NASA PT/TT thread
#151
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In case you guys weren't following the races:
PTC - 1st place - Dennis Holloway
PTD - 4th place - John Magnuson
PTD - 9th place - Lee Papageorge
Great racing on Sunday!
PTC - 1st place - Dennis Holloway
PTD - 4th place - John Magnuson
PTD - 9th place - Lee Papageorge
Great racing on Sunday!
#152
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Was a really fun race. I was leading for a bit but then had an odd problem that slowed me. Half way through the race I ran over some gators at the exit of a turn and it shook the rear view mirror off. As it was the stock rear view mirror it still had some wiring attached to it and was hanging suspended in the middle of the cabin at about shifter height. No matter what I tried or how I yanked I could not rip it out of the way or secure it. It kept swinging about the cabin and hitting me. On hard rights it would get jammed in front of the shifter and block my shifts to 3rd and I'd have to smack it out of the way and try shifting again. My rearward visibilty was a bit impaired as well as you could imagine. It was almost funny. I kept trying different ways to secure it but there was no real solution. Needless to say this was distracting enough that it killed my pace a bit.
Overall it was a great time. 3rd (or 4th) in PTD and 2nd in TTD. Car ran flawlessly the whole weekend. I was a one man team but literally all I had to do to the car all week was add oil, check air pressure and change tires. Nothing else.
We'll see where it is next year... they have not committed to Miller again at this point. I think they have a better turn out at Mid Ohio since almost nobody from the Midwest or East Coast will travel to Utah.
It seems the hot ticket is PT these days is a light weight highly modified miata that gets back tons of points for running skinny tires. I hope Greg closes this loop hole. There was a miata running like that that was 2-3 seconds a lap faster than anyone else.
Last edited by MagnusRacing; 09-10-2013 at 12:51 AM.
#155
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Join Date: Feb 2011
Location: Houston, TX
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hell there were even alot of CA people that didn't go to Miller, and that location was soley to throw SoCal and NorCal a bone after it being at Mid-O for so many years. 2014 and beyond hasn't even been hinted at from mgmt. I haven't been able to dig up any credible rumors either so who knows at this point...
That is certianly some adversity to drive through especially in a big race like Nats. Great work!
That is certianly some adversity to drive through especially in a big race like Nats. Great work!
#156
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Thread Starter
Link to the PT race: SpeedcastTV
#157
What do you guys recommend as the minimum fender lip to wheel center height for acceptable roll center migration? The springs that come in the ride rate I want (~1.5Hz, dual duty car) will drop the car ~1.1'' in the back and ~1.75'' in the front. I'm combining these with Koni Yellows, so that may be up to another 1/2'' drop over the stock Tokicos. It's hard to tell what the final height will be because my current shocks are blown and the front is preloaded up. I assume I can raise the car about 1/2''-1'' via bushing preload if need be, but that obviously has an effect on bushing wear and rates.
Current camber is around ~-1.5 to -2.0 all around and wear/heating is unacceptable. The car does have big bars (est 1.5-2.0 deg/g total including bushings). The LCA adjusters are seized but near maxed out. The UCA is offset all the way in to the chassis (and then some) already, so there's nothing to be had there. I'm hoping to get -2.5 to -3 all around.
Thanks,
Chris
Current camber is around ~-1.5 to -2.0 all around and wear/heating is unacceptable. The car does have big bars (est 1.5-2.0 deg/g total including bushings). The LCA adjusters are seized but near maxed out. The UCA is offset all the way in to the chassis (and then some) already, so there's nothing to be had there. I'm hoping to get -2.5 to -3 all around.
Thanks,
Chris
#160
Do you have a rough value for the rear as well? The front is currently 15'', so it's going to be tricky to keep 13.5'' with ~2'' expected drop from the springs and shocks. Has anyone heard of a spring spacer for this car? Something between the perch and first coil...
-Chris
#161
Link to the PT race: SpeedcastTV
Last edited by yomomspimp06; 09-12-2013 at 02:59 PM.
#163
Thanks. The UCA is already offset and the LCA is seized.
Do you have a rough value for the rear as well? The front is currently 15'', so it's going to be tricky to keep 13.5'' with ~2'' expected drop from the springs and shocks. Has anyone heard of a spring spacer for this car? Something between the perch and first coil...
-Chris
Do you have a rough value for the rear as well? The front is currently 15'', so it's going to be tricky to keep 13.5'' with ~2'' expected drop from the springs and shocks. Has anyone heard of a spring spacer for this car? Something between the perch and first coil...
