increased boost

[cook1981]

Another newbie question, can you turn up the boost on a standard setup any using the actuator arm without altering the fueling, I've been trying to read up on it, and have found conflicting reports, the car is just over 9psi at the moment, I've read the fueling needs altered over 14/15 psi, if I was to up the boost to 12psi thus giving a 30% increase am I likely to blow up the engine, has anyone done this in the past with success or does it usually end in disaster, all input welcome thanks

[BluntyR5GTT]

at the 2 recent dyno days iv sorted out, cars running 10-12 psi have been fount to be running really lean. now this was either due to the carb needing be set up or the carb needing a rebuild or maybe a combo of both?

if the carbs not been rebuilt for a while id look at doing that first and give all the jets etc a good clean through.

[jamie_clioGTT]

im running 18psi with a t25/t2 on standard carb with afr's of about 12.3..

[GTphil]

Bluntys on the money here, re-building/cleaning the carb is most definatly the first port of call, after that as long as everything else is in order, and it's been well serviced 12psi should be fine on a standard set up.

lots of people have ran more boost than that I.e 1bar but since we have all invested in afr kits a lot of the time the fueling is a little lean past 12/13psi.;)

[Brigsy]

Get some means of checking the fuelling before upping the boost, wideband afr or a rolling road etc. Every gtt ive setup has required the jetting adjusting at 15psi. With these cars getting old the fuelling could be borderline at standard boost with components wearing.

[Alex]

im running 18psi with a t25/t2 on standard carb with afr's of about 12.3..

Without wanting to sound argumentative, if your boost reading/ARF figures are correct..........No chance! ;)

Re turning the boost pressure up. You can turn it up to circa 13-15 psi without touching the carb but I wouldn't recommend it for reliability reasons. An AFR gauge is one of the best things you can buy if you're tuning a car :)

[olidaviesuk]

As above - even a £25 power run on the rollers where you get a printout of your afrs/lamba will do the trick.. Because they're carb (and getting old with some parts more worn than others) theres no hard and fast rule to how the car will run on given jets and boost pressure. Some of the more experienced members will be able to guesstimate fairly close but that's all it'll be.

Unfortunately it was irresponsible tuners who turned the boost up without adequate fuelling in the late 1980s and 1990s who gave the 5 it's bad name for reliability :sad2:

[Jonny5]

I was lean, 13.6 @ WOT with only 11psi on my standard carb. So please heed all the warnings before tweaking the actuator arm.

[jamie_clioGTT]

Without wanting to sound argumentative, if your boost reading/ARF figures are correct..........No chance! ;)

Re turning the boost pressure up. You can turn it up to circa 13-15 psi without touching the carb but I wouldn't recommend it for reliability reasons. An AFR gauge is one of the best things you can buy if you're tuning a car :)


yep, in theory my engine should be nailed, but ive been rolling round a while now giving it death and thats the readings ive got. and engine is fine.

[Alex]

Is that pressure at the manifold or carb top? I suspect if you started measureing the jets you'll find there's no way they'll be standard, even if your pressure is taken at the carb top.

Still, good ARF though! :D:agree:

[jamie_clioGTT]

its taken from manifold. im not going to lie and im going to make u believe me even less now but.. at 16psi on t2 my afr's were like 12.6 ish. so bigger turbo and better afr's?

it dosent make sense but i just ignore the fact :wasntme: