The Roadster NA Journey Begins

sailaholic · Postby **sailaholic** » Mon Jul 25, 2016 9:32 am

Centre exit exhaust through the boot ala Dannys NC?

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corners · Postby **corners** » Mon Jul 25, 2016 9:37 am

I was only just thinking of that!

Trackphotos · Postby **Trackphotos** » Mon Jul 25, 2016 9:53 am

Isn't the sweet spot for rear diffusers supposed to be around 7 degrees? One of those counterintuitive things where it needs to look less functional for it to work better?

Magpie · Postby **Magpie** » Mon Jul 25, 2016 10:37 am

sailaholic wrote:Centre exit exhaust through the boot ala Dannys NC?

That is the plan, need to be careful of the material used for the diffuser... There is also some interesting theory about F1 cars that used the exhaust gas into the rear diffuser hence why the practice is now banned.

Trackphotos wrote:Isn't the sweet spot for rear diffusers supposed to be around 7 degrees? One of those counterintuitive things where it needs to look less functional for it to work better?

Yes and no

The best angle is when the airflow stays attached to the diffuser, hence why I plan to make it adjustable. There is some work on the web that suggests about 11° for the MX5, however the angle is also dependant on other aero fitted like wing/underbody and ride height. http://www.rtheorymotorsports.com/blog/2015/9/19/september-19th-2015-miata-rear-diffuser-cfd-analysis

I was surprised at the final angle, however I could have done the math first and worked it out

Anyway I will get out the differential pressure meter and do some testing to see what is the best angle. I may fix up the rear bumper so that I can do the testing on my car before I cut my car's bumper.

Magpie · Postby **Magpie** » Sun Jul 31, 2016 6:36 pm

Spent the Saturday redoing the angle of the diffuser, it is now at 12°. Next weekend is cutting the template for the sheet metal for the diffuser. will also be contemplating getting the air out from the rear wheel arches. Heaps of room now to bring the exhaust out above the diffuser.

DSCN3364 by Eipeip, on Flickr

DSCN3366 by Eipeip, on Flickr

DSCN3368 by Eipeip, on Flickr

DSCN3365 by Eipeip, on Flickr

Magpie · Postby **Magpie** » Sat Aug 20, 2016 5:56 pm

General Practice at QR today. No records broken, heaps of oil from the happy laps so the early part of the day was more driving on ice than anything. Had a scare (so did Trackphotos as he was driving) when the oil dipstick worked its way out and started spilling oil onto the exhaust and creating a smoke screen. I thought it was a diff seal again, but lucky it was just oil out of the dipstick. Will be cable tied in future.

Trackphotos jumped in for a few laps and has provided some good feedback to be considered. Lucky for me he had traffic...

Trackphotos - red lines
Me - blue lines

Lap Compare by Eipeip, on Flickr

T6

T6 by Eipeip, on Flickr

T3

T3 by Eipeip, on Flickr

T1,2,4,5

T1-2-4-5 by Eipeip, on Flickr

Trackphoto's lap

My lap

Test video for combing laps.

Magpie · Postby **Magpie** » Sat Aug 20, 2016 7:11 pm

Last video did not upload so here its is

Trackphotos · Postby **Trackphotos** » Sat Aug 20, 2016 7:47 pm

Was a lot of fun

shame about the traffic, always expected with general practice though.

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Magpie · Postby **Magpie** » Sun Aug 28, 2016 3:30 pm

Quite weekend doing some odd tasks, rear diffuser on hold till after WTAC (46 days to go).

Saturday was bike day, rebuild carbs and balance (exhaust fan came in handy Lokiel)

IMG_1452[1] by Eipeip, on Flickr

Should have the fairing back soon

IMG_1456[1] by Eipeip, on Flickr

Sunday was MX5 day.
Rear brake pads are fine, will however swap the W6.5's in soon to see how they go.

Had some air tabs sitting around in a drawer since 2012 so decided to paint/mount them to see if they really do work. Since lowering the wing by one riser the car actually posted faster lap times, but again it could just be me improving as a driver.

IMG_1453[1] by Eipeip, on Flickr

IMG_1455[1] by Eipeip, on Flickr

Also thinking about a change to the exhaust...

IMG_1454[1] by Eipeip, on Flickr

speed · Postby **speed** » Sun Aug 28, 2016 5:32 pm

What are those air tab things? Look like my dust pan.

Centre exit exhaust for WTAC?

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MattR · Postby **MattR** » Sun Aug 28, 2016 6:44 pm

I think they are there to create more drag to slow the car down........

Personally Mark, don't worry about hanging more sh*t off the car to create drag and what not, just get out there and drive it until YOU can't go any faster and then you can start to play with it to make the most of what you have.

Magpie · Postby **Magpie** » Sun Aug 28, 2016 7:19 pm

Speed
1. They do look like small dust pans. They are vortex generators and are supposed to reduce drag.
2. Not centre exit

However the muffler maybe replaced with a straight through. The racing beat weights in at about 8kg.

MattR
3. Refer to point 1

4. That is what I have been doing, just driving and not playing

the air tabs are easy to remove anyway. Still have a few more general practices to do and street sprints at QR before I leave for Sydney.

MJT_MX5 · Postby **MJT_MX5** » Sun Aug 28, 2016 7:48 pm

What did you think of the racing beat exhaust?
Currently thinking about one for mine, need something thats not too loud for daily driving.

Magpie · Postby **Magpie** » Sun Aug 28, 2016 7:57 pm

No problems with the racing beat, nice sound and no drone. Will be putting the racing beat on when the car is dríven on the road, unless the replacement one is within legal noise limits.