-Chris
13 inches is going to be very low. I found 13.5 (front and rear) to work well on track, and get the needed camber without any aftermarket bushings, but it is a little low to get over the speed bumps in my work car park, or up my driveway. 14 inches worked well on the street, but not quite enough camber on track. I'm now at 13.75 and it is good enough on the street. Will see how it does on track in a few weeks.
Have you ruled out coilovers? I know it is likely to be significantly more expensive than shocks + springs, but I am really liking my fatcat setup. With that, you can pick your spring rates and ride height front and rear and get shocks specifically valved to match them. I'm pretty sure you could go up to 1.8hz and still be comfortable on the street. I am at around 2Hz and still drive the car every day. I would not want to go any stiffer than my current rates, but at the same time, I am not regretting those spring rates and at lower speeds I think it is actually more comfortable than stock. It is over freeway dips and rises where you feel the higher spring rates.
#164
My s2 sport had a front ride height of 15 inches stock so you are at around stock height right now.
13 inches is going to be very low. I found 13.5 (front and rear) to work well on track, and get the needed camber without any aftermarket bushings, but it is a little low to get over the speed bumps in my work car park, or up my driveway. 14 inches worked well on the street, but not quite enough camber on track. I'm now at 13.75 and it is good enough on the street. Will see how it does on track in a few weeks.
Have you ruled out coilovers? I know it is likely to be significantly more expensive than shocks + springs, but I am really liking my fatcat setup. With that, you can pick your spring rates and ride height front and rear and get shocks specifically valved to match them. I'm pretty sure you could go up to 1.8hz and still be comfortable on the street. I am at around 2Hz and still drive the car every day. I would not want to go any stiffer than my current rates, but at the same time, I am not regretting those spring rates and at lower speeds I think it is actually more comfortable than stock. It is over freeway dips and rises where you feel the higher spring rates.
13 inches is going to be very low. I found 13.5 (front and rear) to work well on track, and get the needed camber without any aftermarket bushings, but it is a little low to get over the speed bumps in my work car park, or up my driveway. 14 inches worked well on the street, but not quite enough camber on track. I'm now at 13.75 and it is good enough on the street. Will see how it does on track in a few weeks.
Have you ruled out coilovers? I know it is likely to be significantly more expensive than shocks + springs, but I am really liking my fatcat setup. With that, you can pick your spring rates and ride height front and rear and get shocks specifically valved to match them. I'm pretty sure you could go up to 1.8hz and still be comfortable on the street. I am at around 2Hz and still drive the car every day. I would not want to go any stiffer than my current rates, but at the same time, I am not regretting those spring rates and at lower speeds I think it is actually more comfortable than stock. It is over freeway dips and rises where you feel the higher spring rates.
I was originally looking for coilovers but decided the $750 koni+spring combo would give me rates, camber, and level of adjustability that I wanted for the time being. The impression I got was that the coilovers would be $2300-$3000 to guarantee the equivalent performance of Konis with well-matched springs. That said, the adjustability may be worth the added cost in the future.
Does anyone know the perch to perch distance at a given ride height? I had the springs tested and am looking at 1.5/1.7Hz F/R (330/320lb/in) at 1g vertical. I know the spring length, but don't have a conversion to ride height.
-Chris
#165
The rear sits at 13.75'' right now, so I presume the stock shocks are blown. 13.5'' sounds pretty reasonable.
I was originally looking for coilovers but decided the $750 koni+spring combo would give me rates, camber, and level of adjustability that I wanted for the time being. The impression I got was that the coilovers would be $2300-$3000 to guarantee the equivalent performance of Konis with well-matched springs. That said, the adjustability may be worth the added cost in the future.
Does anyone know the perch to perch distance at a given ride height? I had the springs tested and am looking at 1.5/1.7Hz F/R (330/320lb/in) at 1g vertical. I know the spring length, but don't have a conversion to ride height.
-Chris
I was originally looking for coilovers but decided the $750 koni+spring combo would give me rates, camber, and level of adjustability that I wanted for the time being. The impression I got was that the coilovers would be $2300-$3000 to guarantee the equivalent performance of Konis with well-matched springs. That said, the adjustability may be worth the added cost in the future.
Does anyone know the perch to perch distance at a given ride height? I had the springs tested and am looking at 1.5/1.7Hz F/R (330/320lb/in) at 1g vertical. I know the spring length, but don't have a conversion to ride height.
-Chris
I can try to get some perch to perch measurements off my car, but probably not for a few days.
With $2300-$3000 you should get better than koni performance. IMO, the koni's work very well at stock spring rates, but less well the further you get from those.
