My Functional Front Splitter Build
.........learning the hard way is often the only option
02-03-2013, 04:06 PM
#52
I lost a genuine MS bumper because my splitter was attached to the bumper and i had splitter struts and a support bar inside the bumper that was attached to the frame.
I stongly recommend to not attach to the bumper. Come up with something else.
And what material are you using for the splitter? Looks like some sort of wood. Im not a fan. I like alumalite. Strong but cheap and it will bend and flex if hit hard.
Lastly i hate splitters for street use and it wont take ling before you will too.
Good luck.
I stongly recommend to not attach to the bumper. Come up with something else.
And what material are you using for the splitter? Looks like some sort of wood. Im not a fan. I like alumalite. Strong but cheap and it will bend and flex if hit hard.
Lastly i hate splitters for street use and it wont take ling before you will too.
Good luck.
I'm going to use Flitelam UNS It's a sandwich panels comprising uni-directional glass skins on Nomex honeycomb core which comply with All Aviation Specifications. Needless to say it will be up from for the job And it's free (for me, the sheets retail at over £800 each.
And lasty, It's a track only trackday car with will never see the streets.
03-24-2013, 04:48 PM
#55
Mine has been just attached to the bumper since I built it, I haven't made any changes really. I've still never had any failures at speeds up to 125MPH and even after large impacts while I was out mowing down bushes on the side of the track lmao.
I'm working on a second version now that is much larger, about 2" further out and 2" wider, made of alumalite, and will have cables that will be attached to the two front tow hooks for support as well as the bumper whiskers.
I'm working on a second version now that is much larger, about 2" further out and 2" wider, made of alumalite, and will have cables that will be attached to the two front tow hooks for support as well as the bumper whiskers.
04-10-2015, 09:46 PM
#64
rev it up
Lowering the car and adding a chin to the front bumper will reduce the amount of air flowing under the car. This will reduce lift created by air flowing under the car, less drag from turbulent air under the car.
01-16-2016, 12:36 PM
#65
Registered
All very interesting. IMO there's a lot not said.
As eluded earlier, a splitter is OK for the track but not for the road. The splitter needs to be so close to the ground to be effective, below 2" say, that it's only really effective on track with stiffened suspension. Sure, you'll get some effect at greater ride heights, particularly when braking for a corner, but average drivers will be better spending their time and effort elsewhere. The only splitters I've seen on road cars have led me to look down on an owner that I think is a boy racer trying far too hard to impress.
The MX5 data is useful if taken in context and allowance made for its deficiencies - it is from computer modelling where I doubt the model is correctly specified. That said, the conclusions are hardly unexpected: an air dam with a low ground clearance reduces drag and a splitter increases front downforce.
I'm now, at best, an average track day driver (my kids have excellent driver skills that they must get from me, as that explains why I have none left) so hesitate to say anything about handling when fast drivers are more authoritative. That said, I like balance in handling and am against the average driver having a splitter and/or rear wing on the road and having one without the other on track. By all means play with sway bar settings on track but the average driver will be out of his depth and will really want someone with skill and knowledge to tell him "do this".
For my project car, a 13B REW conversion with 360-380 rwhp on the road and 400-450 rwhp on track, I'm developing a quick-change splitter for track use that will be close to Arca's design. It will be completely useless on road - anything less than a 5" ground clearance will ground on the speed bumps near my place.
As eluded earlier, a splitter is OK for the track but not for the road. The splitter needs to be so close to the ground to be effective, below 2" say, that it's only really effective on track with stiffened suspension. Sure, you'll get some effect at greater ride heights, particularly when braking for a corner, but average drivers will be better spending their time and effort elsewhere. The only splitters I've seen on road cars have led me to look down on an owner that I think is a boy racer trying far too hard to impress.
The MX5 data is useful if taken in context and allowance made for its deficiencies - it is from computer modelling where I doubt the model is correctly specified. That said, the conclusions are hardly unexpected: an air dam with a low ground clearance reduces drag and a splitter increases front downforce.
I'm now, at best, an average track day driver (my kids have excellent driver skills that they must get from me, as that explains why I have none left) so hesitate to say anything about handling when fast drivers are more authoritative. That said, I like balance in handling and am against the average driver having a splitter and/or rear wing on the road and having one without the other on track. By all means play with sway bar settings on track but the average driver will be out of his depth and will really want someone with skill and knowledge to tell him "do this".
