Engine undertray

[scm2004red]

Having started to poke a bit more around my 2004 Red Edition,I am starting to clock up a few queries.

I assume there is a plastic undertray beneath the engine, which is missing on mine. Judging by the state of things under there I suspect the fastenings seized and eventually some grease monkey ripped it off.  Presumably the fixings are all steel (hasn't anyone ever heard of stainless fastenings ) I can find about 4 locations where they should be , can anyone confirm the correct number please. Looks as though the fixing brackets can be removed for repair/rectification.

There are 2 further undertrays forward of the engine which appear to have plastic fasteners I presume this is normal in this case.

Need to obtain an undamaged undertray if anyone knows a source.

[Topdownman]

This is what is often called the "nappy".

I,like many dont have have one anymore. Its OK not to have one if you havent got one/ dont want one.
I think from memory there are 3 fixings on the rear edge and 4? in the middle and front.

Its very common to use zip ties for the middle and front fittings and just cut and replace when it is removed. Some do replace with stainless fittings.

[scm2004red]

I'm afraid i take the view that Mr Toyota didn't spend millions on designing and testing our motorcar with an undertray so that we can bin it.

Have a similar problem with the Porsche 924, it has a fitted undertray which which directs air through the engine compartment, and eventually the fittings seize or break off and it gets binned, then people wonder why the get excessive underbonnet temperatures. I figure Dr Porsche knows what he is doing.

[SV-3]

I'm afraid i take the view that Mr Toyota didn't spend millions on designing and testing our motorcar with an undertray so that we can bin it.

Have a similar problem with the Porsche 924, it has a fitted undertray which which directs air through the engine compartment, and eventually the fittings seize or break off and it gets binned, then people wonder why the get excessive underbonnet temperatures. I figure Dr Porsche knows what he is doing.

Absolutely

[Petrus]

I'm afraid i take the view that Mr Toyota didn't spend millions on designing and testing our motorcar with an undertray so that we can bin it.

Yes and no.
The manufacturer has a book full of legal regulations for homologation that not apply later. A major one is sound emission. Trays under the engine were first fitted to limit the sound bouncing from the road surface into the surroundings.
Have a look at the catalist and muffler. They will have cost a sweet sum to develop and they are very, véry good quality.  You can easily fit better flowing lighter ones though that still pass inspection because the norms for that inspection are a lot more permissive than those for initial homologation.
Back to the engine undertray there is no drive by periodic test at all!

Láter manufacturers understood the importance of under car airflow and the trays had that role too.
Yes and they are thus also part in directing the air flow through (or not) the engine bay.

In the case of the MR2, the rear nappy is most likely only for noise emission purposes and removing it likely to deminish lift at the rear and also cool the catalist which if anything lowers underhood temp.

The front part definitely also has a noise limiting role plus at higher speeds it will aid flow under the car but I cannot see it and the rear nappy having any role in directing air thróugh the engine bay. There is only a very small opening in the front one.

That the two keep dust and spray effectively out of the engine bay is strong pointer that they do nót direct extra air around the engine but keep it out!

If cooling would be your point, then you probably best remove both. Cooling is however not an issue with the ZZW30. Less still if you improve the flow of the exhaust.

[shnazzle]

There have definitely been indications that the undertray is an intricate part of the airflow management in the engine bay.

Whether it's true... Only Toyota knows

[scm2004red]

Thank you gentlemen, I have no doubt that design is an optimum depending on the circumstances and purpose to which the vehicle is intended to be used for, and I am sure nothing will stop the fitting of oversize wheels and the binning of an airbox in favour of a cone filter, all in the pursuit of an imagined improvement in speed or handling. Everyone likes to put their own stamp on things. For me, factory standard is best and I shall put it on my "to do" list.

[Ardent]

@scm2004red

Funny you should mention in takes.

If there is one thing that holds true on these cars. On a stock car, stock is best. Especially when it comes to things intakes. Hours and hours of reading should you wish. Fresh filter. Job done.
The take away. Stock is best. Cone filters and alike. Moving on nothing to see.

I also agree in principle re the nappy.
Deep down I trust Mr T. (Toyota) But,
I have ran with and without nappy. And can tell no difference whatsoever on any metric.

Edit.
You are right about wheels as well. Stock is best.
Only improvement to be had there is adding lightness.
The stock rim is hard to beat.

I try to keep mine as vanilla as I can.

[Bossworld]

Your biggest difficulty may be tracking down undertrays that are still in decent condition given the youngest are at least 14 years old, and as you've established, given the two schools of thought, there's healthy demand for them.

There've been a couple of posts on here where the material on the inside-facing part has burned, and many other people will be securing theirs on with cable ties.  Some of the mounting points can be drilled and retapped but you may also need some penny washers as the original points on the undertray have suffered damaged.

My mum's MR2 still has them and I curse my luck every time I have to do an oil change.  Mine doesn't have the rear-most two.

[Petrus]

I also agree in principle re the nappy.
Deep down I trust Mr T. (Toyota) But,
I have ran with and without nappy. And can tell no difference whatsoever on any metric.

TTE modded the front one on yours a bit so the intercooler got some more air.
If you think about it, this also higlights how little flow there is with both undertrays fitted.

The burn evidence does the rest imo. I took mine off because of this.
First the rear one as plant material collected there and heated up to the point of smoking.
Left the front one in following the OEM is good school of thought.

Found plant matter collected there too, albeit less. The fact it stayed put on the front tray even after a 140 km/h stint settled the matted concerning air flow for me.
Any air flow there is over the undertrays is limited and not worth a fire hazard.
Ok, literally not as hot an issue up north but it is illustrative for the air flow nonetheless.

Here a snapshot of the decat pipe which by chance shows some plant matter left áfter cleaning out. These lighweight thingies did not go anywhere. Hence my conclusion about the air flow.

I try to keep mine as vanilla as I can.

Jase, some will call that denial phase ;-)

That rimes so is true :-)

[Joesson]

@scm2004red
I also like to keep things generally standard. I confess the aerial does not go up and down at every opportunity, the "radio" is not OE there is a lack of precats and some fixings have been replaced with stainless steel.
As for the under trays that was one of my first jobs, replacing the cable ties with stainless hex had machine screws via penny washers into re tapped holes. If I remember correctly there are four screws on the mid section and four plastic clips. Next time I am under there I will try to remember to check and let you know.
As for replacement, maybe Mr T still offers them, likely costly but maybe worth asking. As you have done asking on here may have a result as some do discard them. Otherwise a specialist breaker such as Mr Dick Sloan may be able to help
Section on here MR2 Roadster Recycling (Dick Sloan)
      

[scm2004red]

Still bugged by not having any engine undertrays on my car, and can't work out whether I am missing 1, 2 or 3!
Has anyone any good pics or diagrams of what is actually under the rear of the car?

Thanks

[Ardent]

@scm2004red

Pm sent

[Littlebloke]

Both of my rear undertrays where missing when I bought my mr2 so I started searching on eday and found a pair that hadn't made reserve only 10 miles from where I live. The guy let me have them for £10 spent a couple of hour cleaning them and fitted this weekend. Had to use a couple of zip fasteners. I'm very pleased

[Joesson]

@Littlebloke
Sorry that I have not been under the car to count the fixings, but now you have "bargain" replacements you know how many.
Sounds like they were in better condition than mine, I had to fix mine  before I could  re fit  them.

[RubixRonnie]

Great thread, getting mine up on a ramp this week to check mine. I have a steep drive and get that awwwwwful scraping noise when getting it and and off the drive. Weird thing is it didn't used to do that when I owned it previously. Pressures are fine, have a feeling the trays have come loose and just need a cable tie or two!