Boost spikes
Turbo Mini Forums

Ok well im having a bit of an odd issure that i cant find when i search the forum.

When driving everything is fine when off boost, but if i stay at a constantish RPM (can be any RPM though) when on boost iv getting boot spikes, where im loosing all power from the engine for a split second then it comes back.

I dont get this problem if the revs are changing, but if i stay at the same RPM for a while i get what appear to be spikes in boost pressure lose.

Iv taken a little video where it was at its worst where this happened alot in a short time. If you watch the gauge you will see the pressure flicking from on boost, this happens a couple of times in the video.



Has anyone got any idea what could be causing this problem?

Edited by mini=love on 2nd Jun, 2010.

your driving on two wheels ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Hi im not sure what you mean by that? i was driving down the road when the video was taken...

I think that was a comment on the angle of the video....

Normally boost spikes refer to random high boost. Low boost would be a dip. However, this is not important.

This could be any number of things. My fist guess would be to look at the fueling though. Does this happen after a prolonged period at a constant boost? i.e. are you emptying the float bowl of fuel?

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Lol,

what fuel pump you using? Does the car come on boost and stay on boost?

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
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Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I think robert has it, I can't see any other way to end up with vacuum unless you close the throttle.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

I thought the same about the vacuum, but I though that was at the end of the video and he had closed the throttle. I can't review the video now though as the link has gone..

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Edited by mini=love on 2nd Jun, 2010.

Regarding the pipes being sucked flat, Robert is referring to the main air inlet to the turbocharger from the air filter.

Thanks Tom, i will double check my air feed, it does have a metal wire trace all the way through to to try and eliminate this, but i guess it might be at an angle that folds it on itself cutting the air.

If this was happening though I would have thought it would be worse at higher boost and that appears to be fine.

My money is on fuelling, maybe a restricted float bowl valve, something like that. Do you have an AFR gauge that you can fit?

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

could it be a clogged fuel filter, or the std gauze on the in tank pick up if its standard?


*edit* just watched the vid and sounds like mine did when the gauze was clogged.

Edited by Nick on 2nd Jun, 2010.

have a read of this chap :)

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=150874

Ok a bit of an update on this, initially i believed the engine was loosing boost, but i have just taken the car out for a quick drive and its actually flicking to full boost and back.

I checked the pipes between the actuator and turbo and the pipe to the bleed valve. and there doesnt appear to be any leaks. i removed the hoses and there were not any splits.

Heres another video, im on two wheels again sorry, You can see the boost increases pretty clearly.

se if the wastegate actuator rod moves easily .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Possibly solved this, i just shut the bleed valve off completely and took it for a quick drive and i didnt experience the spikes once...

So i guess this leads to the bleed valve being faulty and somehow bleeding off more in very quick spikes then returns to normal.

But i guess the problem could be that its not building up enough boost to be able to see the problem, as i have to rev to about 4000rpm im getting about 1psi-2psi boost pressure...

Ill get a picture of the bleed valve im using and see if anyone has had similar problems.

Heres the bleed valve im using.

what turbo are you running? when i was running my T34 at 22 psi on mine the turbo was wanting to boost high but was running at about 1/4 throttle around 3500 rpm, this caused the turbo to surge which would give a drop in boost then a spike in boost.

Im just running the standard T3.

Well there goes the idea of it being fixed, its definitely not spiking anywhere near as often with the bleed valve fully shut, but it is still getting the boost spikes, i guess because it was producing more boost before it was spiking worse...

I checked the actuator arm iv never set one up before so im not 100% sure what its supposed to be like, but it didnt slop about, there was no movement towards the actuator and would pull towards away like its one a spring and if i let would would return to its original possition, i pressure this is how its supposed to be.

Also i noticed today that if going up a hill the engine would loosed power, but you could have the turbo spooling up as it does this...

have you tried removing the bleed valve altogether?

We had a cheep one fitted to our van, the end result was new rings

Really?

my N/A lump needs new rings, I might fit a bleed valve!

yep, very clever these modern bleed valves