Unfortunately, it also has some potential problems. This is the area where I had the most difficulty finding good info. Most of the threads I read were by people that were singing the praises of their installation and glossed over any issues they were having.

Some EPS units are reported to have a "dead feel" and don't give much road feedback to the driver. I've seen reviews of new cars that this disconnected feeling is reported to be present. This may be due to too much assist, but I never found any reliable info about this. I have driven older hydraulic steering cars that had this problem. I seem to remember it most on the older linkage type power steering setups rather than the more modern integral units. The older setups felt completely disconnected from the road, but you could literally steer a 2 ton sedan with your little finger. I remember one fellow describing it as feeling like you were driving on butter with bald tires!

The most serious issue I found reported is returnability. A good steering system will attempt to return to straight ahead (RTC - return to center) after a turn if you let go of the steering wheel. Some EPS systems are said to dampen the RTC. This would be a real deal killer for me as I think it's unsafe. I don't want a car that I have to "unsteer" after a turn, especially any performance car that might be driven, well, like a performance car.

The RTC issue is what I discussed with the steering rep. He told me that his company had looked into EPS, but had put it on hold because they experienced RTC issues with some, but not all, of their test cars.

I have found some info that suggests that this is a result of the steering control unit being out of adjustment since it reportedly keeps up with where center is located and is supposed to apply a small reverse assist to get back to center when a turn is completed. As far as I can tell, there doesn't appear to be a command from the vehicle computer that tells the steering to RTC, so the control unit out of adjustment thing may be true, but I doubt it. If that were the case, it seems to me that the units would have to be removed and reinstalled in exactly the same spot in the steering travel every time. That seems a little far fetched, but I guess it's possible.

My theory is that the RTC issue is purely mechanical. The cars I've researched that had do-it- yourself EPS added were originally non-power steering cars, mostly older muscle cars. Those old cars usually didn't have much caster to reduce steering effort and most older cars that came with manual steering had pretty high steering ratios for the same reason. Caster is one of the major players in getting normal steering to RTC.

Some of the comments I read said that with the power off there was no difference in effort required to steer the car, but I do know from handling them, that there is some internal mechanical drag from the EPS gearbox. The EPS units like mine are really just right angle worm drive gear boxes with a permanent magnet DC motor. Worm drives are known for their self holding ability even with low numbered gear ratios. Add in the drag from the permanent magnets in the motor and it makes sense that there would be some mechanical dampening. For what it's worth, the drag is high when you initially try to turn the unpowered EPS, but drops off after you get it turning.

Since a manual steering gear box has a high mechanical advantage and since the EPS unit is on the steering wheel side, any drag by the EPS would be multiplied by the steering box. Just to throw out some numbers, if the steering box had a 20 to 1 ratio, the drag of the EPS unit would, in theory at least, be 20 times greater at the spindle. Once I got the steering on my car hooked up with a manual MII rack and the EPS, I noticed that it takes quite a lot of effort move the steering by trying to move the spindle. Much more effort than I normally associate with moving manual steering the same way. This leads me even more to believe that the issue is mostly mechanical.

I did read one source that said that one of the big three (Ford I think) had to go to specially ground rack and pinion units to get one of their car models to RTC reliably. This also would seem to indicate that the problem is mechanical since if it could have been overcome by simply adjusting the steering control unit, I'm sure Ford would not have spent extra time and money on high precision rack parts. Of course, this info came courtesy of the good old internet, so you never really know if it's based in actual fact.

The solution could be as simple as increasing the caster in the front end to give a much stronger mechanical RTC signal. This and possibly using a faster(lower ratio) steering gear to reduce mechanical advantage the EPS drag has. Adding extra caster should be fairly simple on most cars, but changing a steering box could get expensive. Many applications may not even have a faster box available. We'll just have to see what we have when I get my car on the road and go from there.

At any rate, the Saturn EPS I'm adding is fairly inexpensive compared to the systems offered by the big name aftermarket companies. The system can be gutted if I don't like it and then it really won't add any drag to the steering. I can then switch to a hydraulic rack with no other changes. Everything is in place to go to hydraulic steering as plan "B". The gutted EPS system won't be seen behind the dash if I go this route.

That's enough for right now.
Stay tuned, more to come.