For my project car, a 13B REW conversion with 360-380 rwhp on the road and 400-450 rwhp on track, I'm developing a quick-change splitter for track use that will be close to Arca's design. It will be completely useless on road - anything less than a 5" ground clearance will ground on the speed bumps near my place.
01-16-2016, 11:52 PM
#66
Dang. Thread is 4 years old now.
I daily drove the car with that splitter for almost 6 months, pretty much no issues. At that ride height.
Not sure what the whole street car argument was in reference to but the car is a dedicated track car now. Or dedicated jackstand car, whatever way you want to look at it.
I daily drove the car with that splitter for almost 6 months, pretty much no issues. At that ride height.
Not sure what the whole street car argument was in reference to but the car is a dedicated track car now. Or dedicated jackstand car, whatever way you want to look at it.
01-17-2016, 12:35 PM
#67
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You can't keep a good thread down.
Bit by bit I'm writing a thread on aero for RX8 turbo conversions here and I'll be doing something on air dams, splitters, spoilers and wings when my project gets to building those. For anyone reading this who is thinking of building a splitter and/or air dam:
The aerodynamic forces are proportional to the square of the car's speed so you may get relatively insignificant performance increases at road speeds.
The behaviour of any design depends heavily on the circumstances and the 'best' one can only be determined by extensive testing, which few amateurs have the time and money for. 
Think an air dam will decrease drag? There are loads of factors in play and some cars see an increase in drag with an air dam.
Think lowering your car will reduce drag by limiting the volume of air bouncing around underneath? Below a certain height, which could easily be 4" for a road car, drag actually increases. AFAIK no-one has done a practical investigation on RX8s so I have no idea what the optimum height is for us.
Think you can use computer analysis like that above with confidence? The difficulties of modelling a car's underside and the moving road underneath mean that any results are highly suspect; yes, car manufacturers evaluate designs by computer but they then spend masses of money, time and effort in wind tunnel testing and redesigning. That said, some practical tests on cars not unlike the RX8 suggest that: The maximum length of a splitter should be 4"
Extending the width of a splitter beyond the end of the bumper creates a lot of drag without increasing downforce (sorry, Arca, you need to cut off those end bits).
Extending the splitter to the line of the outside of the tyre and fairing it into the wheel arches with a canard-style fillet generally improves downforce for a relatively small increase in drag.
The best shape is akin to a thick aerofoil turned upside down with the upper surface joining the bumper at about 1/3 chord pointing slightly upwards and the lower surface continuing underneath the engine bay to form a venturi. However, the reduction in lift over a straight plate is heavily dependent on ride height and may not be significant for a road car.
A splitter will decrease lift (ie provide downforce) at the front axle but will increase lift at the rear axle, thus requiring the rear to be modified, for example with a wing, spoiler or diffuser, to regain balance. I prefer a combined splitter and air dam like that in the first picture as a the best combination of effect and looks for a road-going RX8. If I went off-the-shelf I'd go for the one in the 2nd & 3rd images, with the option of fitting a flat-plate splitter for track work (with a wing added at the back).
Bit by bit I'm writing a thread on aero for RX8 turbo conversions here and I'll be doing something on air dams, splitters, spoilers and wings when my project gets to building those. For anyone reading this who is thinking of building a splitter and/or air dam:
The aerodynamic forces are proportional to the square of the car's speed so you may get relatively insignificant performance increases at road speeds. The behaviour of any design depends heavily on the circumstances and the 'best' one can only be determined by extensive testing, which few amateurs have the time and money for. Think an air dam will decrease drag? There are loads of factors in play and some cars see an increase in drag with an air dam. Think lowering your car will reduce drag by limiting the volume of air bouncing around underneath? Below a certain height, which could easily be 4" for a road car, drag actually increases. AFAIK no-one has done a practical investigation on RX8s so I have no idea what the optimum height is for us. Think you can use computer analysis like that above with confidence? The difficulties of modelling a car's underside and the moving road underneath mean that any results are highly suspect; yes, car manufacturers evaluate designs by computer but they then spend masses of money, time and effort in wind tunnel testing and redesigning. That said, some practical tests on cars not unlike the RX8 suggest that: The maximum length of a splitter should be 4" Extending the width of a splitter beyond the end of the bumper creates a lot of drag without increasing downforce (sorry, Arca, you need to cut off those end bits). Extending the splitter to the line of the outside of the tyre and fairing it into the wheel arches with a canard-style fillet generally improves downforce for a relatively small increase in drag. The best shape is akin to a thick aerofoil turned upside down with the upper surface joining the bumper at about 1/3 chord pointing slightly upwards and the lower surface continuing underneath the engine bay to form a venturi. However, the reduction in lift over a straight plate is heavily dependent on ride height and may not be significant for a road car. A splitter will decrease lift (ie provide downforce) at the front axle but will increase lift at the rear axle, thus requiring the rear to be modified, for example with a wing, spoiler or diffuser, to regain balance. I prefer a combined splitter and air dam like that in the first picture as a the best combination of effect and looks for a road-going RX8. If I went off-the-shelf I'd go for the one in the 2nd & 3rd images, with the option of fitting a flat-plate splitter for track work (with a wing added at the back).
