Do you happen to have a link to the thread where this was discussed? I can't find it and it must have been discussed while I wasn't present in the Miata community.

 

https://www.miataturbo.net/race-prep...results-80176/

 

Theres another one somewhere it was posted here an club ricer. Of course here had like actual discourse across multiple pages and on CR it was just everyone trying to justify that their bumper cut looked cool enough that the extra drag didnt matter.

 

Well, I'm glad I didn't cut my bumper today!

 

Two birds with one stone today, improved fender aero and weight loss. A single straight line cut with the angle grinder worked wonders.
I hid the ugly underside with matte black paint, but there is still a gaping hole into the front of the door which I don't much like.
I suppose eventually I'll have to make something to fill the void much like Moti did on his blackbird car(s).

 

So I went out today and tried a test with a bumper and without. This test was done on the road, in my 93, 1.6 powered car. I first went out on a nearby road and made 2 runs in each direction, then came back home, removed the complete bumper, and went back out, I even went so far as to fill up with fuel at the exact same pump between runs, it was .85 gallons if anyone cares. I again made 2 runs in each direction. The road is pretty flat and dead straight where I went. Though you can definitely make out 2 distinct lines for each so it's not perfectly flat, and there may have been a little wind, but not too bad.

I simply removed the complete bumper, I did weigh it and all the hardware I left off between runs, and it was 19lb 5oz, which was more than I was expecting. Also of note I have the mud flaps on the rear, so this would theoretically represent the worst case for bumper drag.

Green = bumper
Purple = no bumper

I don't think there is any difference in aero drag to speak of. You might talk me into thinking the 20lb weight savings is showing up at the lower speeds, maybe.

One other note, for some reason the accelerometer calibration got messed up between runs, so this graph was done using the GPS longitudinal acceleration channel multiplied by 9.8. So the units would be m/s/s.

 

MrJon,

Thanks for sharing. Repeatable controlled data gives me a woody. Agree with your conclusion. Values for A and B both fall well within the noise of the test.

 

THIS is the reason to remove the bumper if there is no requirement/need for it.

 

Wait, there's 20 pounds in the bumper, bumper support and hardware? I thought they were like ~5 pounds together. That's reason enough imo.

 

Almost 25 lbs including the bottom horns.

It all adds up before you know it and you've got a caged/hardtop/turbo 1990 with wing/splitter sitting at 2055lbs with half tank.

 

"I won because my rear bumper was still on"

- No one, ever.

 

Interesting, so let's say my TA class allows me to remove my bumper. Would you guys do it without thought? Or does there need to be consideration about making the weight distribution even worse? This is on a singular winged car btw.

 

Weight reduction > weight distribution, make that bumper go away.

 

That I can do. Thanks for the guidance!

 

Bumper delete was the most important thing we did to Bullet.

 

Important, yes.
But more important than installing Creampuff's end plates and my BRAND NEW 245 A7's?

 

Tongue firmly in cheek.

 

Finally decided to put the car on the scales again, and it would appear that the car has lost 21 kgs since June 2017, so this goes some way to explain the increase in acceleration. Since July 2013 the car has lost 84kg

WTAC Clubsprint lists the NA6 as 940kg, however mine is 995kg (sans driver). However being NA the car can go to 804kg, so 195kg to go! Not sure where I will find this!

Weight savings planned:
1. Hardtop swap. The OEM is said to be about 25kg (will check mine soon soon). Have one to go on the weights is at 14.1kg. So approximately 11 kgs saved.
2. Heated windscreen. This will allow the HVAC to be removed (fan, heater core etc), 5.83kg saved (HVAC control 0.540, ducts 0.398, fan 2.029 and heater core 2.863).
3. Driver 20kgs...

 

I weighed my hardtop a while back and it was about 42ish lbs, it was within 1 or 2 pounds of the soft top. My hardtop doesn't have a liner or defrost.

 

14.1 is still a bit heavy for a hardtop. The carbon fibre ones I made weighed about 6kg's complete. The new moulds are being made now, and some lightweight fibreglass ones will be ready in a month or so.plan to get them under 10kg's.