Undertray

[Mr2highpeak]

Hi, what's your thoughts on the undertray, can I leave them off or should they be fitted.

[Petrus]

Hi, what's your thoughts on the undertray, can I leave them off or should they be fitted.

It depends.
Have a search on the subject.

Quite an interesting finger point is what TTE did. Apart from the fans, more on topic; where they put the intercooler of their Turbo kit.

Also very interesting what @AdamR28 did/experienced with his track special.

[SV-3]

Hi, what's your thoughts on the undertray, can I leave them off or should they be fitted.

MrT fitted them - that's good enough for me.
Check and where necessary replace the fastenings.
Car designers generally favour a 'smoothed/aerodynamic' floorpan.

[Joesson]

MrT fitted them - that's good enough for me.
Check and where necessary replace the fastenings.
Car designers generally favour a 'smoothed/aerodynamic' floorpan.

I favour them for the above reasons and also because I believe they (Back and Front) reduce the amount of road dirt that accumulates in the engine and steering bays.

[Petrus]

The primary reason Mr.T. fitted the rear ones was meeting legal noise requirements.

Aero wise the front and rear undertrays cannot be compared.
By all means see it as taking the front bumper skirt or rear one off. Taking off the front will seriously increase frontal resistance, taking off the rear is likely to decrease drag.

After a lót of a lot     I took them off because of the fire risk the rear one under the cat. posed. Then took the one under the engine off to improve air flow.

@Ardent has the TTTE turbo kit fitted and the intercooler is a good pointer.

[J88TEO]

I took the rear ones off and that help the engine bay cooling.

[Petrus]

Engine bay temps of the MR2 are a neat subject btw.
Contrary to what you would expect it is actually a cóóler set up than front engined but it ís more prone to escalating temps in slow/no speed use. This again nicely illustrated by TTE with their turbo install: The fans in the engine lid blow dównwards. The telling bit being that the natural flow is oút of the top... Cóól no?!   
 

[J88TEO]

They installed it wrong side up!? 

[fawtytoo]

Engine bay temps of the MR2 are a neat subject btw.
Contrary to what you would expect it is actually a cóóler set up than front engined but it ís more prone to escalating temps in slow/no speed use. This again nicely illustrated by TTE with their turbo install: The fans in the engine lid blow dównwards. The telling bit being that the natural flow is oút of the top... Cóól no?!   
 

Surely that's just blowing the hot air back down onto it?
Given hot air rises, I'd of put the fans underneath. That might of sucked the car onto the road a bit too.

[Petrus]

Surely that's just blowing the hot air back down onto it?
Given hot air rises, I'd of put the fans underneath. That might of sucked the car onto the road a bit too.

Well, they did take their tome developing it and it was covered by Toyota warranty 

As it is the TTE turbo install make two air flow thing clear:
1. That there is a lower pressure inside of the engine tray than under the car; hence the intercooler placing.
2. That under low/no speed circumstances (thus no flow under the car cooling down the inlet air) temp can escalate and needs blowing down even if that is against the natural flow.

All in all there is in standard trim no nééd to remove the undertrays and they will indeed keep dust out which also points at them keeping the air flow out.

Pick your choice.

In the UK I would probably have left both under the car. As observed, under mine over here the rear one was a fire hazard (see Belle´s thread) and taking the other off was part of the rest of the aero mods.

[Joesson]

I feel a sense of déjà vu!
When the direction of flow of the TTE turbo cooling fans was discussed previously I found the Mr T solution less than intuitive, but apparently it works !

[Petrus]

I feel a sense of déjà vu!
When the direction of flow of the TTE turbo cooling fans was discussed previously I found the Mr T solution less than intuitive, but apparently it works !

The thing is Jason, that in OEM guise the vents have véry little functional role. The drip tray blocks the flow quite effectively. As such the two fans do not block any natural flow and it is most effective to blow cooler outside air in straight from above.
In OEM guise taking the drip tray out creates extra flow. The plastic cover on the valve cover keeps the coils/plugs dry. The TTE turbo does not have the drip tray either 

[Ardent]

Given I have a tte turbo setup in full fat vanilla guise.
All I know is, it works.

It would seem the Toyota R+D Dept. knew what they were doing.

Plug n play fit n forget. It just works.

Despite thinking, that's not right, when I first worked out which way the fan works.

[Mr2highpeak]

Ok so I think I will leave the rear undertray off for now. Cheers guys for all your input.

[Dev]

I believe one part of the underside was an option in Japan and was standard everywhere else. I believe it was considered a garnish of sorts.
These engines run cool no matter where they are placed because of its modern design and temperature regulation. Unless the oil or water temps are out of bounds there is no need for any cooling measures.
 People tend to add more than they need complicating their set up when what they should do is monitor them first and then make that decision.
 
 It is speculated by BOE that when Lotus used two oil coolers for the Elise it ruined the intake came due to having the engine oil temp too cold for the conditions.
 It is just as important that the engine is hot enough and not messed with unless you are pushing the car into the extremes for the kind of use.

[Ardent]

Just for the record I took a couple of pics of the TTE drip tray - fan setup and the thermo sensor.

[Petrus]

Just for the record I took a couple of pics of the TTE drip tray - fan setup and the thermo sensor.

Thanks for showing us the sucker 

[Joesson]

Thanks for showing us the sucker 

I thought this had been considered, discussed, examined and reviewed and found not to be a sucker, but a blower!
But that is a matter of perspective, in that it sucks air from the outside and blows it into / through the engine bay.

[Petrus]

I thought this had been considered, discussed, examined and reviewed and found not to be a sucker, but a blower!
But that is a matter of perspective, in that it sucks air from the outside and blows it into / through the engine bay.

Pov Joesson, pov; as it is mounted on the inside it súcks air throúgh the engine lid into the engine bay