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#1062958 - 07/29/19 09:38 PM Re: SSLance's Build thread [Re: SSLance]  
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No issues here MAP, I'm used to explaining to engineers why practical experiences sometimes trump math on paper. laugh


Ron Sutton who had a ton of race suspension tuning had never ridden in a car driven on an autocross course like I do either and I had to show him video of how we were creating forces more quickly and more powerful on our parts than he or the manufacturers ever imagined.

When you have a swaybar on a stick axle, it's either going to twist or lift the inside tire in the air, that's the only two choices. I've seen lots of the latter.

The only reason I put the soft rear springs back Is because the front roll resistance is so massive and works so well now, I feel I can go ba k to a softer rear to gain more forward bite which I so desperately need. On the street, there appears to be little difference in rear roll but I know once on track that will change. I just need to find the lesser of two evils.

BTW, just filled up 13.5 gallons, had less than 1/8 tank on guage. Before filling I made several hard launches and some aggressive turns with zero fuel starve. 11.5 MPG I have no idea if that's good or not, lot of hard driving and really hot days on that tank.


Lance
1985 Monte Carlo SS Street Car
#1062960 - 07/30/19 12:27 AM Re: SSLance's Build thread [Re: SSLance]  
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Hi Lance,

The practical never conflicts with good theory. When the two diverge, the explanation is that the theoretical is faulty or incomplete. As Einstein said, everything in the universe should be as simple as possible, but no simpler. Assuming we haven’t made dumb mistakes with the theory, then we've oversimplified the theory. Ron Sutton is very smart and vastly experienced, but by his own admission, he's no engineer. Remember what I said about the profound flaw in his claim about the relationship between caster, camber, and kingpin inclination.

Again, I come back to other as-yet-unknown factors at work, that are creating the impression that the underlying theory is wrong. The real explanation here is that vital pieces of this picture are still missing. Oversimplification again. Swaybar and lifting: true if no springs are involved. But they act in concert, and in pure roll the combination, exactly - not approximately - mimics stiffer springs. We need that whiteboard!

Let's try it this way: imagine a rear with a perfectly rigid rear sway bar and soft springs. The car rolls. And, exactly as you say, the inner wheel lifts: it has no choice so to say, and again, exactly as you say. But now let's remove the swaybar and substitute perfectly rigid springs. The car rolls. What is the result? The inner wheel lifts in exactly the same way.

HTH,
MAP

PS: 11.5 mpg with lots of hard driving: that sounds good!

Last edited by MAP; 07/30/19 12:31 AM.
#1062962 - 07/30/19 12:56 AM Re: SSLance's Build thread [Re: SSLance]  
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While not a complete test, this was a good start to my rear bar decision making about 5 years ago.

https://youtu.be/QzsIIIf5PaI

If I recall with that setup, I ended up with 250# springs and no rear sway bar and that was the best way I found to keep inside rear tire down on the ground. It got even better when I put the 600# springs in the rear.


Lance
1985 Monte Carlo SS Street Car
#1062965 - 07/30/19 05:38 AM Re: SSLance's Build thread [Re: SSLance]  
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Hi Lance,

Great video - thanks for sharing it! Again, I don't question the observations, but rather the conclusions. What the video proves is that as you reduce rear roll stiffness while making no other changes, the inner wheel stays in better contact with the pavement. That's all, and it's certainly unsurprising. But we're vastly oversimplifying the full dynamic picture of what's going on here, and for this reason, drawing faulty, or rather incomplete, conclusions.

Lance, I'm going to sign-off on this topic now, because there's only so much we can communicate through a simple internet thread. A deeper dive would require a different venue - please take no offense.

Best,
MAP

Last edited by MAP; 07/30/19 05:48 AM.
#1062969 - 07/30/19 02:38 PM Re: SSLance's Build thread [Re: MAP]  
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Again, No offense taken at all MAP, I actually enjoy conversations like this. Much better than arguing about politics or religion. laugh

Here is exactly where I have an issue with your premise.

Originally Posted by MAP


Let's try it this way: imagine a rear with a perfectly rigid rear sway bar and soft springs. The car rolls. And, exactly as you say, the inner wheel lifts: it has no choice so to say, and again, exactly as you say. But now let's remove the swaybar and substitute perfectly rigid springs. The car rolls. What is the result? The inner wheel lifts in exactly the same way.



