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Plenum Manifold To Throttle Bodies?


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9 hours ago, rogerguzzi said:

That sounds a good starting point but i still think you will need to tweek then when running!

I think you are right. There are separate air bypass screws for fine tuning at idle. Of course, having flipped the direction of operation, the vacuum ports provided by BMW to connect test gauges will no longer function for that purpose…… so going to probably need a flow meter, which look disappointingly pricey…. We’ll see. Maybe I can get a clockwork 600rpm idle by ear (not bleedin’ likely with 300deg cam!!)

 

6 hours ago, GT6MK3 said:

Nice work Nick.  I take it this is going in the Vitesse?

Thanks. Yes. Initially anyway. 
The possible sub-plot is that it looks as though I’m going to have to revisit the GT6 engine, and as I have a couple of 2.5 cranks lying on the garage floor…… it might be rude not to gain 500cc.

I also have an R160 diff in 3.54 viscous lsd flavour, one of Steve’s fitting kits   and an itch in my brain that thinks a mild(ish) tune 2.5 in the Vitesse with the original injection, in combination with this diff would produce a champion mile-eater.  This would mean that the yowling monster currently in the Vitesse would go to live in the GT6, which would mean injection and all that entails…. Putting the R160 in the GT6, in combination with the MX5 box means a ridiculously short propshaft and some unreasonable angles…..

No final decision made.  I don’t feel like spending lots of money on IC engines and mpg is going to matter….

 

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48 minutes ago, Escadrille Ecosse said:

That looks quite fabulous Nick.

Thanks. It’s going to look less pretty draped with the wholly necessary wiring harness….

 

9 minutes ago, rogerguzzi said:

Are you not having an air idle valve?

Ah. Well spotted. Again some options in play. The TBs have linkage for idle speed increase. Manual in this version but could possibly be operated by a PWM solenoid. That’s plan A. Plan B involves a T in my vacuum manifold and an extra air valve. Probably the thermoelectric one I’ve been using.

For now, I’m curious how big an issue this is. It warms up very fast…..

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Well, some way from finished but it runs.
 

DFBAF33E-42E2-492E-AE7B-DD5F73ED2441.jpeg

Surprisingly well considering all I’ve done is changed the fuel value due to bigger injectors (not needed, what I had) and set the throttle pot.

It’ll idle flat at sub 500rpm and the noise is completely altered at both ends (was expecting the front to sound different). Sounds proper fierce at the front end.

It’s very rich as the MAP is offset upwards. I’ve not attempted to drive it as no air filters, dark, raining and Tuner Studio wasn’t playing ball. But I reckon it would drive.

I do have video evidence, but it’s on my iPhone and thus hard to transfer to my PC….. Maybe I can get it to YouTube direct…

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Blimey you were not hanging about with getting that to the pointy end. Impressive. 

And superb result too for straight out the box. 

I was curious about how you would get on with starting idle as I also suspected you might get away without idle air valve and rely on ignition timing to keep the thing alive while warming up.

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21 minutes ago, Escadrille Ecosse said:

rely on ignition timing to keep the thing alive while warming up.

Interesting you should say that. Current firmware doesn’t have that ability, but as it looks like the very aged firmware is what is upsetting Tuner Studio (dunno why, it’s been fine for years), maybe I have to bite the bullet and upgrade. Then I will have that facility. Bit reluctant as it’s been completely stable and bug-free, which is more than could be said for the much later, more feature-rich version I used with the PI.

Need to crack on and get it to a driveable state as I’m very curious to discover if it’s worth the effort!

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13 minutes ago, GT6MK3 said:

Is that a TPS hung on the front end?

Yep, TPS at the front. On a GT6 I think it could be at the rear (as BMW intended) as there’s more bulkhead clearance. As it is, I’m going to have to turn the bulkhead lip on the Vitesse to miss the airbox as apparently I can’t read a ruler….. it misses, but only by a fag paper.

As regards GT6 fitting, it is all pretty low. Lower, and further back, than my single TB set-up. Front of the fuel rail would be the potential contact point. I’ve laid the injectors back further this time (35 deg) which helps a little. Still using EV6, full-length injectors. Could go shorter without major difficulty. Whether that is enough to miss a GT6 Mk3 bonnet…. I’m not sure.  There would be various other hurdles to jump when injecting the GT too.

 

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There's some stuff in my GT6 thread that might be worth digging up if you do.  Particularly the 0280156080 injectors from the 3.2L Vauxhall Vectra, that gave me the smidgeon of clearance I needed, while still being EV6 and (resonably) lowish flow.

I'm not sure my GT6 will have the bulkhead clearance - I seem to remember when I made the plenum's for it and the 6fire the bulkhead clearance was awfully tight.  Found lots of room at the front with angled pipes.

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Yes, will look back at your thread(s), as you are the expert on this!

Was it the round tail you really struggled with with its smaller bonnet bulge? Or both?

I could physically try it on the GT6 when I start pulling that apart. It’ll come off the Vitesse in minutes, it’s the carbs that are awkward.

 

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  • 2 weeks later...

Been working on the airbox….
As mentioned, clearance stuff the rear was minimal 

1F2FE694-0F75-4052-8C20-0F938C81B6B0.jpeg

So got the hammer out again
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The bulkhead got a minor massage too.

Then hammer forming the box part
496C0D26-0AAB-4DFE-B1B3-4A38F1352AB2.jpeg

Couldn’t manage the full depth of the curve, so let a bit in

6EF3DF1C-8CCA-418B-A0B2-2B647B736026.jpeg

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It too had to have a flat in it to miss the clutch gubbins
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Sort-of fits the backplate….. I'll stich them together and seal with PU sealant when I've figured out the front end

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Front end was a bit of a challenge. How to blend a tube to a rectangle with just the right amount of tip down and in.

Not least because the Royal Mail camel got sick and I had to use a “stunt double” air filter for the design process...... It's a strut gaiter for a C4 A6.
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tacked….

Then I remembered I needed a new heat shield

76F78AED-DACB-45C9-96CF-1F84592C5777.jpeg 


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Stub welded in before permanently uniting the two parts

F428C80E-6514-4441-B504-31B52DAE28F8.jpeg

As of this afternoon it’s “finished”, apart from PU sealant around the majority of the joint and some paint. That might have to wait. It’s not got above 3ºC in the garage and I had to resort to the hot air gun to dry the etch primer!

AE7B0A61-6122-46FF-8431-F2F7FC86ECD2.jpeg

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Nearly time to go mapping - except they’ve been dumping salt on the roads…..

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last pic shows the inlet air temperature sensor. It’s a bit snug…

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Nick,

Just been perusing this thread again, you said at the start you bought 3 sets of bodies. Also you mention later that each body is individual, but can be joined to extend.

What I can't quite make out, do you need three sets of bodies to make up a 6 pot set? Or could you do it with two sets on the basis of one each of the end bodies, plus four in the middle?

Muchos gracias!!

Phil

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You can do it with two complete sets Phil. At least you can with the K1100 ones. There are several model variants that look similar but have detail differences.

I had 3 sets because one purchase was a job lot containing a full set and a part set that was in fact a full set apart from no throttle pot and one link arm missing. In fact there is a full set left that Chris has blagged for….. something…. 
 

You couldn’t make 2 sets of six from three sets of 4. Not easily anyway.

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