Painted the Differential Case and Cover
 

I got some Dupont Automotive paint and painted the differential case and cover today. I prepped the aluminum cover by masking off the machined surfaces and all holes leading to the inside and sandblasting. That thing was pretty nasty to start, I wish I had taken pictures of it before I did the work.

I also masked off the differential carrier (ring and pinion) with a couple plastic bags and some tape and went at the differential case with an air powered wire brush. It seemed to work pretty well, but cleaning with some solvents to remove all the dust was a pain in the ass.

Painting is not ideal in these cold conditions.... I heated the whole thing up in the shop by sticking it next to the waste oil heater and hitting it with a heat gun, then wheeled it outside, shot it quickly, and hit it again with the paint gun. I've never used a proper automotive acrylic enamel or a paint gun before, so I hope this was OK to do.

Note, the next 2 shots are taken before I had fully scrubbed the dust and residue off, there was a light coating of rust dust there, but I got it off. Hope I did a good enough job, I don't want this flaking or chipping as easily as rattle can seems to do...

http://i916.photobucket.com/albums/a...ket_30202_.jpg

http://i916.photobucket.com/albums/a...ket_30203_.jpg

First Coat

http://i916.photobucket.com/albums/a...ket_30205_.jpg

http://i916.photobucket.com/albums/a...ket_30206_.jpg

Second Coat

http://i916.photobucket.com/albums/a...ket_30207_.jpg

http://i916.photobucket.com/albums/a...ket_30209_.jpg

Finished

http://i916.photobucket.com/albums/a...ket_30215_.jpg

http://i916.photobucket.com/albums/a...ket_30214_.jpg

http://i916.photobucket.com/albums/a...ket_30212_.jpg

http://i916.photobucket.com/albums/a...ket_30211_.jpg

I also decided I will never paint my own car.

Might have reconsidered painting the aluminum housing, you just added a layer of insulation reducing its ability to dissipate heat.

It will be fine. Diff Coolers are much more effective than conduction through the case and convection from the case to the air.

Hey, that background looks familiar... :)

I CERTAINLY remember that Supra.

so your going to move the spot where conductive heat transfer occurs?

I plan on using a heat exchanger to pull the heat from the gears. I'm getting some advice from a certain Eaton engineer on the proper design of gear cooling. He may or may not be patrolling this thread... :o)

Differential Heat Exchanger Design Discussion
 

Supercharged FC, the pinion sits lower than the axle center line. I looked through my Rx-7 manuals and found this picture for the stock fluid level:

https://www.rx7club.com/attachment.p...1&d=1292281596

This indicates to me that the pinion is at least partially submerged in the gear oil. So, perhaps simply exchanging the fluid as opposed to designing a complex squirter will be sufficient.

From what I can find, most of the 350z and E46 guys are just simply exchanging the oil.

Diff cooler ideas
 

I'm still looking into this but I got a quick pointer from my friend at the upside down axle company. You need one roller submerged of the highest bearing. You can verify this with the sight tube test. In most cases this is the front pinion bearing but in a RX7 it might be the stub shaft bearings.

https://www.rx7club.com/attachment.p...1&d=1292296788

The biggest issue you might run into is having to over filled system to keep the cooler filled or making foam with pump. Overfilling would cause the system to overheat and lead to seal issues. In an ideal world your cooler could be lower than the fill plug. Like these -

https://www.rx7club.com/attachment.p...1&d=1292296788
https://www.rx7club.com/attachment.p...1&d=1292296788
https://www.rx7club.com/attachment.p...1&d=1292296788

In an RX7 I would shoot for something like this GTR (or the white 350Z above). Note the fittings are on the top of the cooler preventing the excess oil from running into the diff. This can also be accomplished with check valves, thermostats, or regulator valves (opens when pump creates sufficient pressure). I also dig the location of this cooler: lots of air, short hoses.

https://www.rx7club.com/attachment.p...1&d=1292296788

With mechanical pump you need a pressure regulator to handle warm up. With an electric system you could simply wait until it heats up, but having a thermostat system could be beneficial.

Holy shit, this is something I would never have suspected a couple years ago!!! Then again this engineer has grown up from his ghetto build of yesteryear. Although now his car seems to be broken more.

I must say you just know the coolest people don't you. :lol:

Diff cooler
 

I was talking to the lube lady about this and you should try to keep your temps diff lube temps below 250F-300F depending on your additive package. 180F is a good target temp for 75W90. Also you shouldn't have issue with foaming 75W90.

