Most of my research is directing me to threads of C5's with DTC errors that are trying to disconnect active handling and traction control which are only partially answering my question...So I'm looking for those that have some knowledge about the C5 EBCM.

I'm building a midengine car from a C5 donor using the front and rear suspension and the LS1 from a 2004. I'm not using the PCM or BCM as I'm using a standalone Haltech. However since I have the full donor car I've been considering taking the EBCM and ABS system and installing them as a "standalone" ABS on the car (already using C5 hubs/speed sensor/brakes etc). I've seen a couple examples of this being done (Matt Jones 69 camaro) but they never give details on the build. My understanding was they used all the sensors on the install (yaw, steering angle, lat accell etc). I thought they installed only the ABS and not active handling, but from what I'm reading in the dtc errors threads are those sensors mostly don't affect ABS. So perhaps the builds were using both ABS and AH. Anyway, I ONLY want ABS and don't want to screw with any unnecessary sensors. I read that IF you don't have the EBCM connected to the PCM and BCM that it WILL ONLY perform ABS. But then what additional sensors are required? How can I tell definitively if a sensor is needed or not?

Second part of the question is I read you can insert a switch in to the system to easily turn ABS on/off (brake lamp switch? can't find the comment regarding the details now) Anyway...without the ABS dynamically affecting bias front/back how could I get proper braking with the ABS off. Add a bias valve before ABS unit? or will this affect the ABS when it is switched on. I'm not sure if the abs unit determines the pressure its actually receiving and then proportions it based on needs or if it "expects" a certain pressure and then changes proportions based on needs. Then if the later...I may already be screwing things up with 12" wide tires in the rear, a different master cylinder etc.

 

Here is sample of thread I was referring to

EDIT...after more research I found this post. Pretty much answers a lot.

GTM ABS C5

But the question still remains on how the ABS functions via the EBCM. By putting an adjustable brake bias between the master cylinder and ABS so that I have perfectly biased brakes when the ABS is shut off will that cause problems to the ABS performance while it is on?

I can see it both ways. I have to imagine that since the C5 allows for disabling the ABS that they would have the car setup up appropriately when it is off. In other words a stock C5 should be properly biased with ABS off and then appropriately dynamically biased with it on as well. Therefore by making changes to the vehicle weight, wheelbase, wheel size, MC etc, this changes the required brake bias. So returning the modified car to appropriately biased with the ABS off via proportioning valve, may make the modified car perform better with the ABS on. Instead of assuming the EBCM is setup up for the stock C5 and yes modifying the car changes braking characteristics but modifying bias will only make it worse.

 

I think the ABS will work without having the PCM and BCM. You must have the wheel speed sensors for ABS. The yaw rate sensor does feed into steering Magnasteer (via the EBCM) if you plan on having that.

You will not have TC and obviously no AH.

The EBCM does control braking bias (front versus back). With the changes you are doing it may not perform that correctly. Not sure how you would disable that since it is in the internal programming. The brake pressure sensor at the BPMV is only to detect a differential braking pressure problem issue to throw a warning light.

I would think you could add a mechanical bias proportioning valve the adjust the braking to what you want with the EBCM still doing it's thing in the background.

Anytime you would want to temporarily remove ABS, you could just put in a way to kill power to the EBCM. It has two power inputs. Dual contact switch or remote relay, your choice.

Hope this helps some. Not sure if I addressed everything so if you have any follow up I'll see if I can address them.


Mr. Sam

 

Good Info Thanks!! I wasn't aware of the Magnasteer. Well since I'm using the C5 rack, it seems like I should try to include this. There doesn't seem to be any downside. If Magnasteer is disabled due to elimination of the yaw sensor, I would assume this means the magnets do not function and steering would be permanently more difficult at slower speeds (I could live with this). Without a BCM or use of tech2 I'm curious how installing the sensors (yaw in particular here) might be done. Multimeter reading and shimming? Or does the EBCM somehow reset the yaw sensor? Or close enough is good for purposes of the magnasteer and won't introduce irregular handling if it's off from stock positioning slightly. Are you also confident that steering angle is not used in Magnasteer as this seems to be involved with the slip angle? This sensor poses much more difficulty to install as I'm not using C5 steering column.

I will incorporate TC from the Haltech elite eventually and based on a lot of comments I don't really want the AH. Heard stories of one side braking at speed.

Based on reading I knew no changes to EBCM could really be made and that performance would not necessarily be 100% as designed. I guess my issue is that since I haven't found much info on HOW it senses then corrects the braking, I don't really know the extent to which this will be affected and then the best way to proceed.

So what comes first in your opinion the chicken or the egg? Settup bias first without abs or with? Setting up the bias with the abs on could be difficult as it's going to try to prevent lockup (or maybe this makes it easier...). I'm new to biasing so without ABS I guess you'd setup so the front lock up just before the backs lockup and with you'd setup so ABS in front kick in first?

 

The Magnasteer does use steering angle from the SWPS, but I forgot it also uses vehicle speed. So without a PCM and SWPS it will not work.

With regard to bias I would just see how the braking is first, If not close or good enough I would disconnect the ABS and adjust the bias mechanically. Once done turn ABS back on and see how the braking is.

 

I would think the module uses the wheel sensors and an indication of vehicle speed. I'm pretty sure there is no speed input from the PCM and I doubt it would obtain that over the serial bus. But, if there is a speed input it's likely the typical 4k pulses per mile signal that would be easy to generate.

 

I guess I'll give installing the SWPS on the new steering column a shot hopefully it's also 1" - if not I won't bother. So sounds like for ABS and Magnasteer I just need the EBCM, 4 wheel speed sensors, Yaw, and SWPS and for ABS alone...just EBCM and 4 WSS. Anybody know what the SWPS and yaw sensor should read in their straight/level positions?

 

I'll have to look at the FSM and see how the EBCM gets the VSS input. I thought it came via the PCM. The Yaw sensor is only for AH like the Lateral Accelerometer.

The early SWPS had an analog voltage output you could use to center it but the later ones (01-04) do not if I am correct. I will look and see what it takes to read that output on the later ones. The early SWPS are not available except used if you can find one.

BTW, I love properly done mid engine cars. I have Detomaso Pantera which is a great car.

What are you putting together?


Mr. Sam

 

I'm building a Superlite Apex. Here's a couple pics.

 

Nice. Would like to see pictures once the drive train is installed before the shell is installed.


Here is mine.