Rear Mounted Oil Cooler

[Locobob]

Been kicking around moving the engine oil cooler to the rear frame rail so I thought I'd throw the idea out of comments and input. I would be using a custom/universal oil cooler, probably something like a 10"x10" and hanging it off the rear frame rail next to my relocated battery box which is already there hanging off the right side of that crossmember right behind the rear end.


Pros:
10lbs ish of weight off the front end for better weight distribution
Declutters the radiator area for better cooling
Mounted next to my battery box it'll make a nice mounting surface
for the rear diffuser I plan to make.


Cons:
Probably add 3-4 pounds of hose using light weight hose, might be
mitigated somewhat by size of cooler
Hose routing will be a bit challenging, I'd probably go
through/behind pass side lower body panel
Pressure drop?
Road debris? differential/exhaust should protect it pretty well
Effectiveness? I would just rely on under car airflow, I think it
would be good enough considering how little the oil cooler
actually gets used - pretty much track only.


Thoughts???

[Dynomite]

It is not so simple as a rear mounted battery installation with a limited voltage drop to contend with.

With oil and some 10 ft of hose (actually twice that with return line) you will have a lot of head loss and not much oil flow albiet the hose itself will cool significant oil. By the time the oil goes 10 ft the oil temperature will have dropped such that the cooler will not be very effective in cooling that already relatively cool oil.

See Item #3...……...Oil Filter Adapter Functions (http://www.zr1.net/forum/showthread.php?p=194213)

My vote is NO...…..:handshak:

[secondchance]

Personally, I think too many cons to contend with for 10 lbs and better cooling. Keeping it simple would be my preference. Introducing 20’ long rubber hose makes me feel uneasy not to mention possible oil pressure drop which will make me feel real uneasy.
I am seriously considering Spal fan conversion to beef up cooling although worst I have seen since Dewitt dual row radiator was around 218 in 98 degree day in stop and go traffic. Spal fans may add weight but not by much.

[Dynomite]

I am seriously considering Spal fan conversion to beef up cooling although worst I have seen since Dewitt dual row radiator was around 218 in 98 degree day in stop and go traffic. Spal fans may add weight but not by much.

I am considering an experiment using Spal Fan motors and blades installed in existing Fan Shroud replacing Stock Fans and motors.

See...….Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans (http://www.zr1.net/forum/showthread.php?t=29972)

This provided by Phil (Jagdpanzer) which I recall he is experimenting with shortly.
http://www.zr1.net/forum/picture.php?albumid=387&pictureid=3857

Dual 11" Spal Fans from Summit Racing (2,700 cfm) (https://www.summitracing.com/parts/spu-ix-30102052/overview/)

If I read this correctly, I could install two of these 1,600 cfm Spall 11" Fans and end up with 3,200 cfm :thumbsup:
Single 11" Spal Fans 30102800 on Ebay (1,600 cfm) (https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=Spal+Fans+30102800&_sacat=0)

Might have to reconsider when the fans come on and if both come on :p

[Pete]

Rob unless your racing her really hard oil cooler is useless till oil reaches 200* for the T-stat to fully open.
I don't road race my Z,some drag racing and street driving.
What i notice is my oil temps are about same as my engine temps +- 10*

Pete

[Vette Guy]

Bob, what temps are you seeing that are prompting changing the stock cooler? Our cooler is used by road racers in L98 and LT1 applications. I went to a Setab 9-row cooler in my L98 (sitting in front of the radiator) but also upgraded to a HV pump to effectively move the oil. I agree with everyone here that you’d introduce a lot of potential engine failure issues for little benefit.


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[GOLDCYLON]

I am considering an experiment using Spal Fan motors and blades installed in existing Fan Shroud replacing Stock Fans and motors.

