IW STi Forum banner

81 - 100 of 149 Posts

·
Registered
Joined
·
1,320 Posts
Discussion Starter #82
Re: Project Silverstreak: Perrin Gauge install!

Holy shit! Thanks for the info. Besides getting the splined end out, do you have to worry about the CV joint itself?
I just left the broken end in the joint and bought a new half shaft assembly from Subaru. I did save the old one for spare parts.

So according to Driveshaft Shop the CV's are made out of the Japanese equivalent of 4130 chrome moly steel. The axle shaft itself is made out of something a bit weaker. I think Subaru did this on purpose. The outer stub shaft holds the wheel bearings together. Designing the axle to break first allows the car to still be driven. Just lock the center diff and go. I would not drive it on the highway, but I was able to drive it off the course and onto a friend's trailer. If the stub shaft broke the bearings would have been destroyed and the wheel assembly could have came off. It's this thought that kept me from buying the DSS axle shaft upgrade kit. I was concerned about moving the weakest link to the stub shaft.

A friend of mine with a more prepped car has broken a half dozen or so. Always the left rear, always the same place ...the outer spline on the axle shaft. He can change them out in about 5-10 minutes. Unless you launch the car hard enough to break the tires loose it's probably not something an STI owner would have to worry about. As for me I'm going to buy a spare shaft to keep on hand. I'm not sure I'll try and change it at the track though.
 

·
Registered
Joined
·
1,320 Posts
Discussion Starter #83 (Edited)
Re: Project Silverstreak: Perrin Gauge install!

So I tried to install a PST carbon driveshaft. In short it didn't fit.

You can see in the pic there is virtually no clearance between the body and the car and the shaft.



In the end I couldn't figure out why my car is different. All the bushings have been replaced, but save for a few they are mostly group N. There's no body distortion issues so everything should have been located precisely where it was supposed to be. The one bushing I thought might have changed clearances was the Whiteline outrigger bushings, but they where within a couple millimeters of the OE dimensions. Rally Sport customer service was great in trying to help me solve this problem, but after we exhausted all possible ideas I had to return the shaft. They did also offer to have a custom shaft made specifically for my car. With race season here I didn't have time to mess with all that, but may down the road. The only thing I can come up with is a friend of mine that owns a Subaru repair shop said the chassis can be out of spec 3/4" of an inch from the factory. It might be that variance that caused my clearance issues. Anyway that's the best guess so so far.

The reason I wanted a one piece shaft is to get rid of the carrier bearing assembly. The slop in the rubber cushion drives me crazy because I know that's where most of the bucking in low gears comes from. So then Plan B... well technically C. I tried this first with a compound called Versimold and it proved to be hard to work with and too soft for my application.

So my plan is to use something called a liquid engine mount kit form a company called DST. It's basically 400ml of liquid two-part poly urethane. It comes in four durometer ratings. 60A, 80A, 80A High-performance and 94A. I'm going with the 80A HP. It should come close to the durometer rating of group N bushings which should help to keep things consistent. I know NVH will go up a bit, but it shouldn't be too bad relative to what it is already. I'm going to remove the driveshaft and fill the cushion that surrounds the carrier bearing. The kit costs around $40 so if it does the job I'll be happy.

to be continued...
 

·
Super Moderator
Joined
·
10,688 Posts
Re: Project Silverstreak: Perrin Gauge install!

Subysal,

That portion of the car when I installed the ACPT driveshaft had to be clearanced/finessed/beat the shit out of with a BFH a few times. I'll try and link the image.
 

·
Registered
Joined
·
1,320 Posts
Discussion Starter #85
Re: Project Silverstreak: Perrin Gauge install!

Subysal,

That portion of the car when I installed the ACPT driveshaft had to be clearanced/finessed/beat the shit out of with a BFH a few times. I'll try and link the image.
Yes. I have heard this same thing from a couple friends of mine I race with. This was not something that was made known when I purchased the driveshaft nor was it something I was willing to do. The advantages of a carbon shaft would be awesome, but if I can get the results I want by adding urethane to the oe shaft bushing without altering the body structure I'll be happy with that.
 

·
Registered
Joined
·
668 Posts
Re: Project Silverstreak: Perrin Gauge install!

I went with a Driveshaft Shop carbon fiber shaft...no clearance issues. It may be smaller diameter, but after 60K+ miles works as advertised.
 

·
Registered
Joined
·
1,320 Posts
Discussion Starter #87
Re: Project Silverstreak: Perrin Gauge install!

I've heard the DSS shaft is a smaller diameter, but the guys I race with have not had good luck with them. Apparently the bond between the carbon and metal gives up after so many hard launches. That's actually the main reason I went with the PST, I originally wanted a DSS shaft. Theoretically I should be able to get PST to make a smaller diameter shaft for my application. I'm running half the torque the RSD spec shaft is rated for. I just don't have the time right now to go through all that. Also if the poly plan works I'd rather put the 1k towards something else... like a trailer.
 

·
Registered
Joined
·
1,320 Posts
Discussion Starter #88 (Edited)
Re: Project Silverstreak: Perrin Gauge install!

