Thoughts on de-powering the rack? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Suspension, Brakes, Drivetrain discuss the wondrous effects of boost and your miata...

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 07-17-2011, 03:56 PM   #21
Junior Member
 
Join Date: Jun 2008
Location: Fairfield, California
Posts: 418
Total Cats: 0
Default

Quote:
Originally Posted by Spookyfish View Post
I think 99% of Spec Miata drivers in US, UK and NL only drain the fluid and plug. Not sure if welding is allowed. That should give some track (np) record for the poor mans depower?
I don't know anything about Spec racing, but what you say does make sense from a rules point of view, though I would think Spec racers would probably prefer a true manual rack for durability and rules sake; or if they did de-power, perhaps many are running welded pinions despite the rules. Perhaps they swap racks when theirs becomes sloppy or just stops working; I just don't know. But not welding the pinion is a major compromise in precision in exchange for not that much effort. It only takes an hour or two to remove and replace a pinion shaft.
Thucydides is offline   Reply With Quote
Old 07-21-2011, 03:02 AM   #22
I'm Miserable!
 
Join Date: Feb 2010
Posts: 584
Total Cats: 0
Default

On welding…

The pinion shaft's skinny core twists with steering input. However the amount is limited by the spline slop midshaft. If the skinny rod twists all the way, the spline slop is used up and from that point onward during that steering input in the same direction the shaft acts like it is one piece until the torsion comes back down. This acts as a safety factor, so that the skinny core rod does not eventually fatigue out and break. When you weld, the spline slop becomes inactive since the load passes through the outer welded area too. If your weld ever broke (unlikely), the remaining center rod will keep you from dying young. You can see the end of the skinny torsion rod at the rack's splined input which is where the steering column connects. It sticks out a bit past the spline. Some on the net freak about welding. This is actually a forgiving weld effort. You don't need to use special rod/wire. No you won't die like Senna. In that case they had butt welded the actual main shaft - ugh.

Some of the internet how-to sites I have read leave many seals in place besides the center of the rack piston seal. The rack comes pressure sealed in two main areas. The part of the pinion shaft where the spool valve lives. And either side of the center piston on the rack. The rack and pinion gear mesh zone is greased on both manual and power racks. On racks I have seen there are three pressure seals in the rack tube and at least two in the pinion shaft housing. Each seal adds some drag and uneven breakaway stiction,
so if you won't need them to hold in high pressure (1000+ psi) hydraulic fluid then remove them.

If you are doing a rack depower, track down ALL of the internal pressure seals so that you can cut friction / steering drag. This slightly lowers effort and mostly helps improve feel.
sjmarcy is offline   Reply With Quote
Old 07-21-2011, 03:33 AM   #23
Elite Member
iTrader: (2)
 
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,782
Total Cats: 119
Default

What the ever living **** are you saying? I accept responsibility for failure to comprehend, but this makes me question god's purported benevolence.

It sounds like this is the most complicated thing ever.

I just want my **** to feel good and not wear out and be horrible.
Faeflora is offline   Reply With Quote
Old 07-21-2011, 04:44 AM   #24
Elite Member
iTrader: (4)
 
MartinezA92's Avatar
 
Join Date: Aug 2009
Location: Mountain View, CA
Posts: 1,702
Total Cats: 28
Default

God ******* dammit.
I should probably weld my pinion shaft too. Does anyone have more detailed pics/instructions? I feel like it is being made to sound more difficult than it really is...

I looped the lines when I pulled my engine and have not touched it since. There is a considerable amount of slop in the steering wheel.
MartinezA92 is offline   Reply With Quote
Old 07-21-2011, 04:54 AM   #25
Senior Member
 
Join Date: Dec 2004
Location: Brisbane, Australia
Posts: 1,272
Total Cats: 32
Default

I did this mod to my NB and it is baller. I didn't weld the pinion just removed the seals. Makes the car feel like a little go kart!
timk is offline   Reply With Quote
Old 07-21-2011, 05:41 AM   #26
Elite AbsurdFlow Member
 
Laur3ns's Avatar
 
Join Date: Mar 2008
Location: Enschede, NL
Posts: 2,058
Total Cats: 11
Default

What about the whole overheat-during-welding-issue-and-killing-the-rack-shortly-after story?
Laur3ns is offline   Reply With Quote
Old 07-21-2011, 07:47 AM   #27
I'm Miserable!
 
Join Date: Feb 2010
Posts: 584
Total Cats: 0
Default

It's an easy project really. Really. It's simply unfamiliar to most. Everything seems weird the first time you open up a manual transmission too. But they are also relatively simple.
sjmarcy is offline   Reply With Quote
Old 07-21-2011, 08:58 AM   #28
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by Thucydides View Post
I've got mixed feelings about this. On the one hand it works for you and you like the feel. On the other, there are probably better ways to dampen the rack that won't wear it prematurely. That pre-load you've put on the rack collar will wear the nylon cover pretty quickly, and before long most of the preload will be gone.