Last edited by Ian_D; 01-20-2016 at 05:48 AM. Reason: Added image
01-19-2016, 04:23 AM
#69
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Aerodynamics remains one of my major interests and I'm happy to consider anything new, particularly if discussed healthily (I don't want to argue with you either, so that's us both happy).
Please explain why you think my comments are simply not true. I took care to write only what I could back up with academic and/or practical research. As well as being of interest to me, I'm sure any contradictory evidence would be useful for others to consider for their own research.
Please explain why you think my comments are simply not true. I took care to write only what I could back up with academic and/or practical research. As well as being of interest to me, I'm sure any contradictory evidence would be useful for others to consider for their own research.
02-07-2016, 02:19 AM
#70
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Some of what you said does make sense however
I don't really know the technicalities, but if you look at the aero designs of a lot of race cars, they do extend beyond the bumper. Surely, considering the level of R&D put into designing these cars, it would suggest that there is an increase in downforce?
"Extending the width of a splitter beyond the end of the bumper creates a lot of drag without increasing downforce (sorry, Arca, you need to cut off those end bits)."
02-08-2016, 08:27 AM
#71
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Rakesh, I don't know of any professionally-designed race cars with splitters that extend beyond the bumper. What cars are you thinking of?
Let me elaborate. A splitter works by generating a higher pressure above it by slowing air down above it; depending on the shape of the undersurface it may also lower pressure underneath it (by creating a venturi). At the ends of the bumper the upper air flow angles towards the outside and the pressure on the upper surface moves towards atmospheric; if the splitter ends there then there is a small vortex created that produces a little drag. However, if the splitter is carried on as in Arca's design then there is effectively no downforce over the extra bit as the air flows are at the same speed and static pressure; however, the extension pushes the vortex further out, creating more drag by itself and more often than not by interacting with the flow out of the front wheel wells.
I just did a quick Google search and found the article here that covers someone's practical experience. And this one on wind tunnel testing of end plates.
Let me elaborate. A splitter works by generating a higher pressure above it by slowing air down above it; depending on the shape of the undersurface it may also lower pressure underneath it (by creating a venturi). At the ends of the bumper the upper air flow angles towards the outside and the pressure on the upper surface moves towards atmospheric; if the splitter ends there then there is a small vortex created that produces a little drag. However, if the splitter is carried on as in Arca's design then there is effectively no downforce over the extra bit as the air flows are at the same speed and static pressure; however, the extension pushes the vortex further out, creating more drag by itself and more often than not by interacting with the flow out of the front wheel wells.
I just did a quick Google search and found the article here that covers someone's practical experience. And this one on wind tunnel testing of end plates.
Last edited by Ian_D; 02-09-2016 at 07:16 AM. Reason: Added second example
02-09-2016, 08:49 AM
#72
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Rakesh, I don't know of any professionally-designed race cars with splitters that extend beyond the bumper. What cars are you thinking of?
Let me elaborate. A splitter works by generating a higher pressure above it by slowing air down above it; depending on the shape of the undersurface it may also lower pressure underneath it (by creating a venturi). At the ends of the bumper the upper air flow angles towards the outside and the pressure on the upper surface moves towards atmospheric; if the splitter ends there then there is a small vortex created that produces a little drag. However, if the splitter is carried on as in Arca's design then there is effectively no downforce over the extra bit as the air flows are at the same speed and static pressure; however, the extension pushes the vortex further out, creating more drag by itself and more often than not by interacting with the flow out of the front wheel wells.
I just did a quick Google search and found the article here that covers someone's practical experience. And this one on wind tunnel testing of end plates.
