DIS Heatsink Feedback

Rich Thomson

Registered User
I have finished a cheap and simple Heatsink for the DIS. This is on my 94 but will start one for the 89-93 which heat soaks much more. Feedback please. I am starting a Howto article which will cover 89-95 DIS cars. I was thinking a 1/16" aluminum plate with short spacers to provide an air gap below the DIS on the 89-93 cars?

Rich

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Rich,

I would get a hold of a IR temperature gun and run a test. I haven't seen how the E-dis mounts, but I would be concerned with loosing the mass of any of the big things it was attached to in exchange for the aluminum.

Aim it at the top and bottom seeing the temp difference with the stock mount, then your modification. You may find that it'll take more surface area to get a significant change, in which case maybe a thicker piece of aluminum and then fin the back side by taking some thin sections out.

Of course it may be just fine. It's hard to know without testing myself as it could be much of the heat I notice is coming from the bracket itself and not the DIS.

Overall it looks like a good idea.
 
Rich Thomson said:
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I was thinking a 1/16" aluminum plate with short spacers to provide an air gap below the DIS on the 89-93 cars?
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The 89-93 DIS has a thin aluminium plate built into its base. So, in my opinion, adding another thin plate of the same size won't help. The thin plate with spacers would function the same as the DIS mounted directly on spacers. The DIS needs to be mounted on a piece of metal that has a larger surface area than its metal base - like the accessory bracket on the 89-93 models or a computer/electronics heat sink with cooling fins. The larger surface area will allow more rapid heat transfer to the air.
I would either mount the DIS in a cooler area which would require the addition of shielded cables, or mount it on a heat sink with fins and maybe add a small computer fan to draw air over the fins when the car is idling.
 
I've looked into this as well. I've gone as far as getting a very rough autocad drawing done for one. The problem that you run into though is that you only have about 1/2" clearance to the stock hood. I was trying for a 3/4" electronics heatsink style, but I ran into fitment issues.

It will work flawlessly on an aftermarket hood, just not the stock one.

Once I realized I had some fitment issues, the project fell to the wayside and I haven't really looked at it since. The design was very much like a computer heatsink though. Lots of small fins to dissipate the heat away from the DIS. It is something that I will probably go back to, but until I have an aftermarket hood, I'm pretty much stuck with what I've got.
 
Maybe a copper plate with a heat tube and a larger finned aluminum heat sink mounted on the side of the bracket on the early cars?

Bah. I'll see if my bud at work has a spare IR temp gun in his trunk and take some readings before and after a run for lunch. That'll at least give a base line.

I'm not so sure the aluminum won't help, but my concern is the air gap using stand offs. I know where that's coming from though with the idea that the bracket is actually collecting heat from other places and soaking itself so that it can't take heat from the DIS. Or on the fender mounted ones, the sheet metal isn't all that heat conductive or massive.

There are some engineering principals involved here that are really beyond garage logic so unless someone figures them out with their slide rule, the best bet is to just do it and test it and see what the results are.
 
Part of the idea is that adding a small spacer like 1/4" - 3/8" to raise the DIS off the top of the AC bracket would stop much of the direct heat transfer caused by a heat soaked AC bracket. Also air would circulate under the DIS and further reduce the temp. The other part of the idea is when lifting the DIS off the AC bracket you need to have a heatsink surface to cover the back side of the DIS module. This is where the aluminum plate comes from. I know a standard heatsink will not fit or work on the back of the DIS.

Rich
 
My concern comes from the lack of surface area of a flat piece of aluminum. But since I don't know the output power of the coil pack I can't try to calculate heat dissapation from the DIS. Thus my only knowledge of the heat from the DIS is when the DIS is attached to the bracket.

Thus best bet would be to use a IR gun to measure your coil pack temp at the hottest point on the top of the coil pack, then try to aim it near the bottom edge and get a measurement there.

Then install your aluminum plate and spacers and check the temps in the same place. If the hottest point on the top of the coil pack is lower with your plate in place, it's very likely that the plate is better able to sink the heat than how it was mounted before.
 
Rich,
The design that you have is simple and it will work to dissapate heat away from the DIS, which is much better than stock. I think with a raised hood, there can be better and more efficient designs to dissapate the heat, but for the stock hood and the limited area with which to work, your design is good to go.

