Secrets of the Mirage

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Loren Williams
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Secrets of the Mirage

Postby Loren » Thu Apr 26, 2018 8:06 pm

I did think about doing that. But, the cutting head that I used to cut the hole initially really wonked out my drillpress. I need to do some work on the drillpress before it would be able to use it. My drill chuck currently has about 1/8" of wobble in it. It's not pretty.

Joe's going to try to make a quick jig to put it on his lathe and re-bore the holes that way. Should work, and yield a nicer hole.
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The "Push Harder, Suck Less" philosophy explained:
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Suck Less - Drive something resembling a proper racing line.
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Postby Loren » Sat Apr 28, 2018 5:12 pm

With a little help from Joe and his lathe, we got the caster plates completed this morning. And this afternoon I installed them on the car. While I was at it, I raised the car about 1/4", and also lengthened the rear shocks by another 1/4". Hopefully, that will keep the rear tires out of the fenders without me having to roll them.

Ended up with about 3.2-3.4 degrees negative camber in the front, zero toe. And if my measurements are anywhere near correct, I had 2.8 degrees of caster, and now I have about 4.1. Honestly, I think I'm not measuring/calculating the caster correctly. Maybe I didn't measure with the wheel turned far enough? If we scale those numbers up... I probably started with closer to 4 degrees, which means I should have about 6 degrees now. And I absolutely DID move the top of the strut back by 7/8". 7/8" over the length from the strut bearing to the lower ball joint (23", I think) is 2.18 degrees. So, I should have gained at least 2 degrees of caster.

The difference in caster can be felt. It's not night and day, but it's there. Just one more little piece of the puzzle. The car is feeling really good.

Oh, and the caster moved the wheel aft by maybe 1/2" at the most. No clearance problems. All is well.

What? Oh, you want photos?

Before and After:

ImageImage

Hmmm... I need to check the protrusion of the new bolts through the bearing assembly.

Top View:

Image

Installed:

Image
Loren Williams - Loren @ Invisiblesun.org
The "Push Harder, Suck Less" philosophy explained:
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Suck Less - Drive something resembling a proper racing line.
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Postby Native » Sat Apr 28, 2018 5:33 pm

Very cool. Nice fabrication!
And functional, to boot... :thumbwink:
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I'll get to it. Eventually...
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Postby Carracer » Sat Apr 28, 2018 5:38 pm

That is just awesome!
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Postby jbrannon7 » Sat Apr 28, 2018 5:55 pm

Today while working on Loren's plates I learned a fun fact, SAE counter sunk screws are 82 degrees and Metric countersunk screws are 90 degrees. Also if you want more surface, like attaching thin aluminum skin to wing spars, aviation screws are 100 degrees.
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Postby CaptainSquirts » Sat Apr 28, 2018 6:10 pm

Noooo, rest in peace camber adjusting plates.
Loren Williams
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Postby Loren » Sat Apr 28, 2018 7:09 pm

jbrannon7 wrote:Today while working on Loren's plates I learned a fun fact, SAE counter sunk screws are 82 degrees and Metric countersunk screws are 90 degrees. Also if you want more surface, like attaching thin aluminum skin to wing spars, aviation screws are 100 degrees.
I was wondering about that. Good to know.

Some further driving along familiar roads, and the effect of 2 degrees of additional caster is becoming more apparent. It doesn't so much make the steering feel more responsive as it makes it just FEEL. You feel more in touch with the car when you're turning. A little more driver feedback. But, not so much that it affects steering effort. Good stuff!
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Suck Less - Drive something resembling a proper racing line.
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Postby CaptainSquirts » Sun May 06, 2018 1:23 pm

Consensus on Caster for autocross?
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Postby Loren » Sun May 06, 2018 1:26 pm

The more I drive the car, the more I like it. Steering used to always feel a little vague no matter what I did to the car. Now it feels crisp and responsive. Feels REALLY good on typical back road sweeping turns. And it felt good in the slaloms and the turn-around on our last course.

In general: as long as you have power steering and aren't going to make your steering effort too high, it seems like a couple degrees more caster is a good thing just for the improved feel. It also comes with the added benefit of a little more camber while turning. Good stuff!
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The "Push Harder, Suck Less" philosophy explained:
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Suck Less - Drive something resembling a proper racing line.
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Postby CaptainSquirts » Sun May 06, 2018 1:36 pm

:thumbwink: good to hear, its my next upgrade.
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Postby Loren » Wed May 09, 2018 4:19 pm

I don't remember if I noted this in here before, but sometime recently, I picked up a "groan" in the steering. Typical steering inputs would generate a groan from... somewhere... as you turned the wheel. I thought it was the funky spring stack I'd put in the front first, but after I went back to the original single spring setup, the noise was still there. Then I thought maybe it was the upper strut bearings. Went as far as to put some oil on them, but that didn't seem to be it. Next I was thinking that the bump stops that I put in the front might be binding on the shock shaft and the strut bearing... maybe making some noise somehow? I gave that a good look last week, and that was all I could come up with. It seemed a lot like the kind of noise you'd get from a failing upper strut bearing.

Yesterday, I went at it again, determined to find the problem. Jacked up the car so that I could swing the wheel from side to side. Was readily able to duplicate the noise... and after a few minutes, I was able to rule out the bump stops... and then I found that I could sort of feel the vibration when I put my hand on the tie rod. My tie rod ends are unsealed heim joints. They're still quite new, not a hind of rust or anything. But, I gave each of them a shot of penetrating oil. And that took care of it! No more noise.

