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Discussion Starter · #1 ·
Hey peeps dont know if anyone has done this before.

You know how our intake manifolds get ridiculously hot after a long drive?
I know i cant even touch it its gets that hot.

Heres a great way to make the manifold way, way cooler than stock. It will only get to around 50 degrees celcius (122 degrees F)which is a huge improvement, the car will make more power and be better on gas.

I pulled off my manifold and got my local fabricator to weld up the large coolant ports on the head flange. I also had him weld up the EGR holes and all the other factory shit. This was very cheap. I then took off all the coolant circulation pipes from the manifold and just put a U bend bypass hose on those little spigots above the oil filter.

Of course, the heater will now be bypassed too, but you can put an adapter pipe in your top radiator hose and run it to the heater coil if you want your heater to work. If you choose to bypass, make sure u plug the other heater hose tho (return hose).

This way no super heated coolant at all goes anywhere near the manifold or the throttle body, it just through the engine. You'll make sure that the air going through doesnt get heat soak again after the intercooler does its hard work. Also reduced you chance of water leaks as you have way less gay messy hoses going everywhere

It seriously works and I can now hold my hand on the manifold for ever and i hardly feel any heat at all.

I know it sounds like one of those ads lol but I just thought it would be good to share with you guys.


BTW i insulated my mild steel post-intercooler pipes with refrigeration grade pipe insulation too, $15. After a long (1 hour) drive boosting and sitting in traffic the pipe is still at ambient temperature! it used to get over 70 degrees celcius (158F) due to heat soak from the engine bay.

It also looks good coz its matt black and makes ur piping look fatter lol

Cheers guys
 

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mate sound like a great idea but did you notice a power increase or reduction in fuel consumtion? pics would be great help for ppl who want to replicate
 

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Discussion Starter · #3 ·
thanx mate. soz cant give pics its back on the car now....

problem is i also fitted an aftermarket computer and a big turbo and throttle boddy and a whole heap of other stuff at the same time so its quite difficult to gauge the difference.

Im sure it would give a respectable increase tho. probly not worth it if you go by a power-per-dollar basis but if youve got the manifold off already its worth a go.
 

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Do you know why the manifold is too hot to touch after a long drive?

Because the heat transfer is insignificant. If the intake air would gain heat, the intake would be much less hot.
 

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Discussion Starter · #6 ·
No... its coz the coolant flowing through it it way hotter than the boiling point of water....

Thats why its hot....


Mate, why is then, that my mild steel pre-intercooler pipe and half of my intercooler get really freaking hot when im boosting?

Oh yeah! Thats heat transfer! The same amount of air is flowing through the manifold, but this time, we have the cool air absorbing heat from the manifold instead of the cool pipes absorbing heat from the air.

The temperature difference and therefore heat transfer between the air and the vessel is similar in both instances.

As something gains heat, it looks desperatly for a way to get rid of it. Since the manifold is stinking hot, it can either release its heat into the engine bay or the air inside the manifold. Since the engine bay is also stinking hot the only place for the heat to go is into your air charge.

Im not saying itll give you an extra two hundred horsepower but in our cars, which are horsepowerly challenged compared to most other imports, any gain in efficiency or HP, even though small, is a good thing.


Oh and BTW, if the heat transfer is insignificant, why did mazda decided to heat the manifold?
 

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There's no coolant lines in Mazda intake manifold.

Edit: oh, the 8v FET lump does have. That's strange. Then again FET were originally non-intercooled to begin with

BTW let's think about what's happening at the intake piping. The air is swooshing past, and every now and then an air molecule passes it's energy onto it. What happens? the pipe that doesn't go anywhere slowly collects heat from the air rushing inside. The pipe gets mighty hot because it has little cooling, and the air is constantly bombarding it with energy.

What happens with a hot pipe and cold air? Every now and then a rushing molecule picks up a bit of heat from the pipe, which, again, has no means to cool itself. You got to remember the air only spends some milliseconds in the intake.

In a nutshell: you have tons of air warming up a few kg's of metal, and few kg's of metal warming tons of air. Which would you think have more effect?
 

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Ah, so the F2 does have the same coolant flow into intake afterall... A leftover from carburated design.

Still I don't give much weight on the manifold heat issue. For instance, some air cooled designs use shrouds around exhaust manifold for interior heating. Even then they aren't exactly pressure cookers.
 
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