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C7 Aero Balance with GM Aero

 
Old 07-10-2019, 01:55 PM
  #1  
wings19
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Default C7 Aero Balance with GM Aero

New to Corvette here but have been sifting through as much info as I can. Have a 17 GS with Stage 3 aero.

Regarding GM offered aero I'm looking for some data on aero balance on the Z06 and GS. I understand the power difference between the two but for cornering balance they should be equal enough. For larger, faster tracks I'm interested to know what has been learned regarding power vs. drag of the different aeros kits on the GS.

For this conversation let's take a look at my two main tracks:
  • MSR Houston - 2.38mi club track, fairly technical, 4 straights where I can get up to 125-130.
  • COTA - Y'all know COTA... F1 track, faster, longer straights.
As I have the Stage 3 aero bits I'm looking for insight on the best config for each scenario from experience or other empirical data. For the front aero I'd rather not switch back and forth between stage 2 and 3 winglets as they're a bit of a pain but I'm open to sticking with one or the other. For the rear I can obviously adjust the clear wicker or take it off easily if it makes sense.

Thoughts?

Last edited by wings19; 07-10-2019 at 01:57 PM.
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Old 07-10-2019, 02:20 PM
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your over thinking it.

factory front aero doenst produce enough drag to be of any concern.

get out there and just drive.
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Old 07-10-2019, 02:44 PM
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Originally Posted by STANG KILLA SS View Post
your over thinking it.

factory front aero doenst produce enough drag to be of any concern.
I appreciate your sentiment but "overthinking it" is part of the fun for me. I do go out and drive, let's also have a discussion about the aero bits That's what forums are for, right? It's for us track rats who are stuck in the office wishing we could be at the track but can't so we talk about it instead.

When you reach a certain level in your driving ability you also need the car to work with you and small changes make a difference, hence this discussion. I'm curious to know if any of the more advanced guys have done any testing between the aero sets. GM claims the aero is functional and I've heard downforce numbers so surely they have some affect. If nothing else I'll do some of my own testing at MSR and see what the numbers show and my seat of the pants feel is. If I can come up with a front/rear combo that give me a couple 10th's I'll take it.

On your second comment, is this based on any data?

Last edited by wings19; 07-10-2019 at 02:46 PM.
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Old 07-10-2019, 03:53 PM
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So GM thinks stage 3 is too much for the power of a GS. Maybe it is. I know that my Stage2 stuff hits a wall at about 145, and imagine the center part of the rear to make a 3 back there wouldn't help. Front grip is not generally lacking in these with a track setup on camber. But if you are trying to run a more street setup, then you might want the extra grip the stage 3 stuff in front can give.

So, I submit you get the Stage3 stuff, and if you want to, or try to remove the rear extra for COTA and see what happens to lap times overall, and balance. And at MSR Houston, run run the full kit. And no, I don't think removing the center rear part will cause a diabolically loose mess, the majority of the downforce comes from the outside spoilers which you can see when the car is dirty by the airflow.
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Old 07-10-2019, 07:10 PM
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I once did some testing with my C7 Z06 with the stage 3 front aero and no rear wicker (effectively stage 1) and it was noticeably loose and downright scary in fast corners like T3 and T10 at Summit Point but I didn't see much improvement in VMAX on the straights. I'm with Sam that stage 2 rear should be fine with the stage 3 front though. I believe it was Jim Mero that said that the stage 3 aero was too much for the GS, even at the ring which was a track that really benefits from extra downforce, honestly the crappy 5th gear on the GS probably exacerbates the problem.

Currently I'm running the ZR1 wing with the stage 3 front splitter on my GS and the aero balance has been very good at the low wing angle. With it I'm able to hit a GPS verified 150 MPH on the back straight at VIR with stock power.

There are downforce and drag numbers posted in one of the Ask Tadge answers but they don't get in to front vs rear and the numbers are for the entire car, there was also a slide from one of the bash presentations that someone posted. I took the DF numbers I could find and made a math channel to demonstrate the effect on Df with speed in this thread over here - https://www.corvetteforum.com/forums...downforce.html

Below are my rough notes that I used to create that.

