Tuning Making a 40mm Throttle Body

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Tuning Making a 40mm Throttle Body

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Feb 11, 2011
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Suffolk/Ipswich
My background is in engineering so when I saw what Tricker used to do to the throttle bodys, I thought that looks possible and would be a challenge. We bought a cinq with the idea of converting it to electric (very slow build so far), so with anything to do with petrol engines taken off the car I had a TB to play with.
There was a lot of time spent searching old threads and thinking how I would hold and machine the parts, the butterfly is not just a round disc with two holes.
I have access to a large lathe and mill so I made a jig to hold the TB.

This is what it looks like after it has been bored out for the sleave.(note the big hole in the side)

Found some ali. tube and turned it to fit the TB.

Cutouts made in sleave and fitted.

Next bored out to 40mm, tapered front and holes drilled for spindle.

Just the spindle and butterfly to do, which is oval with one side longer and the sides at a 5deg. angle, so I made a jig to hold it.

All fitted together. 40mm & 30mm. Spacer bored.

Also made some gaskets and just waiting for someone to try it out.
Thanks for reading, I tried to keep it brief but there was a lot of steps.
Steve.
 
Nicely done think you could easily be very busy converting those for people! Interested to hear about your electric build as well always something that I like the look of but lack of lathes, mills would mean it'll be an expensive one for me although I'm sure a space could be cleared in my garage for one
 
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Nicely done. I'm sure you'll find a willing test pilot!

Others have avoided the making of the butterfly (the truly difficult part) just by ordering them from Jenvey (who seem quite happy to supply them).

Thanks.
Yes the butterfly was interesting to make (I do like a challenge) because it's at an angle so it's oval and as it's not on the centre of the spindle that makes one side longer.
I did look at Weber DCOE carb. butterflies but found they were the wrong angle.
Now I have the jig it holds the disc at the right angle and position.
 
The next thing to address in my opinion is that massive step.

Have you smoothed that out into the bore or left it as shown in the pictures?

Thanks

X
The step at the top is the taper of the casting below that it's tapered and smoothed into the bore. It could be smoothed and polished more but do not forget the 40mm TB is 78% bigger than the 30mm one.
I did have a Tricker to look at to see how he had done it.
Steve.
 
I dont know whether I am correct with this (or its all in my head) but now I have done a few more miles the smoothness and power feel like they have increased.

Does the ECU "learn" a bit over time ? - even tick over went from 1800 (which it was on my first drive) down to a nice 1000.

Dead chuffed with this upgrade
 
i have no doubt.. the old tricker 40mm TB was always one of the single best engine mods you could get... I do think one slightly smaller would probably work a little better on a engine with very few changes though, upto the point of porting heads and changing inlet manifolds and cams etc i think 36-37mm would prob flow faster and give better throttle response low down etc. But the difference the 40mm TB made to my old turbo cento's was almost unbelievable!!
 
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