So, I guess I need to put a drop of oil on those tie-rod ends, and probably the equally exposed upper strut bearings, every couple months to keep them happy.
Loren Williams - Loren @ Invisiblesun.org
The "Push Harder, Suck Less" philosophy explained:
Push Harder - Drive as close to the limit of your tires as possible.
Suck Less - Drive something resembling a proper racing line.
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Postby Loren » Sat May 12, 2018 2:21 am

Raised the rear of the car another half inch today. It was still munching the edge of the tire tread occasionally on bumps. (still doesn't seem to be doing it at autocross because I run with the rear shocks full stiff)

And...

I started looking into exhaust headers again. There are at least 3 companies that make them. One seems to be a myth. One is fairly easy to find. The other one is not as easy to find, but ended up having the best communication, good information, and a great looking product at a very reasonable price.

So, I've ordered a SuperCircuit Exhaust Header. And I've started planning the cat-back to go with it. $306 shipped for the header, and I should be able to put together a cat-back for under $200.

https://www.facebook.com/pg/SUPERCIRCUI ... 1253095374

Powerrrrrr!
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Suck Less - Drive something resembling a proper racing line.
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Postby twistedwankel » Sat May 12, 2018 9:20 pm

Malaysia? I don't get FB so don't know. Looks nice. Might be hard for you to stay under 96db tho'. I was told pipes pointing straight up at the back make less db than pointed to the ground.

You should visit Rob and ask him: "What is this budget thang you speaketh of?" :chuckle:
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Postby Loren » Sat May 12, 2018 9:49 pm

96db? I don't want the car to be much louder than 89db!

I figure replicating the stock exhaust (rear cat, round muffler, and resonator at the end) using larger tubing (2 inch) and mandrel bends should open up the flow enough without adding too much volume.
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The "Push Harder, Suck Less" philosophy explained:
Push Harder - Drive as close to the limit of your tires as possible.
Suck Less - Drive something resembling a proper racing line.
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Postby CaptainSquirts » Wed May 16, 2018 11:47 am

Why did you go back to the single spring?
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Postby Loren » Wed May 16, 2018 12:37 pm

Because the dual spring wasn't compressing enough to bind the shorter spring and make it effective. I didn't want to spend big bucks on the correct spring set to make it work. So, I went back to the original single spring. Simplicity.
Loren Williams - Loren @ Invisiblesun.org
The "Push Harder, Suck Less" philosophy explained:
Push Harder - Drive as close to the limit of your tires as possible.
Suck Less - Drive something resembling a proper racing line.
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Postby Loren » Thu May 17, 2018 10:59 pm

Cute little 3-pipe header is on its way from China. Malaysia, actually. About 900 miles from where the car was built in Thailand.

I've had a pretty slack schedule this week, so I spent some time researching exhaust design and come up with a good exhaust plan. Decided to change my plan from 2" cat-back to 1.75". Why? Because those who know will tell you that it's all about keeping the exhaust velocity up, and if you go TOO large on the pipe, velocity goes down. That's great if you have a turbocharger, or if your goal is maximum high-rpm horsepower. But, I'm autocrossing in a low-powered car... the last thing I need to sacrifice is mid-range torque!

The OE pipe is 1.5" OD, about 1.45" ID. I found a reference that states a 1.5" OD pipe is good for max 78 hp. Go figure. 1.75" is good for a little over 100, which is about 10 more than I ever expect to see with this engine. 2" would be overkill, and I think it would hurt the usable torque. Plus, it would add a few pounds of unnecessary weight.

Unfortunately, the smallest high-flow cat available is 2" ID. So, I'll make the first part off of the header 2" into the oversize cat. That should almost guarantee that the cat isn't a significant restriction to exhaust flow. Then I'll neck down to 1.75" for the rest of the system.

Fortunately, small pipes and components are CHEAP. Magnaflow cat, Walker muffler, Jones resonator, and a few J-bends add up to just under $150! I'll probably pull the trigger on that later this month.

For ease of fitment and serviceability, I'll be making the front part with the cat a separate flanged piece, and the rest will be an actual "cat-back".

Using components that are very similar to stock, I don't expect it to be a great deal louder than stock. Being larger pipe, and replacing two 1.5" cats with a single high-flow 2" cat will surely make it a LITTLE louder. But, that's okay. Maybe you'll hear it coming. And it will intimidate you. :twisted: Or not.
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The "Push Harder, Suck Less" philosophy explained:
Push Harder - Drive as close to the limit of your tires as possible.
Suck Less - Drive something resembling a proper racing line.
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Postby twistedwankel » Thu May 17, 2018 11:18 pm

Loren wrote:And it will intimidate you. Or not.
I'm starting to get the picture. Tiny is still tiny. Snails will always be slow until they lose their Shell (not gas).

Shell has a 3/4 clam.
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Postby Loren » Tue May 29, 2018 11:22 pm

12 days later... my header has finally appeared at a USPS facility in Los Angeles!
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The "Push Harder, Suck Less" philosophy explained:
Push Harder - Drive as close to the limit of your tires as possible.
Suck Less - Drive something resembling a proper racing line.
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Postby CaptainSquirts » Thu May 31, 2018 4:08 pm

Will it be installed before this sunday?

Image

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