See...….Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans (http://www.zr1.net/forum/showthread.php?t=29972)

This provided by Phil (Jagdpanzer) which I recall he is experimenting with shortly.
http://www.zr1.net/forum/picture.php?albumid=387&pictureid=3857

Dual 11" Spal Fans from Summit Racing (2,700 cfm) (https://www.summitracing.com/parts/spu-ix-30102052/overview/)

If I read this correctly, I could install two of these 1,600 cfm Spall 11" Fans and end up with 3,200 cfm :thumbsup:
Single 11" Spal Fans 30102800 on Ebay (1,600 cfm) (https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=Spal+Fans+30102800&_sacat=0)

Might have to reconsider when the fans come on and if both come on :p


I've used these for 5 years. Modded daily drivers in AZ heat when the freeway hits 128/135 its a must

[lfalzarano]

You’ll have to consider, the the extended lines would be exposed to more heat from the road, than in the current original route. Air flow and pressure through the oil cooler radiator fins will be significantly less than in the original location. It doesn’t appear to aid in lowering oil temperatures when needed. JMHO


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[GOLDCYLON]

Bob, what temps are you seeing that are prompting changing the stock cooler? Our cooler is used by road racers in L98 and LT1 applications. I went to a Setab 9-row cooler in my L98 (sitting in front of the radiator) but also upgraded to a HV pump to effectively move the oil. I agree with everyone here that you’d introduce a lot of potential engine failure issues for little benefit.


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OMG Bob! Don't.... for these reasons..... very little benefit. For 5 pounds skip the heavy lunch......

[Locobob]

I'm not having any issues with oil temps, or coolant temps. My oil temp needle barely lifts off the bottom, usually hovering between the two zeros in the 100 indicator mark, even during spirited driving. The only time I've seen it get above that was on a road course track day. What got me thinking about it is I need to put in a new A/C condenser so I'd be digging around in there anyhow. I was mainly thinking about the weight issue, our cars are nose heavy so anytime I see a chance to remove weight from the nose or move it reward it peaks my interest. The main issue I see here is pressure drop, I'd be adding at least 20' of hose to the system and I'm not sure if or how that might effect the cooler bypass valves operation. I don't see any real danger of catastrophic engine failure here, hell the cooler is rarely enabled anyhow, unless maybe I didn't prefill the oil cooler and lines and had a situation where the valve opened and created an oil starvation issue.

[A26B]

.......... unless maybe I didn't prefill the oil cooler and lines and had a situation where the valve opened and created an oil starvation issue.

That won't happen. thermostat valve was engineered with bypass to insure the oil cooler system is always charged with oil.

[Locobob]

Seems to me like the worst that could happen then is that the cooler doesn't work very well do to pressure drop.... so I'd need to figure out what the drop is from adding about 20ft of hose to the system

[tccrab]

I'd be worried about potential damage from road debris being kicked up from the front tires as well as the low pressure area under the engine.
And damage from speed bumps, pot holes etc.

Our Zee's ride low, low, low, anything hanging from the bottom is going to be in harms way.


Just my $.02


'Crabs

[Locobob]

I'd be worried about potential damage from road debris being kicked up from the front tires as well as the low pressure area under the engine.
And damage from speed bumps, pot holes etc.

Our Zee's ride low, low, low, anything hanging from the bottom is going to be in harms way.


Just my $.02


'Crabs


Proper undercar routing would certainly be a concern. I would run braided hose and protect it in high exposure areas. I was eyeballing the covered channel inside of the rocker moldings for most of the run, might be able to get two hoses through there.

[Vette Guy]

I run an Accusump to the rear of the ‘88 car. A single braided line barely fits under the rocker. The Accusump does not need a high pressure area to keep it cool like a cooler would.
What Crabs pointed out is that the area under the car is a low pressure area, unlike the stock location in a high pressure area. The area under the car in the rear may not provide sufficient airflow for the oil cooler to work - racers have used the rear area to cool gearbox fluid, but with puller fans directly mounted to the cooler.


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[tnova]

I've recently moved my battery to the box behind the passenger seat and used the rocker areas to run the positive and negative cable; negative along passenger side outside the panel alongside the fuel lines and positive inside the rocker panel with factory wiring. Note much room, especially for the size hose needed. Though I haven't run my ZR-1 on the track yet, I've plenty of experience with a brand "P" air cooled race car that lives on cooled oil run from the rear engine to the front. The lines are huge, 30mm to 50mm. No such room on the bottom of a stock ZR-1 for lines this large. Other ways to remove front end weight are a better option.

[WARP TEN]

I run an Accusump to the rear of the ‘88 car. A single braided line barely fits under the rocker. The Accusump does not need a high pressure area to keep it cool like a cooler would.
What Crabs pointed out is that the area under the car is a low pressure area, unlike the stock location in a high pressure area. The area under the car in the rear may not provide sufficient airflow for the oil cooler to work - racers have used the rear area to cool gearbox fluid, but with puller fans directly mounted to the cooler.


