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blacky83
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Re:Front Air Diffusers - do they work? 2012/06/29 15:14:33 (permalink) ☄ Helpful
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Real world testing is always the best idea if you can do it. CFD is useless unless you can validate it against something accurate, and even wind tunnels aren't perfect unless you have a rolling road within it.
For measuring downforce, I've used linear potentiometers mounted on the shocks to measure the suspension travel. So go drive 100kmh with and without your aero, and you should have a difference. However that was with downforce of around 10-15% of the static weight, which you won't get close to on a road car, so dunno whether it would be accurate enough.
Alternatively you can use strain gauges/load cells on the mounts to directly measure how much force its pulling down with.
 
For drag, if you can log speed data (electric speedo, ABS sensor) then its really easy to measure with a coast down test. Again start at 100kmh, then just let the car drop speed on its own (in neutral). The drag force will be equivalent to your velocity^2, whilst rolling resistance is only equivalent to the velocity. Some quick maths will give you the drag coefficient, so you can test whether it changes much.
 
I believe EMS powered sell the flat underbody panels, but they're aluminium. Not the material I'd use.
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Re:Front Air Diffusers - do they work? 2012/06/29 22:31:20 (permalink) ☄ Helpful
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blacky83, i'm guessing you did mech engineering or aero at uni, and did formula sae?? Linear shock pots are awesome if you have them available to you, but can be very expensive. I use delco ride height sensors off holdens with hid's, with a small 3/16 link to the lower control arm. There isn't a lot wrong with using alloy for undertrays, it is a bit heavy, and it has to be braced, the thing that you need to keep in mind is whatever you use, it has to be rigid to ensure that the airflow stays attached to remain effective. Steep angles are to be avoided for this reason. Small diffusers in front of the front wheels can be quiet effective, with some small strakes mounted to them. When doing front splitters, you must keep in mind that the further they protrude, the more leverage they have. For the coast down test, you only need to coast down 10-15km/h to get enough data, and note that one you attempt the test above 150km/h, drivetrain drag increases exponentially. If your getting to the point of using shock pots and doing coast down and constand speed tests, you will need to invest in some form of weather station to help eliminate some variables of windspeed and direction, as piezo tubes are over the top for a road car. Also with an mr2, if you make a front splitter and extend it under the front between the wheels, make sure you don't seal it to the body too much, or if you do, consider how you are going to get the air out once it has past through the radiator.

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more to come......
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Tree
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Re:Front Air Diffusers - do they work? 2012/06/29 23:03:33 (permalink)
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I'd be interested in buying if you make it :)
My under panels aren't in the best shape anyways... 
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Re:Front Air Diffusers - do they work? 2012/06/29 23:11:20 (permalink)
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EssDub and I were interested in getting some new front panels made up too (maybe CF?). The two small ones underneath the radiator.

1990 SW20 GT 3S-GTE Targa
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blacky83
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Re:Front Air Diffusers - do they work? 2012/07/02 01:22:25 (permalink)
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Yep, I was involved in the Uni of Adelaide FSAE team for a bit. Was a fantastic experience, and it was really nice having so many resources to work with. There would be race teams with less access to some of the things we were using, only most of it we had to teach ourselves how to use.
Linear pots are pretty expensive, unless you could borrow a set. Alternatively it should be possible to rig a rotary pot to measure linear displacement, though it would need to be calibrated. I'm not familiar with the Delco sensors, how do they function?
 
Aluminium floor wouldn't be as heavy as I originally thought, but I still think for something that is only really supporting itself, you can get away with something a lot lighter. Fibreglass or carbon fibre are pretty good if you are able to work with them. Otherwise you can get sheets of aluminium/foam sandwich board pre made, or even corrugated plastic lke Coroplast. As for the radiator, ideally I'd like to use a vented bonnet and route the air upwards (this can also help with downforce, marginally) but I think this requires cutting of the body.
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Re:Front Air Diffusers - do they work? 2013/03/22 01:20:49 (permalink)
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Anyone still looking for front splitters?
 
https://www.importmonster...title=Front%20diffuser

http://www.holycustomcreations.com/catalog/index.php?main_page=product_info&cPath=13&products_id=30
 
