Boost spikes

[youngsyp]

Hi again,

I just wanted to know if anybody else is suffering huge boost spikes because of the cold weather ?

I was out in the car on Saturday and accelerated onto the M1 from a slip road in 5th. The boost is currently set at 1.15 Kg/mm on my AVCR and it jumped up to 1.49 kg/mm, pretty much as soon as the turbo came on boost. :shock: Luckily, the throttle was only open 58% and I noticed it as soon as it happened.

I guess I need to get the AVCR to re-learn the boost curve, now we have the cold weather ?!

I have cleaned my air filter recently too and not had the car at WOT. It seemed to make a difference to how the engine picked up so, I guess this could be a contributing factor too ?!

Paul

 

[antgtir]

Are you sure all your vac pipes are sealed as it were?

Plus nothing is sticking such as Actuator etc?

The car will run smoother im sure of that as the colder denser air will aid combustion, however if your AVCR is set to 1.15 then it should stay at 1.15 (apart from the norm slight boost creep).

Id look around the engine bay to be sure nothing has slipped off, been pulled off during filter clean (you never know) or just plain failed.

Good luck.

Ant.

 

[youngsyp]

Yeah, a bit of a mongtard question really. :der:

I'll take the car out tonight and see what boost it makes on a 2k rpm upwards run in 4th. That will show if everything is working as it should.

I will say that the car has always over shot the target boost level when coming back on the throttle, once the engine is up to the right rpm to make full boost. Just not by that much before.

Paul

 

[G20_GTI-R]

I was having the same problem with my evc but i just adjusted the settings for the cold weather and i have it holding 1.2 now.

 

[youngsyp]

Well I checked all the vac hoses last night and couldn't see anything obvious so, decided to take it for a drive.

Loaded it up in 4th gear from 2k rpm and the boost pressure flew up to 1.66 Kg/mm :shock: .
So as a process of elimination, I turned the AVCR off to see if the actuator was sticking or open to atmosphere. Loaded it up in 4th gear again and it made 0.60 Kg/mm and held it steady. That rules out the actuator !

To rule out the AVCR solenoid valve, I set the AVCR to setting 'B' (1.05 Kg/mm). Again, loaded it up in 4th and it shot round to 1.08 Kg/mm then settled at between 1.05 and 1.06 Kg/mm. That rules out the solenoid valve then ?!

I then went through the settings for setting 'A' (1.15 Kg/mm) and and nothing seemed obvious apart from the fact that I'd moved the 'NE points'. So, at 3500 rpm the solenoid was at 90% duty (I stick the solenoid duty up to 90%, normally from idle to 3k rpm, to help spool up). That would explain the 1.66 Kg/mm but, I'd only done that last night.
I guess the overshoot at the weekend was due to the cold weather although, I will do some further testing at the weekend.

Sorry to bore you.... :lol:

Paul

 

[antgtir]

So with all the AVCR settings set back as you originally had them for Setting A does the car still overboost the set level? or has it stopped now?

Maybe its an intermitent fault thats just happened to coincide with other small changes? This does tend to happen alot lol

Ant.

 

[youngsyp]

So with all the AVCR settings set back as you originally had them for Setting A does the car still overboost the set level? or has it stopped now?

Ant.

I'm not sure as, I didn't test it. From the other testing though, I'm confident that it won't overboost any more. Logically, it shouldn't do unless of course, there's an issue with the electronics that control setting 'A'.... I very much doubt that though.
I'll have another play with it at the weekend, on setting 'A', just to confirm all is well.

Paul

 

[G20_GTI-R]

If you just set it higher you wont have to worry about over boost

 

[LOU ROB]

I had this problem many years ago, i think I just knocked down the duty in the winter time and it calmed the boost spike down. ( I cant remember as it was that long ago )

 

[youngsyp]

Just to close this one off, and to possibly help others....

Thanks for all the suggestions.

The spikes were indeed down to the cold weather and, due to me having the solenoid duty set to 90% up to 3k rpm, to help spool up.

The turbo seems to spool quicker in the colder weather so, by the time the engine is at 3k rpm, it's well on it's way to making full boost.

I just dropped the duty up to 3k rpm, back down to the same level as the rest of the 'curve' and the unit dropped the duty by 1% over the rest of the range, to compensate for the change in atmospheric conditions (clever little unit !).
It now spike to around 1.2 Kg/mm as the turbo hits peak spool and settles at 1.15 Kg/mm as before.

Paul