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Discussion Starter #1
Anyone logging/monitoring your oil temps? Please post your findings....

I've always thought it odd that we have like 25 feet of oil cooling lines and two, relatively huge oil coolers up front in a car that's already fairly well liquid cooled (these things never run hot).

Intuitive drawbacks to our oil system is that we surely get a nasty pressure drop in oil pressure across the 25 foot hose section, our oil takes "forever" to warm up, and perhaps our oil doesn't get hot enough to do its job effectively (recall that cold oil puts excess pressure on parts and does not lubricate as well as hot oil.... to a point anyway...).

So what were the Lotus engineers thinking here? Was all this cooling really needed? Is our oil cooling system over engineered to the possible detriment of the engine from the excess in hoses and heat exchangers? Any chance the slow warming oil is part of the reason we have cam issues where the celica guys do not?

The TRD oil cooler for the 2zz uses engine coolant to cool the oil, which is typical of OE oil coolers. These coolers warm up the oil faster (at a similar rate that the coolant warms obviously) yet, they still typically keep oil in that magic 200-220 degree range where oil typically works best... Another interesting thing about the coolant driven oil coolers is that don't need 25 feet of hose to work, just about 2 feet!:up:

I'm clearly thinking outloud here and tossing around some ideas about changing the OEM oil cooling system...

Best,

Phil
 

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Phil,
The oil pressure response issue during transient throttle was the reason we stopped using the factory coolers 3 years ago.
Here are a few alternatives.
Mocal liquid to oil

Pass side scoop
 

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Discussion Starter #3
I knew you guys were doing that. I know Frank has relocated his after he used the front coolers for heat exchangers as well... I was thinknig of just putting the TRD oil cooler on the car, which is a sandwich plate between the block and the filter. It would be nice to have some documented figures before and after the change- specifically at the track since that's where things tend to get the hottest...

Do you guys have any figures? I'd like to know both oil pressure (post coolers) and oil temps (before and after coolers would be nice)....

I had read about a fella with a Celica who actually tracks his GT-S was maintaining temps no higher than 220, but averaged 210 with the TRD cooler and had temps in the 250+ range w/o the cooler. I suspect 220 in our cars would be pretty ideal. Particularly, if we could maintain better oil pressure while doing so... Of course, if this sandwich cooler is so great, why didn't the Lotus engineers take that approach? Tim M would be PO'ed if a guy deviated from Lotus's excellent engineering without good reason:D I presume it's possible that Lotus took the approach they did due to cost and availability, as they often were forced to do with other parts on the car.

Best,

Phil
 

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our oil takes "forever" to warm up, and perhaps our oil doesn't get hot enough to do its job effectively (recall that cold oil puts excess pressure on parts and does not lubricate as well as hot oil.... to a point anyway...).
The oil adapter that the oil lines connect to is a thermostat controlled adapter. It only sends the oil to the coolers as it heats up and gets warm enough to start to open the thermostat (just like the one in the cooling system). A cold engine is not sending the oil through the coolers. A hot engine is sending some (or all) of it's oil through the coolers. It's part of why the oil temperatures in the engine don't get as high as they do in most cars.
 

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Discussion Starter #5
The oil adapter that the oil lines connect to is a thermostat controlled adapter. It only sends the oil to the coolers as it heats up and gets warm enough to start to open the thermostat (just like the one in the cooling system). A cold engine is not sending the oil through the coolers. A hot engine is sending some (or all) of it's oil through the coolers. It's part of why the oil temperatures in the engine don't get as high as they do in most cars.
Good call Tim. I didn't see a thermostat type valve when I had the engine out, but I didn't look 'that' close either. I'm still curious why they didn't use a sandwich type cooler on the car and use the coolant to cool the oil. The water lines are already on the car for the TRD type sandwich cooler. They're the ones that are simply U'ed right above the filter that are known for leaking:rolleyes: The U turn essentially goes nowhere and loops back around. I cut that section of coolant line out and replace with about a 4" piece of heater hose, which wa much cleaner and remove a place for leaks... It's almost like it was thought about and then abandoned. I wonder if TRD couldn't deliver enough sandwich coolers for the production run or something like that...???...???

