ABS disabled
 

I did a shake down with the car at the track this weekend. I have the ABS disabled. I found under hard braking the front brakes would lock very easily. No matter how i tried to modulate the brakes they would lock.
Anyone ever run without the ABS system and have this problem?

Yes. I'm chasing other brake problems so I am hesitant to attribute it all to the ABS absence but modulation prior to ABS engagement is harder without ABS and fronts lock easily.

ABS systems in modern cars are one of the ways the manufacturers control brake bias.

Why would you disable the ABS?

Because I am allowed to be 56 pounds lighter without it.

56 pounds? That sounds like a really bad tradeoff.

Not really. Very little time is gained under braking and most of us can threshold brake as well as ABS. Maybe a different story in the rain but baring a lock-up there's not much ABS advantage when it comes to lap times. 56 pounds though (2% of total weight) pays off in corners, under acceleration, and under braking so pretty much everywhere. When races are usually won by less than a car length, it matters.

I'm having trouble resolving your two statements. On one hand, you can threshold brake as well as in a car with ABS. On the other hand, you're apparently having problems with the fronts locking.

I'd postulate that some drivers can brake as effectively without ABS as they can with ABS... but that none can do so in every braking zone, on every lap. One mistake is all it takes to throw that miniscule (56 pounds) advantage out the window.

Sorry for the confusion But I originally posted the problem with the front brakes locking up. Then Adax also posted a reply.
To answer your question why I was running with the ABS disabled I damaged the rear sensor cable when replacing the rear clip. I thought I'd give it a try to see how it ran without the ABS but without the ABS system the hard braking was extremely bias toward the front. For me, I would need to install a proportioning valve or fix the ABS system. I'm inclined toward fixing the ABS. The weight is not an issue with me.

Sorry, for the latter post I should have said "in general". True, if I can't get front bias worked out otherwise it will be better to keep ABS. If it gets sorted, I'd rather give up the weight. One of the many things in "development".

AC

56 pounds, over 20 kg, you are dreaming mate, try about 18 pounds.
ABS Module, bit of wiring, and a tiny bit more of hydraulic line is not close to 25 KG.

No, the rules in the class I race the car in permit a 2% weight reduction if the ABS is disabled.

Sorry for all the confusion I've caused.

AC

Without the ABS you just have single channel brakes. RX8s have Electronic Brake Force Distribution so you'd need to add a proportioning valve.

i feel like my car has too much rear brake bias with abs on. it feels like the rear abs kicks on when i threshold brake. im running DTC60 front and DTC30 rear

I would hope the ABS would engage when you threshold brake. That's kind of the point.

I'm saying it's too much rear bias, so if the abs wasn't working, the rear would lock up and I wouldn't be able to threshold brake without flat spotting rear tires.

Try DTC-15 or -5 if they still sell those?

I agree. You're trading a maybe a couple tenths of performance for consistency under braking and the margin of safety ABS provides.

There seems to be some suggestion in this thread that the ABS system does a fair bit of proportioning front to rear. I wasn't aware of that, if true.

Well just to summarize, the braking system from the factory has no mechanical brake bias other than the master cylinder and caliper piston sizing with the ABS system electronically providing the rear bias (called EBD, see attachment at bottom of this post) as dictated by the wheel sensors. It’s one of the reasons I generally recommend using the same brake pads front and rear; the ABS system will just work against that to tune any forced bias out, at least within it’s adjustment capability range. So you can’t just disable it and expect to have proper bias. Other changes are required to compensate for removing the programmed electronic balance.

it seems like the rx8 asb engage ice mode much easier than in my Evo. so far in 5 races with the rx8, i've hit ice mode 3 times during race. i tracked the Evo for 8 years and only engaged ice mode once, when i hit the brakes while the tires was still off the ground from a jump.

problem with using same compound front and rear and relying on abs to control the bias is that you still have an uneven bias during non threshold braking. like during trail braking where you're not on the brake at full force, so the abs is not engaging to control the bias. and you'll end up with too much rear bias.

on my Evo, i had too much rear bias for my driving style, that i end up using high performance street pads for rear and dtc70 for front. on my rx8, im now running dtc60 front and hp plus rear, and it still have too much rear bias. i can feel the rear abs engaging before the front. and during trail braking, when the rear abs comes on, the rear will snap out unpredictably.

