Thanks to Robert for advice regarding fuel starvation on the van.
Turbo Mini Forums

Just a short TY and a bit of a dit on Lessons Learned. Certainly for me anyway.

Very big thanks to Robert who took the time to discuss and give top advice to me when I met him at Beaulieu Cooper Day a couple of weeks ago.

The problem I have had with the van since finishing its build last June 2008 has been one of massive fuel starvation when coming on boost, this despite embodying the 'Tee Piece Trick' and clamping the Part Throttle Lean Off Pipe. It even baffled Stuart Gurr when I was on the dyno last September and the issue has been getting me down big time to the point of nearly giving up and fitting twin HS4's.

Until tonight that is when I undertook a very simple bit of boost signal re-plumbing and sorted the issue big time.

The fundamental reason I had been having problems is that I had used the brass connector on the compressor snail as the source of my boost signal to the Fuel Pressure Regulator (FPR) rather than the small outlet pipe on the plenum which I was using for other stuff.

Easy enough mistake to make in my book. Especially as my little brain thought the pressure coming directly from the compressor snail brass connector would have a higher pressure than the plenum as it had fewer losses due to the fact that the air did not have to pass through the intercooler pipework and intercooler and all those bends !

Not strictly correct and the van is proof of that having caused me no end of grief.

I thought I'd capture what I've learnt from some bloody good advice.

This was to ensure that :

1. One of the two outlets on the brass connector fitted to the compressor housing should be permanently blanked.

2. The other outlet should be connected to the actuator via whatever boost controller / bleed valve you are fitting, if at all. I'm using a GReddy Profec B2.

3. The signal to the FPR should always be taken directly from the small plenum outlet pipe, preferably replicating the standard setup which senses pressure before the plenum restrictor (hence at a slightly elevated pressure than the manifold pressure).

The outlet pipe should also feed the signal to the Dump Valve, or the DV should at least have its own line from the plenum. Importantly, the signal to operate the DV needs to be before the throttle disc rather than after it in order for the operation of the DV to be effective in preventing compressor stall and maintaining the RPM of the rotating shaft.

In order to give me a chance of sorting the problem, I borrowed Rob H's plenum (Ta Rob) which is one of Nick R's manufacture having the small signal outlet pipe on the rad side of the plenum rather than the standard MG Turbo Ali unit that is fitted on the clutch side. This has been extremely worthwhile.

4. The boost signal to the ECU (whether Megasquirt or standard MG Turbo etc) and the boost gauge, should be from the manifold after the throttle disc and preferably 'as close to the inlet valve as possible'.

5. That ideally there should be individual plenum outlets and individual manifold outlets for each signal line going to each individual piece of hardware, rather than using Tee pieces. This aids fault diagnosis and operability.

After re-plumbing the FPR signal line to take its feed directly from the plenum and by reinstating effectively a standard MG Turbo carb setup (ie removing the Tee Piece Trick and unclamping the PTLO pipe), the difference is absolutely remarkable.

I managed to hold 12.5 psi in all gears at an AFR of around 12.3:1, for about a mile. Nearly shit my pants.

Tomorrows test (that'll be today then) is to drive it 25 miles to work and 'give it some' up the hills on the way.

Things are very much looking up.

Thanks again Robert.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Point 3 second paragraph is wrong. The DV should have its signal from the manifold, after the throttle disk, otherwis it'll do bugger all.

The actuator should have it's signal from the plenum, which is not mentioned above.

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

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Curses, Robert is right again

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

Will, Ben, Robert - thanks for the points of clarification, I'll make sure they're incorporated on the van.

Ben - the post with the pics is just great, thanks very much.

Happy days.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Will, Ben, Robert.

Made the changes you suggested.

Made a huge difference, particularly DV operation which is now very audible - certainly wasn't working like that before.

Might even try my own DIY Meastro modded plenum again before handing Rob H's back. If the modded plenum (with restrictor ring) is still crap, then I'll be sure to order one from Nick R.

Fuelling wise its a little lean at part throttle on an incline so I think now its mostly sorted than its a good time to hand it back to Stuart Gurr - the first session did not exactly go according to plan. I've got high hopes this time around.

Thanks for your help again. Much appreciated.

Cheers.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u