Every coil spring I have seen used with these platforms are open ended and the only thing holding them in place is the pressure between the top spring perch and the bottom spring perch. There is nothing on either end of the spring to pull as the spring is extended.

Given that fact, how can a spring pull up and lift the inside tire off of the pavement like I showed in the video example above?


Lance
1985 Monte Carlo SS Street Car
#1062972 - 07/30/19 07:58 PM Re: SSLance's Build thread [Re: SSLance]  
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Hi Lance,

Thanks for that! OK, that's an easy one: yes, the presumption is that we operate each spring (and the sway bar is just another spring) within its linear range, where compression yields an opposing restoring force. Outside of that range, things change radically.

That scenario is, let's say, unintended and somewhat illegitimate, because both mark sharp diverges from their normal, linear ranges of operation, although the swaybar case is sharper than the loose-spring case. My experience is that whenever the suspension diverges from linearity, and especially in this distinctly bimodal way, the car often becomes difficult to control. Given that, it's true that the loose spring at least allows some traction on the dangling inner wheel to help handling of the car, whereas in the case with the lifted wheel with the sway bar, the inner tire loses all contact with the road, and the car corners on three wheels (I see this all the time with very nose-heavy FWD cars with lots of rear roll stiffness. If you slam on the brakes with one wheel in the rear dangling in the air, we have a guaranteed oversteering spin-out.)

Lance, this is a great example of expanding the picture to include more of those "other factors." In theory, a relaxed swaybar could be decoupled from the suspension in exactly the same way as a relaxed spring is decoupled, but it would get a bit bulky and complex from a packaging perspective.

I would much sooner use a less-stiff swaybar to increase its linear range so that we don't lift the inner wheel at times when we still need traction there. Stiff springs that are allowed to dangle at the extremes of suspension motion is just a bandaid solution (I know, better a poor bandaid than no bandaid at all.) But I think there are much better, although more difficult solutions. One obvious way is take weight, and in this case lots of it, off the front end of the car. Another way is to reduce the car's COM height, so we need less roll stiffness at both axles. What a great place to make a plug for an EV conversion for our cars.

And speaking of which - I just got a job offer out of the blue from Tesla! Too bad it's in the SF bay area, the birthplace of million-year home mortgages...

Best,
MAP




Last edited by MAP; 07/30/19 08:38 PM.
#1062973 - 07/30/19 09:20 PM Re: SSLance's Build thread [Re: SSLance]  
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Thanks MAP!! I think you just said I was right. laugh

It shouldn't be any secret by now that the way I drive this car on course pushes it way past normal driving circumstances. One of these days Ill get you in the right seat for a run and can guarantee two things when I do. First, you'll giggle like a school girl and second...you'll be amazed at how fast and hard the car reacts to the inputs thrust upon it. The car will do things you never imagined it would...

Congrats on the job offer, I sure it was exciting even if the details arent exactly as you prefer.


Lance
1985 Monte Carlo SS Street Car
#1062974 - 07/30/19 09:52 PM Re: SSLance's Build thread [Re: SSLance]  
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Hi Lance, why yes - I did say you were right! But don't let that go to your head(!) It's like saying, gee, Harry, you were right to cut-off your arm with a switchblade when you saw you were trapped underneath that boulder.

Exaggerating for comic effect but wow, there are much better ways to handle this. Too bad, however, that you're not willing to alter the basic structure of the car to make bigger gains. Then again, you're probably thinking - and rightly so for about 99.999999% of us - that what you've got is more than good enough - so why press for more?

At work I had a nickname by the other engineers - Tensig. That's short for "ten sigma," a reference to statistics with a Gaussian density function, for being faaaaaaaaaaar away from the norm.

Tesla: actually, they came back and asked if I would consider Sparks, NV instead. This is getting interesting!

Thanks!
MAP

#1062975 - 07/30/19 10:16 PM Re: SSLance's Build thread [Re: SSLance]  
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Nice!! That is interesting. Good luck.

I'm about done improving the on track performance of this car. I'm not willing to do the weight reduction it will take to move it up in charts and I already believe it outperforms where it should inspite of the weight handicap. What I'm working on now is getting the comfortable street manners back into it without loosing the performance gains I've made so far.

