The Official "RX8 in DSP" Thread - Page 34 - RX8Club.com



RX-8 Racing Want to discuss autocrossing, road-racing and drag racing the RX-8? Bring it here. This is NOT a kills/street racing forum.

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Old 03-02-2018, 05:27 PM   #826  
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FINALLY getting the chance to revisit the RX8 a bit, got distracted racing motorcycles...

Got the thing painted (not to shabby if I say so myself), and I think I have given up on keeping the battery in the engine bay. Anyone have any suggestions for a good battery post setup for under the hood? I'd like to have the cables running to the trunk mounted in an appealing way in the front.

Also, I stumbled upon a cheap set of FCM coilovers I think I am going to pick up and get Shaikh to rebuild/revalve... A close friend has been absolutely swearing by the customer support and willingness to work towards custom setups at Feal though, and that would cost less than the revalve/rebuild on the FCMs.

Too many things to consider...
For the battery, cut off the stock positive clamp in the engine bay and crimp / solder / shrinkwrap on a junction to re-route that wire to wherever you want it in the trunk. You could also remove the stock positive wire from the wiring harness and re-wire it with a dedicated line if you don't want to use a junction. I did this with my STS build years ago and got clarification it was legal so it would be fine in Street Prepared. Unless you really like having a battery post setup in the engine bay. Wire the negative in the trunk with a short wire between the battery and the unibody. Just be careful when you wire in the ground to make sure the engine (starter) has a good 1-2AWG ground to the chassis in the engine bay.

For the coilovers, I don't know if you saw this or not but there is a set of Penske 8300 DA (remote) dampers on Miata.net for sale. The guy is asking $1750 shipped. The springs are wrong, and they would need to be revalved (they have linear/linear valving) but that's a steal for a set of good shocks, and the double digressive valving is not expensive. Maybe you can even talk him down. I just bought a set of Penskes for $1800 shipped and felt it was a good price...
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Old 03-02-2018, 06:01 PM   #827  
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For the battery, cut off the stock positive clamp in the engine bay and crimp / solder / shrinkwrap on a junction to re-route that wire to wherever you want it in the trunk. You could also remove the stock positive wire from the wiring harness and re-wire it with a dedicated line if you don't want to use a junction. I did this with my STS build years ago and got clarification it was legal so it would be fine in Street Prepared. Unless you really like having a battery post setup in the engine bay. Wire the negative in the trunk with a short wire between the battery and the unibody. Just be careful when you wire in the ground to make sure the engine (starter) has a good 1-2AWG ground to the chassis in the engine bay.

For the coilovers, I don't know if you saw this or not but there is a set of Penske 8300 DA (remote) dampers on Miata.net for sale. The guy is asking $1750 shipped. The springs are wrong, and they would need to be revalved (they have linear/linear valving) but that's a steal for a set of good shocks, and the double digressive valving is not expensive. Maybe you can even talk him down. I just bought a set of Penskes for $1800 shipped and felt it was a good price...
That is a good deal on the Penskes! After getting them reworked and all I'd probably blow most of my budget for the season just on those though... At this point it looks like I can get the FCM setup for around $2600 with new springs and revalve... I'm honestly not sure what the better option is.
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Old 03-03-2018, 08:05 AM   #828  
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I doubt you'd be into the Penskes for much more if anything, and they are worlds better than the FCM setup.
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Old 03-03-2018, 09:21 AM   #829  
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That is a good deal on the Penskes! After getting them reworked and all I'd probably blow most of my budget for the season just on those though... At this point it looks like I can get the FCM setup for around $2600 with new springs and revalve... I'm honestly not sure what the better option is.
Looks like for those Penskes, there isn't any front top hats. Believe it or not, the ND uses the same top hat bolt pattern as the NC/RX-8 -- so I bought a set from SakeBomb and had a friend bore out the spacer for the Penske 12 mm shaft.

Send those off to Ankeny or Anze and have them revalved -- of course, driver preference on spring rates. I'm sure they'd be willing to give their input as well.

If not, I'm fairly sure I can find someone locally who'd be willing to buy those, if you're not.
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Old 03-03-2018, 09:59 AM   #830  
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Looks like for those Penskes, there isn't any front top hats. Believe it or not, the ND uses the same top hat bolt pattern as the NC/RX-8 -- so I bought a set from SakeBomb and had a friend bore out the spacer for the Penske 12 mm shaft.

Send those off to Ankeny or Anze and have them revalved -- of course, driver preference on spring rates. I'm sure they'd be willing to give their input as well.

If not, I'm fairly sure I can find someone locally who'd be willing to buy those, if you're not.
Do you happen to know a ballpark price on revalve/rebuild for Penskes? I honestly hadn't even researched that since they were 'not agreeing with my wallet'.

Finding top hats should be TOO hard I would think.
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Old 03-03-2018, 12:25 PM   #831  
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Do you happen to know a ballpark price on revalve/rebuild for Penskes? I honestly hadn't even researched that since they were 'not agreeing with my wallet'.