Let me elaborate. A splitter works by generating a higher pressure above it by slowing air down above it; depending on the shape of the undersurface it may also lower pressure underneath it (by creating a venturi). At the ends of the bumper the upper air flow angles towards the outside and the pressure on the upper surface moves towards atmospheric; if the splitter ends there then there is a small vortex created that produces a little drag. However, if the splitter is carried on as in Arca's design then there is effectively no downforce over the extra bit as the air flows are at the same speed and static pressure; however, the extension pushes the vortex further out, creating more drag by itself and more often than not by interacting with the flow out of the front wheel wells.
I just did a quick Google search and found the article here that covers someone's practical experience. And this one on wind tunnel testing of end plates.
Fair point Ian, what you said does make sense. So you're saying that extending the splitter past the bumper doesn't do anything as it create any pressure differential from above and beneath the splitter until it reaches under the bumper? Something like that?
Isn't this classified as a splitter going past the bumper?
That was my understanding!
02-10-2016, 05:24 AM
#74
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Rakesh, effectively, yes. The airflows under and over the splitter will effectively be at the same speed and static pressure there.
IMO that splitter does not go past the bumper. The lower bumper/air dam at the splitter is shaped to come to the outside of the splitter and there is no splitter beyond the edge of the bumper; although academic, note too that the splitter ends are within the line of the upper bumper.
I expect the design of that splitter and air dam reflect the particular regulations for that race class, for example there may be a restriction that a splitter may not extend beyond the sides of the bumper and, say, 1/2" forwards from the line of the bumper. The shape of the lower/bumper is therefore set back to give room for the splitter and the shape of the ends probably reflects pushing the air outwards to avoid the turbulence of the front wheels (Nascar speeds are far higher ours, with aerodynamic forces typically 4 times ours so this may not be the best design for us).
Note also that the downforce from the ends of the splitter is lower than at the centre because the airflow shapes to go around the bumper and the speed drop, and hence static pressure rise, reduces.
There are 2 further causes of drag that I didn't mention in order to keep the post short: unless aerodynamically shaped (in which case that bit of splitter becomes a wing), the front of the splitter will cause the air to separate for a short distance and hence generate drag (see here an analysis on a Spyker that I Googled which is perhaps more useful for covering the cross-sectional shape of a splitter in some detail); secondly, when the splitter gets close to the ground it starts to generate noticeable interference drag.
IMO that splitter does not go past the bumper. The lower bumper/air dam at the splitter is shaped to come to the outside of the splitter and there is no splitter beyond the edge of the bumper; although academic, note too that the splitter ends are within the line of the upper bumper.
I expect the design of that splitter and air dam reflect the particular regulations for that race class, for example there may be a restriction that a splitter may not extend beyond the sides of the bumper and, say, 1/2" forwards from the line of the bumper. The shape of the lower/bumper is therefore set back to give room for the splitter and the shape of the ends probably reflects pushing the air outwards to avoid the turbulence of the front wheels (Nascar speeds are far higher ours, with aerodynamic forces typically 4 times ours so this may not be the best design for us).
Note also that the downforce from the ends of the splitter is lower than at the centre because the airflow shapes to go around the bumper and the speed drop, and hence static pressure rise, reduces.
There are 2 further causes of drag that I didn't mention in order to keep the post short: unless aerodynamically shaped (in which case that bit of splitter becomes a wing), the front of the splitter will cause the air to separate for a short distance and hence generate drag (see here an analysis on a Spyker that I Googled which is perhaps more useful for covering the cross-sectional shape of a splitter in some detail); secondly, when the splitter gets close to the ground it starts to generate noticeable interference drag.
Last edited by Ian_D; 02-10-2016 at 05:29 AM.
02-10-2016, 09:09 AM
#75
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Now I understand you, I misunderstood when you said past the bumper, I completely forgot about the side of the bumper.
With regards to interference drag, I learnt a lot about that with the spoon and sink experiment. Seeing how water flows when it hits the spoon. I think that was mostly emphasising the effects of increasing the rake of the underbody or the rear diffuser angle.
Aerodynamics is such a complex topic haha, really interesting though.
With regards to interference drag, I learnt a lot about that with the spoon and sink experiment. Seeing how water flows when it hits the spoon. I think that was mostly emphasising the effects of increasing the rake of the underbody or the rear diffuser angle.
Aerodynamics is such a complex topic haha, really interesting though.