EFI Testing - Dyno Day 6: 1.5:1 Ratio rockers
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But from your radius of 2.38978", that would mean to move the cam 10 deg would require somewhere around 10.6mm of movement on the circumference.

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I took a slightly different approach.

I did the maths first to see how far a longer chain (ie, two extra links) would need to be pulled out to the side (one side only) to tension it back up.
That is assuming the sprockets are dot to dot (standard timing) even though they ar not dot to dot in my photo.

That maths gave 1.4" sideways movement as per the second photo in my sequence.

I then reasoned that if you then drag the slack across to the other side with one of the sprockets held stationary it will rotate the other sprocket by two teeth.

In other words, the maximum difference you can achieve by taking the slack (or tension) completely from one side to the other is a two teeth rotation which is either 2/20th * 360degrees or 2/40th * 360 degrees.

That's where my notes started to get a bit scrappy (I wasn't being very methodical about this) and I got sidetracked by worrying about how big a tensiorer (let's say a roller) would actually fit behind the chain to push it out anyway so started printing out scaled copies of the original photos and drawing on them.

From this I deduced that if you start with the chain pulled/pushed out equally both sides (0.7" each side), how do you then calculate what happens if you take one side out a bit and let the other side in a bit to achieve 5 degrees relative rotation (push one side out for +5 degrees, other side out for -5 degrees.

From a combination of poor maths and drawing I got just under +/- 1/4" (or just under 1/2" overall which is similar to your 10mm).

By this stage I was still not convinced my maths or drawings were actually correct and whether it will be physically possible to get some suitable mechanism(s) inside the chain loops without hitting the sprockets themselves so decide the best way would be to mock it up for real hence searching the web for, and ordering, some cheap chain.

Just one point of clarification - when you say 10 degrees, do you mean 10 degrees at the cam itself or 10 degrees static timing difference ??

As in the "normal" way I time the cam in (using offset keys on the Mini and Vernier cam wheels on the Cossie) is with the 360 degree graduated wheel on the crankshaft, and set the crank to whatever (say 108 degrees), then rotate the cam for maximum valve lift (with a DTI) and fix it at that point. But what ever figure is chosen using that method, if say I had set it spot on at 108 I wanted to change it to 106 just by swapping the offset key for one 2 degrees "smaller", it would only change the relative position of the camshaft by one degree.

So is it 10 degrees we want at the cam or at the crank ??

TBH I've lost track (and my notes and sketches aren't clear enough) which I was working against. I think it was the cam but rather than try to go through through the maths/drawings all again, I'll wait for the chain to arrive.

A second reason for wondering is that most of the hydraulic wheel types appear to have a lot more movement available (which means an awful lot at the crank) but that may well be down to the benefits of changing inlet and exhaust timing separately.

Schrödinger's cat - so which one am I ???

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Siamese 5 port EFI testing
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Briefly back to the Variable length inlet runners


I spent all day yesterday fitting up, jigging and welding the new runner pieces.

One of the issues I have is height, the existing plenum rubs the bonnet slightly, and with the angle I had made the flanges on the curved part of the runner, this meant that the plenum would be even higher, around 15mm by eye I think.



Not a lot of good.

Hence I had to angle the new top runner piece down somewhat.

Amazingly I managed to weld it all up without any major drama. There is a little warpage on the thinner flanges of the bottom extension pieces, but enough to be worried about.











But… That’s where the positivity ends!






Fitting in the car.


Yep, I screwed up.

I have my 5mm clearance to the bulk head on the bottom of the curved section, which is good. I can tilt the engine forward marginally to increase that if necessary.

But, Rocker cover…

Basically, it’s in the way.








ARRRRrrrsssse!!!!!


I’m just heading over to my Dad’s workshop to steal a standard tin rocker cover off one of the spare engines, so that I can see whether that allows enough clearance, and to make sure that the 1.5:1 rockers have room.
Failing that, I will need to reduce the extending length of the runners by around 25mm, and I’m not yet sure how that will affect my figures.


Grrrrrr.

’77 Clubman build thread
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Siamese 5 port EFI testing
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This whole project is mind blowing! Great work, Gra!

OK,

Even though I said I'd wait for the chain to arrive, I've re-done my maths but working backwards and, without resorting to drawing it out again, I get the following (pretty much as before but I'm happier with the way I did it).

Add two links to the chain and it requires deflecting (or tensioning) out to each side by ~0.7"

(Imperial is not my native language but it's safer as the chain and wheels are imperial).

To achieve a 10 degree swing (ie, +/- 5) on the "static" (ie, crank) timing requires the chain to swing between 0.5" and 0.9" extension, equal and opposite, on either side.

