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StuartG

Cold air intake

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11 hours ago, ed_h said:

This is my fresh air induction arrangement on my carburetted TR6, and my version of a heat shield.  The heat shield has a reflective surface, an insulating layer, and an air space.  The graph is on the bench, not in the car.

Ed

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That looks good Ed. It’s what I expected a heat shield to look like, not the vertical one sold by Moss. 
Just need to make one for my 4A now and find a neat way of attaching it like you have.

Chris

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Hi Chris,

from time to time I am asked why I do not to fit a heat shield on my TR4A / SU HS6 carburetors.

This is because every time I stop the engine and touch them - they are cold! One time I even found them wet from condensing air humidity!

This is because of the evaporation of the petrol, not similar what you see on the surface of a camping gas bottle, but this way.

So check first before you do the effort.

Ciao, Marco

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The heat radiation “breaker” that Ed has installed will certainly help to reduce risk of vapor lock when the engine was stopped when hot and then re-started after some time, a known issue for classic cars.

Ed’s masterpiece keeps inspiring me and probably many others. Wish I could match or even come close to your skills.

Best regards,

Waldi

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On 11/3/2019 at 11:35 AM, ChrisR-4A said:

Hi Stuart, I have just added a cold air intake to the 4A, do you have the flexible hoses to the inlets on your air box , these could be routed to an area open to cold air from the front of the car. As they feed the air box before the filter this should not introduce any pressure into the inlet which would adversely affect the mixture.

Chris

 

 

 

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Chris,

I'm just stripping my TR4 for the rebuild and been considering replacing the drivers side wheelarch with a new TR6 wheelarch with it's preformed "indentation" for their injection which will do nicely for my car with it's various carb injections I'll be going through (hopefully). I notice there is a smaller (I think) wheelarch indentation on yours, did you do this yourself ?

Mick Richards

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.

I don't know if it's of any interest or help to the OP,  but my ex-boss who was engine designer for Rootes, and also used to race / hill climb once explained to me that cold air expands more during combustion than hot air can (well that was my understanding of what he said anyway) and that hot air taken in over the exhaust was to prevent carburetor freezing in the winters they used to have.  His own cars took intake air in from before the radiator.   And I understand a trick used in hill climber sprints was to place dry ice inside the air filter.  

When I had a Jaguar 3.8 S-Type,  a few years ago now,  its air intake was from directly over the exhaust manifolds.  And as I also hated the look of the air filter over the top of the engine I sought to change it .

This is as it was when I bought her (standard configuration) . .

1526477892_stype007.thumb.JPG.366154c2ec146ad4726b90a0e762644a.JPG

 

And (below) is to how I changed things around . .

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^ I just think that motor is a gorgeous piece of engineering !

.. but the sneaky thing about this is that the twin air filter you see is blanked off - It is simply being used as a air plenum.  And the flexi-pipe you see going out through the inner wing leads to an XJ40 air filter housed under the front wing  ..right the way forward to besides the headlamp.  Naturally its own intake was shielded and so positioned not to fill with road spray or grit. Indeed it was further taken down to just below the front valance panel, so not noticeable when looking at the car.   I don't like engine bays filled with pipes and cables anyway,  but as you can see - running a decent sized pipe forward within the engine bay wouldn't have got passed the radiator. 

Anyway I thought it was a neat solution, not least because  it used a standard Jaguar air filter box (later ones were in plastic, so non corrosive). And of course there was next to no air induction noise to be heard either.   It worked well and, perhaps psychological,  it definitely felt quicker.  

Pete.  

 

Edited by Bfg

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No Mick, it was on the car when I bought it, I was told by a PO that it was a new wing fitted in 1979 and that it was meant for a TR5 as that's all that was a avail back then. It also doesn't have the shelf for the horn which is why both my horns are on the LH side.

So far I've only tested it in garage for air flow by placing a large household fan in front of the car. The new pipe does direct the airflow fairly evenly to the underside of  both air filters. What I did notice was that no noticeable airflow was entering the underbonnet space from anywhere else so without the new inlet most of the underbonnet air must be that coming through the rad, which is obviously at  higher temp than ambient.

Chris

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Thanks Chris, I thought it was smaller.