Have you already dialed in all the caster you can? You can also install an external damper. Another possible way to slow things down is to leave in the piston, fluid, and loop the lines so the piston pumps the fluid from one side of rack chamber to the other. You might be able to adjust the damping by adjusting fluid viscosity.
Good grease will stop friction.

lol @ external damper

Slowing it down with the looped lines makes it too hard to turn, been there, done that.

Caster won't make the steering heavier, it will make it harder to turn and easier to spring back.
hustler is offline   Reply With Quote
Old 07-21-2011, 10:58 AM   #29
Elite Member
iTrader: (2)
 
Join Date: Jan 2007
Location: Los Angeles, CA
Posts: 8,782
Total Cats: 119
Default

The most complicated car mod to grace miataturbo.net???
Faeflora is offline   Reply With Quote
Old 07-21-2011, 11:22 AM   #30
I'm Miserable!
 
Join Date: Feb 2010
Posts: 584
Total Cats: 0
Default

Quote:
Originally Posted by Spookyfish View Post
What about the whole overheat-during-welding-issue-and-killing-the-rack-shortly-after story?
Rubbish.
sjmarcy is offline   Reply With Quote
Old 07-21-2011, 11:30 AM   #31
I'm Miserable!
 
Join Date: Feb 2010
Posts: 584
Total Cats: 0
Default

Quote:
Originally Posted by Faeflora View Post
The most complicated car mod to grace miataturbo.net???
Boost is for motors, not steering.
sjmarcy is offline   Reply With Quote
Old 07-21-2011, 11:37 AM   #32
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by Faeflora View Post
The most complicated car mod to grace miataturbo.net???
It's pretty easy unless you're a trophy-bottom.
hustler is offline   Reply With Quote
Old 07-21-2011, 11:49 AM   #33
Elite Member
iTrader: (17)
 
Join Date: Aug 2007
Location: Fort Myers, FL
Posts: 2,791
Total Cats: 130
Default

Quote:
Originally Posted by Faeflora View Post
What the ever living **** are you saying? I accept responsibility for failure to comprehend, but this makes me question god's purported benevolence.

It sounds like this is the most complicated thing ever.

I just want my **** to feel good and not wear out and be horrible.
At least I'm not the only one that feels this way.

This seems like one of those things where I finally build up the confidence to pull it all apart, screw everything up, have to buy another rack, wait for it to get delivered, and after a month of not being able to drive my car and spending $200. I'll be able to put it back to the same looped lines I had before I started.
pdexta is offline   Reply With Quote
Old 07-21-2011, 12:00 PM   #34
I'm Miserable!
 
Join Date: Feb 2010
Posts: 584
Total Cats: 0
Default

Quote:
Originally Posted by pdexta View Post
At least I'm not the only one that feels this way.

This seems like one of those things where I finally build up the confidence to pull it all apart, screw everything up, have to buy another rack, wait for it to get delivered, and after a month of not being able to drive my car and spending $200. I'll be able to put it back to the same looped lines I had before I started.
Good judgement comes from experience. Experience comes from bad judgement.

I'd suggest that if you are very new to mods like this…hire it out. Or DIY using an extra rack so that you have no down time and it's less stressful. You need tools like snap ring pliers, various sized sockets to punch out seals, five minutes of access to a welder, and the interest. The second time you do one will take a fraction of the time of the first.
sjmarcy is offline   Reply With Quote
Old 07-21-2011, 12:01 PM   #35
Junior Member
 
Join Date: Jun 2008
Location: Fairfield, California
Posts: 418
Total Cats: 0
Default

Quote:
Originally Posted by hustler View Post
Good grease will stop friction.
So the grease defeats the friction you added by over tightening the rack pre-load.

Quote:
Originally Posted by hustler View Post
lol @ external damper
Yeah; what was I thinking. Race cars never have steering dampers; those are for monster trucks. Oh wait:

http://forum.britishv8.org/read.php?7,17819,23898

Quote:
Originally Posted by hustler View Post
Slowing it down with the looped lines makes it too hard to turn, been there, done that.
I agree, but then I don't crank down my pre-load either because I don't have problems with too light a steering on my de-powered racks.

Quote:
Originally Posted by hustler View Post
Caster won't make the steering heavier, it will make it harder to turn and easier to spring back.
Well, perhaps I don't know what you mean by making the steering heavier, and why you think you need it. Perhaps the problem you're trying to fix with the steering originates somewhere else in the suspension, and you're using a band-aid instead of solving it.

Last edited by Thucydides; 07-21-2011 at 12:12 PM.
Thucydides is offline   Reply With Quote
Old 07-21-2011, 12:17 PM   #36
I'm Miserable!
 
