Tuning a weber 32/36

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Tweety
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Tuning a weber 32/36

Post by Tweety » Sat Aug 08, 2015 7:59 pm

Yes, its ben done before. But it takes quite a lot of study and searching to find all the information needed to get your head around the weber and its features and methods to tune it.

Thanks to Tambox for lending me the Weber Carburettors book. Great info into how the carbie actually works.

A little while ago I bought a brand new 38/38 weber synchronic. Forget it. I went against the tide hoping I'd get even more low down torque that what the new 15/55 cam would give me. It is virtually untunable for the ea81/ea82 as it is only suited to high performance highly modified engines and these engines have a head design that is not modifiable to that degree.

I recently purchased the Gunson colortune unit that came in handy. For 100 bucks its a great addition to your toolbox. Search for it on youtube.

Briefly, my newly reconditioned ea81 has 9.5:1CR, 15/55 cam for high torque at low revs, and SPFI manifold. This manifold is 6mm greater in diameter so about double the volume capacity. To install this manifold (if you go to the trouble to get one from the USA) you need to grind 2mm off the centre of the crankcase halves to give clearance, ream the 6 mounting holes at each end of the manifold (if the block/heads are shaved the holes wont meet up) and you'll need to splash some $400 on a aluminium adapter. Unlike other manifolds the SPFI one has an angled face and a large circular hole. You need to cut away at the hole to make the weber butterflies fit.

Image

The carbie- the 32/36 comes in a number of models with different chokes. I've had both my 32/36's without chokes fitted and its argued that these no choke carbs have a little less air restriction. However when starting from cold you'll need to pump your pedal 5-6 times in order for it to start. The redline 32/36 conversion kit is sold with the following jets.-

Primary/secondary mains 140/140 airs 170/160 idles 50/55

Don't be fooled, if you want the best output and cleanest engine then you'll need to change your jets.

Unlike a lot of logic the idle jets for the primary circuit operates up to 3000rpm when the idle for the secondary jet comes in. So it is critical to get that primary idle jet correct in size. So how do we do it? There are two ways.

I'll assume all other aspect of your tuning has been done- leads, plugs, timing (10-12 degrees BTDC) etc

Firstly the A/F mixture screw. This works in conjunction to the idle jet. If your idle jet is of the correct size the mixture screw should be wound out from all the way in between 1-2 turns. If it is over 2 turns then consider going down one size on your idle jet. Don't know where your jets are? google images weber 32/36 jets and you'll get a view.

The other method is as follows. Allow your engine to idle. Tune your mixture screw to its preferred best running point (I used my colortune here) then raise your idle speed to 2000 rpm. Now, slowly screw out your mixture screw...if the engine speed rises then you need to go up one size on your idle jet. Repeat this each time you change a jet. Eventually you'll get to an ideal size...in my case 60 idle was it. My mixture screw was wound out 1.5 turns.

Go for a drive. Do you have enough power on the primary? are there flat spots?

Hesitation from primary to secondary should not occur. If it does try a larger secondary idle jet. Go for a drive. Enough power? If not enough try larger main jets. in the end I got my ideal jetting at-

primary/secondary mains 145/150 air 180/180 idles 60/55
redline is...............mains 140/140 air 170/165 idles 55/50

notice that all jets are one or two sizes from redline? No great huge changes but massive change in performance. This engine is seriously improve. I did, while doing this found a stuck vacuum advance diaphragm. Had a spare handy and all was fixed.

Some comparisons. The 38/38 was dyno tuned. It struggles to get past 120kph (private road ok) The tuned 32/36 140+ and quickly to 130.

I hope you guys that want to go weber or have done so and you aren't happy with your performance try these basic methods to get it ok. Feel free to add, criticise. cheers.

Image

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[SIGPIC][/SIGPIC]Tweety trike- EA81 (full reco 2014) 32/36 weber, SPFI manifold, 9.5:1 CR, VW auto.

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steptoe
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Post by steptoe » Sun Aug 09, 2015 9:11 am

weber starting to be demystified - thanks Tony !

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Post by TOONGA » Sun Aug 09, 2015 10:14 am

I think I have a copy of the same book. I do know every time I share it on the internet it gets taken down due to copyright violation. get it while it is available ;)

http://www.filedropper.com/webercarburatormanual

I Have gone the trial and error method for tuning webers as well :) I have a 34 ADM weber (ford six cylinder 3.9 or 4.1 motor) sitting in a box now because as much as I tried I couldn't get it to be economical :)

It real fun to use on an EJ22 but once the second barrel opens forget the economy. I'm now using a vintage 32/36 weber which I got off an old hilux motor at the wreckers, with a 145 main, a 210 secondary (probably overkill but fun) Idle jets are both 60 primary and secondary air are 170, remember that my motor is 2.2 litre :) As well I'm using a modified EJ16 manifold which at a glance people have confused with the EA82 spider manifold.

Image

I get around 10l/100kms around town and at cruise on the Hwy at 100km/h I get around 8l/100kms. This is as long as I don't play too much with the second barrel :)

I've found webers way easier to tune than nearly every carby I've ever seen on a car since I first opened a bonnet in 1978.

Get the weber PDF while it is up :)

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Post by mattw » Sun Aug 09, 2015 10:58 am

Download isn't working for me. But it might just be me on a Sunday morning....

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Post by TOONGA » Sun Aug 09, 2015 11:45 am

mattw wrote:Download isn't working for me. But it might just be me on a Sunday morning....
I just checked to make sure it was still there (yes they can be that quick) and I got the link to work straight away.

