Balancing Throttle Bodies

Balancing Throttle Bodies

Author
Discussion

smighall

Original Poster:

105 posts

169 months

Sunday 28th June 2015
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I've had my throttle bodies modified by Andy to have the bearings fitted and have put them back on the car. When i'm trying to balance them cyl 3 is only registering about 2.5 on my synchrometer with the idle sat at 900rpm where as 2 and 1 are already around the 7 mark.

Does that sound like there's an air leak or that i just need back off all of the balance screws and wind up the idle screw a bit more to get #3 in the right sort of ball park before i move on? I've already had to order some new balance springs as #4 doesn't actually close enough so is already sitting at 10cfm without anything pushing on the linkage, i can easily reduce this by lifting the linkage so hopefully new springs should help that one.

Andy_mr2sc

1,223 posts

175 months

Sunday 28th June 2015
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Hi Sean
When balancing the bodies you should start at three and work outwards so 3,4,2,1,5,6. Regarding the springs I've often seen these go soft and not work as they should. Well worth changing as they are only ~£1 each at RG or whatever they are calling themselves these days!
Hope this helps.

Andy.

TAM747

270 posts

248 months

Sunday 28th June 2015
quotequote all
here is a pic (thanks) from the german tvr forum, shows exactly where/how to balance 1 - 6

start with 1, means: idle and throughflow 3rd cylinder, then 2., 3. and so on ...





smighall

Original Poster:

105 posts

169 months

Sunday 28th June 2015
quotequote all
Yes started at cylinder 3 and it was really low on the synchrometer. To get it anywhere near 5-7 i think i'd have to really start opening the body up, so i'm thinking there must be an airleak on that cylinder potentially, I did try winding the idle up a bit but it was making very little difference to the CFM for #3 which seemed quite strange to me.

I refitted all the bodies with Powers gaskets that i've had sat on the shelf a while so hopefully they should be sealed properly.

I'll have another go once i get the new springs through, probably next weekend now.

Edited by smighall on Sunday 28th June 19:04

twinreal

300 posts

154 months

Sunday 28th June 2015
quotequote all
First start with mechanically syncing the gaps of all six butterflies via the linkages. You can use a small drill, i.e. 1mm for this.
Then as wrote above, start with cylinder 3 and sync it to 5-7 via syncrometer. If idle is too high after this, reset the throttle pots via diagnostics software. Then as wrote above sync the other ones beginning 2 - 1 - 4 - 5 -6. And finally reset throttle pots again + reset mapping.



Edited by twinreal on Sunday 28th June 19:06

smighall

Original Poster:

105 posts

169 months

Tuesday 30th June 2015
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Did it again today and got them all pretty much spot on, although still need to replace the springs as the 4-5-6 cylinders won't go low enough as the springs have lost their strength i think.

One other question, I assume once setup you need to get it up to temperature and then reset the idle again?

TAM747

270 posts

248 months

Wednesday 1st July 2015
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yes.

smighall

Original Poster:

105 posts

169 months

Thursday 2nd July 2015
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Thanks,

and thanks for the PM too. The tip about using a drill bit to get them all mechanically balanced first really makes it a lot easier!

Curdster

481 posts

183 months

Friday 10th July 2015
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I had mine bushed by Alan and had the same balancing issues. Eventually took it to Neil Garner to sort. When buying the springs, buy 2 packs as even though they are new I had 1 which collapsed in 48 hours and had to wait for the post again for another pack. I also had difficulties as the new gaskets supplied by Alan move th pots ever so slightly away from the head, and then I foudn I had alignment issues with the other linkage and had ever so slightly moved the contact points on each arm.

m4tti

5,426 posts

154 months

Friday 10th July 2015
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Curious... What difference did it make moving the throttle pot away from the head. It's attached to the throttle body and motion is provided by the butterfly spindle.

Curdster

481 posts

183 months

Friday 10th July 2015
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Sorry typo. Bodies not pots

Curdster

481 posts

183 months

Friday 10th July 2015
quotequote all
Sorry typo. Bodies not pots

smighall

Original Poster:

105 posts

169 months

Friday 10th July 2015
quotequote all
Finally took the Tuscan out for a run this morning and the difference is amazing! Really smooth all the way through the rev range, rock solid idle and no more flat spots.

I don't even think my bodies were too bad, certainly couldn't feel much play in them but with the bearings now in things just seem to be how they should be. Very happy and would definitely recommend Andy for getting the work done!

Sagi Badger

589 posts

192 months

Friday 10th July 2015
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Ummmhhh, the TP is on the spindle so the TB could have 20 gaskets and still do its job, as mentioned. The alignment of each TB has entertained me many times, I have thought long and hard about this but really the best solution is spending time aligning them and slowly tightening up to avoid the twisting and turning that occurs.

These throttle bodies require careful alignment of the butterfly on the spindle as well, so be careful that the balancing issues are not due to a nearly closed but not correctly positioned butterfly.

J