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Nick Jones

Plenum Manifold To Throttle Bodies?

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As I'm running a fairly daft cam I have some minor low speed running issues.  This seems to be the result of reversion in the plenum/runners.  Though not a big issue in the scheme of things it does get irritating in traffic queues - and this is Britain - we have lots of queuing traffic.

 

So a late night ebay session resulted in this......

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BMW K1100 throttle bodies.  3 sets.  Enough for 12 cylinders......  35mm ID and all separate castings bolted into a ladder frame.  Injector provisions must be made elsewhere.

 

Won't happen quickly but I'm thinking about it!

 

Nick

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Won't happen quickly but I'm thinking about it!

 

 

 

Maybe not, but that has the potential to look so pretty on a Six, just imagine a row of six with mesh trumpets so you can see the butterflies!

 

Alan

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Nick,

As ever, never knowingly underengineered!

 

But (and I know you knew I was going to say that) are those Tbs big enough?     I researched motorbike Tbs a while ago, and found none that were.   And even the BMW 1200 had 'only' 1171ccs, on a four cylinder thats neraly 100cc (86) less/cylinder than a Triumph six.    But the proof is in the power output.  I'll watch this space, with eager anticipation!

 

On the injectors, just back from Silverstone Classic.   Rather than injectors mounted in the Tb, a popular racing position is off the Tbs, on a rack, with the injectors pointed into the intake, straight at the middle of the butterfly.   This said to allow bigger injectors and more top end power, thanks to better atomisation.    This is a picture I found of a nice DiY effort on a Golf GTi.

 

John

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Edited by JohnD

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All injectors before the throttle have the disadvantage

that under bad topographics the fuel drops out of the manifold

Also spraying against the closed plates is bad from several reasons.

So that is best for racing where plates are mostly open and bad

for street use where plates are mostly closed.

 

If this systems catches a fire maybe from backfire its a big problem.

 

I did see some BMW systems and was impressed from the precise mechanic.

Its like a big clock........

Although I would prefer the PI manifold where it fits because it has all we need

and can be made plug and play quickly on a TR6.

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Big enough.....?!  Oh yes.  At the moment I run a single, just one (1) x 54mm TB.  At 22.8 cm2 this has almost exactly the same flow area as 2 x 1.5" carbs though maybe does slightly better by having only a single throttle shaft.  So based on Alan's extensive testing of Strombergs, probably a bit small for my engine.  I still need to confirm this by doing some data-logging

 

3 x 35mm gives 57.7 cm2, so well on the way to triple the area.  The ports themselves are 30mm.

 

Actually, my problem has been finding them small enough.  I have a set of PI TBs.  They are 46mm and too big.  Bonnet clearance issues on a Vitesse too.  Bike TBs also tend to be too big, especially if you go looking on the small displacement sports bikes.  You need to look a the big displacement cruisers, tuned for torque.  GSX 1400 is a good one, but they are very expensive.  That K1100 lot cost under £100 delivered.

 

I'll put the injectors near the head as they are now.  On the whole, when you see injectors placed like that Golf they are actually part of a staged injector set-up with each cylinder having two injectors - one relatively low flow one mounted near the head that takes care of idle and low speed running and one outside the throttle as shown that only comes into play at full chat.

 

Nick

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Indeed,the sierra RS500 had twin injectors, but the std cossie on single I think

 

John, I find it difficult to believe you couldn't find bike ITBs big enough! Mine are off a 1000cc bike, and are 42mm (tapered from 45ish) and are good for up to 220bhp on a 4 cylinder (wish I could squeeze that out of mine!) so that is 55bhp/cylinder. 

There are some good pointers on the Jenvey website about choosing throttle body size. 

 

And to throw a little extra, when I had my car on the rollers, teh very knowledgable tuner was saying how the latest cars (ford Duratec was mentioned) are going to very large ports and throttle bodies. And this is on what is used as shopping cars and super economical.......

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Nice one Nick.

 

As it happens, there's a set of these on their way to Camberwell as well (saw them on a mates old Bimmer a couple of weeks ago and went "Snap!").

 

I'm not convinced there's enough room at the bulkhead end to get the packaging to work. 76.5mm centers means about 1cm off center to deal with, and the od of the runners at 40mm is 2mm smaller than the runners I've used for plenums. The vac takeoffs were the original attraction - brake booster and MS made easier. The ladder design should make adapting easier than Suzuki alternatives.