It is as easy as clicking on the "downland this file link" and filling in the capture request.

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Post by Tweety » Sun Aug 09, 2015 5:35 pm

Got it, thankyou.

I read somewhere that your "airs" should be roughly 60 more than your mains. Up the mains say 2 or three sizes and you should up the airs one size. So me thinking Toonga that 210 on the secondary mains should bring with it an air at least 220 or more. Could be where the economy is suffering. Either that or lower the secondary main to 180 or so.

As said on many sites, the weber is a case of balance. With Tweety I got a feel for the difference in main jet sizes. At 130 primary mains there was little kick in the back when accelerating and the throttle needed to be wound up a lot every time you accelerated. Bit like the ea81 engine of mine prior to getting the 15/55 cam. So when I jumped to a 140 main jet it has a lot of bite in the throttle. I realised I was close to where I wanted it to be. 145 was the answer. I could have went higher to say 155 etc and although there would have been slight gains it was more a case of just throwing more fuel at it, not a real tune as such.

The secondary throat was harder to gauge. The secondary idle, if not hesitating might be well left alone at 50 or 55. The secondary mains I think is best gauged by WOT response and top end run out. Bearing in mind the Hitachi has total mains of 280, my primary (145) and secondary (150) add to 290....in the ball park.

And I think "in the ball park" is the way to go. I've experimented too much for too long.

I have several friends tinkering with their twin carb VW engines now using the colortune. This is where the colortune really shines, tuning twins for equal operation. SSHHHH....don't want all the residents of my small town coming for tune ups on their farm bashing Brumby's lol
[SIGPIC][/SIGPIC]Tweety trike- EA81 (full reco 2014) 32/36 weber, SPFI manifold, 9.5:1 CR, VW auto.

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Post by mattw » Sun Aug 09, 2015 11:45 pm

Got it this time. Must have been ham fisted with the captcha code or something.

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Post by Tweety » Sun Aug 23, 2015 9:38 pm

maybe matt,

the good news is- under 10L/100kms is achievable (I have an auto trans) because I mad eit happen today. Rode to Phillip Island and return for a trike club run. one leg was 110-115 kph and maintaining that speed up hills and used 39 litres of fuel. 30mpg. Best economy yet achieved. on my return I refuelled at Wallan then did 100 kms to Euroa sitting on 120kph (speedo was out lol) and achieved 11 L/100 kms. The stretch of 80-100 kph through the city and Monash freeway helped lower the consumption.

This is really pleasing and I couldn't believe the fuel gauge was taking so long to go down. Wont be touching the carbie now. Tinkering has ended. Also the trike gets up to 120kph easily on the first throat. No need to "gun it" all the time but when I do that roar comes with the second throat opening, no hesitation etc. really impressed.

When tyres are due I'll be buying 275/60R15 instead of the 29/50R15. 5% bigger circumference. lowering revs 150 at 100kph which will give it longer legs in each gear and improve economy a little more.

Cheers.
[SIGPIC][/SIGPIC]Tweety trike- EA81 (full reco 2014) 32/36 weber, SPFI manifold, 9.5:1 CR, VW auto.

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Post by steptoe » Sun Aug 23, 2015 11:46 pm

great result there Tony but, if we all know you ..you won't be able to help yourself to do something more to improve it :D
BTW is this on 98 fuel ?

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Post by Tweety » Mon Aug 24, 2015 12:06 am

95 fuel. I really don't want to go 98. reason being 1/ cost 2/ it seems to run a little harsher but only a little 3/ have had 98 in it and performance isn't any better.

95% of my riding is done cruising. all that 98 fuel going down the gullet of the carb for no real improvement me thinks.

By the way. pm me jonno and I can send you some weber jets if and when you are tuning your 32/36. wont cost you anything as you can put back in the box jets you replaced etc. got a small box of jets from USA recently. am not going to change my jets I have installed now that my engine is sweet.

If you take a trip down here you can have a ride of tweety and sleep in the guest bedroom. :)
[SIGPIC][/SIGPIC]Tweety trike- EA81 (full reco 2014) 32/36 weber, SPFI manifold, 9.5:1 CR, VW auto.

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Post by tony » Mon Aug 24, 2015 12:52 am

Toonga want to sell the falcon carby? I have been looking for one for the commodore.

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Post by TOONGA » Mon Aug 24, 2015 8:53 pm

tony wrote:Toonga want to sell the falcon carby? I have been looking for one for the commodore.
PM sent

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Post by Tweety » Thu Aug 27, 2015 5:40 pm

so after 100's of kms mainly freeway riding I checked the plugs and they are white. Ideal of course is light tan.
This makes me think the engine is running lean.

I have a 60 as primary idle jet and 145 as main jet. Should I raise the idle to 65 or the mains to 150 or both.?

your thoughts. Apart from this I'm happy with the economy at 30mpg and performance.
[SIGPIC][/SIGPIC]Tweety trike- EA81 (full reco 2014) 32/36 weber, SPFI manifold, 9.5:1 CR, VW auto.

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Post by Tweety » Sat Aug 29, 2015 5:45 pm

All sorted. Lesson..look at the plugss in daylight then you see the brown colour.
[SIGPIC][/SIGPIC]Tweety trike- EA81 (full reco 2014) 32/36 weber, SPFI manifold, 9.5:1 CR, VW auto.

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