GMcM

All,

Just wondering if anyone has experienced a shudder when changing from 1st into 2nd when you've floored it in 1st gear. I've only had the car a few days and I can never seem to get a clean bite for 2nd at speed, is it the clutch or has anyone any suggestions?

Its a standard MY99 UK Turbo with 23K on the clock...

Cheers,
Geoff

RB5320

current car is an RB5 prodrive, so basically same as yours. does exactly the same, as did my previous MY99 UK turbo. also, its not just between 1st and 2nd. not entirely sure why (although it has been suggested that changing the dump valve might help by allowing the turbo to spool up quicker). sorry I cant help more but at least there is nothing wrong with your car. will be interested to see other replies from more technically minded people.

Steve

dodo

Just a thought // are you hitting the rev limiter
Easy to do in first.

GMcM

No not hitting the limiter, but probably about hitting 6,000 rpm before the gear change.

Moles Dad

Probably the drive shafts about to give up

Jaay

Mine has, god I cant wait for the new ones to be fitted it was like driving with faulty bushes or knackered strut. Nasty !

g60stu

My 99 UK turbo (totally standard) has exhibited a problem similar to the one you're describing. After giving it some welly (say just over 6k rpm) and changing up a gear, as soon as I put my foot on the accelerator I get a nasty jerk (someone described it as the same symptom as fuel cut). It very apparent in 1st to 2nd and 2nd to 3rd and occurs sometimes 3rd to 4th. This only happens when I'm doing quick gear changes.

I went to the main dealer about it the other day. The mechanic test drove it and did some diagnostics and reckons the MAF needs replacing. I'll find out tomorrow if a new MAF fixes the problem.

I'm not sure if you're describing the same problem but it sounds familiar and I'm confident that the problem I get on my car is not a characteristic of the MY99, but rather a fault.

Stuart

GMcM

That sounds similar to what I have, like a lot of these things, its hard to put into words.

Basically, 1st gear floored hitting around 6000+ rpm, clutch in grab 2nd, releasing clutch, flooring it and then the brief but noticable shudder before the car accelerates away normally. The shudder is almost like the car has broke traction.

I havent noticed it going into 3rd, 4th or 5th but then there's not as big a load released into the transmission through the higher gears.

Stuart, I'll be interested to hear what happens when you get your car checked.

Geoff.

g60stu

OK Geoff,

I'll let you know the outcome. Luckily I reported the problem with about 6 days left on the warranty!!

Cheers
Stuart

DaveMcC

Geoff

I too have exactly the same "characteristic" on my MY00. Only notice it changing up to 2nd and only if the revs in 1st are >6000 before the change (and no I'm not hitting the rev limiter. It is possible to avoid this by "careful" use of the clutch - basically let it slip slightly as you re-engage it - the technique was shown to me by my dealer driving my car. Not very keen on doing this so usually change up just before 6k (esp. as not much useful happens after 6k in any case).

Wasn't very impressed with this trait though - I've owned several performance cars before this and never had this (incl. a GTI-R, so don't blame it on 4wd or turbo!) I would be interested in seeing a Delta Dash analysis of what is actually happening - it certainly feels like an overboost resulting in momentary fuel cut - hence possibly the suggestion above that a different dump valve may cure the problem - though nothing to do with spool up of turbo but to do with making sure inlet manifold pressure is released properly whilst the throttle is shut.

If anyone finds a cure, I'd love to know!

Dave

Suresh

Indeed, experience the same problem on my MY99 with 25k miles, though never had it on my old MY95 with 80k on it.

Having the car TEK 3'd at the end of this month by EMS who hold the franchise over here in Holland. I'll mention it to them and see if anything comes out of it.

Suresh

g60stu

I had the air flow sensor replaced on my motor this morning. First impressions don't look hopeful. I still had the problem when changing from 2nd to 3rd. It's difficult to test this sort of thing out at 9:00am because of traffic so I'm going to take the car out for a good run tonight to see whether it's still the same.

As has been suggested, I get the feeling it is more to do with overboosting/fuel cut/dump valve.

Question: my car was delta dashed last week. I'm told that a standard MY99 should have peak boost of about 13.8. The max reading out of the delta dash on my car was more like 12.8 and only once did it get to 13.2. This would contradict the overboosting theory wouldn't it?
I guess this is complicated stuff and there's probably other contributing factors.

Stuart

DaveMcC

but did you log at the point you did the gear change and got the fuel cut/lurch?? - that's the bit which will prove or (more likely) rubbish my theory! If it is overboost related fuel cut, I'd expect to see boost over the fuel cut threshold (about 17psi IIRC) and also the injector duty cycle dropping to 0 momentarily.

Dave

g60stu

Dave,

YHM (delta dash results from my car). Can you draw any conclusions from them?

Cheers
Stuart

GMcM

Guys,

Just wondering what the latest was on the possible resolution of this?

Cheers,
Geoff

DaveMcC

I'm no expert, but I can't see anything odd on Stuart's DD log - there's no sign of overboost or fuel cut. Beats me what causes it!

Dave

MGJohn

Hi All,

What happens if you change up at a little below those revs from 1st to 2nd? Say by lifting off at 5-5500 rpm in first, quickly selecting 2nd THEN flooring it up to NEAR full revs before changing to 3rd ..... try and see what results are ... does it still do it?

My turbo (not a Scooby) performs best if I do not go max revs in 1st but do so in 2nd and thereafter. No idea why .... a quirk of turbos? Revs maybe actually higher than indicated as get there too fast .... just guessing ?

When driving friend's car got to max revs in 1st and 2nd so quickly that the rev limiter came into play - which sort of defeated the object .... :-(

GMcM

Even changing around 5k rpm there is still a shudder for a fraction of a second while accelerating away in 2nd.

I'll get the dealer to have a look at it.

Andy.F

Interesting this

I experienced exactly this when driving John Banks's car hard, I was logging an acceleration run on the AP22 performance meter and doing 'quick' gearshifts at approx 6500 rpm, each shift was followed by a 'hiccup' just like fuel cut but only less than a second duration then it pulled properly. I checked the AP22 data and it showed up clearly as a total power cut for approx 0.5 seconds immediately after a gear change
John ran the same routine but with his own style of shift feeding the clutch in more gently and the 'hiccup' dissappeared ????
weird !

Catalunya 051

Is this rubbish? maybe maybe not here goes....

Lots of boost up to ~6k rpm, then lift off and dump clutch for gear change to 2nd, wastegate dumps boost back into exhaust, pressure suddenly high on wrong side of turbo, maybe this is stalling/trying to slow down the turbo so that you are getting turbo lag until wastgate shuts and dumped boost pressure reduces compared with exhaust gases driving the turbo???

It may all be cow poo, just chucking ideas into the pan...