Why should you consider using a Rear Wheel (ground) Speed Sensor on your FWD Honda
We have been selling our rear wheel speed sensor kits and brackets for a while now, roughly 1000 units now over the last 8 years or so yet I still see misinformation about "ground" speed and the benefits of putting one on your front wheel drive application.
CLIFF NOTE BENEFITS
- Works best with a factory ECU
- Better launch control
- More accurate vehicle (ground) speed reading and control
- Cheaper than replacing a factory transmission VSS
- Bolt-on, and easy to setup.
- Can benefit you in all types of racing (drag, road course, etc)
The majority of applications we see using these are 92-00 Honda Civic or Acura Integra, 02-06 RSX and even some 8th/9th Gen Civics as well. We have made bolt on sensor mounting brackets for the 92-00 applications that use both disc or drum brakes. These brackets are very simple pieces, you could certainly make your own out of very basic materials but if you look at a $$$ per time spent, we feel there is a lot of benefit to grabbing a bracket when you purchase your RWSS kit at Xenocron. With that said, there are lots of ways to mount the brackets. Our brackets mount the sensor to trigger off of the rear wheel lug nuts. The lugs are EVENLY space ferrous pickup points for the Hall Effect sensor we supply. As long as the lugs arent welded to the hub which makes them a potential non-EVENLY spaced trigger, and as long as there are no artifacts of other metal or holes in the hub, these work great.
For a typical Honda with a 22-24" tire, this equates to (4) pickup points to travel about 6 feet. Coincidentally, the pickup points in the factory B, D, H and K Series transmissions equate to approximately the same amount. This means, with an aftermarket ECU like Hondata, Neptune or KTuner, you can use the rear (ground) speed as you main vehicle speed sensor. A lot of people say "that's not much resolution" but in fact the only place it really lacks in resolution is below 15 mph and that more based on how a factory ECU averages or smooths the signal coming into it. Certainly more pickup points are helpful, and you can use our same sensor to trigger off a factory ABS tone ring, but the stock ECU will not like 52 pulse per revolution instead of 4 and we suggest only using more resolution if you are using a standalone ECU like a Haltech or MoTeC.
So why use ground speed? Well, with a FWD car, you are going to spin....and when you do spin, and that wheel is the only one reporting speed to your ECU, it is not getting correct information. With Boost by Gear in a OBD1 or K-Series ECU, you are given tables that give you a boost target or % based on a gear and an RPM. Gear is calculated based on wheel speed, gear ratios and engine rpm. If you target a certain amount of boost, and the car spins....your RPM goes up, and typical you request MORE boost at a higher rpm, so if you spin, now the ECU is going to request MORE boost and spin MORE. With a rear wheel sensor, the speed the ECU sees stays the same even at the front wheels are spinning, and so it will not request more boost, until the car hooks and goes.
Launch control is another added benefit as you can keep the car on the the launch RPM for a few moments by basing the release or turning off launch based on ground speed. If you turn off launch control based on driven or front wheel speed, it will turn off as soon as it spins. If you base it on ground speed, and do not allow it to turn off until further down the track (when you hit, 10, 15, 20 or maybe 25 mph) it keeps the launch limiter on for a bit longer so the wheel spin cannot get out of control.
Again, most of these benefits will be found when using a factory ECU like Hondata S300, Neptune RTP or Hondata KPRO. If you are running a standalone ECU, there are many more features and more than likely if you are using one of these ECUs hopefully you are using both ground and driven speed in your features.
If you have a story of how adding a RWSS has helped you, please share it with us!