So plan C or as I like to call it Liquid Schwartz has arrived. Shooting for tomorrow to get this done.

 

·
Registered
Joined
·
1,320 Posts
Discussion Starter #89 (Edited)
Re: Project Silverstreak: Perrin Gauge install!

Just for reference here's what the Versimold looked like. It's just not good for this application. I could not get it to cure all the way through using heat. I had to push it in too.





It was imperative to get the shaft dead nuts level. Here's a shot before I poured in the poly. I also cleaned the cavity thoroughly and used an adhesive promoter.



The urethane flowed so well I was able to use a syringe to suck it out of the container and slowly fill the bushing (to avoid air bubbles). This method worked really well and I was able to fill it to the top without over flowing.



I had to set the shop thermostat to 77ºF and now have to wait 7 days for it to cure properly. This stuff is very exacting. I feel like I should go buy a lab coat just to use it.

 

·
Registered
Joined
·
1,320 Posts
Discussion Starter #92 (Edited)
Re: Project Silverstreak: playing with poly...



So I cured the urethane as per the instructions (7 days @ 77ºF) and reinstalled the shaft. Frankly I was surprised at the difference it made after driving the car. The car feels so much more solid and consistent. Especially at lower speeds. I guess it makes sense when you've replaced every bushing in the entire car in an attempt to tighten everything up... that 1/4" or so of play in that carrier bearing bushing can really be felt. There is a bit more gear noise, but that's all as far as the detractions go. I don't foresee any long term adverse effects, but only time will tell. For now I can't wait to try it out at the next time attack on the 7th!

I'm kinda surprised no one has thought of doing this before.
 

·
Registered
Joined
·
101 Posts
Re: Project Silverstreak: driveshaft is back in!

Bushings, seat, and steering wheel have always been my favorite mods just because they change how you "feel" the car so much. Going from the stock driveshaft to a carbon fiber one was huge too, I'm sure you're going to love the difference!
 

·
Super Moderator
Joined
·
10,688 Posts
Re: Project Silverstreak: playing with poly...

[URL=http://i262.photobucket.com/albums/ii95/SubySal/STI%20journal/driveshaft%20w%20poly.jpg]Image Link
[/URL]

So I cured the urethane as per the instructions (7 days @ 77ºF) and reinstalled the shaft. Frankly I was surprised at the difference it made after driving the car. The car feels so much more solid and consistent. Especially at lower speeds. I guess it makes sense when you've replaced every bushing in the entire car in an attempt to tighten everything up... that 1/4" or so of play in that carrier bearing bushing can really be felt. There is a bit more gear noise, but that's all as far as the detractions go. I don't foresee any long term adverse effects, but only time will tell. For now I can't wait to try it out at the next time attack on the 7th!

I'm kinda surprised no one has thought of doing this before.
Good job, interested in hearing long term results.
 

·
Registered
Joined
·
1,320 Posts
Discussion Starter #96
Re: Project Silverstreak: driveshaft is back in!

So a bit of an update... Yes the poly makes a difference! I noticed it on the start. Usually I have to launch hard and break the tires loose to get a fast start. If I don't the car bucks and I have to let off the gas a bit to get it to settle. That's when boost drops off. However, without the driveshaft bouncing around I don't get any bucking and the car just goes. It's nice not to have to hammer it on the start. The car is also smoother overall on course. I think that was the last bit of play in the car. I wish I had done this much sooner! I also checked the bushing after the event. The poly is holding up perfectly.

This is my first run. I managed to shaved off another 7/10th's in my 4th run. That was good enough for second overall out of 157 drivers. There is no PAX. This is all raw time. I was able to squeak past a GTR and a McLaren. The only car that got me beat was a very modified turbo-charged MR2. The course really suited the STI's gearing. I was able to stay in 2nd while many others had to downshift to first. To date this is the best driving I've done!

 

·
Registered
Joined
·
694 Posts
Re: Project Silverstreak: driveshaft is back in!

So Time Attack at PPIR is kinda like a big autocross?

Looks fun... do you know where there's a schedule of their events from the year? Might have to make the trip.
 

·
Registered
Joined
·
1,320 Posts
Discussion Starter #99 (Edited)
Re: Project Silverstreak: driveshaft is back in!



The Time Attacks are kinda like a big autocross, but also very different. You don't work the events. There is no membership required. You just show up, pay the entry fee and proceed to grid. Though this last event had a short course the courses are usually longer and faster. You get 5 runs per event... and fun runs most of the time (depending on weather and such). They run the whole grid at once so there is more time between runs. Some SCCA guys don't like this, but I do. 71R's run better cold and it's nice not having to rush between runs. The track surface has at least twice the grip of the back lot and is very smooth. PPIR is constantly working to improve the events and even the course itself. They've recently added a bunch of turn sections to the infield to expand course designs. In fact they are working on new improvements on the infield right now.

Most of the news and activity about events is focused on the facebook page here:
PPIR Time Attack Public Group | Facebook

The rules, roster, overview, etc. are here:
Pikes Peak Int'l Raceway
 
81 - 100 of 149 Posts
Top