intake manifold cooling

intake manifold cooling

Here is my question,
how many of you folks out there running aftermarket downdraft webbers, use the intake manifold cooling arrangement?

if so, why?
if not, why?


mark

Re: intake manifold cooling

Mark,
I notice no responses.
I personally have no idea what you are talking about. Can you give some details? Maybe I can help or someone who knows will jump in. Usually a Big Healey pic in foreign territory will get something going.
D

Re: intake manifold cooling

Mark,
If you are talking about an intake manifold with a tube running through it from the rear to the front, it is a 'heating' not "cooling" arrangement. That tube is for the heater return line and will heat the air-gas mixture in the manifold.

Re: intake manifold cooling

Biff

Are you sure about that? I know that's the popular thinking, but with the water running through the intake the temperature of the intake manifold should not exceed 190F give or take. Without the water running through the manifold and considering the intake is practically surrounded by the exhaust manifold, what temperature does it reach???

I haven't measured, but I suspect it is even hotter, especially if the car is sitting.

Has anyone checked this on a dyno or, at least, pointed a thermometer down the intake to confirm or deny this "urban legend"?

Re: intake manifold cooling

bout Time Fellas, The Big Healy pic is here...lol

I consider it a cooling system. But i am sure it helps with quicker warm ups. the stock zenith setup had it as well as a heat shield. The webber conversion manifold has it (or is at least set up for it) as well. I guess i just wonder if it is needed or not? Keeping the fuel mix at temp has got to be better than letting it got to hot. It does sit right on top of the header.

i was just wondering if all the weber fellas out there used it or not. I do.

thanks Dave for bringing this back.. /ubbthreads/images/graemlins/smile.gif

mark

Re: intake manifold cooling

My Weber uses it but I have never tried to run without it. But I was going to look into using a heat wrap or maybe a ceramic coating on the header to help with the heat. Then eliminate the cooling line and possibly reduce the intake temp.

Re: intake manifold cooling

anyone thought of fabbing up a intake box and feeding it from the front of the car?


mark

Re: intake manifold cooling

Mark,

A cold air intake plus removing the manifold heat source would give more power & possibly less drivability under certain cold conditions. The latent heat of fuel vaporization plus the intake air flow does a surprisingly good job of manifold cooling. This is a pretty good deal, because at low speed low fuel/air flow, there is less cooling & at high power, where you want it, there is much more fuel/air flow, vaporization & cooling.

I once put thermocouples in the intake ports to measure this cooling. (Unheated manifold) This WAS a turbocharged engine which had additional charge cooling which was bypassed for this test. This engine also used a 50 HP charge of nitrous oxide plus fuel to get the turbo spooled up faster, but that is another story. This was also disabled for the tests.
The results for this particular engine on which the ports were at 210F at idle & low speeds:
There was a 60 degree drop at cruise & a 150 degree drop at full power. This intake charge cooling effect would be less with a heated manifold, depending upon how much the manifold was heated.

Since air density increases by about 2% for each 10F drop of temperature, you can see where gains can be made by using a cold manifold & ambient air intake vs the very hot under hood air intake. You would probably have to richen jetting some to make up for the increased air density.

If you may be driving in cold temps part of the time, perhaps the best situation would be to put a shutoff valve on the water heat/cool manifold connection & use an air intake located in a cooler position.
D

Re: intake manifold cooling

Was the engine for these tests an "F" head like our Austins? Or, was the inlet and exhaust on different sides of the engine?

Re: intake manifold cooling

Opposite sides, but the very hot turbo compressor was on the intake side. As was the exhaust feed to the compressor.
D

Re: intake manifold cooling

WOW! ... I was just thinking about thsiexact topic yesterday ... and now I find a post for it!

yesterday, when I parked my 78 midget in the garage after a 40 minute highway run, I heard a distinct hiss from the engine compartment. Upon investigating I discoverec a small leak in the rubber hose running from the thermostat housing (maybe the water pump) in to the front side of the intake manifold. I'd never noticed it specifically before, and as I got to looking, it appeared to circulate thru the manifold to a similar rubber hose coming out the rear end of the manifold into the manual heater control valve.

I obviously have to replace the leaky hose. Buti I can't tell from the way you guys described it ... which way is it flowing? and is it supposed to be heating the fuel/air mixture? or cooling it? and for what purpose? ... I'm confused.

Please be patient with me as I just bought my first midget in April (wanted one for 25 years!) and am just learning of the intracacies. learn me ... thanks /ubbthreads/images/graemlins/driving.gif

Re: intake manifold cooling

Welcome aboard!! we have plenty of patience here.

whether it is heating or cooling , i am not totally sure, but my gut says cooling. not sure quite why this arrangement is used , maybe to keep temp levels steady? certianly quicker warm up, and the cooling side would help prevent carb overheating...?

