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Old 10-29-2014, 12:39 AM   #61
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Quote:
Originally Posted by patsmx5 View Post
That is true. But you can calculate the amount of cooling, it's m*CP*dT, mass flow rate time heat capacity times change in temp. So that takes into account how many times it passes through.

The tilton is rated at 1.9 GPM.

This 75W 90 oil Mobil 1 Syn Gear Lube LS 75W-90 is listed at having a density of 0.859 g/cc. 1.9 gpm is 7,192 cc/minute, so that's .859g * 7,192 = 6,178 grams/minute, or 6.178 kg/minute.

Cp of oil is 1.67 kJ/kg*K I think.... Not 100% on that. Can anyone confirm?

So if our GOAL is to keep the oil at say, 230*F max, then the oil exiting the trans will be 230*F, and we'll cool it a bit and then return it to the trans.

230*F = 110*C
So if we cool the oil say 50*F, which I would think would be pretty reasonable/good, that's 230 - 50 = 180*F = 82*C exiting the heat exchanger heading back to the trans. So temp drop is 110-82 = 28*C I didn't put numbers in Kelvin but the delta T will be the same K or C.

heat removed would be m*cp*delta T, so 6.178 kg/minute * 1.67 Kj/kg *C * 28C = 288.88 KJ/minute, which is 4.81 kJ/sec, which is basically 4,810 watts, or 6.46hp worth of heat.

I think.... That's actually a decent amount of cooling, more than I thought it would be.
Didn't use a calculator, but your math seems legit, at least to the 2 significant figure math I do in my head.

When I think about it, I do not think that a 2 GPM pump should even be questioned when it comes to flowrate limitations. I think we can all agree, the size of the heat exchanger used will affect the overall cooling performance of the system more than the pump. Basically, a very reliable pump is needed, but not something with insane flow rates, since the overall system will be limited by the heat exchanger used.

I am speaking from a theoretical standpoint of course. My Miata is stock, and won't need this cooling measure for a VERY long time. Just got accepted for the masters program in Mech. Engr.

I want to add that you guys who are using up transmissions like consumables at high power levels may benefit from this even more than I previously thought. Previously, I was just focusing on the gears themselves, and how temps above 250 F or so will reduce the gears allowable stresses to a degree. But now that I think about it, a lot of gearbox failures point to a problem with case flex, correct?

If this is the case, look at a table comparing the stiffness of aluminum to temperature, and you will see that at 350 F, aluminum loses about 5-10% of its stiffness as compared to 230 F. Basically, adding a sufficient transmission cooler will decrease case flex by up to 10%, which leads to better gear meshing, and increased transmission life. Adding a cooler will increase longevity in multiple ways.

Now, I'm not saying that this will cure your transmission problems at 400HP, but at 275HP, it may well be a viable solution. The 6spd can only be taken so far before a stronger transmission should be used, but everyone here knows this.
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Old 10-29-2014, 09:13 AM   #62
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I think the important part in the nascar cooler pictures is the fact that the cooler uses a "toothed" belt instead of a V belt or ribbed belt. I was worried about offsetting tension earlier when someone mentioned the use of a cheap tensioner. I think a belt that works like a timing belt or a chain is probably the way to go because you don't need the tension required with a smooth-line belt. I wonder if a motorcycle sprocket can be made to fit the input shaft of the diff?
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Old 10-29-2014, 09:18 AM   #63
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I forget the source we used but we bought some reasonably priced custom sprockets that bolt to flanges for the FSAE car. It was under $100 for like a 13" diameter sprocket for 5-20 roller chain. Something like a 30tooth sprocket for like #25 chain shouldnt be too expensive to have cut to match the pinion flange.
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Old 10-29-2014, 05:30 PM   #64
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The nascar pumps use a v-belt or multi-v belt. The pump should turn very easily because it is making very little pressure. I think the multi rib belt running against the smooth driveshaft would be fine with just a couple of lbs of tensioner pressure. We aren't trying to pressurize a steering rack, just move a little oil around with very low resistance. Just a little flow, and not much pressure.
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Old 10-29-2014, 05:57 PM   #65
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Well right now I'm thinking that if ~2 gpm is "enough" cooling, then I'll just go with an electric tilton pump for 200 bucks. I can buy that and get it hooked up/working quicker than I could fab/design a pump that's driveshaft driven.

New question: Ideal scenario, what "temp" would you want the oil in the transmission to be? For best reliability, of course.

