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C7 Z51 TT2/ST2 build thread

 
Old 03-02-2019, 09:11 PM
  #21  
BrunoTheMellow
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Originally Posted by BrunoTheMellow View Post
MSR is my home track. Heres my best lap there so far. Z51 with 255/295 r888rs and Z06 aero. 1:23.4

I'm going back in a month with 295/305 r888rs and Z06 springs. Hoping to hit 1:22 flat.

also you mentioned the car is on 750lb front springs. As a comparison Z06 springs are 670lb front. Z51 magride 450, z51 nonmagride 525.

https://youtu.be/w7ytltJNXsw
So interestingly enough, article in grassroot motorsports April 2019 edition testing coil vs leaf spring rates. After 3 coils and 4 leafs tested, the conclusion was leaf spring rates were about half of coils in actuality even with similar quoted rates.

Here are some results:

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Old 03-03-2019, 10:50 AM
  #22  
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Well that's super interesting.

Originally Posted by BrunoTheMellow View Post
So interestingly enough, article in grassroot motorsports April 2019 edition testing coil vs leaf spring rates. After 3 coils and 4 leafs tested, the conclusion was leaf spring rates were about half of coils in actuality even with similar quoted rates.

Here are some results:
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Old 03-03-2019, 11:20 AM
  #23  
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Didnít read article but lead rates are quoted for the whole sprig. Have to divide by 2 to get comparable corner rate. So a VBP 1200 leaf is 600 per corner bolted up.
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Old 03-03-2019, 11:31 AM
  #24  
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I remember reading a tech article on Corvette transverse springs a long time ago that said the springs are designed to "twist" with compression. The spring rate, therefore, increases with increased compression. Just reporting what I read - I'll see if I can find the article.

Pappy
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Old 03-03-2019, 12:20 PM
  #25  
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Originally Posted by Tool Hoarder View Post
Didnít read article but lead rates are quoted for the whole sprig. Have to divide by 2 to get comparable corner rate. So a VBP 1200 leaf is 600 per corner bolted up.
I see. Didn't realize this. So z51s have 225 lb springs ? Jeez.
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Old 03-03-2019, 12:20 PM
  #26  
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Originally Posted by mfain View Post
I remember reading a tech article on Corvette transverse springs a long time ago that said the springs are designed to "twist" with compression. The spring rate, therefore, increases with increased compression. Just reporting what I read - I'll see if I can find the article.

Pappy
That physically doesn't make sense. There's is no angular load applied.
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Old 03-03-2019, 12:24 PM
  #27  
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Originally Posted by BrunoTheMellow View Post
That physically doesn't make sense. There's is no angular load applied.
Could be the physical profiling or varying density of the spring material that causes it to twist as it compresses??? I'll find the article.

Pappy

Edit: This is not the article I was talking about, but this paragraph from Wikipedia shows why it is hard to pin down the actual rate of the Corvette transverse spring. When the car is compressed level (equal compression on left and right side), then you get equal wheel rates for both wheels. However, if the compression is in roll, the wheel rate of one side varies with the amount of compression on the other side, so the wheel rate varies with amount of loading and degree of roll.

From Wikipedia: "When either wheel is deflected upward, the center span of the spring (the portion between the pivotable mounts) deflects downward. If both wheels deflect upward at the same time (for example, when hitting a bump in the road) the center section bends uniformly between the pivot mounts. In a roll, only one wheel is deflected upwards, which tends to form the center of the spring into an S-shaped curve. The result is that the wheel rate of one side of the suspension depends on the displacement of the other side.[8]
[9]
[13] The extent to which the spring acts as an anti-roll bar depends on the distance between the pivot mounts and their rigidity.["

Last edited by mfain; 03-03-2019 at 12:46 PM.
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Old 03-03-2019, 04:34 PM
  #28  
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Originally Posted by mfain View Post
Could be the physical profiling or varying density of the spring material that causes it to twist as it compresses??? I'll find the article.

Pappy

Edit: This is not the article I was talking about, but this paragraph from Wikipedia shows why it is hard to pin down the actual rate of the Corvette transverse spring. When the car is compressed level (equal compression on left and right side), then you get equal wheel rates for both wheels. However, if the compression is in roll, the wheel rate of one side varies with the amount of compression on the other side, so the wheel rate varies with amount of loading and degree of roll.

From Wikipedia: "When either wheel is deflected upward, the center span of the spring (the portion between the pivotable mounts) deflects downward. If both wheels deflect upward at the same time (for example, when hitting a bump in the road) the center section bends uniformly between the pivot mounts. In a roll, only one wheel is deflected upwards, which tends to form the center of the spring into an S-shaped curve. The result is that the wheel rate of one side of the suspension depends on the displacement of the other side.[8]
[9]
[13] The extent to which the spring acts as an anti-roll bar depends on the distance between the pivot mounts and their rigidity.["
S shape as in $ where the | is the cars axle.
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Old 03-04-2019, 10:44 AM
  #29  
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Leaf spring rates and engineering sounds like a good "Ask Tadge" question...
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Old 03-05-2019, 09:33 PM
  #30  
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Well finally installed the fender spats. They're gonna be absolutely necessary for my new 10.5" front BC Forged wheels.


