[Mk2] [Generic] Reducing front end lift and generally improving front end grip

[kayjay0_7]

Does anyone know what kind of thickness of aluminium sheet I'd need to use for the front undertray? Or if there's a better material to use?

Metal would be good as I'd like to incorporate speed flaps into the single sheet.

Gazrev1tubby has made a fibreglass under tray for his rev6 front bumper


I'm surprised that he hasn't posted in the mk2 modifications section

Hopefully when the weather improves , I'll lay up a couple of layers of fibreglass and do the same

I've seen that the mr2 mk3 and Lexus is200 have a different style of speed flap so will be easier to fix this to the under tray

[Magic Beans]

Wouldn't there be issues with flex and a risk of it cracking?

I'm looking at taking the bumper off and making a template in the next few days. That way I can make them out of whatever material seems best at the time. Might even be a market for them

[Magic Beans]

Ordered the aly sheeting for the undertray, I opted for 2mm, to reduce flex. The sheet is being partially cut to shape before shipping, so it will be the right width and length, leaving just the contours to cut into it once it arrives

The edge which meets the tyres is intentionally being left longer, as I plan to create a 50mm (ish) flaps which will be folded down to act as a speed flap. However I'm unclear as to what angles it should be at and what the aerodynamic principles/aims are for these flaps

Would the ideal configuration be the flap running perfectly vertical and running perfectly in line with the outer edge of the tyre, or would toeing it in or out have some benefit? I'm not sure if their purpose is simply to create a vertical surface for the air to hit, or whether they channel the air in a specific direction (out of the arches etc)?

[Magic Beans]

I thought I'd update this as I've not finished and installed the flat front bumper undertray, which incorporates speed flaps.





A full write-up of the build process (including the usual 1000000 photos ) can be found here, for anyone who's interested http://www.imoc.co.uk/forums/viewtopic. ... start=1500

The results so far are positive, with the car generally feeling much more planted at speed. I'm currently working on the custom arch liners at the moment, which should complete the package and hopefully amplify results and feel. That's the thinking/logic at least

Another aspect I'm conscious of is that these cars are quite poor in terms of weight distribution front to back, which certainly plays a part in that floaty feel under boost. I'm not sure how this can be addressed though. Is there anything which could be relocated towards the front without any significant compromise? Other than the passenger sitting in the frunk of course

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Great job Phil . Knew the speed flaps would work - have you seen http://ecomodder.com ? Specifically reference contoured tyre spats on this page http://ecomodder.com/forum/fuel-economy ... ations.php


Re. Weight redistribution, not much you can do unless you think outside totally outside the box and fit a remote (front mounted) turbo : you then lose weight of turbo and exhaust box and possibly other turbo ancillaries from rear (and naturally frunk space) .

Crazy I know but it's been done on front engined cars . Before anyone dismisses the possibility they may want to consult these guys on the whole scenario http://www.balancemotorsport.co.uk/prod ... bocharging

But then that's a whole new discussion, right?

[synXero]

Perhaps you could think less about front to rear weight distribution and try to power the centre of gravity more? That wouldn't do much for high speed floatiness but would be great through the corners. I don't know if the process would deny the results but I expect so.

[Magic Beans]

Great job Phil . Knew the speed flaps would work - have you seen http://ecomodder.com ? Specifically reference contoured tyre spats on this page http://ecomodder.com/forum/fuel-economy ... ations.php


Re. Weight redistribution, not much you can do unless you think outside totally outside the box and fit a remote (front mounted) turbo : you then lose weight of turbo and exhaust box and possibly other turbo ancillaries from rear (and naturally frunk space) .

Crazy I know but it's been done on front engined cars . Before anyone dismisses the possibility they may want to consult these guys on the whole scenario http://www.balancemotorsport.co.uk/prod ... bocharging

But then that's a whole new discussion, right?

Thanks for the links Adam, some food for thought I'm going to look into some of the other non-aero ideas and will create some new threads on them.

One question it's created is are the two side there for any purpose other than aesthetics? My thinking is if they were to be internally blocked and then uprights pieces being mounted at the sides of the main (central) opening, this would channel air cleanly through the rad(s) and underneath the car. It would also prevent air from flowing towards the arches, which we know is something which it's better to reduce/stop. The downside of blocking openings on other cars seems to be the risk of affecting cooling in front engined cars. This however isn't a risk for us and air would be allowed in, just in the way we choose.



I remember reading a thread on here about a guy who was looking at the front mounted turbo solution. It could work and be done but I fear at the detriment of space and practicality. I need to spend some time researching it all really, likely on the American forums, as people seem to like to push the boundaries over there, which I like

[Magic Beans]

Perhaps you could think less about front to rear weight distribution and try to power the centre of gravity more? That wouldn't do much for high speed floatiness but would be great through the corners. I don't know if the process would deny the results but I expect so.

These cars are pretty good in terms of having a low centre of gravity, due to things like the position of the fuel tank etc. Definitely something I'll be reading about though, there's definitely some good gains to be had with some adjustments.

[J-1]

On the subject of aerodynamics and such, I thought I'd ask this...

Does having a rear bumper on a MR2 cut, like the photo on the link bellow, make any difference due to the engine location? Or is this only beneficial to front engined cars?

http://lateralperformance.co.uk/images/ ... rborne.jpg

[synXero]

That bumper is cut to allow for the diffuser to continue up from the undertray fella. There is a very specific gradient that a diffuser should follow in order to perform optimally! Usually this means butchering your bumpers.

Patrick at Rogue wrote a great post about this once.

[andylaurence]

I don't see a diffuser on that Impreza, just a diff and an ARB. I suspect the rear bumper was catching air and acting like a parachute. Removing it has probably reduced drag. Fitting a diffuser would have been far more preferable as it would generate some downforce. Maybe the car wouldn't be several feet off the ground with a bit of downforce!

I've not seen this thread before, but it's an interesting one. What you're aiming for is an aero balance. By that, I mean the centre of pressure should be close to the centre of gravity. To explain further, if the car's got a 40/60 Front/Rear weight balance, then you really want a 40/60 balance of downforce (or lift). Often, people aim to get the aero balance slightly further rearwards as this helps induce a bit of understeer at speed, which is comforting!

There's loads of scope for improving the aero on an MR2, but it depends on what your objectives are as to the way forwards. I'm sure that a full flat floor with a small diffuser (8-10 degrees) at the rear will reduce drag and lift on an MR2.

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Agree with the flat floor throughout - perhaps we need to tackle both drag and lift using this approach too?

Why not divert airflow through two small rads evacuated into the front wheel wells, as per Ferrari F430? Speed flaps would lower pressure within the wheel wells further encouraging extraction.

Front splitter extending 3" or so would take care of downforce

As you've removed the front bumper Phil, what's the feasibility ?

[Magic Beans]

Agree with the flat floor throughout - perhaps we need to tackle both drag and lift using this approach too?

Why not divert airflow through two small rads evacuated into the front wheel wells, as per Ferrari F430? Speed flaps would lower pressure within the wheel wells further encouraging extraction.

Front splitter extending 3" or so would take care of downforce

As you've removed the front bumper Phil, what's the feasibility ?

It could be done, however it would require a fair amount of work to get the rads mounted correctly and be functional/efficient. I'm not sure if there's enough of a benefit, as the car was built around the rad being in the stock central location, whereas the F430 was built around it's own configuration.

If I were to do it again with a Border bumper I'd go with my idea to block off the two side vents on the bumper, as they were designed to vent the brakes on the Border racing car, as well as creating the shroud around the main opening. Speaking to others on the American forums, those who understand aero far better than I, they seem to agree that's the best approach. Although the ultimate would be to do it in conjunction with a proper Border bonnet and to angle the rad so airflow goes over the bonnet. The shroud would still work in that instance and I'd imagine the original Border car had one within the bumper. Without seeing it I guess we'll never know for sure.

[Peter Gidden]

As you've removed the front bumper Phil, what's the feasibility ?

He's have to ask the new owner first. Last post was 5 months ago.

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As you've removed the front bumper Phil, what's the feasibility ?

He's have to ask the new owner first. Last post was 5 months ago.

yes Peter I realize that, Phil happens to be a helpful sort of guy, as you see above.

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Agree with the flat floor throughout - perhaps we need to tackle both drag and lift using this approach too?

Why not divert airflow through two small rads evacuated into the front wheel wells, as per Ferrari F430? Speed flaps would lower pressure within the wheel wells further encouraging extraction.

Front splitter extending 3" or so would take care of downforce

As you've removed the front bumper Phil, what's the feasibility ?

It could be done, however it would require a fair amount of work to get the rads mounted correctly and be functional/efficient. I'm not sure if there's enough of a benefit, as the car was built around the rad being in the stock central location, whereas the F430 was built around it's own configuration.

If I were to do it again with a Border bumper I'd go with my idea to block off the two side vents on the bumper, as they were designed to vent the brakes on the Border racing car, as well as creating the shroud around the main opening. Speaking to others on the American forums, those who understand aero far better than I, they seem to agree that's the best approach. Although the ultimate would be to do it in conjunction with a proper Border bonnet and to angle the rad so airflow goes over the bonnet. The shroud would still work in that instance and I'd imagine the original Border car had one within the bumper. Without seeing it I guess we'll never know for sure.

Ok thanks Phil for replying, very good of you since you no longer have the Mule in your possession, I'd agree with you that the Border bumper would work quite well if someone wanted to go that route ( hopefully the vents would flow enough air )

Think I'll carry on with my research on the twin rads in terms of finding a CFD model with proven benefits. If there isn't a decent benefit of course it's not worth the bother ..

[Magic Beans]

If you've not read it before you should have a look at the thread below.

http://www.mr2oc.com/showthread.php?t=410768

It could be an interesting experiment to go with the rads solution you mentioned. I wouldn't invest too much in it, as if it was a significant improvement it would have been done before. In theory at least, you might just be pioneering something new

Keep us posted

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Thanks Phil I was reading the MR2OC CFD thread last night, seems to be leading somewhere but slowly ..

also note that in addition to the F430 the Porsche 996 (including GT2) run twin front rads. just need to get my head round this some more and I'll keep you posted for sure if I do the conversion.

[Magic Beans]

What's your main goal?

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less drag and lift from bulkhead