Downforce at 150 MPH
Z06 Stage 1 = +41.9 lbs (lift)
Z06 Stage 2 = -187.1 lbs
Z06 Stage 3 = -343.5 lbs
ZR1 ZTK = -524 lbs
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Old 07-10-2019, 07:46 PM
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Thanks for the responses, gents, very helpful.

I had a fitment issue with the front winglets and I'm going back to Corvette World tomorrow as they have a new set to try. This is my opportunity to basically return the front winglets.

After looking through Tadge's post and putting all of this together I'm thinking it may be best to just stick with the Stage 2 kit (small winglets, large rear end plates but no clear wicker). I've always been of the belief that for sports cars, companies dump a bunch of R&D into the design of the car and it's all for a reason. If they don't offer Stage 3 with the GS it must be for a reason but then again, on a track like MSR Houston all of that aero may benefit but where is the break even point of power/drag on this car?

The other option is to keep all the parts and get out to do some back to back testing with PDR data.
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Old 07-10-2019, 08:02 PM
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Originally Posted by Poor-sha View Post
I once did some testing with my C7 Z06 with the stage 3 front aero and no rear wicker (effectively stage 1) and it was noticeably loose and downright scary in fast corners like T3 and T10 at Summit Point but I didn't see much improvement in VMAX on the straights. I'm with Sam that stage 2 rear should be fine with the stage 3 front though. I believe it was Jim Mero that said that the stage 3 aero was too much for the GS, even at the ring which was a track that really benefits from extra downforce, honestly the crappy 5th gear on the GS probably exacerbates the problem.

Currently I'm running the ZR1 wing with the stage 3 front splitter on my GS and the aero balance has been very good at the low wing angle. With it I'm able to hit a GPS verified 150 MPH on the back straight at VIR with stock power.

There are downforce and drag numbers posted in one of the Ask Tadge answers but they don't get in to front vs rear and the numbers are for the entire car, there was also a slide from one of the bash presentations that someone posted. I took the DF numbers I could find and made a math channel to demonstrate the effect on Df with speed in this thread over here - https://www.corvetteforum.com/forums...downforce.html

Below are my rough notes that I used to create that.

Downforce at 150 MPH
Z06 Stage 1 = +41.9 lbs (lift)
Z06 Stage 2 = -187.1 lbs
Z06 Stage 3 = -343.5 lbs
ZR1 ZTK = -524 lbs
This is interesting info.

As a side note, I'll be at Auto Club Speedway this weekend. My GS is an FE6 car but with full OEM GS Stage 3 aero....aka it lacks the center wicker on the rear spoiler but has everything else including the front canards and undertray. Conversely, my buddy will be there in his GS that's an FE7 car but with Stage 1 aero. We're equivalent drivers but this will be the first time at this track at the same time with these cars so I'm looking forward to seeing how the cars compare. I expect him to be faster than me on the long NASCAR straight but slower on the banked turn and the high speed chicanes. Obviously with the CCB he'll out-brake me.
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Old 07-10-2019, 09:19 PM
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It will be interesting to see how you guys get on.

You should do a coast-down test on the way to/from the track. I believe the various stages of aero produce downforce increasingly but now I'm starting to wonder if stage 3 really is too much for the GS...
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Old 07-10-2019, 10:11 PM
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Originally Posted by Poor-sha View Post
I once did some testing with my C7 Z06 with the stage 3 front aero and no rear wicker (effectively stage 1) and it was noticeably loose and downright scary in fast corners like T3 and T10 at Summit Point but I didn't see much improvement in VMAX on the straights. I'm with Sam that stage 2 rear should be fine with the stage 3 front though. I believe it was Jim Mero that said that the stage 3 aero was too much for the GS, even at the ring which was a track that really benefits from extra downforce, honestly the crappy 5th gear on the GS probably exacerbates the problem.

