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Fine tuning my IDF 40s on a Type IV engine
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Tronview
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Joined: 29 Jun 2007
Posts: 330
Location: Bethlehem, Ga

1963 Volkswagen Beetle

PostPosted: Mon Jan 09, 2012 1:32 am    Post subject: Fine tuning my IDF 40s on a Type IV engine Reply with quote

I have been working to get a the right combination of jetting for my carbs. The beautiful thing is that I have improved the acceleration and remove the flat spot I had at start off but now I am working to increase my fuel economy. I would appreciate any ideas or instructions on how I should precede. Before I started adjusting the jets I was getting 19-22 MPG now I am getting 11-16 MPG I am unsure of what the cam or head measurements are but I have been told that my engine is a 2000cc based on the block and certain tells with the heads. below is a list of the current carburetor components.

Dual Weber IDF 40s
Main Venturi 28 mm
Main Jet 135 mm
Idle Jet 55 mm
Air Correction Jet 200 mm

The two jets I have been adjusting were the following.
Main Jet: was 115mm now is 135mm
Idle Jet: was 50mm now is 55mm

I would assume that adjusting the main jet back to 115mm will increase my MPG but am concerned about how that will effect my engine.

Thanks for your help.
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Last edited by Tronview on Mon Jan 09, 2012 10:41 pm; edited 1 time in total
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Greg



Joined: 12 Aug 2009
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Location: Jefferson, GA

1969 Volkswagen Beetle

PostPosted: Mon Jan 09, 2012 1:15 pm    Post subject: Reply with quote

Are you using the stock distributor?
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1963 Volkswagen Beetle

PostPosted: Mon Jan 09, 2012 3:15 pm    Post subject: Reply with quote

Greg wrote:
Are you using the stock distributor?


Yes. based on my research it is.
I am using a 0231 181 012 vacuum advanced Distributor.
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Greg



Joined: 12 Aug 2009
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Location: Jefferson, GA

1969 Volkswagen Beetle

PostPosted: Mon Jan 09, 2012 5:23 pm    Post subject: Reply with quote

hmmm, Since you had a flat spot on take off, I'm wondering if the vacuum part the of distributor isn't working. (I'm guessing that it's centrifical/vacuum advance)
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PostPosted: Mon Jan 09, 2012 5:58 pm    Post subject: Reply with quote

Vacuum is working fine. And the flat spot went away when I increased the ideal jet to 55mm
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Greg



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1969 Volkswagen Beetle

PostPosted: Mon Jan 09, 2012 10:47 pm    Post subject: Reply with quote

Do the plugs look sooty when you take them out, if they are tannish (normal), I'm at a loss.
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PostPosted: Tue Jan 10, 2012 2:02 pm    Post subject: Reply with quote

Ill take a look and get back with you.
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cavediver520



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PostPosted: Wed Jan 11, 2012 7:27 am    Post subject: Reply with quote

Do a search for best lean idle...follow the steps and that should fix you up and if not it will let you know where you stand as far as idle jets go and if not, March aint that far away. Good luck.
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Mountain Power House



Joined: 26 Jul 2006
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PostPosted: Wed Jan 11, 2012 8:50 pm    Post subject: Reply with quote

You were getting better MPG because you were way too lean.. Also the weather is colder now and the engine isn't as efficient and the tuning changes with air density increases.. We are also on winter blend fuel now and every car I own has lost 3-4 MPG and it does every year.

That said, you should only be getting about 18MPG @ peak on the highway when tuned correctly. Remember that you are driving a 2 ton, non-aerodynamic brick with huge axle bearings and large CV joints. This equates to horrible aerodynamics and a lot of mechanical drag as well. The engine makes less than 70HP and has to work its ass off all the time just to run 60 MPH. I have found with a Bus that MPG plummets after 60 MPH.

The venturis you are using are properly sized for a 1600cc Fiat engine, they also for well with a 1600 Type 1, but not a 2 liter Type 4. Try this

32mm Vent
135 main
180 air (This will bring the mains in earlier and will richen up just the top end)
60 idle (those 55s might work but if it hunts at idle or wants more than 2 turns out on the mixture screws to idle well go to 60s)

Now, remember that most carburetor issues are really ignition issues.. Question your advance. Try going up and down with the timing and see how it responds. You must allow the engine to TELL YOU what it wants, meaning you have to LISTEN as well as act.

