Prepared Car Support Group - Page 3 - MR2 Owners Club Message Board
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post #41 of 363 (permalink) Old March 12th, 2009, 19:46
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The front bumper can support itself using the radiator support and fenders. There is strips of studs that connect everything. The rear bumper will require brackets to be made.
i personally left my rear bumper off.
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post #42 of 363 (permalink) Old March 13th, 2009, 09:16 Thread Starter
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Quote:
Originally Posted by zipty842
The front bumper can support itself using the radiator support and fenders. There is strips of studs that connect everything. The rear bumper will require brackets to be made.
i personally left my rear bumper off.
I agree regarding the front bumper. Once it is gutted it holds pretty well to the upper radiator support, and the fenders. See here: http://www.pbase.com/mtb_zack/image/109738887

On V1.0 (my first chassis) I gutted the bumper, welded in two short L bars and supported the rear bumper with some hood pins, and Zip ties. I planned on filling it with foam. You can see here: http://www.pbase.com/mtb_zack/image/98010323

I am thinking of another sloution now for V2.0, the hardtop.

Last edited by mtbmr2; March 13th, 2009 at 09:20.
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post #43 of 363 (permalink) Old March 14th, 2009, 12:34
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Aw11

thanks for the input on the front bumper, last night went out and removed these items

lower weighs 18 lbs upper 3 lbs





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post #44 of 363 (permalink) Old March 15th, 2009, 01:52
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im really interested in your feedback in regards to these spring rates. I seem to be having a little more understeer than id like with the 600front/350/375/400rear set up. Id like to try and up the rate to 450lbs/in in the rear, but im weary on leaving the front rates at 600lbs/in, so im going to wait until I get feed back from you guys. Maybe its just me.
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post #45 of 363 (permalink) Old March 16th, 2009, 12:42
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Verno-dub; understeer??? You shouldn't be getting understeer. Send me an email so we can talk about what's going on.

I made a set of brackets for my rear bumper from aluminum angle. Light, cheap, easy and holds the bumper in place nicely. I hated the way the car looked without the rear bumper cover.

-Steve
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post #46 of 363 (permalink) Old March 16th, 2009, 14:06
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Have you played with the settings on your dampers? I've been fooling around with my konis, and a half turn makes all the difference in the world when it comes to how the thing drives.
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post #47 of 363 (permalink) Old March 16th, 2009, 16:31 Thread Starter
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Tonight, I plan on cutting and installing the Lexan for the rear quarter windows. For now we will re-do the alignment, make sure the brakes are bled well, tighten everything down properly, and go racing in two weeks.

I have lots of aluminum sheeting to build the rear deck, and clean up the interior with once the next couple of events shake out the car. I have also order a few carbon fiber sheet samples to be sent to me. I can't help it, I love the stuff.

Quote:
Originally Posted by sliverstorm
Have you played with the settings on your dampers? I've been fooling around with my konis, and a half turn makes all the difference in the world when it comes to how the thing drives.
Yes, I had done some testing on well worn asphalt. I'll say that there is a definite corner-off understeer that develops with excessive rebound damping in the front.

However, take that piece of data with the fact I need to completely cure my bumpsteer issues.

Quote:
Originally Posted by verno-dub
im really interested in your feedback in regards to these spring rates. I seem to be having a little more understeer than id like with the 600front/350/375/400rear set up. Id like to try and up the rate to 450lbs/in in the rear, but im weary on leaving the front rates at 600lbs/in, so im going to wait until I get feed back from you guys. Maybe its just me.
I can't report any understeer that I didn't semi-knowingly create. If anything the car might be a little loose transitionally, I never got to test in a slalom, just a never-ending circle rights (or lefts) around our block in the industrial complex.

