Who passed thermodynamics 101?

Got 2 48-vane mesa oil coolers that I'll be mounting in front behind the grill (under the front bumper) of my `73 Super. I'm mounting in front due to all the free air flow at highway speed. As a backup, I should have fans.. But @ what airflow?

Hmm..

I was told a single 96-vane is a proper match to my engine. Due to the space up front, had to split to two 48s. The fan from BugPack that mounts on the 96 has an airflow of ~450 cubic feet per minute (educated guesstimate). Therefore I need two fans to equal 450 to get the same. But as these are the "back up system" for around town use, do I need that much? For 120mm fans, ratings seem to be around 90cfm. So that'd be 180; half the airflow. This seem OK?

As I find the case of all the fab work I do on the car, my first attempt I learn from, and usually get it right the second try :)

Reply to
David Gravereaux
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My only question is, why does the car need that extra cooling, and are you sure it even does?

Jan

Reply to
Jan Andersson
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"David Gravereaux"

You had better use insulated pipe otherwise the oil might be stone cold by the time it gets from the back to the front. In other words, !?!?!?

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Reply to
Poodles

Yeah, I'm sure. The engine builder said so. For all engines over 2 liters (mine is 2.27), the 96-vane is the recommended size.

Reply to
David Gravereaux

I doubt anybody's going to be able to tell you exactly how much fan power you need, etc. With all of the extra plumbing to run 2 separate coolers instead of one, the math isn't going to be exact. I mean you can't say you need X amount of airflow for a cooler of size A so you need X/2 amount of airflow for 2 coolers, each of size A/2. Just admit it. You're just making conversation. ;-)

Reply to
Shaggie

What are you using that is capable of pushing oil that fan and returning it without very low oil pressure. I'm very reluctant to have a cooler more than a few feet from a heavy duty pump.

Reply to
Wolfgang

Not true. I over-think things and like it that way. I don't like screwing up. It would be nice if I could at least attempt the math like the way you can with heatsinks for power supplies, but not knowing any of the characteristics of the cooler, I can't given what I don't know.

Last time I over-thought the throttle arm geometry, I actually fixed it for good. So pooie on youie :P

was:

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That attempt made the feel much worse (ie. inverse proportional) is:
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I cut that grooved wheel on a lathe after solving for its radius. You know.. central angle (theta) equals length (s) over radians (r) Math is your friend. Physics is reality.

Guess I'll choose "some" whatever fan as something is better than nothing for the in-town / stop and go use. If I find oil temps rise and the fans are locked on, then they're too small.. Good enough.. At least I tried to solve for it before purchasing something which is probably the best I can do.. Unfortunately.

Reply to
David Gravereaux

You should have got nickelsil cylinders.

Reply to
jjs

send me a check for $2500 and I'll be glad to add them :)

Reply to
David Gravereaux

It's called a "thermal bypass" near the engine @ the remote filter. Hot oil is easy to push and hot oil is the only oil I want to cool.

Reply to
David Gravereaux

David,

at idle or putting around town, in fact any time you drive like you used to drive a stock engine (using same acceleration rate and speed, i.e. using the same amount of horsepower), you are not producing any excess heat. If the engine was built correctly, you will not overheat, unless the circumstances were such that you'd also cook a stock engine.

For example, cruising down the highway at 55mph uses roughly 30hp, no more. If that's what you use, then the energy (heat) produced by the burn process stays the same. Maybe even less, because you have a new, tight engine that burns everything more efficiently than an old, worn engine would.

This is why I ask you why do you think you need extra coolers for. Don't put them there unless you have proof that you need them, and even then only AFTER you have made sure the engine was built right. Any extra oil cooling you have will only help you HIDE an overheated part of the engine. The reason for the extra heat may be something that needs to be fixeed ASAP, not just hidden out of sight by increasing oil cooling and measuring the now cooled oil temperature. fralse sense of security that might bite you in the ass some day...

Jan

Reply to
Jan Andersson

Reply to
ilambert

The engine was not damaged in the fire. It's just got some ungodly backfiring issue at idle (only) and has since day one. I noticed it, of course, but it was stiffled by the dual quiet packs. When I went to serpentine pipes off the end of the header to dump in front of the rear wheels (kept the header as-was), it was so loud it sounded like gunfire. Literally. I wonder if one of the carbs is pouring gas down the pipe. But I'm slimming down the 'stuff' I have, and can't take this car with me.

Reply to
jjs

44 IDFs? I had a similar prob. Take off the choke blocking plate and inspect the position of the sliders. Both slots need to be in the down position. I couldn't figure out my rough running prob either until I went to add the "enrichment assembly" and found the culprit. One of the sliders was stuck at the top.

I hope it's that simple..

Reply to
David Gravereaux

Ok, now someone is talking to me :)

Agreed on all counts, especially the last. My old worn motor prior to this new one had a bearing problem and wouldn't hold any (4psi) pressure when warm and all I could do was 30 minutes of highway driving before I had to pull over and let it cool down from 260 before continuing.

But that engine is gone.

I'm good on that respect as I have about 600 miles on the motor now and the temporary position the oil cooler was on the rear deck:

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Is a great cabin heater when the fan kicks in :) From dead cold, it takes about 20 minutes of highway cruising before 180 is reached and the fan kicks in. Given that there is only marginal heat dissipation from no air flow, I'll surmise that equal area from two 48s behind the grill at highway speed should do great. If its hot out (around 90), the fan stays locked on for the highway, temp never rose over 190, and was awfully uncomfortable in the car for noise (full open windows) and temperature :(

Mr. Raby says to use a 96vane with the engines he builds over 2 liters. I don't question his experience.

Jan, I completely understand your position given a stock motor and your claim for equal HP (thus heat) at nominal cruising for engines of equal "health". Jake says to use a 96 and I'm not going to argue that and two

48s equal a 96, done. Heat wrap tape on the headers will happen, and so will getting the sealing tin all in. Granted the monstrous added amount of air flow found at the front grill at speed compared to a cooler mounted up around the transaxle should be considerable. So in a way I guess from the greater flow aspect I could make the cooler area smaller, but don't know if that would be a safe assumption.

To reel this back, say I'm barreling down I-5 in the central valley like a crazy loon passing ricers and decide to exit for gas. Now while I'm waiting for the light at the end of the exit ramp, and no air flow is going across the coolers, what's a decent CFM rate I want on the fans given that the motor is 160hp and I was using "some" of it?

The Mouser catalog ranges 120mm ones from 50 to 200CFM. Given that Jake recommended a 96, I'll assume with the 450CFM fan, but as most of the airflow I get for free from the front placement, the fans will only be a backup.

Screw it all... I'll get 2 100s and see if I don't dislike them after a highway blast in stop and go on freakin' hot day. Good enough..

Reply to
David Gravereaux

Yikes! :D

Don't look at me, I don't know :) I can't afford to drive like that, our speeding fines are too big for anyone with ahlf a decent salary... (Progressive fines, the more you earn, the more you pay.. the fines are a percentage of your salary or something)

Jan

Reply to
Jan Andersson

Dual fan mounting idea with shorter oil lines/ more oil pressure. If you get one of those aluminum or stainless drag wings, which you would need for the aerodynamics over 100mph. You could cut two 8-10 inch holes in it and mount the oil coolers underneath the wing. Similar to a Porsche 911. Something I had already thought of if I had the means.

Reply to
Zarana-X

Ohh, yeah carerra style. Neet idea. I've only seen bugs like that in pictures.

Reply to
David Gravereaux

Goodyear blue hose inside firebraid running inside the tunnel. As the thermal bypass

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't allow flow thru the long lines when the temp of the oil is cold, I'mnot too concerned about that.

Reply to
David Gravereaux

....

Oh I'm not saying I would. I'm just trying to perceive the limits I expect the car operate under. Oh, and there's pulling a 2500lbs trailer going up the famous 18 mile climb we Californians call the "grapevine" (Tejon Pass) crossing the hills into LA. And doing 65 the whole way. Ok, granted I don't have the rear frame (or lack thereof) reinforced with a hitch yet, but that's a goal in the future.

I decided on this model:

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-> SPA03017 CFM seems a bit high @ 252 from my guesstimate, so I'll try them first in series and swap to parallel if they don't cut it. Maybe mount a speed switch on the dash..

Reply to
David Gravereaux

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