Engine bay spoiler info and advice?
Discussion
Hi all, I know there have been many threads about this but would like to pass on some info on what I have done, the results and advice from any air'o or race guys out there? My 4.5 LW did not have any splitter underneath to stop the air pressure build up under the bonnet at speed and so i got my son at F1 to make me a splitter. After seing a very damaged one at Top Cats. I measured it all up and made one 30" wide, with a one inch flat flange pop riveted through the floor right in front of the engine bay this is also in line with the wheels and helps clearance a little, it then had a one and a half inch wing at an angle forward that reduces the overall clearance by one inch about 25 degrees i think approx. Now as the general front clearance is only four and a half this then reduces it to three and a half?? yea banged it twice already? I got him to make it out of a light s/s so that if it did touch it would not cause any other damage just bend. Outcome after putting it on i did a trip to london and back 60 miles each way and keeping to the speed limit? took it to x mph were normally you can see the bonnet tryin to escape it stayed steady as a rock even more impressive was when i got home i then discovered in my stupidity i had not locked the bonnet down so it was all done without the lock on and so even more impressive. Have enclosed a couple of photos hope u can see clearly? Now my question to any experts is do you think i can get away with a much smaller lip say half an inch instead of the inch and a half i have. I think the angle of about 25 degrees seems to be good. if this would work it would increase clearance and not make it such a problem as it really does take nothing to sudenly become a bulldozer??
from the front looking back
from behind the engine bay looking forward
from the front looking back
from behind the engine bay looking forward
Funnily enough, I've just done something very similar. Mine was looking a bit the worse for wear, so I had the local machine chop make me a new one in aluminium.
I was planning to fit brake cooling ducts while I was busy with the suspension rebuild, but that plan has now been temporarily shelved.
I had reasoned that the ducts would have the effect of slightly increasing front end lift at speed, because they were channelling air at pressure into the wheel arches.
Therefore, in a wholly unscientific way, I specced the replacement spoiler 10mm longer (front to back).
Suspension is still in bits, so I can't tell you an effect (and I'm not sure I'll notice even when it is all back together).
Just one question - have you put that on the right way round? Seems funny to have a "scoop" pointing forwards?
I was planning to fit brake cooling ducts while I was busy with the suspension rebuild, but that plan has now been temporarily shelved.
I had reasoned that the ducts would have the effect of slightly increasing front end lift at speed, because they were channelling air at pressure into the wheel arches.
Therefore, in a wholly unscientific way, I specced the replacement spoiler 10mm longer (front to back).
Suspension is still in bits, so I can't tell you an effect (and I'm not sure I'll notice even when it is all back together).
Just one question - have you put that on the right way round? Seems funny to have a "scoop" pointing forwards?
jammy_basturd said:
Call me dumb, but the top pic is from the rear looking forward, no?
Also, why the lip? Why not just one flat smooth piece of material over as much of the underside as possible?
I won't call you dumm Jimmy Also, why the lip? Why not just one flat smooth piece of material over as much of the underside as possible?
Top pic is from the front facing the rear. How can you fix a flat peice of metal, so that it's angled downwards? Hence the lip.Edited by JensenA on Tuesday 17th February 16:30
It seems as though some are facing foreward and some to the rear 
here is a pic of mine posted a couple of months back.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Not sure if it has been changed, but I have no problems with bonnet movent.
here is a pic of mine posted a couple of months back.http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Not sure if it has been changed, but I have no problems with bonnet movent.
The Nige said:
It seems as though some are facing foreward and some to the rear here is a pic of mine posted a couple of months back.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Hi Nige, yep, yours is on the wrong way too, as BCA pointed out. Does look fresh round the edges as if it were new(er) - two wrongs don't make a right and all that. here is a pic of mine posted a couple of months back.http://www.pistonheads.com/gassing/topic.asp?h=0&a...
I may be wrong but if u look at the many posts about this i was told they are meant to face forward and then do two things act as a splitter as many other cars helping to keep the front down otherwise u are looking at putting on something that will try and make the car take off (not good)and of course reduce the air ram efffect into the engine bay? I was actually thinking of making it into a slight v and so feed the air directly back onto the front brakes? Maybe someone on here with racing experience could put us tight as I feel like a right T---d if it is back to front although that would be my first insticnt if i had not seen previous write ups in it??
My car doesn't have it's one on it any longer.
It wasn't on it when I got the car.
I spoke about whether or not it is worth having with ex-F1 and ex-WRC mechanic Eoin Corrigan.
The only benefit he could see in having it was to reduce the amount of air able to come up into the engine bay and thus reduce the potential of the bonnet catches being strained and the bonnet lifting.
However ..... because of the design of the area under the bonnet in front of the engine there is very little chance of air from below the car coming up from below.
Also, as the floor of the car is not flat, it has no aerodynamic benefit worth talking about.
So based on that, and as the roads around here are so bad, I decided against fitting one.
It wasn't on it when I got the car.
I spoke about whether or not it is worth having with ex-F1 and ex-WRC mechanic Eoin Corrigan.
The only benefit he could see in having it was to reduce the amount of air able to come up into the engine bay and thus reduce the potential of the bonnet catches being strained and the bonnet lifting.
However ..... because of the design of the area under the bonnet in front of the engine there is very little chance of air from below the car coming up from below.
Also, as the floor of the car is not flat, it has no aerodynamic benefit worth talking about.
So based on that, and as the roads around here are so bad, I decided against fitting one.
I dont agree on the fact air cannot get into the bay as as soon as the nose flat finishes u are straight into the engine bay with nothing to stop it and i have seen my bonnet at 130 plus definatly straining upwards and bowing slightly in the middle? Maybe as its a LW it might be a little more flimsy than the standard? And as I mentioned it made a massive difference as i forgot to lock the bonnet and drove 120 miles with the bonnet happily sitting there with no movemnt at all? I guess you could fill in that open flat area under the engine bay with a nice light ally section? (anyone done)I agree its going to be a real pain keeping it in one peice and if u do catch it u sure mess it up. I think when i am next back I might cut it right back to less than half an inch then it should be less prone to damage. Still would love to know for sure which way round is it meant to be a splitter ie, facing forward or a deflecting wing to push the air down?? Any more ideas out there??
Without the bonnet catch secured the bonnet on my cerb starts to lift at about 95 leptons and mine has lost its splitter so if you have no lift at 130 leptons then I`d say the splitter has a dramatic effect on engine bay pressure. Perhaps having it `the wrong way` gives more downforce to the front end also which has to be a good thing at speed?
Monitor at home shows the picture a lot more clearly, so I can see the silencers now! lol
I see, so the chin thing is acting more like an air dam, stopping the front from lifting at high speed, rather than directing the air smoothly under the car (which it would if it was backwards). In addition to being an air dam, I would have thought it would create a cushion of air in front of the lip, that would then also direct air a bit more smoothly under the car also.
Personally, if I was to seriously look into this, I'd start by getting a few sheets of hardboard or similar and cable tie it to as much of the chassis as possible to see what effect it had, and then if successful move on to a more permanent solution, with the help of my friends carbon and fibre.
I see, so the chin thing is acting more like an air dam, stopping the front from lifting at high speed, rather than directing the air smoothly under the car (which it would if it was backwards). In addition to being an air dam, I would have thought it would create a cushion of air in front of the lip, that would then also direct air a bit more smoothly under the car also.
Personally, if I was to seriously look into this, I'd start by getting a few sheets of hardboard or similar and cable tie it to as much of the chassis as possible to see what effect it had, and then if successful move on to a more permanent solution, with the help of my friends carbon and fibre.
DonnyMac said:
I won't call you dumb... but you can see the silencers in the top pic, and they're in entirely the wrong place if this photo was taken from behind 
The splitter is on back to front - it should be angled backward not forward - good job though.
D.
i believe he has it the right way round.The splitter is on back to front - it should be angled backward not forward - good job though.
D.
SO who is going to turn theirs round and gives us their insight into the best way to have it?
Mine faces backwards (less likely to get ripped off?), but bonnet still moves about a bit. May try bending it down at a bit.
Although bonnet has survived 150 leptons without problem, but I wasn't looking at it that much!
I might try reversing it to see the difference (camcorder on dash) when I get a chance.
Mine faces backwards (less likely to get ripped off?), but bonnet still moves about a bit. May try bending it down at a bit.
Although bonnet has survived 150 leptons without problem, but I wasn't looking at it that much!
I might try reversing it to see the difference (camcorder on dash) when I get a chance.
dean_ratpac said:
DonnyMac said:
I won't call you dumb... but you can see the silencers in the top pic, and they're in entirely the wrong place if this photo was taken from behind
The splitter is on back to front - it should be angled backward not forward - good job though.
D.
i believe he has it the right way round.The splitter is on back to front - it should be angled backward not forward - good job though.
D.
VPower said:
SO who is going to turn theirs round and gives us their insight into the best way to have it?
Mine faces backwards (less likely to get ripped off?), but bonnet still moves about a bit. May try bending it down at a bit.
Although bonnet has survived 150 leptons without problem, but I wasn't looking at it that much!
I might try reversing it to see the difference (camcorder on dash) when I get a chance.
Mine is the same as yours VPower. Lifts at about 90 if not locked down (heart stopping moment the first time).Mine faces backwards (less likely to get ripped off?), but bonnet still moves about a bit. May try bending it down at a bit.
Although bonnet has survived 150 leptons without problem, but I wasn't looking at it that much!
I might try reversing it to see the difference (camcorder on dash) when I get a chance.
With a rearward facing lip the logic is(IMO) the air flowing over the lip causes a vortex behind the lip which spills into the void of the engine bay sucking air, that would normally be passing under the car if no lip fitted, into the engine bay also.
My bonnet strains on the latches and bows at higher speeds!!!!
Reversing the lip to face forwards or blanking the opening off a little more could well solve the problem and cut lift. Got to watch water temperature though.
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