I'm loving street driving it more and more all the time.


Lance
1985 Monte Carlo SS Street Car
#1062976 - 07/31/19 04:23 AM Re: SSLance's Build thread [Re: SSLance]  
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Hi Lance,

Perfectly understandable. And I can directly attest to the fact that it outperforms where it should considering the weight handicap. You've probably pushed the very edge of what's possible short of major surgery. Yes, good street manners and sharp handling tend to be mutually exclusive. That's why Bose invested so heavily in active suspension development. An active suspension delivers absolute top-notch performance and a glass-smooth ride in the same package. It's literally impossible for a passive suspension to do as well. Lance, if you could have ridden in one of those demo cars, you would have been absolutely floored. Even though they weren't tuned for maximum cornering acceleration as you've done, it would have been a piece of cake to make the switch. The possibilities are almost endless: you can, for example, program it for negative roll, so that it corners like a motorcycle.

Here's a video from some years ago: https://www.youtube.com/watch?v=3KPYIaks1UY

Neal Lackritz is a very sharp guy (MIT) and someone I'm thankful to count as a friend. We had a number of conversations about project sound.

Best,
MAP

Last edited by MAP; 07/31/19 05:12 AM.
#1062980 - 07/31/19 02:05 PM Re: SSLance's Build thread [Re: SSLance]  
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Originally Posted by SSLance
Nice!! That is interesting. Good luck.

I'm about done improving the on track performance of this car. I'm not willing to do the weight reduction it will take to move it up in charts and I already believe it outperforms where it should inspite of the weight handicap. What I'm working on now is getting the comfortable street manners back into it without loosing the performance gains I've made so far.

I'm loving street driving it more and more all the time.


Now that it's your DD once the 383 gets tired, just toss an aluminum 6.2 LS in there, 100lbs off the nose like that lmao

And I'm with you Lance, I don't really like the idea of cutting the car up for another .010 on the timing board. Once the 3 link is in for me, the car is "done" mechanically and creature comforts (AC, SFI, better seats, lighting) and paint and body work are my next steps. I'm done trying to turn a sows ear into a silk purse. It's the law of diminishing returns.


86 SS 6.0L LQ4, TBSS GEN IV intake, 92mm TB, 30lb injectors, Summit Stage 3 NA Cam, Stainless long tube headers, Stainless 3in exhaust, Microsquirt ECU, FABbot AR5 5-speed, Torsen LSD, QA1 Lvl 3 Suspension Kit, UMI Front & Rear Braces. Check out my build blog on Summit Racing's OnAll Cylinders https://www.onallcylinders.com/author/travis-jones/
#1062981 - 07/31/19 04:47 PM Re: SSLance's Build thread [Re: MAP]  
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Spending $10,000 to save 100#s doesn't really make any sense either now does it? laugh

I don't regret any of the work or parts I've thrown at this car to get it to where it is today, I think I've learned a ton during the whole process and hopefully helped others learn something along the way as well. And I'm not giving up on competing with the car either, I still very much enjoy that part of it as well. As long as it and I can keep beating cars we aren't supposed to be able to beat, I'll keep enjoying racing it. I'll just enjoy street driving it as much if not more with the other refinements I'm currently working on.


Originally Posted by MAP


Here's a video from some years ago: https://www.youtube.com/watch?v=3KPYIaks1UY



Now that is freaking cool! I had no idea that Bose worked on projects like this. That had to be a strange feeling driving that car with the modified suspension... One I'd like to experience...


Lance
1985 Monte Carlo SS Street Car
#1062982 - 07/31/19 07:39 PM Re: SSLance's Build thread [Re: SSLance]  
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Hi Lance, Travis,

About project sound: I never got behind the steering wheel. Only a very, very privileged few were allowed that special seat.

About ROI on major surgery: if I'd ever go back to hack-up an A/G body for further performance gains, it would only be to do something radical, not incremental. Hence, EV conversion and a big shift of COM location. I see an ICE solution for an A/G body as a losing proposition because more power, other things being equal, means more weight on the front axle. That's exactly where we don't need it! GM switched the C-8 Corvette from a front-engine to a rear-engine design for the same reason.

