[pboglio]

Thanks. It's been a long process really. I think it's coming down to the finish line in terms of wrapping up the CVT, seems like I keep finding stuff to fix/improve....lol.

CVT cooling:
As far as CVT cooling goes, there has been quite a bit done by Juke members and I'll add my thoughts.

My Juke will be running the Setrab 9 series x 20 row (14"x6"x 4.35") with (2) Spal 654 cfm fanpacks mounted in the front of the vehicle. This was to fit in the vertical position left by the stock FMIC location running the 2J FMIC. I'll be running an external oil thermostat set at 180-190*F, and an external large capacity oil filter. With the +330 hp I plan on running, the CVT cooling will have to keep up with the engine output. In case anyone was wondering, a typical CVT uses: 12% power on the CVT oil pump, 4.7% power on the Torque converter, 13.5% power on the Variator/Pulley assembly, & 3.2% power on the Output,Transfer, Differential,bearings, etc. At full TCC lockup (i.e. > 18 mph), the torque converter isn't losing any power, so the 4.7 % can be eliminated. That leaves about 71.3% available to road power and 28.7% wasted in the transmission. At part throttle, the losses are far less, typically better than an automatic transmission, thus the mpg improvement. When I dynoed at P&L, I put down 183 w.h.p., but I know the engine was making near 260 h.p. based on the mass airflow on the datalogger the day before the dyno run on the same tune. That's close to 28% loss.

So if the engine is putting out 330 h.p. (223 kW), then 28.7% or 94.7 h.p. (70.6 kW) is lost as waste heat thru the CVT at full power. The CVT cooler would need to dissipate about 240,747 Btu/hr to maintain a set temperature. Some of the heat is lost thru the transmission case, but for now I'll ignore it. The CVT oil pump also cavitates at 7000 rpms, so this is the practical upper rpm limit of a CVT vehicle.......oh darn.

At 6000 rpms the oil pump is putting out 16.32 gpm or 10.3 cm3/rev flowrate, assuming no oil bypass flow at full engine power. However, the oil pump is only feeding a fraction of the oil supply to the oil heat exchanger, the remainder is doing work. To make it clear, the oil pump is cooling in parallel to the hydraulic circuit (oil lubrication, pulley, valvebody control, etc.). Actually, only 12.8% oil is bypassed to cooler/lube circuit based on my research. That's 16.32 gpm x 12.8% = 2.1 gpm thru the oil cooler for example. The formula for power is: Btu/hr = Pump flow rate (gpm) x 60 min x (Delta T, F) x 3.91. So, solving for the Delta T, using 240,747 Btu/hr and 2.1 gpm pump flow, I get a Delta T of 488*F, or about 559*F oil temp. That isn't workable, since I really only want a final oil temperature of 185*F (i.e. 115*F over ambient). I'd need to ramp the oil pump flowrate to something like 8.9 gpm, even at 100% heat exchange efficiency, which the formula is assuming. Also very difficult to do with (1) primary pump.

Looking at the Setrab catalog they show BTU/hr ratings for their oil coolers at 0.75 gpm, 1.5 gpm, 5 gpm, and 8 gpm flowrates. The performance drops off with lower flows, so how the pumps and heat exchangers are plumbed makes a difference. Now the strategy that might work best is using the primary oil pump (2.1 gpm) and (2 x 2.0 gpm) Tilton auxilliary electric pumps plumbed in PARALLEL and driving thru (3 x 50,000 BTU/hr @ 5 gpm rating) the oil heat exchangers in SERIES. This produces a combined +150,000 BTU/hr., which should be sufficient. Probably could fit (1) oil heat exchanger w/fan packs in the stock FMIC location, then (1) each without fans could fit in either fender well. The Tilton pump is 2x 3.5 lbs ea, the Fanpack oil cooler is 7.7 lbs, (2) 14.40" x 7.60" oil coolers @ 4.35 lbs each. Total would come in at +23.5 lbs without hose. Now all of this is to maintain a steady state thermal condition for something like a race track, which probably I won't be doing but I routinely do extended highway pulls.