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Old 03-09-2019, 11:13 PM
  #31  
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Car no longer has carbon fiber side skirts

they were here ripped off today


F
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Old 03-10-2019, 09:57 AM
  #32  
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On track?
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Old 03-10-2019, 11:06 AM
  #33  
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Originally Posted by ErnieN85 View Post
On track?


lol yeah
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Old 03-10-2019, 11:33 AM
  #34  
Poor-sha
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I think this was asked earlier but I never saw an answer. What is the solenoid looking thing bolted to the rear cage in your first picture? It has two heavy gauge wires coming form it.

Also, any issues with headroom with the cage? Could you shoot some pictures of the front part of the cage and where the roll hoop is located?

Thanks!
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Old 03-10-2019, 10:02 PM
  #35  
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Originally Posted by Poor-sha View Post
I think this was asked earlier but I never saw an answer. What is the solenoid looking thing bolted to the rear cage in your first picture? It has two heavy gauge wires coming form it.

Also, any issues with headroom with the cage? Could you shoot some pictures of the front part of the cage and where the roll hoop is located?

Thanks!
Solenoid is for my kill switch.

please ignore the paint job, I did the painting myself in a rush job before a weekend and never got around to cleaning it up.

I personally have no issues but anyone taller than me would almost assuredly have to have the seat lowered substantially.

I also seem to of forgotten to get the pictures of the main hoop. I left my car with GSpeed for some work so can't get any more pictures for a minute.





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Old 03-10-2019, 10:50 PM
  #36  
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So, has a **** poor Saturday just wasn't feeling great. Missed the first session for.. reasons... went off track the next two sessions.

busted my carbon fiber side skirts. I wont be replacing those. at least not for full price lol.

They lasted approximately 3 events if anyone is curious.

My cars last dyno was 393 that I had done in January which is lower for no real reason than the last dyno (419) I'm speculating its the catalytic converters turning into garbage. So I left my car with GSpeed. For some Kooks headers and a tune.

Maybe a corner balance if I can afford it. Either way to compete with the TT2 front runners I need to get the car more on a level playing field.

So up my power a bit while staying in class. Add a touch more front downforce, possibly experiment with sticking 315/30/18's in the front on my new 10.5 front wheels.

I wasn't expecting to beat those guys this event. TT2 guys were all tenths off in the 1:15's with my trailing behind with 1:19 (and the guy behind me a 1:23 for the sake of my own ego)
Not going to lie, it took me until today to get a feel for the track.
I can easily see a 1:18 with some more seat time and keeping the car as is.

With a few of the aforementioned changes 17's and with some more coaching and practice.. then maybe we can look at being on the same page as them.

One of my goals is to beat a particular Lotus at NOLA at the end of the year. This thread is going to document that journey. Successful or not, I'll have fun.


ETA:
looking at my data from this weekend, I see very costly mistakes everywhere. I hate cresson

Last edited by lobsterroboto; 03-11-2019 at 11:55 AM.
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Old 03-11-2019, 10:56 AM
  #37  
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That front tube looks like a leg breaker in any accident... you're stuck with it now, but why didn't they trim back the rocker and go straight down onto the frame rail?
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Old 03-11-2019, 11:53 AM
  #38  
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Originally Posted by Tool Hoarder View Post
That front tube looks like a leg breaker in any accident... you're stuck with it now, but why didn't they trim back the rocker and go straight down onto the frame rail?
I'll ask my builder, I certainly didnt build it. I thought about that when i got the car back and didnt bother to ask.

I think maybe just because its in line with the main hoop? I dunno
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Old 03-11-2019, 11:29 PM
  #39  
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Originally Posted by lobsterroboto View Post
Either way to compete with the TT2 front runners I need to get the car more on a level playing field.

So up my power a bit while staying in class. Add a touch more front downforce,
Even with reduced power, SLJHMR still has very good midrange and I feel that really helps with drive-ability out of the corners (both slow and fast) since the power delivery is more predictable and easier not only to drive but also consistent to setup for.

As for front DF, how big is your splitter? I made the one on SLJHMR as a prototype (so it aint pretty-ified) carbon one and it might weigh 10lbs I think whereas the plywood was 30. Obviously the carbon is not as durable, but there you go. I made a prototype for a c7 as well and it is floating around there somewhere in the millions of corvette parts. I think it was a 7" splitter....but I've slept and built other stuff since then so that's likely not accurate.

I can easily see a 1:18 with some more seat time and keeping the car as is.
Agreed. I have very little time at Cresson and most of it in the wet until this weekend...so thanks to Louis running data and Hester (another data guy) telling me where I was sucking, I picked up about a full second. On Sunday I still went the wrong way on a change and cost us the win. Oh well, live and learn.

With a few of the aforementioned changes 17's and with some more coaching and practice.. then maybe we can look at being on the same page as them.
Agreed again...you'll get there. Good plan to get the car a bit closer and then focus on driving and coaching. That is where you'll find the big gains.

Costas
cars and such...
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Old 03-12-2019, 09:32 AM
  #40  
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Thanks costas

If i remember my splitter is right at 8"

I'm going to make revision 2.0 about 4" out on each side and add some splitter diffusers/tunnels and see what that gets me. I'm also gonna cram some 315's up front.

The splitter is stupid heavy (it's birch plywood)


Yah I have no delusions, I'm still making large adjustments in my skills and not quite fine tuning yet. I realized that I wasn't doing nowhere near enough driving last year, basically every NASA event which wasn't a lot of laps collectively in TT and some member days sporadically and like one DE.

That will give me the biggest gains.
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