Last edited by mtbmr2; March 16th, 2009 at 16:42.
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post #48 of 363 (permalink) Old March 16th, 2009, 20:39
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Quote:
I can't report any understeer that I didn't semi-knowingly create.
Same here, but then again, my runs were in an inch of water. :P

My lexan is getting cut this week too
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post #49 of 363 (permalink) Old March 18th, 2009, 09:59
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Quote:
Originally Posted by verno-dub
im really interested in your feedback in regards to these spring rates. I seem to be having a little more understeer than id like with the 600front/350/375/400rear set up. Id like to try and up the rate to 450lbs/in in the rear, but im weary on leaving the front rates at 600lbs/in, so im going to wait until I get feed back from you guys. Maybe its just me.
Guys could you please share your findings here.. this is such a great post, and the suspense is killing me..

thanks
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post #50 of 363 (permalink) Old March 18th, 2009, 12:55 Thread Starter
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Quote:
Originally Posted by Shane Bawa
Guys could you please share your findings here.. this is such a great post, and the suspense is killing me..

thanks
Suspense? You mean suspension?

DISCLAIMER - My 'findings' are based on driving a car with an oil leak for 2-3 hours figuring out how I want it to handle. The notes are "as best as I can recollect". Although some of the numbers I know are dead on correct.

The "tester" car (my V1.0 car):
It weighed 1857 on that day, plus 200 pounds of me. 57% rear weight, 43% front, and corner weights were an atrocious 53/47, when I was in the car. (I have a picture somewhere of the scale read out) I never measured the ride height.

Suspension set up: 600F/Koni Yellows, 450R/Koni RACE. I had about 2-2.5-3 (?) degrees of camber front, about 1.5 in the rear, and toe was 1/8th out in the front and 1/8th in for the rear. (I would say that is way too much camber/toe for the front) The test "course" was rectangular block (4 - 90 degree turns) about 1/10 mile in total length, with well worn but "sharp" asphalt, with large aggregate (pebbles/rocks).

I had talked with Gordon Benson at Koni, and he recommended a couple of tests to set rebound damping using these. I will also state that "testing" a car to set it up can be tedious. Ideally you'd have a data logger that told you what was actually going on, because the butt-dyno is not that good.

The Protocol:
Drive the car at a set speed a couple times around your test course (closed site/street) in both directions. Then do it at full soft and full firm to notice the difference at the end you are setting. Make sure you are using inputs like you would on an autocross course.

For the fronts: Start at full soft (counter clockwise) and add damping in 1/4 turn increments until the car pushes transitionally (Turn-in/apex off). Then soften it about 1/8-1/4 turn and retest.

For the rears: Start at full firm (clockwise) and reduce damping in 1/4 turn increments until the car until the car pushes transitionally (Turn-in/apex off).

Repeat again for front and rear. (I stopped here due to my lil oil problem/church starting across the street)
Repeat process slowing into turns and accelerating out. Then repeat process driving at 90-100% concentration.

My Impressions:

My car had some mild bumpsteer in the front and probably the rear. That is #1 on my to-do list after the car actually survives an event.

Obviously, the yellows are a little over matched for the 600 springs on a bumpy surface. I had to go a little firmer (1 full turn) than I expected based (1/4-1/2 turn) on my email conversation with Gordon.

I liked the rear spring rate for the steady state turns of my "course". But it may make the car oversteer too much in slaloms, I don't know.

Once I actually get to an event, and get the car aligned the way I think I like, I'll go back and reset the rebound damping (only thing controllable with the single adjustable shocks)

Last edited by mtbmr2; March 18th, 2009 at 22:35.
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post #51 of 363 (permalink) Old March 18th, 2009, 21:55
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Hey everyone,
I bought a '85 DP last year and have been entering it in local auto-x and taking it to track days at VIR. The car has been slowly transitioning its way from street to "prepared" thru about three owners. It's still a long way off. So far it has the interior stripped, racing seats, auto power cage, Tokico adjustibles, Eibach lowering springs, MSD ignition, 5 point belts, HKS high lift cams, Flowmaster muffler, Greddy Emamage blue piggyback, and Hoosier A6 or Toyo Proxes RA1 205x50x15. I also moved the battery up front.
Next step is to change suspension to Steve's recommended set up, and get '87 brakes. Glad to find this sticky. I have lots of questions for my next post. Tried to send a picture from photobucket but it didn't work. I'll try again later.
David

Last edited by dka1; March 18th, 2009 at 22:01. Reason: picture didn't work
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post #52 of 363 (permalink) Old March 18th, 2009, 22:34 Thread Starter
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dk1 - welcome to the club! Sounds like you have a DP car ready to run! Who did you buy the car from? If I had your car, I wouldn't worry about changing the brakes to 87 spec. The bigger caliper brackets and rotors are extra unsprung weight. Even for a track day, the 85 spec should be withstand repeated braking zones.

Anyway, my latest progress is here: http://www.pbase.com/mtb_zack/image/110376980
I wish I could say I have the quarter panels windows installed, but I was hyper anal about cutting them and fitting them to the car. I got the wipers/motor and some more wiring out of the car.

Last edited by mtbmr2; March 18th, 2009 at 22:39.
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post #53 of 363 (permalink) Old March 19th, 2009, 11:38
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I've seen several people running 13" wheels and some 15". What are the pros and cons to wheel size?
David

Last edited by dka1; March 19th, 2009 at 11:45.
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post #54 of 363 (permalink) Old March 19th, 2009, 11:53
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Finally got an image. This is me at an event in Greensboro, NC. last summer.

David
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post #55 of 363 (permalink) Old March 19th, 2009, 13:26 Thread Starter
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Quote:
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I've seen several people running 13" wheels and some 15". What are the pros and cons to wheel size?
David
Most people in the class run 13x7 wheels. It is a compromise for maximizing contact patch with a minimal gearing penalty due to wheel diameter. 13 in wheels fit 20 (outer diameter) x 9 (tread width) x 13 (wheel size) cantilever slicks.

DP limits your maximum wheel size to 7" in width. Anything beyond that and you take a weight penalty of 75lbs +. Minimum weights are based on displacement. (For the MKI MR2 the formula is 1587 x 1.1 = 1745lb)

See SCCA Solo rule 17.4H and Appendix A "D-Prepared." You can download the pdf here: http://www.scca.com/contentpage.aspx?content=61
The SCCAforums "Prepared" Forum is well read by other Prepared compeitiors and rules makers: http://sccaforums.com/forums/30/ShowForum.aspx

Last edited by mtbmr2; March 19th, 2009 at 13:32.
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post #56 of 363 (permalink) Old March 19th, 2009, 13:39
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Quote:
Originally Posted by mtbmr2
Most people in the class run 13x7 wheels. It is a compromise for maximizing contact patch with a minimal gearing penalty due to wheel diameter. 13 in wheels fit 20 (outer diameter) x 9 (tread width) x 13 (wheel size) cantilever slicks.

DP limits your maximum wheel size to 7" in width. Anything beyond that and you take a weight penalty of 75lbs +. Minimum weights are based on displacement. (For the MKI MR2 the formula is 1587 x 1.1 = 1745lb)

See SCCA Solo rule 17.4H and Appendix A "D-Prepared." You can download the pdf here: http://www.scca.com/contentpage.aspx?content=61
The SCCAforums "Prepared" Forum is well read by other Prepared compeitiors and rules makers: http://sccaforums.com/forums/30/ShowForum.aspx
is that weight with or without the driver?

I saw D-mod was with the driver but did not see anything in prepared class

thanks
David
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post #57 of 363 (permalink) Old March 19th, 2009, 13:56 Thread Starter
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Quote:
Originally Posted by davegt27
is that weight with or without the driver?

I saw D-mod was with the driver but did not see anything in prepared class

thanks
David
WithOUT driver.
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post #58 of 363 (permalink) Old March 22nd, 2009, 07:28
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My next step is to get rid of my sway bars and use stiffer spring rates as Steve recommended. What shops carry the springs I'll need and are easy to deal with?
David
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post #59 of 363 (permalink) Old March 22nd, 2009, 20:25
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Hi David,

Welcome to DP and the forum. Glad you found the thread useful.

I run 20" wheels as they provide three primary benefits; 1. Fitted with 20x9x13 slicks, the car can be made about as low as practical without major re-engineering to the chassis. 2. They provide more favorable gearing than the 15" wheels. 3. They have lower intertia than the 15s.

I buy Eibach springs from Ground Control. And I have used used only Eibachs for the last 15 years.

Edit: I added a couple of pics to show how low my car is. I couldn't get there with 15s.





-Steve

Last edited by XHead; March 23rd, 2009 at 09:55.
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post #60 of 363 (permalink) Old March 23rd, 2009, 02:51
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Steve-o, where are you buying your slicks?
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