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PostPosted: Fri May 25, 2018 11:46 am 
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Thanks J !


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PostPosted: Fri May 25, 2018 11:52 pm 
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DonCichocki wrote:
How about someone making an oil cooler with a built-in thermostat for those of us who drive in cooler climates where the oil barely gets up to operating temperature. [...]

I've got several schemes to do this in the folder. Some look like they'd work, but there are some problems:
1) You, me and two other folks are concerned about engines running too cold. Well, maybe five other folks.
2) I have yet to devise a "fail-open" design, which means I have to convince all buyers that my design is better than the one the factory gave up on, and which won't leave them with an overheated engine if it does fail.
3) And then, (as I'm sure John can attest) producing even the one which do not have this feature is a major up-front expense if you want a quantity price that will sell at an acceptable retail price.
Which leads to the last problem:
4) I don't want to own and warehouse several hundred very cleverly designed coolers which will get sold for scrap when they plug me in the ground.

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PostPosted: Sat May 26, 2018 7:04 am 
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I understand, thanks Ron.


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PostPosted: Mon Jun 04, 2018 3:03 pm 
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Which one of you engineers out there can explain the theory that indisputably proves that the various aluminum oil coolers are more efficient than the original coolers? I took apart an engine today with this cooler and my marginal brain took notice of the number of rows that Porsche used, eight. That is eight and space for airflow to either side of the cooler. So does the steel allow the tubes to be thinner and still resist cracking? Does the superior heat transfer of aluminum fully compensate for the fewer rows that the aluminum coolers have? Was Porsche unaware of aluminum when they were revising the oil cooler design? When they tried to fix the cracking at the cooler mount why didn't they change to aluminum? I'm starting to wonder if some real testing isn't in order.
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PostPosted: Mon Jun 04, 2018 4:09 pm 
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Good questions.
I have always thought that many of the "improvements" sold in the air Cooled world are based on theory and not fact.
I do know that in 1971 VW introduced an aluminum cooler that was wider than the old steel ones and was offset in what VW guys call "the doghouse." Porsche/VW used a similar cooler in the Type 4 engines used in buses and 914s. This would indicate some advantage to aluminum since they could have kept the cooler steel and offset, right?

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PostPosted: Tue Jun 05, 2018 7:16 am 
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Just to stir the pot...
Quote:
Start with the Chart

Setrab USA has gone to the trouble of providing us with a very handy oil cooler application chart (PDF format) that gives us a starting point without having to do math. The chart covers engine oil coolers, transmission coolers, and even power steering and valve spring coolers. Note that the chart is arranged by part number, not by application. Browse the chart a bit and you'll see that most applications are listed under more than one cooler size.

Oil Flow Restriction and Cooling Performance: Rules of Thumb

Here are some broad, oversimplified, very general principles to keep in mind when choosing a cooler. Remember that all of these imply "all other variables being equal."

Oil coolers introduce a flow restriction. Our goal is to minimize this restriction.
There is a direct relationship between plate length and restriction.
Longer plates (rows) = more restriction.
Shorter plates (rows) = less restriction.
There is a direct relationship between plate length and cooling effect.
Longer plates (rows) = more cooling.
Shorter plates (rows) = less cooling.
There is an inverse relationship between the number of plates and restriction.
More plates (rows) = less restriction.
Fewer plates (rows) = more restriction.
There is a direct relationship between the number of plates and cooling effect.
More plates (rows) = more cooling.
Fewer plates (rows) = less cooling.
Two coolers with similar cooling area will have similar cooling performance.
In the list above, the only apparent conflict we have to wrestle with is in plate length. Longer plates cool better (good), but at the expense of flow (bad). Fortunately, the last point in the list above suggests a good workaround: We can choose a shorter cooler to regain some of the lost flow, and simply add more rows to regain some of the lost cooling. Even better, adding more rows simultaneously improves flow even further.

Let's take an example from the Setrab application chart and do just a little math. Say we have a high-performance engine putting out about 325 HP. The chart suggests at least three possibilities: Series 9 with 20 rows, Series 6 with 25 rows, or Series 1 with 50 rows. All three of these coolers have an effective cooling area right around 75 square inches, so their cooling performance is similar.

