: CTS-V wheel hop reduction - a higher tech alternative?



HiTechRV
03-02-07, 11:24 PM
I was talking to an old friend yesterday who reduced wheel hop on an older high power corvette by reducing and increasing engine richness to damp out the power in opposite phase to the wheel hop.

He was thinking we could tap into the accelerometer values in the body management computer to vary the power being applied thru the ECU in a similar way.

Sure sounds interesting in theory.

Florian
03-02-07, 11:34 PM
oy vey.....not even a chance.


F

DILLIGAF
03-02-07, 11:37 PM
AHHHHHHHHH,I did a 2nd gear dump at 2000 rpms without a hint of hop an hour ago.Stock diff

HiTechRV
03-02-07, 11:45 PM
I'm not sure if the values for the accelerometer get put on the CAN bus, but I think it is a pretty slick idea. Varying the ECU power could be very easy - even externally thru the throttle drive by wire signal.

The idea is sound. As the initial suspension downward stroke in the rear starts slowing down, back off the power a little. As it starts to move back up (hop), go back to WOT.

Lyn Labahn
03-03-07, 01:49 AM
I highly doubt the system response time is adequate to produce a opposite phase power pulse to reduce the wheel hop. You would be better off just modifying the physical system to prevent the input, or reduce its response to the input. I am an engineer if that helps convince you at all.

Oregon Stealth
03-03-07, 05:53 AM
Ok. if I'm understanding correctly you're suggesting detuning the engine in an harmonic that would be counter to the wheel hop harmonic. While an interesting theory and probably possible given the correct resources, I'm forced to wonder why? IMHO this is admitting that the engine puts out too much power for the suspension to handle and ignores the problems in the suspension causing the hop. Why not focus on the mechanical issues in the suspension to fix the problem and then be able to fully utilize all the power the engine can produce? Sounds like basic weak link theory to me, but then again I've been known to be very wrong/confused and am open to someone explaining the advantages of this approach to me.

keeksv
03-03-07, 08:57 AM
You can't polish a turd, in other words....

Jpjr
03-03-07, 09:31 AM
Dude, sending 350hp to the rear wheels of an IRS sedan meant for luxary driving is always going to leave you with wheel hop. This engine harmonic thing is the funniest solution I have ever heard though.

Wheel-hop recipe (in order of importance)

1. Get stickier tires.
2. Beef up your diff and suspension.
3. Remove any bubble gum rubber bushings with polyurethane or delrin.
4. Add lots of power and put a few dumbbells in the trunk.

TrazzNJ
03-03-07, 12:52 PM
I can't even believe anyone actually responded to this !! Here's an idea. Take out your LS6/LS2 and put in a 4.3ltr chevy vortek V-6(torquey little sucker). You won't have any problem with wheel hop and you can get vanity plates that say CTS-V6.
How cool would that be ???!!!

DILLIGAF
03-03-07, 05:12 PM
I can't even believe anyone actually responded to this !! Here's an idea. Take out your LS6/LS2 and put in a 4.3ltr chevy vortek V-6(torquey little sucker). You won't have any problem with wheel hop and you can get vanity plates that say CTS-V6.
How cool would that be ???!!!So your point is?

90Brougham350
03-03-07, 05:49 PM
Wouldn't the conditions of the road (resulting in different traction coefficients) and the amount of gas in the tank (cause a slightly different downward force on the rear-wheels) be enough as far as variables are concerened to make any programming in the ECU totally ineffective except under the exact conditions the program was written for?

TrazzNJ
03-03-07, 06:25 PM
I'm not sure if the values for the accelerometer get put on the CAN bus, but I think it is a pretty slick idea. Varying the ECU power could be very easy - even externally thru the throttle drive by wire signal.

The idea is sound. As the initial suspension downward stroke in the rear starts slowing down, back off the power a little. As it starts to move back up (hop), go back to WOT.

My point is that it is a completely ridiculous idea. It is not sound, in fact, it is laughable. You may reply to this as you wish but when you do, just refer back to my first two sentances. I will not waist any more time on such an absurd idea.:thehand:


:horse:

ctsvflorida
03-03-07, 06:55 PM
I can't even believe anyone actually responded to this !! Here's an idea. Take out your LS6/LS2 and put in a 4.3ltr chevy vortek V-6(torquey little sucker). You won't have any problem with wheel hop and you can get vanity plates that say CTS-V6.
How cool would that be ???!!!

I just laughed so f***in hard reading this post! As I am reading these other hilarious posts I was thinking exactly what you wrote! BIG points for you TRAZZNJ! Can't wait for Gainesville, we'll have a ball!

I am still laughin my azz off!

Choo choo Charlie was an engineer too by the way!

