240 flat undertray examples - Page 2

The Full Banana · 02-01-2021, 11:50 PM

Quote:

Originally Posted by Jack

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?

redblockpowered · 02-02-2021, 01:08 AM

I interpreted it as earlier car designs in general, not specifically early 240s.

Stiggy Pop · 02-02-2021, 10:10 AM

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.

redblockpowered · 02-02-2021, 03:49 PM

Never too early to start on some sweet 242 CFD modeling for your aero package.

LC4CARL · 02-02-2021, 11:08 PM

Chicks dig down-force.

Jack · 02-02-2021, 11:51 PM

Quote:

Originally Posted by redblockpowered

I interpreted it as earlier car designs in general, not specifically early 240s.

This

Jack · 02-02-2021, 11:52 PM

Quote:

Originally Posted by LC4CARL

[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

Jack · 02-02-2021, 11:53 PM

Quote:

Originally Posted by Stiggy Pop

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

PaddyGarcia · 02-03-2021, 11:44 AM

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

Stiggy Pop · 02-03-2021, 11:56 AM

Quote:

Originally Posted by PaddyGarcia

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.

PaddyGarcia · 02-03-2021, 12:49 PM

No need to fiddle, relocate the gas tank and open the trunk up as the Mother of All Diffusers :-)

VB242 · 02-03-2021, 01:25 PM

Quote:

Originally Posted by Stiggy Pop

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.

Jack · 02-03-2021, 01:29 PM

3 inch won’t fit over the axle.

Stiggy Pop · 02-03-2021, 01:32 PM

Quote:

Originally Posted by VB242

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

Jack · 02-03-2021, 01:37 PM

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

Stiggy Pop · 02-03-2021, 01:39 PM

that felt like a risky click on the work computer

Jack · 02-03-2021, 01:52 PM

Quote:

Originally Posted by Stiggy Pop

that felt like a risky click on the work computer

PM

VB242 · 02-03-2021, 01:54 PM

Quote:

Originally Posted by Jack

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

Jack · 02-03-2021, 01:57 PM

Quote:

Originally Posted by VB242

3" x2" x 2" wye not reducing at all

Wut

Edit Ahh I see

Harlard · 02-03-2021, 02:06 PM

Mike, going over axle will make your life a lot easier.

The Full Banana · 02-03-2021, 02:08 PM

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.

Stiggy Pop · 02-03-2021, 02:12 PM

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

Harlard · 02-03-2021, 02:21 PM

If you plan on doing a true front mount intercooler, I'm interested in that too, lol

JW240 · 02-03-2021, 02:24 PM

Quote:

Originally Posted by The Full Banana

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.

Harlard · 02-03-2021, 02:48 PM

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.

02-02-2021, 01:08 AM	#27
redblockpowered cone dodging dilettante Join Date: May 2015 Location: In bed, probably	I interpreted it as earlier car designs in general, not specifically early 240s. __________________ 1993 944 B230FT/M90 thread here: http://forums.turbobricks.com/showthread.php?t=345277 2x 1991 245 B230F/M47 (LeMons car, street car) I sell chips for LH 2.4!

02-02-2021, 10:10 AM	#28
Stiggy Pop Board Member Join Date: Feb 2011 Location: Granville, MA	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. __________________ '79 242 943 pickup

02-02-2021, 11:08 PM	#30
LC4CARL Aero challenged Join Date: Sep 2008 Location: Vancouver, WA	Chicks dig down-force. __________________ @PDXvolvo on IG

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02-02-2021, 03:49 PM	#29
redblockpowered cone dodging dilettante Join Date: May 2015 Location: In bed, probably	Never too early to start on some sweet 242 CFD modeling for your aero package.

02-03-2021, 11:44 AM	#34
PaddyGarcia Board Member Join Date: Jul 2020 Location: NW Virginia	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

02-03-2021, 12:49 PM	#36
PaddyGarcia Board Member Join Date: Jul 2020 Location: NW Virginia	No need to fiddle, relocate the gas tank and open the trunk up as the Mother of All Diffusers :-)

02-03-2021, 01:29 PM	#38
Jack junkman Join Date: Jul 2011 Location: The Ass Cheek Of History	3 inch won’t fit over the axle.

02-03-2021, 01:37 PM	#40
Jack junkman Join Date: Jul 2011 Location: The Ass Cheek Of History	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

02-03-2021, 01:39 PM	#41
Stiggy Pop Board Member Join Date: Feb 2011 Location: Granville, MA	that felt like a risky click on the work computer

02-03-2021, 02:08 PM	#46
The Full Banana not yet good enough Join Date: Apr 2007 Location: Jackson, WI	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.

02-03-2021, 02:12 PM	#47
Stiggy Pop Board Member Join Date: Feb 2011 Location: Granville, MA	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

02-03-2021, 02:21 PM	#48
Harlard Hurlurd?Harland?Bueller? Join Date: May 2007 Location: PDX	If you plan on doing a true front mount intercooler, I'm interested in that too, lol

02-03-2021, 02:48 PM	#50
Harlard Hurlurd?Harland?Bueller? Join Date: May 2007 Location: PDX	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.