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]
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.
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?
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.
One thing I would recommend, the throttle quadrant could be made more progressive giving better throttle control at low openings. I’ll get around to sorting mine one day!, it would have been easier to sort out when I made the manifold and repacked the TBs
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.
quote:
Originally posted by ttalps2000
I have just fitted GSXR750 SRAD throttle bodies to my zetec. they are 45mm.
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.
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
quote:
Originally posted by snapper
What is the inlet port size at the head face on a Duratec?
I’ve 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]
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]
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 ¼ valve diameter valve lift however the more time the valve is open at more than ¼
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.
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 ¼ valve diameter valve lift however the more time the valve is open at more than ¼ 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.
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...!
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
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 :-)
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...!
Nice work Sebastiaan.
Love the Alfa Sebastian, nice work
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.
Following with interest. Keep us posted.
quote:
Originally posted by garyt
Love the Alfa Sebastian, nice work
quote:
Originally posted by SPYDER
Nice work Sebastiaan.