My guess is that to a point, cooler is better for reliability. So 180*F is better than 230*F, and 230*F is better than 280*F, etc.
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Old 02-28-2015, 06:18 PM   #66
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I have a core and a pump I was going to use to build a trans cooler but never got around to it because I was not thrilled with the fill /empty ports on the trans I was going to use for the plumbing. I'm concerned about having a 90 AN fitting located the drain plug for the obvious reason that it could get torn off if one were to go off track. perhaps this is not that big of a deal but when I was looking at what I had on hand it seemed like the line would hang pretty low. any thoughts? perhaps they make a 90 with a weldable bung on one side a the 90 an fitting on the other so then one would use a straight fitting versus using traditional 90 to an fitting attached to a bung.
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Old 02-28-2015, 06:21 PM   #67
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The drain plug is a straight metric thread. I'd figure you'd just use a banjo fitting. I realize that pressure drop on the low side of the pump is bad, but not the end of the world.
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Old 03-01-2015, 12:34 AM   #68
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Quote:
Originally Posted by Leafy View Post
The drain plug is a straight metric thread. I'd figure you'd just use a banjo fitting. I realize that pressure drop on the low side of the pump is bad, but not the end of the world.
ha yeah right. a banjo fitting is the way to go. I don't recall the size but as I recall the plug is larger that what one would use on a, say 8 AN banjo so I/we would prob need to drill the stock plug. perhaps not but I thought at least one of the plugs was pretty large. back to the line size, it 8 AN what one would normally use?
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Old 04-01-2015, 09:50 PM   #69
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So i'm going to bump this thread instead of starting a new one, because my question is more-so just off the top of my head instead of being an actual question that needs answering.

My NB will be gutted when it becomes a full time track car, and i know the transmission tunnel is reported to get VERY hot, for obvious reasons. To keep from burning legs, i was just looking for a quick and simple method to fix this, and came up with a "hey, that might work."

Aside from adding some insulation / heat tape, wrap, whatever to the underside of the transmission tunnel, what about adding some ducting from the cowl area of the firewall?
Basically, just running X amount of hose from the high pressure area in the firewall cowl to the top of the trans to keep all that heat from radiating into the cabin?


My personal thoughts, please feel free to critique:

Pros:
Simple / cheap
low chance of failure - dont fix what aint broken, if the hoses do nothing i just end up with a burned leg, not a fragged trans.


Cons: (these may be excessive, but i'm trying to cover ALL angles)
1. Basic aero says air under the car is bad, and this is basically actively pumping air down there.

2. I'll eventually be ducting the radiator through the hood, this car will be seeing double duty between my Fiance and I, so i am going over kill on the cooling mods to keep the car alive. If the radiator is ducted through the hood, does that affect the high pressure zone at the cowl?

3. uneven cooling. The thought would be to direct the air over the top of the trans to keep heat out of the tunnel, but i know next to nothing about heat transfer. Will "cooling" the top of the trans interdependently of the bottom cause issues? I know heat moves from hot to cold, so it would essentially just act to "pull" heat from the bottom of the trans correct?



Lastly; maybe i have not done enough research yet, i am still new to this platform, but i am not new to motorsports. I know if it were this easy someone would have done it already, but why not use something like the mustangs?
Ford Racing Boss 302 Mustang Manual Transmission Cooler Air Scoop M-5025-MBR (11-14 GT, BOSS) - Free Shipping
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Old 04-01-2015, 11:58 PM   #70
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I don't think that an air duct will help much, there is a lot of air movement there when you are going 100mph+, most of the heat is radiant heat form the glowing exhaust system.
This works well for me keeping exhaust system and transmission heat out
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Old 04-02-2015, 09:44 AM   #71
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Simple enough, thanks.
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Old 04-02-2015, 10:11 AM   #72
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Adding sheet metal shielding with an air gap around the exhaust itself like OEMs do is the most effective way to keep heat out of the trans and the cabin. That is why they do it. After isolating the exhaust, any excess heat created by mechanical action within the transmission would be what you are concerned with.

As you mentioned, excess air under the car promotes lift. Lift is undesirable.

Ducting the radiator to the hood is good for cooling and good for reducing lift. That is why many race cars and performance cars do it.