The Holy front splitter looks like it's made for some serious downforce!
Shipping might be the killer here tho
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Re:Front Air Diffusers - do they work? 2013/03/22 21:20:45 (permalink)
+1 (1)
I very envious of all you guys who managed to make it to uni. Well done to you all.
My experience/knowledge is limited but I do have a little that I would like to contribute to this thread.
First: Rear wing. I did a test when towing my car to various tracks. First without the wing, then with a high downforce setting then one with a lower downforce setting. With no wing the car was not stable at all . Any wind of any type or simply cruising, the car and trailer was unstable. When driving with the higher downforce setting, I experienced some pitching at the pivot of the trailer and van due to the rear lifting. It also caused a heap of drag which was very noticable when towing. The last test was with the rear wing set to a less agressive setting where abiltiy to tow effectively was very noticable with the trailer far more balanced to the trailer.
So the wing does make a difference from 60km/h up to 110km/h.
The car is also fitted with a full undertray from the front splitter which protudes 50mm forward of the front bumper.
It is alloy with a alloy subframe bolted and pop riveted to the chassis. Its too heavy, almost 30kg which was very noticable in the track. A lighter unit will be made now we have a template. there was a difference in the way the car felt on the track but unfortunately we could not use all the power available so we could not get a clear picture of its full potential. Even so, we could carry a lot of corner speed as this didnt require a lot of throttle inputs. Out corner speed was just about as quick as the division one cars through the quicker corners on the track without any movement of the rear of the car.
We added ducting to the undertray at the engine bay which provided huge gains in engine temp management.
I believe the ducting in the frunk of the car helps remove a fair amount of air from under the car.
The canards help to clear the air exiting the side of the car. I dont run these, but will test once Im tuned into the current set up. They may not provide much downforce, but they may help in other aspects of performance.
 
I dont think the cars need too much rear down force but more front and a diffuser to reduce the gap between the front of the car working and the rear
I have added a video showing the car at 140kmh in wet conditions with the hope of seeing the effects of the aero fitted to my car. I believe the spray helps to see whats going on, but you be the judge. A important point being the wing was set up for high downforce and the pitch was 10mm higher at the front of the car. The driver was complaining of aquaplaning and excessive wheelspin when it would boost spike but thats another tail..
 
http://youtu.be/eCZGJ6jE-qs
 
 
 
 
#22
Tree
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Re:Front Air Diffusers - do they work? 2013/03/23 00:57:16 (permalink)
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Steve my man, don't be envious of uni. I'm in uni and uni sucks (except the chicks!!!). There I said it lol (but seriously, so many things>>>homework). I wanna be doing what you do and race cars for a living. Now that would be worthy of envy :)
Thanks so much for sharing that knowledge that came from your time and efforts.
The wing needs to be higher than the tallest part of the car to be effective yeh? With so much rear grip it makes sense to have more grip up front. Too bad my car won't reach the "effective" speed haha. Once I get new sussy sorted out I'll see how that goes and see if I need the front splitters at all. But seeing as my front under tray ripped off on the way to 2013 MR2 Track day, I do need a suitable replacement...at least for peace of mind...
I suspect the flat under body would make the car feel...hmm smoother or more stable high speeds?
Cool vid dude, it looks really really wet! (what she said) can defs see the water spray up
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Re:Front Air Diffusers - do they work? 2013/03/23 19:24:33 (permalink)
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its not really the wing has to be higher than the highest part of the car - the cleaner the airflow the wing receives, the more effective it will be. the easiest way is just sticking it up in clean air, but it also makes more drag that way.

the easiest way to work out how much aero you need, or how you need to go about it is how much drag you can afford. big wings, big dive planes and really outlandish aero are all good and well, but if you cant afford the drag penalty it is useless. keeping drag down ie. cleaning up panel gaps or taping them up, smaller mirrors, removing wipers at track day, wheels being inside arches, excess weight removed, smooth, sealed arches, can be just as effective.

'88 MR2 4AGTE W/ EFR6258

224.6KW @ 20PSI

more to come......
#24
Tree
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Re:Front Air Diffusers - do they work? 2013/03/24 03:45:07 (permalink)
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Cool guess I'll start with those annoying panel gaps...
Thanks for the knowledge and tips MCT!
post edited by Tree - 2013/03/24 23:20:42
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Re:Front Air Diffusers - do they work? 2013/03/24 11:36:23 (permalink)
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Tree
Steve my man, don't be envious of uni. I'm in uni and uni sucks (except the chicks!!!). There I said it lol (but seriously, so many things>>>homework). I wanna be doing what you do and race cars for a living. Now that would be worthy of envy :)
Thanks so much for sharing that knowledge that came from your time and efforts.
The wing needs to be higher than the tallest part of the car to be effective yeh? With so much rear grip it makes sense to have more grip up front. Too bad my car won't reach the "effective" speed haha. Once I get new sussy sorted out I'll see how that goes and see if I need the front splitters at all. But seeing as my front under tray ripped off on the way to 2013 MR2 Track day, I do need a suitable replacement...at least for peace of mind...
I suspect the flat under body would make the car feel...hmm smoother or more stable high speeds?
Cool vid dude, it looks really really wet! (what she said) can defs see the water spray up


Thanks Tree but sadly, I dont race cars for a living. It's a hobby,a passion but Im in the same boat as you my friend. Looks like Uni has its perks but no matter what you do, there is always some form of homework.
As for the rear wing, mine is not as high as the boot but it does work and you can adjust to maximise what it has to offer. We cannot get massive downforce but we can get enough to create a balance in the car. I think the standard wing must work to the limits of our car and the power they produce. It would also be designed not to create a lot of drag for fuel and top end speed. A splitter would help but you need one that is similar to the attached photo in the earlier post. Im a big believer in the 7 degree of rake and veins which push the air out the side of the car. From what I can gather, this helps with cornering, reduces understeer in quick corners like turn one at PI and EC or the sweeper at Winton which is 160kmh corner. 
A undertray is a good idea. We were discussing the undertray at Wakefield yesterday when Ian asked if the undertray did weigh 30+kg. It should only weigh 20kg in total but it felt a lot more on the track. It felt heavy but quite stable in the corners so its possible that I was experiencing the effects of the undertray 'sucking' the car to the track. Im not saying this is it, but its possible this was the case.
If you are using the car at the track more often, you can always get consistancy with your currrent set up and driving skills then when your ready, return to the track with the undertray and wing not fitted then do some back to back testing.
Go out for two sessions and get your 'eye in', taking lap times and video. After the second session, fit the front diffuser then go for a session. Take some notes, check the tyre temps/pressures in comparison to the earlier sessions. Then add the rear wing or adjust your existing unit then test again. Take notes,temps and pressures, then remove the parts, reset the wing then go out again. Then take notes,pressure and temps. You should then have enough info to come up with a result. If you can gain some support for your experiment you will have a great day out with some like minded people and have some feed back for the rest of the community.
As for the water spray on my car, I was looking to see if there was difference to a MR2 without a undertray and its flow in comparison. It would be great to get some footage of a std undertray and draw a back to back comparison. Is it raining down there??
 
 
 
#26
Tree
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Re:Front Air Diffusers - do they work? 2013/03/24 23:18:50 (permalink)
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Well I really hope one day our passions come to fruition. Once I'm done with this uni thing I'll definitely work harder to get there!
You take the sweeper at 160km/h!!? I think on semi's (A048) I reached 110km/h but it was high traffic (fun day). On road tyres (RE002) about 105km/h, a bit more with better driving/lines.
Definitely a good idea to work on driving first and foremost and the rest can come later. Even so stock suspension is just not good enough! Yeh I guess I should learn taking notes once I get "good enough" and have my Koni's and semi's back on. Getting quite serious for a road car tho hehe.
I was at Winton last Friday and the weather was great, a bit cloudy so it wasn't boiling hot in the car and the track was 99.7% dry. There were 1-2 heavy rain days but mostly sunny down here.
7 deg rake means the car is dipped lower at the front isn't it? Sorry I'm still such a noob hehe
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Re:Front Air Diffusers - do they work? 2013/03/25 10:28:35 (permalink)
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I was at 7200rpm in third, grabbing fourth on entry to the sweeper. The key is the corner before.
Do you have times on your trackday? Are you looking at a front diffuser to improve front grip on entry?
 
The 7 degrees rake is from the front of the bumper to the lower control arm pivot points not the whole car. I think  one degree is 10mm per 1000mm which would make 300mm overall. That will not work.
The same is done with the rear diffuser. 7 degree from the subframe back as far as you can(rear bumper).
Im not 100% if this is the right degree, but it has appeared from time to time.
The Pearl has about 15mm from front of car to the rear. Im not sure the reason for this but its could be a old way of helping with getting air out from under the car(slightly) and/or improving stability under braking (as we were told to do at the Wakefield 300). The Pearl is quick and will be quicker if it returns for the MTC 2014.
 
#28
Tree
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Re:Front Air Diffusers - do they work? 2013/03/25 17:04:40 (permalink)
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At my speed I don't think it will make too much difference, maybe in the S bend after the longest straight.The front diffuser I'm hoping to replace the under body panels that go underneath the radiator. I know Travis said it shouldn't make much difference, but it looks like it might. With testing we'll know.
 
I have about 40 mins of racing footage that I'm still editing. My best I think is about 1:53 with those road tyres and stock sussy. On semi's it's about 1:52 high traffic. I think with good driving, stiffer sussy and semi's back on the car is good for under 1:45. Might seem optimistic but I think it's fairly accurate.
I'll link the videos to my sig when it's finished.
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Re:Front Air Diffusers - do they work? 2013/03/25 20:33:57 (permalink)
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A 1.53 is pretty good with your set up and a 1.50 should be the aim with the semi's. After doing a calulation based on your times at Wakefield against mine I came up with a 1.59 lap which means you are already way ahead of your first trackday experience.
I think I did a 1.37 consistantly so you could get to a 1.45 but will require a bit of work.
The calculation:
divided your time into my time (76sec/68sec)=1.117
multiplied your ratio by my time at winton (1.117x107sec)=119sec/1.49min
I think this is correct but please correct me if Im wrong as it would be great to get this right.
You may notice difference in the quicker corners with the front diffuser but just go for it and let us all know. Thats what its all about Tri.
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