To tension/guide it, there is not enough length available on the inner face - the standard tensioner has a much greater length available on the outside.

A simple roller wouldn't work because the links are flat so would need a very large roller (like the normal slider) for constant velocity and there is no point in persueing this if the chain speed is going to be varying (in a horrible oscillating way).

However, there are actually duplex sprockets available - much to my surprise - with as little as eight teeth.

None of the catalogues give me the actual dimensions but using my trusty "any dimension you might ever want to know on a polygon" calculator I get a radius to the pin centre of 0.489961", so a diameter of ~1"
Obviously the tooth peak diameter will be larger but I see absolutely no reason why, just like on the tensioner of the de-raillier on your pushbike, the teeth can't be machined down to flat top, ie to the pin centre diameter, or 1" overall.

With a quick mock-up in the garage just using a bit of 1" round bar, that gives the required travel with approx 0.1" clearance before the tensioner sprockets would hit the main sprockets.

I'm beginning to think this is do-able without the complication of the hydraulic VVT pulley type things.

A pair of 8 tooth sprockets now on order.....

Schrödinger's cat - so which one am I ???

Blimey - nice work Rod.

’77 Clubman build thread
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Siamese 5 port EFI testing
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Disaster averted – I hope…






It is still a bit close and I will work out if I can reduce the overall extension length slightly, but that’s around a 9mm mm gap, so it should be enough, though not as much as I was hoping.



I also have to consider the flow of air into the runner mouths when it is fully extended, so the extensions might have to go shorter anyway.

Of course, this means a load of messing with the rocker cover to remove the filler neck and make a new filler off to the side like the Aluminium rocker cover had. But that’s not critical at this point because it will be a while before this setup gets onto the car proper so I can just lop off the filler neck for now and finish it off later.


So, now onto what I should have been doing today. Hacking my molding of the Plenum to get it to fit.

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Siamese 5 port EFI testing
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Well, the chain, links and sprockets arrived.

But as soon as I laid it out next to the standard chain to mark it for cutting I realised there was a classic cock-up in my maths....

I had calculated that adding two extra links should give me 1.4" deflection total, ie, 0.7" either side.
I don't know where I went wrong but it's actually 1.4" each side......

So, instead of an "ordinary" chain with an even number of links and a standard joiner I need one of these to create an odd number.


I don't really like them but it's the only way.

However, I was going to try out 4 extra links so with just two I get what I was expecting to have to use four for...





That's the basic principle.
Even without (yet) machining the tops of the idler teeth there is more room inbetween the main sprockets than I envisaged.
As pictured at the moment, it would give way more than 10 degrees but would require a significant enlargement of the backing plate and cover so I'll see how it looks (and make sure it will get 10 degrees) once the new link(s) arrive.
The other reason I don't like the above, provided the original idea can be made to work as I intended with the alternate link, is that is wrapping the chain almost 1/4 the way around either of the idler sprockets which - although valid because the rollers are supported in the valleys of the teeth - means each roller rotates a lot more than normal as it passes over the idler so I suspect the wear rate will be a lot higher than normal.
In the Renolds design manual (yes, there is one...) it recommends any idler sprocket should be at least as large as the smallest driven/drive sprocket so I'm way outside their recommendation anyway.

EDIT - typo

Edited by Rod S on 31st Jul, 2019.

Schrödinger's cat - so which one am I ???

That looks like it will be a lot of movement to get a reasonable change in timing.

And a lot of work with enlarging the backing plate and chain cover.

I was expecting around half of that deflection.

It will be interesting to see see what the new chain link gives.

’77 Clubman build thread
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Siamese 5 port EFI testing
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The photos are deceptive because I didn't fix the big wheel in position and it moved as well as the little one when I re-positioned the chain (just for the photoshoot).

From measurements the relative movement is about 22 degrees, maybe slightly more.
So that should equate to 11 or more with the replacement cranked link. Then a bit more still with the idler teeth machined down to centre roller pin height.

In other words I do still expect it to be half that deflection (or less) for 10 degrees.

I don't know how soon the new bits will be here but I'll build a proper static jig in anticipation.
Next thoughts are on a mechanism to operate it, starting with bearings for the idlers.
The pilot hole in the sprocket is 6mm and the boss (un-seen in the photo) is 15mm so I'm thinking of boring to 10mm and fitting a sintered bronze bush for a 6mm pin.
6mm bore bush and pin is already very close to the maximum allowable speed for a bronze bush.

The bushes have three ratings; surface speed (V), pressure loading (P), and P*V.
It doesn't help that the only datasheets I can find are imperial and although I can calculate speed I don't know what pressure is going to be required to keep everything in place so can only work backwards to what is the maximum pressure I can apply.

Because they are only 6 teeth they will run at 20/6 crankshaft speed. Keeping the pins down to 6mm is essential to keep the surface speed below its limit - 6,500 RPM crank speed is 16,250 RPM at the idler which, on a 6mm pin gives 1,063 ft/min against a max allowable of 1,200. By using the full height (length) of the sprocket for the bush maximises the surface area available for the load but calculating backwards allows me only 11 lb load (force) at maximum speed to avoid exceeding the P*V limit (at maximum RPM).
In proper units that's ~5Kg or 49Nm.
So a bit of experimentation is required to see if that's enough.

Best I can think of at the moment is try to find a spare standard tensioner (the spring blade type) and see how many bags of sugar I have to put on top of it to flatten it.......

EDIT - sentence added for clarity.

Edited by Rod S on 1st Aug, 2019.

Schrödinger's cat - so which one am I ???

I love how TM are still helping to push the boundaries.

Interested in your plenum design, interested in making one myself, How many layers of Carbon did you use, and what's you max boost? How may layers do you think would be required for 30psi?

Team www.sheepspeed.com Racing

Jim, as yet I have not made a Carbon fibre Plenum.

The current plenum in service (X7) is made from welded 1.2mm sheet aluminium and a few bits of aluminium tube.
It finally blew out during Februaries Dyno session at we think around 18PSI – it tore on the welded seem.
I have repaired it with 2 layers of 2/2 twill 3k 200g, wrapped around the outside like a bandage. So far it has seen 18PSI on the road.


I have made a few moulds of the original manifold and was working on smoothing out the corners to make the laying up process easier.

I say was, because now that is all out the window with the Extending runners. I need to change the shape of the plenum slightly, which I am current working on by hacking up one of the failed pieces I previously made.


I got this far with the X7 plenum mould…












…before now working on the changes I need to make to suit the runners.

Also, spot the mistake – This mould would make a nice outer surface finish, but there would be a lot of work to get the inner surface smooth and consistent.
Another reason for dropping it and concentrating on the new shape.






My overall plan though is to make a plug mould (I think that's right??) so the inner surfaces are the correct size with a good finish.
Layup the mould halves with 1 layer of 200g material, followed by a couple of 450g layers.
Then break it out of the mould and glue the 2 halves together.

I can then “skin” the outer full shell with as few layers as possible of 200g and or 450g to strength the whole thing and get a reasonable finish.



I have no idea how many overall layers would be needed, but some research on the internet a fair while ago suggested a plenum would need a thickness of around 1.5 – 2mm of carbon fibre for a boosted application, though it did not say to what boost level, so I am aiming for around 2.5mm total – but then, I am limiting myself to 21PSI due to the MAP sensors I have installed…

or 30PSI if I get the MAP sensors upgrade…



Apparently one layer of 200g adds ~0.2mm thickness, 450g adds ~0.45mm.

Edited by Graham T on 1st Aug, 2019.

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=611675

may need a 3rd clutch spring for 30 psi graham

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

On 1st Aug, 2019 robert said:
may need a 3rd clutch spring for 30 psi graham

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Siamese 5 port EFI testing
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i'll drive ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

That would be Nappie AND Waders - I have read the stories...

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
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Thanks for the info Graham,

I've thought about 3d printing a plenum, to use a plug, then dissolve and hack out the 3d printed plug afterwards.

Team www.sheepspeed.com Racing

I made a mould for my carbon plenum using a big block of modelling foam and sanding it to shape. The foam is easily dissolved using thinners.

Phil.

WWW.TURBO-MINI.COM

Schrödinger's cat - so which one am I ???

Edited by Graham T on 4th Aug, 2019.

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=611675

Just a small offering on the Plenum mould side.
A long way to go still, but the basic shape is there.

I have Just got to fill the gaps and stiffen it all up, then reshape the top section, paint and polish.

Just…











Then I can make a cast which can go on the flow bench.

I can hold the two halves together with duct tape (which will also seal it) for testing, that way if changes in the shape are needed, we can get inside easily and use plastercine to change the shape. I can then append those changes to the plug.
All sounds so simple.

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=611675

On 2nd Aug, 2019 Tom Fenton said:

On 1st Aug, 2019 robert said:
i'll drive ?

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=611675

On 4th Aug, 2019 Graham T said:

On 2nd Aug, 2019 Tom Fenton said:

On 1st Aug, 2019 robert said:
i'll drive ?

By the way, I have complete trust in Roberts Driving.

where are we at now? 52 Runs on the Dyno and apart from that unfortunate incident in Feb, all is good.
Just as long as the car is strapped down with 2 """racket straps""""" I'm totally comfortable being passenger to him!

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM