WHAT'S INSIDE? -BLOW THROUGH CARBS

CSU & QUICK FUEL-WE LOOK INSIDE BOTH! Kevin from CSU steps up to help our twin-TorqStorm 6.0L with customer carb. Trying to run two superchrgers with an E85 blow-through carb. Check out what happens when we throw the kitchen sink at it! We look inside the Quick Fuel and CSU carbs to see what makes them tick.

[superkillr]

To anyone who can't find the answer.... it was the dyno fuel pump.

[manitoublack]

I'd suggest trying a carburetor hat that has a better radius into the boosters. Even one with guide vanes or a large plenum (like the old Banks power hat's from the 80's.) Remove the turbulence to improve booster signal and response ;). Remember that the cleaner and stronger you can make the signal at the boosters (by improving the Delta.P between the main venturi and booster, ) the more fuel you'll drag through the booster. If the air is all chopped up, no clean signal = no fuel draw. You could even go as far as having a 30cm straight pipe extending out the top of the carb into the hat to have air moving completely vertically into the boosters.

In addition. As airflow/airspeed increases at tight 90° bends, the turbulence increases making the problem worse. Just think water through a hose.

Good idea for a test. testing various carb hats ;).

[smblock]

Had the exact same problem. LQ9 with D1SC ProCharger making 15psi. Through a Quick Fuel 750cfm Blow-through carb, Aeromotive Boost Ref Regulator, Aeromotive fuel pump, 8AN fuel line, on a Victor Jr. No Cooler and 90* Carb hat. During first test run the AFR slowly Leaned to an unsafe level. Immediately started with carb tuning, and increasing fuel pressure thinking, more pressure more fuel. Increasing fuel pressure doesn't increase volume.
The fix- Change 8AN fuel supply line to 10AN. Separate fuel supply lines from the Regulator to Front and Rear bowls on the Carburetor.
I didn't see how yours was set up in the video, but sounded like the same problem I was having. Thought I'd share.

[Rdawg]

Extend the vent tubes into the 90 so they pick up boost pressure earlier at the bonnet. This increases the pressure in the bowl sooner and in turn assist in allows easier flow out into the engine. It creates a pressure difference. Aircrafts use airspeed tubes for this purpose

[henrysmith]

I run Vent tube extensions on mine. The extensions down into the carb hat more than half way. I was able to jet back down on the carb for street use. The extensions allow it to pull more fuel through less jet. I also run AN 10 line to 8AN with fuel return to tank.

[snaprolle]

Seen this once before. The elbow on top of the carb is screwing up the airflow. Get one with more of a radius to turn the air into the carb. Good luck. If you guys can't figure this out, the rest of us are screwed.

[minibuggies]

I agree, it's the hat. Anytime I run more then 8 lbs of boost or so the carb hat or enclosure box has to be the proper design. I recommend the Paxton power hat. Works well at that boost range. I've also had some success using a screen in the airflow like a boat filter. Torque Storms hat is supposed to work up to 12 lbs. I would think you should have one of them to try. Thanks for the vids!

[HeadFlowInc]

Unmetered air could be introduced to the engine? I know it sounds simple but I would be searching for vacuum leaks or some other source for the unmetered air. The fact that you’re seeing two different air fuel ratio’s on different banks of the engine should give you an idea where to look.

[kathleenhastie]

I agree with you on most your changes, but we use e85 on top of a 177 Weiand using boost referenced bypass reg 3psi to 13psi and a 130 gph mechanical pump. (10psi boost)We are worried about lemonade (bubbles) in fuel bowl at high rpm. This is why I suggested duel needle bowl lower fuel pressure and help fuel level in bowl. Love your content thanks GM engines.

[addmoreboostOG]

Carb hat turbulence not letting the boosters do their job when the air really gets moving. Perhaps trying an extreme velocity type hat or one with a divider to split the air evenly.

[goodmanboattransport]

Listened to this video now 3 times, fuel pressure is fine, checked before and after the regulator, and this problem is going on with 2 different E85 carbs and a gas carb, the common component is the carb hat, and running 2 superchargers is increasing the CFM dramatically, air is hitting the back of the hat, and not able to flow through the rear throttles, backing up and causing an eddie effect (turbulence) and messing with the front throttles ability to get a smooth flow of air, and likely surging causing the rich lean bouncing we see on the HP curve instead of the smoother curve we usually see. If you can cut the hat and weld a second fitting for each charger, the boosted charge air should stop being so turbulent, I suppose this could also be remedied with a splitter installed that others have suggested as well. Good luck with the diagnosis, great work as usual

[koalafiedengineering]

I have not read the comments to see if this has been figured out yet but your issue is likely velocity through the venturi. This is only encountered on a blow through blower application. Put a anemometer in the plenum to measure airspeed and you will see it slow down and begin to stall as boost increases. This cannot be checked with a hot wire maf because of the evaporative cooling from the fuel, a vane air meter may work. As air velocity drops fuel distribution becomes an issue and vacuum signal through the carb drops. You have a combination that is completely filling the cylinder with pressurized air before the intake valve closes. You can mitigate this problem by reducing lsa to increase overlap, Closing the intake valve before air speed stalls or a combination of both. Or just use port

[ssoffshore]

Some good thoughts already posted. One other thing to keep in mind is that it takes a lot of power to drive those two blowers. So while it might only be making 1000hp on your dyno, there's probably 200-300 hundred (or more?) being spent to drive those two blowers... which all takes fuel to do.

The lean bank thing is odd. Sounds like an air flow/distribution issue to me.

[tylermurray]

Check intake for vacuum leak or any other vacuum leak we ran into the same exact issue on our blow through 406

[standbackperformance]

I tune an X Nascar Chrysler W8 with a Procharger and one of Kevin's carbs for drag racing.

It started out as gas motor carb combo with an inner cooler which worked Great.

Last year we has Kevin convert the carb for E-85 and it took me months of trial and error to get ahold of it. Same issue as you way too lean up top.
The things I did that helped most were, had Kevin send heavier power valve springs along with me drilling and tapping both front and back metering blocks to accept 4 metering jets each. That allowed better fuel control as the boost came up which made the biggest change. On the street it made driveability way better.
I like you have1 bank running leaner and my explanation for that has to do with the hat and squirters. Watch any video of a dyno run with a cam above the carb and at some point you see the squirters adding fuel to each venturi. If the hat pushed air in vertically all would be good but like others said your asking it to make a 90 deg turn and things get unhappy.
My plan this year when we get out of our houses is to put a Snow Performance meth/water system on with a shear plate under the carb. That will add fuel, cool the incoming charge and with a 2 jet plate allow me to add more fuel to the side that need it.

If that doesn't work it will get a Haltech 2500 EFI system.

[wyattwunderlin]

What is the BSFC? Once the amount of fuel the engine is consuming has been established, a fuel issue can be verified. An engine with excessive amount of fuel (90 Lb/Hr of flow though 8 injectors making just over 500 Horsepower excessive) can "Trick" the O2 sensors into reading a lean condition.


Once a fueling issue has been identified, start with the incoming air and the signaling for fuel. Several have mentioned that the carburetor hat could disturb airflow in unintended manors. Once verified that the corroborator is receiving the correct signals to deliver the correct amount of fuel, analyze the fuel entry point into the corroborator. Work back through the complete fuel system and sub-system until a point of antiquate fuel has been reached.


I hope this helps you out, or may provide guidance for another in the future.


Thank you and best of luck.

[dhatchett]

Richard, you could extend the float bowl vents into the snorkel of the hat using 5/16" tubing into steadier boost pressure in the boost tube . This will increase the pressure in the bowls at high air FLOWS . MY to cents

[josmith]

20 years ago when I played with boosted cars on OBDI and you couldnt tune them we would run cold start injectors off pressure switches. Boost would hit whatever PSI and the injector would turn on. Dont know if that would work

[dennykatz]

If there are no vacuum leaks in the system, are the fuel bowls holding enough fuel when making the high rpm pull? Bowl extensions, high flow needle and seats, larger fuel lines from the regulator(s)? Try a belt or cam driven fuel pump with bypass back to the tank. Mechanical fuel pumps are flow tested at 100psi which is approximately 8000 rpm!

[blakeperritt]

Great video Richard! These are getting more and more interesting