Our transmissions are poorly designed for air cooling. The manufacturer does not expect it to generate much heat in an OEM configuration and expects it to be shielded from the exhaust. If designed for air cooling it would have many fins outside and within the case to maximize surface area for effective heat transfer. As it is, it would take a lot of airflow for little benefit. But a small cooler of proper design could transfer a great deal of heat away with only a small amount of air.
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Old 08-02-2017, 02:49 PM   #73
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Back from dead but in searching for some flow information, I ran into a toyota forum when I got side tracked on oil coolers. The following link came up for manual trans cooler:

Driftmotion Manual Transmission Oil Cooler Kit

Quote:
Driftmotion Transmission Oil Cooler Kit. We have been doing upgrades and rebuilds on R154 and other Toyota transmissions for a long time, and one thing we have noticed is that the elevated horsepower level people are running these days creates a lot of heat in the transmission, which leads to excessive wear, and can even cause major failures. We noticed that no one offered a kit to keep a Toyota Supra manual transmission cool, which is where we come in Also, any metal wear that happens inside the transmissions usually stays in the transmission, and gets circulated through the gears and bearings. With our kit an inline filter will trap metal particulates in the oil, and further extend the life of the transmission. The cooler and lines also add more oil volume to the system, which is a plus.

We have assembled some quality parts at reasonable prices that we will keep in stock to assist you with your project. As soon as we can get a few vehicles ready to do full installations we will make more complete kits and add more detailed pictures, but for now it will be more of a DIY offering with some of the hard to find items. Feel free to call Aaron at 909-753-7385 if you want to discuss these items or have questions about an installation on your vehicle.

The recommended way it should be plumbed is the lower drain plug on the transmission will go to the inlet on the filter, the outlet on the filter goes to the inlet on the cooler, the outlet on the cooler goes to the inlet on the pump, and the outlet on the pump goes to the fill plug location on the transmission. The pump should be primed with oil before the first time it is run, and we recommend filling the cooler and filter with oil also. Do NOT run the pump dry the first time it is used. Mount the cooler with the fittings facing up. The cooler is mounted with the fittings facing up so that oil will not drain from the cooler and overfill the transmission when the oil pump is off, and also to keep the system primed with oil. After oil is circulated through the system until you can hear the pump running smoothly, remove the fill fitting on the transmission and fill the transmission case until oil runs out the fill hole, just like you would do normally.

The oil pump we recommend is a metal gear Mocal pump that is designed specifically for gear oil. There are cheap imitations of this pump out there, some even use plastic gears, but Mocal is definitely the best. We include AN-6 adapter fittings in addition to the AN-8 fittings that the pump typically includes. AN-6 hose will allow for plenty of oil flow, especially considering that the transmission only has about 3 quarts in it and the pump is rated to flow 2 gallons per minute.
You can use 3'8" push-lock hose and AN-6 fittings, or braided stainless AN-6 hose. We can even make you custom crimped Teflon lined stainless hoses by just getting the measurements from you.

Another big benefit to our oil cooler kit is to add oil filtration to the transmission. By removing metal particles that build up in the oil and cause bearing and gear wear, your transmission's lifespan will be increased. We offer a special 240 micron filter designed specifically for thicker gear oils. It has a washable stainless steel filter element. A normal 100 micron filter designed for fuel will cause too much back pressure on the pump, and clog up much too quickly, which could overheat and damage the pump

Our 18mm fittings are the perfect replacement for the stock drain and fill plugs, giving you an easy inlet and outlet without having to drill holes in the transmission case. We include a factory Toyota aluminum crush washer with each fitting.

If you have a tight clearance to the tunnel on the fill plug, we have a AN-6 90 degree adapter that will make the hose fitting come out close to the transmission and turn a sharp 90 degree angle.

We have several options for different oil coolers. If it is mounted somewhere that doesn't have good airflow, or you want a fan to keep cooling the transmission when the vehicle is moving slowly or stopped, we have a nice compact top-of-the-line Setrab unit we have used on custom projects in the past. If a fan isn't desired, we have several options for Long and Koyo brand coolers. Since manual transmissions don't have a torque converter constantly producing large amounts of heat, a reasonably sized cooler will be sufficient, it doesn't need to be massive.

We offer a 10amp rated Setrab 180 degree thermostat switch that can handle running the oil pump directly without a relay. If you have a cooler fan also, a relay would be recommended.
It is 1/8" NPT pipe thread, so it could be mounted in a hole drilled in a rib in the transmission case, but we also have an AN-6 inline fitting with an 1/8" NPT port that can be used.
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