Manual steering thoughts
04-18-2010, 06:14 PM
#32
My preferred seating position is right up on the steering wheel, that may have something to do with it by providing better leverage and reducing arm and shoulder fatigue.
04-18-2010, 06:59 PM
#33
Rennlist Member
Perhaps there is a point where the benefits of a manual rack are surpassed by the negatives. My assumption would be that this is directly corresponding with tyre sizes and types. I noticed a similar feeling to what Van describes during trail braking. I was only driving on the street yet going into slower sharpish corners, the car felt like it was being sucked down and forward rather than allowing any turn in. I did have to turn like a 'modern' racer...all up close and elbows sticking out. This is with 275/18 NT01 up front.
Again, it sounds like the guys who like the manual rack are driving smaller tyred and lighter model cars. This would make a huge difference. Especially if you were doing any endurance racing.
IMHO
Again, it sounds like the guys who like the manual rack are driving smaller tyred and lighter model cars. This would make a huge difference. Especially if you were doing any endurance racing.
IMHO
04-18-2010, 10:28 PM
#34
Rennlist Member
i drove a very similar car to mine-weight and power wise- back to back w/ my car. His was manual, mine is power. Both run 245 front tires all the time. His car was great cruising around but a bear at slow speeds. Not sure about on the track but having just come from a DE this weekend and doing 24 hours two weekends ago in the Dragon w/ power steering i love POWER STEERING. I get plenty of feedback from my power rack-which if you keep up on it doesnt leak all the time...
Didnt seem to have any troubles with steering inputs at all, and corrections when necessary are quicker for sure.
Didnt seem to have any troubles with steering inputs at all, and corrections when necessary are quicker for sure.
04-19-2010, 02:20 AM
#35
Rennlist Member
I don't find my manual rack to feel heavy at all. The ratio is slower but its not too bad. I run 275's up front and use it for endurance races. I have had no problems in 3+ hours stints and none of my co-drivers have ever complained about heavy steering even after racing it for several hours straight.
I have my steering wheel spaced back a few inches. You do need to have proper leverage and your caster settings will also have an effect on steering effort. If you have power steering you would never notice that. I get ~3.9 deg max caster on my car. If your car can take a lot of caster, then yes I think power assist would be advantageous.
The thing is so simple and light with nothing to break. I don't plan to go back.
I'm not sure how you could back-to-back test a power vs. manual rack. Its an involved swap (intermediate shaft, tie-rods, alignment, etc.). More work than I would want to do at the track. I was forced to do it once at the track and its not a fond memory!
I have my steering wheel spaced back a few inches. You do need to have proper leverage and your caster settings will also have an effect on steering effort. If you have power steering you would never notice that. I get ~3.9 deg max caster on my car. If your car can take a lot of caster, then yes I think power assist would be advantageous.
The thing is so simple and light with nothing to break. I don't plan to go back.
I'm not sure how you could back-to-back test a power vs. manual rack. Its an involved swap (intermediate shaft, tie-rods, alignment, etc.). More work than I would want to do at the track. I was forced to do it once at the track and its not a fond memory!
04-19-2010, 03:04 AM
#36
Drifting
Join Date: Jun 2007
Posts: 3,464
Likes: 0
Received 0 Likes
on
0 Posts
I run 245 Hoosier R6 up front and having recently done this change my initial impression was that that the steering was heavy and initially vague (felt like lots of travel before any motion or turn) This went away as ai got used to it however I can say that it is certainly heavier and I am moving the wheel an inch closer to me for the next race to help. After a couple of sessions I did find the seering more (much) more informing. As many have said you can feel weight transfer and loads. For instance in the uphil at LRP you can actually feel the compression whereas with power I could not fel it no where near as much.
As for times hard to say as I was on old tires and also just took 230lbs out of my car.
As for times hard to say as I was on old tires and also just took 230lbs out of my car.
04-19-2010, 04:03 AM
#38
Race Director
Scrub angle on the wheels make a big difference with a manual rack when it comes to effort. I've driven several 944's with and without power steering.
Would prefer power steering unless I was going for ultra lightness in a racing class with max tire width regulations of 225 or so.
The turbo Cup car was good with manual rack but once fitted with grippy wide tires it was a bit tricky and you had to be fast to catch it at times. I learned that the stock steering wheel is nice to have because of the diameter, needs a spacer though to come closer to the driver.
If I was to build a race car I would look at an electrical race power steering system like the ones used in modern race cars running big rubbers.
Would prefer power steering unless I was going for ultra lightness in a racing class with max tire width regulations of 225 or so.
The turbo Cup car was good with manual rack but once fitted with grippy wide tires it was a bit tricky and you had to be fast to catch it at times. I learned that the stock steering wheel is nice to have because of the diameter, needs a spacer though to come closer to the driver.
If I was to build a race car I would look at an electrical race power steering system like the ones used in modern race cars running big rubbers.
