T Piece Trick Working but Question
Turbo Mini Forums

I have been working on setting up my engine and after sorting out a few problems with the fuelling I got to a point where at 90 at full boost 12psi it was struggling. I used the T piece trick. Now great.
I noticed now my dump valve hardly works.
Question. When lifting off the throttle before, the dump valve dumped the boost pressure.
Is that pressure now going to the float chamber? If so is that detrimental?

I presume that you have T'd into the vac signal for the dump valve.

Try taking a separate signal. Actually the T piece trick should take it's signal from the plenum.

Photo might help.

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

www.twin-turbo.co.uk

Hi
I have Teed into the plenum to fuel reg pipe

Quick photo

Oh well I tried.
Will try again

there

Got to go to work now

Where are all them pipes going???
Try a different angle image; I can't make out what's going on there.

I think a diagram would be more helpful. That's a proper rats nest. Lol

In the 13's at last!.. Just

Well it looks about right, so I can't see how the T-pice trick could have affected the dump valve operation.

However, the dumpvalve looks like it's connected to the standard vac connection on the carb. This does not always have enough suck to open the dump valve. A direct decent sized feed from the inlet manifold would be better.

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

www.twin-turbo.co.uk

It is a bit busy I admit. I will try and do a diagram.

This is how its connected. Apart from the loss of power at 90 it has worked fine all the way up to that. The T piece cured it and made it run even better but now little or no dump.
I have not been able to concentrate on it at the moment. Wife, kids, cat, dog, work, everyone wants my time so bear with me replying to comments. any spare minute I am on it.

Swop the dump valve feed from the feed it's on to the boost gauge feed. That should do it.

The little vac feed on the carb has little or no flow; not enough to open the dump valve quick enough anyway.

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

www.twin-turbo.co.uk

Ok I have done that and the dump valve is working again.
The boost gauge though, where the original way around showed minus 7psi + with the throttle closed, and zero at steady speed and boost at full throttle, it now reads zero with the throttle closed and steady speed and boost on full throttle with slower reaction.
The new way around the signal to my Amethyst module is now what was being sent to the boost gauge so different to the original.
Should I worry?
I know little about the amethyst system I had it set up at TMS Knaresborogh. It seems to work great.

The original distributor vac takeoff on the carb is right where the throttle disc is, when the throttle is closed the takeoff is actually on the other side of the throttle disc and doesn't see the manifold vacuum. When the throttle starts to open it swings past the vac takeoff then is sees vacuum. I don't use the takeoff for anything, I blocked it off and made another takeoff in the carb spacer.

So at the moment it is reading different values.
Not a problem as now I know why.
That take off is originally for the vac advance so I suppose that's why its in that position.
Wondering how it effects the ignition module?
I can also fit a take off in the spacer.
Do I really need a dump valve?

Good enough

It might be a silly question but.
Going back to the t piece trick why would it alter the way the dump valve operated?

No idea.

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

www.twin-turbo.co.uk

I'm not 100% sure on this and it probably makes no difference to operation but I would have thought that the recirc valve you have there has the wrong connection to the plenum, If I'm correct it should be the one that's pointing downward connected to the dump takeoff, the pressure helps push up the valve faster during dump.

That makes sense. I'll try that tomorrow.
Although I know there is debate about the way round they should be fitted.

An update to finish the thread.
I have solved the problem. (dump valve not operating after using the t piece trick)
I have left the connections as I originally had them.
The difference is, instead of teeing off the connection to the amethyst unit for the dump valve I now have the dump valve teed off the connection to the boost gauge This now works as it did before I used the t piece trick.
I now have 12.2 AFR at full boost 12 psi at motorway speed so I am happy to give it plenty of right foot.
Thanks for the input everybody.

Edited by ERA1028 on 28th Aug, 2014.

also one thing to note is
when cruising with a bit of vacuum that dump valve may be slightly open letting the engine breath dirty air