I shall be fitting a cold air box onto the carbs but I'm not too worried about pressurisation, the corrugated pipes which you have fitted and I have used also previously, cause a turbulence inside the pipe and a degree of "stalling" of the airflow. This means the carbs draw whatever they need from the pipe the advantage being it's cooler. If on the other hand there was smooth bore piping with gentle bends available I would be looking for a sealed air box and trying for a small increase in ram air pressure.

This is what you end up with when you've 48 hours before a race including a rolling road set up and making inlets.

 

 

 

Mick Richards

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Edited by Motorsport Mickey

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Looking at the lack of space between the exhaust manifold and the throttle bodies and their linkages it looks like it's going to be very difficult to get a heat shield in there. Has anyone fitted a heat shield on a Lucas injection TR6 ?

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As a picker up of unconsidered trifles I recall that complete evaporation of fuel in a correct mixture will reduce its temperature by about 20C. Low enough to cause condensation to form on a manifold - in theory. Indeed the short pipe from the SU to the blower on my 6 drips condensation after a run on a humid day.

Peter

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I made this heat shield out of polished stainless, has blanket on underside. The top two mounts bolt into standoffs that replace the two nuts on the head studs. The bottom mount is a captured bolt stainless zip tied to the header.

E164224B-F638-42A7-89E7-99925B3EE519.jpeg

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.

Out of interest, does anyone know how much does it cost to have manifolds ceramic coated.?  That has the advantage of keeping the heat within the exhaust pipes, which it is said, because of the gases'  lesser viscosity improves exhaust extraction.  It does help keep under bonnet temperatures down which is good for wiring bits n' bobs.  The 4A, I'm in the process of buying, has a 4 into 2 into 1 exhaust,  so the likelihood is I'll use heat wrap on those down pipes. But if affordable then I'd prefer the coating. 

As an aside I put a heat shield on my Jag - under the manifolds, between they and the block and its water jacket ..just a few inches away.  The big straight-six in such a tiny engine bay is not particularly prone to overheating, but it can boil the stew when sitting for long in traffic.    The Triumph has the space of a ballroom by comparison !   

And on my Citroen, with a boxer engine, I added a heat shield specifically to contain the heat around my inlet manifolds, because on that car the long inlet manifolds took an age to heat up, even though the oil cooler was positioned immediately under the carb.  Starting and cold running was seriously compromised because the fuel would condensate in the manifold before getting to the engine.     

And on my motorcycles (Sunbeam and Norton) there's no heat shield, but the inlet manifold has an insulator between it and the cylinder head.  

I note many older cars had a shield under the carburetor, but that was not to keep it cool , but rather to prevent any petrol leak dripping directly onto the exhaust manifold. Most manufactures didn't seem to think hot inlet manifolds were an issue.

.

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Hi folks, 

the SU H6 and HS6 are such a genius construction! So ridiculous simple, even without a idle jet!

On my TR4A the HS6 do never suffer from any heat, not in any case. Even not at the hottest summer day (38 deg. C this year).

Anything about a heat shield on the TR4A in my opinion is wishfull thinking of not existing problems.

Check it, touch them anytime and any case after and before you drive the car.

The TR6 may be different, but I have doubts about this.

Ciao, Marco

Edited by Z320

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Being skeptical by nature, I've always questioned the efficacy of ceramic manifold coatings. Does anyone know for sure what mechanism is in play if they do work?  I wouldn't think such a thin layer could contribute much resistance to conduction.

Ed

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Btw:

do nothing that makes the cast iron TR4A exhaust manifold hotter, if you want to keep an original one.

They crack from this permanent hot-cold-hot-cold after now about 50 years.

And here are not so many around anymore as spare parts.

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8 hours ago, ed_h said:

Being skeptical by nature, I've always questioned the efficacy of ceramic manifold coatings. Does anyone know for sure what mechanism is in play if they do work?  I wouldn't think such a thin layer could contribute much resistance to conduction.

Ed

There was an extensive thread about this a couple of years ago. IIRC someone did some measurements that showed the coating does very little.

Found it :

 

 

Edited by RobH

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RobH,

you should have linked again to the killer evidence that you provided in that previous thread: http://insulationinstitute.org/wp-content/uploads/2016/01/CI224.pdf

From the North Amercian Insulation Manufacturers Association, "Insulation Products for Commercial and Industrial Applications: Thermal Performance of Coatings Used to Insulate Pipes, Ducts, and Equipment.     This fact sheet analyzes and discusses performance claims and recommendations by manufacturers of coatings (sometimes called ceramic coatings) used to insulate piping and equipment in mechanical applications."

This is specifically about ceramic coating, and compares that with 1/2" thick mineral fribre coating.

The conclusion?  "The testing shows that the coatings, even at thicknesses that are above those typically installed in field use, are three times less effective as insulators than ½ inch of mineral fiber insulation."

What is lost in the hype about ceramic coating is that whioe it is used in high perfomance vehicles, there the purpose is the keep the exhaust gases at hot as possible for as long as possible, accelerating their exit and improving scavenge.     This it achieves.   If some heat loss to the external area occurs then that is only a fortunate extra.

John

 

 

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On carb engines disconnecting the inlet manifold hot water pipe will help, assuming the car hibernates.

IIRC Vizard advised a high polish on ali inlet manifolds to reflect radiant heat.

Peter

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A highly reflective surface will certainly reduce radiative heat transfer in most cases, but the challenge in an engine bay is keeping it shiny.  Oxidation, corrosion,  dirt, or other surface conamination will all reduce the effect of the shine.

Ed

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20 hours ago, john.r.davies said:

you should have linked again to the killer evidence that you provided in that previous thread: http://insulationinstitute.org/wp-content/uploads/2016/01/CI224.pdf

That makes interesting reading. Thank you for sharing it. 

Table 2. of this report records the experimental results of heat flow from a pipe at 350°F  (177°C)  to an ambient room temp of 90°F  (32°C).    Their bare metal pipe’s heat flow is 1,564  btu/ft2·h and that with a 0.060” coating is 727 btu/ft2·h.   ie.,  just 46%  of the heat is getting through.   

The fact that half-an-inch of fibre insulation may be x3 better still - doesn’t alter the tremendous performance of this very thin (just sixty thou of an inch thick) coating. One might equally say that a cavity-insulated brick wall is better, but neither is so practical nor attractive a finish for our application.   Or else one might consider just how well 0.060" of fibre insulation would perform ? !

The report concludes goes on to state that  “Arguably there may be some instances where coatings could be suitable for use - to lower burn potentials in some hard to insulate areas, for example.”    That sounds good to me too. 

The 177°c  test is a very low temperature compared to exhaust manifold temperatures, but perhaps is an indication of how it may perform at the higher extreme.  Jaguar cars (..which back-in-the-day were very much built down-to-a-price) used ceramic coatings ..even on their saloon’s exhaust manifolds.  And as often suggested - racing chaps very often consider the coating or wrap worthwhile enough to spend their money &/or time on.  I’m not clever enough to dispute their wisdom,  but reason suggests -  if more heat is coming out of the exhaust tail-pipe then that same heat cannot have been lost through the exhaust manifold.

Based on the figures in this report - I’m impressed with these coatings.

NB. I haven't yet, but will now read the link provided by RobH - Thank you.   ..perhaps I might think differently after considering that.

Pete.

p.s. " NAIMA is the association for North American manufacturers of fiber glass, rock wool, and slag wool insulation products."  so they mightn't be slightly bias in the wording of their report would they ? 

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That article, really aimed industrial process piping, and not automotive exhaust pipes,  uses 1/2" of pipe insulation as the standard for comparison, so of course a much thinner coating will have inferior performance.

For auto exhaust systems, the standard for comparison would be bare uninsulated pipes. This makes the ceramic coatings look pretty good, as Pete notes.

So, just changing the base case would lead to a conclusion pretty much the opposite of that in the article.

Ed

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32 minutes ago, ed_h said:

For auto exhaust systems, the standard for comparison would be bare uninsulated pipes.

No Ed - the discussion thread that link came from was comparing wrapped exhaust with the ceramic coating. Although exhaust wrap isn't 1/2 inch thick one would expect the outcome to be on similar lines, if not as marked.

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I was really just thinking within the context of the article in the link, not the thread it came from. Some people apparently took the conclusions of the article as evidence that ceramic coatings don't really work, while the data indicates that they do indeed reduce conducted heat flow by a significant amount, compared to a bare pipe.

Ed

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If you follow this thread to page 5,  Alan "Old Tuckunder" did some real-world measurements on his exhaust. His words say it best.

 

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