Finding top hats should be TOO hard I would think.
Give Anze a call. Or call Sam Strano, he has a guy relatively local to him that can service them. Any of the major shock vendors can do penskes, the parts are relatively cheap.


Before you buy top hats, verify the shaft diameter. There are a bunch of options.
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Old 03-03-2018, 10:18 PM   #832  
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Do you happen to know a ballpark price on revalve/rebuild for Penskes? I honestly hadn't even researched that since they were 'not agreeing with my wallet'.

Finding top hats should be TOO hard I would think.
Anze has a price list:

https://anzesuspension.com/wp-conten...Price-List.pdf

Looks like 1060 for a set of 4. Probably budget about 75 for shipping both ways, and an extra 150 for consumables (I'd replace the spherical bearings in the rear shocks).

And John is definitely right about figuring out what the shaft stud diameter is -- I swapped my rears out for the 10 mm (but they're $$$, bought separately).
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Old 03-04-2018, 09:36 AM   #833  
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I would give up other parts in the budget and spend your money on good shocks. They are the #1 thing we did to my car. Next was having Jeff H help us dial them in

Also, you can run them with the stock front top hats. It's not ideal (some side loading) but we did for awhile. We now have spherical top hats front and rear.
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Old 03-05-2018, 05:51 AM   #834  
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For the battery, cut off the stock positive clamp in the engine bay and crimp / solder / shrinkwrap on a junction to re-route that wire to wherever you want it in the trunk. You could also remove the stock positive wire from the wiring harness and re-wire it with a dedicated line if you don't want to use a junction. Wire the negative in the trunk with a short wire between the battery and the unibody. Just be careful when you wire in the ground to make sure the engine (starter) has a good 1-2AWG ground to the chassis in the engine bay.


I have a very similar setup; bolted a positive lead to the OEM positive terminal in the engine bay, re-grounded all of the negatives to the front chassis member behind the fans, ran the positive lead to the trunk, ran a short negative chassis ground from the negative terminal.


BUT, i did not make any changes along the lines of "Just be careful when you wire in the ground to make sure the engine (starter) has a good 1-2AWG ground to the chassis in the engine bay". How is the factory starter grounded, and/or why is it good to improve this ground? I am having somewhat slow cranking and i assume this could be contributing. Is the old starter ground connected directly to the battery negative?
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Old 03-05-2018, 06:58 AM   #835  
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Unless I'm mistaken, the starter is grounded through the engine/transmission.

I think John's point is that you need to make sure that the grounding wires between engine and chassis are in good shape if you connected your negative battery terminal to the chassis.
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Old 03-05-2018, 08:26 AM   #836  
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Unless I'm mistaken, the starter is grounded through the engine/transmission.

I think John's point is that you need to make sure that the grounding wires between engine and chassis are in good shape if you connected your negative battery terminal to the chassis.
Yes, the point is you need a cable that can carry the return current from the starter to the battery's negative terminal.

Most cars have the negative cable from the battery connected directly to the engine, so any ground wires from the engine to the transmission are relatively small (high numerical gauge) wire. If you relocate the battery to, say, the trunk, you need to add a high current (low numerical gauge) wire between the engine and the unibody.

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Old 03-05-2018, 08:14 PM   #837  
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I searched the thread but didn't see any discussion about motor and diff mounts. Has anyone had success eliminating wheel hop from launching on Hoosiers?

I found the following motor mount options:
- RX8Performance $265 aluminum 70A poly
- Black Halo Racing $395 aluminum ?A poly
- Race-Roots $200 stainless ?A poly
- Megan Racing $307 ?metal 70A rubber

Here are the differential bushings I found:
- Whiteline $36 ?A poly
- Powerflex Purple/Black $77/86 80/95A poly (street/race)
- Superpro $69 70/80A poly (street/race)

I'm sure I've missed some. Is 70A durometer enough to control things in the rear?
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Old 03-06-2018, 06:00 AM   #838  
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Doing solid (Delrin / Aluminum) bushings in the subframe and diff of the BMW cured all the wheel hop issues. I would expect the same is true of the RX-8.

Polyurethane is not a good bushing material and IMO should never be used. For anything.
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Old 03-06-2018, 07:26 AM   #839  
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Quote:
Originally Posted by gigglehurtz View Post
Looks like for those Penskes, there isn't any front top hats. Believe it or not, the ND uses the same top hat bolt pattern as the NC/RX-8 -- so I bought a set from SakeBomb and had a friend bore out the spacer for the Penske 12 mm shaft.

Send those off to Ankeny or Anze and have them revalved -- of course, driver preference on spring rates. I'm sure they'd be willing to give their input as well.

If not, I'm fairly sure I can find someone locally who'd be willing to buy those, if you're not.
BTW, I was referring to these:

https://forum.miata.net/vb/showthread.php?t=660886

And they look to have top hats included.
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Old 03-06-2018, 01:35 PM   #840  
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Doing solid (Delrin / Aluminum) bushings in the subframe and diff of the BMW cured all the wheel hop issues. I would expect the same is true of the RX-8.

Polyurethane is not a good bushing material and IMO should never be used. For anything.
I was hoping to avoid going that stiff since my car will be street driven. I don't believe I've experienced driving a car with delrin diff bushings before, though. Is it a perceptible vibration or just more of a noise thing?

