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Effects of metal sheet under engine area?

AdrianH - 19/6/12 at 08:52 PM

I am planning on fitting a sheet of aluminium across the bottom of the engine bay, as the sump sits 25mm'ish below the chassis the sheet will be cut around it.

I would like to ask if anyone has done this and then had issues with over heating especially oil temps and also if the bonnet is more or less likely to lift with one on or off?

The engine has only moderate power so hoping to eliminate a bit of drag at motorway speeds and help acceleration if I can getting up there, but wonder if the air flow could be reduced around the oil pan or more pressure build up in the engine compartment could cause the bonnet to lift.

You thoughts as always welcome.

Adrian

coozer - 19/6/12 at 08:54 PM

Just think about air flow through the body, maybe some vents in the bonnet especially the rear edge next to the scuttle?

And, last not least, bits of stones rattling round on top

mark chandler - 19/6/12 at 11:07 PM

Mine is all panelled in with just a little hole for the sump, I had to provide a lot of bonnet venting to release the air, started off with louvers, now have 2" holes down the side as well, it used to lift above 90 at the rear edge

AdrianH - 20/6/12 at 06:24 AM

That would then be a problem for me as the bonnet and sides are sprayed and I would not like to stick holes in them. I was wondering how much air came in to the engine compartment from underneath but by the sounds of it not a lot, virtually all being from the front grill (Obvious I know).

What I could do is leave a gap of a few inches in the panel at the rear of of the engine bay before the bulkhead for air to exit, this is still dumping the air underneath the car as well as what little goes down the tunnel.

I could do with some form of pressure meter to measure before and after and some thing better then the rubber IVA bonnet clamps!

Adrian

[Edited on 20-6-12 by AdrianH]

mcerd1 - 20/6/12 at 07:22 AM

flared side panels could be the answer...

907 - 20/6/12 at 08:12 AM

quote:
Originally posted by AdrianH

I could do with some form of pressure meter to measure before and after ....

Adrian

[Edited on 20-6-12 by AdrianH]

You can measure Milli Bars with a water gauge.

A simple length of clear plastic pipe with the end bent into a U, and fill the bottom of the U with water.

10M of height differential in the U = 1 Bar, so 10mm = 1mb. (I think I've got the maths right)

( I used this method to test a pre-set Calor Gas reg. 370mm between the water levels in the tube = 37mb.
It turned out that the reg was OK, but the new range cooker was fitted with mains gas jets.
It boiled an egg in under a minute though.

)

Don't know if this would work in a car if the U was taped to the dash? It might work in a straight line but
I think the levels would change round corners.

Face full of water at the first left hander?

Cheers,
Paul G

[Edited on 20/6/12 by 907]

dhutch - 20/6/12 at 08:18 AM

What about a pair of big naca ducts in floor tray?

Not panneled mine, but something I though of if i ever did.

MikeRJ - 20/6/12 at 08:23 AM

quote:
Originally posted by AdrianH
That would then be a problem for me as the bonnet and sides are sprayed and I would not like to stick holes in them. I was wondering how much air came in to the engine compartment from underneath but by the sounds of it not a lot, virtually all being from the front grill (Obvious I know).

Just remember that no air will be going into the engine bay unless it can get out again!

sickbag - 20/6/12 at 08:53 AM

Would be better if the engine bay air was dumped out of the sides rather than underneath? As it'll just add to the air that would normally go underneath the car and make the rear lift that bit more?

I'm asking because I want to panel all of my underside - front to back - and plan on dumping the air from the engine bay through flared side panels as in the picture posted by mcerd1.

loggyboy - 20/6/12 at 09:19 AM

quote:
Originally posted by MikeRJ
Just remember that no air will be going into the engine bay unless it can get out again!

'Less' air strictly speaking, as the engine bay will never even be close to perfectly sealed.

nick205 - 20/6/12 at 09:49 AM

Will paneling the engine bay floor really give a noticeable difference to drag/acceleration?

(BTW - I'm asking because I don't know the answer)

AdrianH - 20/6/12 at 12:07 PM

I don't know the answer myself, but thought it worth the try!

When I have looked at Caterham type sprint cars they have been panelled underneath. I guess it is a bit like the rear difusers being fitted under the boot area at the back to reduce drag caused by the large vertical section catching the air.

I have assumed the same effect will happen in the engine bay.

I will have the hole for the sump and it will also be open around the bell housing and gearbox area, so I will have to find out what effects it has. I have a few burette tubes that I could use as a manometer, but have also wondered about using a MAP sensor, have one on a spare Megajolt and they will run from partial vacuum to approx 3 bar, but how sensitive they are to get a repeatable and trusted couple of readings is anyone's guess.

Adrian

[Edited on 20-6-12 by AdrianH]

amalyos - 20/6/12 at 02:30 PM

Panelling the underfloor is an easy gain on aero for a seven, but it will deifinately increase your engine temps, if you don't vent somewhere.

When I did my RGB car, I had my bonnet lifting 1/2" in the center when I was at speed, due to the trapped air.

I had to cut the sides out and put some flared vents in, this fixed the problem.

snapper - 20/6/12 at 02:55 PM

I don't think you will see the benefit of a panelled bay floor.
You will however feel the disadvantage of overheating.
It's a road car
It will stand still in traffic and spend more time at low speed than high, getting rid of engine bay heat is a big issue.

40inches - 20/6/12 at 03:50 PM

quote:
Originally posted by AdrianH
I don't know the answer myself, but thought it worth the try!

When I have looked at Caterham type sprint cars they have been panelled underneath. I guess it is a bit like the rear difusers being fitted under the boot area at the back to reduce drag caused by the large vertical section catching the air.

I have assumed the same effect will happen in the engine bay.

I will have the hole for the sump and it will also be open around the bell housing and gearbox area, so I will have to find out what effects it has. I have a few burette tubes that I could use as a manometer, but have also wondered about using a MAP sensor, have one on a spare Megajolt and they will run from partial vacuum to approx 3 bar, but how sensitive they are to get a repeatable and trusted couple of readings is anyone's guess.

Adrian

[Edited on 20-6-12 by AdrianH]

Is this Differential Pressure Gauge -10-700 Pascal w 1.8m Cable | eBay
ebay

any good?

motorcycle_mayhem - 20/6/12 at 05:14 PM

I leave the floor open under the engine. It's not an F1 car, my opinion is that there isn't much aero gain closing it off.

It helps engine inspection if it's all open, along with providing a path for the ready exit of oil when a rod comes through the block.

MikeRJ - 20/6/12 at 05:41 PM

quote:
Originally posted by loggyboy

quote:
Originally posted by MikeRJ
Just remember that no air will be going into the engine bay unless it can get out again!

'Less' air strictly speaking, as the engine bay will never even be close to perfectly sealed.

Strictly speaking my statement was "none out = none in", which is perfectly true, as is "Little bit out = little bit in"!

AdrianH - 20/6/12 at 07:32 PM

quote:
Originally posted by 40inches

Is this Differential Pressure Gauge -10-700 Pascal w 1.8m Cable | eBay
ebay any good?

Wow 700 pascals converts to 0.1 psi that is one sensitive unit. Perhaps a bit to much so.

I had a look at grills and came up with the BMW/Mini series 1 vent that goes on the windscreen panel, not seen one in real life so do not know if one in each side panel would look OK?

This is a picture of the panel I have cut so far, still to fit obviously, just trying to come up with a good way of fitting without drilling holes so I can fit and then remove later when my problems start.

under engine panel .

I have my pipette, just need to get some a few meters of clear tubing to play with and I will give things a try.

Adrian

I know how I could see if it benifits the car, by going back to York race track at a RWYB and seeing if I can get the terminal speed over the 83 mph average

Run Time Catagory Dialin Reaction 60 Foot 1/8 ET 1/8 MPH 1/4 ET 1/4 MPH
09:58:53 RWYB - CAR 0.00 1.1449 2.6250 10.5202 67.3500 16.4381 80.6100
10:05:54 RWYB - CAR 0.00 1.1307 2.5510 10.2871 68.7000 16.0663 83.5000
10:12:39 RWYB - CAR 0.00 1.0201 2.5520 10.3810 67.9500 16.2207 82.2500
10:17:10 RWYB - CAR 0.00 1.0639 2.4289 10.1133 68.7800 15.8941 83.3300
10:23:45 RWYB - CAR 0.00 1.1410 2.4941 10.2389 68.2800 16.0421 82.3900

[Edited on 20-6-12 by AdrianH]

AdrianH - 7/7/12 at 04:38 PM

I did a small run out today with a home made manometer attached to the dash with the inlet tube at the back of the engine bay up by the bonnet.

The maximum change in water height I detected was 45mm, so an on-line calculator gets that at 0.064 psi, quite low.

If considered over a 1 meter square bonnet area that is still 100lbs of lift. Not very scientific I know but a start.

Adrian.

steve m - 7/7/12 at 05:53 PM

"I don't think you will see the benefit of a panelled bay floor.
You will however feel the disadvantage of overheating.
It's a road car
It will stand still in traffic and spend more time at low speed than high, getting rid of engine bay heat is a big issue. "

My mondeo is fully enclosed , so why not a 7

yellowcab - 7/7/12 at 07:03 PM

This is what I made:

quote:
Originally posted by yellowcab
Firstly would like to apologise to Colin/ ReMan - I said I'd pop over today to lend a hand but I completely forgot, wasn't intentional, intact, I was oblivious until the wife said 'are you not going over Cols anymore...' - Sorry bud! D'oh!

Not much of an update, got the front aero diffuser / splitter powder coated, had it back today

Open under side before and after...

Side on view for those that sent me a message asking for one

Open rear end to let out hot air

Made the centre piece removable for oil changes, and quick fixes

That's all folks!

AdrianH - 7/7/12 at 08:09 PM

yellowcab

I notice you already have big vents on the sides of the car.

Description

This is something I do not not have, which is why I am being warned about over heating .

I have a hole around the exhaust, but not much else, so I am considering a mesh vent in the bonnet, if I can find one I like.

I know yours is more of a performance car, so have you noticed any improvements in getting up to speed would be my question, the 7 is as aero-dynamic as a brick generally and I see bits of fins etc. stuck on cars, to try and make them better and just considered the engine bay should be covered as much as the rear tub.

The engine only provides 95 ish BHP so the car will never be a rocket ship, that still does not mean I should not try to improve it.

Adrian