Join Date: Feb 2010
Posts: 584
Total Cats: 0
Default

Spend some time driving a Lotus….now THERE is excellent steering and feel. I've had three over time, from Europas to the Elise. BTW, those cars are all so light that you can kneel down by a front wheel and "turn" it, watching the steering wheel spin inside the car. Try that on nearly any other car if your arms are not the size of legs.

On modded Miatas, it would be nice to see drop-spindles used to keep the articulation happy at low ride heights. Much lowered Miatas suffer from various issues which harm the steering characteristics.

You can feel the sport-driving steering improve as you go from power to looped-line manual to tweaked-manual steering.
sjmarcy is offline   Reply With Quote
Old 07-21-2011, 01:10 PM   #37
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by Thucydides View Post
So the grease defeats the friction you added by over tightening the rack pre-load.

Yeah; what was I thinking. Race cars never have steering dampers; those are for monster trucks. Oh wait:

http://forum.britishv8.org/read.php?7,17819,23898

I agree, but then I don't crank down my pre-load either because I don't have problems with too light a steering on my de-powered racks.

Well, perhaps I don't know what you mean by making the steering heavier, and why you think you need it. Perhaps the problem you're trying to fix with the steering originates somewhere else in the suspension, and you're using a band-aid instead of solving it.
Define "over-loaded". Actually, don't. If you're so dense that you think I added 100lb/ft instead of something reasonable then you're beyond hope. This also reduced the slop.

Fab up a steering damper for me, for free.

I added a little pre-load because I like the way Porsches steer more than BMW feel. Maybe you can ask Porsche about their suspension problems.
hustler is offline   Reply With Quote
Old 07-21-2011, 01:18 PM   #38
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by sjmarcy View Post
Spend some time driving a Lotus….now THERE is excellent steering and feel. I've had three over time, from Europas to the Elise. BTW, those cars are all so light that you can kneel down by a front wheel and "turn" it, watching the steering wheel spin inside the car. Try that on nearly any other car if your arms are not the size of legs.
Maybe I like the heavier steering because I'm so pumped and masculine. I drove a Porsche once and fell in love with the heavy steering. You could still feel the pavement texture through the wheel, but I felt like the wheel was nice and heavy. In my daily driver Miata, it's too whippy and I saw at the wheel.
hustler is offline   Reply With Quote
Old 07-21-2011, 01:52 PM   #39
I'm Miserable!
 
Join Date: Feb 2010
Posts: 584
Total Cats: 0
Default

Quote:
Originally Posted by hustler View Post
Maybe I like the heavier steering because I'm so pumped and masculine. I drove a Porsche once and fell in love with the heavy steering. You could still feel the pavement texture through the wheel, but I felt like the wheel was nice and heavy. In my daily driver Miata, it's too whippy and I saw at the wheel.
I hear ya…well I don't have 22 inch pythons attached to my shoulders like Hulk Hogan haha. I love German car control-efforts. The solid brakes, heck the whole car is solid.

Part of the thing about Miatas is that the wheelbase is so short. If you think about it…that can create some steering issues at high speeds that will certainly catch your attention. The Lotus car also has a short wheelbase but they manage it fairly well. For instance they use deliberate and coordinated front/rear bump steer to good effect. And a goal chassis torsional rigidity has been achieved. A nice thing about the small Loti is their initial turn-in…the next time you drive one pay close attention to it. They have their issues, but there is absolutely zero whippy steering feel at speed.

Much of your concerns with Miata steering could be ameliorated via new front uprights and similar design level changes. When you design a suspension system, the uprights are one of the core assumptions. And ours were designed to be cheap while handling stock power levels and speeds.
sjmarcy is offline   Reply With Quote
Old 07-21-2011, 02:09 PM   #40
I'm Miserable!
 
Join Date: Feb 2010
Posts: 584
Total Cats: 0
Default

Here is a rack I converted to manual. I like to clear coat the aluminum casting after steel brushing it once it has been degreased. This fills in the casting pores so that it stays clean and shiny. On this one I cut off the nipples that live on the black tubular section. It just looks sleeker. Fluid line ports on the alloy casting were JB Welded flush, as you can barely see in the picture.

https://www.miataturbo.net/attachmen...1&d=1311268120
Attached Thumbnails
Thoughts on de-powering the rack?-rack.jpg  
sjmarcy is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Moroso Air Oil Separator Catch Can Aroundcorner Miata parts for sale/trade 2 10-01-2015 04:20 PM
Time to start learning and play with tuning The Gleas MEGAsquirt 3 10-01-2015 10:30 AM
Walbro 255lph Fuel Pump $50 lsc224 Miata parts for sale/trade 2 10-01-2015 10:17 AM
Odd Steering issue interestedofold Suspension, Brakes, Drivetrain 5 09-29-2015 02:42 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 02:46 AM.