Currently I'm running the ZR1 wing with the stage 3 front splitter on my GS and the aero balance has been very good at the low wing angle. With it I'm able to hit a GPS verified 150 MPH on the back straight at VIR with stock power.

There are downforce and drag numbers posted in one of the Ask Tadge answers but they don't get in to front vs rear and the numbers are for the entire car, there was also a slide from one of the bash presentations that someone posted. I took the DF numbers I could find and made a math channel to demonstrate the effect on Df with speed in this thread over here - https://www.corvetteforum.com/forums...downforce.html

Below are my rough notes that I used to create that.

Downforce at 150 MPH
Z06 Stage 1 = +41.9 lbs (lift)
Z06 Stage 2 = -187.1 lbs
Z06 Stage 3 = -343.5 lbs
ZR1 ZTK = -524 lbs
I posted in Poor-shaís related thread linked above but Iíll post here also.
Looking at the 187.1 and 343.5 lbs of downforce for stage 2&3, how do these numbers result in increased grip. The end goal is to go faster through the turns. Doing that requires us running higher Gs. To increase the capability of our cars to increase Gs we use better, softer tires and downforce. Which is more efficient?
343.5 sounds like a lot but itís roughly 86lbs of downforce at 75 mph - assuming the downforce drops squared relative to speed. The stage 2 drops to roughly 47 lbs. So a 39 lb difference in downforce between stage 2 & 3 at 75 mph. With a 3600 lb car(and driver) isnít that just over .01Gs? Seems like nothing compared to tire improvements.
Thoughts? This is a little over my head, but very interesting.
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Old 07-11-2019, 12:45 AM
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Originally Posted by fatsport View Post
I posted in Poor-shaís related thread linked above but Iíll post here also.
Looking at the 187.1 and 343.5 lbs of downforce for stage 2&3, how do these numbers result in increased grip. The end goal is to go faster through the turns. Doing that requires us running higher Gs. To increase the capability of our cars to increase Gs we use better, softer tires and downforce. Which is more efficient?
343.5 sounds like a lot but itís roughly 86lbs of downforce at 75 mph - assuming the downforce drops squared relative to speed. The stage 2 drops to roughly 47 lbs. So a 39 lb difference in downforce between stage 2 & 3 at 75 mph. With a 3600 lb car(and driver) isnít that just over .01Gs? Seems like nothing compared to tire improvements.
Thoughts? This is a little over my head, but very interesting.
What the above does is highlight the impact of the actual track. For instance, at Streets of Willow, even on the front straight, top speed for me will be in the 105-110mph range, there's another straight that's upper 90s/low 100s, and most of the ~14 turns are 60mph or significantly less. Downforce simply isn't going to matter that much. Conversely, at Auto Club Speedway I enter Turn 1 at ~150mph, apex at ~125, and then accelerate to ~130. There are multiple other areas on the track where corner entry is in excess of 100mph. Here, downforce does matter, at least in my opinion. Is it as much as tires? Don't know but I do think if the car feels a bit more planted/stable, that by definition gives the driver added confidence vs a car that feels light and on edge due to lift. An interesting and complicated topic!
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Old 07-11-2019, 01:07 PM
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Op,

what are your lap times at each? MSRH CW/CCW & COTA?

"stage 3" is by no means to much for any C7 corvette. It's not enough... period. losing a couple mph on the straights pales in comparison to the amount of speed real aero enables you to carry through turns 2,3,4,5,6,7,8,9,15,16,17,18 and 19 at COTA and T1, 2,3,6,7,11,13,14,15,16,17 at MSRH

FWIW my car at cota with just regular Z51 aero would hit 153 with a good corner exit off of T11 and with full aero I'm bouncing on the rev limiter in 4th at 144mph down the straight. It's STILL faster to be slower on the straight.
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Old 07-11-2019, 02:26 PM
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Originally Posted by Poor-sha View Post
I
Currently I'm running the ZR1 wing with the stage 3 front splitter on my GS and the aero balance has been very good at the low wing angle.

