MR2 Roadster Owners Club

The Workshop => Maintenance, Problems & Troubleshooting => Topic started by: treeroy on October 26, 2020, 09:54

Title: Is the exhaust guard needed?
Post by: treeroy on October 26, 2020, 09:54
I ended up taking the exhaust guard thing off while I was doing some stuff under the car yesterday. Is it actually necessary? Do I need to put it back on?
I assume it is to protect the exhaust from getting hit by stones?

Anyone had any issues with theirs off?

Thanks and happy Monday
Title: Re: Is the exhaust guard needed?
Post by: Joesson on October 26, 2020, 10:03
Quote from: treeroy on October 26, 2020, 09:54I ended up taking the exhaust guard thing off while I was doing some stuff under the car yesterday. Is it actually necessary? Do I need to put it back on?
I assume it is to protect the exhaust from getting hit by stones?

Anyone had any issues with theirs off?

Thanks and happy Monday


This is also known as the under tray, Nappy or perhaps can of worms because there is some discussion about this/ these items.
Some keep it in place, with OE fixings and or cable ties. Some run free and nappyless.
I believe it keeps the engine bay clean and does whatever MrT spent X000's of Yen developing and producing it for.
Title: Re: Is the exhaust guard needed?
Post by: thetyrant on October 26, 2020, 10:26
Ive left mine off for ease of access most of year, it does protect the engine from road crap to a degree but looks awful from the back as well as making access to engine for oil changes etc awkward, each to their own but i choose to leave it off at least in summer months, might refit for winter though.
Title: Re: Is the exhaust guard needed?
Post by: Petrus on October 26, 2020, 10:33
The primary function is preventing engine noise to reflect from the road towards onhearers. It is a measure to comply with noise regulation.

Secondly all under plastic plays an aerodynamic role; it makes the bottom flatter.

Air flow through the engine bay seems better without.

I took them off because they collected organic plant matter which was very close to igniting in close contact with the catalist.

As a bonus I could then fit a rudimentary, token diffuser which mostly looks better  ;D
Title: Re: Is the exhaust guard needed?
Post by: Chilli Girl on October 26, 2020, 11:05
One of our members nappy did actually catch fire, it was delhusband's wasn't it?  Foxy has hers still.
Title: Re: Is the exhaust guard needed?
Post by: Petrus on October 26, 2020, 12:10
Quote from: Chilli Girl on October 26, 2020, 11:05One of our members nappy did actually catch fire, it was delhusband's wasn't it? 

WOW!!! Did not know that. Could see that coming on mine though: The heat resistant fiber matt under the cat was charred so not rocket science to conclude that vegetable matter collected there  would sooner or later ignite.
Dry grass et all staying put there also made clear to me that there was hardly any air flow there.
Title: Re: Is the exhaust guard needed?
Post by: Carolyn on October 26, 2020, 12:25
I would also point out that the nappies don't seem to have protected subframes from demolition-by-rust.
Title: Re: Is the exhaust guard needed?
Post by: Ardent on October 26, 2020, 12:27
Certainly had mine smouldering at one point. Squeaky bum time.

Took it off after that never to be seen again.
Title: Re: Is the exhaust guard needed?
Post by: Petrus on October 26, 2020, 12:28
Quote from: Carolyn on October 26, 2020, 12:25I would also point out that the nappies don't seem to have protected subframes from demolition-by-rust.

Them stopping air flow will most likely have done/do the reverse.
Title: Re: Is the exhaust guard needed?
Post by: Petrus on October 26, 2020, 12:29
Quote from: Ardent on October 26, 2020, 12:27Certainly had mine smouldering at one point. Squeaky bum time.


A bit too ardent then :-)
Title: Re: Is the exhaust guard needed?
Post by: treeroy on October 26, 2020, 15:26
Thanks for the answers. Maybe I'll keep it off and throw it away.
Title: Re: Is the exhaust guard needed?
Post by: Joesson on October 26, 2020, 15:35
Quote from: treeroy on October 26, 2020, 15:26Thanks for the answers. Maybe I'll keep it off and throw it away.

But, even with the contra indications above there has been at least one recent request for said component in the wanted ads.
Title: Re: Is the exhaust guard needed?
Post by: Petrus on October 26, 2020, 17:15
If you have the space to stuff it somewhere than keep it. Otherwise put it up for sale. The little spyders are getting more rare and parts from breakers more so still.
Title: Re: Is the exhaust guard needed?
Post by: scm2004red on October 26, 2020, 22:32
Must confess when I bought mine it had no engine undertray and my first thought was to get a replacement. Most I have seen have damaged fixing points where they have been butchered off and the existing fixing lugs on mine aren't good, so I haven't pursued it. I am concerned however that there is no positive fixing  to the lower edge of the rear bumper which must act as an air brake at speed without the undertray aerodynamics and would flex alarmingly.
Title: Re: Is the exhaust guard needed?
Post by: treeroy on October 26, 2020, 23:33
Quote from: scm2004red on October 26, 2020, 22:32Must confess when I bought mine it had no engine undertray and my first thought was to get a replacement. Most I have seen have damaged fixing points where they have been butchered off and the existing fixing lugs on mine aren't good, so I haven't pursued it. I am concerned however that there is no positive fixing  to the lower edge of the rear bumper which must act as an air brake at speed without the undertray aerodynamics and would flex alarmingly.

I struggle to believe that your car will be slower just because of a piece of loose plastic trim at the back of the car... ?
Title: Re: Is the exhaust guard needed?
Post by: scm2004red on October 27, 2020, 07:27
The effect on speed wasn't the issue, although the aerodynamics will be adversely affected, it is the fact that there is a large area of of unsupported flexible plastic bumper flapping in a 70mph breeze!
Title: Re: Is the exhaust guard needed?
Post by: treeroy on October 27, 2020, 09:43
Quote from: scm2004red on October 27, 2020, 07:27The effect on speed wasn't the issue, although the aerodynamics will be adversely affected, it is the fact that there is a large area of of unsupported flexible plastic bumper flapping in a 70mph breeze!
The bumper is not "supported" by the exhaust guard. The exhaust guard is supported by the bumper.
Title: Re: Is the exhaust guard needed?
Post by: Petrus on October 27, 2020, 09:51
If anything the ´drag´ improves without the nappy and the rear bumper is sturdy enough to not ´flap about´.
Cutting out the mid section of the lower part of the bumper will improve mid range speed aero because of reducing lift. Marginally ofcourse, not like letting go of a parachute  :))
Title: Re: Is the exhaust guard needed?
Post by: scm2004red on October 27, 2020, 09:56
Not having an exhaust guard fitted it's difficult to comment, but something clearly attaches to the lower edge of the rear bumper which is no longer there on my car, and I would assume that same something attaches to the underside of the engine bay somewhere effectively bracing the lower edge of the bumper?
Title: Re: Is the exhaust guard needed?
Post by: Ardent on October 27, 2020, 18:28
Although not the actual lowest part of the  bumper.
There are 3 protrusions on the inside that use those pop in clips to fix it to the  crash bar.
The protrusions sit under the bottom edge of the bar.
Those plus the connection to the wheel arch liner keep it where it should be.
Title: Re: Is the exhaust guard needed?
Post by: scm2004red on October 27, 2020, 20:56
Quote from: Ardent on October 27, 2020, 18:28Although not the actual lowest part of the  bumper.
There are 3 protrusions on the inside that use those pop in clips to fix it to the  crash bar.
The protrusions sit under the bottom edge of the bar.
Those plus the connection to the wheel arch liner keep it where it should be.


Interesting, I assume you are referring to an impact bar behind the bumper, and the bottom of the bumper attaches to that?

Really don't recall seeing that, must stick my head underneath tomorrow and check.
Title: Re: Is the exhaust guard needed?
Post by: Ardent on October 27, 2020, 23:36
Will need to look a bit higher than the lower edge. Going from memory, much more centre line and below.
find the bottom of the crash bar and horizontal from there out to the bumper.
Title: Re: Is the exhaust guard needed?
Post by: scm2004red on October 28, 2020, 14:47
Yes, there are fixings higher up the bumper attaching it to the impact bar as I discovered when fitting a new O ring on the timing chain tensioner, still leaves the lower edge of the bumper on my car unsupported which annoys me a little.
Title: Re: Is the exhaust guard needed?
Post by: Bad Dog on November 26, 2020, 16:12
Quote from: Joesson on October 26, 2020, 10:03
Quote from: treeroy on October 26, 2020, 09:54I ended up taking the exhaust guard thing off while I was doing some stuff under the car yesterday. Is it actually necessary? Do I need to put it back on?
I assume it is to protect the exhaust from getting hit by stones?

Anyone had any issues with theirs off?

Thanks and happy Monday


This is also known as the under tray, Nappy or perhaps can of worms because there is some discussion about this/ these items.
Some keep it in place, with OE fixings and or cable ties. Some run free and nappyless.
I believe it keeps the engine bay clean and does whatever MrT spent X000's of Yen developing and producing it for.


Nappyless 😂
Title: Re: Is the exhaust guard needed?
Post by: Ardent on November 26, 2020, 17:59
Nappyless. Topless. We do it all.
Title: Re: Is the exhaust guard needed?
Post by: Petrus on November 26, 2020, 19:33
Don´t get me started  O:-)  O:-)
Title: Re: Is the exhaust guard needed?
Post by: Ardent on November 26, 2020, 21:38
 ;)