Is this LSD ?, ... or perhaps some other phenomenae ? |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Is this LSD ?, ... or perhaps some other phenomenae ? |
drifter914 |
Nov 8 2019, 10:03 AM
Post
#1
|
drifter914 Group: Members Posts: 50 Joined: 12-May 13 From: pearce, arizona 85625 Member No.: 15,863 Region Association: Southwest Region |
So I have this '76 914-8 with an LS-1 conversion & one day while pulling out of a graveled area I kicked it a bit & noticed leaving 2 ruts behind instead of the one I was used to in a previous 914.
So the other day when I had it up on jack stands I started it up, put it in 1st gear & let it idle while I got out to look... left rear wheel was turning fwd at a constant rate, while the right was also turning fwd, but at a slower rate. Could it be that I have some sort of limited slip arrangement here ? Transaxle is a modified 901 & has the numbers HA 22095 on the bottom of the case. Thanks for any info on this... Terry |
mepstein |
Nov 8 2019, 10:13 AM
Post
#2
|
914-6 GT in waiting Group: Members Posts: 19,142 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region |
|
GregAmy |
Nov 8 2019, 11:05 AM
Post
#3
|
Advanced Member Group: Members Posts: 2,262 Joined: 22-February 13 From: Middletown CT Member No.: 15,565 Region Association: North East States |
The car that made these two equal-length tire marks had positraction. Can't make those marks without positraction.
And why not? What is positraction? It's a limited sIip differential, which distributes power equally to both the right and left tyres. The 914 has a regular differential, which anyone who's been stuck in the mud knows you step on the gas, one tire spins, the other does nothin'. |
Retroracer |
Nov 8 2019, 01:54 PM
Post
#4
|
Senior Member Group: Members Posts: 606 Joined: 7-July 13 From: Bend OR Member No.: 16,100 Region Association: Pacific Northwest |
|
burton73 |
Nov 8 2019, 02:50 PM
Post
#5
|
burton73 Group: Members Posts: 3,457 Joined: 2-January 07 From: Los Angeles Member No.: 7,414 Region Association: Southern California |
My Cousin Vinny (5/5) Movie CLIP - Automotive Expert (1992) HD
Positraction? Bob B https://www.youtube.com/watch?v=CFdJza0AbeA |
mepstein |
Nov 8 2019, 03:33 PM
Post
#6
|
914-6 GT in waiting Group: Members Posts: 19,142 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region |
Sorry, meant to say if both turn the same direction forward or backward, it’s got lsd. If they turn opposite, no lsd.
|
drifter914 |
Nov 9 2019, 10:30 AM
Post
#7
|
drifter914 Group: Members Posts: 50 Joined: 12-May 13 From: pearce, arizona 85625 Member No.: 15,863 Region Association: Southwest Region |
Sorry, meant to say if both turn the same direction forward or backward, it’s got lsd. If they turn opposite, no lsd. O.K. ... this morning I jacked up the back end & spun the driver side rear wheel by hand... first in neutral ... then in 2nd gear same result... they turned in opposite directions... no LSD . So the two ruts in the gravel must mean that with very little resistance, the wheels spin alternatively. I notice the right side rut is more pronounced. I imagine on asphalt I would leave only a right tire burnout, but I just am not a burnout guy... so no LSD for me ! Terry |
settador |
Nov 9 2019, 11:19 AM
Post
#8
|
Newbie Group: Members Posts: 31 Joined: 16-May 05 From: Lee, NH Member No.: 4,086 Region Association: None |
Last time I had LSD
I saw colors and the road was like sea |
sixnotfour |
Nov 9 2019, 11:47 AM
Post
#9
|
914 Wizard Group: Members Posts: 10,392 Joined: 12-September 04 From: Life Elevated..planet UT. Member No.: 2,744 Region Association: Rocky Mountains |
Augustus Owsley Stanley III is rumored to have made the best
|
Superhawk996 |
Nov 9 2019, 11:56 AM
Post
#10
|
914 Guru Group: Members Posts: 5,670 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
Sorry, meant to say if both turn the same direction forward or backward, it’s got lsd. If they turn opposite, no lsd. O.K. ... this morning I jacked up the back end & spun the driver side rear wheel by hand... first in neutral ... then in 2nd gear same result... they turned in opposite directions... no LSD . So the two ruts in the gravel must mean that with very little resistance, the wheels spin alternatively. I notice the right side rut is more pronounced. I imagine on asphalt I would leave only a right tire burnout, but I just am not a burnout guy... so no LSD for me ! Terry The reason you see two tracks is because the road friction is reasonably uniform at each contact patch at each tire. In the case of gravel it is a medium friction surface. Friction is referred to as Mu in reference to its Greek symbol that represents the coefficient of friction in physics equations. A conventional open differential is able to drive both wheels with approximately the same force to each wheel on medium and high Mu surfaces. For typical passenger car applications It isn't until you get onto very low mu surfaces (mud, snow, ice, etc.) that the "one wheel peel" effect of spinning up one wheel becomes a problem. Similarly, if you are cornering hard and unloading the inside tire, that wheel can spin due to the light load on it that limits the amount of torque it can transfer