 

But the price is awesomely cheap!

 

I've got a "back of the brain" adapter plate plan swirling - one that would allow a clip on cold air log similar to a PI one.

 

First problem is a manifold/runner/injector combo that allows the fuel rail to clear the bonnet (as always). I _think_ I may have come up with a better solution than my last couple of efforts. Just have to make it... (affordablly and repeatably)

 

C

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I was considering going with the Suzuki Hayabusa throttle bodies though they need an adapter to fit the Triumph Spitfire (photo).

 

Was working with a friend several years ago on machining the adapter from aluminum as a single piece. Got the exterior machined but my friend and the machinist got cross-ways on machining the tapered interior and work stopped (photo).

 

I may pick this up again as part of rebuilding a 1500 engine I have laying around. If/when I start this up again I'll be engaging with this forum for consultation and/or lessons learned (i.e. don't try this it didn't work out).

 

Kurt

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That is very nice - and eerily similar to what Chris and I sketched up yesterday evening.  Though I'll most likely be fabbing from mild steel using a hacksaw, angle grinder and selection of hammers.......  Will probably get the flanges laser-cut though because they are a BIG ball-ache to do by hand.

 

We were also contemplating a composite airbox including ram pipes.  Chris has good composite contacts...... with access to weapons grade (albeit out of date) carbon fibre stock.

 

Nick

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I'll follow this with interest!

When I said too small, I was basing that judgement on the cylinder capacity that each injector was spraying into.

Clearly that is the wrong criterion, and I need education:

 

Nick, I presume - probably wrongly - that your present single injector runs continuously?

 

zetecspit, " Mine are off a 1000cc bike, and are 42mm (tapered from 45ish) and are good for up to 220bhp on a 4 cylinder "  What tells you that?   When a Zetec is 1.6-2.0L  they will be inadequte on my false criterion.

 

Tryumph, Hyabusa kit would seem to be a good match (on my crits) to a Spitfire engine.  But the bores in the adaptors arer tiny!   Is this to be corrected?

 

Apart from cylinder capacity, what properties do you look for in an injector to match it to your engine?

John

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John,

 

At present, although I only have the one throttle body, there is an injector for each cylinder and this won't change.

 

Perhaps confusingly, the K1100 TBs I'm planning to use have no injector pocket as the injectors fit either directly into the head or into a rubber sleeve dependent on exact model.  Most bike TBs have the injector pockets built in and some even have two for staged injection.  You don't have to use them though.

 

Power output per cylinder is the most useful comparison for injector sizing.

 

Nick

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John, you are missing the point about sizing of TB's and injectors. 

 

A 1000cc bike will produce more power than your engine. And that is on 4 cylinders. So use TB's off a 1000cc bike and you will have way more than enough for your 6 cylinder.

 

My 2 litre zetec will be producing as much power as a well sorted TR6 (as in modified and about 175-185bhp) so use 6 of those injectors will be almost too big......

 

Time to do some research, look up injector sizing, and if you look at the Jenvey website there is a section on throttle body sizing.... size of engine they are attached to does not really matter too much, all about power/cylinder and a bit to do with rpm the power is made.

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So a little progress on this.
We made some manifold flanges.  I bought some tube.  Chris has cut and shut some lengths of tube to give a 35mm to 30mm (ID) taper over 140mm.

Today we've been messing about with layouts.  The modular nature of the K1100 setup allows easy addition of extras - if you have enough sets as each of the 4 TBs is unique - and even allows the throttle linkage to carry working as designed - though I need to remove some springs or I'll need both feet for the throttle!  However, the even 76mm spacing doesn't match especially well with the Triumph  55mm / 116mm spacing.  The other option is to split into pairs and extend the linkage between pairs.

The major issue looks like being bulkhead clearance.  No 6 TB sits right over the bulkhead (or even in it).  This is slightly worse with the paired layout as it moves back another 15 - 20mm.  The (huge) throttle pot is, naturally, attached to what ought to be No 6 TB, though it looks like it would be possible to flip the whole lot over so No 6 becomes  No1 - where it may clash with the bonnet instead.......  We've not tried it on the Vitesse yet as would need to to remove the existing manifold to do it (not hard).  We did try it on the GT6 where it actually sits just ahead of the bulkhead if the even spacing is used.