Getting a temperature sensor that you can datalog with would be a good first step. You can adjust the system from there.

I'm guessing you are running a stock TII LSD, which means some sort of additive package for the clutch packs (which can be mostly smoke and mirrors), but if ever switch to a torsion or want to play with blending you might try Road Ranger 75W-90 FE. It has been shown to reduce running temperatures (designed for Fuel Economy hince FE).

Just some ideas :)

I am running an NA diff as dictated by the rules. I had to sell my KAAZ :-(

I recently picked up a rebuilt stock NA diff with 4.30 gears in it and oversized shim plates on the clutch pack. We will see what condition it is in, but just for the gears, I can't complain about the price.

I am currently working on a duct design. My idea on ducting the heat exchanger is that I can get away with a smaller exchanger for the same amount of heat rejection, thus saving weight and having a nicely packaged system. I will be validating my design with the use of CFD, mostly in order to get an idea of the flow across the heat exchanger. I'd like to do some iterative design work; that is, make some changes and see the results. Look back in a few weeks or so to see the process.

Something just popped in my head. Can't I use the same oil in the transmission as the differential? Front drive cars do, and for this reason, I could use the same cooling system to cut down on complexity and weight.

Given that they would likely heat at different rates, I could still use separate thermostat systems on each one, and do a neat-o squiter on each gear for the trans (although I would like to save that for the dog box).

Can you think of a reason that mixing the oils isn't OK? I tend to think it is given the racing history of Hondas and other FWD cars...

Believe there is a 5.12 diff for sale in the classified section of this site. Not sure what your transmission plans are, but even with a 1:1 top gear, a 4.30 is probably going to be too tall.

Very Quick CAD Work on Duct Design
 

Here's a quick idea on what I have in mind for the cooler.

Basically, I have a diffuser, which turns the low pressure, high velocity air from under the car into high pressure, low velocity air (much like how duct work for a radiator is designed). Then, I have the reverse of that on the other side of the heat exchanger, which turns it back into high velocity, low pressure air.

Not modeled here is the freeflow "ramp" which will cause the air inside the exiting duct to be a lower pressure than the air flowing over it, which will give a favorable pressure differential for the flow to exit.

Once this system is modeled, I will verify with CFD in order to maximize the flow across the heat exchanger. I will use this iteratively to select my heat exchanger.

Any racers out there that have temperature taps on their diffs, speak up, I would like to know the conditions that cause the highest temperatures, and size accordingly.


http://i916.photobucket.com/albums/a...uctWorkV11.png

http://i916.photobucket.com/albums/a...uctWorkV12.png

http://i916.photobucket.com/albums/a...uctWorkV13.png

Yeah, I have a spreadsheet I have been working on to optimize the trans, and had that sneaking suspicion.

I may gut mine and buy the gear... Haven't wanted to part with that much money yet.

The 5.12 and 4.88 are spendy but worth it. Most of the tracks in the area will have similar top speeds, even though their layouts are vastly different. An E-prod car is probably going to see a terminal speed of around 135-140 at M-O, ORP, and Grattan. Easy enough to figure out top gear and r&p will work.

Any idea what you're going to do for a trans?

Nope, the ratios I came up with don't exist in a T-5. I hear the Jerico is a good box. Any suggestions?

Seth

I believe the issue you will runinto ina RWD car on slicks is that to protect the diff and its clutch plates and R&P your going to want to use something along the lines of Redline Shockproof "Heavy" with some amount of fritcion modifier, and in the gearbox you will likely want to run Shockproof Liteweight or similar. I would not mix the two.
FWD/AWD cars get away with one oil but its usually a compromise and they are somewhat traction challenged, where a RWD car with 55 to 60% rear bias and good tires does not suffer this issue.

Use gear oil for gears, not transmissions!

I know it is common practice but there lots of engineering that goes into both for their particular needs. I run Roadranger CD 50 transmission oil (uses different viscosity ratings) in my TII trany and have seen benefits in cold and high rpm shifting.

It will depend on what box you run in the end.

Combining the cooler and pump (as done in F1), assuming like oils, would be interesting but also adds risk if you get a leak. Blowing a mazda diff is much better than $3K race box. Also use a good filter, small debris can have a huge effect on bearing performance.