Downforce at 150 MPH
Z06 Stage 3 = -343.5 lbs
ZR1 ZTK = -524 lbs
Poor-sha, how do you think this is possible? Shouldn't the car understeer?
Only possible explanation I can think of is the 524 lbs of ZR1 downforce was measured with the wing at the higher angle. This would significantly increase drag though.

Last edited by fatsport; 07-11-2019 at 04:19 PM.
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Old 07-11-2019, 07:46 PM
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Originally Posted by fatsport View Post
Poor-sha, how do you think this is possible? Shouldn't the car understeer?
Only possible explanation I can think of is the 524 lbs of ZR1 downforce was measured with the wing at the higher angle. This would significantly increase drag though.
I'm a bit surprised myself but it might be helpful to look at the numbers at 80 MPH which is about where you enter most fast sweepers.
Df at 80 MPH.

S1 - +11.9
S2 - -53.2
S3 - -97.7
ZTK - -149

At that speed the ZTK is making ~ 50 lbs more of downforce and theoretically that is balanced front to rear so let's call it 25 lbs on the rear. The amount and the balance is also going to be heavily affected by ride height, rake, and whether you are neutral, braking, or on the throttle. In the end I think it ends up pretty close and even entering the esses at VIR at ~130 MPH I can't say I felt aero understeer. If anything, I thought my ZR1 had a push at high speed even in the low wing position so I'm surprised the GS actually feels better.

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Old 07-11-2019, 10:50 PM
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Originally Posted by lobsterroboto View Post
Op,

what are your lap times at each? MSRH CW/CCW & COTA?


I got the car 4 weeks ago so I haven't been to COTA with the Vette. I'm coming from a stock 2016 GTR. With that I ran 2:24 at COTA (first and only time out there so far) and 1:44 in both directions at MSR on cheap Kuhmo street tires.

I think the Vette will be faster around MSR - I am brand new to the manual trans/RWD platform. However, last weekend I went out and did a couple of CW runs. The car is currently on street alignment, MPSS run-flats, DOT3 brake fluid, and stock pads. Due to the brakes I was doing about a 6/10ths effort and still pulled off a 1:45.65 with coasting, nowhere near threshold braking, and not pushing too hard in and out of the corners as I'm still getting the feel for the car which is encouraging. I had the stage 2 front end with stage 3 rear spoiler. I wasn't going hard enough to feel any imbalance but it felt good overall.

Next steps for me is definitely brake fluid and pads along with stickier tires and track alignment. I think I'm going to run the Stage 2 setup and feel it out. I can always bolt on the front or rear bits as needed. I spend a fair amount of time at MSRH so I should be able to do some testing.

As for tires I'm finding it difficult to find options, looks like Cup 2's are about it for stock sizes?
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Old 07-11-2019, 11:31 PM
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Originally Posted by wings19 View Post

I got the car 4 weeks ago so I haven't been to COTA with the Vette. I'm coming from a stock 2016 GTR. With that I ran 2:24 at COTA (first and only time out there so far) and 1:44 in both directions at MSR on cheap Kuhmo street tires.

I think the Vette will be faster around MSR - I am brand new to the manual trans/RWD platform. However, last weekend I went out and did a couple of CW runs. The car is currently on street alignment, MPSS run-flats, DOT3 brake fluid, and stock pads. Due to the brakes I was doing about a 6/10ths effort and still pulled off a 1:45.65 with coasting, nowhere near threshold braking, and not pushing too hard in and out of the corners as I'm still getting the feel for the car which is encouraging. I had the stage 2 front end with stage 3 rear spoiler. I wasn't going hard enough to feel any imbalance but it felt good overall.

Next steps for me is definitely brake fluid and pads along with stickier tires and track alignment. I think I'm going to run the Stage 2 setup and feel it out. I can always bolt on the front or rear bits as needed. I spend a fair amount of time at MSRH so I should be able to do some testing.

