TB butteryfly gap

[pmessling]

Does any one know what size gap there should be on the throttle butterflys, there is no information in the engine manual and need to check mine for my high idle.

thanks
Peter

[ukkid35]

Great question Peter, there's a really big gap on mine, and I'm sure that's the issue with my high idle.

[pmessling]

I need to check mine, as i've set everything up how it should be, new TP, my new link etc, and can't get it to settle below 1500, when i started it, got it idling nicely, but when i went for a drive, shot back up again, so looking else where now, having done the o rings like you.

[gruffalo]

Wear on the throtle shafts can cause the butterfly's to not close fully, also causes Throttle Pots to give slightly spikey readings. these cure said problem.

http://www.actproducts.co.uk/shop/sp001-ajp-tp-bea...

[Gray_101]

Hi Peter , have you got a syncrometer , and tested the air flow reading on each butterfly ?

If not I'm thinking one or two of your TB s are expanding with heat and bleeding extra air round the butterflies on tick over. I seem to recall this problem being mentioned before and the TB s had to be overhauled at power or racing green

[pmessling]

yeah got a air meter, set every thing as it should be balanced the banks, TP set, adaptives set, got them all set correct using the computer and still no good after a drive. Just need to check the butterfly's and adjust or rebuild, happy doing it myself, but would be helpful knowing what they need to be set to.

Haven't tested each cylinder with the air meter yet, so can check that too.

But sounds like I'm in the right area.

Edited by pmessling on Monday 28th November 14:05

[pmessling]

gruffalo said:

Wear on the throtle shafts can cause the butterfly's to not close fully, also causes Throttle Pots to give slightly spikey readings. these cure said problem.

http://www.actproducts.co.uk/shop/sp001-ajp-tp-bea...

Yeah fitted these too

Edited by pmessling on Monday 28th November 14:01

[Tanguero]

pmessling said:

yeah got a air meter, set every thing as it should be balanced the banks, TP set, adaptives set, got them all set correct using the computer and still no good after a drive. Just need to check the butterfly's and adjust or rebuild, happy doing it myself, but would be helpful knowing what they need to be set to.

But sounds like I'm in the right area.

Just a thought, but did you try comparing the idle airflow before and after going for a drive? If it is a butterfly seating problem, you should be able to see it increase. It might even indicate one bank or the other to be looking at.

[pmessling]

No not yet, only got as far as setting it all up as per the manual then took it for a drive, so need to start again, but will check that, but if i can check the gaps before on the cold engine, then again when the engine is hot i can get a good judgement of whats happening to the TB, but has to wait till wednesday once i'm on my rest days.

So to the original question, what should they be set to, have looked around the net and a few different manufactures and seen 2thou gap around the butterfly, but don't know what the ajp is supposed to be.

[a1rak]

Im not to sure there is a particular gap they should be set to. As far as I am aware if you close the butterfly completely (throttle/ idle screw stop wound out of the away) then the engine should stall. Any gap thats left when the throttles are completely closed will cause you a problem problem.

obviously TVR tolerance produce problems in this area. I would wind the idle adjustment right out of the way and see if the engine stalls. It may just be that one butterfly is binding when the engines hot.

I made some new throttle bodies up for my 4.5 with the injector on the engine side. I used the original throttle shafts and butterflys. What I did to set them up to a closed position was warm the engine up to operating temperature, loosen (not remove) the 2 screws that clamp each of the butterfly to the spindle then gently tap each of the butterflys shut. Once it is seated correcly tighten the screws. Do one butterfly at a time, then if the spindle starts to binds you know wish one is causing the problem. You must do this with a warm engine.


When I did this I could stall my engine by shutting the throttles. If you cant stall the engine with the butterflys closed then they are worn out. Goog luck.

[ukkid35]

a1rak said:

I made some new throttle bodies up for my 4.5 with the injector on the engine side.

It's interesting that TVR started with the injectors under the butterflies in the 4.2, and then went to the apparently cruder design for the 4.5. How come you didn't use the 4.2 throttle bodies? Presumably it only makes any difference at partial throttle openings, do you get better performance or economy now? Do you have any photos? Thanks

[ukkid35]

OK found the photos now, but the thread seemed to get sidetracked for some reason...

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[julian64]

gruffalo said:

Wear on the throtle shafts can cause the butterfly's to not close fully, also causes Throttle Pots to give slightly spikey readings. these cure said problem.

http://www.actproducts.co.uk/shop/sp001-ajp-tp-bea...

I don't see how they are expected to work.

The butterfly shaft is supported between each throttle pot. The pressure is on each butterfly.

If you look at where the forces are acting the two ends where you put those bearings are the bits taking the least force!


I assume this was the only thing they could think of because putting bearings between each throttle inlet where they are actually needed would have required machining.

Unfortunately the wear will still be there because the 10mm spindle with the cut outs for the butterflies is fairly easily deformed with a finger, let alone the pressure of the engine when at tickover. So you are still going to get metal on metal rubbing in between each inlet.

As for the ops original question. I've never seen a butterfly gap stated. I assume cos its probably different for each engine based on the small amount of air leak that inevitably gets in.

