Bender lean spot. Relocate float bowl pressure line?

[spray25]

Myself and several other Bender owners are experiencing extreme lean conditions at aproximately 1/3 throttle (which also equals about 8,000 rpm and 3.5 lbs of boost). We have tried to many jetting combinations to even try and count them all. Fuel pressures are verified correct. No leaks in any lines.

I am becoming convinced that the problem lies with the pitot system Bender uses for pressurizing the float bowls. No other kit uses a system like this and no other kit is producing this lean spot.

I want to try moving the float bowl line to the airbox where most other kits have it. I understand that the exact place on the airbox that the line is connected has an effect on the amount of pressure that is put into the float bowls. How critical is it though? If the wrong location is used does it just mean diferrent jetting or does it mean that the system won't work at all? Also does anyone have any guess at to where would be the best spot?

Another option I have is to relocate the line feeding the fuel pressure regulator to the nipples behind the carbs and then use the original regulator spot on the airbox for my float bowls.

Any input?

 

[Ted Jannetty]

Myself and several other Bender owners are experiencing extreme lean conditions at aproximately 1/3 throttle (which also equals about 8,000 rpm and 3.5 lbs of boost). We have tried to many jetting combinations to even try and count them all. Fuel pressures are verified correct. No leaks in any lines.

I am becoming convinced that the problem lies with the pitot system Bender uses for pressurizing the float bowls. No other kit uses a system like this and no other kit is producing this lean spot.

I want to try moving the float bowl line to the airbox where most other kits have it. I understand that the exact place on the airbox that the line is connected has an effect on the amount of pressure that is put into the float bowls. How critical is it though? If the wrong location is used does it just mean diferrent jetting or does it mean that the system won't work at all? Also does anyone have any guess at to where would be the best spot?

Another option I have is to relocate the line feeding the fuel pressure regulator to the nipples behind the carbs and then use the original regulator spot on the airbox for my float bowls.

Any input?

Don't move the Pressure regulator to the carb boots this can shut off fuel flow on Decell.

If you can put the Carb float bowl pressure line in between 2 of the carbs up high on the box facing the intercooler or inlet pipe this would be a good place.

 

[spray25]

I have the stage one box so about the only place to get direct airflow would be to put it near the front left with the opening pointing to the right. Does it need to protrude into the box? If yes how far?

 

[BlgsRX-1mtn]

Ray, for what it's worth (comparing apples to oranges here) my SC kit has three lines that regulate the carb/fuel pressure. Ther are two that attach to the bottom of my air box just after the intercooler; one goes to the fuel press regulator on the pump, the other goes to the rear carb vent tees. The third line (yellow one in the pic) runs from the charge tube to the front carb vent tees. Is this what your thinking of trying?.

I'm running 127.5 mains, 25 pilots, airscrews 2 3/4 turns out with the needle clip in stock setting. My sled is a little lean at idle (low 13:1 A/F ratio) the mid range is in the low to mid 12:1 range and my WFO is reading high 11:1 to low 12:1 on the wideband O2.

Jim

 

[spray25]

Do you happen to know if the hookup on the charge tube is flush on the inside or if it protrudes into the charge tube a ways?

 

[Ted Jannetty]

It can be flush.

 

[spray25]

So maybe a brass hose barb where the red arrow is pointing?

 

[BlgsRX-1mtn]

What sits right underneath the airbox on your sled? The two brass "hose barbs" on my airbox sit centered and are 90 deg elbows that point forward. The hoses make the turn from the brass elbows with the carb vent going to the elbow that is centered in the bottom of the air box. The hose for the fuel pressure regulator is located to the left of center about 1".

BTW, where the hell is Peter? You should be able to duplicate his setup to eliminate the Pitot tube. I don't know if a picture of my airbox would do you any good but here it is. You get a better view of the yellow tube comming from my charge tube to the front carb vents also.

Jim

 

[spray25]

The bottom of my airbox looks about like yours. Two 90's that feed the fuel regulator and slides.

So far I could put a hose barb where the red arrow is pointing, or I could put one in the charge tube. Jim do you know if you charge tube barb is flush on the inside?

I'm actually leaning towards the charge tube. Some say in the airbox you have to have the perfect spot and perfect length. The charge tube sounds more forgiving.

 

[BlgsRX-1mtn]

Ray, I'm not exactly sure if it's flush or not. The bung looks similar to the ones on the bottom of the airbox though.

I do have the tigon tube and brass fitting from MPI though if you want it. I went to Ace hardware and bought the yellow tube and brass fitting for my charge tube. Bear accidently sent me a charge tube for the Apex which was an allen head plug where the hose goes in it.

 

[spray25]

So the charge tube just has a bung welded on it and then you thread a brass hose barb on it? If that is the case then it is flush or at least for all practitcal purposes it is.

So where do I find a steel bung that has 1/8 npt threads on it? I doubt my charge tube is thick enough to just drill and tap.

 

[BlgsRX-1mtn]

Here is what my charge tube looks like. The bung is between the blower dicharge and the 90 deg bend. The hose barb was actually about 1-2 mm shy of flush with the inside.

As for locating a steel bung with 1/8" npt threads; your on yor own there cowboy.

 

[BlgsRX-1mtn]

Ray, I found a bung assuming your charge tube is thin walled stainless.

Jim

www.racepartsolutions.com/products.asp?cat=20

 

[spray25]

Thanks Jim. Big help. I'll see if the local guys have anything (doubtful) and then order one from that website.