04-19-2010, 09:04 AM
#39
Three Wheelin'
Don't forget that you should see an increase in horsepower because you are eliminating parasitic drag. I will be doing this conversion on my 951 race car in the next two weeks and will report. I am changing it to lower the weight on in the front. I have heard that it provides more feel.
I would suggest that weight plays an important part, I expect to be in the 2700 range with driver, running 245/35/18's.
Regarding an electric pump powered rack. I attended a car prep seminar at Fall Line and they have converted a number of cars to BMW electric pumps which was pretty cool. Something else that was very trick was their use of BMW motorsport ABS on porsche race cars, apparantly it's way ahead of the Porsche units.
I would suggest that weight plays an important part, I expect to be in the 2700 range with driver, running 245/35/18's.
Regarding an electric pump powered rack. I attended a car prep seminar at Fall Line and they have converted a number of cars to BMW electric pumps which was pretty cool. Something else that was very trick was their use of BMW motorsport ABS on porsche race cars, apparantly it's way ahead of the Porsche units.
04-19-2010, 12:17 PM
#40
Addict
Rennlist Member
Rennlist
Site Sponsor
Rennlist Member
Rennlist
Site Sponsor
I run a full manual setup on my 86 951, here is my take: (car is light, about 2750 with a full cage and tank of gas)
On the track:
I run 245/275 16" hoosiers, and you have to shuffle steer on the track, there is just no way you are taking a lot of turns without doing it due to the force required to turn the wheel under hard cornering. At the end of a 20-30 minute session, your arms are pretty tired.
On the street:
I love it (running 235/275 17"), and from a maintenance standpoint it is great. Simple, easy, slow speed steering isn't that bad, but you do have to put in extra effort in parking lots. No biggie IMHO.
If I had to do again (at a point where the entire PS system needs to be gone through), i'd just get the autozone power steering rack, rebuild the pump, and refresh all the lines and keep the PS setup. If you just refresh everything, it will give you problem free years of service.
On the track:
I run 245/275 16" hoosiers, and you have to shuffle steer on the track, there is just no way you are taking a lot of turns without doing it due to the force required to turn the wheel under hard cornering. At the end of a 20-30 minute session, your arms are pretty tired.
On the street:
I love it (running 235/275 17"), and from a maintenance standpoint it is great. Simple, easy, slow speed steering isn't that bad, but you do have to put in extra effort in parking lots. No biggie IMHO.
If I had to do again (at a point where the entire PS system needs to be gone through), i'd just get the autozone power steering rack, rebuild the pump, and refresh all the lines and keep the PS setup. If you just refresh everything, it will give you problem free years of service.
04-19-2010, 12:31 PM
#41
Three Wheelin'
I eliminated a leaky power steering system and a non-functioning AC system when I first got my 951. How much HP does that really recover? Aren't we talking about a 1/4 HP or so?
04-19-2010, 05:07 PM
#43
Rennlist Member
04-19-2010, 05:45 PM
#44
Race Director
Perhaps there is a point where the benefits of a manual rack are surpassed by the negatives. My assumption would be that this is directly corresponding with tyre sizes and types. I noticed a similar feeling to what Van describes during trail braking. I was only driving on the street yet going into slower sharpish corners, the car felt like it was being sucked down and forward rather than allowing any turn in. I did have to turn like a 'modern' racer...all up close and elbows sticking out. This is with 275/18 NT01 up front.
Again, it sounds like the guys who like the manual rack are driving smaller tyred and lighter model cars. This would make a huge difference. Especially if you were doing any endurance racing.
IMHO
Again, it sounds like the guys who like the manual rack are driving smaller tyred and lighter model cars. This would make a huge difference. Especially if you were doing any endurance racing.
IMHO
I run manual steering with a manual rack on my 944 spec car. It is lighter, has less to fail and makes the engine comparment easier to work in. I would not go back to power.
However my 944 is only 2625lbs with me in the car. I run 225/50 R15 all around with RA-1s. I have only 133 hp. What I like most is delicate feel through the wheels. I can feel the contours of the road more closely and have better feeling of when the tires are gripping when they are not. As for corrections I correct slides all the time. Never any problem. I find the force required to turn the wheel to be very nice. Overall I feel more connected as power tends to dull the sharpness of the inputs so I can't as easily tell what the front tires are doing.
Now this works on light, small tire low grip car. I am not convinced it will work on heavier car with much bigger tires. At some point the nice delicate feel goes away and you are just stuck. I know for autocross a manual racke is not ideal even on ligtht car like mine. Heck even on street tires in a NA it just is not that good overall. In sweeping autocross turns i works great, However the extra force and slower ratio allow you to really get behind on steering.
So this very well might also happen on faster, heavier cars with more front tire.
As for speed in 944 spec some guys love powersteering and others don't. It all comes down to what you like as a driver.
BTW... I sit rather far back in the car. Some might say too far away from the wheel. I fine that my leverage is better sitting father back. If the wheel is too close it seems like my elbows get in the way forcing shuffle steer. Farther back just turn the wheel and if my hands get cross up it is no big deal.