I sent you some light reading in an email, we can talk through some things if you are serious about adding forced lubrication to your transmission. I would hestitate on a high dollar race box unless there is precedence, but on a TII or NA I'm all in.

Keep working, I want to watch you race next summer!

Sweet cooler ducting

Well, I won't be getting the dog box for a little while, so the idea of the combined system was a little far fetched anyway.

Here is some advancement on the duct design. I'm in the middle of meshing the part, then I'll get some CFD done on it. Here you can see the ramp that I mentioned earlier. Hopefully, this will create a pressure differential between the air in the outlet duct, and the air just outside the outlet duct.

I'll be running 4 speed cases, one at each vehicle speed:
-50 MPH
-75 MPH
-100 MPH
-135 MPH

More pics:

http://i916.photobucket.com/albums/a...rDuctWork1.png

http://i916.photobucket.com/albums/a...rDuctWork2.png

http://i916.photobucket.com/albums/a...rDuctWork3.png

http://i916.photobucket.com/albums/a...rDuctWork4.png



This last picture shows the fluid domain that I'm analyzing around the duct. I haven't put much thought into this part, and it will probably need changed. I haven't taken any pictures of under the car or where I will be putting this cooler, so the actual cooler design and ducting will change from what is seen here. This is just a practice to see if the theory works out.

http://i916.photobucket.com/albums/a...luidDomain.png

The fluid domain basically represents flow under the vehicle, with one wall being the undercarriage, one being the road surface, and the other two being either an exhaust, fuel cell, driveshaft, or something like that. Its a little bit crude, but the idea is there.

I've never done it but thought about it quite a bit and a hybrid Miata/RX-7 box looks interesting. With the right r&p the Miata box can be combined with the short OD gear of one of the first gen boxes (forget which one) to produce a box with 4 usable gears. The Miata box has a lower input ratio than the RX-7 box along with a 2nd gear that's quite a bit taller. To get the right OD gear you'll need to actually count teeth and not rely on published ratios. The input ratio changed over the years, making the published numbers no an accurate representation of what you would need to look for. Forget which r&p would work well with it. Thinking the 4.88 or 4.77. I might have all the figures stashed away somewhere.

The synchros are still going to be a liability. You could have Liberty build the box and face plate it to eliminate the synchros and make for very quick upshifts, you would need to perfect double clutching to down shift though.

Gear strength with any of the stock boxes is marginal. We've had good luck with the Redline Shockproof in allowing the gear set to live. It's just not very synchro friendly, IMO.

this is super cool and would have helped me on a billion occasions. what is it called and where can i get one?

what are those made of? is that a hollow threaded tube? or are those ends just welded on? what are those ball joint things/where can i get em? im looking for them to make a torque brace..

asweoms build man. everything is incredibly impressive. im assuming youre using aluminum for all the fuel related stuff? tig? mig?

:icon_tup::icon_tup::icon_tup:

Can help with one answer. Those are Rod End Bearings. Also known as Heim Joints or Rose Joints.

the first tool is called a contour gauge.

all those braces are a solid 1" aluminum round stock drilled and tapped then welded onto a hollow aluminum tube.

what happened to this build?

Looooooooong story.

Cliffnotes: A masters program + Internship is a lot of work with less then stellar benefits to put towards car. Car moved to the coast and is being built for a different class.

No updates, or at least some closure?

nice work

The car is no longer an E-production build as Farberio said. I have been searching for a shop to put all of my fabrication tools. Currently, the car and the tools, are in storage. I have definite plans of finishing it, but need a place to work on it.

I moved to Charlotte, NC after getting my master's degree for a job down here. I have rotors from Carlos Lopez on the way, and am working on a design for an integrated variable length intake and slide throttle assembly, complete with CFD analysis to optimize the intake plumbing.