But the Series 9 will have the most flow restriction (longest rows x fewest rows), and the Series 1 will have the least restriction (shortest rows x most rows). As it turns out, the 25-row Series 6 will have about half the pressure drop of the 20-row Series 9, and the 50-row Series 1 will have roughly 1/10th the pressure drop of the Series 9!

Using real numbers, with a 10 GPM flow rate as an example (not uncommon for an engine running 6000 - 8000 RPM), the 20-row Series 9 will introduce a 5 psi pressure drop from inlet to outlet. (Note that a single 90 degree fitting in your oil line could cause more restriction than that.) The 25-row Series 6 will cause a 2.6 psi drop. The Series 1 will show less than a 1 psi pressure drop. The flow restriction from the Series 1 option may not even register on your oil pressure gauge.

Installation Factors

There are just two general rules when it comes to mounting the cooler. (Remember, "all other variables being equal.")

Oil coolers require airflow to take heat away. More airflow is better.
Cooling depends on the difference in temperature between the air and the oil. Cooler air cools better than warmer air.
The airflow equation is a little complicated. As airflow velocity increases, the additional benefit decreases (the graph begins to flatten around 40 mph). The important takeaway is that your oil cooler needs to be exposed to airflow. The largest oil cooler will be ineffective if it's sealed in the trunk or mounted flat up against the firewall. Air must be able to get into the cooler, and it must be able to get out of the cooler. This is what carries away the heat.

In many cars, this suggests mounting the cooler near the radiator. After all, Detroit / Stuttgart / Tokyo spent a lot of time and effort to locate the water radiator where it would get the best airflow. It seems like a no-brainer to follow their lead. But that leads to the second point above.

Air temperature has a direct effect on oil cooler efficiency. Hot air does not cool as well as cool air. This is why we turn on the AC when we're hot, and not the heater. Mounting the oil cooler behind the radiator can reduce the efficiency of the cooler by as much as half. A better solution would be to mount the cooler in front of the radiator. The trade-off is that the efficiency of the radiator will be affected by the air coming through the cooler, but the effect should be much smaller because the cooler is typically smaller than the radiator. An even better option would be to mount the cooler next to the radiator (assuming there is room) or below the radiator (if it can be protected from damage).

The air temperature difference also means that if we run two oil coolers, they should be plumbed in parallel, rather than in series. If you run two coolers in series, the oil in the second cooler would be cooler (closer to the air temperature) than the oil in the first cooler, making it much less efficient. Another bonus to plumbing in parallel is that it has the same effect as adding more rows to the cooler: Less flow restriction for an even happier oil system.

Much more information about mounting oil coolers for maximum air flow with minimum drag can be found in Chapter Nine of Tune To Win by Carroll Smith.


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PostPosted: Tue Jun 05, 2018 9:11 am 
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C J Murray wrote:
So does the steel allow the tubes to be thinner and still resist cracking? Does the superior heat transfer of aluminum fully compensate for the fewer rows that the aluminum coolers have?
Just to stir the pot...
Quote:
Start with the Chart

CJ, I think you've basically answered your own questions with that Setrab info. I can add that aluminum transfers heat about 4x more efficiently than steel. At the same time aluminum expands about twice as much as steel for a given temperature change. That would explain the need for thicker aluminum to keep it from cracking. Otherwise, per the Setrab chart, it comes down to overall surface area, airflow outside and oil flow inside. Less rows of aluminum tubes/plates still provide adequate surface area for the required heat transfer. The plate spacing affects airflow speed, the thickness of the overall (hollow) plate affects oil flow speed inside the plate and both of these contribute to the amount of heat transfer. So you have two fluids, each with different heat transfer coefficients, oil and air, the speed of those fluids moving across the surfaces determined by the oil pump (inside surface) and the fan speeds (outside surface) and the material between the fluids, aluminum or steel with their different coefficients of heat transfer. All of these factors contribute to defining the overall heat transfer coefficient of the cooler as a 'system'. And you can't beat John Wilhoit's empirical testing to confirm all of this as applied to the 356!

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PostPosted: Tue Jun 05, 2018 9:50 am 
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The info jibes with what VW did with the offset cooler. It is wider, more rows, yet shorter than the steel ones.
Of course the idea world would be having the ability to use the VW aluminum cooler, which is like $50 or so new, with the offset. The problem is the offset requires the doghouse which would interfere with the accelerator linkage set up.

