RazMan
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| posted on 18/7/10 at 12:15 AM |
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Thinking about ITBs
My ST200 V6 engine could do with a few more horses so I am thinking about options. Throttle bodies would be an obvious choice but the inlet system is
a little unconventional and has each 4 valve cylinder's inlet divided into twin ports (~15mm) in an effort to give better torque lower down in
the rev range. BTW I have gutted the secondary butterflies for ease of mapping and the fact that a 725Kg car doesn't really need more low down
grunt.
So how would I install ITBs? Do I fit 12  small TBs or 6 larger TBs with a Y section into each cylinder?
Any idea how much extra power ITBs would give?
 
ST200 Manifold
[Edited on 18-7-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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l0rd
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| posted on 18/7/10 at 12:45 AM |
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ditch the inlet manifold
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paulf
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| posted on 18/7/10 at 08:09 AM |
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Make a new manifold or remove the section in the inlet between the 2 ports and make some oval joiners to attach the TBs.
However if hoping for more power then the best way would be a new custom manifold assuming the head design allows a single inlet runner into each
cylinder.
Paul
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MakeEverything
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| posted on 18/7/10 at 08:10 AM |
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Get a flange lazer cut with an oval port which covers both ports. Then, get a suitably sized piece of pipe and squash one eng to an oval, which will
give you a round top and an oval to weld to the flange.
Then you should be able to connect a TB via a silicone connector.
Thats what i was doing and it would have worked really well.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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RazMan
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| posted on 18/7/10 at 08:52 AM |
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quote:
Originally posted by l0rd
ditch the inlet manifold
The heads are dual port so the manifold is only part of the story 
Paulf / MakeEverything - Sounds like you are both on the same lines and looks feasible.
I might find a scrap lower inlet manifold and simply TIG the alloy oval / round tubes on the top. That would give me round stubs to attach TBs by
silicone hose. That would give me two sets of triple TBs so I am thinking that Triumph Speed triple TBs would be a good candidate. The only problem
that I can see will be the spacing between TB centres but I guess that I can lose a few mm during the 'oval to round' conversion.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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suparuss
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| posted on 18/7/10 at 08:58 AM |
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pretty sure this will have been done before. with you on the principle, makes sense to ditch some torque with a lighter car!
id have thought 6 bike throttle bodies would be plenty big enough. R1 throttle bodies with enough air flow for 180bhp at 11000 rpm, so that equates to
45bhp per cylinder (0.5 ltr per cylinder) so 270bhp at 11000 rpm for 6 cylinders. you probably wont need 11000 rpm worth of air flow though but you at
least know the TB's are up to the job.
pretty simplistic way of looking at it i guess.
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James
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| posted on 18/7/10 at 09:24 AM |
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quote:
Originally posted by RazMan
quote:
Originally posted by l0rd
ditch the inlet manifold
The heads are dual port so the manifold is only part of the story
Paulf / MakeEverything - Sounds like you are both on the same lines and looks feasible.
I might find a scrap lower inlet manifold and simply TIG the alloy oval / round tubes on the top. That would give me round stubs to attach TBs by
silicone hose. That would give me two sets of triple TBs so I am thinking that Triumph Speed triple TBs would be a good candidate. The only problem
that I can see will be the spacing between TB centres but I guess that I can lose a few mm during the 'oval to round' conversion.
Or, two sets of GSXR throttle bodies (which are respacebale and remove one TB from each set!
HTH,
James
------------------------------------------------------------------------------------------------------------
"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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SPYDER
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| posted on 18/7/10 at 10:31 AM |
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Or.... three sets of V twin throttle bodies mounted sideways.
Might be a little on the large side though, internal bore wise.
Possibly SV650 ones? They will be smaller than RSV or Suzuki 1000.
And the throats on RSV ones already point down at an angle towards the heads. Could be mounted with silicon tubes on to short stubs.
The top face is flat, could make plenum fabrication a little easier.
Geoff.
[Edited on 18/7/10 by SPYDER]
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big_wasa
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| posted on 18/7/10 at 11:19 AM |
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I vote forced induction and keep the ford manifold 
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RazMan
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| posted on 18/7/10 at 11:26 AM |
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suparuss - 11,000rpm
The redline on my V6 is 7500rpm (and that's pushing it a bit) so I would think the R1 TBs would be a bit on the small side. I am presently
getting ~230bhp so I am thinking of Triumph Speed Triple TBs. These have a bore size of 47mm and look as though they will be a good candidate. I just
bagged a set on eBay for £15 so I won't be too disappointed if they don't fit.
Spyder - The heads have flat mating surfaces so no need for V twin TBs. Interesting idea though 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 18/7/10 at 12:14 PM |
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quote:
Originally posted by big_wasa
I vote forced induction and keep the ford manifold
That was certainly high on my options list but being a V6 it would ideally need 2 small turbos (like the Noble) and after getting quotes for new
exhaust manifolds, uprating the oil supply etc, I decided NA was the most cost effective way to go. I considered a single turbo but it would be too
far away from the exhaust ports and therefore quite laggy.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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stevebubs
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| posted on 18/7/10 at 03:50 PM |
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Where's Claire? She's done ITBs to a couple of Mazda V6s recently....
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RazMan
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| posted on 18/7/10 at 04:53 PM |
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Thanks for the tip Steve - I have sent Claire a U2U
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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clairetoo
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| posted on 18/7/10 at 05:49 PM |
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U2U replied to
Its cuz I is blond , innit
Claire xx
Will weld for food......
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RazMan
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| posted on 20/7/10 at 11:12 AM |
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Many thanks Claire - some good tips
My Triumph 955i TBs arrived today It would be great if these could be adapted for a few reasons:
1. Ridiculously cheap (£15)
2. No injectors to worry about
3. Nearly the right spacing
4. Simple Throttle linkage
 
