Mounted a heatsink under the distributor
Printed From: West Coast Fieros
Category: Technical Topics Forum
Forum Name: Technical Questions and Discussions
Forum Description: Got a technical question about your fiero? ask it here.
URL: http://www.westcoastfieros.com/forum/forum_posts.asp?TID=949
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Topic: Mounted a heatsink under the distributor
Posted By: Patrick
Subject: Mounted a heatsink under the distributor
Date Posted: 27 October 2008 at 1:08am
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As reported http://www.westcoastfieros.com/forum/forum_posts.asp?TID=942&PN=1 - Here , I was recently stranded with a cooked ignition module. Not wanting to go through this process again, I searched the PFF archives for ways of cooling down the ignition module on my '86 GT. Although I found posts from PFF members talking about the possiblility of using heatsinks mounted on the underside of the distributor, I was surprised that I didn't actually find any posts by someone who had done it. I obviously then wasn't able to find any pictures of a modified distributor to see how it might've been accomplished. So I did it my way. I used a heatsink from some ancient CPU that was about the right size for the job. Longer cooling fins might've been better, but you gotta use what you have on hand. I ground down all bumps on either side of the distributor base, and drilled large enough holes for machine screws to pass through. I then drilled and tapped the heatsink to accept the four screws, two of which go through the ignition module as well. Thermal paste was applied to the underside of the ignition module as well as to the topside of the heatsink. The way I assembled everything, the ignition module can still be changed with the distributor in the engine. Hoping I won't have to do it again though. Yes, the screws look goofy sticking down so far, but I figure the more surface area the better for cooling. They won't even be noticeable once the distributor is installed. If you have any questions, I'd be pleased to answer them.
I noticed afterwards how much the camera flash shows up the ground aluminum dust on the heatsink in some of the shots! |
Replies:
Posted By: marcelvdgn
Date Posted: 27 October 2008 at 8:11pm
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Patrick i really like what youve done i have a box of old cpu chips heatsinks somewhere goin to find them and rebuild a spare distributor Marcel ------------- Marcel 86SE V6 Auto 85SE V6 Auto 85 2m4 soon to be sleeper 3.8sc 5 speed |
Posted By: Patrick
Date Posted: 27 October 2008 at 11:17pm
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Thanks Marcel. This is something I've wanted to do with the GT ever since I bought it earlier in the year. I know the reputation the V6 has for eating ignition modules in Fieros, so I'm hoping this will extend the module's lifespan. Can't hurt! And here she is all buttoned up, ready for AirCare tomorrow.
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Posted By: Capt Fiero
Date Posted: 28 October 2008 at 11:41am
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I have been meaning to post these for months. Here is the one that I have, its pretty much the same principal as what you have done. The dist shaft is completely rebuilt and polished on my wire wheel to make it nice and shiny. I did not install the heat sink, an ex club member that worked for Air Canada did the work in a machine shop using a mill. I just did the finishing touches to it blending the seems and stuff.
I am really tempted to go one step further and wire up a small 4cm computer fan to the heat sink, and power it via the 12v lead from the ignition system. Not sure if it would do a darn thing, but is an idea. 
 ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: Patrick
Date Posted: 28 October 2008 at 5:04pm
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That looks really nice Dave, much more "refined" than mine. Oh, how I wish I had a shop and proper tools to play with! I fabricated mine with nothing more than a handheld electic drill out in the carport.
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Capt Fiero wrote:
Posted By: Dr.Fiero
Date Posted: 28 October 2008 at 5:07pm
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I wasn't going to open up this can of worms, but... WTF. :D Remember that a heat sink works both ways. It can displace heat - it can also absorb it! If the heat in the engine bay (or at least the air pocket right there beside the toasty exhaust manifold) gets hotter than the ignition module, you will start to drive heat INTO the module instead of pulling it out! This would be a good reason for a fan (remember the factory one that almost everyone pulled out on the early V6 cars?). It'll have to be a pretty robust one though, or you'll be swapping them out monthly. I still like the idea of extending the pickup wires, and mounting the module onto a heatsink/fan and stuffing it into the trunk. |
Posted By: Patrick
Date Posted: 28 October 2008 at 5:27pm
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All valid points John, but... GM wouldn't have mounted the ignition module on the aluminum base of the distributor if the heat in the engine compartment was hotter than the module. They put it there for a particular reason - to dissipate heat from the module out through the bottom of the distributor. Otherwise they would’ve insulated the module instead. In essence, the aluminum base of the distributor is a simple heatsink. I combed through the archives at PFF about this before I tried my little experiment. I came across at least one post which stated that the ignition module gets VERY hot, much hotter than the ambient temperature under a Fiero's decklid. Of course, it certainly doesn't hurt to have the EGR tube blocked off or removed or well insulated to reduce heat in that particular area. |
Posted By: Capt Fiero
Date Posted: 23 November 2009 at 11:29am
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Well this is a good time to bring this thread back to life. Its been a year for me, and I am thinking about the same for you Patrick. Have you burned up an ignition module yet? If the heat sink was drawing IN heat from the exhaust and causing early failure, our modules should have failed by now. I installed mine with a used module and still no failure, how bout yours? Heck my dist is now running in a 2nd motor as a test mule and still no issues. ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: Patrick
Date Posted: 23 November 2009 at 11:32am
No Dave, it's been just over a year and there have been no problems at all. I've been very pleased with the modification. I should add that eight months ago I reinstalled my EGR tube and therefore added a bit more heat to the distributor area. My ignition module and I survived the hot summer months unscathed.
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Posted By: Capt Fiero
Date Posted: 23 November 2009 at 11:23pm
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We'll we will see if Damien finds a way to mass produce the heat sink distributors and if not, I'll start adapting them to all the ones at the house. If it saves me even one trip out to go and rescue, Lisa, Shirley or Tim broke down at the side of the road, it'll be worth it enough for me. At $100 per module, and costs in fuel, several times a year. (combined for all the cars) I think a new type dist might be looking like a great idea. ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: Romeo
Date Posted: 24 November 2009 at 12:06pm
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Has anyone also considered using a liquid cooling system? Might help matters as well, I know that's what people do to computers and electrical circuits when they want them very, very cold. ------------- Never shift into reverse without a back-up plan. |
Posted By: Patrick
Date Posted: 24 November 2009 at 5:50pm
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Great idea, Tristan! We'll run some long wires and screw the ignition module to the radiator. Actually, after thinking about it for a minute... How about some kind of metal mount for the ignition module that attaches in some manner to the metal coolant return pipe near the passenger side of the engine? The coolant coming back from the radiator is probably no more than 200 F (probably a lot less), and this would be a whole lot cooler than the extreme localized heat that the module itself produces. Hmmmm, the wheels are turning...
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Posted By: Car-2-Lo
Date Posted: 24 November 2009 at 6:23pm
That's so gnarley ! 
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Posted By: Capt Fiero
Date Posted: 24 November 2009 at 7:33pm
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I think what you guys are looking for called a "water block" its what the home water cooling CPU kits use. It has a flat metal surface for attaching to your CPU and then 2 hoses come off of it to your computers radiator and water pump. (yes some computers have radiators and water pumps) I thought about installing a kit like that in my large server tower. The main reason for home kits is not for extreme cooling, but no fans means no noise and the better water pumps are silent. So your computer is silent. I really don't think we need to go to the extent of using our cars cooling system to cool our ignition modules though. It might work and function, however with so much extra stuff needing to be added and hooked up, I honestly don't think it would be worth it in the long run.
http://www.dangerden.com/store/new-products.php - http://www.dangerden.com/store/new-products.php ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: Patrick
Date Posted: 24 November 2009 at 8:27pm
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We probably don't need to go to the extent of putting V8s in Fieros either, but does that stop everyone? Dave, if it hasn't already been done, someone someday will try using their car's cooling system to cool their ignition module. It's such a crazy idea it might just work!
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Posted By: CFoss
Date Posted: 24 November 2009 at 9:07pm
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Yeah, guys, the cooling water idea wouldn't work. The p-n junction of the transistors which are trying to dissipate power would have to get way hotter than the 200F starting point...poof. Now, a nice liquid hydrogen cooled substrate...now you're talking! Dr. Fiero makes a good point...time to read up on black body radiation basics again! The transistor junction temperature is linked to the ambient through a 'thermal impedance' which takes into account all the things like junction to case, case to heat sink, heat sink to ambient impedance values. By adding the improved heat sink you've lowered the heat sink to ambient impedance. Given that we think of the air around the dist as cooler than the ignition module there should be a modest improvement in transistor junction temperature, given a constant thermal output from the module. I think it probably produces less heat at low rpm (Less switching), but not that much less. Worth a try though eh? Chay ------------- 86 SE 3.4 |
Posted By: Patrick
Date Posted: 24 November 2009 at 9:33pm
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That's so gnarley! (Sorry, Tristan and John forced me to say that.)
So Chay, how does that differ from the module sitting on the base of the distributor (with or without an added heat sink)? Wouldn't "heat soak" from the hot air under the decklid do the same thing, especially if the engine is restarted shortly after being turned off on a hot summer's day?
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Posted By: Dawg
Date Posted: 24 November 2009 at 10:52pm
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Hmmmm....All this seems a little overboard.....:) Oh I know....a Peltier Junction would be simple and would work. But still overkill.... Google it, you'll like it. DG ------------- You dream it up....I'll make it |
Posted By: marcelvdgn
Date Posted: 24 November 2009 at 11:30pm
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buy or scroung an old working portable 12volt coleman cooler/heater and tear it apart. Has all you need including the circuitry, heat sink and the peltier exchanger. plug it into your lighter and your good to go M
------------- Marcel 86SE V6 Auto 85SE V6 Auto 85 2m4 soon to be sleeper 3.8sc 5 speed |
Posted By: Romeo
Date Posted: 25 November 2009 at 12:01pm
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Oh, I see what you did there... But yeah Patty, I think you've probably seen what I mean, liquid cooling systems, even very tiny ones, are often regarded as superior to heatsinks. ------------- Never shift into reverse without a back-up plan. |
Posted By: Romeo
Date Posted: 25 November 2009 at 12:04pm
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Shouldn't keeping ANY of the electrical circuits in the car produce more power? Remember, the key to superconductivity is cold. That's why the Large Hadron Collider can generate over 10,000,000,000eV, because they keep all the circuits close to absolute zero, making them literally more than ten times as effecient as if they simply focused exclusively on voltage. ------------- Never shift into reverse without a back-up plan. |
Posted By: Patrick
Date Posted: 25 November 2009 at 12:11pm
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??? Was anyone suggesting we should be "keeping ANY of the electrical circuits" outside of the car?
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Posted By: Matt
Date Posted: 25 November 2009 at 1:15pm
Hmmm maybe that's why I find those females "superconductive." ------------- I wanna go fast. |
Posted By: Romeo
Date Posted: 25 November 2009 at 5:06pm
Oops, after car, there should be the word "cooler".
And Matt, you're my hero. lol ------------- Never shift into reverse without a back-up plan. |
Posted By: Patrick
Date Posted: 25 November 2009 at 7:03pm
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Matt is your "hero" because the women he meets are "cold"? Geez, how much fun can they be?
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Posted By: Patrick
Date Posted: 25 November 2009 at 7:13pm
Ummm, you want it to read like this... "Shouldn't keeping ANY of the electrical circuits in the car cooler produce more power?" Let's get this straight... You want to be packing electrical circuits around in your car cooler to produce more power?
Tristan, are the drugs there more potent than here in BC or what?
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Posted By: Matt
Date Posted: 25 November 2009 at 9:40pm
Tones of fun! Don't you like a challenge? ------------- I wanna go fast. |
Posted By: CFoss
Date Posted: 25 November 2009 at 10:00pm
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Patrick, the water idea doesn't work because the ambient becomes the 200f water. The normal air ambient/dist base has to be way less than that. It's analagous to a dc electric circuit, where the 'common' is the ambient temp, the 'positive' is the transistor junction temp, the current is the powerflow and there are thermal impedances, which resemble resistors. A good description on the electronics analogy: http://en.wikipedia.org/wiki/Thermal_resistance_in_electroni cs If you research it, junction temps are considered very high (unreliable, no kidding) at the 200 deg mark. Chay ------------- 86 SE 3.4 |
Posted By: Patrick
Date Posted: 25 November 2009 at 10:16pm
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Chay, keep in mind I pulled that number out of the air, or should I say water?
Geez, I dunno about that. Do you really think the air temperature around the base of the distributor is less than say... 150F on a hot summer day after the engine has been brought up to temperature while running a 195F thermostat? No doubt you know a hundred (maybe a thousand?) times more about electronics than me, but I'm not so sure my question below was completely off the mark.
What would be interesting to find out though, is just what the temperature at the base of the distributor stabilizes at while the car is being driven. If that temperature is consistantly lower than whatever the temperature is of the returning coolant, then yes, I'd agree that having the ignition module cooled by engine coolant would be completely impractical.
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Posted By: Patrick
Date Posted: 25 November 2009 at 11:16pm
I'm getting too old for challenges. I want immediate gratification!
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Posted By: CFoss
Date Posted: 26 November 2009 at 10:19am
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It's all speculation, like you said. But when I engineer something I look at the best and worst case scenario...say the car overheats...then where does your cooling scheme go...I'd hate to overheat AND lose the ig module in 1 go! I really don't think the ambient around the dist base is that hot. The reason is that air moves. When it heats up it convects, lowering the temp again, and so on. It's not really captive in there, it's sorta captive. The heat transfer from the ex man. is radiant, not convective, so if we radiant shielded the ex manifold (Ie: a piece of sheet metal) on the dist side, then added the heat sink, the solution is pretty good.
Chay ------------- 86 SE 3.4 |
Posted By: Patrick
Date Posted: 26 November 2009 at 10:33am
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Of course, it's all speculation and conjecture, but it makes for interesting discussion nevertheless. Thanks Chay!
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Posted By: ARTIC-1
Date Posted: 26 November 2009 at 7:54pm
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Wow ive looked at most of this thread an have come to the conclusion
that theres a prob with HEAT in the ignition module pick up.a lot of good ideas here,an technical analysis! trobbl is i understand all of it. the good Capt Fiero had the right idea with moveing it to a differnt local where theres not as much heat.an Patrick an Dawg with mounting a heat sink under is a quick inexpensive way to do it to.myself iam going to use a vary unique remote sodium heat sink from a computer,no power required.it uses Thermal conductivity to move the heat away an if you add induction in there,mount it closer to the Exhost,it will pull heat from the cooler point,ignition module.in theory this should work,has yet to be tested? W/m-k. m2/s.  ------------- SNOW MAN 87-GT/AUTO-2.8_ WHITE 88-TTop/ Duke-2.5. RED |