I see that RX8 Performance offers both Delrin diff bushings and aluminum subframe bushings, with a $50 option to have the diff bushings installed (+$150 core). I wish I had noticed that before I bought a spare diff carrier.
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Old 03-06-2018, 07:46 PM   #841  
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I was hoping to avoid going that stiff since my car will be street driven. I don't believe I've experienced driving a car with delrin diff bushings before, though. Is it a perceptible vibration or just more of a noise thing?

I see that RX8 Performance offers both Delrin diff bushings and aluminum subframe bushings, with a $50 option to have the diff bushings installed (+$150 core). I wish I had noticed that before I bought a spare diff carrier.
This is SP. Make your own. :D
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Old 03-12-2018, 09:46 AM   #842  
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This is SP. Make your own. :D
I thought SP was the original bolt-on class? :-P
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Old 03-12-2018, 10:21 AM   #843  
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We made delrin diff bushings. They did help the wheel hop some, but it's still there just reduced. We did a mix of poly and delrin suspension bushings everywhere - some of them in the rear are slight compliance bushings so we were a little worried about going delrin (and also the front lower rear control arm is definitely a compliance bushing, so we kept it OEM). Our engine mounts we DIY filled the OEM ones with 90A poly (I think). Not sure that's the best solution but it was better than OEM. We are still on stock subframe bushings - maybe we should consider swapping them for something stiffer.

We found messing with shock settings could actually dial out some of the wheel hop too.
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Old 03-12-2018, 11:31 AM   #844  
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I thought SP was the original bolt-on class? :-P
I was just being snarky. Bushings are usually pretty easy to make and you can typically save a lot of money making your own. I made mine because at the time the available aftermarket solutions were not legal for SP. Rules have changed since then.

To answer your question about NVH, yes, delrin / aluminum bushings definitely increase NVH. With the BMW, the first thing I did was the delrin engine mounts (because the car came with a broken engine mount and I needed something fast), and that increased NVH dramatically. When I made the subframe and diff bushings a year later I didn't notice that it really made much of an NVH change, but all the wheel hop went away.

Polyurethane is a terrible bushing material. I usually recommend to people that are considering poly because they don't want a lot of NVH to just use stock rubber. It's just better in every way.
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Old 03-12-2018, 06:59 PM   #845  
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I'm still on the hunt for suspension things... stumbled across these: eBay Penskes

Looks like having Anze rework these could be a very cost effective option.
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Old 03-12-2018, 07:20 PM   #846  
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I'm still on the hunt for suspension things... stumbled across these: eBay Penskes

Looks like having Anze rework these could be a very cost effective option.
Those are the same ones I linked here a week ago
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Old 03-12-2018, 07:52 PM   #847  
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Those are the same ones I linked here a week ago
I think I'm losing my mind...

The one thing I was looking forward to with FCM was not having to worry about the spring rate/bump stop/sway bar decisions since he has experience with the chassis, going with the Penskes means I'll be doing a bit more testing and playing with it.

Would anyone be willing to divulge their numbers on here?
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Old 03-13-2018, 04:39 AM   #848  
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Sam at Stranoparts can help you out with rates, and hook you up with the springs and bars as well.
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Old 03-13-2018, 08:33 AM   #849  
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I think I'm losing my mind...

The one thing I was looking forward to with FCM was not having to worry about the spring rate/bump stop/sway bar decisions since he has experience with the chassis, going with the Penskes means I'll be doing a bit more testing and playing with it.

Would anyone be willing to divulge their numbers on here?
Unfortunately since the RX8 is still being developed for DSP there's no known hot setup that everyone can default to. I'm not sure if the STX thread divulges setups more, but you could probably take it and just stiffen everything up a little to account for the higher grip, and that would get you ball park. I believe Monnar discloses his spring rates and other info on his website, for a DSP idea.

Also, each driver can have very different preferences, so what works for one may not work for another. For example, we don't run bump stops - our spring rates are stiff enough and we have enough shock travel that we never bottom them to need them (our shocks were custom built for our setup, most shocks need bump stops). Sam Strano tends to run softer setups that use bump stops I believe, and it obviously works very well (JV's car, for example). I'm sure Sam could help you a lot if you want to take that approach.

Also, aero vs no aero changes the setup quite a bit. We had to stiffen the rear a lot once we added the rear ducktail. Keep that in mind if you look at STX setups as a starting point, since they don't run aero.
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Old 03-13-2018, 03:53 PM   #850  
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For anyone interested in more details on our build, Mazda Motorsports asked me to do a writeup on the basics of how to build a DSP RX8, including costs. The article outlines all of the parts on our car and the steps we took to make it competitive. I know some of you guys are still early in the development stage, so hopefully this may be helpful.

The only part not mentioned was the lightweight clutch, since the original manufacturer didn't work out like we hoped. We should know on the new one by early April once events get started again. A lightweight clutch did do wonders for our car though, when it worked.

https://www.mazdamotorsports.com/201...d-tips-budget/
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