My build is being changed to a general track car, but that allows me to do this cool stuff with the intake. I have nearly completed the roll cage, but can't weld it at this point in time due to the work space constraints listed above. The new plans with the car are as follows:

-Dry sump
-10,000 RPM and associated mods to achieve this
-Ceramic apex seals
-CLR Racing rotors - scalloped, balanced, clearanced, and lightened 9.7:1 rotors
-A better transmission - either synchronized or dog-ring will do. Since I don't plan on racing this car anymore, I think I would prefer a synchro box due to ease of shifting and less maintenance. Does anyone know of a synchro box that can shift at 10,000 RPM? S2000 or Rx8 series 2? The associated issues with mating an s2000 transmission to a rotary can be overcome.
-Variable Length intake
-Slide throttle assembly
-Semi peripheral ports - Defined Autoworks has had awesome results from this setup on their 3 rotor, so I see no reason not to use it
-Drive by wire, mostly for better control of staging in the semi-peripheral ports seamlessly
-Custom data logging system... a couple guys at work have built one using an arduino board and I plan on following their lead on this one
-Custom controller for the drive by wire and variable length intake system. Hopefully to be integrated with the standalone engine management and datalogger.
-The suspension will likely stay as it is for now, but custom control arms, both front and rear, will come down the road. I currently have CAD data for the rear control arms since I took those to a coordinate measuring machine a few years back. Once I collect data on tire temperatures, this may be useful. Perhaps the only thing that needs to be done is to lighten them up? I'm not sure I can engineer better suspension than Mazda did, however.

That about sums it up for now. Sorry for keeping you guys on hold for a couple years.

Attachment 689111

This turned out to be a bust. It was a piece of junk. I'm going back to the factory setup; I already have a replacement steering column.

lad to see the car wasnt jut given up on

Keep at it! It's turning out to be quiet the project.

Guys, its been over a year since I did anything on this. I'm just getting back to her again. Here's the story:

-Had to finish my Master's degree, write my thesis, defend, etc.
-Got a job in North Carolina as an aerodynamicist using my degree in Aerspace Engineering and my focus, Computational Fluid Dynamics, for Pratt and Miller Corvette Racing. Awesome job.
-When I moved, I didn't know a single person here, especially one with a shop (props to GTORX7 for helping me out when I lived in Ohio!). Hence, the car and tools went into storage.
-Finally, I decided that I could rent 3 single car garages in my apartment complex and set up a fab shop in one, the car and toolbox in another, and use the third as storage.
-I decided that I'm not moving forward with building the car to E-Production rules. I recently ran a ChumpCar race, and while it was fun, I'm more into track days. If I feel the need to wheel-to-wheel race, I can always rent a ride with some work buddies running ChumpCar.
-Because I'm no longer planning on E-Production, I can now build the car as I see fit. So, I've decided to do several things:

(1) Build a more integrated (somewhat heavier than E-Production) roll cage. This will primarily be to increase the vehicle's torsional rigidity.
(2) I bought CLR racing rotors: lightened, balanced, race clearanced, and scalloped. With this, I plan to rev the engine to 10,000 RPM. All necessary systems must be upgraded, including dry sump, ceramic apex seals, and hardened stationary gears. The primary focus with the high rev limit is to increase power according to the power equation: HP = Torque * RPM / 5252. Keeping peak torque constant, power rises linearly with RPM. Obviously, the work is in achieving the same peak torque at a higher RPM as you can at a lower RPM.
(3) The power increase will require a shorter intake manifold. However, I am interested in making a variable length intake manifold to increase torque at lower RPM ranges, without sacrificing peak torque at the designed peak torque RPM. This will be integrated with a slide throttle assembly to reduce (eliminate) energy losses in the flow across the throttle valve at wide open throttle.
(4) Because I don't have to run E-Production rules, I can now run a radiator vented through the hood. This causes a considerable increase in front down force, and one does not want more down force in the front than rear. Therefore, I need to do aerodynamic analysis on the vehicle to aerdynamically balance the car. I am not shooting for GT car levels of down force; rather, I want a balanced vehicle. Think along the lines of skirts, a diffuser, and a small spoiler, or wale-tail. No wings with airfoil cross sections.
(5) I am still retaining the E-production wide body kit, because I like the way the AWR kit looks, its well made, and I already own it, ha! I don't want a giantly-wide car.
(6) Again, because I don't have to follow the E-Production rule set, I can put 17" wheels on the car, for appearance, availability of tires, and to fit larger brakes under the car to accomodate the higher horsepower realized by the engine that does not have to follow E-production rules. Balance is the key here, not to put huge brakes on it. But 17" rims on an FC look good.

Anyway, I'll be posting pictures of my garage set up first, and then some pics of the roll cage. I have made progress on it since I last posted. I owe you guys some pics :-P

:( is all I have to say

Wow awesome build so far! Im in Charlotte as well. Good to see another rotorhead around here!

I should probably rename the thread and put some updates up. I have some exciting advancements on the intake and throttle bodies!

Seth