20 psi running lean...

[gardner51]

Hi all. I'm runing a t28 turbo and Its set to 20psi, I went on the rollers yesterday and only produced 185bhp,

Matey said its because I'm running lean in the later part of the revs. As if the carb is emptying all fuel and can't deliver enough?

We drilled the main jet out and this helped a little but still running lean,

I apparently have a group a carb, what size is the Venturi (spelling) ment to be. I have a 25mm in

Any help for a newbie?

Ellz

[Penfold aka The Dealer]

Speak to Matt@coderedmotorsport.... He can help you set the carb up & is pretty local to you :)

[gardner51]

Is that his user name?

[Penfold aka The Dealer]

Is that his user name?


Yep :)
http://www.rtoc.org/boards/member.php?u=113

[BluntyR5GTT]

Im.pretty sure 25mm Is standard venturi. What size air corrector and what size 2nd stage do you have

[R5MJH]

25mm is standard but most group a carbs have the standard 25mm drilled out so id measure the venturi properly mate even thou its stamped 25 it may be 27/28/29mm

[gardner51]

Air corecter is a 90 I been told,

Not sure on the 2nd stage.

Ellz

[Sparkie]

Matey said its because I'm running lean in the later part of the revs. As if the carb is emptying all fuel and can't deliver enough?
Ellz


imagine you had a coke can with a 1.2mm hole in the bottom of it.
you then put it under a tap dribbling water out of it at a rate not quite enough to fill the coke can quick enough - so the water level inside dropped instead of rising.
then you make the 1.2mm hole into a 1.5mm hole and expect the water level to rise inside the can?
you really need to increase the amount of water entering the can.....


basically what you need is either a larger float chamber jet. - try a 2mm first of all.
or you need a one way valve with a 15psi crack pressure feeding fuel into the bottom of the float chamber.
this will stop the fuel emptying out of the carb quicker than u can put it in.

[gttjames]

When i was looking into this ellz i got told about the larger needle valve or got told to fit this to raise fuel pressure.... thoughts?

http://www.ebay.co.uk/itm/FUEL-PRESSURE-REGULATOR-TURBO-CARB-ENGINE-RENAULT-5-GT-TURBO-/200759911324?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2ebe39239c

[gardner51]

Cheers James, ill most likly go down that route as that's easy way to control fuel?

Any one else run one of these?

Ellz

[SCHWARTZ]

whats wrong with the standard reg? get an afr gauge on there before you do anything else.

[Tony Walker]

Also fuel filters a cheap item that should be changed. may not fix it but it should be changed and could be a restriction to the supply.

[gardner51]

whats wrong with the standard reg? get an afr gauge on there before you do anything else.

Have you read the 1st post.....

I.was on the rollers with a afr gauge and it was leaning out in the later revs, so trying to find out how to keep fuel in the carb...


Ellz

[Markey Mark (BD)]

Have you read the 1st post.....

I.was on the rollers with a afr gauge and it was leaning out in the later revs, so trying to find out how to keep fuel in the carb...


Ellz

Sounds to me like the carbs not set right thats why the afr's are leaning out.

If all you have done is drill the main jet out and fit smaller ac jet then thats one reason why the carbs leaning out

You want to go back to standard main jet, standard venturi (if you not got that already) and look into modifying the 2nd stage enrichment side and ac to make sure if keeps a good supply of full high up the revs

[Fordy]

what size needle valve?

[SCHWARTZ]

Have you read the 1st post.....

I.was on the rollers with a afr gauge and it was leaning out in the later revs, so trying to find out how to keep fuel in the carb...


Ellz

read between the lines. If the old reg aint broke dont fix it.
just sounds like carb settings, get an afr gauge on it to see what its doing.

[gardner51]

I have had an afr gauge on it and it leans of in the later part of revs,

It goes back in tuesday and matey is going to have another look at the jets and venturi and see what he can do,

Thank you for the replies will let you kno how he gets on

Ellz

[Tony Walker]

as previously stated, needs standard venturi standard main, drilled 2nd stage smaller air corrector and perhaps a larger needle jet..... tried and tested methods beyond 20-psi.