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 Post subject: snap oversteer and
PostPosted: June 18, 2016, 7:27 am 
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Joined: January 25, 2016, 6:13 pm
Posts: 38
so I want to build a car that is somewhat like a lancia rally 037, and I want to use a honda b16 with a rotex centripetal supercharger, How does one counter snap over steer in a car with a mid mounted transverse engine?


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 Post subject: Re: snap oversteer and
PostPosted: June 18, 2016, 7:57 am 
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Joined: January 1, 2012, 12:44 pm
Posts: 240
Location: Boise, Idaho
A little rear toe-in, sticky tires and lots of aero downforce. Take a look at the Loti that autocross in SCCA XP.


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 Post subject: Re: snap oversteer and
PostPosted: June 18, 2016, 11:07 am 
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Joined: January 25, 2016, 6:13 pm
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thats a pretty elise, how much downforce would be on a car like that? Ive never seen autocross break 100, I was under the impresion that you wouldnt make enough to matter


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 Post subject: Re: snap oversteer and
PostPosted: June 18, 2016, 11:41 am 
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Joined: January 1, 2012, 12:44 pm
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Location: Boise, Idaho
I 'll ask the owner if he has that info at our next event (mid-July). I do know that the double and triple element wings can be designed for noticeable downforce (100+ lbs) at speeds above 50 mph. (note: these are not PEP Boys variety wings) I also know that before the owner added the splitter/wing combo, he'd loop it at least once every event because he's a 10/10ths driver (ok, sometimes 11/10ths). Which brings up the obligatory disclaimer that, I'm assuming your question was about driving your build at 10/10ths in closed course activities, and for street driving, the solution is the 5/10ths approach.

Ron


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 Post subject: Re: snap oversteer and
PostPosted: June 18, 2016, 12:53 pm 
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Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
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Location: SoCal
You're starting with the conclusion as a given; build the car and toss it about at an autocross, then decide. What's really hard to learn is to keep your foot down when it starts to go, as lifting off only makes it worse.

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 Post subject: Re: snap oversteer and
PostPosted: June 18, 2016, 1:53 pm 
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Joined: February 8, 2014, 10:47 pm
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Location: Cornholio OR "Where the magic happens"
That is what I was going to say.

Is this something you are experiencing or read about on the internet?

Different track layouts, different track surfaces, tire pressure, tire compounds, temperature of the air, temperature of the track, shocks springs, sway bar settings, wheel offsets, roll centers, all play into a cars handling.

Generally in my experience snap oversteer occurs on a car that is setup too tight. If a car is screwed into the track when it comes loose it will not give any warning and be difficult to control when it does (hence the "snap" label). The setup needs to be adjusted to loosen the car up a bit so it gives the driver some feedback before coming unscrewed.

Another adjustment for snap oversteer is the nut behind the wheel. Perhaps the driver needs to adjust the apex to make the car happier.

Some track layouts favor a front wheel drive car, what are you going to do then?

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 Post subject: Re: snap oversteer and
PostPosted: June 18, 2016, 4:18 pm 
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Location: Fort Worth, Texas
Also snap oversteer isn't a given in a mid/rear engined Locost or any other car. It all goes back to set up.

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 Post subject: Re: snap oversteer and
PostPosted: June 18, 2016, 5:37 pm 
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Joined: August 19, 2014, 5:17 pm
Posts: 685
Location: England
jwestie15 wrote:
so I want to build a car that is somewhat like a lancia rally 037, and I want to use a honda b16 with a rotex centripetal supercharger, How does one counter snap over steer in a car with a mid mounted transverse engine?


Build and tune in some understeer thats effective before the dreaded snap oversteer. Its what all car makers do :)

Bob

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 Post subject: Re: snap oversteer and
PostPosted: June 19, 2016, 11:48 am 
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Joined: December 7, 2012, 8:28 am
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Location: Sarasota
Snap oversteer is usually caused by breaking hard and then attempting to turn too quickly. When you break the rear gets light and you could possibly lock the rear tires (or not). The grip on the rear tires is minimal due to little load however with most of the mass in the rear car, it then tries to overtake the front when the car attempts to turn. The easiest solution is to brake in a straight line.

A little bit of snap oversteer is desirable (for some) in an autocross car and I will regularly use the brakes to get the car to rotate quicker by getting loose, with practice it can be a lot of fun and a real crowd pleaser. To control it you brake and turn to get the rear end loose as it starts to rotate you accelerate. The weight then transfers to the rear and the rear grips. With a good setup and great timing this allows you to corner very quickly and accelerate hard out of the corner.

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 Post subject: Re: snap oversteer and
PostPosted: June 20, 2016, 2:55 am 
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Joined: January 25, 2016, 6:13 pm
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random thought I want to use a honda d16 (305 pounds!) for my engine mainly due to them being the lowest weight motor I can find that has a very sizable aftermarket how much would unequal length halfshafts in the rear be okay?


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 Post subject: Re: snap oversteer and
PostPosted: June 20, 2016, 8:38 am 
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Joined: April 23, 2006, 8:26 pm
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Location: SoCal
You'll be fine.

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Midlana book: Build this mid-engine Locost!, http://www.midlana.com/
Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


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 Post subject: Re: snap oversteer and
PostPosted: June 20, 2016, 8:11 pm 
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Joined: January 25, 2016, 6:13 pm
Posts: 38
okay so here is my concept 1.6 liter intercooled turbocharged honda powered dirt road crusher, 4 wheel McPherson struts(blasphemy I know but they can be made more durable, and more importantly lighter than dual wishbone) all with some GPR skin. I'm almost to a point where I can afford to do it financially as well as time wise. Im inspired by the toyota MR2 222d, the group S car that never was, the lancia 037 rallye, the mistrale open wheel Vtec build, and the Mcrae R4.


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