Balancing Butterfly's

way back in March of 2004 Mike Lane posted that he was having trouble with engine fluffing when pressing accelerator, turned out that the butterfly’s weren’t balanced correctly and air flow was all over the shop. He is/was running an Emerald ECU and the optimal reading for each is 5 (5 of what i’m not sure but 5 it is) There was talk that the value is different if running a Lotus ECU, 8 rings a bell? Can anyone confirm this? I used to have the manual but that computer packed up long ago so I can’t check. The car has the 190 upgrade. Thanks for the help.

Mike had removed the IACV, this is why the balancing became crucial.
Normally your engine will have one, and this is the only way to achieve a safe and respectable idle with the Titan throttle bodies, as they lack a proper balancing system.

The Jenveys do have one, so it’s safe to remove the IACV, but in the Titan case it’s false economy.
The Titans have only one screw that can balance the two pairs, left to right, but is very basic.
Maybe removing it to save 200gr would make sense on a very stripped car, but mainly one where idle is not going to be seen.

As far as the numbers go, it doesn’t matter, the numbers should only be equal, whatever they read.

Yeah the figure isn’t important. A venturi balancing tool simply pulls a vaccuum at a given throttle opening and you are looking for the same vaccuum on each venturi at set throttle opening. Before I bought a propper tool, I always used a length of rubber tube and my ear, and you make it so the noise is the same, and it is actually remakably accurate!!


If you are not using an IACV and you are using an Emerald then it is important to set the airflow volume per barrel somewhere near 4.5-5KG/hr or you will not be drawing enough air to give a decent/sustainable idle on cold start. Even with an IACV, your TBs need to decently balanced since inbalances will be carried through to all throttle positions and the IACV cannot smooth these out other than at idle. Air imbalances will also lead to imbalances in air/fuel ratio between cylinders with some running lean and others rich. If you do alter the balance and overall airflow values you must re-align the throttle pot and ensure the fuelling is still correct or the map may run skewed.


Very important on the Jenveys, nigh impossible on the Titans.

If Titans, leave the IACV on.

Jeepers…you guys know how to scare folk don’t you!! I think I have decided its running just fine, maybe I will just clean and oil the filters!! Thanks for your technical input. I will just check that nothing is too weird and leave well alone!!

I got the meter from Demon Thieves for around �25 quid and it is very easy to use - if you are ever down my way, I would be happy to stick it in your orifices !!!

I had my butterfly inspected balanced at DVA yesterday but Dave cannot balance the first one as it is readying about 8kg/hr while other 3 reads out about 6. This is the reason he suggested that this causes the HIGH idle when HOT. He is suspecting a bent butterfly spindle on the first TB but cannot be confirm yet!!!

Anyone can shed some light on this? cheers

My IACV is removed if that will caused that?

wow - a blast from the past - i thought a couple of the originals had come back to post until I read the post dates. You must have been digging through the archives!

If the spindle is bent can’t you see or feel it getting tight somewhere in it’s opening arc?

As far as i can see i cannot feel anything as this is what DVA suggested. I had gone through all the archives to identify the problem but without success. Just wonder are there any vhpd specialist in the North West area? :wink:


Can’t they be adjusted on the spindle - I thought that there was a grub screw. maybe they have just moved a little off centre?

Dave at DVA had tried to adjusted for me but apparently the screw is adjusting by pair? (for 2 throttle bodies). By the time it adjust the first one, the second is off and so on. But i have no idea as i am not familiar the throttle adjustment on the K…it idles better now but still a bit irritated by not so smooth idle hunting… :frowning:

He’s right!!!

Haha…it is still lumpy but it still hunting idles from 1.5k-2krpm when hot but is a lot better than before.

Ollie Sadler at Phoenix Motorsport, Accrington, well worth a try.

cheers guys, i will give Ollie a call Monday!!

Now is booked in for Ollie to look at next week!!! :slight_smile:

Did you sort this???


yes i did as i took it out check and cleaned, it works fine now but don’t know for how long