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Old 02-01-2021, 11:50 PM   #26
The Full Banana
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Originally Posted by Jack View Post
Look at hypermileing 240s on google. There’s been a few.

Aero stuff makes a difference above 30 mph

the way the panels fit makes a huge difference. Your biggest gains will come from under the engine and smoothing out area behind the axle
Also the less holes in front of car the better ... ie gaps between headlights and turn signals (Look at a 240 vs 850 and then look up their drag coefficient all little things add up)

When you start modifying for aero your car will loose a lot of wind noise
One of the worse things on early cars are the roof drains.

Here’s some simple equations for aero stuff. Found this at my old school F1 engine builders shop

https://imgur.com/a/vwO72Yy?s=sms
What’s different about the drip rails on early cars? Difference in the trim?
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Old 02-02-2021, 01:08 AM   #27
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I interpreted it as earlier car designs in general, not specifically early 240s.
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Old 02-02-2021, 10:10 AM   #28
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I know drip rails are great for making a bunch of wind noise on the highway..

Took a quick look under the car in storage and the exhaust/muffler is the lowest point in the rear. Might be able to pass under the axle, but not sure if its worth the effort.

Probably something I'll get started in March, unfortunately.
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Old 02-02-2021, 03:49 PM   #29
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Never too early to start on some sweet 242 CFD modeling for your aero package.
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Old 02-02-2021, 11:08 PM   #30
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Chicks dig down-force.
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Old 02-02-2021, 11:51 PM   #31
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Originally Posted by redblockpowered View Post
I interpreted it as earlier car designs in general, not specifically early 240s.
This
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Old 02-02-2021, 11:52 PM   #32
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Originally Posted by LC4CARL View Post
[IMG]

Chicks dig down-force.
Did you just discover bing image search ?

F40 has a drag coefficient of .34.

850r sedan is at .29 (93 sedan is .34 which shows how much a little smoothing out with the right spoilers can do)

75 244 is .47
75 245 is .45

Last edited by Jack; 02-03-2021 at 12:02 AM..
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Old 02-02-2021, 11:53 PM   #33
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Originally Posted by Stiggy Pop View Post
I know drip rails are great for making a bunch of wind noise on the highway..

Took a quick look under the car in storage and the exhaust/muffler is the lowest point in the rear. Might be able to pass under the axle, but not sure if its worth the effort.

Probably something I'll get started in March, unfortunately.
Generally Wind noise = bad aero
Big reason why newer cars are so quiet (not counting the tire noise)


Interesting read by volvo https://www.mech.kth.se/courses/5C12...erg_2012_1.pdf

Last edited by Jack; 02-03-2021 at 12:04 AM..
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Old 02-03-2021, 11:44 AM   #34
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Good stuff there. I never realized how much benefit comes from lowering the car.

Stiggy Pop, do you have a rear spoiler? Assuming that the Group A cars were stable at speed, they could make a good pattern for a solution: smallish (for today) front lip and some rake to help keep air from going under the car, and a smallish (again, for today) rear spoiler to reduce lift at the back.

Some input here: https://scholarcommons.scu.edu/cgi/v...text=mech_mstr
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Old 02-03-2021, 11:56 AM   #35
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Originally Posted by PaddyGarcia View Post
Good stuff there. I never realized how much benefit comes from lowering the car.

Stiggy Pop, do you have a rear spoiler? Assuming that the Group A cars were stable at speed, they could make a good pattern for a solution: smallish (for today) front lip and some rake to help keep air from going under the car, and a smallish (again, for today) rear spoiler to reduce lift at the back.

Some input here: https://scholarcommons.scu.edu/cgi/v...text=mech_mstr
no spoiler, and unfortunately I'm unwilling to add one, or a splitter. Just not part of the car's aesthetic. I'll white knuckle it to 150 first

Looking at the bottom of the car I think the whole front 2/3 is going to be pretty straightforward. The exhaust/axle area will be fiddly.


Last edited by Stiggy Pop; 02-03-2021 at 12:54 PM..
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Old 02-03-2021, 12:49 PM   #36
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No need to fiddle, relocate the gas tank and open the trunk up as the Mother of All Diffusers :-)
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Old 02-03-2021, 01:25 PM   #37
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Originally Posted by Stiggy Pop View Post
no spoiler, and unfortunately I'm unwilling to add one, or a splitter. Just not part of the car's aesthetic. I'll white knuckle it to 150 first

Looking at the bottom of the car I think the whole front 2/3 is going to be pretty straightforward. The exhaust/axle area will be fiddly.

Interesting that you went under the axle with your exhaust, what size pipe? I was thinking about splitting it down from 3" to 2) 1.75 or 2" pipes to go over the axle.
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Old 02-03-2021, 01:29 PM   #38
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3 inch won’t fit over the axle.
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Old 02-03-2021, 01:32 PM   #39
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Interesting that you went under the axle with your exhaust, what size pipe? I was thinking about splitting it down from 3" to 2) 1.75 or 2" pipes to go over the axle.
it's 3". Not sure if it would work as well with a higher ride height, but with the short konis I can hang the axle at full droop and it doesn't interfere
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Old 02-03-2021, 01:37 PM   #40
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My 3 inch
https://i.imgur.com/aZeWk07.jpg?s=sms


If you’re going to reduce your exhaust size to go over the axle why even bother with the larger stuff
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Old 02-03-2021, 01:39 PM   #41
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that felt like a risky click on the work computer
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Old 02-03-2021, 01:52 PM   #42
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that felt like a risky click on the work computer
PM
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Old 02-03-2021, 01:54 PM   #43
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My 3 inch
https://i.imgur.com/aZeWk07.jpg?s=sms


If you’re going to reduce your exhaust size to go over the axle why even bother with the larger stuff
3" x2" x 2" wye not reducing at all

http://www.siliconeintakes.com/dsm-i...RoC4rQQAvD_BwE

Last edited by VB242; 02-03-2021 at 02:00 PM..
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Old 02-03-2021, 01:57 PM   #44
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3" x2" x 2" wye not reducing at all
Wut

Edit Ahh I see
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Old 02-03-2021, 02:06 PM   #45
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Mike, going over axle will make your life a lot easier.
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Old 02-03-2021, 02:08 PM   #46
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Time to tuck that exhaust up over the axle!

3" fits over axle, you just have to be careful. I just did it in my reasonably low 242 and so have quite a few others.



I could have tucked mine closer to the body for more clearance. I would just take your time to get it pretty close and you'll be fine.
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Old 02-03-2021, 02:12 PM   #47
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ehhh not sure if the juice is worth the squeeze on that one. I'd have to relocate the muffler, then I'm most of the way to building a new system from the DP back, and there's really no other driving forces so it's tacking a lot of cost and complexity onto a "for fun" project.

I'm slow rolling another project involving computer models, custom end tanks and welding so I want to keep this one simple-ish
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Old 02-03-2021, 02:21 PM   #48
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If you plan on doing a true front mount intercooler, I'm interested in that too, lol
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Old 02-03-2021, 02:24 PM   #49
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Time to tuck that exhaust up over the axle!

3" fits over axle, you just have to be careful. I just did it in my reasonably low 242 and so have quite a few others.

[img]https://i.imgur.com/s66xIjil.jpg[ /img]

I could have tucked mine closer to the body for more clearance. I would just take your time to get it pretty close and you'll be fine.
Yeah, the JT system I had (was great, the muffler before the axle was slanted upwards to the rear and was far from the lowest point under the car. Over axle, did not have clearance issues.
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Old 02-03-2021, 02:48 PM   #50
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The JT with 2 mufflers is what I have too. Very easy to fit. Wish it was 409 SS but for the convenience I can't complain. Center muffler mounts to seem to transmit a lot of vibration from the engine with stiff motor mounts. It's a bit loud at idle but mostly great for the price.
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