to to road. An open differential can only transfer torque equally between the wheels. If one wheel is lightly loaded or on low mu (like ice), that low torque transferred is effectively zero. One wheel spins and transfers very little torque and the other wheel therefor gets zero torque, and the car doesn't move. At that point you're giving up forward momentum. LSD's are used in performance applications to help overcome this limitation of an open differential but if you lift a wheel off the road even with a LSD, you'll quickly discover that even a high bias LSD can't transfer very much torque. Better than an open differential but still not very much. Modern electronic Limited Slip Differentials would be the sole exception but those really are a completely different animal vs. a clutch plate LSD or a Torsen. In your case, with both wheels just going straight with no cornering, the load on each is about equal. The road surface is about equal mu from side to side. The open differential transfers approximately equal torque, therefore you get approximately equal spin out marks. |
rgalla9146 |
Nov 9 2019, 12:32 PM
Post
#11
|
Advanced Member Group: Members Posts: 4,538 Joined: 23-November 05 From: Paramus NJ Member No.: 5,176 Region Association: None |
So I have this '76 914-8 with an LS-1 conversion & one day while pulling out of a graveled area I kicked it a bit & noticed leaving 2 ruts behind instead of the one I was used to in a previous 914. So the other day when I had it up on jack stands I started it up, put it in 1st gear & let it idle while I got out to look... left rear wheel was turning fwd at a constant rate, while the right was also turning fwd, but at a slower rate. Could it be that I have some sort of limited slip arrangement here ? Transaxle is a modified 901 & has the numbers HA 22095 on the bottom of the case. Thanks for any info on this... Terry a 914 trans with OEM LSD would have HB as a prefix....but many types are available for later install. your two wheel burnout is due to reduced traction and a straight start. |
GregAmy |
Nov 9 2019, 04:21 PM
Post
#12
|
Advanced Member Group: Members Posts: 2,262 Joined: 22-February 13 From: Middletown CT Member No.: 15,565 Region Association: North East States |
Last time I had LSD I saw colors and the road was like sea (IMG:style_emoticons/default/drunk.gif) If it's a torque-biasing diff, like a Quaife, it would roate different directions. The "jack up the rear and check for wheel rotation direction" only works for sprung-clutch-type or Detroit Lockers. Two scratch marks? With a V-8? That's an LSD. You really should watch your culturally-significant movies. Marisa got it right. |
djway |
Nov 10 2019, 01:28 AM
Post
#13
|
Senior Member Group: Members Posts: 787 Joined: 16-October 15 From: Riverside Member No.: 19,266 Region Association: Southern California |
Back in the day my lil Baja Bug shot up two monster rooster tails and it was nuttin but a 67 swingaxle
|
settador |
Nov 10 2019, 11:00 AM
Post
#14
|
Newbie Group: Members Posts: 31 Joined: 16-May 05 From: Lee, NH Member No.: 4,086 Region Association: None |
|
914bub |
Nov 10 2019, 11:33 AM
Post
#15
|
Member Group: Members Posts: 433 Joined: 16-August 13 From: Modesto CA. Member No.: 16,260 Region Association: None |
And if you do have a limited slip and you break em loose making a right turn at say an intersection brace yourself because as soon as you get traction again your going straight, and quickly into whatever you're pointed towards. I learned that one the hard way when I was 18 in a quick 68 Volvo 1800. In my case I was pointed towards a Santa Clara county bus stop bench. Wiped out the bench and the front end of my 1800. I also learned that Jack Daniels and limited slip + 18 years old = FAIL. Glad I lived through my stupid youth without hurting somebody.
|
drifter914 |
Aug 10 2020, 11:59 AM
Post
#16
|
drifter914 Group: Members Posts: 50 Joined: 12-May 13 From: pearce, arizona 85625 Member No.: 15,863 Region Association: Southwest Region |
Thanks you guys for the interesting replys & Superhawk for the education !
Driving on LSD was also quite an education... but for fun, nothing like that one hit shit & fwy driving with a pair of binoculars !!! |
rhodyguy |
Aug 10 2020, 12:08 PM
Post
#17
|
Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,042 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
Then everything starts melting and Stairway to Heaven seems like it's been playing for an hour. Then your girl friend turns into a lizard. Then you pull over and turn the car off. Having sex with a lizard was not part of the game plan.
|
KELTY360 |
Aug 10 2020, 01:20 PM
Post
#18
|
914 Neferati Group: Members Posts: 5,024 Joined: 31-December 05 From: Pt. Townsend, WA Member No.: 5,344 Region Association: Pacific Northwest |
Then everything starts melting and Stairway to Heaven seems like it's been playing for an hour. Then your girl friend turns into a lizard. Then you pull over and turn the car off. Having sex with a lizard was not part of the game plan. .....ask him how he knows. (IMG:style_emoticons/default/shades.gif) |
Lo-Fi Version | Time is now: 28th March 2024 - 04:03 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |