It's my Reno 12

Tell us your ongoing tales and experiences with your French car here. Post pictures of your car here as well.

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bowie
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Re: It's my Reno 12

Post by bowie »

MP1435B50 (1).jpg
Like this?
Dormouse
Donor 2021
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Re: It's my Reno 12

Post by Dormouse »

no. can't find a photo so will draw it instead.
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Paul-R
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Re: It's my Reno 12

Post by Paul-R »

Dormouse wrote:
08 Jun 2021, 13:07
Have you ever seen a Stacked 4 into 1 where all 4 pipes go into a large fishtail type box inline?
Such as these for a Lotus headed Vauxhall 2300 Twin Cam? Sadly without the collector box.
IMG_20180715_164154474a.jpg
Inspired by these I made a set of four-into-one manifold pipes for an Alfa Romeo 1300 twin cam some 45 years ago. No photo I'm afraid but they're still around somewhere.
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bowie
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Re: It's my Reno 12

Post by bowie »

I think your describing something akin to most motorcycle manifolds?
images.jpeg
Cool.
Dormouse
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Re: It's my Reno 12

Post by Dormouse »

Try this and see if it might work.
1623160969829.jpg
The 4 pipes arrive at a collector box vertically in line ( or whatever angle to suit space available). Notice how the furthest away pipe goes straight to the chamber. The next one goes over the first pipe giving you a chance to get a matched length.
The third one goes over the first two giving you a chance to get a matched length.
The fourth one goes over the first three giving you a chance to get a matched length.
Pipe 1 is a tuned length and bore. Pipe 2 should be curved to fit and be the same length and bore. Pipe 3 should be curved back and forth more to give the same length and bore. Ditto pipe 4.
For a 4 stroke, 4 cyl engine the cross sectional area of the outlet pipe should be twice the area of the primary pipe to maintain gas flow speed ( like the 35.5 and 50 mm pipes in the photo you sent). They need to be calculated for your exact engine requirements. Normally you use the nearest diameter of standard pipe available unless you can seriously afford custom sized pipework.
The Chamber can be very short a la "square" 4 into 1 in the photos you have put up or you can take the opportunity to match the chamber volume/length as in 2 stroke exhaust technology. The fishtail could also curve and the outlet does not need to be in the same plane as the primaries/block side. What is important is to maintain tuned pulse lengths/volumes and gas flow speeds. Ideally the total length of the exhaust to the very end should be calculated to finish to aid pulse return waves.
I hope this makes a bit of sense. And, yes, it is a science in it's own. Good muffler/exhaust designer is a very clever person.
Dormouse
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Re: It's my Reno 12

Post by Dormouse »

bowie wrote:
08 Jun 2021, 14:27
Image

Like this?
In this picture pipe 2 and 3 are obviously different lengths and ideally 3 should terminate where 2 goes into the 4 into 1 collector (and 2 for 3) to get equal tuned lengths and 1 and 4 should be shaped to match the tuned length if this was a perfectly designed manifold. Problem then would be space to get all the extra curves in. This one is the best, simplest manifold design that fits the Alpine without fouling issues but is slightly compromised in designed tuned length primaries.
Dormouse
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Re: It's my Reno 12

Post by Dormouse »

bowie wrote:
08 Jun 2021, 15:27
I think your describing something akin to most motorcycle manifolds?

Image

Cool.
Yes, sort of. This manifold is actually a 4 -2 -1. Look carefully and you will spot two "Y"s in the first part of the collector then into another "Y"
Dormouse
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Re: It's my Reno 12

Post by Dormouse »

And without being too picky, the collector looks like it is struggling to provide tuned lengths and gas flow speeds although it is the right kind of basic design. Time to pull my neck in now and put my tin hat on.
Dormouse
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Re: It's my Reno 12

Post by Dormouse »

Love the way your 12 cocks it's inside rear wheel ready to P*** on anyone brave enough to dive up the inside. Takes a fair bit of bottle to maintain that stature through a bend. Weight transfer to the front outside suspension is very high.
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bowie
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Re: It's my Reno 12

Post by bowie »

Ahhhhh I'm with ya now. Thanks for explaining that fish tail example above. Yes I will be working toward equal length primary's, and that's an interesting packaging example, particularly with the capacity for the collector to be curved with an outlet being offset. With the engine being backwards in my 12, the collector could nearly start at the front

Yes I have a few books to read before I put pen to paper... ah but we know I'm going to jump right in then try to correct a mess I've made for myself :D

The second best thing I did to the 12 (after putting wider wheels on it) was to install thick sway bars, I think I ended up with a 28mm rear and a 22mm front (vs 14 rear and 17 front), chucking it around is great fun.

I keep tyre pressures pretty low and it understeers when pushed, but getting off the go peddle it still has it turn in and tightens up, nearly to much oversteer which is fun.
Dormouse
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Re: It's my Reno 12

Post by Dormouse »

You certainly seem to understand the magnitude of what you are doing. Does the 12 snap into oversteer when you lift off abruptly or does it sort of shuffle into oversteer?
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bowie
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Re: It's my Reno 12

Post by bowie »

No never got snap oversteer with it, then again I never go off the power completely mid corner either to be fair. Don't know if I'd consider it fast enough to qualify as "snap" either to be honest :P

It will start to turn over on itself when you reduce the power mid corner, but it was never violent. I was using Yokohama's AO48's (second hand from some formula ford teams) and I suppose they helped.
Dormouse
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Re: It's my Reno 12

Post by Dormouse »

yes. I was just trying to find out if your front suspension compliance bushes were giving you a vague feel or not. Have you ever considered doing corner weight compensation?
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bowie
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Re: It's my Reno 12

Post by bowie »

There's a few other little things I'll need to do before I get that detailed.

I want to Heim joint the silly thing and I need to decide what to do about camber. (Camber is fixed front and rear)

Ah one project at a time. :S

You did remind me of something a little urgent however. I got around to installing some vented disc (had to change the hubs and carrier) and whilst there I replaced the lower control arm, fresh bushes. The replacement bushes are no good however, they are two piece and fall out of the control arm as compared to the OEM single piece and pressed into the arm. Anyway...

I have heaps to do.

My welder hasn't arrived yet, might start of with good old regular maintenance.
Dormouse
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Re: It's my Reno 12

Post by Dormouse »

I have been looking at the front suspension funnily enough and the positive camber is very pronounced. will do a bit of searching to see if any bits can be interchanged. cheers