As for tires I'm finding it difficult to find options, looks like Cup 2's are about it for stock sizes?
Iím over here with poverty z51 I have no idea what tires fit a GS stock wheels I would move to 18ís ASAP tho.

Personally I would go with the most aero you can get for both Cota and Msrh.

Once you sort the brakes and get more familiar with the car 43ís are certainly attainable stock. (Regardless of aero)

are you a member? I may be out there on the 21st
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Old 07-12-2019, 09:06 AM
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I would like to get 18's but it will be a bit before I can invest in wheels. I put a bunch down on the car, bought all the aero pieces, and did PPF so I'm tapped out lol. I'm waiting to see a nice used set pop up.

I'm not a member but go on some member days and I instruct with Driven & Blessed. Last weekend I was out there with Car Culture for a free event they put on to drive memberships. Are you a member?
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Old 07-12-2019, 10:33 AM
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Originally Posted by wings19 View Post
I would like to get 18's but it will be a bit before I can invest in wheels. I put a bunch down on the car, bought all the aero pieces, and did PPF so I'm tapped out lol. I'm waiting to see a nice used set pop up.

I'm not a member but go on some member days and I instruct with Driven & Blessed. Last weekend I was out there with Car Culture for a free event they put on to drive memberships. Are you a member?
I'm not a member, I live too far up north from the track to commit to it. I have quite a few friends that are tho. So I usually mooch off them. Also I dont think i would commit to a membership anyway since they cant seem to make basic repairs to their facility. Makes me question the longevity of the track.

I mostly drive with NASA and instruct for them, member days, Chin or Drivers edge. You should come drive with NASA, we'll be at Texas Motor Speedway (full ROVAL configuration) next month.

I'll also be at COTA next weekend for the Edge Addicts "nighttime" event. $575 for 5 sessions 2 of which in the dark.


fwiw to keep your thread on topic, the GM aero bits while decent are nowhere near comparison to a good wing (even the ZR1 wing is kind of meh compared to one that's not making compromises)
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Old 07-12-2019, 10:54 AM
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I have driven with NASA and Chin, I enjoy both of those organizations. I've never driven with TDE because when I had the GTR it seemed Rick had an aversion to me immediately so I chose to drive with other orgs instead.

I'm probably going to wait until September until I hit the track again. Need to get the car better sorted and it's so damn hot right now.

I appreciate the insight, let's get together next time at the track.
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Old 07-12-2019, 11:14 AM
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Originally Posted by wings19 View Post
I have driven with NASA and Chin, I enjoy both of those organizations. I've never driven with TDE because when I had the GTR it seemed Rick had an aversion to me immediately so I chose to drive with other orgs instead.

I'm probably going to wait until September until I hit the track again. Need to get the car better sorted and it's so damn hot right now.

I appreciate the insight, let's get together next time at the track.

LOOOOOOOOTS of GTR's have shown up at TDE and driven very poorly but they're so damn fast and they typically just don't get it. "faster on the straight" = faster to them. I'm pretty sure thats why Rick has an aversion lol.

TDE's red group has gotten pretty bad tho. The last time I was out there, it was just a **** show. Most of the drivers are casuals. I still think that TDE has the best program when it comes to teaching new students but it kind of falls off a little later. I think part of the problem is that they talk like the red run group is the pinnacle of driving so lots of those guys are slow and don't realize it thats's all they ever do is TDE so they dont really have a lot of exposure to faster drivers.
Red group is safe just not fast is what i mean by bad. They're all pretty good drivers safety wise and dont really have a problem getting stuck behind anyone.

We have a track junkies discord going if you want to get in on that, its mostly Texas area racers. We talk about events, car setups, builds etc.

Most of which are with NASA but we have HPDE guys too. it's a fun chat.


Also no kidding it's hot as hell I'm not exactly looking forward to next weekend or the TMS event. May even take a break until NOLA in october.
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Old 07-12-2019, 11:34 AM
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Awesome, shoot me a Discord invite.
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