02-17-2017, 11:08 AM #1
Lets talk about carbed fuel pressure regulator set ups
I'm rigging a boat for a carbed motor right now, I have a big Weldon pump and aeromotive high pressure FI regulator on the boat now.
I got a Holley blue pump for the carb set-up I will be running for a bit, and I'm looking at regulators now.
I have been away from carbed HP stuff for a while, haven't run a carbed race car in decades and my other carbed boats are more or less stock with stock fuel systems so I'm trying to re remember and learn what's new at the same time.
I planned on getting a bypass style regulator, feed from the pump to the regulator, return to tank and output to carb.
I have seen some set ups recently in pics doing searches that looks to me like its set up more like a injection style in the sense that the fuel goes to the carbs from the pump and a tee going back to the reg, and the return from there. IE like how an FI set up goes to the injectors from the pump and the return or pressure side is where the excess flow is dumped to regulate pressure.
I assume this is to guarantee full fuel flow can go to the carbs and flow not limited by restriction through the regulator.
Did I see this wrong, or is that how some people run them on carbed outboard race applications, motor is not a crazy race motor just a tuned 200 2.4 that will see high rpm use(as high as I can get it to turn!!)
I was thinking this type set up might have a tendency to lift the needle and seat? or is this the preferred routing now?
what bypass reg is everyone using these days? seems like there aren't too many choices for middle of the road cost on bypass regs, its either a cheap non bypass reg or a 150.00+ bypass reg??
seems like I used to buy bypass regs for around 50.00 for carbed applications way back in the day??
02-17-2017, 03:20 PM #2
FWIW, the Merc supplied pump on the 2.4 hi-po carb bridgeport was a holley red - fixed at around 7psi - no return to the tank
Dave Strong liked this post
02-17-2017, 04:41 PM #3
Personally I think you'll be just fine with the H-Red as long as you run it through a relay!
As you probably already know, the pressure can be tweeked by changing the built in regulator's spring rate!
I've known many 4ooish hp drag cars running them with no probs!!
20XDC Bullet/Modified Merc 260
295TF Charger/ProMax 225x-Sold!
'83-20' Contender Pickle Fork/Merc 2.4 ModVP BridgePort EFI-Sold!
'85-18' Stratus Tunnel Vee/Merc Hi-Po 2.4 EFI-Sold!
Freedom 240 DLX Fisher Toon/Merc 115
10' Cougar Cub/Merc 25HP On The Bottle!
18" Home Made Tunnel/OS .021XM Outboard on 50% Nitro and Expansion Chamber
02-17-2017, 05:50 PM #4
I have a Holley blue, I'm going to run a regulator. I would prefer to not have considerations that don't follow what I have stated either the conventional carb style regulated way, ie pump to reg, return to tank and output to carb or
pump to carb with tee, tee to rev and return to tank.
Pros and cons of pump straight to carb with reg after carb
02-17-2017, 07:47 PM #5
I just run the Holley non return regulator all mounted in boat just for simplicity and clean looking with no problems. A return style t-eed in with carbs I would think is optimal way being it would be more steady and consistent fuel control without allowing any pressure drops. May be overkill and more envolved. That's how we solve fuel pressure issues on the 6.0 diesel by removing regulator before injectors and installing one after injectors to prevent low pressure points in fuel rail in head. Think same could apply here.
02-18-2017, 10:25 AM #6
I tried a return set up on a carb 245 and it would run out of fuel at about 8000. Tried a couple of things but ended up going back to a deadhead style. Never did figure out what the problem was but I know of one other person that had the same issue. Aeromotive regulator but can't remember the pump, probably Bosch. Used Holley red for the deadhead setup.Quartermaster
texasvector liked this post
02-18-2017, 10:42 AM #7
I ran a blue holly dead head on those carbs with no problems. Most of the carb guys run the bypass regulators. I had mine mounted to the intake with the pressure gauge and return back to the tank to try to keep things consistent. "They" say too much flow into the carb on hard acceleration causes a bog. I honestly never saw the difference, but that was pre high tech loggers ! Good luck. MikeCheaters never Win !!!
02-18-2017, 01:03 PM #8
02-18-2017, 04:39 PM #9
Baffling, I know others have had success but I didn't want to burn it down with more testing.Quartermaster
02-20-2017, 12:42 PM #10
In an old muscle car. Bypass wasn't invented. Thats why vapor lock happened. Fuel was pressed up to the carb and the extreme heat started boiling the fuel in the fuel line and it evaporated. Bam, vapor lock. Thats the simple version. Now a days, Bypass eliminates that problem mostly.
So is this the main reason you would want to run a bypass system on an outboard? I just don't hear anyone saying their boat keeps dying because of vapor lock. Or are "we" trying to integrate bypass systems to maintain a more accurate fuel pressure at all speeds of fuel consumption?If I don't ask any questions, I'll never learn anything.
02-20-2017, 01:21 PM #11
02-20-2017, 04:31 PM #12
Have had car carb set ups non bypass that would drop fp when it was nailed and stumble.
I just have always felt more comfortable with bypass style since they came around.
I could put a dead head Reg on it to get it going and test see how it does I guess I have a mountain of stuff to do to finish the rigging anyway.
WillySteve liked this post
02-20-2017, 04:38 PM #13
02-20-2017, 04:42 PM #14
02-20-2017, 05:50 PM #15
StratosVT liked this post
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