DPE with aero on Miata - modulus inside

Hi, I'm Marcus and I drive a miata.



I recently started a new position with Nine Lives Racing, customer service/web admin/spellchecker/etc as well.


Soon after, ok immediately after, starting with 9LR we got to work on aero onto my TTE(TT6) NB. Converting it to TT5 a week before the next event with NASA-SE at Roebling Road. Opted for the 64" Swan-Neck Big Wang, because Johnny said so.

Also installed the 9LR prototype air-dam along with a DiY 3" splitter out of alumalite. Big Wang install was a breeze, air-dam and ducting isn't optimal but it certainly made a difference.

The mouth turned out to be too small for drafting. Car crept up to 3/4 on OEM temp gauge while drafting for 1/4 of a lap(2.2mile course) while it was slight over-cast and ~75* ambient. My miata has 37mm Koyo v-core and Qmax reroute. Ducting would resolve this problem while in a draft with this size of an opening, IMO.

The car gained 5hp, lost ~140lbs, and added this aero package since the last time I was at Roebling.
Previous times in TTE trim of 130rwhp, 2440lbs,Xida800/500,RB1.125"/14mm, 205 R7s, 15x9s - 1:21.7xx - 1:23.0xx 
New times in TT5 trim of 135rwhp, 2300lbs, Xida800/500,RB1.125"/14mm, 205 R7s, 15x8s - 1:19.4xx - 1:21.7xx

The largest difference with this aero both my co-driver and I noticed was how settled it was on a slip-angle. It required smaller inputs to correct to squiggle through. Unfortunately, I was not running AiM data two years when I was at Roebling last :(

This comparison actually does a decent job of showing the difference of inputs:
http://youtubedoubler.com/?video1=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dx76iDNfEpZE&start1=4&video2=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DJHhr1Rma5Zw&start2=51&authorName=why+we+slap

Very cool! What’s the advantage of a swan neck vs. a regular wing? 

Less disturbance to the bottom (crucial) surface of the wing. Also Le Mans cars use them ;) But the difference is pretty significant. 

Yeah, like Keith said less disturbance which generates faster air beneath the wing = more down-force. The only extra drag on this setup is the extra height of the mounts, which is about 6" higher. Although the extra down-force certainly surpasses the drag from the taller mounts.

Next goal for aero is to properly duct the front-end, which will lead to more front down-force. I'm also going to try out our gurney flaps . Planning to gather some data on them at Road Atlanta in June. The miata has the TTE record there, 1:42.4xx, along with several other events with data at the current power. So seeing the difference of aero there will be pretty cool.

Cool! Do you have any mph/lbs of downforce data on the wing? (Would be interesting to see data with swan mounts vs under mounts).

I've recently made a homemade wing and I'm planning to test mine within in a couple weeks.

I know laps times data are king, but do you also try to collect stuff like pressures and wool Tufts and coast down drag data?

In reply to Robbie :

NineLivesRacing has some data on their site... I don’t recall for what size wing, nor the mounting.  But, the fact that it’s out there is refreshing.  I haven’t gone bombing around trying to figure out what section they’re using, and if coordinates are out there anywhere.  But, it looks like (off hand guessing) that their camber is around 10% without a gurney flap.

Marcus_NineLivesRacing said:

Yeah, like Keith said less disturbance which generates faster air beneath the wing = more down-force. The only extra drag on this setup is the extra height of the mounts, which is about 6" higher. Although the extra down-force certainly surpasses the drag from the taller mounts.

Next goal for aero is to properly duct the front-end, which will lead to more front down-force. I'm also going to try out our gurney flaps . Planning to gather some data on them at Road Atlanta in June. The miata has the TTE record there, 1:42.4xx, along with several other events with data at the current power. So seeing the difference of aero there will be pretty cool.

By “fully ducting” you mean from the new air dam, to the radiator, and from the backside of the radiator to the hood vents, right?  Otherwise, I expect that keeping air from getting between the air dam and the OEM bumper cover will help you realize some cooling efficiency gains.

Not knowing what/if the SCCA TT rules have for limitations.  Have y’all done any investigation on the shape of the air dam leading from the splitter to the radiator?  I realize there’s a certain aero “zeitgeist” to throwing as big an airdam on top of the splitter as possible with a sharp edge to duct to the rad, in order to “capture” as much high pressure on the top side of the splitter, while make a clean cut for the air directed at the rad.  But, it looks like doing this might be artificially limiting your effective area, compared to extracting some vertical momentum from that flow on the way to the radiator?

Robbie said:

Cool! Do you have any mph/lbs of downforce data on the wing? (Would be interesting to see data with swan mounts vs under mounts).

I've recently made a homemade wing and I'm planning to test mine within in a couple weeks.

I know laps times data are king, but do you also try to collect stuff like pressures and wool Tufts and coast down drag data?

Yes we do have CFD testing on the wing! Keeping in mind this was tested in open air, so not accounting for different mounts. https://9livesracing.com/cfd-testing

For the front aero I used this article as a rough estimate. https://hanchagroup.wordpress.com/2013/01/29/splitter-or-air-dam-which-design-is-best/

Hopefully we can have CFD testing on multiple chassis using 3D models in the near future.

sleepyhead said:

Marcus_NineLivesRacing said:

Yeah, like Keith said less disturbance which generates faster air beneath the wing = more down-force. The only extra drag on this setup is the extra height of the mounts, which is about 6" higher. Although the extra down-force certainly surpasses the drag from the taller mounts.

Next goal for aero is to properly duct the front-end, which will lead to more front down-force. I'm also going to try out our gurney flaps . Planning to gather some data on them at Road Atlanta in June. The miata has the TTE record there, 1:42.4xx, along with several other events with data at the current power. So seeing the difference of aero there will be pretty cool.

By “fully ducting” you mean from the new air dam, to the radiator, and from the backside of the radiator to the hood vents, right?  Otherwise, I expect that keeping air from getting between the air dam and the OEM bumper cover will help you realize some cooling efficiency gains.

Not knowing what/if the SCCA TT rules have for limitations.  Have y’all done any investigation on the shape of the air dam leading from the splitter to the radiator?  I realize there’s a certain aero “zeitgeist” to throwing as big an airdam on top of the splitter as possible with a sharp edge to duct to the rad, in order to “capture” as much high pressure on the top side of the splitter, while make a clean cut for the air directed at the rad.  But, it looks like doing this might be artificially limiting your effective area, compared to extracting some vertical momentum from that flow on the way to the radiator?

Initially, ducting from the air-dam to the radiator opening. Unsure if I'll dive that deep into adding ducting from the backside into the vents. Good authority has told me the majority of the front drag, say ~70%, is from the radiator. Any low-hanging fruit to help reduce that drag and I'm game.

NASA has a rule of the airdam cannot be sloped anymore than 5*. However, it's fine to angle ducting in any fashion I want past the air-dam and/or car silhouette. Also, I did a 3" splitter instead of a 4" so I could comply with GLTC rules. 

In reply to Marcus_NineLivesRacing & airdams:

gotcha, as ever "there's a rule for that"