Crap, I think you're right! I was thinking of datalogging the wheel speed sensors which is definitely CAN on AP2v2+

But yeah, I think you're right that "the ABS module handle the raw signals direct from the sensors". Sorry for any confusion.

Looks like AP1 or AP2v1 could be made to work for you application :)

Sorry, bud. Looking at that further it is definitely 3-channel. You're right. I'm still not going to dismiss it at this point however as someone I trust very much swears that it is very well programmed for what it is. The 3-channel on many 90's era cars just pick up rear wheel speeds with one ABS tone ring on the driveshaft near the differential and were junk. At least the S2000 one is monitoring both corners and constantly comparing them?

@DavidNJ I understand the fail safe. Also why all tandem OEM MC's have a wall in the reservoir separating circuits. The diagonal routing happens inside the ABS module so I would plumb things as depicted. Just for the record, I intend to make new lines and route them so this isn't something I just intend to drop in and connect. All OEM tandem master cylinder circuits operate at the same pressure until the rear circuit is proportioned, whether it's mechanical or through EBD. I think the biggest take away is that you just can't have a proportioning done before the ABS module (which a lot of older OEM master cylinders do) because then you would end up proportioning a front/rear diagonal vs rear only. That would be something, eh? lol Maybe circle track guys do some crazy shit like that.

So the pricing I mentioned previously is soup to nuts, with a custom harness where I specify the lengths I need, which those don't include. But, you're absolutely right about trail-blazing vs getting something already done. I just am not convinced the MK60 would give me a $1000 better lap time and consistency than the AP1. Might be more beneficial to use that $1000 for aero and make way with the AP1 ABS.

@shind3 , I actually ended up finding one, but huge thank you! Really appreciate it.

Circle track rules don't allow ABS or traction control. The racing pedals have separate front/rear master cylinders, typically each with its own reservoir. Circle track cars don't run in the rain; there are no circle track rain tires.

The question is how much more of your time will be required with the S2000 vs Mk60 ABS. What else would you do with that time? The other side is what is the probability of finding a problem at an event? How much track time would be lost? Would a better result in the event or a championship be forfeited?

A corollary question: how much faster do you expect ABS to make your car? The knock against street ABS systems is they intervein to early before maximum deceleration is reached. The Bosch ABS has 12 driver adjustable settings. I'm guessing the MB AMG GT4 race cars are using the Bosch because they also have 12 settings. MB has 9 or 12 settings for the stability/traction control on both the street and race AMG GT versions. I don't think that is possible with the Mk60.

I think you took my circle track comment a bit too literal.

As for time to implement, AP1 may have the advantage mostly because of the wheel sensors I can use easily. But, I'll have to wire everything up vs the harness being done for the MK60. Both require new lines and routing to be done.

If the MK60 ABS goes down in a race, I lose EBD/proportioning. If AP1 goes down, it's just how the car has always been, but without ABS. I/we've been threshold braking without ABS for the last 6-8 years so no issue there.

As for faster time, my guess is 1/2 second per minute of lap time in the dry. Seconds in the wet. I'd also be able to put aero on the car with the $1k I save, so the combo of a good 3-channel ABS and aero vs an excellent 4-channel ABS alone will be significant I'd assume.

And it's not only about faster lap time, dealing with traffic in endurance racing is huge. If I can brake a single car length later than now, it'll make a large difference in how traffic can be dealt with; being able to pass people under braking and also not getting passed.

As for Bosch, it would be an amazing system to put in my car. Just need to muster up $8-$10k real quick. MK60 can't be modified to adjust settings on the fly.
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@shind3 , just looking briefly at the AP2 VSA/ABS in the FSM, the only CAN lines it seems are going to/from the steering angle sensor (ECM bridges off of the same lines. TC?), and the "sensor cluster" (lateral/yaw sensor unit). The wheel speed sensors are two wire, + and - inputs, so perhaps they're not CAN? The AP2 system actually has the brake pressure sensors internal to the ABS unit vs the MK60 which are external and need to be plumbed in. Nice!

