proxlamus©
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Posts posted by proxlamus©
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ugh error
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You didnt look hard enough..
From JMortensenPosted 29 August 2005 - 08:49 PM
Bumpsteer FAQ
Bumpsteer is a condition where the toe changes as the suspension moves through its travel. It is generally not noticeable on street cars unless they are being driven "arrest-me-officer" fast, but is an important factor with regards to how a race car handles at the limit. Bumpsteer curves can be plotted out, and generally they follow the following rules: when the suspension droops the wheels toe in, and when it compresses the wheels toe out.
A car suffering from too much bumpsteer generally has the following symptoms: Bumps in the road hit by one wheel cause the car to jerk in one direction or the other even though the steering wheel does not move. When driving through a bumpy turn the wheel must be constantly moved back and forth in order to keep the car traveling in a continuous arc.
Why does my Z have bumpsteer in the first place?
Bumpsteer is engineered into most cars direct from the manufacturer. They use bumpsteer as a safety mechanism. The more the suspension compresses, the more the front tires toe out. When you turn very sharply and load the outside front suspension that tire toes out and makes the car want to take a straighter path. This will contribute to understeer and understeer is considered to be a safer and easier condition to control than oversteer.
What causes bumpsteer?
Bumpsteer is caused when the tie rod and control arm are different lengths, or sit at different angles, or a combination of the two. In a Z the tie rod and control arms are the same length from the factory, so the issue in the Z is that the two are at different angles.
How do I measure bumpsteer?
Bumpsteer can be measured with a bumpsteer gauge. Wasn’t that easy?
A bumpsteer gauge is basically a glorified pair of dial indicators. Usually a bumpsteer gauge comes with a steel or aluminum plate which gets strapped to the wheel. A stand sits next to the front tires that holds the dial indicators in contact with the plate. The suspension is moved up and down, and the front and back dial indicators are compared to measure the toe change. Unfortunately, you want to do this measurement right in the car’s normal ride height, and through a couple inches of suspension movement on either end of that ride height. To accurately measure the front springs and sway bar must be removed, then the car must be placed at ride height with relation to the suspension and moved up or down while monitoring the toe change on the dial indicators.
How do I “fix†bumpsteer?
There are many ways to fix bumpsteer. Probably the most common modification available is the bumpsteer spacer which can be purchased from just about any Z parts supplier. This is a spacer that fits between the bottom of the strut and the control arm, and “restores factory geometryâ€. It doesn't really restore factory geometry, and it really does not fix bumpsteer either. What it will do is return the ROLL CENTER to a position closer to stock on a lowered Z. What bumpsteer spacers really do is raise the roll center of the car which makes it have less body roll in turns with a given spring rate. The bumpsteer spacer does not eliminate bumpsteer.
The next most common modification is the JTR crossmember modification or some variation of it. This involves redrilling the control arm hole up ¾†or 15/16" and out ¼†in order to reduce bumpsteer and add negative camber at the same time. Moving the pivot out ¼†will gain more negative camber, but it also exacerbates bumpsteer, because now the control arm length is now shorter than the tie rod length. Again, this approach will be helpful to the roll center, but will not “cure†bumpsteer unless the pivot is moved to the correct height. In order to know what the correct height is you really need to measure on YOUR car, because a 30 year old car is going to vary chassis to chassis, plus some people want to run the "bumpsteer spacer" to raise the roll center AND fix the bumpsteer in addition to that.
Now we’re into the not-so-common methods for dealing with bumpsteer. One method I have used is to slot the front crossmember. I did this by drilling a hole directly above the original control arm pivot hole then connecting the two holes with a cutoff wheel. I then measured the bumpsteer with a gauge and adjusted the pivot up until it was at 0. I've run my Z this way for more than 5 years, autoxing and doing track days on slicks and have not had the pivots move at all.
So far all of these methods have dealt with moving the inner or outer end of the control arm in relation to the tie rod. It is equally possible to move the tie rod.
One way to move the tie rod is to modify the steer knuckle that the outer tie rod attaches to so that it will accept a common bumpsteer spacer kit. These kits are very common in road racing and circle track racing, and generally replace the outer tie rod with a rod end, then use spacers to move the rod end up or down in relation to the steer knuckle. Cary (tube80z) has pointed out that a standard bridge ream can be used to ream out the hole in the steer knuckle. The bridge ream has the same taper as a Ford, so a Pinto bumpsteer spacer kit available from any circle track racing parts supplier will work once the steer knuckle has been modified. One issue with modifying bumpsteer on the tie rod end is clearance between the wheel and the tie rod. Sometimes there is not enough room to move the tie rod down far enough to get rid of the bumpsteer.
Another way to move the tie rod is to raise or lower the steering rack, which then raises or lowers the inner tie rod. This is not an easy option in a stock Z, but can be done with some fabrication if desired.
Where do I want the bumpsteer to be?
Opinions vary. Some like me prefer 0 bumpsteer, some like John Coffey prefer to tune the car by changing the bumpsteer and roll center characteristics by varying the thickness of bumpsteer spacer used. What is a fairly universal idea is that little toe out on compression makes the car more forgiving and toe in on compression is not a good thing.
Is bumpsteer worth messing with?
If you have to ask this question it probably isn’t worth it. 99% of street drivers will never notice bumpsteer or will consider it cured by the JTR mod or a bumpsteer spacer. For those that do drive hard enough to notice it can be very worthwhile.
Modifying your suspension is potentially dangerous and you do so at your own risk.
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I have the 60 gallon Husky compressor from The Home Depot, which regulator did you purchase?! Mine has a built in pressure gauge and a plastic adjusting knob from Husky. http://www.homedepot.com/h_d1/N-5yc1vZ1xhf/R-100082550/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053
That's a very bizarre problem you have. My compressor is set up this way: Compressor > Shut off ball valve > regulator > water separator > hose
I severely doubt that changing the regulator and water separator around will make much of a difference.. Have you called Husky's customer service?! I wouldn't recommend going to Home Depot and talking to a hardware associate, depends on the associate, but most won't have a clue.
1-888-HD-HUSKY
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bump for a very interesting read =)
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a little bump..
anyone else wanna chime in?!
I need to do some research, but can I apply POR-15 then an undercoating?! hurm
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So I've been sanding my car down with a dual action sander, wire brush, grinding disc and soda blasting and I'm having a difficult time getting the paint down to the bare metal.
If I use a 80 grit sand paper and sand down through the original clear coat and partially between the paint and primer in certain spots, is it necessary to strip the paint ALL the way down to the metal or primer for a re-spray?!?!
There are areas on the underbelly where I was able to get the factory undercoating off, but not the yellow-ish primer. This is the same on the interior of the car as well... I'm worried the primer and paint won't stick unless I take it all off.
Am I being overly cautious or is it ok to paint over a very well sanded original paint/primer??!
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ohh good ol Colorado.
I have winds gusting to 45 mph right now with freezing rain pelting my windows in my room. grr
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I've been browsing around on different fuel options..
I know a lot of guys don't recommend a fuel cell unless I opt for a good $1,000 unit with a bladder and foam core..
I've seen a lot of guys weld on a fuel tank sump and then a lot of guys who have welded up a surge tank off to the side.
Unfortunately I don't know a whole lot about the major differences and I was hoping to get some input.
- My plan was to use the factory 280z tank, weld up a surge tank and run the low and high pressure pumps.
Would there be any benefit to welding on a fuel sump on the bottom of the (280z efi) tank with a separate surge tank??
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the fuel cell is a good option, but I have read that if your going to do it, opt for a nice aluminum unit with a bladder and foam on the inside.. which can go up to $1,000!!? a lot of guys wish they kept their factory tank and welded on a sump.
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haha.. after working at Home Depot for the past 5 years.. I will completely agree with this thread =)
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Well, that's a first. Never before have I heard of anyone comparing a street driven 240Z with a purpose built WRC rally car in a safety discussion. You appear to have already made up your mind and are now just fishing to get someone to give you an "Internet OK" while using a irrelevant example as proof. Good luck with that.
EDIT: I know that's sounds bit harsh, but... but... Geez!
Oh John,
Im not comparing a 240z to a WRC car.. I just wanted to bring up a WRC car as an example of modifying the floor-pan, the seats and the seat mounts to allow adequate headroom for a cage. I was hoping to see that maybe someone may have done the same.
I have not made up my mind until now and I'm glad people are chiming in their opinions.. I have decided to go with only a half cage, after hearing the opinions of people who talk from experience.
Thanks guys!
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yeeehh pics pics!
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what are you doing about the spare tire well?
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Wow! thanks for the great response guys!
I am defin. going to grab a 3.54 =)
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So im debating between a full and half cage..
I realize that a half cage is recommended for any car that is ever used on the street, but after watching tons of WRC racing.. Ive realized that these cars are driven for many many many many miles between the rally stages and they don't wear helmets..
the WRC cars have the seats mounted very low with plenty of headroom above their heads and the halo/roll bar
Help me make sense of this.. in the event of an accident, if my head moves it will smack the roll bar.. without a roll bar and my head moves an extra 1 1/2" my head will hit the upper door frame?!?! I just dont see the big difference an 1 1/2" will make.. especially with nice padding!?
Has anyone used SIDE seat mounts and mounted the seats super low and had issues with head room?!
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Tim, pm sent.
Richard, thank you for the reply!! If things fall through with the local source, I will contact you! Thanks again!!
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Im still interested!
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I agree.. I should of paid a shop to do it.. dumb mistake.. its my first car, so another learning experience and lesson learned.
I will however be able to use the soda/abrasive blaster for suspension parts and a blast cabinet. so its not a total waste.
I found a cheap local source for soda bicarbonate.. harbor freight wanted $39 for a 50 lb bag... I found a place in town that sold me 100 pounds of soda bicarbonate AND 100 pounds of nickel slag 90 grit for rust removal for $55 after taxes!! What a deal!!! 200 pounds for $55?! sold!! =)
All of the sand Home Depot sells (quickrete)states on the bag and instructions DO NOT use for sand blasting.. silicosis anyone?! The nickel slag seems pretty sweet for the rust removal.. its also called the "green diamond" and less then 1% silica
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not really sure why you copied and quoted my old post zgeezer, with nothing else added after the quote???!
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I have a moon/sun roof on my '78 280z..
I am looking for a clean roof skin or a cut off roof from the upper a-pillars and b-pillars.
Anyone have anything?! thanks guys
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No offense.. but I think it would be of some benefit to find a clean 240z and a RB front clip, McKinney's motor mount kit for a RB and drop it off to a shop and have them do the work.
I mean a stock 2004 Sti at the lowest is around $20k... plus all of your mods...
You can easily build a 240z with an RB and have a shop do all the work for WELL under that.
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Ive learned a few things over the past week or so..
First.. use a Dual Action Sander on the car, then use the sandblaster for hard to reach areas
Second.. if you build an enclosure like I did.. I tried using duct tape and 3 mil plastic and PVC for a frame. I would duct tape the plastic to the PCV, which didnt turn out to be too successful. I had leaks all over when I put the booth in positive pressure and the plastic would fall all over the place. I bought a can of Heavy Duty Spray Adhesive.. which is AWESOME. It really seals the booth and I havent had any issues with the plastic falling apart or leaks causing my garage to be encapsulated in a cloud of dust
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Oh BTW... I would NOT recommend blasting an entire car with this.
It will simply take too long and the bags of media will add up very very fast. I would take it to a shop or RENT a towable blaster.
I will use this for blasting parts and getting into the cracks and areas that a hand sander cant reach.
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Im running a 60 gallon Husky air compressor. 135 PSI maximum pressure and air delivery 11.5/10.2 SCFM @ 40/90 PSI.
As for duty cycle.. I have no idea what that means .. haha. sorry. It pretty much runs ALL the time while im blasting.
I usually have to give the pressure pot a big shake to get the soda down the in siphon, every few minutes or so.. but I dont have any problems with the compressor running out of air.
AFR compensation for elevation
in Wolf3D
Posted · Edited by PrOxLaMuS©
damnit.. my reply didn't post
The stoichiometric air/fuel mixture for gasoline powered engines is 14.7. This does NOT change with altitude.. the air density and oxygen levels change with altitude which require less fuel.
Even airplanes taking off at sea level and climbing to 18,000 msl need to adjust the air/fuel ratio to aim for the proper AFR/EGR temp for max power and fuel economy.
Your car will need to be tuned at altitude, but once again, the AFR numbers will remain the same. 11-12 afr under load/boost, 12-14 moderate loads, 14-16 afr rich/low cruise