Triumph 9551 TBs
... and I now face my first challenge (one of many I suspect) The distance between bores is about 100mm on the V6 and 90mm on the TBs, so my question
is ....
I need to 'blend' the circular bore of the TBs to the oval shape of the combined twin ports but can I lose the 10mm mismatch by fabbing an
adaptor as MakeEverything suggested?
quote:
Originally posted by MakeEverything
Get a flange lazer cut with an oval port which covers both ports. Then, get a suitably sized piece of pipe and squash one eng to an oval, which will
give you a round top and an oval to weld to the flange.
Then you should be able to connect a TB via a silicone connector.
This will obviously mean that the ports will be slightly different lengths but maybe I can adjust the lengths of the intake trumpets to compensate? I
believe the Rover V8s do something like this.
[Edited on 20-7-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 22/7/10 at 08:26 AM |
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I will probably forget the Triumph TBs and put them back on eBay because they are very tricky to cut'n'shut to the right spacing – ah well
it was worth a try.
Meanwhile I've had a Locost idea!!
Looking closely at the original Lower Inlet Manifolds, they are almost like simple throttle bodies, as they had butterflies (since removed) in
the secondary ports
 
ST200 LIM
 
LIM closeup
The shafts obviously run through the primary ports so how about machining flats on the shafts and installing identical butterflies, possibly from a
donor set of LIM? Measuring the ports, I find that they are 33mm & 35mm so new butterflies would have to be made, but it's not rocket science
is it?
All that would remain is to fab some kind of idle stop, TPS connection and return spring for the new throttle linkage.
This mod would have the advantage of using the existing casting, injectors and fuel rail instead of buying new TBs, and they are obviously already
matched to the ports perfectly. Add a set of twelve trumpets and the job's complete…….. as I say, all this is in theory and I welcome any
comments or suggestions.
What do you think?
[Edited on 22-7-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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clairetoo
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| posted on 23/7/10 at 06:55 PM |
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How about getting the 33mm ports machined to 35mm (I would think they are just cast at the mo' ?) , then all the butterflies would be standard
parts
Then blend the upper end to an obround (port shape...) , and have some one make matching shaped trumpets (in CF , natch ) .
That would look awesome !
Its cuz I is blond , innit
Claire xx
Will weld for food......
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RazMan
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| posted on 23/7/10 at 07:55 PM |
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That's a great idea Claire, but surely there will be some mismatching between TB/manifold and ports won't there? Unless they are tapered
in some way but that will be a bit of a challenge for a machinist.
Isn't a butterfly just a fairly simple disc made of brass or similar material? Admittedly any machining will have to be pretty accurate to get
sync between the bores exactly right, but maybe with a needle valve in each primary bore at least a steady tickover should be achievable?
Another question springs to mind - how the hell do I calculate the lengths of the 12 inlet trumpets?? I suppose each bore could have it's own
length to spread the torque a little bit like the original design.
Also, I wonder who could fab some CF trumpets for me 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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clairetoo
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| posted on 23/7/10 at 08:20 PM |
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The thing with butterfly's is that they are not round - if they were , they would rotate rather than stopping and closing off the flow .
I did work out a locost way of making some when I was considering boring out some throttle bodies - it wouldnt be easy , bit not impossible !
Making the trumpets would be a challenge - and I love a challenge
Its cuz I is blond , innit
Claire xx
Will weld for food......
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RazMan
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| posted on 23/7/10 at 10:30 PM |
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quote:
Originally posted by clairetoo
The thing with butterfly's is that they are not round - if they were , they would rotate rather than stopping and closing off the flow .
Ah yes, I had suspected that they might be slightly oval. Well, they say you learn something every day ..... How about laser cutting some?
I'm trying to source a couple of manifolds now so we will see what happens.
The earlier ST24 LIM has 32mm/34mm bores so maybe they would work better, boring the 32mm bores out to 34mm although I'm not sure if the extra
1mm will hurt the flow much.
quote:
Originally posted by clairetoo
Then blend the upper end to an obround (port shape...) , and have some one make matching shaped trumpets[/quote
I'm not quite sure I follow you there (it's late and I've had a few glasses of a very nice Shiraz ) - do you mean blend each of
the port 'pairs' into one oval shape and then put 6 trumpets on top?
[Edited on 23-7-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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interestedparty
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| posted on 24/7/10 at 04:40 PM |
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Have you thought about putting a Jag 3L V6 in there? Supposed to be 240 as standard, with a free flowing induction and exhaust system should be a bit
more
No substitute for cubes
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
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RazMan
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| posted on 24/7/10 at 04:59 PM |
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Indeed I have but TBH the work involved (not to mention the cost) doesn't make it viable..... and SWMBO would chop off parts of my anatomy if I
started shelling out serious cash again
I have now got 2 sets of LIMs on their way to me and I've got the drawing board out again
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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iti_uk
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| posted on 25/7/10 at 08:05 PM |
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Lol, back when I was considering the Duratec V6 for my swap, re-using the lower manifold casting was going to be my method! Good luck with it,
I'd be very interested to see how it turns out.
Chris
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RazMan
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| posted on 5/8/10 at 07:34 PM |
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Trumpets?
Initial inspection is promising and it looks as though it might be easier than I first thought. I have just bagged some bigger injectors which
should suit the extra airflow and I am waiting for quotes to come back for the conversion work[crosses fingers]
One question for the collective brains here - how do I calculate the length of the inlet trumpets? I am not into racing so I just need a broad spread
of power around say, 3000 - 6000rpm (which is where the fun is) but I am still wondering whether to blend each of the port pairs into 6
'obround' shapes or go for 12 tiny trumpets - or would that look like a church organ sitting on top of the engine?
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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