05CTS
03-03-07, 07:24 PM
There is too much deflection in rubber bushings. They should be replaced w/poly bushings and stiffer rear shocks.

nikon
03-03-07, 07:45 PM
ummm....ya, it's already got that, stock.....ask jesse bubb (wait4me) Im sure stealth would be able to tell you the same...they can disable, but it can't be disabled by turning traction/stability control off...I though you guys new that??

if you don't believe me...sorry for going to the 'other' board but well....oh well.

http://www.ls1tech.com/forums/showthread.php?t=634729&highlight=wheel+hop

Imperator
03-03-07, 09:43 PM
http://www.doubledeez.net/Funney/inout2.gif

livingthedream
03-03-07, 11:07 PM
Not sure about all the adjustments noted, but I put in KARS III and wheel hop is all but gone. Cannot remember when I last had an issue with hop.

Had to adjust it once, retighten once I ran some miles on the initial install, but its been perfect since then.

livingthedream
turn the key and smile

HiTechRV
03-03-07, 11:18 PM
I highly doubt the system response time is adequate to produce a opposite phase power pulse to reduce the wheel hop. You would be better off just modifying the physical system to prevent the input, or reduce its response to the input. I am an engineer if that helps convince you at all.

I'm an engineer too. The guy who proposed it to me used to be chief engineer at Summit racing - he's pretty knowledgable. He already did this once on a Corvette he owned - and it worked. He had to use lean/rich adjustment because that engine management computer was too slow to directly alter the output, but the power drop from quickly richening up the mix was enough to damp the wheel hop. And he did not have any accelerometers built into the car to work with like we do. The frequency of the sine wave on wheel hop is VERY slow. Only a few cycles per second - an eternity compared to the speed of the electronics we are talking about in the V.

It may not take much more than a simple PID loop using an accelerometer as input and some output to the ECU to adjust power output. All you need is a little negative feedback in theory. You could engage it manually and flip it off once you got going as a simple way to try it out.

The reason it is interesting to me is it does not compromise all the track tuning that went into the original suspension design. Some of the other wheel hop solutions have the potential to degrade either the ride quality or handling of the car as designed.

I have not asked but if the next gen V has magnetic ride control, that is very fast in comparison to wheel hop - 1000 corrections per second if I recall right. It could also be used to counteract wheel hop directly by sensing and adapting shock stiffness to wheel hop in extension and compression. Not sure what it would take to get a couple of those shocks from an STS onto a CTS.

If you think about it most of the trick is to reduce power just for that last inch or two as the suspension in back bottoms out the first time. Then as it just starts to lift for the first hop, transfer to full power. Taking the bounce out of that first compression is all it takes to transfer the weight back and use the engine's power to pretty much keep it there for the rest of the run.

You guys running Bose noise cancelling headphones are using the same principle, only those cheesy little DSP's are doing it at like 1000 or more times the rate required here. And the waveforms being cancelled are a LOT more complex.

keeksv
03-04-07, 01:26 PM
Not an engineer, but you would have to account for and correct the lateral movement of the car that helps start the wheel hop. The car hunches down in back and to the right rear wheel when you punch the "go" pedal in my experience...

Now I'm going to bail out of this thread and go light up the tires a bit on a Sunday afternoon...with no wheel hop.

HiTechRV
03-04-07, 04:33 PM
Actually THAT is exactly the biggest problem I saw with the approach - it does not compensate for the difference in hop side to side (no I'm NOT an M.E.). The right hand rule comes to mind.

Basically if you start running from 90% to 100% throttle (or whatever the numbers show you need to damp the right wheel hop), you are pushing as well on the left wheel that is still in initial compression. It clearly would reduce the hop over what we have now, but not likely eliminate it. The throttle reduction in the latter half of the downstroke should even reduce the difference in the force on the right and left rear wheels a touch.

Shocks with separate bound and rebound settings will do this wheel by wheel mechanically. Magnetic ride strut correction can compensate for the side to side difference electronically in a similar fashion. I wonder if the STS-V does any wheel hop cancelling with the magnetic shocks. The slushbox and 4V engine will make it less of a problem but I imagine it would still be an issue.

I wonder how hard it would be to model the dynamics of wheel hop in one of the UG tools, and then compare to a controlled launch sequence.

I wish I had payed more attention in Dynamic Systems class lol.

nikon
03-04-07, 04:43 PM
ummm....ya, it's already got that, stock.....ask jesse bubb (wait4me) Im sure stealth would be able to tell you the same...they can disable, but it can't be disabled by turning traction/stability control off...I though you guys new that??

if you don't believe me...sorry for going to the 'other' board but well....oh well.

http://www.ls1tech.com/forums/showthread.php?t=634729&highlight=wheel+hop

ahem......

Lyn Labahn
03-05-07, 12:42 AM
Dynamically changing the output of a small sound signal (Bose Headphones) vs a car's drivetrain is a completely different animal due to the intertia involved. During my university days we used ignition timing and electronic throttle position for traction control on a small Formula SAE car with moderate success. This was a "step" change in input, and not actively changing an output. Are you postive your friend was producing a varying signal, and not just reducing power when he had wheel hop?

ctsvflorida
03-05-07, 11:31 AM
Question for the engineers: How much pot do you guys smoke! :histeric:

Please send me some of that good stuff to:

Jeff Spicoli
100k At Me Dude rd.
Woodstock, NY 12498

BigEnos
03-05-07, 01:00 PM
Wouldn't designing a system to react to wheel hop make it basically useless? Once the wheels hop it's already too late.