I still use it even with my weber conversion and have had no problems.



mark /ubbthreads/images/graemlins/driving.gif

Re: intake manifold cooling

It is actually heating the intake manifold to the "regulated" temperature of your engine cooling system. This is to normalize the vaporization of you fuel and aid in equilibrating the fuel air mixture.

Virtually every carburated engine there is had some method of running coolant through the intake manifold.

Mike

Re: intake manifold cooling

So, Unicorn, you're saying that the purpose is to get the fuel/air mixture regulated temperature-wise so as to closely match the temperature inside the cylinder ... I assume this facilitates better ignition of the fuel ... right? ... I'm certainly no genius mechanic, & haven't worked much on engines particularly, but I'd never before heard of this ... guess I thought the intake manifold was just a connector from the carb to the engine.

Next question ... if the rubber hose the water pump to the manifold is leaking (ever so slightly) will this cause damage to the manifold, or to some other part of the engine? ... or will it cause it to simply run inefficiently? /ubbthreads/images/graemlins/confused.gif

Re: intake manifold cooling

a leaking cooling system will cause damage. it should be fixed. as for the rest, ..well i am no genius either. just (like you) kinda wondered about it..


mark

Re: intake manifold cooling

Not Unicorn, but, since I'm the one who made the statement, thought I would try to field this one too. /ubbthreads/images/graemlins/smile.gif

It is just a connector. But, while it is connecting, it is trying to make the air/fuel mixture as homogenous as possible. The Idea here is if you can get a truely homogenous, stochiometric mixture, you will have the most efficient combustion and if you got everything else right, the most powerful engine. /ubbthreads/images/graemlins/cool.gif If the fuel is not fully vaporized, it won't burn efficiently and maybe not at all. /ubbthreads/images/graemlins/frown.gif Not very efficient and actually harmfull to your engine. /ubbthreads/images/graemlins/frown.gif

If that connector hose leaks, I would imagine it to have little to no effect on the operation of your intake manifold...UNTIL you have leaked enough coolant to effect the operation of your cooling system. /ubbthreads/images/graemlins/shocked.gif (It will undoubtably get hotter. Your vaporization will probably get better. Well, until it get too hot and every other part of your engine complains. /ubbthreads/images/graemlins/frown.gif
I don't know if it can get hot enough to cause mixing/combustion problems. /ubbthreads/images/graemlins/confused.gif
I do know that I don't want to find out with my engine. /ubbthreads/images/graemlins/nonono.gif
Fix the hose and clamp (cheap) and /ubbthreads/images/graemlins/driving.gif on!

Mike

Re: intake manifold cooling

thanks Mike ... I know I need to get it fixed asap anyway ... got parts on the way ... here's something else I'm thinking ... tell me if you think I'm crazy ... problem started the same day I turned the heater valve to the "on" position (it was a chilly morning and I hadn't run the heater for several months) ... could it be that with the valve "off" it wasn't circulating any coolant through that portion of the system, but when on the pressure built up and caused the tiny leak in a rather old hose? ... what I'm driving at is, is the leaky hose a sign that I've got a malfunctioning thermostat? ... or might it simply be a dry-rotted hose that cracked under pressure after several dry months? ...

... thanks again for the insights ...

Re: intake manifold cooling

Mark,

I had an airbox made from stainless steel and it is fed by a K&N out front of my radiator. I am running dual DCOE's, so there is no provision for the intake heating coolant system. It still starts and runs good in the cold (I've run it down to about 10-15F), but is slightly less efficient (probably because the denser air makes it run a bit too rich). I'm amazed by those cooling numbers that Dave gave us. I've been thinking about making an injection molded intake (TWM offers one for an exorbitant price of $600 with the proper holes cut in the mounting face) and also ceramic coating the intake and headers (the headers are already wrapped). I believe this should get me a few more horsepower, esp. after the car has been idling a while. I can send pictures and approximate dimensions (I didn't write them down) of my airbox, but it wouldn't really apply to the downdraft at all.

Re: intake manifold cooling

I don't know the cooling system plumbing of your car, but I would tend to doubt that the flow through the manifold is controled by the heater valve. /ubbthreads/images/graemlins/confused.gifThat just wouldn't make sense. /ubbthreads/images/graemlins/confused.gif But, even if it did, you won't have more pressure because the valve is off, only more or less flow. I said that and now I will add that if the manifold were on the return side then when the heater valve was closed you would have a low pressure zone due to it's being scavanged by the cooling pump. A highly unlikely scenario. /ubbthreads/images/graemlins/confused.gif


/ubbthreads/images/graemlins/cheers.gif
Mike

Re: intake manifold cooling

... that''s why I originally asked about the direction of the the flow ... oh well, gotta fix it anyway.

... thanks again, guys for your help ... /ubbthreads/images/graemlins/cheers.gif