Anyhow, this is the math I did to size up the heat exchangers.......when I get to that point.

 

[squirtbrnr]

@pboglio I smell something fishy... Are you sure you don't work for Nissan and have engineered these cars or transmissions before? Because you've got me fooled. Great job making the science work for you, not against you.

 

[pboglio]

Thanks Squirtbrnr,

Lol, nope I don't work for Nissan I'm an engineer doing product development in another field so the math and R&D come naturally, even if it's not automotive related. Yep, the science has to make sense otherwise it's a lot of wasted effort. Trial and error works too, but it takes a lot longer. That post was my thought process for developing a cooling system to get some baseline development going, hopefully it wasn't too technical.

 

[JuklearWinter]

Not sure that 'too technical' is a term you can apply to what has ostensibly become a scientific journal. I just read every word of your post about drivetrain loss and it was fascinating. Won't remember any of it but the 28% loss part after today, but just that little morsel is useful information. Don't stop with this format.

 

[pboglio]

Here's a little more practical approach that you guys might really be interested in. Been researching how the GTR is dealing with heat load from the DSG transmission which is famous for overheating on the track and going into limp mode, sound familiar? HKS and Greddy seem to be using standard Oil/Air coolers. Well AMS don't do that. They are using the Laminova Oil/Water heat exchanger. Basically looks like a round tube with super dense fin pitch on the oil side, and an extruded core for the water/glycol coolant side. The idea here is that the car radiator is actually under utilized even at full power, while the stock Beehive heat exchanger is rather poor in transferring heat from the oil back to the radiator. Well the Laminova style cooler is super efficient at yanking the heat out of the oil and dumping it back into the cooling system, while also having the ability to balance the heat load with some manual adjustment so as not to over tax the cooling system. This can all be done with the 2.1 gpm (8 liter/min) stock CVT oil pump flow as their performance graphs show for the S34-194 unit. This cooler would fit perfect running parallel to the bumper support in front of the radiator since it's a very small diameter.

Anyway, if AMS can control the GTR transmission temps with this thing, I think our CVT can benefit. I might use a Setrab or Mocal oil cooler as an auxilliary water radiator to get some more capacity if this starts overheating the main radiator, but I actually think it's got a chance of working.

Links below:

Build your own - Laminova

Alpha Performance R35 GT-R Cooling Kit - AMSPerformance.com

From the factory, your GT-R’s engine and transmission share the same inadequate cooling system. Thus, prolonged street abuse or even short stints in racing conditions cause components in the engine and transmission to overheat. Important Notes: The race cooling system also now includes a...

amsperformance.com

 

[pboglio]

Here is the spreadsheet "program" I developed for the CVT & Engine cooling requirements (work in progress), see below. I input my 330 h.p. crank horsepower, and it's showing me as a percentage what I have available for cooling % given the heat exchangers I have listed. The CVT wastes 28% of power AFTER the engine at the crank. Of the 100% power available from the Fuel, 33% goes into the engine crank horsepower, 33% to the radiator cooling system, then 33% thru the tailpipe. So the charts shows radiator power at almost 314 h.p., nearly equal to crank engine power of 330 h.p. but I showed it different as to not confuse the (2) values during the calculations.

I also calculate roughly the cooling capacity of the CVT aluminum transmission case, it's definitely not zero but more like 8-9% based on the surface area and exposure to flowing air. The Setrab cooler is only giving me another 21% cooling I need, and it's already a pretty huge cooler (14" x 6"). Contrary to what I thought previously, it's now very clear that tossing extra oil/air coolers at the setup isn't going to practically work and still hold an 85*C oil temp, even with additional 2 gpm Tilton oil pumps. By work, I mean thermal stability over minutes or hours of endurance racing. For this to be practical, the Laminova cooler is going to leverage the remaining 71% CVT cooling requirement off the main water radiator. As you can see, I'm using the Laminova oil cooler and coolant radiator in a 15/85 % load sharing split, stealing just enough cooling from the main radiator without starving it of capacity for the engine. This can be done with a bypass. The Laminova will be plumbed ahead of the Setrab in a SERIES setup for oil flow, with water/coolant cooling the ambient side for the Laminova, and air cooling for the Setrab. The Laminova will be running in PARALLEL with the main cooling radiator with 40 LPM coolant passing thru it, the remaining cycling thru the normal engine cooling circuit. However, I'm coming up short on the main water/coolant radiator at 89% as it is with the engine cooling demands, so I'll need to tolerate some higher coolant temps or upgrade the coolant radiator with something maybe 10% more efficient. Maybe Griffin can make me a custom aluminum radiator.

Main downside, you cannot drop the CVT oil temperature below 185*F (85*C) of the radiator thermostat setting. Guys think that the radiator "heats" up the CVT oil, and this is true to a slight degree, but see below why it doesn't matter much. Where the factory failed is that the Beehive cooler is too small and the technology isn't near as efficient at swapping heat from the oil to the water, but the general concept is the correct way to go. The GTR use a similar type of oil/water heat exchanger, but it's too small/inefficient for high horsepower/spirited driving. The advantages are much better packaging and lighter weight with access to a massively big front mounted radiator with huge heat capacity.

Oil Cooler Sizing:

Enough with the theory, shown below are the Laminova C43 series peformance curves. The C43 is the core diameter in mm, the length I'm looking at is the -332 which is also mm. At 10 lpm oil flow and coolant cross-flow thru the core at 40 lpm, starting with 90*C coolant temps, I can get roughly 97 *C oil temps coming out of it. In fact, we run at 85*C on the Juke, so the oil temp would be more like 92*C (198*F). Basically the CVT oil temp rise over the radiator is +7*C, that's pretty outstanding. Keep in mind this all assumes the main radiator can keep up with it, see the chart below for that answer.

Something to note here, look at the C43-92 chart, it's loosing thermal control compared to the -332, pushing the oil temps from 97*C to as high as 110-112*C @ 10 lpm. Now imagine the stock Beehive cooler being even much smaller than that.......you can see the trend. Finally, if the factory oil filter gets clogged up..........then the cooling falls off the cliff and you overheat. The charts illustrate this pretty clearly and it's what I've seen on my CVT when I replaced the clogged filter with the cooling being much improved. So Nissan's general idea is brilliant, the sizing/efficiency of the oil/water cooler was really the main problem from the factory. The GTR suffers the same type of issue, factory undersizing.

All this just requires: (1) Setrab fanpack oil cooler (50,000 Btu/hr 14" x 6"), (1) Laminova oil cooler, & optional (1) upgraded aluminum coolant radiator. In the end, this is looking a LOT like how AMS got their GTR setup. Hope you guys enjoy.

 

[pboglio]

Basically, and after much number crunching and rechecking of the data, I'm ready to finalize the CVT cooler design with some modifications.

I've been reviewing the new Chevy mid engine Corvette and the Camaro and noticed something pretty interesting.......they seem to run multiple coolant radiators. The vette has (4) radiators and the Camaro has at least (3). This got me thinking why not run an auxiliary coolant radiator on the Juke where the stock intercooler sits? I don't like the mess of having all these oil coolers all over the place. So, all the various oils (CVT, engine oil, etc.) can run with their own upgraded oil/water heat exchangers but feed back into the main & auxiliary water radiators. This makes for a clean setup, and the aux radiator also boosts the cooling system capacity by ~+23%. I'll be using the Jeep/Patriot/Rogue 4-port Beehive cooler and capping the (2) coolant pipes and using their coolant feeds for the Laminova cooler & auxiliary radiator instead, while taking the beehive oil port connections and feeding them to the Laminova oil ports.

Anyhow, some might argue that the coolant gets pretty hot and that makes the CVT oil hot too. Well, 85*C isn't that hot actually, it's only 185*F. To flow correctly, it's gotta run at an optimum temperature.......guys miss this fact. Run too cold and the oil pump screams until it's warmed up and the belt and bearings don't get adequate lubrication. My new setup would hit a max of ~104*C (219*F) at full WOT for extended periods based on some number crunching, and the additional radiator would give the engine a lot more reserve cooling as well.....win/win situation. If I used that same oil cooler to actually cool the CVT oil instead, it wouldn't work anywhere nearly as good, and I'd also have much less cooling for the main engine.

