TheSamba.com :: View topic - 2276cc sputters on accelleration, Weber tuning advice needed

Mon May 29, 2017 8:42 am

So I've only owned this buggy for a month and I'm going off what I know. See specs below. Compression check excellent, we've adjusted the valves, synced the carbs and she idles and revs nicely. Under load on acceleration she sputters and pops a bit: does not run smooth from 2.5k-3.5k rpms. Loves to run up high in the rpms and rolls along fine at 2k rpms.

Engine: 2276cc, Engle cam, HiRev Dual Spring Lifters, EMPI Big Valve Heads, EMPI Fuel Pump with Regulator, D8EA spark plugs, MSD 6AL Ignition, MSD Blaster Coil

Carburetors: Dual Weber 44 IDF
idle jet: 60
main jet: 135
Air Corrector: 175
Emulsion tubes: F-11

My thought is that the main jet is too small as is the air corrector. Thoughts?

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Mon May 29, 2017 9:25 am

One thing I would try is to increase your fuel pressure from 2 to 3 psi. With your setup, it would be better to run the 3 psi to make sure you're getting enough fuel. I'm sure other will chime in on this and your jet sizes.

Mon May 29, 2017 10:10 am

cn63bug wrote: One thing I would try is to increase your fuel pressure from 2 to 3 psi. With your setup, it would be better to run the 3 psi to make sure you're getting enough fuel. I'm sure other will chime in on this and your jet sizes.
I'll try that. I haven't messed with the regulator yet, but that's why I put in that image. I've heard guys running up to 3.5. Haven't owned a VW in 20 years or so.

Mon May 29, 2017 10:31 am

that pump sucks. That regulator isn't (it's a restrictor). Replace both. I also recommend bumping the plugs to a heat range 6, 8 is quite cold.

60 idles are too rich, change to 55. Change mains to 145, and airs to 200.

That will get you close(r).

Mon May 29, 2017 12:47 pm

[email protected] wrote: that pump sucks. That regulator isn't (it's a restrictor). Replace both. I also recommend bumping the plugs to a heat range 6, 8 is quite cold.

60 idles are too rich, change to 55. Change mains to 145, and airs to 200.

That will get you close(r).

Got it on the jet changes, that is about what I've heard. I was a bit surprised to see the jets currently are basically the stock Weber 44 setup. I'll order them up.

Brutal on the fuel pump, any suggestions for alternatives?

Mon May 29, 2017 12:52 pm

John makes no apologies for his posts. He just tell's it like it is. Don't be offended.
A Carter rotary FP is highly recommended. Get a Holley regulator downstream of the pump and you'll have a good setup.

Good Luck.

Mon May 29, 2017 1:05 pm

67rustavenger wrote: John makes no apologies for his posts. He just tell's it like it is. Don't be offended.
A Carter rotary FP is highly recommended. Get a Holley regulator downstream of the pump and you'll have a good setup.

Good Luck.
Never offended, all the input is appreciated. I know this engine is strong and just missing a few setup tweaks that will make all the difference.

I've been riding Dirtbikes in Baja for the last 15 years and miss aircooled VW life. The buggy is just getting me back in the game.

Mon May 29, 2017 1:33 pm

Carter makes a rotary pump that puts out 3-4 psi, internally regulated. No regulator needed.

I agree on jets. Most cases main 140-145, 55 idle. 175 air may be ok, but if you go up on the airs will need to use larger main also.
200 air, will probably need 150 main.

Mon May 29, 2017 1:35 pm

Get rid of that fuel pump and throw the regulator away like John suggested.

If you want to stay electric do an internet search for Carter GP60504. It pushes fuel so must be located near your gas tank and is set at 3 1/2lbs of pressure so you don't need a regulator. Rockauto has good prices. CB Performance sells it too.

Then check your float levels and follow the jetting advice John gives you. You can get jets from him that are orig jets that measure and flow the correct amount.

Mon May 29, 2017 6:28 pm

74 Thing wrote: Get rid of that fuel pump and throw the regulator away like John suggested.

If you want to stay electric do an internet search for Carter GP60504. It pushes fuel so must be located near your gas tank and is set at 3 1/2lbs of pressure so you don't need a regulator. Rockauto has good prices. CB Performance sells it too.

Then check your float levels and follow the jetting advice John gives you. You can get jets from him that are orig jets that measure and flow the correct amount.
Ordered: Jets: IJ:55, MJ:145, Air:200 rotary fuel pump. I'll keep ya posted. Thanks for the input

Mon May 29, 2017 7:46 pm

That's the pump I'm running with 44s. Works well with no regulator.

Mon May 29, 2017 7:55 pm

As some one with experiance with buggys and street cars here is my advise, loose the regulator, if that facet pump is the low pressure pump keep it. 1 grain of sand will stop a carter pump, when the same particle stops the facet a large screwdriver handle against it a couple times will get it going again, not the rotary. This is probably the only application where I would suggest this pump over the carter. And this is because I have been stuck in the dunes and desert with both of these pumps. Also you will not see a rotory pump used as a secondary in any limited desert cars, all Facets.
As far as your jetting I agree with most here.

Tue May 30, 2017 8:43 am

mcmscott wrote: As some one with experiance with buggys and street cars here is my advise, loose the regulator, if that facet pump is the low pressure pump keep it. 1 grain of sand will stop a carter pump, when the same particle stops the facet a large screwdriver handle against it a couple times will get it going again, not the rotary. This is probably the only application where I would suggest this pump over the carter. And this is because I have been stuck in the dunes and desert with both of these pumps. Also you will not see a rotory pump used as a secondary in any limited desert cars, all Facets.
As far as your jetting I agree with most here.

Good point mcmscott. I bought a pressure meter so my plan is to get flow set at 3.5psi. Put in the new jet sizes and go from there.

Tue May 30, 2017 9:01 am

It's hard to give accurate advice with knowing the lift/duration of the cam and what size valves those heads have in them? Are they ported?

Tue May 30, 2017 10:32 am

[email protected] wrote: It's hard to give accurate advice with knowing the lift/duration of the cam and what size valves those heads have in them? Are they ported?
Understood.

Bottom line it is not running right with the setup I noted. Since I don't have access to the builder, my specs are limited. I feel I'm 70% there, just need to tune it to run the full powerband.

The advice given will put me on a path and hopefully this bugger will lose the mid range sputter. I'll keep you posted.

Wed Jun 07, 2017 6:04 pm

Thank you guys for all of the advice. I did a bunch of tweaks and the motor is now a smooth beast. Here is what I did:

MJ: 145
IJ: 60
Air: 200
Spark plugs: NGK D6EA
Valves adjusted
Carbs sync'd

No more mid range sputtering and feels more powerful.

Thu Jun 08, 2017 5:09 pm

Idle seems on the high side, try 52-55's we will see what others have to say.

Thu Jun 08, 2017 5:11 pm

yeah, usually 60 is too big, but not always, that's why I put "usually" in there. :wink: