TitosToy

hey guys, here'a a few questions about the coolant passages that surround the spark plug area. i've read in a website (forgot which one!!) awhile back and they were selling engines that they port the coolant passage above and below the spark plug area for better cooling. is this true and has anyone done it? any adverse effects?

classicauto

iTrader: (3)

I've heard about porting the coolant passages as well....seems to me though that you would want the coolant to stay in the motor for the engineered period, if you port them wouldn't it enter/leave faster, thus absorbing less heat from the motor?

TitosToy

from the website it was explained that when you port it, it dissapates the heat quicker and you have a cooler-running engine, especially at hi revs. any thoughts?

kungfuroy

iTrader: (6)

its more like grinding in ribs to the coolant passages around the spark plug area. The ribs add more surface area to coolant passages, more surface area for more cooling efficiency

13b4me

They engineered it based on on stock engine specs... When the engine is upgraded to the point where it affects thermal efficiency, it would seem like the more coolant you could move through the engine, the better...

TitosToy

so this would be a better upgrade for an above-average modded engine huh?

classicauto

iTrader: (3)

True, it was engineered for the stock setup.

However it just seems to me that porting them would make the coolant go through faster and thereby absrob less heat......but maybe its the opposite, just seems to me that if I had two molten hot blocks of steel - one with a hole straight through, and one with a couple holes that curved round a bit - and poured 1 cup of water through each, the one that had the water in it the longest would be cooler sinc the water had more time to absorb the heat.

What kind of info do they have on this site? BTW, where is it?

Edit: Actually just realized something...."the more coolant you move through the motor the better".......why not just add a super high flow electric water pump, then you would be changing the actual flow of the coolant in the whole system as opposed to just decreasing the amount of time it spends in the block? thoughts?

TonyD89

iTrader: (10)

Check out RB's site. They cut ribs into the cooling passages. They have pics.

TitosToy

i'm still looking for it...gimme a sec...

Dinnercoat

Ribbed. For her pleasure.

13b4me

You can add an electric pump, and alot of the Aussie high HP drag cars actually do just that... And the one thing you may be forgetting is the housings are aluminum which transfers heat extremely fast... I doubt you'd lose any cooling ability by moving the water through the block at a higher rate... With it being ribbed for more surface area, and more coolant actually making contact with the aluminum, it would essentially dispel the heat alot more efficiently I think...

BLUE TII

iTrader: (9)

Yes, you cut grooves into the waterjacket in the spark plug area.

It increases the surface area and so increases the heat transfer out of the rotor housing into the coolant.

The '86 on rotor housings have a thicker casting in this area to promote fast warm up, so there is plenty of material to safely remove.

Since the spark plugs cool themselves through the water jacket it also helps keep their temps down which decreases the chance of detonation/preigniton just like running a "colder" heat range plug (which also should be done on high HP rotary, I use BR10EIX).

I found the easy way to do it is to buy a dremel bit (looks like a thick ~1/4" diameter sawblade on a shaft) and chuck it up in a drill press. Put a nut above and below the drillpress depth adjuster so it is locked into position. Move housing around while the bit cuts the passages. Move bit down a set amount and repeat.

This pic from my rebuild thread shows the results.

TitosToy

sorry guys, i cant find the site but what you said bluetII is exactly what i read

NZConvertible

Unfortunately that's exactly what does happen. This is a long-proven fact, and is why you shouldn't run without a thermostat (or replacement restrictor plate).

13b4me

So with a restrictor plate, what size passage would you recommend allowing?

BLUE TII

iTrader: (9)

Actually, for a RACE ONLY ROTARY I believe Racing Beat recommends removing the thermostat and blocking the bypass port.

No restrictor.

This provides the highest flow possible for best cooling.

Note; not what is done in the piston racing world.

RotaryEvolution

iTrader: (30)

you won't be able to convince a few people here regardless of what some people say since they have their own beliefs and won't believe anything unless they try/see for themselves.

personally my engine ran coolest with a cored out thermostat and plugged bypass port. porting the rotor housing cooling passages isn't worth the effort IMO, the benefits would be so minor that it is more beneficial to simply experiment with the flow of coolant through the radiator and thermostat than through the engine itself, also in the mixture of the coolant. porting and or modifying the housings near the spark plugs would be a last ditch to reduce temps. there is plenty of easy ways to reduce engine temps, one is simply upgrade the radiator..

FC3Spro.com has a listing for ported rotor housings, i believe what the original poster saw. this involved porting where the housings met the irons for more area.

Kyrasis6

This grinding ribs is a stupid thing to do, for one it will cause cavitation above a certain rpm, this not only increases pumping looses to hp but can also cause little bubbles to form on the passageways that eat away at the metal.

A local speed shop here also advertised that the ribs help increase regidity which is true but they also greatly increase stress making them much more likely to crack, both from an engineering standpoint.

importsown

Uhm, maybe im missing something but wouldnt porting the coolant passages (making the passages bigger, hopefully we are all on the same page) increase the time the coolant spends in the block? Its just like intake manifold porting, as well as the auxillary ports. The bigger the ports, the more volume but the lower the velocity. I actually think this would be a very good idea. Im not sure about the ribs though, they would probably cause too much drag IMO, but i guess it all depends on how deep they are, etc.

Maybe im just rambling, but it seems the opposite to me as what your guys are saying?

Kyrasis6

Also both the the radiator cap and thermostat function to keep pressure in the coolant system which raises its boiling point. Another effect the thermostat has is to create a pressure differential between the engine and radiator to maintain good flow through the radiator.

Any heat transfering media fluid needs a certain amount of exposure time in order to cool efficiently. A good example, start up a propane torch and get the flame as big as you can get it, or do it with a butane lighter if your not as confident. Move your hand through the flame quickly if you do it fast enough you won't get burned. Move your hand throuh more slowly and you'll burn the crap out of yourself. This is based on how fast the part can dissapate heat into the coolant and how fast the coolant can absorb it. If the torch or lighter where the housings the torch would transfer heat much faster then the lighter, this would be like the difference between something iron and something aluminum giving off heat. At the same time the coolant has a certain amount of time required to absorb the heat, too much time and it does not absorb any heat, just like your hand through the flame, move it too slow and it saturates not allowing the parts to get the heat out.

Having said that a modified engine should only start running hotter if it generates enough heat to saturate the coolant. If your temp gauge doesn't change then you don't need to modify anything. If the gauge does rise higher at any time then measures need to be taken to bring them back down to stock levels. Mild porting of the restrictions in the coolant passageways would then help by allowing the saturated coolant to get out and colder coolant to get in.

Machining the passageways closer to the combustion area would decrease the thermal path to the coolant and allow the heat to get out faster with a sacrifice of strength.

Kyrasis6

Its a ballance, and like you said just like an intake, you would either need to keep the porting to a minimal, reduce the drag in the system, or port it and push more volume through it in order to maintain velocity.

Just like a restriction in a river, water the coolant speeds up and you get rapids.

Would have gotten that in on the last post but my hands type faster then I can arrange my thoughts, lol.

Edit: Another thing to do is install a restrictor in a cooler part of the engine and port the hotter part, this diverts extra volume to the hotter area and brings the velocity back up if the coolant is flowing slow enough to heat saturate.

importsown

Very good posts kyrasis, and thats alot like what i was trying to get at. If you can increase the volume while maintaining the same velocity, wouldnt that be the ideal situtation?

tekwiz99

one than need bigger pump and, in contrast, stealing more power by the belt

tinvestor

I think there is some confusion about what this is being called. This IS porting in the fact that you are altering the shape it IS NOT porting in the sense that you are making the passage larger. Volumetric growth of the passage is slight and the passages useable surface area is increased but the passage flow is not accelerated by being enlarged it is in fact slowed by the volumetric increase. Think of the passage as a straw if you cut the the straw in half and insert a larger diameter segment in the middle it does not accelerate the flow through that area it in fact slows the flow because the exit is still the same size as it used to be but it holds more liquid.

This is an extreme example but if you pour water thorugh a straw into a cup with a straw sized hole in the bottom does it let the fluid out faster than if the water was flowing just through a straw? The answer is no. However the water does stay in the desired area for a longer period of time. For this example assume that the pressure at the exit hole is identical for both the straw and the straw sized hole.

Kyrasis6

Ah ok, didn't know that is what was meant by porting, but the example you gave is the same as the river example, just didn't explain that part of it.