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Advantages of pannels on the bottom of your car ?
greavesy7 - 4/11/14 at 10:00 PM

I'm just in the middle of a n engine transplant on my gbs zero from a pinto to a zx9r engine. I have the chance to pannel off the bottom of my car as the engine does not stick past the chassi . What are the advantage of this if any.


snapper - 4/11/14 at 10:11 PM

Alledgely a smooth airflow under the car
However you need a rear diffuser to get any downforce
Disadvantage is that the hot air from the radiator has no where to go
IMHO not worth it


greavesy7 - 4/11/14 at 10:39 PM

I have got a diffuser but I kind of agree that it's prob not woth it


mark chandler - 4/11/14 at 11:13 PM

Top end and economy, leave it open like under the axle fuel tank and you have added two parachutes under your car.


jwhatley - 4/11/14 at 11:15 PM

I have one, I noticed a difference in cornering at high speeds on track.

Cooling isn't an issue with mine although I have wide side pods.

Big up side for me is the fact the engine bay stays a lot cleaner!

Mine is fixed on rivnuts, so removing it is a 5 minute job.

IMO, it's worth it for the cost of a bit of aluminium.


r1_pete - 5/11/14 at 08:05 AM

Many if not most production cars have under trays fitted now, even my L200 pickup, so there must be a benefit, I'd guess in production car use its mainly for economy.

If you had some rear facing louvres punched it could help with under bonnet airflow and cooling.


Doctor Derek Doctors - 5/11/14 at 08:29 AM

Combined with a diffuser mine creates a large and noticeable amount of downforce, it also acts as a guard when rubbing over kerbs and it's nice to have a lovely clean engine bay even after a wet Trackday or spinning it through the gravel. As above mines on rivnuts so 5 mins with an Allen key has the whole underside removed for access.


Smoking Frog - 5/11/14 at 09:51 AM

Increase chassis rigidity? Not quite the same benefit as fitting the back to flat-pack furniture but I'm sure it will bring something to the party.


mark chandler - 5/11/14 at 11:04 AM

It's all about the little changes once you have made your car.

Lose 5% weight
Lose 5% drag with underfloor sheeting back to front
Gain 5% more power

It's adds up and is cumulative so above is really 16.5% in total


Doctor Derek Doctors - 5/11/14 at 11:55 AM

quote:
Originally posted by Smoking Frog
Increase chassis rigidity?


Forgot to mention that, mine is a single piece of 5251 that runs the entire length of the car and is bolted on at all the node points.


Slimy38 - 5/11/14 at 12:37 PM

quote:
Originally posted by r1_pete
Many if not most production cars have under trays fitted now, even my L200 pickup, so there must be a benefit, I'd guess in production car use its mainly for economy.



I suspect it's mostly for decoration so the average Joe doesn't see all the 'horrible greasy bits' when they're in a showroom wanting to buy their new car. Same under the bonnet, I can't remember the last time I saw an engine rather than covers and panels covering everything.


Mr Whippy - 5/11/14 at 01:26 PM

quote:
Originally posted by Slimy38
quote:
Originally posted by r1_pete
Many if not most production cars have under trays fitted now, even my L200 pickup, so there must be a benefit, I'd guess in production car use its mainly for economy.



I suspect it's mostly for decoration so the average Joe doesn't see all the 'horrible greasy bits' when they're in a showroom wanting to buy their new car. Same under the bonnet, I can't remember the last time I saw an engine rather than covers and panels covering everything.


A lot of covers are acoustic too and help cut out high frequency chatter like tappets and diesel rattle.

I left of the bottom engine skirt of the wife’s cmax tdi and it was quite noticeably louder. Even the rubber seal under the back of the bonnet stops a surprising amount of noise, I take that off in the winter on my bluebird to let hot air from the engine flow over the windscreen to stop the wipers freezing up.


nick205 - 5/11/14 at 02:04 PM

Tin top engine covers are there primarily for sound deadening. The engine under trays are there for aerodynamics to aid fuel economy. If you look under a modern tin top the manufacturer's go to quite a lot of trouble to smooth the airflow under the vehicle. As Mark comments, it's the cumulative effect of small changes that make the difference.


Ivan - 6/11/14 at 02:09 PM

Have read of this - quiet informative.

http://www.autospeed.com/cms/article.html?&A=2159