#166
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The OE ride height info encompasses a range and is listed in the service manual
just changing from the OE high pressure monotube shocks to Koni low pressure shocks (or no pressure for custom valving & other changes) will drop the car quite a bit all else being equal
this may not be what's in the current service manual, the attached are from a very early internet manual that had a lot of errors which were later corrected
just changing from the OE high pressure monotube shocks to Koni low pressure shocks (or no pressure for custom valving & other changes) will drop the car quite a bit all else being equal
this may not be what's in the current service manual, the attached are from a very early internet manual that had a lot of errors which were later corrected
Last edited by TeamRX8; 09-13-2013 at 04:32 PM.
#167
Yep, stock rear ride height was ~15 to 15.25 inches for me.
I can try to get some perch to perch measurements off my car, but probably not for a few days.
With $2300-$3000 you should get better than koni performance. IMO, the koni's work very well at stock spring rates, but less well the further you get from those.
I can try to get some perch to perch measurements off my car, but probably not for a few days.
With $2300-$3000 you should get better than koni performance. IMO, the koni's work very well at stock spring rates, but less well the further you get from those.
Team, I saw the charts you posted in the alignment thread. Very helpful to judge camber gain from a given ride height change.
Has anyone measured the pickup points? I can do it when installing the shocks if it might help everyone out.
Last edited by cwatson; 09-13-2013 at 08:12 PM.
#169
The car currently has slight understeer mid corner and okay on corner exit. The car is very loose on braking and trail braking and pushes at turn in. I suspect this has something to do with blown rear shocks.
These numbers do not take into account bushing or chassis stiffness. Assuming the bushing/chassis stiffness contribution is even front to rear, the FRC and LLTD will tend towards 50% from the values below, tending towards oversteer:
FRC = Front roll couple = roll stiffness distribution of bars/springs %F
LLTD = Lateral load transfer distribution %F
Stock (push, believe from poor camber with too much roll):
FRC = 69.6%F, LLTD = 65.3%F
Stock with drilled rear bar (neutral mid-corner balance)
FRC: 66.5%F, LLTD = 62.7%F
Current setup (progress tech):
FRC = 69.3%F, LLTD = 65.0%F
Proposed springs with stock ride height,roll centers, and same bar settings:
FRC = 65.2%F, LLTD = 61.6%F
Drop height 1.5'':
FRC = 65.2%F, LLTD = 61.2%F
Drop roll centers 0.5'':
FRC = 65.2%F, LLTD = 61.6%F
Adjust bars max understeer:
FRC = 71.0%F, LLTD = 66.5%F
Adjust bars max oversteer:
FRC = 62.6%F, LLTD = 59.4%F
So, assuming the under/oversteer line is somewhere around 62.5%F LLTD with the current alignment for these calculations, I should be okay by adjusting the bars. These numbers are sensitive to roll center heights, so I'll probably take the time to measure pickup points when doing the shock install.
Last edited by cwatson; 09-13-2013 at 11:41 PM.
#172
So, assuming the under/oversteer line is somewhere around 62.5%F LLTD with the current alignment for these calculations, I should be okay by adjusting the bars. These numbers are sensitive to roll center heights, so I'll probably take the time to measure pickup points when doing the shock install.
Also, be aware that the koni adjustments are not linear, and may not even respond the same shock to shock. That means lots of playing around on each corner, or setting them on a dyno if you want to hit a pre-calculated value.
I have posted some FRC numbers from my car using the FCM calculator in the sway bar options thread (under s1 susp & brakes). I have found balance to change slightly based on ride height (I suspect due to not having enough front camber at higher ride heights to compensate for the greater roll angles).
Whatever you go with I would expect you can balance it using different sway bars or settings.
^There is quite a range of adjustment available if you are prepared to swap bars.
#173
Camber with the lower height is definitely going to muddy the waters. The tires are currently wearing in a way that calls for a flip at 30-50% of their life.
Looks like you have done some research on this one... I don't think the suspension bushings are going to have a huge effect, but are you accounting for bump stop stiffness and engagement points?
Also, be aware that the koni adjustments are not linear, and may not even respond the same shock to shock. That means lots of playing around on each corner, or setting them on a dyno if you want to hit a pre-calculated value.
I have posted some FRC numbers from my car using the FCM calculator in the sway bar options thread (under s1 susp & brakes). I have found balance to change slightly based on ride height (I suspect due to not having enough front camber at higher ride heights to compensate for the greater roll angles).
Whatever you go with I would expect you can balance it using different sway bars or settings.
^There is quite a range of adjustment available if you are prepared to swap bars.
