Lotus Elan

Carb Balancing tools. What's the best?

PostPost by: peterako » Tue Oct 20, 2009 7:45 am

Like Terry, I have feeds on my Dell'Ortos for vacuum synch connection.

BUT....

I have found balancing them with a gauge on the end of the trumpet gives me better reults :)

Peter

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PostPost by: terryp » Tue Oct 20, 2009 7:47 am

paddy wrote: but rich enough to avoid hesitation from idle.Paddy


Paddy
I have a hesitation from idle but only when the car is super warm , does that mean I'm too rich?
Thanks
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PostPost by: paddy » Tue Oct 20, 2009 8:05 am

terryp wrote:I have a hesitation from idle but only when the car is super warm , does that mean I'm too rich?


How long have you got?

The only short answer is that it is one possibility.

I am not an expert here, but my limited understanding is that there are several things that could be causing it.

Idle mixture is one - and definitely worth experimenting with if you do have a colortune or something else that allows you adjust it reproducibly. You can get into all sorts of trouble if you just go randomly tweaking different screws and lose track of where you were.

You might have an imbalance or some other adjustment wrong which means that one or more of the carbs is idling on the progression circuit instead of the idle circuit, which will impair the take-off from idle.

Also, the ignition advance has a big effect - check the timing.

Float level also affects it - after braking hard I get a lot of hesitation initially because the levels change in the float chambers.

All of that is before you start to look at the accelerator pump and other jetting.

With the colortune one thing you can do is to drive the car until it is hot and showing the problem, then fit the color tune and have a look at what's going on under different conditions of idle, slow take-off from idle, and fast take-off from idle. The colour you see tells you something about what the carbs are doing under each condition and may give you a clue. The colortune instruction leaflet gives some useful information on how to interpret the different conditions.

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PostPost by: Galwaylotus » Tue Oct 20, 2009 8:12 am

paddy wrote:With the colortune one thing you can do is to drive the car until it is hot and showing the problem, then fit the color tune and have a look at what's going on

Be very careful if you plan to remove a sparkplug while the engine is hot. Good formula for stripping threads! At least ensure that it has been installed with antisieze and not overtorqued.
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PostPost by: alexblack13 » Tue Oct 20, 2009 8:13 am

Wow! Great info. Thanks guys..

I am about to buy a synchro and no doubt a colourtune also. I think a pair would be ideal and would allow one carb adjustment start to finish without stopping the engine etc.

Good idea?

Great stuff guys.. Thanks again.

I am off to meet Some Italians at Edinburgh airport this a.m. I will have them with me for 3 days and will give me lots of oppo's to 'arrange' the purchase of a Fiat 500 for resto. !! Plan A.. It worked great with a Lambretta!

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PostPost by: alexblack13 » Tue Oct 20, 2009 8:34 am

Terry.. As Paddy has said, Make sure all the other possibles are right 1st. I would recom' fitting electronic sparks. This gets rid of any distributer issues providing the unit is reasonably sound. I also had my carbs rebuilt by a well known expert up here and had him set them up initially. We could not 'tune out' the slight flat spot on throttle opening when hot. It just flattens and fluffs for a second then goes. I would have put money on the acc' pump jets slightly blocked or what have you. We checked them. They shot fuel across the room! Mike (stuart) recond' too rich. Acc' pump stroke was checked / adjusted. and the jets reduced one size. This very nearly cured it but not quite.

I think if it does not do it whilst engine is warming up and gets prog' worse (as it does) it points to the pump being slightly rich. I think the coloutune will spot this as Paddy says.

Mike has advised finishing run in and then final tuning this out and is expecting my car sometime next year to finish this. Meanwhile I carry on finishing the small details etc..

These tools will be a godsend for normal maintenance .

Alex..
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PostPost by: terryp » Tue Oct 20, 2009 8:47 am

Alex , Paddy
I have Lumention and the timing was set up on a rolling road last year when the car was in the UK. There is no hesitation on warm up, I changed the pump jets from 50 to 35 as per the manual , that improved a bit but perhaps more is required? I'll check the ignition as I beleive it was set up when the car was running on 95Ron + Castrol Addititive , rather than 98Ron with Castrol, whether this would make a difference I'm not sure?

