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Home > Help Needed / General Tech Chat > 1293 turbo build teething problem

citykie

7 Posts
Member #: 11879
Junior Member

Hey all, 5 years into my summer project I've finally got my mini turbo running and kinda drivable.

I've struggled with loads of stuff over the build but now is all falling into place. I've got the Interior and arches left to fit then an attempt at an MOT will be had.

The engine was set up on a bench dyno but I've changed a few things since.

I'm now running a Avonbar electronic dizzy ( it was an Avonbar points based previously) I've gapped out my sparks to .75mm.

my prob is that on part throttle the engine seems to be misfiring and confused what to do. As soon as I'm on full throttle the boost kicks in and ...the thing bloody fly's ! currently running .7bar I've got a bleed valve fitted to a Mambo actuator.

I was wondering if anyone could offer any advice, i was thinking perhaps the plugs need a slightly larger gap.

Carb is set for 14psi as is the dizzy, i plan to run no more than 12psi...

The car is gonna be absolutely crackers once finished it pulls really well struggling for grip in the dry !

thanks all Kieran



Mr Joshua

2484 Posts
Member #: 1954
Post Whore

Luton Bedfordshire

What have you set the fuel pressure regulator to at idle should be 5psi if memory serves. The carb gets what the pressure regulator sends it the turbo fuel pump is capable of 9bar of pressure so your carb will see varying pressure as boost ramps up. Over fueling may be your issue.

Own the day


citykie

7 Posts
Member #: 11879
Junior Member

thank you, I'll get a fuel pressure gauge sorted and check this. I do not know what fuel pump they used on the bench testing.


minimole23

4300 Posts
Member #: 1321
Post Whore

Wiltshire

Any more details on the fuelling system?

Assuming you are using a metro turbo pressure regulator?

On 7th Oct, 2010 5haneJ said:
yeah I gave it all a good prodding


citykie

7 Posts
Member #: 11879
Junior Member

yep using a standard MG metro turbo fuel regulator and pump. But I think Mr Joshua is on to something, I don't know what fuel pump was used during the bench set up or the size of the fuel lines etc, I think switching those would affect pressure.


Mr Joshua

2484 Posts
Member #: 1954
Post Whore

Luton Bedfordshire

I run 10mm feed and return, going smaller can run you into problems like fuel starvation due to stall in the fuel pump.

Its the flow and the pumps ability to achieve 9 bar that allows fuel pressure to me modulated at the carb as boost pressure rises. As long as your pump is not producing so much flow that the return line develops a back pressure your fine and seeing as your using the original style pump for the metro turbo your fine. You just have to make sure your feed and return are of the correct size.

Own the day


citykie

7 Posts
Member #: 11879
Junior Member

I tested the fuel pressure at tick over today, 6psi ! I reduced it down to 4.2 and it runs a lot better ! I'm still getting a hesitation on part throttle then boom, off she goes !

I have 10mm copper pipes running under the floor but I think my rubber lines are 8mm, I'll check em. The boost is reduced down to 5psi for now whilst testing.

I've redone some of the boost pipes to be sure the intake isn't leaking

Thinking of trying the original refurbed MG Metro turbo Dizzy I have to discount that and go from there.

Fuel lines are also on the list, I remember reading lots before I installed it but it was a good while ago.

Still wondering is a 0.75mm spark gap enough ?

thanks all Kie













Steve220

240 Posts
Member #: 11017
Senior Member

Shropshire

0.7mm gap is about the norm. Only run larger if your ignition system is powerful enough.


Mr Joshua

2484 Posts
Member #: 1954
Post Whore

Luton Bedfordshire

What are the bore sizes for the feed and return? A good way too look at is to look at the pump your using, the supply line from the tank needs to be the same internal bore size or bigger than the the input into the pump, same applies for the return, that needs to be a larger internal bore than the exit out of the pump. fuel pressure reg needs to be set at 5psi.

Also consider the oil in your dash pot I had to up mine to 40 weight silicon which is fairly thick to stop it bogging down. Why silicon you may ask, ill never drive it when its that cold and if the engine ever gets that hot engine is toast.

Own the day


citykie

7 Posts
Member #: 11879
Junior Member

The copper is 10mm ID 8.9mm, the rubber pipe ID is 8m for both send and return. I have the 10mm ID rubber here already but I stupidly bought my 12mm ID 11m copper from China... 3 week wait. I'll get that sorted as soon as it turns up.

Dash pot oil I've not even considered.... I took the dash pot off (dome thing 3 screws with a screw top and bracing ring) a few weeks ago to check for debris. no oil escaped. I didn't see an...carbs are black magic to me !

@Steve I'm running an Avonbar (before minimine) electronic turbo dizzy .... is the advice to gap to .7mm ?

thanks all. I'm able to get things i would never of dreamt i needed to checked out !



Edited by citykie on 8th Apr, 2024.

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