14 replies to this topic

[Andy.]

Hello ,coming to the end of the restoration of my sons 1980 mini 850.
Like all teenagers he wants the big exhaust ,which means big exhaust manifold and a water cooled inlet manifold which have been fitted and are ok,
but how do I plumb in the inlet manifold ?. At first I thought the pipe coming from the heater would be routed through it but if the heater is turned off would that stop the flow? any help would be appreciated . Thanks Andy

[SA MINI]

hi the heated manifold doesn't necessarily need connecting . on my 998 with stage 1 kit it runs better without the heated manifold

[Cooperman]

It's a water-heated (not water-cooled) manifold and you can simply by-pass it. It really serves no useful purpose and the cooler the mixture going in is the more power it will give. The water heated manifold is really only good in very cold climates.
With an 850 the largest exhaust you should fit is a 1.625" internal diameter. Any larger and some of the small amount of power an 850 has will be lost due to exhaust inefficiency. Even that size can be a bit too large at low to mid-range revs and high revs will be needed to make it work well.

Edited by Cooperman, 13 June 2012 - 09:24 PM.

[Spud_133]

I wonder if you'll get flamed for saying that there is no need for a heated manifold, Cooperman. Maybe it was because I'm younger means that I cannot know what I'm talking about?

[Cooperman]

I wonder if you'll get flamed for saying that there is no need for a heated manifold, Cooperman. Maybe it was because I'm younger means that I cannot know what I'm talking about?

???

[dow62]

Thought the same cooperman.

[Spud_133]

On another post I said there was no need for a heated manifold, but quickly got told I was wrong, so I will be waiting to see if the same people tell you that it is wrong.

[AVV IT]

As others have said, you don't actually need to connect it up, I ran my heated inlet without plumbing it in for many years. Then I decided to connect it up one day and whilst there was no noticeable change in performance, I did notice that the engine didn't take anywhere near as long to settle down and run smoothly on cold mornings once it was fitted.

So I'd say it's not actually a necessity, but it's still worth plumbing it in.

I can't really help with the plumbing on a 1980 model I'm afraid, as I've only ever plumbed one in on a later model where the heater inlet valve is at the bulkhead and the heater circuit take off is taken from a sandwich plate beneath the thermostat housing. This makes it much easier to take a separate feed off of the heater take off hose, before it enters the actual heater circuit itself.

I suppose you might be able to fit a sandwich plate beneath the thermostat housing on an earlier model, giving you a separate feed for the inlet manifolds plumbing and then also fit a later type bottom hose that includes the additional take off for a heated manifold outlet??

Edited by AVV IT, 13 June 2012 - 10:07 PM.

[tiger99]

A heated inlet manifold necessarily reduces engine power, but maybe not by very much, as at high revs the mixture will pass through so quickly that its temperature will not be raised very much. At idle it may be very significant. An engine produces power according to the mass, not volume, of the incoming air/fuel mixture, so if it is hot, and so less dense, the finite displaced volume of the inlet stroke can only suck in less mass of air/fuel, so there is less power.

Ideally you would have a thermostat that worked in the opposite way to the engine thermostat, cutting off the water supply once the engine was warm, when there is no need to heat the manifold.

[Cooperman]

Very few cars were/are fitted with heated manifolds. No Minis ever had them before about 1980-ish and they were not thought necessary for any of the real Coopers or Cooper 'S'. I've always by-passed them when I've used a manifold with water pipes and never had any issues.
I always think it was just one more rather odd thing that Austin/Rover did, like mixing brake connections imperial & metric, rubber mounting the front sub-frame to the detriment of handling, etc.

[tiger99]

Yes, that is true, and it will be useful at low engine speed, in a cold environment, but unfortunately when the engine is cold, the water will still be cold, and so will the manifold, so it gives no advantage at the most important time, which is cold starting. But maybe they did not need to pass an emissions test with the engine completely cold?

I have thought about this, and consider that the old-fashioned hot spot, where the inlet and exhaust manifold castings are joined, used to achieve the required result fairly quickly after engine start, but when the engine was working hard would be far too hot, and cause a significant power loss. The water temperature, being controlled by the thermostat, is more stable and predictable. Which leads me to my next thought, about how the manifold should be plumbed in to the cooling system. Ideally it wants to get as much hot water as is available quickly, before the thermostat opens. After that, when the engine is warm, it is not so important. So, its hot side should be fed from below the thermostat, the cold obviously returning to somewhere near the bottom of the system, e.g. T piece into the existing heater stub on the bottom hose. That may help answer the original question.

I had a Metro engine in one of my Minis, and I seem to recall that it had an outlet, maybe on a sandwich plate below the thermostat, which would seem to be the correct place for connecting the manifold heating system. I can't confirm that, as I don't have a Metro manual, and never saw the engine actually in a Metro.

My old Ford Focus TDi had an electric heating element in the water circuit, supposedly to get the demisters working quicker. Maybe adding one of these in the water feed to the manifold would gain some advantage on warm-up time?

[mini-luke]

I had a Metro engine in one of my Minis, and I seem to recall that it had an outlet, maybe on a sandwich plate below the thermostat, which would seem to be the correct place for connecting the manifold heating system. I can't confirm that, as I don't have a Metro manual, and never saw the engine actually in a Metro.

http://www.minispare...|Back to search

Like this? They're used in 90's on mini's for a heater take off and to eliminate the bypass hose.

[tiger99]

Yes, I was assuming that the choke would be used. It is not much fun trying to start without it. Unfortunately, it is often mis-managed by non-technical drivers. I hear that some dumb blondes pull it out so they can hang their handbags on it.

I thought my point was that when you use water heating you don't need a hot spot, perhaps that was not too obvious. If you have a modified exhaust system, with manifold fabricated from tube, you don't have the option anyway.

As for heated front screens, yes, they are the right thing to do, and I know that you can get then for Minis. I think that if you have one you will be MOT legal even if you strip out the heater. (Actually, not sure about whether the MOT would care, but you probably need a means of demisting to satisfy Construction and Use Regs, depending on the age of the car, and would definitely need one if it had to go for IVA.) My Focus had a heated front screen, and the heating element in the water feed, which when I think about it does not make a lot of sense, so I could have misunderstood, and the electric element was there to warm the passengers, not the windscreen (which it did not do particularly well).

At least we seem to be agreed about the OP's question, the manifold should be plumbed into the heating circuit. On a Mini, I would think that T pieces into both heater hoses would be the easiest thing to do for a retro-fit.

[Ethel]

Most Minis have a heated manifold because it's cast in one piece with the exhaust. I'd plumb it in, you'll get better mpg & running in winter. If it's in series with the heater valve, it won't heat if the heater is off.

[Andy.]

Thanks chaps, loads of information there ,I think I will leave it for now and may be look at it when the cold weather returns Andy