I'm going to put into the 3D-CAD the Setrab cooler/wfan, Laminova oil/water cooler, 4-port beehive cooler, oil and water plumbing hoses, inline filtration, coolant bypass, etc. etc. It'll give a good idea how I'm routing the setup. It'll be an interesting test once I get all the parts ordered up and laid out.

 

[Macgyver]

Remember there is an All aluminum radiator for the Juke. Much larger. That should fit your needs.

Matt also has figured out the 170deg thermostat(s) upgrade too if you need that 10deg of extra temp drop. Not sure the optimum CVT oil temp.

 

[pboglio]

I was looking at the Japspeed (sp?)....unit. They seem to be out of stock. But yeah, that radiator is good for 30% more cooling capacity. It would actually be perfect for the extra cooling the CVT needs. I like simple and clean solutions, just gotta talk to Japspeed and see if they can do a production run.

A vented hood might also help too. I’ll be running the RS front bumper to get more air into the upper radiator over the bumper support. It’ll be a bit of trial and error to get the engine cooling improved.


Simpler and lighter is better. I’m trying to do some weight savings and I really don’t want to add more weight to the front end, the AWD already understeer bad enough in certain conditions.

The thermostat I’ll have to look into, looks interesting.

 

[pboglio]

I've been reviewing the valvebody hydraulic circuits in the JF011E to try and figure out how Level10 bumped the line pressure and/or secondary pulley pressures up.

The secondary pulley pressure is closed loop with the pressure sensor & solenoid (N/H PWM signal). Sort of like an EVC boost controller. There's no easy way to trick the computer mechanically with springs or shims, the pressure sensor is telling the TCM exactly what the pressure is regardless. The factory designed in a 30% safety margin on CVT pulley pressure to account for wear. The ECM knows what torque is coming from the engine. On a factory new CVT running 330 N-m, the pulley pressure goes up to say 3.1 Mpa in 2nd gear. That 3.1 Mpa of pressure is +30% more than what's needed for 330 N-m. When I look at my CVTz50 datalogs, the factory are increasing pressure linearly as the torque goes up, so it knows how to compensate even on a modified vehicle, at least with ECUTek flash anyway. Now in the real world, the belt wears over time due to worn out valvebody or oil pump, and that 30% margin drops to 20% margin, then 10% margin, then 0%, then -10% and so on. Then the belt finally slips.

What I believe is that Level10 actually modified the Line pressure control, NOT the Secondary pulley pressure control. In a way the are related but the computer will undo any changes to the pulley pressure. These line pressure control valves & springs are fed by PWM solenoids and don't have pressure sensors for feedback, so they run OPEN loop and can be tricked mechanically, from what I can tell.

 

[pboglio]

Oil Filter/Cooler Housing:

Here's a little work I did on the CVT oil cooler adapter for the Juke. It's a custom machined aluminum plate using a Setrab 19-SPT76-20-180-22 Oil Sandwich adapter w/oil cooler ports and a standard WIX style oil filter cartridge. The Setrab part (green insert) has a thermovalve/thermostat for the oil that I might not use but it comes with. The large o-ring is OEM from Nissan, the smaller is a -113 o-ring off the shelf. The difference with my design is that it comes with a provision for an external spin on oil filter, the available products don't have this feature.

Next step is a 3d-printed physical model for fitment with the other off-shelf parts. Engine coolant will then flow thru the Setrab FP920M22i cooler w/fans/temp switch/inline thermostat, and feed that into the Laminova cooler, which'll have engine coolant & filtered CVT oil passing thru it in cross-flow exchange. The Setrab cooler will be mounted vertically where the current OE intercooler sits, and the Laminova mounted horizontally on the 2J custom front crash beam. I'm thinking total weight adder is maybe 12 lbs but I have to add it all up.

