heavy85
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Posts posted by heavy85
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IME wheel hop is a ***** to get rid of. Even poly suspension mounts hop. To finally eliminated it I has to make some stiffer UHMW bushings, stiffer diff mount, etc. Wheel hop will definitely tear up stuff. Gear ratio is also important. I ran 3.7 for a couple years with zero problems with the stock half shafts behind a T56. The higher the ratio the more torque you can put through the shafts. Finally, as Jon mentions suspension travel is important. The higher the angle the shaft has to work the more stress you are putting through it. The devil is in the details and IMO there are many details involved. As others have said the Nissan stuff is not too bad if set-up well.
Cameron
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If you plan to race competitively and are concerned with weight distribution then as far to the right as will fit to offset the left heavy bias that inevitably happens with the driver. If it's just a street car it probably doesn't matter and do what's easy. I think mine is offset 3/4". Everything fits well but I'm still at 51% left side weight so it could stand to go over even farther if it would fit.
Cameron
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and I still think you might be undersprung.
If you're still wearing the outside of the tire, I would say more neg camber or stiffer springs. Getting the tires flat midcorner is the name of the game. Are you taking tire temps?
Im not too concerned with the tire wear in and of itself but its telling me that it may be camber control thats needed to help the center off push. Agree with flat mid corner. Already at 3.5 deg camber and 425 lb on street tires. Sure seems like geometric camber control is where I need to focus. So instead of springrate add track width and instead of more static camber add caster. I used tire temps when I first started running these tires but that was two years ago and I didnt take any temps this year. Need to take them again as I have already made ARB and aero changes since I last measured. When measuring camber curves I also noticed I only have 2" of bump travel before starting to kiss the bumpstops (Koni foam ones) so I definitely need to cut then down another inch.
Cameron
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Bumpsteer spacers negatively affect camber gain in bump. If you want to get a better negative camber gain as the suspension compresses then remove the bumpsteer spacers.
Now I'm confused. I always thought but never tested the opposite. So I just measured it at ride height, +1", and +2" of bump travel.
w/ 3/4" 'bumpsteer' spacers camber changed -1 deg (-1" ride height) then - another 5/8 deg (-2" ride height) - Note 1/8 deg tolerance. LCA started 5 deg pointing down and ended 4 deg up - NOTE 0.5 deg tolerance.
W/out 'bumpsteer' spacers camber changed -7/8 deg (-1" ride height) then - another 5/8 deg (-2" ride height) - Note 1/8 deg tolerance. LCA started 1.5 deg pointing down and ended 8 deg up - NOTE 0.5 deg tolerance.
From my quick and dirty measurements camber gain is within tolerance the same with and without the spacers. So what's the real value of the spacers in adjusting roll center? My theory is I need as high roll center as I can get because with 25" tires need all the lowering I can get. Is there something I'm missing? To be honest I've never tested without them but want to make calculated changes.
The problem with increasing caster and widening the track is that you're increasing scrub, which slows the car down - so you have to compromise on track width and caster. ...Not an issue for a 400hp 240z.
I am planning on longer LCA instead of wheel spacers to avoid adding scrub. Yeah I'm closer to the latter (365 whp) so scrub is not a big concern in terms of losing momentum.
Cameron
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That's a good direction to go. Also, try removing the bumpsteer spacers and correct the bumpsteer in a more traditional way. If you increase the front track and get more caster you can soften the rear springs by 25 to 50 lb. in.
I have the 'bumpsteer' spacers installed to raise roll center not for bumpsteer control. Rod end with shims on the tie rods are used to set bumpsteer. Why would you remove the spacers as that just lowers the roll center? How much track increase is meaningful - I'm thinking 1/2" to 3/4" per side but thats just a swag I pulled out of the air? Caster at ~7 deg?
Cameron
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I went both directions. Started with prelared lines from the farm store then cut one end to length and reflared that end. The cheap tools from Autozone arent worth your time as they dont work well and strip out. Replaced with a kit from NAPA ($100ish if memory serves) and it makes much better flares.