Is your abs working with the Adaptronic ECU? if so, what ABS controller are you using? Mine will not work with either manual/stabilty control or auto/stability control ABS controllers. Plan to contact them Monday.

AC

ABS related ... I've searched and cannot find definitive info just a bunch of conflicting back and forth. I just built an engine swapped RX8 for time trial and hill climbs and I want the ABS to work. I've read that the ABS can run stand alone all it needs is power and wheel speeds. Wheel I have power and wheel speeds but the ABS wont work. I'm running no factory Mazda PCM or modules at all except for the ABS unit. It was a DSC car but the DSC sensors have been removed. I did keep the stock dash harness intact although I dont use it for anything but plugged it in and at least got an ABS light. Just ordered a fancy ABS code reader so hopefully that will help.

The only fact I know is a member here broke his steering angle sensor and it disabled DSC/TCS but kept ABS alive. This is why I removed the DSC sensors and wiring but kept the ABS sensors.

I've read it has to have signal from the PCM to work and I've read it doesn't. Dont know where else to look and so am asking if anyone has successfully run the factory ABS as a stand alone system?

Thanks
Cameron

From a US Racing prospective TEAM (Mark) is the man who knows.

I am pretty sure you are chasing your tail trying to change or disable/modify Brake Bias rear or front, unless you can FFF0 FFFX, code write save etc with the correct dump/write interface.
ABS was and is standard equipment on All RX-8's sold, only some early models had DSC as 'feature option' that then became mandatory standard equipment from about 2005 MY onwards.

Mazda still uses Ford IDS system, but is now separated for the past 4 years.
But the issue as I see it is how do you prevent the PCM/ECU from hand-shaking/communicating with ABS, IC, SRS AB, DSC modules as they all speak to each other and hold event data, writes and holds DTC's and if events are serious enough can or will put car ignition into limp home mode, when warnings are ignored, max speed is limited to a crawl.

I could be wrong but I am pretty sure to 'control' all of these modules effectively you have to abort/remove All of the OEM Mazda equipment and then install a proven aftermarket control system,

Just throwing this out and not new but would 'inserting' a brake fluid restricting orifice devise on the front hydraulic brake lines create the rear brake bias desire you want, without any major electronic module changes, and would it be race legal?

I am running a haltech standalone and am having the same issue with no abs. Unfortunately the abs computer seems to run the speedo on the factory dash. I have plenty of spare outputs I could use to trigger to abs module if its that easy. I feel like they were talking over the CAN bus though. The haltech has CAN support for NC mx-5's so that is running my tacho and temp gauge, I still get an abs light and the dsc squiggles.

I'm certain the ABS system will not work without CAN communications from either the stock ECU or a stand-alone. This is possible with MoTec and Adaptronic stand alones, although currently only one person has it working with MoTec to my knowledge, and Adaptronic only works with manual trans, no DSC ABS units currently.

Also read this thread.

https://www.rx8club.com/series-i-eng...ec-ecu-265467/

Do you have a facespace account? The "LS Powered RX8" group is a pretty good body of knowledge.

Well that really sucks. Any possibility one could wire in the stock ECU just enough to make the ABS work - power, ground, whatever wire that signals the ABS? Alternately has anyone found an aftermarket ABS to integrate with the Mazda speed sensors and such?

A lot of V8 swap guys do this.
They keep the RX-8 ECU in place to operate the OE dash and such. Many put the ESS tone wheel on the crank for RPM measurement to keep the factory EPS system running.
I know some other have tried to emulate the ECU's CAN signals with an Arduino or RPi but CAN messaging information is somewhat scant so not all functions can be emulated this way.

IIRC, Touge Factory near Chicago built an LSX RX-8 that looked and functioned nearly identical to stock. Jason Saini brought it out to an autocross event and I got a ride in it (total BEAST!). I don't know if it had functioning ABS (and Jason's a good enough driver that I couldn't tell) but I think it had functioning ABS. You might want to see if Touge Factory or Jason can/will do some consulting to get this issue solved.

We've gotten CAN functionality working through Megasquirt on the BMW, so I'm hoping we can get the same working on the RX-8. I would definitely not want to run a stock ECU...

Anybody try this setup?
 

Just bought an RX-8 for E Production in SCCA. I'm looking to loose weight and the harness is 28 pounds. This looks promising but I'm wondering if anybody has used it.