Also, be aware that the koni adjustments are not linear, and may not even respond the same shock to shock. That means lots of playing around on each corner, or setting them on a dyno if you want to hit a pre-calculated value.
I have posted some FRC numbers from my car using the FCM calculator in the sway bar options thread (under s1 susp & brakes). I have found balance to change slightly based on ride height (I suspect due to not having enough front camber at higher ride heights to compensate for the greater roll angles).
Whatever you go with I would expect you can balance it using different sway bars or settings.
^There is quite a range of adjustment available if you are prepared to swap bars.
I would like to stay off the bump stops if possible. I imagine they will be hard to avoid with the anticipated ride height and spring stiffness. I'm currently looking at just under 1 deg/g without the bushings. I believe the bushings will bring that number close to 2 deg/g based on the difference between my estimation of the stock setup and the real stock roll gradient (3.4 deg/g) as measured by Car & Driver. Steady state cornering on flat ground should therefore only require about 1'' of travel on either side. I'm working on getting some better information as to the magnitude of bumps/curbs (anyone have some Az data?) on a typical track. If the bump stops look unavoidable, I'll take some quick stiffness measurements using a scale and zip-tie the shafts to check for interference.
I still have the stock sways with drilled adjustment holes, in case this setup goes too far in one direction. The rear can be swapped at lunch or maybe between sessions. The front requires a little more finesse.
Measuring the pickup points will give us some better information about roll center movement under roll/heave/swb.
Setup 1A (66.7% calculated FRC): Slight understeer, front tires heat more than the rears leading to more understeer once the tires have gone over their optimum temps. The rear was well planted exiting corners under full throttle. The car would push slightly to start with and then more noticeably as the tires overheated.
Setup 1B (61.7% calculated FRC): Neutral to very slight oversteer. Rears heat up slightly quicker than fronts. Once the tires had gone over their optimum temps the rears would drift a few % more than the fronts exiting a corner full throttle in 3rd gear.
Last edited by cwatson; 09-15-2013 at 03:37 PM.
#174
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until you actually start testing it's all just going on and on about guesses. Nothing personal mind you, just that once you start testing then you have a feasible reference point from which to start make some meaningful decisions & discussions on where you are vs. where you need to be.
In my experience, based on the calculation system you're using, the LLTD is low in relationship to *reality*, which is what generated my oversteer hunch. But you will only find out what's what once you start actually doing something more than shuffling paper. Without real world data results the preliminary calculated guesses and long ramblings regarding them doesn't serve any useful purpose. The numbers out are only as accurate as the numbers in and how the calculating system is handling them (pun intended).
In my experience, based on the calculation system you're using, the LLTD is low in relationship to *reality*, which is what generated my oversteer hunch. But you will only find out what's what once you start actually doing something more than shuffling paper. Without real world data results the preliminary calculated guesses and long ramblings regarding them doesn't serve any useful purpose. The numbers out are only as accurate as the numbers in and how the calculating system is handling them (pun intended).
#175
BECAUSE RACECAR
iTrader: (10)
Well I think I landed on what configuration I'm going to use for TTC... little less aero, little more tire.
Keep in mind I'm also trying to stay competitive in a Time Attack series that I will have another tune for where the only real rules are DOT tires and 15.0 or above power to weight, so there will be a couple compromises in TT but I think I should still be able to win. I don't ever really plan on going to nationals so if I can win regionally then that's cool.
TT-D* Base Class Aiming for 200-210WHP then I will ask for a weight.
+7 for one * in base class
+10 Tire Compound (Hoosier R6)
+7 Tire Width (275/35R17 on 17x10" RPF1)
+3 Shocks
+2 Springs
+2 Sway Bars
+3 Splitter
+4 Rear Wing
that's 38 out of 39 points. The last one I can use to either cut up the rear bumper or put on vortex generators, either of which will probably yield negligible gains...
Keep in mind I'm also trying to stay competitive in a Time Attack series that I will have another tune for where the only real rules are DOT tires and 15.0 or above power to weight, so there will be a couple compromises in TT but I think I should still be able to win. I don't ever really plan on going to nationals so if I can win regionally then that's cool.
TT-D* Base Class Aiming for 200-210WHP then I will ask for a weight.
+7 for one * in base class
+10 Tire Compound (Hoosier R6)
+7 Tire Width (275/35R17 on 17x10" RPF1)
+3 Shocks
+2 Springs
+2 Sway Bars
+3 Splitter
+4 Rear Wing
that's 38 out of 39 points. The last one I can use to either cut up the rear bumper or put on vortex generators, either of which will probably yield negligible gains...