AWD Speed 3 Project - Halfmilespeed3

so which is a better option to go with/ cx7 rear subframe and diff or ms6 rear and diff?

 

I agree s1 has changed the awd drive game for Honda so corksport has been Mazda community go to for parts and would be huge for mazdaspeed platform

a group buy for the custom parts is the way the go to tet the waters but knowing the mazdaspeed community the demand will will be be crazy high. the awd drive swap has been a need for this platform.

 

Possibly, but expecting my guess around $10K to buy because of the involvement of custom pieces. Let's watch the mad scientist do it on his Speed for now.

 

YOU CANNOT USE THE MS6 REAR SUBFRAME...you might aswell jsut fab your own subframe at that point.

The easy solution: Use the CX7 subframe (the inner frame work that bolts to the chassis only). Then use the control arms and trailing arm from your MS3. The rear differential is made up of two sections (the front section holds the clutch pack and the rear section is the gear housing). Externally, the rear section is the same between the MS6 and CX7. The internals are different; LSD vs Open , respectively. The front section is different externally. The MS6 uses a one-sided mounting setup vs the CX7 using a symmetrical two side mounting setup. To bolt directly into the CX7 subframe, you need to use the CX7 front clutch pack section.
NOTE: the differential mounts for the CX7 are unique (fronts and rear) vs the MS6. I am designing my own billet mounts. You may be able to use the CX7 mounts and replace the OEM rubber bushings with poly bushings...?

Honestly, the axles are the biggest ticket items (especially depending on what power level you want to support). Most of the parts are OEM (junkyard sourced for CX7) with just some supporting custom billet parts and rear suspension support.

 

<- Me right now.

 

Is this before or after the "shit everywhere scene" hahahaha

 

Now the "tuning" for the rear diff is a whole different story. OEM ECU vs Motec ECU makes a huge difference and how much control you want. I want full programmable control so I'm going full custom setup. Working in tandem with the Motec, I am investigating a standalone controller from Syvecs that can take in many inputs (4x wheel speed, diff oil temp, throttle plate angle, accel pedal percent, etc...) so that I can tune and create control algorithms for the AWD system. IDK how much the controller is yet, but my guess is around $1000.

 

trailing arms came out nice and looks great

i appreciate the detailed information and you sharing your build with the community. keep up the good work on your build

that's great that the MS6 axle fits the cx7 hub and vice versa. find an axle with the correct left will be the only thing that would be require.
let us know the left with dss axle comes back

 

Another update:
Transmission is still in progress. Have had some difficulties with shims and such, getting the bearing preload setup. If you are doing any trans work or differential change be warned that Mazda is discontinuing the various thickness shims needed for the bearing races. I ordered what I could and also made my own in various thicknesses. Essential stacking thin shims to get to the spec I needed.
This was needed for the Damond LSD especially (nothing wrong with the Damond LSD, but when you are talking 0.002" differences to get bearing preload correct...things are different from one to another)


Shims I designed and had cut by SendCutSend


Per the service manual; There is a torque spec for bearing load of the differential alone then the differential plus the 5/6/R secondary shaft.
I made my own tool to turn the differential as shown with an old axle shaft end and socket welded to it.

 

Another Update:
Rear axles from DSS arrived.

These are "700hp" rated axles per DSS. Doggo approved



Axle fitment is good with lots of length adjustment range for more or less camber than the current -2.5 degrees.
I also opted to have the wheel speed rings placed on the inboard side of the axles so i don't have to fight fitting a speed sensor inside/through the MS3 trailing arms. I will make brackets off of the rear diff mount to mount the speed sensors.
I have ordered speed6 wheels speed sensors for the rear. I will need to change the electrical connector though. It seems the MS3 is unique in its design vs the speed6 and CX7.


The blue part is the final design for the CX7 front diff mounts. Those are in machining now and I should have them in a couple weeks.

 

About those DSS rear axles...


The shaft diameters are different for left and right...this is not by design.

I talked to DSS about this...basically they said its fine and they used what they had available on the shelf from older MS6 production (yes that also means the MS6 rear axles have varied in diameter)...I'm not stoked about it but I need to keep moving forward with the project. They fit well otherwise.

 

If the axles are rated to 700 I doubt the diameter will make a difference since I doubt the rear diff can take 1400 hp but knowing they were different would drive me nuts

 

Ya thats my same logic.

Touching on the power capacity of the rear diff system...I have more hope. Newer cars with this front biased AWD system are using a simple but clever way to be able to apply more than 50% torque to the rear wheels. The rear differential ratio is ~0.7% higher than the front differential. This creates a speed difference that the rear diff clutch pack can take advantage of. Locking the clutch pack 100% results in more than 50% torque going to the rear because of the speed/gearing difference. However, most of the time the clutch pack is not 100% engaged so there is some amount of slippage in the clutch pack happening. This is great from a torque biasing standpoint but the by-product is excessive heat build up...which we've all seen issues reported of such in the Focus RS and Yaris GR.

The Speed6 can only transfer up to 50% of torque to the rear wheels (unless the fronts have no traction which is unlikely) because the differential gear ratios are the same front and rear. This is good because the differential clutch pack can be locked 100% (and is most of the time anyways from the factory) so the heat issue is reduced significantly which will help with strength to some degree.

 

Yea I can't imaging the heat from burning the clutch on the rear diff all the time

 

i think a custom trailer arms and axles would be a good DIY kit to start with which would help customer's