32/36 weber turbo tuning

hello, i purchased a turbo kit from turbogemini for my 2.3 isuzu motor. it’s a well thought out kit but i’m having issues tuning the weber carburetor under boost. the motor leans out under boost with a 260 already in the primary jets. the Weber is turbo prepped and sealed. i’m lost and the carburetors been off an on over a dozen times. any help would be appreciated. 

1) I would move this away from TechTips since this isn't really a Tech Tip per se

2) Toss the carb and install MegaSquirt?  Seriously this is probably a better solution in the long run, provided that an EFI intake/throttle body is available for that motor.  an MS1 is $125 and will manage a boosted 4-cylinder without issue.  An MS2 provides more tuning options and further expansion opportunities.

3) Seriously though, I'm guessing you bought one of these kits (how terrible is that website)?

http://www.turbogemini.com/Turbo%20Kits.htm

You may need to reduce the amount of boost or find a way to get more fuel into the engine via altering base fuel pressures and/or increasing jet diameter (you can drill them with lettered drills, though its not ideal)

In reply to Stefan :

thanks. unfortunately that’s not an immediate reality. i’m the original owner and wanted something reliable and different. i’ve searched some forums and found that blocking the secondaries air feed will prevent a lean issue under boost. i’m still researching and any advice is appreciated. thank you drive safe 

Is the fuel bowl boost pressure referenced? 

Carbs work by drawing air over an orfice that sucks gas out as it goes. But this only works when the gas in the bowl and the air are close to the same pressure (atmospheric on a regular carb). If the air pressure goes up, something has to similarly increase the pressure of the fuel bowl.

Robbie's got an excellent question.

Is this the kit you went with for the carburetion? If so, it seems like Gemini should A) have gotten you in the ballpark with something that didn't go lean under boost, and B) be able to provide you some well-informed support for the kit you got from them.

There appear to be a few optional extras which may or may not be all that optional in your application. E.g. did you get, and do you need, the boost-referenced fuel pressure regulator?

Have you talked to Gemini about your issues yet?

As an aside, for the cost, I think a Megasquirt installation would be easier, more reliable, and cheaper than that carb kit. But now you've acquired it, I can also see wanting to see it through, though unless you are truly a love of carbs, that may be a good-money-after-bad situation. Hopefully getting the carb sorted doesn't require much more expenditure.

thanks ransom and yes the settings are close but the seller’s in Australia and i’m impatient.  ben of turbo gemini just now replied to an email i sent earlier today. i’ve forwarded it my mechanic to makes sense of it. its been difficult finding info on tuning a weber carburetor on a blow through turbo kit. thanks again to all who’ve responded. drive safe 

message to admin this was my first post in grassrootsmotorsports if this post needs to be located somewhere else please move. thank you 

In reply to turboisuzu :

I moved it over from tech tips to the main forum so it would get more views.

Is the fuel pump capable of producing the pressure you need, and is there a boost referenced pressure regulator?  Remember, if the carb is designed to run on 3 psi and you are pushing fuel into an air box with the carb inside, to create 3 psi with 6 psi of boost, you need 9 psi fuel pressure.

In reply to Streetwiseguy :

howdy. the supplied electric fuel and 1 to 1 fuel pressure regulator are set at the designed fuel pressure of 5.5 lbs.

In reply to turboisuzu :

Where is the fuel pressure regulator (henceforth FPR) taking its pressure reference? Same question for the carb?

I feel like it's strongly likely that we're trying to chase down something fundamental. The sealed, boost-referenced carb and boost-referenced FPR are things you need specifically to avoid the problem you're having. It's likely that further tuning would be needed to get it really right, but if it's going very lean as soon as you're under boost, that makes it sound like one of these things isn't doing the fundamental job of keeping the fuel system adjusted to manifold pressure.

Without that compensation, no amount of jet sizing will make any difference.

I suspect that getting Ben and your mechanic talking more directly would be a good idea; perhaps you should make that email conversation between all three of you.

Moreover, as long as we're playing along here, why not share the questions and responses here? We're guessing from almost nothing, and don't know what you've tried, what the installation looks like, etc...  You initially stated it as a tuning problem, but I think it makes more sense to approach it by making sure the initial installation is correct before getting to tuning.

You stated right up front that you're impatient, but this is one of those things that just fundamentally requires a methodical approach. 

I would monitor fuel pressure while driving and verify that it is rising at a 1:1 ratio and not flatlining at some point. 

In reply to turboisuzu :

Just checking to see if you ever got your weber 32/36 tuned for the blow through?

Not on this application, but I have also seen a carb. fuel bowl get sucked dry... not a large enough bowl volume to support the engine' demands. ( we chased every other fuel delivery possible thing; found that by default. )

But chase the recommended options given here first; just keep it in mind.