MKII CFD Aerodynamics Analysis - Page 2 - MR2 Owners Club Message Board
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post #21 of 345 (permalink) Old January 9th, 2011, 15:25 Thread Starter
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Here I added a slightly lower front lip and a longer flat front under panel. This is very similar to my current setup with the Holy front lip and my aluminum panels.

This configuration produced 45 lb of lift (a 2 lb reduction vs the 93 lip), and a drag coefficient of .315





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post #22 of 345 (permalink) Old January 9th, 2011, 15:57 Thread Starter
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Here is a quick and dirty model of a border style hood, with the radiator standing up straight instead of angled as in the other models. Its not exactly accurate, but like I said before, I am mostly looking for proof of concept results.



Lift was reduced by only 3 lb vs the previous configuration, to 42 lb, and the drag coefficient was .301.





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post #23 of 345 (permalink) Old January 9th, 2011, 16:05 Thread Starter
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Here I took the previous configuration and closed off the underbody behind the radiator, so all air from the radiator must go through the hood vents.

Lift reduced by quite a bit in this case about 9 lb down to 33 lb, and drag coefficient increased a bit to .345.





One thing I noticed in particular here with the new radiator model is that there is very little pressure drop across the radiator, compared to the versions where the bottom is vented. I think this is indicating that the border hood may not be able to vent enough air to generate a sufficient low pressure zone behind the radiator, and that radiator air flow and therefore cooling my suffer in this configuration.


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post #24 of 345 (permalink) Old January 9th, 2011, 16:28
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The bulkhead behind the radiator is vertical, it does not slope back at the bottom.
There are also the two fans that cover most of the rear of the radiator to within a few inches of the bulkhead. The air flow is far worse than your model but this is still the best thing I have seen, please keep the good work up.

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post #25 of 345 (permalink) Old January 9th, 2011, 16:35 Thread Starter
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Quote:
Originally Posted by bobhatton
The bulkhead behind the radiator is vertical, it does not slope back at the bottom.
There are also the two fans that cover most of the rear of the radiator to within a few inches of the bulkhead. The air flow is far worse than your model but this is still the best thing I have seen, please keep the good work up.

Bob
From what I remember of the last time I was under there, there is a slight slope to the bulkhead (you can even see this looking at it in the frunk). The lower flatter slope is definitely there, it is formed by the plastic under tray that covers the steering rack.

Good point about the fans, although I only have on in my car at this point.
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post #26 of 345 (permalink) Old January 9th, 2011, 16:40
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I have the front end off one car at the moment so I will have a look to see if I can see the slope, if it is there, its very small. I will take some phots if I can.

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post #27 of 345 (permalink) Old January 9th, 2011, 16:53
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square off the rear.
See how the air flow curves around the lights? That is really bad. You want the flow separating from the body there, and a squared off rear end will stop there.
The Prius and other new cars have that design now. NASCAR even does it on their cars.

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post #28 of 345 (permalink) Old January 9th, 2011, 17:02
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see how the Prius rear of the quarter panel is squared off?


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post #29 of 345 (permalink) Old January 11th, 2011, 17:32
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Quote:
Originally Posted by Bill Strong
[img]square off the rear.
See how the air flow curves around the lights? That is really bad. You want the flow separating from the body there, and a squared off rear end will stop there.
The Prius and other new cars have that design now. NASCAR even does it on their cars.
reminds me of corvettes, they also have a aggressively squared off back end and are tested to considerably higher speeds than any prius.

Would this explain the tiny lip that comes out off of the side of the rear blinkers? The part on the side that you have to pop off to remove the tail lights. Its small but I wonder if thats the reason for the way they are shaped that way.
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post #30 of 345 (permalink) Old January 11th, 2011, 18:04
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the momo corse jgtc mr2 has add on's that square the rear more on top of the widebody

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post #31 of 345 (permalink) Old January 18th, 2011, 02:10
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Can you run a test of a stock bodied MK2 with under panels covering the entire underside of the engine bay? I'd like to see if it would improve things a bit by relying solely on the side intakes.
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post #32 of 345 (permalink) Old January 18th, 2011, 08:19
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Hey Alex-

Could you run some results making a plate that would secure to the back of the bumper entry hole and make a more ramp like path for the air flow through the hood



And also run it where you would actually mod the front firewall and pull it inwards towards the cabin and make the exit of airflow higher up the hood towards the windshield



Thanks!
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post #33 of 345 (permalink) Old January 19th, 2011, 00:46 Thread Starter
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I will definetly try all of these. The full underbody panel is something I am interested in as well, although probably not something I would ever do since its not legal for SSM (autocross).

The large hood vent I was planning on trying just out of curiousity. The deflector plate behind the radiator I wouldn't expect to do much, as the high pressure zone probably tends to accomplish about the same thing with just air, but I will give it a shot.

I will be working on this some more next week when I get home from California.


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post #34 of 345 (permalink) Old January 19th, 2011, 00:56
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very interesting that you are doing this...Tonite I had an idea of installing my heat exchanger for my a2w intercooler under a hood scoop for effective cooling. You have enlightened me to wonder about the flow (mk1.5) would the air go through the hood scoop into the frunk? your info shows into going through the radiator, into the frunk, and out the hood scoop if the lower area under the radiator "wall" is blocked off low. I am guessing this would mean the hood scoop would open towards the windshield rather than the front...hmmm...would this help keep the car on the ground effectively at track speeds? I am very new to this, but you got me wondering some interesting things...subscribed...
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post #35 of 345 (permalink) Old January 20th, 2011, 12:05
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Quote:
Originally Posted by Alex W
I will definetly try all of these. The full underbody panel is something I am interested in as well, although probably not something I would ever do since its not legal for SSM (autocross).

The large hood vent I was planning on trying just out of curiousity. The deflector plate behind the radiator I wouldn't expect to do much, as the high pressure zone probably tends to accomplish about the same thing with just air, but I will give it a shot.

I will be working on this some more next week when I get home from California.
didnt know under body panels were a no go for ssm. thats good to know
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post #36 of 345 (permalink) Old January 20th, 2011, 13:47
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didnt know under body panels were a no go for ssm. thats good to know
Honestly, if you aren't taking a top 3 finish no one is going to protest you. I ran my car in SSM for a year illegally, wanna know what was illegal? No shift boot. Don't have your BGB on you? I can DQ you on the spot. Ironically enough I also have a custom made front underbody panel so I guess thats another notch against me. No one protests at a local level unless it is blatant like running A6s on a ST class or a swapped car in E stock, etc. Your region may be different however, just my experience. Don't let the rules stop you from doing anything unless your car is purpose built autox car focused solely on winning Tours/Nats than obviously you should follow the rules but the majority autox for fun.

Getting back on topic, it looks like there is not alot of airflow into the engine bay from underneath the car. I'd love to see what a flat bottom under the rear of the car covering the engine/crossmember to the back of the car would do but based on the diagrams it wouldn't do very much.

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post #37 of 345 (permalink) Old January 20th, 2011, 17:53
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post #38 of 345 (permalink) Old January 20th, 2011, 23:50 Thread Starter
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Quote:
Originally Posted by Levi
Honestly, if you aren't taking a top 3 finish no one is going to protest you. I ran my car in SSM for a year illegally, wanna know what was illegal? No shift boot. Don't have your BGB on you? I can DQ you on the spot. Ironically enough I also have a custom made front underbody panel so I guess thats another notch against me. No one protests at a local level unless it is blatant like running A6s on a ST class or a swapped car in E stock, etc. Your region may be different however, just my experience. Don't let the rules stop you from doing anything unless your car is purpose built autox car focused solely on winning Tours/Nats than obviously you should follow the rules but the majority autox for fun.

Getting back on topic, it looks like there is not alot of airflow into the engine bay from underneath the car. I'd love to see what a flat bottom under the rear of the car covering the engine/crossmember to the back of the car would do but based on the diagrams it wouldn't do very much.
Actually front under panel / splitter is legal as long as it does not extend rearward past the center line of the front wheels. You are probably OK in that respect.

Regarding the rules, I agree, nobody is likely to protest you, but I do try to keep my car legal anyway.

I think closing off the rear might be quite effective based on the way the low velocity region grows at the rear starting right at the engine bay opening. If that could be close up and then finished with a diffuser at the rear I think it would be pretty good.

One thing I found quite interesting is how the air flow off the roof runs basically straight into the stock spoiler. The velocity is down a bit at the level of the stock spoiler, but it does appear to be getting plenty of airflow still, so it should be doing something.
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post #39 of 345 (permalink) Old January 21st, 2011, 01:39
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Something I noticed when looking through is that the plastic under body scoop isn't incorporated into the models. The one for the engine bay. I know engine bay air flow has been a hot topic for some and I find it weird that nobody remembers theres is an air scoop under there that feeds into the engine bay.
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post #40 of 345 (permalink) Old January 21st, 2011, 01:46
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Originally Posted by Caprandom
Something I noticed when looking through is that the plastic under body scoop isn't incorporated into the models. The one for the engine bay. I know engine bay air flow has been a hot topic for some and I find it weird that nobody remembers theres is an air scoop under there that feeds into the engine bay.
Well for one, I am convinced most mr2s have that removed, secondly it really isn't a "scoop" its just a shield to prevent dirt/rust/debris from getting to the all the pipes underneath the car. It also isn't low enough to be able to catch any air or do anything really and in relation to how much of the engine bay is exposed it isn't anything significant.
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