VW Bug 2054cc Supercharged – Tuning Help Needed

[madmax23]

VW Bug 2054cc Supercharged – Tuning Help Needed

Hi everyone,

I’ve been building my VW Bug for the past 5 years, and I’m finally at the last stage — but I’m stuck with the tuning. My setup is similar to a Dick Landy–style supercharged build, so I’m hoping someone with experience can share their settings.

Engine Specs:
• 2054 cc, 7.6:1 compression ratio
• Large-valve heads, concave combustion chambers
• Engle 120 camshaft
• 1.25 ratio rocker arms
• Mahle pistons
• High-pressure oil pump + external oil cooler
• 123 electronic ignition
• NGK BPR7 spark plugs
• Holley fuel pump + Holley fuel pressure regulator
• Holley 1450–390 CFM double-pumper carburetor
• Lightened flywheel, sintered clutch
• Gearbox: long 4th gear, medium-ratio differential
• 4-into-1 exhaust, quick-open valve, SC muffler
• Marshall Nordec 200 supercharger (modified)
• Custom intake manifold, draw-through system

Current Settings:
• Ignition timing: 12° BTDC
• Front carb main jet: 25( ordered 57)
• Rear carb main jet: 28 ( ordering 60 (block-off valve installed)
• Fuel valve: 10.5 ( is it worth measuring the vacuum in idle to get the best valve size?)
• No air filter (just a mesh)
• Vacuum source for the fuel valve is now from under the supercharger (I drilled the carb and intake to make this change)
• Vacuum reading: 0.5 inHg at idle, 0 at medium throttle

The Problem:
The engine is running very rich — it’s basically flooding with fuel. I haven’t yet installed the new valve that’s on its way from the USA, so I’m not sure if that will resolve it.

What I Need Help With:
• Recommended ignition advance for this setup
• Holley carburetor tuning: main jet sizes (front/rear), fuel valve size, accelerator pump nozzle size
• Any tips for draw-through supercharger carb tuning to prevent over-fueling(main concern at the moment)

Could a boost referenced power valve or a blow out protection kit could solve my problem?


Any help or proven settings from similar builds would be greatly appreciated!

[Alexander_Monday]

I can't help much, but here are my thoughts based on tuning by twin screw intercooled supercharged 2110 that was port fuel injected.
Under boost it liked non projected tip spark plugs better.
I assume with a roots blower and no intercooler you will not be going above 8 to 10# of boost, but in case:
Past about 12# I had to back the gap off to 0.018".
Past about 16# I had to go to the best coils I could get, the IGN1's but I am distributorless.
At 18# I had to be sure and index the plugs.

You did not mention valve springs.
Boost will push on the back of the intake valves, so they need a little more seat pressure than NA.
How much depends on the area of the valves times the boost pressure.

When I was young I raced V8's and I assume what you call the fuel valve I call the power valve.
If so, then yes it is important to measure idle vacuum to the power valve and select a power valve that opens at about 1/2 of the idle vacuum.
I have not heard of a boost referenced power valve blowing out.
I assume you plugged the vacuum feed hole for the power valve in the baseplate?
If not, that will definitely cause a problem.
_________________
Danth’s or Parker’s Law:
“If you have to insist that you've won an internet argument, you've probably lost badly.”

Alexander_Monday->What were the rings gapped at?
bedlamite->Almost enough.

[Alexander_Monday]

Oh, and timing is going to be different than mine with an FK10/87 cam, 1400 idle, and will depend on compression and chambers but here is what worked well on mine.
Don't go by it because it will not be right for you, but the trend is an example.

_________________
Danth’s or Parker’s Law:
“If you have to insist that you've won an internet argument, you've probably lost badly.”

Alexander_Monday->What were the rings gapped at?
bedlamite->Almost enough.

[BFB]

Im not a domestic carb guy but dont you need more vacuum than that to keep the power valve closed? I’d think with that little vacuum the power valve would be open at idle and dumping fuel.

I do know that the only time you need to boost reference from another location on a drawthrough set up is IF you’re pulling vacuum at WOT under the carb. Otherwise if at WOT vacuum is 0 then your good to go running the carb like its on a N/A intake, which id bet your fine considering its a 4BBl. ( And i think you meant 4150 ). I’d say to disconnect that vacuum reference line going to under the supercharger and connect it to the carbs non ported vac fitting and see what happens.

Also, might talk to these guys.
https://www.lowbugget.com/turbo_new_page_link.html
_________________
"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[Alexander_Monday]

With a draw through roots supercharger the vacuum under the carb is usually stronger than manifold vacuum so it is very common and usually necessary to either plug the power valves in a drag car or manifold reference them for street. The exception is fast opening wide of the throttle which will open it, but when intake velocity builds up it can close and go lean under boost.

His stated vac 0.5 in is way too low so most likely a leak which could be failure to plug the passage in the base plate when drilling a new hole for reference vacuum.
Even if he meant 5 inches a 10.5 power valve will be wide open and would need a 2.5, but even the SBC white stripe cam I ran back in the day had more vacuum at idle and it was a 5500 to 7500 cam.
No way to attempt to adjust jets or air with the power valve open.
_________________
Danth’s or Parker’s Law:
“If you have to insist that you've won an internet argument, you've probably lost badly.”

Alexander_Monday->What were the rings gapped at?
bedlamite->Almost enough.

[daveblank]

[madmax23]

Just a few pictures of the set up.

Thanks for all the replies so far.

[rayjay]

Check to make sure your throttle return springs don't over center at WOT. Personally, I would make a new bracket so the return springs are parallel with the throttle cable. Your current setup has the returning force decreasing the farther the throttle is opened.
.
The first tuning aspect I would address is the completely inadequate air filter. The element is way too small and having the top plate that close to the carb inlet could be introducing all sorts of issues.
.
I think you would be money ahead to pay for some rolling road time with a tuner familiar with Holleys and superchargers.

[Alexander_Monday]

Nice to see supercharger set ups on a VW.
One thing I forgot to mention based on my experience.
#4 main bearing will wear faster.
I got about 12K NA then about the same supercharged and when I tore it down to freshen up #4 was past tolerance.
YMMV
_________________
Danth’s or Parker’s Law:
“If you have to insist that you've won an internet argument, you've probably lost badly.”

Alexander_Monday->What were the rings gapped at?
bedlamite->Almost enough.

[rayjay]

https://www.bing.com/videos/riverview/relatedvideo...;FORM=VIRE