You are better off adding traction than you are restricting power.

ctsvflorida
03-05-07, 04:10 PM
Wouldn't designing a system to react to wheel hop make it basically useless? Once the wheels hop it's already too late.

You are better off adding traction than you are restricting power.

You actually answered these guys seriously? C'mon Noobie, I'll take you under my wing! You're now in 'GOOD hands'! :thepan:

BigEnos
03-05-07, 04:38 PM
You actually answered these guys seriously? C'mon Noobie, I'll take you under my wing! You're now in 'GOOD hands'! :thepan:

Ahhh, you're right! What was I thinking?!?!?

Next time it'll just be random insults, promise! :banana:

TrazzNJ
03-05-07, 05:05 PM
Question for the engineers: How much pot do you guys smoke! :histeric:

Please send me some of that good stuff to:

Jeff Spicoli
100k At Me Dude rd.
Woodstock, NY 12498

Now that is funny S#&T.

They are all kidding right. These aren't real people actually thinking about what they are saying...is it???
Bri, If we smoke more will we understand???

:yeah:

TrazzNJ
03-05-07, 05:10 PM
You actually answered these guys seriously? C'mon Noobie, I'll take you under my wing! You're now in 'GOOD hands'! :thepan:

I should have read all the way down. It just keeps getting better!!

kgoch
03-05-07, 05:23 PM
The Speed GT V's don't have wheel hop, and they have the same rear suspension set up we have. My guess is they have launch control along with better shocks. There is no reason, with the software these cars have, that they could eleminate the wheel hop with software launch control.

ctsvflorida
03-05-07, 05:29 PM
Ahhh, you're right! What was I thinking?!?!?

Next time it'll just be random insults, promise! :banana:

BIG: I just break ballz in instances where 'I' believe it warrants it and probably in instances where I should shush but c'mon now, this is ridiculous, and in my opinion. warrants it more than any other time! You said it right about getting the power to the ground...not restricting it. :thumbsup: It all seems soooo silly to me and Trazz as you can see!

...and yes, random insults are good! Even if you're insulting me...I can take it! :thepan:

BigEnos
03-05-07, 05:51 PM
The Speed GT V's don't have wheel hop, and they have the same rear suspension set up we have. My guess is they have launch control along with better shocks. There is no reason, with the software these cars have, that they could eleminate the wheel hop with software launch control.

Yeah I'm sure the World Challenge "V"s have the "same" suspension as your car. Whatever helps you sleep at night, man.:thumbsup:

kgoch
03-05-07, 06:06 PM
Your name says it all. Maybe you should read the Speed World rule book.

NoSlackCadillac
03-05-07, 08:27 PM
The VRs have a modified rear suspension.

You can get rid of wheel hop by using the Engine Torque Managment tables of the PCM. I am putting down some pretty good numbers and was having significant hop even with KARS III.

I took it off and limited the torque produced in 1st via the PCM. No hop.
The problem with this approach is finding the limit. How much torque do you allow? Traction and actual performance of the car change in just an hour at sunset.

HiTechRV
03-05-07, 08:54 PM
Same principle except you do not need to limit it unless the rear is coming down too hard, pre-hop. If you do start to start a hop upstroke, you want to stop limiting torque to damp it.

All you need to do to deal with the inertia is time phase the correction. It's not a random wave form - you start the correction ahead of time. This is really trivial controls stuff.

NoSlackCadillac
03-05-07, 10:23 PM
Unfortunately, there is no feedback loop in the PCM that relates to the hop.

I figure my best bet is to limit initial torque to prevent the "self-unloading" of the rear and then add torque as rapidly as the traction and suspension will allow.

The best part of doing it this way is that it is easy to get repeatable performance. No feathering the throttle, just floor it and the PCM opens at the predetermined rate.

TrazzNJ
03-05-07, 10:27 PM
O----MY----GOD!!!! This can't really be happening!!!!!!!!

SOMEBODY MAKE IT STOP !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


:horse:

BigEnos
03-06-07, 12:12 PM
Your name says it all. Maybe you should read the Speed World rule book.

I did. It says that pickup points may be reinforced and moved, bushing can be replaced with any material, spindles may be "adjusted", arms may be reinforced, bushings/shocks/springs, and strut mounts are able to be slotted.

So, pickup points, arms, struts, shocks, springs, swaybars, bushings, and spindles can be changed. But you're right, it's the same. :bigroll:

BTW, you can call me "Biggie" :cowboy:

ctsvflorida
03-06-07, 05:31 PM
I did. It says that pickup points may be reinforced and moved, bushing can be replaced with any material, spindles may be "adjusted", arms may be reinforced, bushings/shocks/springs, and strut mounts are able to be slotted.

So, pickup points, arms, struts, shocks, springs, swaybars, bushings, and spindles can be changed. But you're right, it's the same. :bigroll:

BTW, you can call me "Biggie" :cowboy:

That's my boy! lol