Carb 1st stage question

[ranj]

I am using a gt28r turbo and if i floor the go pedal the afrs drop to 10.1 before they lean out .... also sometimes when accelearating from a standing start they go as low as 9.9 and the car fluffs then picks up again as the afrs lean out and revs increase .... so i am going to increase the stage 1 jet to 1.2 and see what effect that has ..

Question is that will altering the stage 1 affect my WOT ????

How large do people go on with the 1st stage .... ?

My spec of carb is 1.3 main , now 1.2 1st stage , 1.4 2nd stage and a 1.0 a/c ... fuelling for max boost of 24psi manifold.

[Woznaldo]

I think, if anything, you want to go the other way with your first stage. I tried increasing mine while trying to get a 110 main to work for MPG (couldn't get it to work for me but that doesn't mean someone with more experience can't) and the result was black smoke at low boost. Not good.

I now run the std 120 main, 1.2 2nd stage and 0.8 1st, as when the std main went back in, it was still very rich. Reducing the 1st to 0.8 improved things but, it's still not there yet.......

[Sparkie]

i always thought that the 1st stage opened when the vac/boost gauge just read zero. - inbetween vac and boost.
With a t28 it takes so long to come on boost compared with a t2, it spends along time in that vac/boost=zero zone, then you have to reduce the size of the jet else it runs rich and isnt smooth.

[ranj]

it seems i have totally misunderstood the 1st stage .... i should be reducing its size to make it fuel less when just coming on boost .... because thats the point that its overfueling .... will have to order a 0.9 a/c on monday.

Just checked the jet i took out ... i presumed it was a 1.0 but in fact its a 1.1 !

At WOT ... does the 1st stage jet have no affect on the afrs ??

[michael tierney]

make sure ur not reading the accellerater pump richness when u plant the pedal initially....check to see if its leaking around the pump nozzle!the first stage will actually come in before the guage reads zero.

[Woznaldo]

I would just solder the original and redrill to 0.8mm.