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]

ditch the inlet manifold

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

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.

quote:

---

Originally posted by l0rd
ditch the inlet manifold

---

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.

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.... 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]

I vote forced induction and keep the ford manifold

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

quote:

---

Originally posted by big_wasa
I vote forced induction and keep the ford manifold

---

Where's Claire? She's done ITBs to a couple of Mazda V6s recently....

Thanks for the tip Steve - I have sent Claire a U2U

U2U replied to

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.

---

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]

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 !

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

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

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 .

---

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]

---

interestedparty - 24/7/10 at 04:40 PM

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

---

RazMan - 24/7/10 at 04:59 PM

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

---

iti_uk - 25/7/10 at 08:05 PM

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

---

RazMan - 5/8/10 at 07:34 PM

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?

---