LS7 Engine Bay Floor

[BIGNUMBER2]

I am fixing the pannels to the underside of my GTR at the moment,I'm putting an LS7 engine in and I'm planning on putting removable pannels under the engine bay,what I need to know is does the engine or any other component sit below the chasis or foul the area
around it in any other way.

[gtrclive]

That all depends on how you mount the engine... I would wait till after the engine install..

[gtrsimon]

Not sure on LS7 but the LS2 sits within the chassis, the engine bay floor will need to start flat and taper out to the lower chassis rail (flywheel) the sump sits below the main chassis by about 10mm but within flywheel chassis rail.

[steve_d]

I think a fair amount of the engine cooling will come from the air coming up from below. If you skin the underside you may end up with a rather hot engine bay.
The Factory definitely do not condone it.

Steve

[BIGNUMBER2]

I was planning on putting a series of forward facing vents in the panels to allow air to be forced in to the engine bay, the panels should help with downforce and help keep some of the crud away from the engine

[gtr-tt]

*IMHO* Our engines are water cooled not air cooled... If the floor makes a differense to the temperature then you need to fix your cooling system.

[gtrsimon]

From what I understand there should be no problem with engine cooling but the gearbox will nead air ducting over it. I intend to floor my rear end as well.

[boosted ls1]

BIGNUMBER2 said:

I was planning on putting a series of forward facing vents in the panels to allow air to be forced in to the engine bay, the panels should help with downforce and help keep some of the crud away from the engine

If you face them the other way, like a spoiler they may extract air and help with downforce by slowing the air speed under the car.

GTR Simon, could you fit an oil cooler to the box if you needed to?

Boosted.

[steve_d]

gtr-tt said:

*IMHO* Our engines are water cooled not air cooled... If the floor makes a differense to the temperature then you need to fix your cooling system.

I'm not considering the engine cooling as such, more the fact you have the whole of the exhaust system stuffed in there as well as the gearbox.

Steve

[BIGNUMBER2]

yeah its a good point steve, coolings going take a bit of thought but i still think its possible, has anyone done this before with any other engine?

[keperkey]

I thought that this was an interesting issue so I did a search. There are a number of posts discussing why this is a bad idea ranging from the temperature/cooling issues mentioned here to an aerodynamic issue related to making the car a wing. Lift off is a bad idea.

I know that the Lotus Elise has a flat bottom and a quick search of the net indicates that it does have several holes cut in (appear to be about 4-5 inches) apparently for cooling and maybe for air evacuation.

Edited by keperkey on Tuesday 20th February 21:59

[steve_d]

Seems like another good place to store gravel.

Steve

[luckyp]

I'm hearin' ya Steve!!

[boosted ls1]

keperkey said:

to an aerodynamic issue related to making the car a wing. Lift off is a bad idea.

I know that the Lotus Elise has a flat bottom and a quick search of the net indicates that it does have several holes cut in (appear to be about 4-5 inches) apparently for cooling and maybe for air evacuation.

Edited by keperkey on Tuesday 20th February 21:59

You can also have a curved underside but the chord line moves at different speeds which effects handling. I guess you would optimise it.

Boosted.

[chuntington101]

boosted ls1 said:

BIGNUMBER2 said:

I was planning on putting a series of forward facing vents in the panels to allow air to be forced in to the engine bay, the panels should help with downforce and help keep some of the crud away from the engine

If you face them the other way, like a spoiler they may extract air and help with downforce by slowing the air speed under the car.

GTR Simon, could you fit an oil cooler to the box if you needed to?

Boosted.

i allway thought you wanted high speed (low presure) under the car and high presure on the top side.

Chris.

[boosted ls1]

In profile the cars shaped like a wing that's upside down so the highest/thinnest air speed is over the top. A flat floor helps combat drag but if you have a curved underside then the apex will be nearer the ground so air underneath will speed up. I think this will redress the imbalance a bit. What was the fluid dynamics guys name, bouelli, raviolli ? He had a famous theory that's an established fact in physics. I'm no good with names.

A friend fitted a tray to a tr8 race car and he got more grip but the balance of the car varied with speed so I think it could have been fine tuned if it wasn't a one piece undertray.

Boosted.

[V8 VUM]

This is a very interesting subject and like others, I would like to cover the underside mainly to minimise the crud.

As for the debate regarding the vehicle acting like an aerofoil if flat panels are fitted, well...

.....I am no expert on this but, I have been very involved with aircraft a while ago..

firstly this behaviour I think would be very compromised by the fact that the foil is close to the ground, and therefore other physics come into play. To illustrate, has anyone done the school experiment with two sheet of paper, where you hold them faily close together and then blow hard between them? Instead of pushing the sheets apart as expected, the sheets actually get pushed together!!!!!

So..my theory calculation is that:

(Weight of the car + the ground/underside effect as above) - the low pressure factor of the curved top surface = still a very very sticky-to-the-ground car...

So with that hypothesis....I hand over the debate to the floor!!!!

Any Physicists about?

Keith

[Alan 2]

I have panelled the engine bay on both a Sports and a GTR. No overheating problems on the Sports in 8 years. The GTR is not on the road yet. It certainly keeps the muck off the engine and gearbox.

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[GTWayne]

Alan 2,
I have seen posts from yourself before and intend to do similar on the GTW. If it does seem to cause a problem I will simply remove the panelling, VOILA! Job's a good 'un. Surely the beauty of our cars is that you can try stuff and if it is not successful, alter it again. Folk do seem to loose sight of the fact that this is a 'Kit Car' and lends itself to modification unlike anything else (mainstream).
With regards to the heat in the engine bay being a problem with regards to the exhaust temp, I have always thought that it may be worth trying to alleviate this by ventilating the top of the rear clip more effectively because although radiant heat may well be a consideration (at least when stationary), the hot air will rise and if it can be helped along and have any restriction removed, it can only be a good thing.
I have got a pair of Spal fans to fit into the rear grill area of the GTW to aid cooling (combined they will shift 2400CFM) but only intend to use them when going to LM etc.

[BIGNUMBER2]

The theory is to make the air flow as fast and as undisturbed as possible beneath the car creating an area of low pressure, which sucks the car down, ie downforce