The appeal for me, of course, is not only the performance gain, which I suspect would be profound, but the appeal of the swap challenge itself, which would include converting the car to a unibody structure, which speaks mostly to the NVH aspect. One of the things that came out of project sound was the importance of a stiff chassis on which to hang all the control elements. At the time, only that Lexus was stiff enough to get the job done, and even that was rather marginal. But what's good for active is also good for passive: we need to start with a stiff chassis, and the A/G body platform is anything but that. Neal and I spoke of the miserable stiffness of the body-on-frame designs of that time: for example, the primary vertical resonance in longitudinal bending of the Crown Vic, at 18 Hz. I believe the A/G body was even worse, at about 15 Hz. That's why they used the unibody Lexus, at about 23 Hz as I recall.

Bose worked on all kinds of top-secret stuff that would surprise the outside world. Dr. Bose was a researcher at heart who always cared deeply about improving the quality of life for people.

Btw, this might be a good place to add that GM's MR (i.e. magneto-rheological) shocks are active in nature too, but only with respect to dampening. They use externally-controlled magnetic fields to vary the viscosity of the internal fluid, and thus the dampening, of the shock absorber. This happens in essentially real time. It's therefore limited in effect but still quite useful. OTOH project sound was a full-blown control package. If we could ever get the price of neodymium down to something reasonable, project sound might well still bear fruit.

OK. So dialing this back down to a level where ordinary humans like you and me can actually do something worthwhile, we must recognize that as time goes by, the factory performance curve will continue to climb steeply. Understanding that we'll be restricted to passive solutions, what can we do? I believe the first step is exactly what Lance did: use the very best tires, and optimize suspension dynamics within the constraints of what is basically the 1960s factory configuration. The next step up is major surgery as I've described it. The next step up from there, unfortunately, involves money with a whole lot of zeroes in the denomination. Wish I could paint a rosier picture...

Best,
MAP

Last edited by MAP; 07/31/19 08:24 PM.
#1063234 - 08/20/19 04:17 PM Re: SSLance's Build thread [Re: SSLance]  
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I have about 350 street miles now on the EFI setup. Andrew and I (mostly Andrew wink ) have been tweaking away on the tune and I think we are just about done with it. After working on the fuel table trying to clean up a few small problem spots, we finally started adding timing and that woke things right up. Turns out this Fastburn 383 likes more timing in the mid RPM range, a little bit more timing upper RPM WOT and a little less timing at idle. Who knew? :headscratch:

We now have it where it'll lug smoothly at 1200 RPM in 6th gear on the highway, pulls like a freight train everywhere else when asked and runs like a 5th Gen Camaro under normal everyday driving. Still haven't decided if I'll ever put it on a chassis dyno or not, only real reason would be to see what the torque and horsepower curves look like and where the peaks are. My butt dyno says the HP peak is a lot higher than the 5400 RPM it was before with the dual plane intake and Quadrajet though. I raised the rev limiter to 6400 from 6000 because I kept hitting it regularly with car still pulling hard. I hardly ever hit it before as I was shifting before it got there.

Couple other things I've cleaned up to make it more street friendly. I put a new blower fan relay in which not only lets the fan work at all 4 speeds now, but also doesn't kill the charging system when the fan is on high.

Took the 600# rear springs out and put 250# springs in and added a UMI Autocross rear sway bar back in. Both are a big improvement for street driving both in comfort and in feel, hopefully it'll still corner good once I get it on track again.

The brand new RE71s I picked up are now installed as well, way over due for them. Hopefully the new rear setup provides more rear forward bite grip and I won't kill these nearly as fast as the last set.

I was going to do a track day at Inde Motorsports Ranch Labor Day weekend as my first track test of all the new stuff, but a family deal came up so I'll have to miss that. Love track days and love that track but at the same time kind of happy that I'll have an autocross event or two to test all the new stuff out before thrashing the car on a big track once again.

Meanwhile, I'm just driving the car every chance I get. First tank of gas netted 11.5 MPG, it'll be interesting to see how the next tank ends up shortly. I'm hammering it pretty hard doing the EFI tuning so I expect it'll get better with more just regular driving. Not really the most important goal but a nice side effect if I can save a bit of fuel along the way.


Lance
1985 Monte Carlo SS Street Car
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