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PostPosted: Tue Jun 05, 2018 12:26 pm 
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Hi Mark
If i understand what is going on here i would think that the 4 row cooler that John previously offered was a better design. The predicted performance results were skewed to infer a better performance to justify the available core since the availability of the 4 row cores was unfortunately lacking.
j

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PostPosted: Wed Jun 06, 2018 7:44 am 
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Jacques Lefriant wrote:
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Hi Mark
If i understand what is going on here i would think that the 4 row cooler that John previously offered was a better design. The predicted performance results were skewed to infer a better performance to justify the available core since the availability of the 4 row cores was unfortunately lacking.
j

Jacques, I am not sure what you want to know here. It sounds like John's 5-row cooler tested more efficiently than his previous 4-row cooler. There's more to it all than just the difference in the number of rows. But what are the 'skewed performance results' you refer to? 'Predicted' or 'inferred' results only occur on paper and only act as a comparison point against actual test results. If that's how I read your comment... :?

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PostPosted: Wed Jun 06, 2018 11:49 am 
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Hi Mark
there are quite a few Aluminum coolers out there. in my opinion the best source is Aero Classics/ Pacific Cooler they do aircraft parts that meet all the regulations. The 4 row cooler that Wilhoit seems to reference is one of the VP specified exclusive coolers. the comparison from Bell Intercoolers that was offered by John was a predicted not based on actual data. the air flow was based on 60mph vehicle speed and even given that the 4 row would have greater air flow it with the same air flow generated an increased exit temperature thereby removing more BTU if you do the math. Yes you could do testing and one may be better in an specific senario. Besides that the addition of another row was not elegantly accomplished and i would call it a 4 1/2 row cooler with reduced air flow.
j

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PostPosted: Wed Jun 06, 2018 12:49 pm 
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Jacques Lefriant wrote:
Hi Mark
there are quite a few Aluminum coolers out there. in my opinion the best source is Aero Classics/ Pacific Cooler they do aircraft parts that meet all the regulations. The 4 row cooler that Wilhoit seems to reference is one of the VP specified exclusive coolers. the comparison from Bell Intercoolers that was offered by John was a predicted not based on actual data. the air flow was based on 60mph vehicle speed and even given that the 4 row would have greater air flow it with the same air flow generated an increased exit temperature thereby removing more BTU if you do the math. Yes you could do testing and one may be better in an specific senario. Besides that the addition of another row was not elegantly accomplished and i would call it a 4 1/2 row cooler with reduced air flow.
j

Hi Jacques,thanks for the clarification, I wasn't fully informed of the background info here. I went to John's website but didn't find test results as he mentions in the beginning of this topic. Actually, going from 4 to 5 rows is a 25% change. It is somewhat misleading and maybe an over-simplification to base the claimed 20% improvement only on the difference in row quantities. This might be 'sales-speak' that, in the interest of simplification 'dumbs down' the technical info and doesn't address the many other factors (temperatures, row spacing, surface conditions, surface areas, viscosities, fluid speeds etc.) involved. It sounds like you are challenging the 20% improvement claim because the cooler is only effectively going from 4 to 4 1/2 rows? I would need to know more on that too because it is only a 12 1/2% change based on row numbers only.

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PostPosted: Wed Jun 06, 2018 12:54 pm 
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Tell us how you really feel Jacques!

Seriously, does the 5 row with oil weigh more than the 4 row and how much more oil (weight) does it hold?

Does it have an effect on side benefit of less weight on the oil cooler case mount?

Michael Foster

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PostPosted: Wed Jun 06, 2018 1:23 pm 
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Hi Michael
you really don't want to know what i feel. It is not a perfect world. i would like to have everyone enjoy their hobby and if you monetarily benefit so much the better. i have a problem with some vendors that are what i consider only in for the cash return or are so completely clueless that they are dangerous. unfortunately for the registry we no longer have Alan or jack Skags to keep us honest. Also while i am ranting the prices for some items in the classifieds are outrageous for items that Adam or i would be happy for someone to benefit from if they hauled it away for their own use.
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PostPosted: Wed Jun 06, 2018 2:20 pm 
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