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Author: Subject: Bike throttle bodies
flak monkey

posted on 20/4/20 at 08:46 AM Reply With Quote
Bike throttle bodies

I'm a little out of touch these days, what are people using for re-spaceable bike throttle bodies now?

I'm building another Duratec (circa 210bhp spec) to swap into our Mk1 MX5 (build thread coming soon) and am considering going down the bike throttle body route. Obviously looking for something around 45mm size.

I recall ZX10R, GSX1000 and R1 being popular - anything changed in the last 10 years?!

[Edited on 20/4/20 by flak monkey]





Sera

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cliftyhanger

posted on 20/4/20 at 08:56 AM Reply With Quote
I thought the early GSXR ITBS are about the only ones that are easily respaceable? But you still need an inlet of some kind.

Not that it matters a great deal, DanSt will do a manifold to suit just about anything.

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snapper

posted on 20/4/20 at 10:00 AM Reply With Quote
Very timely post as I am about to embark on a similar build.
I have a high mileage Fiesta ST engine that will probably need a bit of work to get it ready and a set of Mikuni bike throttle bodies. They paired together like Jenvey and are 42mm, are these likely to limit my bhp as I note you are looking for spaced 45mm?





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ttalps2000

posted on 20/4/20 at 10:22 AM Reply With Quote
I have just fitted GSXR750 SRAD throttle bodies to my zetec. they are 45mm. Not a DanST conversion though. However they are very easy to fit etc.
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rusty nuts

posted on 20/4/20 at 12:06 PM Reply With Quote
One thing I would recommend, the throttle quadrant could be made more progressive giving better throttle control at low openings. Iíll get around to sorting mine one day!, it would have been easier to sort out when I made the manifold and repacked the TBs
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flak monkey

posted on 20/4/20 at 12:44 PM Reply With Quote
quote:
Originally posted by cliftyhanger
I thought the early GSXR ITBS are about the only ones that are easily respaceable? But you still need an inlet of some kind.

Not that it matters a great deal, DanSt will do a manifold to suit just about anything.


I can make the manifold myself, isn't an issue. Just wondered if there were any new options or if we are still using the same stuff we were 10 years ago.





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SPYDER

posted on 20/4/20 at 01:59 PM Reply With Quote
quote:
Originally posted by ttalps2000
I have just fitted GSXR750 SRAD throttle bodies to my zetec. they are 45mm.


Are you sure they are 45mm? I have some K1-K2s in my garage that are 42mm from the butterfly onwards. What year are yours? I've never seen any bigger ones apart from GSXR1300 which are nominally 46mm. Even these are only 46mm at the butterfly, after that they taper down to 42mm. I've bored mine out to 45mm.

With regard to power potential I was advised to go up from 42mm to 46mm as my new engine build was being specced for 220-230bhp. I was told that 42mm would likely start to pose a restriction at 200+.

As previously mentioned it can be worth fiiting a larger throttle quadrant and it can be offset to give a "rising rate" progression. I made a nylon one 75mm dia which gives about 55mm of cable pull. It is simply screwed to the original quadrant. The spindle is where the red dot is. The change of cable angle is allowed for by the little rose joint.



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ttalps2000

posted on 20/4/20 at 02:34 PM Reply With Quote
i measured 45mm at the inlet to the throttle bodies, so most likely taper down to 42mm. I bought my setup 2nd hand and it has all been sealed up etc, so i wasnt going to split it open to start measuring etc. Might do what you have on the throttle quadrant.
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snapper

posted on 20/4/20 at 05:43 PM Reply With Quote
What is the inlet port size at the head face on a Duratec?
If less than 45mm then your increasing port speed.
Interested to Get some ideas on how to proceed





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SPYDER

posted on 20/4/20 at 06:17 PM Reply With Quote
quote:
Originally posted by snapper
What is the inlet port size at the head face on a Duratec?



A quick google suggests the port size is 50 x 37mm which works out equivalent to a 44.5mm circle.

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snapper

posted on 20/4/20 at 06:22 PM Reply With Quote
Iíve done some calculations on inlet valve area and throttle body area
Duratec inlet valve diameter 35mm area = 9.62 sqcm x 2 = 19.24 sqcm
Bike throttle body diameter 42mm area = 13.85
45mm area = 15.90
46mm area = 16.62
Fiesta ST150 throttle body 55mm area = 23.76

Inlet port 50mm x 37mm Area = 18.5 Sqcm

[Edited on 20/4/20 by snapper]

[Edited on 20/4/20 by snapper]





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SPYDER

posted on 20/4/20 at 07:02 PM Reply With Quote
The 50 x 37 is a flattened oval shape. Area is 15.56 sq.cms

Duratec has flippin' big valves doesn't it!

[Edited on 20/4/20 by SPYDER]

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snapper

posted on 21/4/20 at 06:02 PM Reply With Quote
Big valves in total yes but as valves only present fully opened for a short time there is a lot of time when they are either opening or closing (area under the curve I believe). Valve cannot flow anymore air past ľ valve diameter valve lift however the more time the valve is open at more than ľ valve diameter lift the more time it will flow at maximum.

Back to my issue, my 42mm throttle bodies may not provide the flow I need dam it.
So now I need to seriously decide on an approach to this build, a plenum would allow a 60mm single throttle body and the option to boost it.

I am once again conflicted.