• https://www.compbrake.com/wp-content...B1-200x200.jpg
• https://www.compbrake.com/wp-content...OX-200x200.jpg
• https://www.compbrake.com/wp-content...OT-200x200.jpg
• https://www.compbrake.com/wp-content...IR-200x200.jpg
• https://www.compbrake.com/wp-content...IR-200x200.jpg
• https://www.compbrake.com/wp-content...IR-200x200.jpg
• https://www.compbrake.com/wp-content...ER-200x200.jpg
• https://www.compbrake.com/wp-content...LY-200x200.jpg
• https://www.compbrake.com/wp-content...LE-200x200.jpg
• https://www.compbrake.com/wp-content...GS-200x200.jpg
• https://www.compbrake.com/wp-content...R1-200x200.jpg

MAZDA RX8 BRAKE BIAS SERVO REPLACEMENT PEDAL BOX KIT – HYDRAULIC DUAL AP CYLINDER [KIT B

Thanks,

Steve

The easy button for ABS is just to convert the ABS module to one from a non-DSC car. Then you have standalone ABS that doesn't require the factory ECU.

is this a common swap? i many have to look into that.

Probably not, but non-DSC cars are not exactly uncommon and it sure makes swapping different engines / engine management systems a lot easier than starting with a DSC car.

that's some good info, thanks.

SCCA E Production rules
 

Unfortunately, the rule book does not allow ABS at all. I'll be the first one in and let everybody know how it works...I'll be at Hallet in Jennings OK the last weekend in March, then VIR the second weekend in April.

I think I may be the 1st to have an S-5 13b in an RX-8....If anybody knows anybody else, please let me know.

Thanks,

Steve

FWIW, I bought the COMPBRAKE setup out of England, $550 USD included shipping. It arrived within a week.

Won't be driving until late March but I will get back on quality of parts, installation notes, and on track performance.

Steve

I will be very interested to hear your thoughts. The ABS/EBD system in the RX-8 has a pretty terrible failure mode, but it's so magical under braking that I am loathe to remove it.

I tried running without ABS at thunderhill track and the rears would lock up before the front under heavy braking. I actually spun under braking. With the ABS back on and it was much better.

I know this is an old thread but I've been looking for that easy button. I'm trying to convert. Do i need to convert the entire harness as well? Or can I just cut off a pig tail and wire it in? The Bosch plus is completely different then the Sumitomo that I'm switching to. I heard that the hard lines are a little different as well but i can work around that,

FYI I'm buying the Sumutomo unit off eBay and no one will sell me the pig tail so I'm going to cut one off a Mazda 6 at a pull a part and unpin it.

You don't need to convert the entire wiring harness. Buy the non-DSC pigtail and wire it in appropriately. You will have to change the flare fittings (or adapt them) at the ABS unit.

Amazing news thanks John, Is there a wiring diagram available. I feel like I've seen them before but can't find it for the life of me. I have access to all the books on line but can't seem to find it. Is it a hidden menu in the TM that I'm overlooking?

Matter of fact I know they exist because used it to make to make sure that I have the correct plug to the correct coil..

I used the sumitomo abs on my swap. Wiring is straight forward if you have the pigtail from the donor. Match color to color and and an additional 12V power wire.
Link to Service Manual
13 electrical (Pages 122-127) for the diagrams
I couldn't find anywhere to buy the connector on its own; fortunately I found one that came with the pigtail.
An option would be to buy the right terminals (I believe they are Sumitomo TS 90 and TS 187,) crimp them to some wires, plug the terminals into the socket and use an epoxy potting compound to retain them. Then use a deutsch connector or other connector of your choice to make your connection to the RX8 harness.

The Bosch DSC unit uses 6mm lines with bubble flares and m12x1.0 tube nuts; DSC equipped cars also have a master cylinder that use m12 bubble flare fittings.
The Sumitomo unit uses 4.75mm lines with inverted flares and m10x1.0 tube nuts; non-dsc equipped cars have a master cylinder that uses m10 inverted flare fittings.
Lines to the wheels are 4.75mm on both DSC and Non-DSC, but are bubble flare on the DSC and inverted flare on the Non-DSC.

The master cylinder is identical between DSC and Non-DSC besides the the size of the fittings. You can either use adapters or swap to a non-DSC master cylinder
You'll need to re-flare the lines to the wheels or use an adapter.