Progress is slow as it was a nippy 2ºC in the garage today.  Will make up a few more bits and tack up to try on the car.

P1160986s.jpg

P1160987s.jpg

 

Nick

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Looking good Nick. In between other things I have been working on inlet manifolds for the triumph tripple bodies I bought last year. Each set has a TPS on the end of the shaft, so I either need to remove one and link the shafts, not sure if it is possible to use both TPS, I guess not, but also there are two Idle air control valves, so Iwill probably remove one and permanently link the shafts as one. Removing one of TPS should make it possible to get equal spacing. 

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Some more progress.  Just tacked up so we can try it on the car and see what it interferes with. 

P1170040s.jpg

 

This is the version that keeps the standard 76mm BMW spacing all the way along.  Chosen because you can just slot the extra TBs in and the linkage works and it's more compact length-wise

It's all flat and parallel at present but I think there may be bulkhead issues meaning that we have to angle it all.  The compound angles will be a bit of a cow but it's doable.  The jig has been designed to cater for it if needed.

Nick

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Looks nice, but I fear for you packaging wise, both bulkhead and fuel rail wise.

If I had my time again, I’d package everything under the bonnet well before I did any finishing on it - it’s tighter than a fish’s arse under there.  The fuel rail alone is a bitch, better on the Mk3 than earlier though, and if you chuck the distance pieces to get room for the rail, the bulkhead jumps up and bites you (you may be able to relieve its lip, but i seriously doubt you’ll get the tps to fit at the bulkhead end.)

Angling the runners down will give you more options to get fuel injector bungs on a better angle to have the rail down low, and you _need_ to have the shortest injector you can find (think Opel 3.2 V6)

Packaging, packaging and packaging are the three watchwords when squeezing EFI under a GT6 hood

C

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The fuel rail will be ok - no change from how it is now.  Though perhaps not on a GT6 (no definite plans for injection on the GT6 at present).

The bulkhead though....... may be a different story!  May try it later on......

Nick

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Ah ha!  This is for the Skip?  Much more room then.

Surely you're going to inject the 6?

C.

 

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Yes, this one is for the Skip. The packaging issues are different - for  example, I have no idea where I'm going to put the air filter!

The plan with the GT6 is to build it more or less standard (CV shafts aside) and then run it for a bit to see how I get on with it.  Reasoning being that if I don't find I want to keep it, it'll likely sell easier and at a better price in standard form.

Being cautious partly because of the "bonding" issue I had with the PI and partly because I've barely driven a GT6 (I drove one about 5 miles 20 years ago) and, being of similar size and layout inside to a Spitfire, I find it a bit small.

If I do find it's a keeper then it may end up with the current Vitesse engine (with injection) and I'll build a 2.5 for the Vitesse to go with the 3.54:1 viscous lsd  R160 I have under my bench.....

Nick

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Remember this.......  Back on it - sort of.

We've actually got 6 TBs pretty much properly strung in a line so they work as BMW intended, but with 2 extras.

IMG_4541s.jpg

No, those trumpets won't survive - not at that length anyway - as in my quest to get the runners as long as possible (not least because it helps the angles) I haven't left as much room for the airbox as I should have....  It's possible (I hope), but very snug against the wheel tubs.

The question arises of which way to fit the TBs.  There are 4 possibilities.  Because these are simply butterfly valves with no injector pocket there is no obvious reason why they could not be used backwards.  As pictured above, they are backwards.  BMW use them with air entering from the top.  The whole lot can also be flipped over, moving the TPS from front to rear.

Considerations are:
As shown, the throttle cable approaches from the engine side (good)and the idle adjustment screws are easily reachable. The small (3mm) vacuum tapping however are not vacuum tappings anymore but rather useless under sized breathers, whereas the breathers (5mm, underneath) become vacuum ports.  TPS is at the front which helps bulkhead clearance and matches existing wiring.

Alternatively I stick with BMWs original flow direction and retain their vacuum ports.  The breathers are largely useless and I'd need to add a link pipe on the manifold to connect to my flying saucer PCV. This puts the TPS at the rear (maybe sharing space with the bulkhead) but I could flip it over endwise to solve that.  That puts the idle adjustment screw on the bottom where they won't be easy tp reach with the airbox on.  Which probably doesn't matter much.....

Need to try it on the car....

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