Just a thought for you as a slight change...since you've got approx 1/2" to work with, I'd go with a thicker Al plate (3/8") combined with 1/8" to 1/4" spacers. Then drill holes in the plate to increase surface area to help dissapate heat more efficiently. Granted, you would have to find out exactly how much clearance you've got under a stock hood in order to maximize the space you can raise the DIS above the acc'y bracket without hood interference. That would be the easiest and least expensive way to do it.
 
Given the tight clearances with the standard hood, a heat sink that is similar in design to the one used for the ignition module on the 3.8 n/a may work. The base plate of the heat sink extends beyond the sides of the module and the cooling fins are on either side of the module (both the module and the fins are on the same side of the plate).
 
I don't think any kind of passive heat sink is going to work considering the location of the DIS.

With the ideas presented here, you'll just delay how longs it takes for the DIS to get hot..... everything is going to get heat soaked anyway, and you'll reach the threshold that the aluminum can dissipate heat, and in fact you could cause more problems because the aluminum is going to hold that heat, and it has no where to release to other than the ambient air temperature which is hot once the engine is at running temperatures. Also you have to remember that heat rises, and considering you have an insulator on the stock hood that heat is sitting right up there with the DIS.

For a heat sink to work properly, you need a source of coolant be it air or a fluid that is cooler than what the device is so the heat will travel into that medium. Either the DIS is going to have to be moved, or you need to supply at least some cold air so the heat from the aluminum can shed off its heat to.

Also, a flat peace of aluminum is not going to be that good, considering the surface area and the thickness of the material your using.... you need to increase the surface area by using fins etc.

Just my 0.002 cents worth.

Frit
 
Rich - I live in a hot climate and have dealt with my share of 89-93 style DIS module problems. Here is my take on the situation. The module is like the processor in a computer, it's producing lots of heat. The idea of the accessory bracket mount is to heat sink this heat away from the module. Problem is that bracket gets heat soaked and becomes ineffective in getting enough heat out. My problems always occurred at low speeds in very hot weather, which indicates to me that the underhood temps rise and the heat is not dissapating efficiently enough. I think the solution is a remote location out of the hot part of the engine compartment with a very large finned heatsink with a fan. Then take temp readings on the module to prove/disprove a lower temp. Keep us informed of your results and if you can demonstrate a successful result I'm sure you'll have a winner to kit up. John
 
Maybe a 3/8" aluminum plate under DIS, with 1/4" diameter through-holes at 5/8" on center, parallel to direction of travel, with some tubular fins coming out of the through-holes, may air cool it a few degrees.
 
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I think the PC heatsink (either a standard or heat pipe type) would be the way to go - ones designed for the latest P4 and P4 Extreme processors would be best as these should be able to dissipate as much as 130 watts of thermal energy. Not sure how much heat the DIS generates, but you could probably fit two heat sinks on the bottom. Of course you still have to get cool air to the heat sinks, so ducting or careful placement would be needed.

I've thought about trying some ideas, but it's not very high on my priority list because in 12 years I've only had to replace the DIS once, and I don't even know if that was due to thermal issues...
 
Yeah, DIS.

Anyway, all you can do is try it. I look at the finned aluminum heat sinks used for simple power transistors inside switching power supplies and just feel like a flat plate may not have enough surface area.

I guess I don't worry too much about airflow, as it's pretty certain there is air flow over and around that area when the fan is running and when the car is driving. (noticed by all the crud that accumulates on the DIS)
 
I would like to be able to mount my DIS away from the motor.
I do not like all the wires around the top of the motor going
to it.looks bad to me.

Do you think if the DIS was mounted on the outside or inside
of a MP Cold air partition wall, with heat-sink.This would get
the DIS into a little cooler air.A air duck could be ran toward it
since this would place the DIS closer to the front of the car.
Or extened DIS wires so mounting can be done on the front
on the car,between radiator and cold air intake area.

I have a 1990SC .A DIS wire loom extention would be a nice
peice to fab and sell.A plug and play type wire loom to get
DIS out of the heat.This with a nice heatsink,plus bracket,
with mounting intructions.

Thanks RANDY
 
Thanks for the feedback. I have a better idea now after reading a talking to a few of you. My next step is to make a prototype and take heat readings. I will have to show some temp reduction of the DIS mounting surface.

Rich
 
What if I mount a new DIS module on top of the old one???Will that work, considering that I have enough space under the hood??? :rolleyes:
Also, can I use silver duct tape to keep both modules together??? :confused:
 
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