sorry boost levels again

[Ross99]

guys if my car reads .8 bar at manifold what is it at carb top?

also found out why my car was going nuts, the boost controller did indeed work but a fraction of a turn, was all it needed it was going nuts as it was running 1.5 bar at manifold thank christ i changed my boost gauge as the other one had a leak from where the pipe joined it so always read .8 on boost.

bit of fine turning of the controller its adjusting nicely, just need to re jet the carb and i'm happy.

[Adey aka Ewok]

different on every car, put a guage in the carb top to see bud

[Tiny Tim]

Who cares? Its what the engine is seeing you want to worry about.

[Ross99]

so the .8 bar at manifold is what you mean tim? thats what the engines seeing?

if this is the case its only like 11 psi at manifold, what can i whack it up to and not go overboard, with standard jets and with them replaced with 130 and .9 corrector?

[Tiny Tim]

What I mean is, the further you get from the engine, the less accurate a reading you're going to get.

There will be a boost loss across the circuit.... therefore measuring the pressure at the carb elbow for example will be different to measuring it at the inlet manifold. Between the carb elbow and the manifold, you'll generally see around a 2/3psi drop.

[Sy5GTT]

What I mean is, the further you get from the engine, the less accurate a reading you're going to get.

There will be a boost loss across the circuit.... therefore measuring the pressure at the carb elbow for example will be different to measuring it at the inlet manifold. Between the carb elbow and the manifold, you'll generally see around a 2/3psi drop.


Ok. So if say a safe boost limit for a turbo is 16psi(T2) where do you read 16psi from? If the reading is carb base like mine is, 16psi will actually be 18-19psi at the turbo? Is this right or do you just take the safe boost level from the carb base and hope the turbo doesn't notice....

[Shane P]

so the .8 bar at manifold is what you mean tim? thats what the engines seeing?

if this is the case its only like 11 psi at manifold, what can i whack it up to and not go overboard, with standard jets and with them replaced with 130 and .9 corrector?


15psi/1 bar at the manifold is what you can put it up to on standard jets without going overboard :smokin:

[Ross99]

really it'll run a bar at manifold as it is? standard? once i'm re jetted what can i put it up to

[Mart]

1bar carb top is more like it.

[Brigsy]

1bar carb top is more like it.

:agree: I wouldn't push it over 12 psi manifold on std jetting without checking the afr's.

[Ross99]

right you are i'll stick with .8 bar which is about 11-12 psi? then up it maybe when jets are in, but up it to what?

[dave j gtt]

boosting off my standard dash boost gauge, and on my gauge mesuring carb base its hitting .9 or 1 bar = :cool: if set up right .

i run standard t2 turbo , standard cam. and its rapid is well surprising. no real top tuner bull crap mods, just simple stuff that the world of rtoc gave me last christmas:smokin: thank you all :cool2::burnrubber:

when i got my car it had a big problem :crap: not enough boost had to rev the nuts out of it , and still didnt go that well. think mine use to boost around 11psi carb top :sad2:.

spent some time, new plugs, already had volvo clutch, checked had good fuel pressure , made sure all water system was going to last so added a new radaitor , rebuilt carb, drilled 2nd stage jet to 1.4 cranked the boost up to 15psi carb base and got it checked with the wideband by a top bloke "you know who you are" *lol*

copy and paste from other topic ;)

make sure you have no air leaks ,good vacume, good spark, good colour plugs after a drive, good fuel supply/pressure. good working cooling system.

good working standard brakes dont go a miss ;)

then if you have the carb fully standard and working correct, you can run 1 bar / 14.7 psi carb top. untill you check the fueling and then mabey turn up a bit more.
but thats the limit.

thing being is if you do a few little things to the carb , you could run 1 bar at the manifold apposse to the carb top,

thats if you really need that much power it will need fixing a little more often. if you can deal with that great :)

[dave j gtt]

just rememeber carb top and manifold boost pressure different :smokin: