Rear bumper cut to aid cooling

JB21 · July 31, 2020, 12:50

Think of cutting the lower part of my rear bumper and removing the grills, similar to the below. I'm looking at ways to reduce engine bay temps as they kill power and are generally not good for reliable running on track.

Anyone done this?

You cannot view this attachment.

You cannot view this attachment.

Extreme bumper cut

You cannot view this attachment.

Petrus · July 31, 2020, 16:01

It should work.

It should also reduces lift at the rear.

Gaz2405 · July 31, 2020, 18:23

I've done mine, I'll dig out some pictures.

Or find me on insta onemanandhisbike

No noticeable difference but no proper back to back testing either, primarily done it for reduced lift and drag.

You cannot view this attachment.

Joesson · July 31, 2020, 19:26

Quote from: JB21 on July 31, 2020, 12:50Think of cutting the lower part of my rear bumper and removing the grills, similar to the below. I'm looking at ways to reduce engine bay temps as they kill power and are generally not good for reliable running on track.

Anyone done this?

You cannot view this attachment.

You cannot view this attachment.

Extreme bumper cut

You cannot view this attachment.

Possibly not the best "look", unfortunate for the other drivers as that is all they will be seeing!

househead · July 31, 2020, 19:34

Quote from: Joesson on July 31, 2020, 19:26Possibly not the best "look", unfortunate for the other drivers as that is all they will be seeing!

This was my first feeling and I almost posted as much but talked myself out of it since JB21 is running a track car and maybe doesn't care. If my car had this, I'd cry

I expect it will help with cooling the engine bay though.

Gaz2405 · July 31, 2020, 20:13

Quote from: househead on July 31, 2020, 19:34
Quote from: Joesson on July 31, 2020, 19:26Possibly not the best "look", unfortunate for the other drivers as that is all they will be seeing!

This was my first feeling and I almost posted as much but talked myself out of it since JB21 is running a track car and maybe doesn't care. If my car had this, I'd cry I expect it will help with cooling the engine bay though.

100% with you here, if mine wasn't a track car it wouldn't have it.

Karthoum · August 7, 2020, 03:41

Funny how the discussion went towards this being track only,

my previous daily had the bumper cut a week into ownership and it looked great with a centre exit exhaust (not pictured unfortunately).

m1tch · August 7, 2020, 09:36

Think its done mainly for aero, especially if not running a nappy etc, still undecided on it as the rear crash bar blocks a lot of the space back there, good if you have an odd exhaust though.

Perhaps do some logging runs with a temp probe with it standard and then just remove the grill inserts to see if it makes much difference.

Also be aware that for air to flow it goes from a high pressure to a low pressure, although we do have side vents which help.

Gregmorse · August 8, 2020, 14:03

Sometimes this can mess with airflow, for example on my MK2 turbo, I installed the "scoops" for the engine bay, however they forced air down into the engine bay and the way the car's designed is for the hot air to leave through the top. Think it wouldnt be the same kinda issue here but maybe.

Karthoum · August 8, 2020, 20:52

Quote from: m1tch on August 7, 2020, 09:36still undecided on it as the rear crash bar blocks a lot of the space back there, good if you have an odd exhaust though.

The crash bar affects the heat more than that tiny piece of bumper (at least for me), the inserts are still behind the crash bar so it will be hot after a run, mostly from the exhaust. I would do this again to my newer MR2 only if I got/made a custom lighter crash bar with a lot of free space for air to go through.

I wish I could reply to you about the temperature differences but I also removed all the thin metal shielding that's near the rear bumper so it wouldn't be an accurate measure.