Whats the current timing?? What dizzy? How are you setting it?

Those vents are too small, they are creating elevated vacuum signatures that are effecting the progression circuits.
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Jake Raby
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Tronview
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1963 Volkswagen Beetle

PostPosted: Thu Jan 12, 2012 11:40 am    Post subject: Reply with quote

Thanks Jake for all the info. I will apply the changes and post my current timing and dizzy info soon.
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PostPosted: Sun Jan 29, 2012 11:24 pm    Post subject: Reply with quote

Well that didn't work.

Engine idles nicely at 800 rpm and does not feel to be missing any horsepower when driving on the interstate or going up hills. But rpm changes such as present during shifting or pulling out onto the street give bad hesitation ( hiccups ) which do not go away till engine rpms even out. I did not have any hesitation before the changes were made. I am also thinking that my engine is not a 2.0 but a 1.8 based on the head markings.

Below is the changes I made. and updated engine stats.

Changes:

Air Correction Jet 200 changed to 180
Main Jet 135
Idle Jet 55 changed to 60
Venturis 28mm changed to 32mm


Engine Stats:
Heads: 021.101.371 S
Case: GA007486
Dizzy: 0231 181 012 vacuum advanced
Timing at 800rpm 7 BTDC
Timing at 3500RPM 28 BTDC

Current Dual Weber numbers:

Venturi - 32
Main Jet - 1.35
Air Correction Jet - 1.80
Emulsion Tube - F11
Pump Jet - .50
Idle Jet - .60
Starter Jet - 8of5

Any suggestions?
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1963 Beetle
1975 Westfalia

Duct tape is like 'The Force.' It has a light side and a dark side, and it holds the universe together.
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Mountain Power House



Joined: 26 Jul 2006
Posts: 879
Location: Aircooled Heaven USA


PostPosted: Mon Jan 30, 2012 8:53 pm    Post subject: Reply with quote

If that didn't work you have internal carb/ ignition/ engine issues. That combo works very well in our operating climate over and over again.
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Jake Raby
57 Oval
64 Porsche 356C Outlaw
66 Bug -The Plague Returns!
73 VW Thing (Will I ever finish it?)
73 Superbeetle (Suby Power!)
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Location: Bethlehem, Ga

1963 Volkswagen Beetle

PostPosted: Tue Jan 31, 2012 1:39 am    Post subject: Reply with quote

I am going to change the jets back to what they were and work on adjusting the main jet while observing spark plug color. Maybe we can look at it closer during the tech day.

Thanks everybody for all the help.
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1963 Beetle
1975 Westfalia

Duct tape is like 'The Force.' It has a light side and a dark side, and it holds the universe together.
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Mountain Power House



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Location: Aircooled Heaven USA


PostPosted: Tue Jan 31, 2012 11:17 am    Post subject: Reply with quote

I'd do a leakdown and compression check first. Verifying the mechanical integrity is the first step I take when something doesn't tune as expected.

What were the symptoms with the altered tuning?
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Jake Raby
57 Oval
64 Porsche 356C Outlaw
66 Bug -The Plague Returns!
73 VW Thing (Will I ever finish it?)
73 Superbeetle (Suby Power!)
76 Porsche 912E (X3!)
79 VW Iltis 4X4
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Joined: 29 Jun 2007
Posts: 330
Location: Bethlehem, Ga

1963 Volkswagen Beetle

PostPosted: Tue Jan 31, 2012 2:49 pm    Post subject: Reply with quote

I will preform a compression test this weekend and post results. But I do not have a leakdown tester to preform that test. I will see if I can get one. What do you mean by altered tuning. are you talking about the recent carb changes or what I had before. All recent symptoms were posted in the ( Well that didn't work ) post.
_________________
1963 Beetle
1975 Westfalia

Duct tape is like 'The Force.' It has a light side and a dark side, and it holds the universe together.
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