Cheers,

Phil
 

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Of course, if this sandwich cooler is so great, why didn't the Lotus engineers take that approach? Tim M would be PO'ed if a guy deviated from Lotus's excellent engineering without good reason:D I presume it's possible that Lotus took the approach they did due to cost and availability, as they often were forced to do with other parts on the car.
Everything in life is a compromise (usually involving cost). From stuff I've read, people with oil temperature guages are seeing oil temps around 220 or so while doing track days in the middle of the desert. I suspect that the coolers are actually doing a very good job - at least for most people.

As for the pressure drop, the lines are fairly good size and probably more than handle the oil flow. It's not like there is a huge volume of oil flowing through the system. As the volume/velocity of floe goes up, the pressure drop would be significant, but again for our engines, the flow isn't really that high and it's probably sized about right (putting a bigger sized hose wouldn't have been a big deal for the factory if had been necessary).

And everything can be improved upon. It's all a matter of what an improvement in one area causes what effects in another (i.e. more cooling = more weight: etc.). And cost is always a trade off - it's one of the reasons that we drive Elises instead of Enzos...
 

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Good call Tim. I didn't see a thermostat type valve when I had the engine out, but I didn't look 'that' close either. I'm still curious why they didn't use a sandwich type cooler on the car and use the coolant to cool the oil. The water lines are already on the car for the TRD type sandwich cooler. They're the ones that are simply U'ed right above the filter that are known for leaking:rolleyes:
Actually, in the Celica, that oil does use a water (coolant) cooler. The hoses that are there is route to the coolant to the oil cooler. It is an effective way to warm up the oil, and then to cool it. But it adds to the radiator requirements since it must now handle the additional heat from the oil cooler. It also has to controlled by a thermostat since you want coolant to run about 195 degrees, and you want the oil to be 20 degrees or so higher.

Lotus actually removes the oil to water cooler and replaces it with the adapter to the oil cooler lines. That's why we have the U-tube. I don't know if the engine comes that way from Toyota or if Toyota uses the engine in another car without the cooler. The U-tube was a way to bypass the removed oil cooler, but has the problem of rubbing on the adapter that sticks out more than it would without it being there.

In the diagram below, we have the hoses in the red "circle" and the U-tube, but we don't have the oil/water heat exchanger - we have all the rest...
 

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Discussion Starter #8
Everything in life is a compromise (usually involving cost). From stuff I've read, people with oil temperature guages are seeing oil temps around 220 or so while doing track days in the middle of the desert. I suspect that the coolers are actually doing a very good job - at least for most people.

As for the pressure drop, the lines are fairly good size and probably more than handle the oil flow. It's not like there is a huge volume of oil flowing through the system. As the volume/velocity of floe goes up, the pressure drop would be significant, but again for our engines, the flow isn't really that high and it's probably sized about right (putting a bigger sized hose wouldn't have been a big deal for the factory if had been necessary).

And everything can be improved upon. It's all a matter of what an improvement in one area causes what effects in another (i.e. more cooling = more weight: etc.). And cost is always a trade off - it's one of the reasons that we drive Elises instead of Enzos...
I agree with you, Tim. They were on a budget and a tight schedule and compromises were made here and there, no doubt...

It sounds like you think that it may have been a cost and/or availability issue as to why we don't have a sandwich cooler?? That tends to be my thinking. I wonder how much weight could be saved with a simple sandwich cooler? 10-15 lbs?:shrug:

Regarding the pressure drop, it would be interesting to measure it. We may be surprised.

I thought I read that the cars with two coolers were running as low as 180 temps at the track, although I can't recall where I may have read that. That's why I asked...

Best,

Phil
 

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Wasn't Lotus really concerned with oil temps destroying early 2ZZ engines on the Celica? Thought I read about that somewhere. I thought that was why they went with the coolers and the insistence on 5w40.

Take that FWIW - its simply my recollection of what I've read on this board and other sources.
 

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Actually, in the Celica, that oil does use a water (coolant) cooler. The hoses that are there is route to the coolant to the oil cooler. It is an effective way to warm up the oil, and then to cool it. But it adds to the radiator requirements since it must now handle the additional heat from the oil cooler. It also has to controlled by a thermostat since you want coolant to run about 195 degrees, and you want the oil to be 20 degrees or so higher.

Lotus actually removes the oil to water cooler and replaces it with the adapter to the oil cooler lines. That's why we have the U-tube. I don't know if the engine comes that way from Toyota or if Toyota uses the engine in another car without the cooler. The U-tube was a way to bypass the removed oil cooler, but has the problem of rubbing on the adapter that sticks out more than it would without it being there.

