Boost cut...

[andy10v]

I would also check DV (depending on how you leak test if you pressurize both sides you don't simulate how it is under boost)

What were the old and new chips?

[Colesy]

Why are you asking about the rev counter going to zero and then back up.

I've had this happen maybe 6 times in as many years. It seems every couple of years it does it a couple of times. This has been with several different sets of chips. Very strange but so intermittent that I haven't looked into fixing it.


Boost cuts have nearly always ended up being a boost leak or MAF related for me. But my most recent boost issue turned out to be a weak coil/pos. It ran fine up to 1.6bar boost where it would seemingly hit a wall and just couldn't get past it. Drove me mad doing boost leak tests etc. So could be worth checking the coils as the symptoms were very similar.

[Rusty]

MAF plug cleaned, wastegate actuation checked, spark plugs checked (unrelated yo this but after one flew out...) and finally USV sealed with epoxy (no idea if it was leaking but can't hurt).

Final thing to do is to get a proper 2 bar leak test done when I have access to an airline.

[mike74]

Final thing to do is to get a proper 2 bar leak test done when I have access to an airline.

I've always wondered about the need for an air compressor to do this. Surely if there isn't any leaks you should be able to build up pressure with a foot pump and if you can't build up pressure you'd hear it leak regardless? I've managed to do it this (manual) way on another car ok so was just curious...

[Rocco]

1 bar leak test is enough

[Rusty]

It runs 1.5 bar fine, it's 1.7+ when it has cut a couple of times and triggered the over boost code.

[Rusty]

So just burned some more V power (hard life, isn't it) and no cut, which is progress. Car flies over 4.5k but still seems different to before when coming on boost; of course, that could just be a different boost profile to get used to. I took a video or two of the gauge, while watching the road of course, so will analyse that.

With my foot on the brake and in 5th gear, it holds 1.8 bar on the gauge with no flutter, which is nice.

[Rusty]

Had this again this morning

Did it once at the top of 3rd, having run through the gears and then to confuse things, after turning it off and back on, it didn't do it again during a couple of runs in 2nd. Checked a load of things and bought some deoxit for plated connections.

Need to do some more testing, cleaning and checking, as ADI is coming up and I have a full day booked. Pants.

[newsh]

My bet is either boost leak or Maf connector.

Have you done the whole Maf connector clean ritual? Including popping out the pins and getting between the mating surfaces with 1000 grade?

[Rikki Kitto]

With my foot on the brake and in 5th gear, it holds 1.8 bar on the gauge with no flutter, which is nice.
What is the reason for holding the brake in 5th

[newsh]

Just thinking, as you said you got a fuel cut at the top of a gear.., your setup is probably more efficient than a standard RS2 so it may be that you're getting more actual boost than requested boost at high rpms, the boost should taper off at the top end to avoid overspinnung the turbo. If the ecu is requesting 1.5 Bar at 6k and you're seeing 1.7 then you may get cut

[newsh]

Also Andy, is this a hard MAF cut (head hits windscreen) or is it just going into limp? Or both?

[Rusty]

Also Andy, is this a hard MAF cut (head hits windscreen) or is it just going into limp? Or both?

Hard cut.

I'll try the MAF clean and also have checked all pipes and done a basic leak test.

[Rocco]

Overboost?

[Rusty]

MAF & connector are prime candidates TBH, as it boosts fine most of the time and the needle doesn't flicker about. Need to do a proper leak test with a compressor but not got access to one locally, so either head over he other side of Bristol or to a friendly garage further afield.