7 replies to this topic

[dubmeup]

I`m just about to plumb in the heated inlet manifold on my partners mini. I have a few considerations in mind, such as If you plumb it in series with it then flowing to the heater matrix, will the heater valve pull also then turn the flow to the manifold off?
Series makes sense to get the most reliable flow, but would you then still need to have the heater pull open in summer?
I`m sure there are many more considerations, and had a bit of a hunt around on the forum,,, many different opinions out there lol,,, this has led me to settle on plumbing it in and doing it in series when i do. Any chance of a definitive topic on the subject???
Cheers and keep up the good work.

[AndyR]

Hi there

This is just a suggestion that you may want to consider, I may be wrong!! I’m sure you will know that your car runs best with crisp cold dense air entering the inlet manifold - that’s why your mini will run better on dry winter mornings. Therefore by running the coolant through the inlet manifold it will only warm up the air and decrease performance. The loss in performance may only be fractional but every little helps!!!

Good luck

[Grayedout]

The heated manifold is there to prevent carb icing in the winter and at this time of year you will have the heater on hot anyway so the flow will be there ! So yes plumb it into the heater circuit !!!

[panelbeaterpeter]

Here's how I've just done mine, I used a metro thermostat housing sandwich plate with outlet, took a feed off that, through some B&Q 22ml plumbing pipe and then through the inlet up towards the heater tap. It works perfectly.

Pete.

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[Dan]

It should be plumbed in to work all the time ideally. Yes there will be a very minor change in the charge density over cold clean air but by keeping the manifold at a constant temperature you stabilise the tuning. By turning the manifold heating on and off all the time you very much alter the tune of the engine and will affect the reliability of it. It doesn't prevent the carb itself icing as the body of the carb should be isolated from the manifold but then what people describe as carb icing very rarely is actually the carb. It is normally the fuel condensing out of the charge and forming droplets on the cold manifold walls (which it is more inclined to do if you polish the manifold) and heating these walls prevents this. It can even happen in summer too.

AndyR's point is commonly thought to be a good idea but the people who design these manifolds knew what they are doing and just assuming you know more than they did is a bit arrogant! As you say the loss in performance from heating the manifold is fractional but the loss in performance from the engine tune changing with the outside air temperature is far greater. The engine can't compensate very well for the charge density changing (the carb can adjust a certain amount if a Waxstat jet is fitted or if it is an HIF but not much) so letting the air through at whatever temperature it happens to be alters the tuning. This is also why there is a heated intake in the air box. Injection cars can adjust for air density and the SPi still has a heated manifold because it is a very long manifold which fuel flows all the way through so it can still condense out. The only reason there is no coolant in the standard manifold is that it is connected to the exhaust manifold which heats it.

I assume you have the early heater valve setup fitted directly to the head. If you replace this with the later system the valve is remotely fitted and the head has just a pipe stub fitted. Using these you can direct coolant through the manifold seperately from the heater. To the head outlet fit a t-piece and then run one leg to the manifold and one to the heater valve and heater. Then join them back together at the bottom hose. The late system uses 5/8" hose rather than the 1/2" of the early system so you will need some new hose and adaptors.

[dubmeup]

Thanks for the input folks.
The merits and demerits of plumbing the manifold in seem to have been discussed at length in other topics. My intention in starting this one was to get some light shed on the plumbing details once you`ve wisely decided to go through with it.
With that in mind, cheers for the photo Pete. Looking at it raises a question in my mind. If you take your feed from the thermostat, doesn`t that mean that you`ll only be getting flow when the engine is up to full running temperature? Ie, the thermostat would have to be open. Wouldn`t that reduce some of the benefits on cold mornings?
Dan, thanks for your post. Your system would be in parallel wouldn`t it? I may be wrong but as i understand it, when the heater circuit is open, that means that the water has to make a choice which path to take and it will tend to favour the path of least resistance. I guess this would usually be the manifold as it`s essentially just an open pipe whereas the heater matrix has inherent resistance to flow. That would have to be a good thing with regard to heating your manifold but not neccesarily your toes on a cold morning! That`s initially why i thought a series plumb would be better. You could guarantee a good flow to both manifold and matrix. However, to my mind, series does give you the problem i alluded to in my initial post of having to have the heater circuit open at all times of year, just to get flow through the manifold. I`m now thinking that if you were to use the pipe stub outlet that you mentioned, you might be able to take your feed in series from there, through the manifold and on to a bypass valve which could direct water either through the heater matrix or down a bypass hose . If you could get manual control of that valve sorted you`d then have permanent flow through the manifold and also the ability to turn the heater off in summer! I`m not sure how to achieve that control yet but ideally it would use the existing pull on the dash. Got any thoughts? Anyone else been down this route?
Cheers all, Paul

[Dan]

I think you might be thinking about this a bit too much. Do you appreciate how much flow there is in the coolant circuit? It runs at almost 15 psi (1 bar-ish) and flows incredibly fast, the pump turns at roughly the same speed as the engine remember. There's far more flow and pressure than in most domestic heating systems, even with a 1/2" pipe open through the manifold there is still more than enough flow and pressure to push loads of hot water through the matrix. All single point injection Minis and late carb models have heated manifolds running in parallel to the heater matrix and they work just fine, in fact later heaters are a lot better than earlier ones because they have more water flowing to them through the thicker bore pipe work and an aluminium core. All you are doing if you do run them both together is updating your coolant layout to be equivalent to that which Rover found to be most effective in later cars. The only difference is that they take the flow from under the thermostat through a sandwich plate. If you are really worried you could get a sandwich plate to use and leave the heater output supplying just the heater while setting up the sandwich plate to give bypass and manifold heating combined.

Edited by Dan, 17 April 2007 - 03:46 PM.

[dubmeup]

Cheers Dan, you may well be right that i`m thinking about it too much! It`s not the first time someone`s said it. I`ll bow to your judgement. Would i be right in thinking that the outlet from the sandwich plate is taken before and therefore independent of the thermostat? If so then my questions to Pete regarding cold mornings would be irrelevant.
Paul