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My current 2016 Z06 has a trans cooler in the driver side rear fender behind the wheel with a fan (puller I think) on it. (Not my car in the picture)--Bob

[Locobob]

Well I'm going to be working on the belt tensioner and also replacing the a/c condenser so I've been kicking this around again. I remember that some of the turbo charged cars either Callaway of LPE I think utilized the inside of the frame rails to run some plumbing from the rear to the front. It occurred to me that perhaps I could route oil cooler lines through the frame rails themselves. Anyone know if there are bulkheads or other obstructions inside the frame rails? If not it would seem possible to snake a line through there.

[spork2367]

I was mainly thinking about the weight issue, our cars are nose heavy so anytime I see a chance to remove weight from the nose or move it reward it peaks my interest.

I'm not sure that moving a couple pounds from the front to the rear, only to add 3-4 lbs total to the car will be worth it.

[XfireZ51]

How much more oil would u need to fill the system?

[Locobob]

I'm not sure that moving a couple pounds from the front to the rear, only to add 3-4 lbs total to the car will be worth it.


I haven't had a chance to weigh the stock cooler yet but my plan would be to utilize a smaller lighter cooler in the rear as the extra run of the hose would allow for some cooling as well. Yeah it's not a ton of weight but there's not many options to eliminate or move a lot of weight at any one time on these cars. Mostly its a few pounds here and there that add up.


I'm guessing I'd end up with a slight net gain in oil capacity with a smaller cooler and a longer hose run.


My main concern at this point is finding a viable safe route for the hoses.

[Locobob]

Also I should note that I already have a larger aftermarket radiator, I feel like that coupled with the additional air flow gained by moving the oil cooler out of the radiators path should mitigate a loss in efficiency of the oil cooler itself... which is likely given that the new location would not see as much air flow as the stock location.

[RussMcB]

It sounds like you've already convinced yourself to move forward with this mod, but I'm scratching my head as to why. Seems like there are plenty of reasons not to do it, and no real (noticeable) benefits.

But, I understand it's a hobby and considering mods can be fun.

If it were me I could think of lots of other things (not necessarily ZR-1 related) that would be higher on the list of things to do.

I hope I'm not out of line by giving this idea a public thumbs down. Heaven knows I've done plenty mods I've regretted later. I could give a tour around my garage and point them out. :-)

[Locobob]

It sounds like you've already convinced yourself to move forward with this mod, but I'm scratching my head as to why. Seems like there are plenty of reasons not to do it, and no real (noticeable) benefits.

But, I understand it's a hobby and considering mods can be fun.

If it were me I could think of lots of other things (not necessarily ZR-1 related) that would be higher on the list of things to do.

I hope I'm not out of line by giving this idea a public thumbs down. Heaven knows I've done plenty mods I've regretted later. I could give a tour around my garage and point them out. :-)


Well I'm not quite there yet. My main goal here is to move weight off the front of the car to the rear which is beneficial to all aspects of performance. But I still have misgivings as this seems to be somewhat uncharted territory. My main concern would be pressure drop in the system, although some cursory poking around seems to indicate that pressure drop through added hose length is somewhat minimal. I'd feel a lot better about it with some expert engineering opinions. I know Graham Behan lurks in here occasionally, if he or some other Lotus/GM/Merc engineers would chime in I'd feel a lot more confident about whether or not to proceed with this. One thing I could do is simply undo the existing plumbing and connect it to about 20' of hose in a circle and see what that does to oil pressure, but to do so would be difficult as I'd have to run the motor hard enough to activate the oil cooler switch.

[RussMcB]

I agree taking weight off the front could/should theoretically help, and Graham (and other smart people here) will have good advice and opinions.

I often forget that many here's main focus is straight line performance, while mine is road racing, and you’d need to be Lewis Hamilton to notice a change like this on a road race track.

[Locobob]

So the oil cooler pretty much full of oil is 11.5lbs FYI... I'm not going to pursue this at this time as its summer and I don't want the car down... but I might look at it again when its time for a radiator or other "while I'm here" service. At some point I'll probably splice in a 20' loop of hose and do some pressure and temperature testing before making a decision on this.

[tnova]

A really easy to do front weight reduction is to replace the battery with a modern gel or even lithium battery. Perhaps the cost of the battery is similar to the cost of a cooler, mount, hoses, and fittings.

[Hib Halverson]

BAD IDEA!

1) Not only will there be pressure drop with 20 linear feet of hose but any place the hose or line turns a corner, the pressure drop increases. A 45° bend has about a much restriction as 5-feet of hose. A 90° bend has as much restriction as 10-ft. of hose. Years ago, I installed an oil cooler and remote filter on a Big-Block C3. The hose run was only about six feet total. The oil pressure loss was so much, I had to shim the pressure relief in the oil pump and even then there was still 10-15 psi less than before I installed the cooler.

2) At engine start, it will take a long time for oil under pressure to reach the bearings.

3) As engine speed increases, there will be a lag in oil pressure increase.

4) Inertia...as you accelerate oil flow will decrease. That's the last thing you want as RPM increases. Vehicle acceleration aside, the engine oil pump is going to have to work really hard to move the amount of oil in those lines and work even harder when it has to accelerate oil flow.

5) Complexity. Running two oil lines from the front of the car to the rear is going to be a big job. Also, if you think you can run two straight hoses all the way back, think again, then re-read #1 above.

6) Weight. You will not gain anything in a practical sense. Yes, you may move the CG of the car fractionally to the rear, but the overall weight of the car will increase with all that hose, fittings and extra oil.

7) Oil capacity. Get 20-ft of AN-12 hose. Plug one end. Fill the hose full of water then drain the water in to a half-gallon jug and see how much you have. I'll bet it's a lot more than you think.

[XfireZ51]

Super insight Hib! Thanks for that clarification.

[Locobob]

A really easy to do front weight reduction is to replace the battery with a modern gel or even lithium battery. Perhaps the cost of the battery is similar to the cost of a cooler, mount, hoses, and fittings.


Already have a rear mounted light weight battery :)

[Locobob]

BAD IDEA!

1) Not only will there be pressure drop with 20 linear feet of hose but any place the hose or line turns a corner, the pressure drop increases. A 45° bend has about a much restriction as 5-feet of hose. A 90° bend has as much restriction as 10-ft. of hose. Years ago, I installed an oil cooler and remote filter on a Big-Block C3. The hose run was only about six feet total. The oil pressure loss was so much, I had to shim the pressure relief in the oil pump and even then there was still 10-15 psi less than before I installed the cooler.

2) At engine start, it will take a long time for oil under pressure to reach the bearings.

3) As engine speed increases, there will be a lag in oil pressure increase.

4) Inertia...as you accelerate oil flow will decrease. That's the last thing you want as RPM increases. Vehicle acceleration aside, the engine oil pump is going to have to work really hard to move the amount of oil in those lines and work even harder when it has to accelerate oil flow.

5) Complexity. Running two oil lines from the front of the car to the rear is going to be a big job. Also, if you think you can run two straight hoses all the way back, think again, then re-read #1 above.

6) Weight. You will not gain anything in a practical sense. Yes, you may move the CG of the car fractionally to the rear, but the overall weight of the car will increase with all that hose, fittings and extra oil.

7) Oil capacity. Get 20-ft of AN-12 hose. Plug one end. Fill the hose full of water then drain the water in to a half-gallon jug and see how much you have. I'll bet it's a lot more than you think.


Thanks for the input Hib.


I've been doing some more research and here's a few things I discovered.


The factory oil cooler is quite large and has a total of about 15 feet of .78in OD piping.... 6 rows of horizonal pipes are bracketed by the in and out vertical pipes. I'm not sure how that stacks up pressure wise when compared to say a 15 foot straight run. I talked to tech at Derale and was told that the factory system is not a very efficient design by todays standards. It may be possible that a smaller but more efficient cooler combined with a longer hose run may not be all that different in pressure. Probably need a fluid dynamics engineer and testing to know for sure.


As far as point 2 goes my understanding of the system is that the cooler bypass line is temperature activated... therefore on start-up the cooler line is effectively bypassed thus it should have no effect on engine oil pressure at that time. If you have information to the contrary I'd like to see it. Routing a cooler off a remote oil filter line on a big block would be a whole different ball game as it sounds like oil would flow through the cooler 100% of the time.


Weight of about 20ft of line would be 3-5lbs dry depending on the size and type of line... but a smaller aluminum cooler should be lighter than the stock one. Fluid weight would depend on the capacity of the new cooler and added lines vs the stock system... I don't think its really feasible to drop overall weight, probably a wash at best. The main benefit would be moving weight rearward.

[32valvZ]

What about plumbing hard lines, and not rubber hose? Might help with pressure loss because its rigid, and maybe smaller I.D. Also, less chance of damage. I realize this could be harder to accomplish... just thinking out loud...

[XfireZ51]

Hib is saying that the “lag” in such a system could be like “turbo” lag only detrimental to the motor. Takes too long for oil pressure to respond to requirements of the moment, ie WOT. Dry sump for the LT-5 would have been very interesting.

[Jagdpanzer]

Bear in mind the LT5 oil cooler circuit is has a thermostat control valve that begins opening when the oil temperature reaches control range. It directs just enough oil through the oil cooler to maintain proper temps. During normal street driving probably not much oil flow is sent through the cooler as the engine heat loads are not very high. Instead most of the flow goes directly to the engine mixed together with low volume of cooled oil coming from the cooler. The oil heat load increases when more power is produced like at the track. The oil cooler thermostat valve reacts by directing more oil through the cooler while at the same time reducing the volume of uncooled oil going directly to the engine. The engine sees the same over all flow however, more of it has passed through the oil cooler.

[Locobob]

Bear in mind the LT5 oil cooler circuit is has a thermostat control valve that begins opening when the oil temperature reaches control range. It directs just enough oil through the oil cooler to maintain proper temps. During normal street driving probably not much oil flow is sent through the cooler as the engine heat loads are not very high. Instead most of the flow goes directly to the engine mixed together with low volume of cooled oil coming from the cooler. The oil heat load increases when more power is produced like at the track. The oil cooler thermostat valve reacts by directing more oil through the cooler while at the same time reducing the volume of uncooled oil going directly to the engine. The engine sees the same over all flow however, more of it has passed through the oil cooler.


Yeah this was my understanding of the system. If I remember correctly it is never the case that 100% of the oil goes through the cooler

[Locobob]

So I may have come up with a better solution to lightening up the front of the car:
https://beta.rondavisradiators.com/product/1989-1996-corvette-c4-sb-bb-with-engine-oil-cooler/
I just got off the phone with Ron and he says this radiator with the built in oil cooler is only about 2-3lbs heavier dry than their normal C4 radiator. Now the oil cooler displaces a little coolant so its probably about the same weight wet as the standard RD radiator.... which means I could save a full 11.5lbs by ditching the stock oil cooler. I currently have an old RD radiator in my car so it would pretty much be a drop in save for routing the oil cooler lines. Now the oil cooler capacity on this is quite a bit less than the big stock unit but water cooling is inherently more effective than air cooling so that could offset the reduced capacity. I'm thinking it would probably be fine given that my oil temps normally barely move off the needle. The only time I've seen oil temps come up a bit is on track days and I haven't done one of those in years.

[A26B]

Robert,
If you decide to go this way, here is some info for you to consider.

Edelbrock-Russell ProClassic II hose is much lighter than the typical braided SS of the same size. Using crimped fittings is less bulky & looks cleaner.

I only use -10 (5/8") hose for the Oil Cooler Hoses we make in house. If you can make the RD radiator connection -10AN male, I can help you with the custom hoses. Get an approximate length & I can send you a piece of hose to use for obtaining the actual overall length of each hose. Send it back with the overall lengths. I stock 90 deg swivel & straight crimp fittings. Look on my website to see the hose & fittings.

Might be able to trade in your OE Oil Cooler on the new hoses if you are interested.

[Locobob]

Robert,
If you decide to go this way, here is some info for you to consider.

Edelbrock-Russell ProClassic II hose is much lighter than the typical braided SS of the same size. Using crimped fittings is less bulky & looks cleaner.

I only use -10 (5/8") hose for the Oil Cooler Hoses we make in house. If you can make the RD radiator connection -10AN male, I can help you with the custom hoses. Get an approximate length & I can send you a piece of hose to use for obtaining the actual overall length of each hose. Send it back with the overall lengths. I stock 90 deg swivel & straight crimp fittings. Look on my website to see the hose & fittings.

Might be able to trade in your OE Oil Cooler on the new hoses if you are interested.


Sounds like a plan Jerry, my radiator and everything around it is about 15 years old now so wouldn't hurt to freshen things up. I'll probably do some of your red silicon hoses as well. Probably going to be a winter project as I don't want my car down with the weather being nice here.