From my limited experience either it leaks right away when you bleed the brakes or it seals good and doesnt have a problem.
Cameron
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Is it actually reasonable that increasing the roll stiffness can add grip by reducing camber loss? That is, assuming a somewhat softly sprung car to begin with.
Dont know anymore but many moons ago the hot stock fwd autox setup ran huge front bars even though they were front heavy. Rules limited spring & rear bar changes so front was all they had to work with. Theory was the improved camber control due to limiting roll was the dominant factor and produced the best lap times.
I'm starting to think my car (240Z) is limited by camber control more than anything. It's running 425F / 375R springs, stock front bar, no rear bar, front inner pivot up 5/8", front 3/4" 'bumpsteer' spacers. Went to stock front bar this year as the big front bar had braking issues where it would want to lock the inner front unless braking perfectly straight and it tended to push center off. 3.5 deg camber up front and 2 deg rear on RS-3 street tires and I'm still wearing off the out edges and while some better it is still pushing corner off more than I would like. This is on road courses too not tight autox where one tends to abuse the edges more. It's still quite fast but lays over more than I think it should to produce highest possible grip. This is actually my biggest goal for the winter off-season to figure out and build whatever I need to make some gains here. I'm thinking more track width and more caster (from just over stock now) is the starting point but am still very much in the early planning stages and open for discussions.
Cameron
PS - finally getting around to re-read Carroll Smith's 'Tune to Win' again (last time was ~15 years ago) and highly recommend it as a very readable, insightful book that's still relevant 30 years after it was written.
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Stumbled across this old thread and in case anyone is interested here is the 2012 update.
Ran High Speed Autox season again (single timed lap on a full racetrack - no cones) with the Midwestern Council of Sports Car Clubs and a SCCA hill climb down in North Carolina so it was a light year due to hectic life. After about 35 or so days on racetracks after previous years of low speed autox and kart experience I'm finally to the point of getting close to the full potential out of the car. Ended up taking 1.8 seconds off previous best lap time on our home track and scored two or three FTD still on street tires to boot. The car is really quite fast.
Here's thread on the hill climb - I was thrilled with the results http://forums.hybridz.org/index.php/topic/106904-hill-climb-set-up/page__p__1000354__hl__%2Bcameron+%2Bdragon__fromsearch__1#entry1000354
Continuing the theme here are lessons learned:
- Splitter dropped 0.5 seconds of 1:20 sec lap time but hurt cooling (actually done in 2011)
- Bigger wing + cam (guess +40 hp? to 365 whp) dropped another full second off laptime
- Splurged on scales and setting corner weights from 48% cross to ~50% cross dropped another 0.5ish seconds
- Down to stock front swaybar and no rear bar with same 425F/375R springs. Smaller front bar really helped prevent front wheel lock-up under braking. It's very drivable but need to find more mechanical front grip.
- True dual masters work much better than stock set-up
- Video showed the outer rear urethane bushings deflect a LOT as you apply power. UHMW bushings finally all but eliminated wheel hop and noticeably helped the launch.
- Making a car track worthy (brakes, cooling, aero, rollbar) adds weight so now car w/out driver and ~1/4 tank is right around 2,500 lb
- LS1 need dual catch cans and the LS6 valley PCV conversion doesn't do squat to oil consumption through the PCV system.
- Now starting to reach the limits of the OBX and getting a little wheel spin but it's pretty minor and workable. Would a pimp OS Giken diff help much?
- Hankook RS3 work really well with heat but suck in the cold so the internets tell the truth on something.
Now what for next year? Need to take weight out and figure out a way to get more front mechanical grip. Shooting for sub 2:00 run at the Dragon hill climb and what else we will see. Still going faster about each time so the challenge and reward is worth keeping advancing but am starting to get to the point of $$ just for the sake of going faster.
Cameron
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Since air rises I dont see how you are ever going to get the air out. Kind of like installing brake calipers upside down with the bleeder at the bottom ....
I used the speedway 18" or so and clamped it to the firewall pointed up. Actually when I first did the swap I only bled it from the master and it worked great for years. Then my niece kindly pushed the clutch pdeal when the engine was out and pushed out the seal so I installed one then to make sure there were no problems.
