in the blink of an eye or so. Not a happy picture, and your turbo will get really slightly intoxicated off.

Maybe this is the jolt...

I suspect "our" DVs are not venting or partially venting soon enough when we ease off.

I really hope it isn't this. Doesn't sound good.

[!]

 

[PJ]

Quote: posted by Tabs on 13/08/2004 16:51:49

I had the same problem on my 1.8T. Refitted the stock bypass valve the and problem magically went away!

What other mods did you have Tabs?