The MK60 functions without a steering angle sensor which is CAN on that (as well as lateral/yaw and brake pressure sensors). It only needs the lateral/yaw sensor and brake pressure sensors to have complete function ABS with EBD. Hopeful assumption here, but perhaps the AP2 can be made to work in a similar fashion as MK60.

AP2 VSA/ABS circuit diagram for reference:
Attachment 150740
Attachment 150741

Let us know which direction you end up going, though selfishly I hope you try and work out AP2 in stand alone mode because that would be pretty neat to read about :) Also, details on the 240SX. Underrated chassis for trackdays, I'd think. I miss mine.

Ha! Definitely underrated. The biggest issue with the 240 is that it came with a POS engine and most people don't want the hassle of engine swapping. If it came with a better engine in NA it'd be way more popular at the track. As soon as you throw a capable engine in it, it's basically a Japanese E36, almost E46, M3. The dimensions and suspension layout is very similar (without the cracking rear sub-frame issues!).

Don't want to derail too much, but it's an S14 with a VQ35DE swap that I campaign in the American Endurance Racing (AER) series. I have an long build/blog thread that I started on a Nissan forum (click here). That forum has been real quiet of late though so I recently migrated everything to Zilvia, which used to be a shit show, and still kind of is, but the base seems to be maturing some.

Attachment 150662
Attachment 150663

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Like you, I want to try and make the AP2 work because I like doing different stuff (like road race an S14!). I managed to find an MK60 circuit diagram. It is basically the same as the AP2 circuit diagram. They both have the same number of harness pins on the module and the pin numbers basically match up to the T. Then I dug a little deeper and found out that the modules/controllers are identical. They are both made by ATE and the harness connectors are IDENTICAL. The only difference is that the MK60 has external pressure sensors and the AP2 has them internal to the unit.

MK60:
Attachment 150664

AP2(v2) S2000:
Attachment 150665


So, at this stage, there's no reason to believe that the AP2 can't be made to work in a similar fashion as the MK60. I'm going for it.

With that said, does anyone know if the CR edition S2000 had any sort of track or sport map programming for the VSA/ABS? I'm finding that the part number on a standard 2008 S2000 ABS controller is a hair different than the CR edition of the same year. The units are physically identical. I'm hoping that this may be solely a programming difference geared toward track performance, since it is a "Club Racer" after all.

Hey all, figured I'd update this thread.

I ended up going with the E46 M3 MK60 ABS system in the end. I got pretty close to going with the S2000 unit, but there were two things that prevented me from moving on.

1. The S2000 unit splits the 2 line inputs coming from the master cylinder across diagonals on the car. I.e. - input 1 gets split across FR & RL, input 2 gets split across FL & RR. This is actually very common on all modern cars. From a competition point of view, this makes running any proportioning upstream of the ABS module useless. If you wanted to do any rear proportioning you'd have to T into the two rear lines post ABS module (stupid). The BMW unit is very unique in that it splits the inputs front and rear, making the ability to run balance bars/prop valves non issue and such very desirable in a retrofit.
2. The diagnostic information on the S2000 unit is only accessible over CAN. It doesn't mean it can't be run standalone, it's just that you'll be in the dark if there's a fault. The BMW system is over K-line.

Anyway, with that said, I tried. It also means I have a 2008 S2000 CR edition ABS module sitting collecting dust. It's for sale if anyone is interested.

Did you check the earlier years abs modulators? The ap1 and ap2v1 cars didn't have CAN iirc.

AP1 would work, but it's 3 channel. Not sure on the AP2v1, but if it's 4-channel it'll have the same diagonal style split. Something I wanted to avoid in the end.

iirc ap2v2 is an mk60E unit.

I'm personally go to install an mk60, standalone tuning, its hard to beat. Or an Boschmotorsport M4 or M5 abs unit.