On a previous thread I think I said I just tighten everying up and chase leaks until the butterflies closed can immediately stall the engine. At that point its just the throttle stop to adjust the idle. The butterfly will still be bending till it touches metal, especially if its being held artificially high by a bearing at either end.

[a1rak]

ukkid35 said:

It's interesting that TVR started with the injectors under the butterflies in the 4.2, and then went to the apparently cruder design for the 4.5. How come you didn't use the 4.2 throttle bodies? Presumably it only makes any difference at partial throttle openings, do you get better performance or economy now? Do you have any photos? Thanks

I was told that the reason TVR put the injectors on the plenuim side was in an to move them futher away from the back of the valve, as the 4.5 inlets were developed for racing i dont tink they were to bothered about part throttle openings.

I moved mine as part of the project of fitting the supercharger, I thought by doing this it might improve part throttle driving. At present the engine runs and ticks over nicely at 750rpm under lambda control and does appear to tick over much cleaner and more even.

The car needs to be mapped as its now running the K6 emerald ECU and has the supercharger on it. I will do a more detailed thread with photos at a later date.

[FarmyardPants]

a1rak said:

supercharger

Adjusting each butterfly by slackening off the screws and tapping each one closed sounds like a great idea, obvious even. Maybe that should be a service item (eg every 36k). I also suspect it is one reason why your car idles so well.

I would think that having the injectors after the butterflies would give better throttle response, especially when stabbing the throttle from low revs when some of the fuel would end up hitting the butterflies rather than (for small throttle inputs) being carried in the intake air.

[a1rak]

FarmyardPants said:

I would think that having the injectors after the butterflies would give better throttle response, especially when stabbing the throttle from low revs when some of the fuel would end up hitting the butterflies rather than (for small throttle inputs) being carried in the intake air.

not to sure i understand your thinking, why would the fuel hitting the butterfly help? The injector is designed to have an optimised spray pattern if this the hits the butterfly you might as well have a carb!.

anyway photo of install some months ago shows throttles and charger, i really don't know if any of this will work but i will soon find out!!

[ukkid35]

a1rak said:

anyway photo of install some months ago shows throttles and charger

Congratulations on the ultimate thread hijack!

[FarmyardPants]

a1rak said:

not to sure i understand your thinking, why would the fuel hitting the butterfly help? The injector is designed to have an optimised spray pattern if this the hits the butterfly you might as well have a carb!.

anyway photo of install some months ago shows throttles and charger, i really don't know if any of this will work but i will soon find out!!

Looks ace . I meant the fuel hitting the butterflies would be worse! Never mind edit: I didn't phrase it very well

Edited by FarmyardPants on Tuesday 29th November 20:44

[gruffalo]

julian64 said:

I don't see how they are expected to work.

The butterfly shaft is supported between each throttle pot. The pressure is on each butterfly.

If you look at where the forces are acting the two ends where you put those bearings are the bits taking the least force!


I assume this was the only thing they could think of because putting bearings between each throttle inlet where they are actually needed would have required machining.

Unfortunately the wear will still be there because the 10mm spindle with the cut outs for the butterflies is fairly easily deformed with a finger, let alone the pressure of the engine when at tickover. So you are still going to get metal on metal rubbing in between each inlet.

As for the ops original question. I've never seen a butterfly gap stated. I assume cos its probably different for each engine based on the small amount of air leak that inevitably gets in.

On a previous thread I think I said I just tighten everying up and chase leaks until the butterflies closed can immediately stall the engine. At that point its just the throttle stop to adjust the idle. The butterfly will still be bending till it touches metal, especially if its being held artificially high by a bearing at either end.

It helps by centreing the shaft in the throttle pot helping that run smoothly and not hold the shaft and therefore the butterflies slightly off closed.

This also prolongs the life of the throttle pots and lets them operate more smoothly.

Edited by gruffalo on Wednesday 30th November 09:20

[pmessling]

SUCCESS

After lots of fiddling I have got a steady idle of about 1000rpm, I closed the throttles by removing the throttle link bar, cable and the throttle stop, car wouldn't start which was a good sign, i also checked around the butterfly's with some feeler gauges and no gap to speak of at all.

I then put the idle stop back in and screwed it out to a 0.006 gap and adjusted the throttle link bar to the same on the other side and started the car, started off a bit high but think that was from cranking it before with petrol still being injected but settled down, was still a bit high so repeated so screwed down a little and lengthened the rod to a 0.004 gap and got a good idle of 900rpm.

I then balanced the banks to around the 4-4.5 mark, each bank being slightly different but something i could address another day by adjusting the butterfly's

Checked with the software, both TP at 12.3 with nice adaptive value.

So i think the answer to my original question as a good base to start would be a butterfly gap of between 0.004-0.006 gap for idle setting.

Took it for a drive, normal roads and motor ways, pulling like a train, great acceleration in all gears, got the engine stinking hot, pulled over a few times and idle is steady and not creeping up at all.

Happy days for sure, going to monitor it for a few days whilst driving around, might need a tweak here or there but great stuff.

From looking at the castings of the throttles there is room for improved flow, so maybe another project another time.

Thinking short induction, mainly due to having a love hate relationship with the normal hoses, what a pain in the arse even having marked them to where they go

Peter