Cameron
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That explains it. My 240 only weighs 2500 lb with 1/4ish tank, 2730 lb with me. I typically race between 1/4 and 1/2 tank. If the other cars were 500+ lbs heavier then all bets are off as that weight could be anywhere. The thing with driver weight is it's mostly on the drivers side and rearward. If it were me I would still want the battery on the right rear to balance the drivers left side bias otherwise the right rear is relatively light. Also depends on intended purpose. Rear weight is good for drag racing - more the better, doesn't really matter for the street, and some is good for road racing / autox. I've often actually run faster with a passenger despite the higher overall weight and I believe that's due to better weight balance. I recently bought scales and am playing with corner weights and am finding they are SIGNIFICANT to lap times.
Cameron
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Pics would be great. I have already done what John said details and all plus hood vents. I was finally ok with cooling then the splitter actually seemed to hurt a bit then added the extra power and am back in not ideal shape. Is the ron davis custom or they make one to fit?
Thanks
Cameron
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bump - recommendations? I have a LS1 / 240Z. The stock radiator did OK for street driving and for all of about 1 1/2 laps on track. Switched to a Champion + improved airflow + oil cooler and it helped a LOT. Now added a cam and ~50 hp and am back to hitting 230 deg within about 3 laps. Want to upgrade again for next year and am just now researching options. Anyone with REAL world track experience? I'm at 365 whp.
Thanks
Cameron
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That is my understanding from all my research.
Dont know where that came from. My 240 w/ LS1 & T56 is custom mounted but approx the same fore/aft placement as the the John's kit & ~3/4" offset to the passenger side. I wish it was MORE rear bias as it's 51%F/49%R and that's with a full size Optima battery placed behind the passenger seat. Lack of rear bias is actually holding be back from going to a smaller battery as it would not do favors to the weight balance. It's also 51% left side so anything you can move to the passenger side and rearward should improve weigh distribution
I'm on the pointy end of road racing set-up so your results may vary but I do run a 'street' class so have full street legal trim (lights, glass, dash, etc).
Cameron
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That's awesome Cameron. Harold Knoebel is a multi-time national DMOD champion and you beat a host of other people in really fast cars.
Thanks - he's a character. 79 (?) years old driving the snot out of a HEAVILY modified Del Sol towed by an Accord with small front tires to get more favorable gear ratio for towing.
Didn't see your results, congratulations! Your videos aren't showing for some reason, would like to see them.
This you? I was thinking it might be when I first saw the picture, but you're not real close to the dragon.
http://www.facebook....&type=3
background here:
Yep that be me. Towing over the 'Tail of the Dragon' sucked. Hot smelly brakes on the van, 12% grades, 315 turns in 11 miles on the side of a mountain with zero guardrails, bikes everywhere leaning over the center line. When I edit the post the videos show up so dont know what's up with them not showing. They are on my channel (LS240Z) on youtube if you can find them
Congratulations on your finish. I'm hoping to run the Sept event and wondered what size tire/wheel combo you are running.I'm building a hybrid Z (old school 327SBC with carb).
I recommend giving it a shot! I'm running the Rota 17x9 and 17x9.5 group buy rims backwards (9.5 on the front) with 255 Hankook RS3 tires.
Go pro suction mount?
Yep. I've been experimenting with location lately and it's cool to see the various views and I even found a reason to build harder rear bushings. The rear tires change toe a LOT under power with poly outer bushings and offset inner bushing. Made some UHMW outers and it launches much better now.
Cameron
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http://www.ccrscca.com/results/ctd2_2012_raw.htm
Third overall and first in class. Was an awesome trip. Towing over the Dragon sucked but no issues other than smelly (hot) brakes on the van and grinding up the 12% at 15 mph foot to the floor in first. Beautiful country but remote with little to no cel coverage (disclaimer I have AT&T ....). The club is VERY focused on the workers and community involvement. There were spectators and shuttle busses, local 'sponsors' - I was the 'simple life campground' car which happened to be where we stayed. The road had really good grip but is a challenge since it all looks the same and is left right left right .... so it was hard to read and judge entry speed.