The Setrab cooler will have both a temp sensor to activate the fans, and an independent thermostat on the feed/return line with possibly a small bleed to vent any trapped air. The biggest improvement is having a compact but large capacity external CVT spin-on oil filter. I'll be using either a WIX filter or Royal purple, 25 micron rating. This should make changing the CVT oil filter much easier than stock, though still a bit messy. Pressure drop thru the system I'm still calculating but given the cooler & filter I plan on running, it'll be extremely low.

I'm having my CNC shop quote it out early next week. I'll toss all this in 3D-CAD and show the cooling & oil flow directions with everything......minus the actual transmission.

 

[Macgyver]

Well that is an idea for keeping the fluid as clean as possible.

I tried searching for the Jaspeed used or for sale anywhere. Nada.

Keoke was the only one here to install one.

 

[pboglio]

I’ll try and hit them up and see what’s goin on. Maybe we can organize a group buy or something. That Japspeed unit is pretty nice though.

I got the quote for the custom adapter, $265 which isn't so bad. Total CVT oil cooling cost is about $1300 with everything. I'm looking at a rear differential oil cooling system. Possibly mounting a cooler in the aft wheel well compartment where there is some static air pressure. The rear differential w/clutch packs get's pretty hot and performance drops off, but AWD is nice cause with everything locked up there isn't a delay in torque distribution which helps reduce understeer inclement weather (i.e. rain, snow, etc.). AWD-V is great but really only works well in dry conditions since the torque transfer has some serious delay it gets fooled in poor traction conditions.

 

[pboglio]

Finished up the design of my custom CVT oil cooler plate. You can see the 3d-printed prototype in the last picture, fitment is close but I'm still dialing in the dimensions for the Setrab oil filter sandwich. Spent most my time on the CAD stripping weight out of it, got it down to 0.78 lbs. Unlike the available cooler plates, it's massively rigid and won't blow the o-ring out. So far the entire CVT oil cooler assembly (custom plate, oil filter sandwich, oil filter, hoses, & Laminova oil cooler) is coming in around 5.2 lbs vs. 1.6 lbs for the stock Beehive cooler (using CAD & listed weights). Not too bad actually.

Anyway, here is the entire assembly as it'll be mounted on the car. I'm now using the Laminova ECD 54-95 cooler instead of the larger C43-332 cooler. The efficiency is nearly identical, but at 33% the total length. It's using a 54mm double-core which boosts it's efficiency. I found the perfect spot to mount it, right where the stock lower radiator hose manifold sits. It looks like I won't even need to trim the radiator hose, the length is almost identical to the stock hose manifold. The hard point mounting is already available off factory radiator fan shroud. The idea here is that the main coolant flow will pass right thru the Laminova cooler, unlike the factory Beehive cooler which splits the radiator coolant flow off on a small 5/16" hose line. These coolers work most efficiently when all coolant passes thru them. I'm using a spin-on Royal purple 25 micron oil filter & Setrab Oil filter sandwich to route the CVT oil lines in & out using the built-in 180*F oil thermostat. The -8 AN oil hoses will have some slack built in to allow some engine movement. The large Setrab 2-fan pack cooler I instead decided to dedicate for engine oil cooling running in parallel with the factory oil/water cooler, future project. Eventually I'll need a bigger radiator, but for now it'll do.

Next step is ordering up parts, then tweaking the prototype plate design to get everything perfect. Then machine shop quotes & final machining. Hoping in 2 months the entire setup is ready to test fit off the car, then I switch over to finishing up the engine development.

 

[Macgyver]

Maybe cut some holes in your bumper like Yost did ?

 

[pboglio]

Definitely an option. I think the lower part still has some exposure, that’s why I designed a pressure duct to feed it but I’ll have to slap it on and see how it works. A vented hood is high on my list.

 

[Macgyver]

You will be using a RS front bumper right ?

You can remove the right side Fake "Fog" light mount. Then duct that to the cooler. 10mm bolt if I remember what Egg said.