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flak monkey

posted on 21/4/20 at 06:54 PM Reply With Quote
quote:
Originally posted by snapper
Big valves in total yes but as valves only present fully opened for a short time there is a lot of time when they are either opening or closing (area under the curve I believe). Valve cannot flow anymore air past ľ valve diameter valve lift however the more time the valve is open at more than ľ valve diameter lift the more time it will flow at maximum.

Back to my issue, my 42mm throttle bodies may not provide the flow I need dam it.
So now I need to seriously decide on an approach to this build, a plenum would allow a 60mm single throttle body and the option to boost it.

I am once again conflicted.


42mm should do it, they will be at their limit around 280hp (around 70hp/cylinder based on around 300cfm flow)

45mm would support up to around 320hp (around 80hp/cylinder based on 360cfm)

Stick with your plan...will be 'reet

I've just got hold of some cheap R1 throttle bodies - early ones with the vac slides in, so they are a cross between CV carbs and throttle bodies, although all fuelling is done via the injectors. I'm interested to try them out as they should give very good low end torque and throttle response. Will soon find out...!





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SPYDER

posted on 21/4/20 at 08:35 PM Reply With Quote
quote:
Originally posted by flak monkey

I've just got hold of some cheap R1 throttle bodies - early ones with the vac slides in, so they are a cross between CV carbs and throttle bodies, although all fuelling is done via the injectors. I'm interested to try them out as they should give very good low end torque and throttle response. Will soon find out...!


The early R1 ITBs do look intriguing. The vacuum slides look to me to be an alternative to the secondary butterflies found in some GSXR ITBs. Were they to "soften" the initial impact of full throttle?
How would "load" be measured ? The TPS signal would seem to be somewhat irrelevant as the slides would be dictating airflow. I wonder if the slides might help to give a more meaningful MAP signal than is usual with ITBs?

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snapper

posted on 22/4/20 at 06:52 AM Reply With Quote
quote:

42mm should do it, they will be at their limit around 280hp (around 70hp/cylinder based on around 300cfm flow) 45mm would support up to around 320hp (around 80hp/cylinder based on 360cfm) Stick with your plan...will be 'reet



Thanks for that, Iím going to put the Duratec in an old Fury I picked up and whilst I was seriously considering a supercharger building the engine up with what I have would substantially reduce the costs, not that thatís much of an issue but I could learn but I am going to learn a lot whilst Iím doing this.
If youíll forgive me I will probably mirror your build then once the Fury is fully up and running look at getting another Duratec and charging that





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sebastiaan

posted on 22/4/20 at 06:58 AM Reply With Quote
I actually have the R6 version of the "CV slide" ITB's on my alfa project. TPS as load indicator works well, but I am yet to try MAP. They respace easily, just the fuel rail takes some work. I cut & welded.

Pictures in this album: https://myalbum.com/album/qoUBQZ54GA4h

Has DanST velocity stacks on there as well :-)

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SJ

posted on 22/4/20 at 08:10 AM Reply With Quote
quote:

I've just got hold of some cheap R1 throttle bodies - early ones with the vac slides in, so they are a cross between CV carbs and throttle bodies, although all fuelling is done via the injectors. I'm interested to try them out as they should give very good low end torque and throttle response. Will soon find out...!



If ever I decide to inject my Zetec I was planning on using an old set of ZX6 carbs, re-spaced and used as throttle bodies, attached to the standard plastic Blacktop manifold modified to take the ZX6 rubbers. That way I can use any standard or after market Zetec injectors / fuel rail parts.

May never get round to it though.

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SPYDER

posted on 22/4/20 at 06:41 PM Reply With Quote
Nice work Sebastiaan.
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garyt

posted on 23/4/20 at 08:16 AM Reply With Quote
Love the Alfa Sebastian, nice work





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flak monkey

posted on 23/4/20 at 05:50 PM Reply With Quote
Good info, thanks guys.

Here's some pics of the R1 throttle bodies.

This is what they looked like when they turned up. They are ~40mm bore, slightly smaller than I thought (was hoping they were 42mm, but they should still work ok for road use).





Interestingly they have a wax stat attached which controls air bleed valves in each body - this appears to act like an air bypass for warm up, much the same as an IAC would on true EFI. I'm not planning to retain it since they are (according to some google research) quite temperamental and prone to siezing up. I'll be removing it and going down the electronic IAC route as usual with EFI.

I am planning to retain the injectors in the Duratec head, and for reference the ones fitted to the current 2.5l engine in the Mazda are around 300cc/min and super cheap (I got a set for $75USD shipped). These will work great for an engine with throttle bodies and 210hp spec cams. This leaves the holes in the throttle bodies which I might use as the air bypass for the IAC, currently undecided.

Anyway, this is what they look like stripped of everything I'm not going to use. I will split them and respace them to suit the Duratec inlet spacing.











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SPYDER

posted on 23/4/20 at 06:50 PM Reply With Quote
Following with interest. Keep us posted.
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sebastiaan

posted on 24/4/20 at 07:12 AM Reply With Quote
quote:
Originally posted by garyt
Love the Alfa Sebastian, nice work


quote:
Originally posted by SPYDER
Nice work Sebastiaan.


Thanks! Lots more to digest here, auo-translated from Dutch: a tale of woe, rust and a plastic italian car

Flak, keep going, this is going to be good!

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