My best run. There is still many seconds to be had as I dont have the hill memorized yet despite hours of watching last years runs. I was however getting close to the steep part of the risk vs reward curve so much lower times will really have to push with little error. That's what next year is for I guess
I've been so focused on this event for the last several month I dont even have the rest of the season scheduled. Only problem is this makes other track events less meaningful. Time to find another event to add to then knock off the bucket list.
Here is one of the several photographers that were there.
http://www.photoreflect.com/store/th...aspx?e=8571076
Here's an in-car video that's a couple seconds slower but shows the course.
http://www.youtube.com/watch?v=rTR09...ature=youtu.be
Cameron
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Hillclimbs are probably the most fun thing I have done in a car. You may go faster on a track but the feel from a hill is something else. And when you're done and talking very quickly or foot won't stay still you'll know it was a good run.
That's why I'm willing to tow ~11 hrs to give it a try.
I'd look for vids on youtube and make sure to record your own. You can watch them at night to help memorize what it looks like at speed.Just make sure the car still drives after the event. At some point we all have a moment when pushing really hard.
Getting close to having the course memorized from last year's videos. It's fast ....
I'm really trying to NOT set a laptime goal to make sure it comes home in one piece.
Cameron
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Yep you guys have it. All low / medium speed, flowing with no hairpins or really tight stuff, not much of straights to speak of. All asphault and they just repaved the rough spots. Guess average speed will be ~70ish mph which isnt slow. I think Im just going to leave well enough alone.
Cameron
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So I'm planning for June hill climb in North Carolina - 'Chasing the Dragon' (it's near the tail of the dragon). My car is set-up for road coarse and I've never run a hill climb. Is there any set-up changes I should consider to make it more drivable at speed on a public mountain road? I realize practice and driver is the key factor but if there are any changes to make it easier to handle (i.e. safer and therefore more fun) I would like to be prepared and avoid frustration if I'm way off.
Basic info:
2675 lb race weight
Functional aero
364 whp / gear LSD
Hankook RS-3 tires
425 / 375 springs
1" (about to test 18 mm) front bar / no rear bar
1/8" front toe out
1/4" rear toe in
Thanks
Cameron
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I need to add wipers to my 240Z to be class legal. I have the stubs and mechanism and just bought wipers arms but dont have a motor. I was planning to just add a motor but the stubs are frozen and one broke tonight trying to free it so I need at least the stubs if not the complete mechanism and the motor. I will be running it from a switch so dont need anything fancy it just has to work at least decently. Really it's just to be class legal as this is a race car so as long as the wipers move I'll be OK.
Ship to 62521
Thanks
Cameron
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When the NASCAR COT first came out Ryan Newman flipped and they had to cut the roof off the get him out because of the lack of an FIA bar and a very long door opening. You might search and see if they did go back and add any extra bars. This is an extreme example with a much bigger door opening but maybe whatever NASCAR learned from it could help.
Cameron
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ah crap - I was looking at the pic wrong and missed a weld in there. It looked like the toe link had an extra pivot point in the middle like it could fold in half. Sorry I was just looking at it wrong.
PS - if you go back to that old original thread and I think I was the one who started debate with Jon about the needed degree of freedom to reduce strut bending loads as the thread was going to 'stiffer h-arm' is better so I know exactly why it's there was just looking at the pic wrong.
Carry on nothing to see here ...
Cameron
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If I ever decided to add a rear bar, I have a 3/4-16 threaded hole in the adjustment sleeve on the front portion of the arm where it attaches to the upright (see black arrow). It's located in the area where you would attach the sway bar link. I could easily make up something that would attach there and link to the end of the bar.
Mike Mileski
Tucson, AZ
I sure hope the toe link doesn't really pivot in the middle like it appears to?
Cameron
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Here's mine. It sounds just right.
Cameron
Roll Center Height/Roll Resistance
in Brakes, Wheels, Suspension and Chassis
Posted
What are you using?