In the diagram below, we have the hoses in the red "circle" and the U-tube, but we don't have the oil/water heat exchanger - we have all the rest...
I'm not sure that's right about the Celica. From what I've read on the celica forum, they don't have that cooler either. The cooler is a TRD part...I may have read incorrectly and they may jsut be repalcing the stock cooler with a bigger TRD cooler...


Funny that Lotus used a U tube rather than just cutting the tube to about 4 inches long like I Mainelotus and I did and just connect the coolant rail directly to the block (which is all that 2 foot U tube does). Sure would clean up an already congested area... It just seems like an after thought...

-P
 

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Discussion Starter #11
Here's the TRD cooler, BTW
 

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Discussion Starter #12
I found this excerpt from a guy who post the 986 forum. There' no telling where he got this information from. I think he's a bit off as evidenced in his first statement about lotus tuning the head and intake:rolleyes:.....



>>Lotus has always massaged existing engines rather than produce their own from scratch. The Elan and Europa had Ford/Kent blocks w/ Lotus designed and produced heads. The Seven had a BMC inline 4, again massaged by Lotus. The Esprit had it's 2.2L 910 4-cyl. drawn from a Vauxhall Delivery Lorry engine, again, all new internals and heads.

Even the Elise uses a Kent engine (ROW) and the Yamaha-designed Toyota 2ZZ-GE engine, again with thorough tuning, intake, exhaust and head by Lotus for the US Market.

The 2ZZ-GE features a stroke of 85 mm (3.35 in) to an 82-mm (3.23-in) bore to attain a redline of 7800 rpm. The block is made of fine-ceramic-fiber- and grain-reinforced aluminum-silicon alloy. The piston's rubbing surface is iron-plated, and the pistons are internally cooled by oil jets. The 2ZZ-GE's cylinders are tightly packed, with only 5.5 mm (0.22 in) of metal between the adjoining bores. The cylinder block is split at the crankshaft centerline, and the cast aluminum lower block carries five main bearing caps. The 2ZZ-GE's Lotus designed cylinder head is unique to this engine. Valves are inclined at a wider angle of 43° for freer breathing through the upright intake ports. Valves are 34.0 mm (1.34 in) in diameter - intake and 29.0 mm (1.14 in) - exhaust. The 2ZZ-GE combines the VVT-i continuously variable intake-valve-timing device with the new VVT-L, a Honda VTEC-like variable-lift and variable-timing system, employing two sets of cam profiles for both intake and exhaust. Below 6000 rpm, the VVT-L employs the low and mid-speed cam profiles, and above 6000 rpm, the high-speed profiles. The high-revving 2ZZ-GE's camshafts are sprayed with lubricant oil.

In fact, Toyota had been having problems with this engine siezing and warping the heads in the Celica. They went to Lotus Engineering, who redesigned the Oiling system, added an Oil Cooler for higher capacity and flow and the problem was solved. This is why Lotus chose this engine for the Elise, though they massaged it even further. The Kent ROW engine could not be made to meet US EPA requirements, so Lotus went with the 2ZZ-GE which was already certified and being sold here. Toyota's 2ZZ-GE versions found in their own cars in the U.S. make ten fewer hp at 180 hp than the same engine in the rest of the world which has 190 hp.

However Lotus retuned the 2ZZ-GE for use in Elise, smoothing out the torque dip at the 6000 rpm cam changeover point and strengthening the torque in the other rpm ranges. In addition to the improved torque Lotus brought the peak horsepower back up to 190 in their U.S. version of the engine.
<<<

Best,

Phil
 

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Geez phil.

Just put a bunch of monkeys in your engine bay with fans and call it a day. :p

What about the TRD thermostat? Ronin says he used it with great success.
 

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Geez phil.

Just put a bunch of monkeys in your engine bay with fans and call it a day. :p

What about the TRD thermostat? Ronin says he used it with great success.
I'm not all that worried about the engine temps, and I'm aiming on ditching the stock oil cooler system... I just need a good reason to do so other than my gut feeling... Like many things with these cars, it could be that nobody has taken the time to actually test the theories out there and we're all promulgating wives tales...:shrug:

The T-stat is a fine idea and I'm well aware of it... However, define great success for me? I haven't checked with Frank to see if his car can maintain the 160 temps and he may not know for sure yet since he's still tuning the turbo.. I dunno...

Our cars cool well, but I'm pretty certain my car can't hold 160 with the stock radiator on the track so it's a bit moot for a track rat like me... I've lost track of what Frank has for cooling, he may be able to hold 160- I'm quite confident that I can't hold that temp with my setup though...

Best,

Phil
 

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Phil,
It may be a worthwhile move to mount an oil-temp gauge before you do anything to your oil-cooler. Most cars that find their way to the track, even stock, require additonal oil-coolers...and now that your car is well modded, you're thermal requirements are quite different. I also cannot believe that Lotus would mount oil coolers in the front clam (my car has the twin coolers) for cost savings, as the parts are certainly more expensive than the sandwich adapter. As with some things, overbuilt is a good thing...especially when it comes to thermal capacity...more so when applied to oil, as long as proper operating temps can be reached (oil t-stat).

We are actually blessed when it comes to cooling...ever try to keep a Vette cool on the track?...not fun...

Be good,
TomK
 

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I constantly monitor my oil temp, in the pan, where it should theoretically be hottest after being spun out of the bearings and drained from the top end. On the street I never see over 180 and on track never see over 250. Not sure about transient oil pressure response, but it sure seems quick on my gauge - I never see under 40 psi and at higher revs never see under 75. If there is a thermostat, it is set too low, as IMO oil needs to get over 200 to properly purge absorbed combustion products , water, acids, etc.

As for water/oil heat exchangers, the concern I have is that eventually, you have to exchange heat to the air and if you limit yourself to the surface area of the radiator, it sure seems that less heat can be dissipated than if you have the extra surface area of the two oil coolers. Also, I have to believe that an oil cooler with 250 degree oil in it has to disspate heat better than a radiator with 200 deg water in it. If I saw real test data to the contrary, I could be persuaded, but I think the factory setup is pretty good.
 

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as to the oil to air cooling vs. the oil to water cooling, it all depends on the cooling surface coupling capabilities of the heat exchanger.
yes, the delta t is important but the transfer capability is not shown.

the liquid to liquid transfer path is more efficient on an area-to-area case, but is there THAT much more area to make the front cooler more efficient?...
there just isn't enough data to decide.
so i expect the measure and cut and try method is most practical for us.
thermocouples are cheap, the fluke 152 (i think) is a dual channel device i've used when curious about the efficiency of my dodge diesel aftercooler.
it'll record mins and maxes as well as T1-T2.
if someone is seriously interested, i could loan mine....
sam
 

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I also cannot believe that Lotus would mount oil coolers in the front clam (my car has the twin coolers) for cost savings, as the parts are certainly more expensive than the sandwich adapter. As with some things, overbuilt is a good thing...especially when it comes to thermal capacity...more so when applied to oil, as long as proper operating temps can be reached (oil t-stat).
Yep.

I'm not sure that the Celica used the oil/water cooler. But the reason that it's in the manuals is that Lotus uses it - on the Elise-R in some markets. They upgraded the oil cooling system with the dual oil coolers for the US market to cope with the added heat that we were liable to experience. Later they discovered that two oil coolers weren't necessary (and to save costs), and changed it to a single front mounted oil cooler for the Elise, with the Sport Pack adding the second oil cooler back for the expected track use.

Bottom line is that the oil/air coolers should do a better job of cooling the oil and maintaining the proper temperatures than the oil/water cooler does. The oil/water coolers are usually used where space is a premium and/or for cost savings consideration. I believe that we got the better system.
 

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FWIW: My typical H2O (I know, you want oil, but I don't have an oil temp guage) temps from the OEM dash readout read 190-195 deg F on the highway @ 75-90 mph. On track, the temps go from 205 deg F in clean air to as high as 225 while consistently drafting. Not sure that helps, but data points are data points. :shrug:
 

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Bottom line, in a car where owners routinely spend hundreds (or thousands) of dollars to save a few pounds, it certainly seems like overkill to have two heat exchangers and 25 feet of hose to cool oil that doesn't need to get that cool. Ronin has had good luck with one heat exchanger behind the rear passenger wheel well. I think that, the Mocal system, or the TRD mod would be a good one if only for the weight savings alone.
 
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