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PostPost by: alexblack13 » Tue Oct 20, 2009 8:57 am

Ign timing 1st... Not sure ref' ron's and additives etc I have no exp' here.. Sorry :?

Guys?

Alex...
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PostPost by: paddy » Tue Oct 20, 2009 9:28 am

terryp wrote:I have Lumention and the timing was set up on a rolling road last year when the car was in the UK. There is no hesitation on warm up, I changed the pump jets from 50 to 35 as per the manual , that improved a bit but perhaps more is required? I'll check the ignition as I beleive it was set up when the car was running on 95Ron + Castrol Addititive , rather than 98Ron with Castrol, whether this would make a difference I'm not sure?


You're really getting to an area where I don't know what I'm talking about :) With that in mind ...

If timing is to spec, and all other carb settings are as per the spec, then yes, I'd try adjusting the idle mixture. Set the idle speed towards the low end (maybe 700rpm) so you're sure you are getting a true reading for the idle circuit and not the progression circuit. Experiment with sightly different mixture levels (I'm assuming you have a colortune or something so you can see what you're doing).

The usual advice is to make it as lean as possible, but not so lean that the take-off is impaired. As you go from "too rich" to "about right" the colour goes from yellow to blue, then as you lean it out even more it goes a darker blue. I found that If I go towards the darker blue then very quickly the running deteriorates, and the idle pickup is a problem. It can be blue, with no tinges of yellow, but only just.

As for changing the pump, I would try all the idle adjustments first. I get the impression that there isn't really a perfect setting for the pump, only one that is the best compromise for various conditions. My Weber man previously told me the only way real to know if it's right is to experiment with different settings and try them out on the road.

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PostPost by: bcmc33 » Tue Oct 20, 2009 9:33 am

Alex,

Back to your oriinal question - two of my local rolling road specialists use the Synchronizer.

I was so impressed with how quick my system was balanced last time I went onto eBay and bought what looks like a new one for ?25.
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PostPost by: terryp » Tue Oct 20, 2009 9:57 am

Alex / Paddy
Thanks for the info , more to do in the garage............

Terry
PS That Synchronizer thing looks good, Perhaps Father Christmas (if he's listening) could bring me one of those!
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PostPost by: twincamman » Tue Oct 20, 2009 11:43 am

Hi Alex --I use a unisyne to set the initial balance on the carbs -- but only after a spirited run and at 1000 rpm idle with new plugs of the correct heat range properly gaped and your points and coil in good shape - then I wait a for a few days of normal driving to read the plugs for the final tweek if needed -- to check the top end I drive the car to a steady 4500 rpm in 4 th gear and shut the key off while dumping the clutch -coast to the side of the road and read the plug there [ a quiet side road --not the 401 ]---we call it a burn out --this is done with a 115 main and a 200 air correction jet on the 7 and a 125 main and a 180 air [ stage 2 ] on 26r s2 33 at 100 feet above sea level or so -----then I kill a chicken and read the entrails while chanting naked under a full moon ------[this tells me to turn the idle mix screws 1 1/4 turns out ]--ed
Last edited by twincamman on Tue Oct 20, 2009 3:27 pm, edited 1 time in total.
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PostPost by: trw99 » Tue Oct 20, 2009 12:50 pm

Alex

When you have some time on your hands head over to this site:

http://www.innovatemotorsports.com/index.html

They have some interesting kit, but then go into their Forum and prepare to be informed! It is where Keith (type26owner) hung out and he was always worth reading.

Tim
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PostPost by: twincamman » Tue Oct 20, 2009 3:25 pm

yes ----and what a pity he was driven from this site by the constant naysaying of some members here - :( --ed
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PostPost by: frearther » Tue Oct 20, 2009 5:22 pm

terryp wrote:I bought one of these a while back for about ?30

Terry


How do they read the vacuum? Is it necessary to drill and tap the intake runners to insert nipples?
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