Blow through turbo bogging/fueling/carbie choices

[zep]

I'm having a bit of trouble with my blow through carb setup (32/36).

(G161z, forgies, shortened rods, hd crank, turbo cam, T3 turbo, etc)

When I floor the accellerator, the engine bogs down off boost and stutters untill the boost comes on, then it revs up nice and fast. The two guys who are helping me with this (old race car specialists running a carb shop and a race car shop respectively) reckon that the secondary throat is giving too much fuel, so when I put my foot down and the secondary opens, it's trying to push too much fuel in. We took the top off of the air box and you could definately see fuel kinda spraying back out the carb, and there were droplets in the top of the throats.

Both these guys reckon that rejetting the carb wont really help, as it is the size of the venturies that make the difference. They are recommending I get a 32/32 with 22 jets to solve my problem. The idea makes sense to me but I have the feeling that this carb will be too small, the come stock on 1.4s and stuff.

Do you think that rejetting my current carb with smaller jets will make a difference, or that these guys are correct in saying I need a smaller carb?

Would a 34ADM possibley be an option?

Cheers

Leon

[SYKOV6]

remember bro they are the experts. tuning carby /turbo set ups is a bit of a black art i think. can ya rejig the linkages to make the secs open later after its come on boost?

[zep]

The secondaries open depending on how much throttle you put on (mechanical I think it's called). If I gradually put my foot down, it's all good coz I can work it so the boost comes on just before I floor itand open the secondary.

[drftnmaz]

i'm no expert here but the first thing i'd do is get a airr/fuel ratio gauge and o2 sensor so make sure fuel is the problem,

but how hard is it really to change a jet compared to getting a new carb and stuff??

the only downfall i can see to running a smaller jet is u will have to up the fuel pressure to compensate this

mechanicial secondaries are normally operated when the throttle linkages come into contact so thees normally a way to alter it.

[Guest kris]

Accel pump jets too large? Cheaper to try than a new carb perhaps.

This might be a silly suggestion, you'd be better listening to the experts.

[Ned]

sorry leon, but i dont know

my suggestion is ringing around other pro's! best bet

[RT]

ah I believe I remember telling you that this was what was going to happen..

When my mate was doing this the best we could get was to only put the foot down half way to begin with and then floor it once it was on boost.. otherwise the carb just choked. It's always going to be a compromise dude as I have always said.

Also, a holley carb works best with forced induction as that what lots of supercharger people use.. the webber is notoriously problematic in forced induction setups..

[Toucan]

First thought would be to change where the secondaries open. On a 32/36 its at about 3/4 throttle, and yea mechanical is the word for it. Have a look at your carb its the simplest setup ever.

When you press the pedal you open the primary butterfly and when you reach 3/4 a pin locks into the metal bit and then continues to open the secondary butterfly. If you wanted the secondaries to come on later you would just need to extend the hole in the metal part so that the pin takes further to lock into place. I dunno if you understand but look at your carb and it should start to make sense.

Dunno if its what your after, but you would have to floor it more before it would bog down, and maybe the boost would have kicked in by then... Cant hurt to try anyhow.

[Jerm]

yeah it would be easy to make it stay closed longer... but i don't think thats the best way to fix it.. look for that carb you were tlakign about the other da from the lancia turbs

[zep]

Yeah, I think I may have found the carby I'm looking for. Its a 32/32 from a Lancia Delta HF Turbo (early model). Both people who are helping me out rekcon this will fix the problem.

I replaced the progressive jet in the carb with a .60mm one as the one I had was previously drilled out to 1mm. This has helped a bit, more than changing to a .45mm anyway.

Next problem, overheating!

[Toucan]

Is it another Weber? I hear that the ISAN(sp) carbs are real good for a turbo setup.

[lowlancer]

What are you running cooling wise? Twin fans? Bigger rad?

[zep]

Just running the regular radiator with a 12" electric fan and gave the system a flush. I think I'm gonna have to upgrade the radiator so something a bit more modern...

As for the carb, I talked to the dude who gave it to me and he said he modded the secondary to open when the primary is half open. I'm not sure if changing this will make a difference when its foot to the floor.

Although, I did change the progressive jet (had been drilled out to 1mm!) to a 0.60mm one, and that has helped a bit.

[Guest WESTCORT]

Im running a 32/32 weber just thought id add that in. just gave it a fresh rebuild goes well, but i wonder how much better a 32/36 will go

[SYKOV6]

i dunno its hard to say how much the difference would be. its only 4mm, i got the throttle body on my vn commonwhore bored out 5mm that made quite a bit of difference.

[zep]

WESTCORT: IF I cant find the carb I need, keen to swap your 32/32 for a 32/36? I got a good one here

(not the one on my car, a nice reconned one)

[Guest WESTCORT]

i might be keen, ive just freshly reco'd the one i got now.

let me know when you are after a 32/32 for sure and we can talk

[Burntrubber]

I thought long and hard about this problem my engine does the same thing bogs until boost. But then I had an idea I jetted the secondary rich as well as drill the powervalve to give more fuel under boost this is probably why it bogs off boost because its to rich until boost comes on. Just an idea could be completly wrong , as for a 32/32 I got a mint one I used on my gem before the turbo setup if it works better for you I'll give it a go also.