There is another option, although more expensive.
The Bosch DSC MK60 abs from a BMW M3 can be retrofitted.
It's similar to the DSC in the RX8 but a bit more advanced, and it does not need to have the RX8 ECU functional to work. A good choice if you have to an aftermarket ecu or swapped powertrain.
It's becoming popular for retrofitting older cars to more modern ABS/DSC as well as a substantially cheaper alternative to a motorsports ABS unit like a Bosch M4 or M5.

@Stubbs
Thanks for that detailed reply you hit everything. I believe the Mazda 6 used the same gen Sumitomo abs pump and there everywhere at my pull a parts. I just wanted the wiring diagram incase they used different wire colors in the 6. I haven't had any luck finding a cut Sumitomo pig tail from an rx8.

Looking at the connectors you listed they look to small, there 2 pin connectors. Unless I'm miss understanding what you're explaining. https://www.corsa-technic.com/catego...ategory_id=228

As far as the lines go, with my car being a DSC model and them being 6mm do I need to replace all of the brake lines since the Sumitomo uses 4.75mm? I guess in my mind I was just going to un-flare swap tube nuts and re-flare at the pump and just be done. I'd love to avoid redoing all the brake lines if at all possible but it could be a good learning experience.

Provided I can keep the lines could I just put adapters on for the pump side? Example
I have seen the MK60 option which looks awesome, but at $1000 + Pump + 4 new sensors its getting expensive and for endurance racing I need to get a fuel cell before that and just don't have the budget currently. Technically everything works I'm just looking to throw my Haltech in for better engine management that I have sitting.

Thanks for taking the time.

The adapter you linked should work to adapt the DSC master and 6mm lines to the Sumitomo abs.
You'll need m10x1 bubble female to M10x1 inverted flare male to adapt the 4.75mm lines going to the wheels.

One thing you'll need to confirm is if the flares on the Bosch DSC are SAE bubble or DIN/ISO bubble. SAE and DIN/ISO are both bubble flares, but they have some differences. I believe they are interchangeable but I'm not certain. Bosch, being euro, is likely DIN/ISO.

The terminals I mentioned (These: TS 090 and TS 187) are the contacts that make the connection, not the connectors themselves. Essentially you are creating a permanently affixed pigtail off the abs module so you can use a new off the shelf connector to make the connection to the RX8 wiring. It's a solution if the correct connector can't be sourced.

However, if the Mazda 6 has the right connector and is readily available then that's the better choice.

Looks like I’ll be doing a DSC to non-DSC conversion on a 2004 RX8 in the (hopefully) not too distant future and will document my experience in this thread. The DSC vehicle currently is defaulting off on DSC-ABS. I’m hopeful that the swap will resolve that and there aren’t other issues, but won’t know until then.

Not having ABS is bad enough, but 500+ whp coupled with front brakes that default to ice mode without too much braking load is not an ideal situation. Down right unnerving is how I’d describe it. The plan is to try and de-pin the wires from the DSC wiring connector and swap the appropriate ones into non-DSC connector rather than splicing them.

The terminals from the DSC connector housing aren't compatible with connector housing on the non-dsc housing.
The DSC connector terminals are TE/AMP Junior Timer series(first picture.) The Non-DSC connector terminals are Sumitomo TS series (picture 2 and 3 are TS 090 sealed, 4 and 5 are TS 187 sealed.
They are different form factor and the retention is opposite (TE retention tangs are on the terminal, Sumitomo retention tang is in the connector housing.)

If you don't want to splice you can order the terminals and seals for the Sumitomo connector, de-pin the DSC connector and cut the old terminals off, and crimp the new ones on. The harness should have enough length.
https://cimg4.ibsrv.net/gimg/www.rx8...151a93bf95.jpg
https://cimg5.ibsrv.net/gimg/www.rx8...0c7d9841e6.jpg
https://cimg5.ibsrv.net/gimg/www.rx8...6e29a5036b.jpg
https://cimg8.ibsrv.net/gimg/www.rx8...39f314c9a2.jpg
https://cimg2.ibsrv.net/gimg/www.rx8...7f38d26746.jpg

waaa, schooled by the master :worship: and much appreciated.

thank you for saving me the time. I’ll just buy the correct pins and cut/crimp them in instead. :)

.