I see this argument a lot on the forums amd I can't for the life of me make sense of it from a heat transfer perspective, maybe someone can help me understand what im missing.

The radiator is in essence a heat sink with forced convective flow through the fins. For a given radiator set up the heat transferred from the radiator to the air depends on only two things, air velocity (and the associated Reynolds and prandtl numbers), and temperature differential between the radiator and the cooling air.

If you are pumping faster, the temperature drop across the radiator will be less, but the volume of coolant cooled will be greater, and since the radiator temperature will be increased on average, the heat transferred out of the system should be greater. This should result in more efficient cooling, and should continue to improve with increased flow with diminishing returns infinitely.

Can anyone poke any holes in this?

Spoken like a true engineer, even though you are the Purdue type. Go ND

All I know is if you poke holes in it the coolant runs out on to the floor!

The electric water pumps (EWP) can either be run by themselves or as a helper. When you do have an EWP you want to remove the thermostat as when the pump is not spinning it essentially wont let any water through if its running as a helper.


If you run a constant return coolant system (Like you should...) You can either bleed the system slowly by turning the key on and letting it cycle at low speed (I dont recommend), you can apply 12v to the pump and get most of the air out of the system, or you can start the car and just fill it up as it warms up (Recommend).



My recommendation is that for all 6cyls and below regardless of turbo should run no mechanical water pump unless your build requires you to be below 160deg temp all the time. However most modern engines are efficient up to 225deg this is not a concern.

For V8's especially SBC's I think they might need a high GPH water pump or to run a mechanical and electric pump.

I have been driving my 4cyl around in 90deg weather for about a month now and most of the time its cycling the water pump between slow speed pulses and full and I have it set to not go over 160deg for testing purposes which means that its not even working hard at all to maintain that. I rarely if ever see the fans turn on even putting around. The only time they come on is when the engine shuts off, the water pump and fans turn on until the system has cooled down to 140deg or 2-3mins later. This has an added benefit for me as it cycles the water for the turbo as well cooling it down. Again this is just for testing purposes and to make sure everything is circulating as I flog the turbo.

Back to the OP's original video which I watched saturday and forgot the comment. The car sounds great!! Loving that engine combo. I think that should be the new SBC swap as it just make so so much sense in this car.

Yeah, that forum argument has always bugged me too; it doesn't make any sense at all. Many people seem to think that increased residence time has some ability to increase energy transferred. That's true in stagnant systems since conduction comes into play, but really has no bearing in convection dominated systems.

"Too fast" flow is not a problem for heat exchange since higher than average coolant temperature across the radiator and higher flow rates always correlate to better heat transfer through increased exergy (available energy for transfer) and higher convection coefficients. The air side is really the limiting portion so there are diminishing returns to increasing water flow rate. Ideally there is some optimal flow rate which trades heat transfer effectiveness for pumping losses to reduce parasitic engine loads.



Coolant temperatures of 160F are really, really, low. Published studies by Caterpillar have shown engine wear at those temperatures to be very high. IMHO it's much better to be operating at the high end of the coolant temperature limit with a higher pressure radiator cap for safety.

This i know. The old issue with the small block chevy's was that if it started to creep up in temp and get over 200 then it just was never going to get back down. Thats why they would put 160deg thermostats on it and run the fans at 180deg.

I'm with you. Was wondering the same thing. Could higher volume place some air in the system? Or turbidity that impedes flow?

The video link isn't working for me though... The automatic plan is still up in the air but I'll pull some measurements off of cars at RRC here in a few weeks to make my final decision. I'd go with the Audi 6speed but I'm sure they're not giving away the adapters, flywheel, and clutch setups either! If I can get some reassurance that I'm not gonna blow up a Subaru 5 speed I'll probably go that way eventually but if the automatic fits, I'll use it for awhile just to prove it can be done!

Fixed the vid! The 5MT Subaru trans is a pretty nice setup for the $. Shifts very smooth. The clutch is light. I don't see how you could blow it up unless you miss gears a lot. I haven't even ground a gear yet!

Andrew thanks for the kudos. Yours is coming along great too. You built that engine right. It's running very cool. I like all the data you get from it.

Hey on the cavitation thing there are lots of threads on the Subaru-SVX.net forum. Apparently the coolant boils because it can't get through the pump fast enough in extreme conditions. Very high revs for prolonged periods. The flow just gets impeded despite the fact that the water pump is working well (too well). It's like traffic waiting around a curve. They even make a high flow water pump inlet with a larger midsection.

You are spot on in your engineering text book knowledge.

Issue is with the EG33 (maybe others)is that pump actually stops pumping as it creates suction cavitation. Once it cavities, it no longer pumps the coolant thus spiking temperatures in the engine. So I still think my design and understanding of the system is spot on.

Solutions increase inlet hose size 2" was the preferred size in testing. And remove the thermostat. My systems solves the cavitation issue by not being tied to engine RPM. And thus eliminates the need for a larger volume for the inlet hose. And with this system I am able to remove the thermostat as the pump controller will optimize the coolant movement based on temperature.

Other solutions, increase the pressure the system produces. Higher pressure cap. Change coolant to a none water based coolant might also work, but never tested that one.

It must be a know issue with Subaru pumps as killer B makes a modified water pump / thermostat housing to fix the issue. Or maybe to sell more product

So Stephen, the question is, do you also still run the stock pump with a piggybacked electric pump? Or did you figure out a way to gut the stock pump? Since it is driven off the timing belt, that pulley must remain in the loop.

Gut the pump, you just cut the impellers off the pump. I keep the pump face so the bearing still has a thrust to it, generalization of the process. We will see how well t works over the long haul.

Okay...since the stock pump works well and just needs more fluid at higher engine speeds, doesn't the electric pump only come on when needed? So in case the pusher pump fails (I know electric pumps NEVER fail...) you can still have the stock pump to get you through...?
And sorry for the hijack - this is an interesting subject and inquiring minds want to know!
Your build is always on my mind and I've already copied a bunch of your ideas and methods - the car sounds right on the money!

Easily

If the engine is adding 50F and the radiator is only cooling 30F because of the high flow then you get heat creep.
The stock water pump should be designed to deliver the best cooling and consistent temp for the engine concerning flow volume.

I don't know the subie well enough to discuss captivation theories and I didn't read back too many pages so that's all I got to offer today

It's not an airplane, if I started thinking like that, I would run it like a datacenter.

Twin EG33s

Hey Chris, I hope all is well in your corner of this mad world. So any updates? You mentioned talk of console fabrication... You've earned a rest from the posts with the last video but that was months ago! The autumn leaves are turning and make for lovely acceleration videos at golden hour.

Well I do have a few small updates. Haven't started on the interior yet. Been very busy lately but wanted to get the engine sorted before it was time to put it away.

Just wanted to go through the idle-affecting stuff one more time. First, I was able to get my intake to sit normally by slightly trimming the rubber snorkel part. I didn't document it but will post the pics from where I borrowed the idea. I DID NOT trim as much off as it shows in these pics. I cut about a mm beyond the stock thicker clamps. This person was converting a Vanagon, and apparently there is even less space there than a flipped-intake 914.

From The Samba site thread titled 3.3 Subaru SVX/Vanagon Syncro Conversion:

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Reminder my trim was not that drastic. See below for my pics.

Then I also shaved a little off the lip of the throttle body so that the snorkel would slide further on to it. Again, not my photo.

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Here's how it looks back on the car (finally my pics):

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Fits very well and the clamps are holding it tightly. No doubt there was some air getting in before with it twisted up on the passenger side like it was. I also found that the throttle position sensor was probably bad. I'll post a video of how to check that later tonight. Very easy.

Hey Chris, had a quick question - I just got a 2004 WRX trans for the build and I've been reading about the conversion to front wheel drive for mid-engine use. Is there any reason why after modding the center diff you couldn't just re-use the rear cover and block off the driveshaft hole? Or does a flat plate serve a purpose other than being lighter and 2.5" shorter? Thanks and happy holiday wishes!
-Christopher

Christopher,

Well, I'm not really an expert, but I suppose it's possible as long as all of the gears and stuff were removed from that end and you completely plugged the hole. It would require a lot more fluid.

Here's a pic of the removed parts:

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In the case of the 914 that extra few inches is pretty important. The trans would be very close if not touching the rear apron with that piece on. It's so easy to make a cover from an aluminum piece I'd recommend you do that. Always nice to save some room and weight if you can.

Plus the center diff is worth some cash on Ebay, so why not cash in and save some weight in the process?

I guess the question is why not use a block off plate? I just spec'd them out and am having a few cut if you want one.

^^^ Take Ross up this! I think you'll have more options for your cable mechanism with no tail on the trans too. Can't really visualize how it will fit in there.

I'm coming up with a solution on that front too!

Ok guys so (don't laugh too hard at me) but my question if more about aesthetics.

Anyway, the styling on the Lancia in the rear gives it a very exposed undercarriage and the bottom half of the rearend of the Subaru transaxle will be fairly visible. Ala Ferrari 288GTO:
https://goo.gl/images/QCPvKl
The flat plate is all flatty and plain but for the bolts whereas the stock rear cover has cool contours and structure. But if the drive shaft opening is cut flush with the rest of the structure and plugged it's ~2.5" inches longer than the plate. When I get the assembly located in the engine bay I'll decide then which way I'm going but I was initially curious about possibilities. If I'm showing the world what's under my skirt I'd like it to be interesting at least!

Also, I'm way too close to the beginning of this stuff but thanks for the offer Ross! I miss Colorado still, winters and all.

Here's a shot of the Scorpion for reference:


See the jacking point structure just left of center? The bottom of it is flush with the floor of the car and will be removed and replaced with Subie transaxle butt (centered between the suspension points though)

Subaru Gears

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Bremar

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Of course seeing these should give you the idea you can do hat ever you want. Machine a pattern in, weld some stuff on, or laser engrave a picture if you want. Sky is the limit here. Biggest issue is really space.

Of course the 288GTO is just
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Chris are these the ECU connecters at the engine side for a EG33?

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Merry Christmas

Yes they are Bob! I see you found that ECU too . I'll send you something for all that. You can't give everything away! Really appreciate you digging it all up.

BTW all Bob might be selling his flared orange car. He's putting a 6 speed Boxster trans in it first but it'll be ready next year. It has a 383 in it that runs perfectly. I'm kind of a wimp in the passenger seat but that one is a real neck snapper even with the 901 in it. The interior is tan with a neat high bolstered drivers seat. He is re-doing the flares with steel ones and then will paint it. If you get to him beforehand you can choose your own color. If I had the room I would have (tried to at least) bought it a while ago. Just throwing it out there early for anyone looking for a V8 car.

I'll have to see that one next time I'm out...

Maybe I'll be at home then. Retired last month

Hey Chris, or anyone with the Celica radiator,

I searched for pictures, but can't tell. Does the Celica radiator fit between the headlight buckets well enough that it could be slanted forward?

Sorry for the bump, but that's all for now.

-George

Yes. Mine is slanted forward.

I am not looking for a V8 car specifically, but I do want to own a 914 with a nice modern transmission swap. Why wouldn't you want the orange color it is now!

If it was built by Bob, I am sure it will be a great driver. Add a fuel injection kit to the 383 along with the Boxster trans will make for a reliable hotrod.

I said the same thing about the color. Not much better than a fresh coat of Signal Orange. It'll be nice car that you can drive anywhere.

Update...working on the "heater core in the fresh air box". First I had to take the wiper assembly out to lube it and change the rubber mounting bushings. Dang that thing is not fun to reinstall!

Here is the modified airbox.

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FYI the STOCK mid-90's mustang heater core is a little too thick to fit inside the fresh air box. I had to modify mine a bit. I'd go for the thinner aftermarket one if you're going to do this.

I'll have a bleeder valve on the higher line and a Rabbit open/close valve on the lower intake line.

So if you do this you will be eliminating the tube that comes up from the passenger compartment and connects to the heat/fresh air distribution system up front through this:

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You can seal them up with these 2" rubber plugs from the plumbing aisle at Home Depot:

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You also want to lock the flapper in the up position to keep any heat/fresh air from escaping or coming out the wrong area.

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Permanently lock this

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Now...couple of quick questions...

Does anyone know how the wires that connect to the fresh air box go back in to the connector they go in?

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Could someone look at their 914 and see which way their lower heater outlets under the dash are pointed? Does the wider opening point towards the middle of the car or towards the door?

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I just keep looking at this thing...the simplicity...why did I wait so long?

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Every wire is imprinted with the function.

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The EG33 ECU itself has 76 wires. There are also ~4 more that connect to other things. This harness has 36 wires, many of which won't even be used.

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BTW also could someone PLEASE look at the plug that is connected to his/her fresh air fan up front and tell me which wire goes in which slot here? It's the 4 connector power source for the fan. Thanks!

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I have LOTS of updates but need to prove they work before posting them. Will document the MS3 install as well.

Wow, making me jealous with that.... I've got about 60lbs of wiring in my car...

about time

I can check my 76 when I get home. Pm me so I don't forget!

When you take those out of the holder you think "of course I won't forget how these went..."

Hard to get to. Even after I removed the expansion chamber from the gas tank. Looks like I used Andy's camera.

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Perfect! Thank you Kent! Now I can test my heater. Have to finish the timing belt job on my wife's Volvo then I'm 100% finishing the 914 refresh.

what does that Mega squirt box do,..enhance the ECU or replace it..??? TIA Frank

Totally replaces it. Also eliminates many of the unneeded stuff like the EGR, complicated fuel pump/fuel delivery system, etc.

Very cool! So is there a MegaSquirt map already available for the EG33? What are you doing with that old harness?

Hi George,

There are maps on the msextra site. I have a crap-ton of wiring I can give you when I'm done. I'll also have an extra ECU I can pass on.

Hmm,..how much is that..?? if I can ask..

I picked up a used MS3 with the expansion boards and ignition modules needed to run the advanced came on the EZ36 for 750$ earlier this year.