bit of advice on fuelling please.

[jamie_clioGTT]

hi all..

running a t2 at about 14-15 psi,
afr readings flat out are around 12.5,
a fith gear pull flat out im seeing around 13's

what is best to do to my carb to allow for the extra fuel?
im hoping to run it at its limit 16 psi,

do i need to just drill the main stage out a small amount?

thanks in advance.

[James5]

hi all..

running a t2 at about 14-15 psi,
afr readings flat out are around 12.5,
a fith gear pull flat out im seeing around 13's

what is best to do to my carb to allow for the extra fuel?
im hoping to run it at its limit 16 psi,

do i need to just drill the main stage out a small amount?

thanks in advance.

2nd stage needs slight adjustment, what size are your current carb jets?

[jamie_clioGTT]

thanks for your reply,

sorry i should have stated they are standard.
i have read the guide on here but the use of big words confuse me

[GTphil]

The second stage enrichment is behind the triangular bit that is on the side of the carb, held in place with three screws. Take that bit off then you will see a small hole with a brass insert. That's the bit you will need to open up slightly with a micro drill bit, you can do it with your fingers just take your time and use plenty of carb cleaner.

I forget what it is as standard and what you would be best drilling it out to. Mine is 1.4 mm but that's for 22psi plus.

[Mart]

afr readings flat out are around 12.5,
a fith gear pull flat out im seeing around 13's

What's the fuel pressure @ carb inlet like at wot in 5th?

[jamie_clioGTT]

thanks alot phil! just what i needed.

mart im really not sure but i dont understand why i get diffrent readings in fith as the engine is still doing the same amount of rpm ?

if somebody could hazard a guess as to what size to drill it out to that would be smashing

once again thanks for your help chaps

[Mart]

Because the engine is under a more continued load in 5th, and if your fuel pump is struggling to keep the float chamber full, then the fuelling would naturally start leaning off.

Check pump & fpr condition/output before cracking out the micro-drill set...

[jamie_clioGTT]

fantastic, thanks alot mart.

[jamie_clioGTT]

tryed a diffrent fuel pump and regulator today,

i got 12.5 at full throttle in all gears and 12.7/8 in a fith gear pull.
so it helped a little,

would an adjustable fpr help me do you think?

thanks.

[Phoenix Autosport]

back in the day didnt they used to fit a single injector activated by a boost pressure switch to increase fueling at high boost where the carb couldnt quite keep up, bit of a bodge by modern standards but you could use a basic programable injection ecu to map additional fueling as required

[Markey Mark (BD)]

I'd increase the 2nd stage jet alittle bit now mate, 14-15psi is right on the limit of the standard jets so the leaning out you are finding would prob be down to jets now that you've checked all the fuel system over

[jamie_clioGTT]

back in the day didnt they used to fit a single injector activated by a boost pressure switch to increase fueling at high boost where the carb couldnt quite keep up, bit of a bodge by modern standards but you could use a basic programable injection ecu to map additional fueling as required

do you have any more information on this? sounds very intresting!

thanks for your reply mark.. could you take a guesstimate of what size to drill out to first please?

also what do you think to the idea of an adjustable fpr? any good for the c1j?

thanks again..

[Markey Mark (BD)]

thanks for your reply mark.. could you take a guesstimate of what size to drill out to first please?

also what do you think to the idea of an adjustable fpr? any good for the c1j?

thanks again..

I would start at the smallest increase, go 1.1mm and see how it performs

I would only use an adjustable fpr when going high boost and avoids using a larger needle valve which sometimes cause the car to bog when changing gear.

The injector set up which has been mentioned, that was an old tuner set up that they tried to keep the carb bowl full at high boost not really the way to go

[Brigsy]

Increase the 2nd stage a little. 1.2mm should be enough

[jamie_clioGTT]

thanks chaps

[Mart]

tryed a diffrent fuel pump and regulator today,

i got 12.5 at full throttle in all gears and 12.7/8 in a fith gear pull.
so it helped a little,

I'd leave well alone.

Mid-high 12 afr is fine at that level of boost, assuming you're on standard ignition timing.

[jamie_clioGTT]

even better

thanks mart, i will increase it when i get a new turbo then.

i do love this forum

[Mart]

If sorting/improving the fuel pressure has now helped richen the afr when on (constant) 5th gear load, then there lies ya answer.

Worry about enrichment mod's when overall on-boost fuelling is lean, not just at top end/continuous full load - If lean there, that points more towards fuel supply (read float chamber emptying)...

[Matt Cole]

tryed a diffrent fuel pump and regulator today,

i got 12.5 at full throttle in all gears and 12.7/8 in a fith gear pull.
so it helped a little,

would an adjustable fpr help me do you think?

thanks.

Mart suggested you checked your fuel pressure, not change the pump and regulator?

As suggested, leave the carb alone at that boost level. Adjust second stage slightly for more boost if needed.

[jamie_clioGTT]

and what better way to check the two things that affect fuel pressure than by replacing them for known good ones?

[Matt Cole]

and what better way to check the two things that affect fuel pressure than by replacing them for known good ones?

I'ts a bit of a time consuming method of testing fuel pressure when a simple pressure gauge would have saved you the hassle.

[jamie_clioGTT]

very true but as i didnt have one to hand this was the cheapist way

do you think it would be worth while plumbing one in? permanently.
or is it something not worth going to the trouble of?

[Matt Cole]

very true but as i didnt have one to hand this was the cheapist way

do you think it would be worth while plumbing one in? permanently.
or is it something not worth going to the trouble of?

I would plumb one in for the purpose of tuning mate especially when upping the boost but not really needed as a perminant fixture.

[jamie_clioGTT]

thanks for the advice! ill get on the case and buy one.

[Tony Walker]

pump and reg may not of been the problem, fuel filter is the cheapest and easiest thing to change with a low pressure issue

[jamie_clioGTT]

as silly as it sounds that did not even cross my mind!

could do with changing anyway i think.

thanks.

[Tony Walker]

No problem, always worth changing anyway