LARGE pressure spike problems
Turbo Mini Forums

This is a problem on the hillclimb single seater (Z750cc Kawasaki motor with a turbo).

What's happening is that I'm getting large pressure spikes. The result of these are that the TBs are being blown off, the fabricated plenum is blowing up like a balloon and on the last occasion the IC blew to pieces (plastic capped OEM one)

It's only started happening since I fitted a flat shift, this retards the ignition 50deg for 70ms and cuts the fuel by 35%. It seem the gear cut is causing back fires that the inlet system can't cope with.

I'm going to strap the TBs to the chassis/engine and get a new IC fabricated with weld on ends so it's more robust. Also I'm going to stick something like the below on the plenum, but I'd rather stop the back fires, while keeping the flatshift.

http://www.ebay.co.uk/itm/272263102962?_tr...K%3AMEBIDX%3AIT

Anyone any experience of similar issues? Or just general thoughts.

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

www.twin-turbo.co.uk

Try a different flat shift strategy you may be causing a burn with inlet valves open. I use a straight up ignition cut. No retard or fuel cut atall.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

I tried ignition cut. It sounded like a shot gun going off everytime I changed gear. I got my collar felt by the noise police after my first run.

But maybe less retard and more (or less) fuel cut may help. Just difficult to know which way to go.

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

www.twin-turbo.co.uk

Deffo try less fuel cut, I'm thinking if it's too lean the burn will slow down so it's still alight when the intake opens,

Also with 50 degree retard could this cause a back fire in to another cylinder... Could wasted spark cause this.

It is running wasted spark, but has 4 coils.

I'll try 30 deg retard and less fuel cut then.

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

www.twin-turbo.co.uk

Try more fuel cut !! on the cars I cut 100% fuel for the duration of the shift. That also sounds like a huge amount of retard ?

It also ensures enough power reduction for the dogs to actually disengage.

Edited by stevieturbo on 3rd Jul, 2016.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I had no reference to start from and someone said 50deg. From a gear change point of view the settings work.

I must admit 100% fuel cut seems a reasonable suggestion. It seems safer than a lean mix I think.

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

www.twin-turbo.co.uk

50deg, whilst not fully killing the engine sounds like a recipe for problems.

ie you're basically going to allow mixture to combust almost at the time the exhaust valve is opening which will in turn drive the turbine.

ie, anti-lag in a very aggressive form.

If anything, maybe pull 20deg or so of timing just to soften things and a much larger fuel cut to kill power to allow the shift to occur.

If you can also kill ignition too, then that may not be a bad thing either.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Wasted spark is your issue. Think of where the (no longer) wasted spark is happening. With that much retard, it is happening in the middle of the intake stroke.

http://www.jbperf.com/

Just trying to work this out. 30deg BTDC with 50deg retard is 20deg ATDC on cylider 1.

Therefore on cylinder 3 it's 20 deg ATDC on the intake.

Now I feel a bit daft.

I'll look at the ignition and pluck a number out of the air. but 20 deg seems sensible.

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

www.twin-turbo.co.uk

cyl4 ?

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

Is this what was hampering you at Barbon?
Did you get out again at Harewood?

All right clever clogs!

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

www.twin-turbo.co.uk

Barbon was an issue with the regualtor.

We fixed this and then had the pressure issues at Harewood the next day (not been a good year)

Edited by wil_h on 4th Jul, 2016.

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

www.twin-turbo.co.uk