SLC 24 Howard Jones

I think that engine is called "Voodoo".
They were having some oil related issues out there, with one making a large deposit in turn 9, of which Howard promptly went pirouetting in.
 

Howard Jones

Supporter
It's been awhile. The last installment ended with a melted throttle cable at Willow Springs, I called California Push Pull and Talked to the guy who does product development among other things and he suggested that I use a different cable than what I had been using. It is a different product and it has a 40 degree F higher rating (+350F) than the cable I had before. He told me that what had happened to the low friction cable that was installed and melted was the inter Teflon sleeve that is used to provide extremely low friction to the steel cable overheated. This causes it to shrink much like heat shrink tubing causing the cable to seize.

The new stuff uses a flat wound stainless outer sheath and a stainless center wire that is nearly as good from a low fiction system perspective but is better suited to high temperatures and marine use. The outer covering will melt at its rated temp but until it flows into the center cable sheath it usually won't seize. It's pretty much the same cost being about 10 bucks more for the custom cable I needed.

Then I went max insulation on the cable. Two layers of fiberglass cable insulation and two more layers of reflective outer sleeve. The two inter sleeves are first the 1/2 inch ID that was then covered with the 3/4 ID doubling the inter sleeve thickness. Then I slipped them both into a 1 1/4 ID reflective sleeve and coved it all with another 2 inch ID reflective sleeve.

Here is the stuff:



 
Last edited:

Howard Jones

Supporter
Ran COTA again last Sunday. The car ran generally well without any real problems. That's a first. I still have a vibration in the steering wheel under hard braking but it is better. I think I will need to turn the rotors and see if that makes it go away. I also have a minor oil leak from the front of the engine. Maybe a couple of ounces over the whole day. I still want to fix it and maybe I will pull the motor and have a good look.

But all in all a good full day without any real problems. Have video and I am working on it.
 
Last edited:
Ran COTA again last Sunday. The car ran generally well without any real problems. That's a first. I still have a vibration in the steering wheel under hard braking but it is better. I think I will need to turn the rotors and see if that makes it go away. I also have a minor oil leak from the front of the engine. Maybe a couple of ounces over the whole day. I still want to fix it and maybe I will pull the motor and have a good look.

But all in all a good full day without any real problems.
Have you got a short 3/8"unc bolt in the hole at front of block that goes thru to the mechanical fuel pump pushrod, that could be your oil leak. Try a bit more or less toe in at front to see if it kills the vibration.
 

Howard Jones

Supporter
Ya thanks Jac, I found that leak years ago. I am running 1/16 inch toe in on each side at the front. ??????
 
Last edited:
I enjoyed your video! You were idling through the essess faster than those other cars at full speed.
Do you think you'd benefit from a faster rack?
 

Howard Jones

Supporter
Well to be fair, that was the first session in the morning and there were several new to the track drivers there. The two straights are very fast and since I still seam to have a vibration as the brakes heat, I was leaving at least a hundred feet more than necessary in the brake zones. By the end of the day I was adding nearly full power at the apex of the slower corners and doing them in third instead of going down to 2nd. The thing is with my engine power (about 450HP) once the tires get up to pressure and are somewhat hot I can't spin them unless I'm in second and really try.

This car will always be a lot faster than I want to drive it. I just have to except that and stay in the fun zone. There is quite a lot of time left in the lap but to be honest I am very close to the fast end of what I call my "fun zone". I also am shifting at 5800. The engine part selection and balance spec should be safe to at least 6500-6800 with a max power curve peaking at 6300. So there is a lot left.

I tried a different pad material this time. Wilwood A pads were replaced with their B pad. Not much difference really. I am going to take the rotors off again and have them turned this time, maybe surface ground if I can get it done locally.
 
Engine sounds much better now with the cross pipe in there.
Looks like so much fun, congrats on getting reliable for a full day of activity.

Can't wait to be able to join you out there!
 
I tried a different pad material this time. Wilwood A pads were replaced with their B pad. Not much difference really. I am going to take the rotors off again and have them turned this time, maybe surface ground if I can get it done locally.
I don't know how relate-able this is, but we found the pad compound in our Sprint Cars makes a huge difference. We tried multiple brands and compounds and have settled on what works for us. We run the BP-40s in the back (main) and front (left) and when we run an outboard rear we run PolyMatrix Bs in it. I've found the claimed Wilwood compound characteristics to be spot on.
 

Howard Jones

Supporter
So last Saturday I did another open track day at COTA with Edge Adicts. I ran all 5 sessions and really didn't have any big issues. I had hoped to post another video but operator error seems to have struck and the memory was blank. Sorry.............

On another issue, I have figured out the vibration under braking thing. Since the last time at the track, I had the front rotors turned. I lathe operator was asked to only remove a minimum of material so as to expose the virgin surface. I think the max amount he took off was a bit less than 2 thou. In any case, the vibration is COMPLETELY gone. Not a hint.

I used the first session to gently bed in the pads (Wilwood B see chart below) on the new rotor surfaces and then began to add pace throughout the day in later sessions. The sessions are 30 mins so you get about 6-7 hard laps per session. I will tell you that at 150mph I was able to just about stand on the brakes and as the downforce bleed off begin to modulate the brakes to prevent lock-up. This was a hard technique to commit to and a big change from the sort of tentative adding leg as the car began to slow and to confirm complete control over a longer brake zone.

The best times of the day were around 2:38, a fairly brisk pace, with brake zone entry speeds above 140MPH and seeing 150 a few times on the back straight. I believe that there are 20s in this car but maybe not in the driver. These are "no bench racing" numbers.

I can say that times really come down when you take 50 and then a 100 feet out of the high-speed brake zones. In any case, the brakes really work well now.

The other big setup changes for this event were the spring rate changes. The front got the rears 800s an increase from the 650s on it before and the rear got new 900s. It was necessary to add two clicks to both compression and rebound on all four shocks. I think the shocks are getting near their adjustability envelope. There may be a shock valve tune in the future. I'm guessing but I think any more spring rate and the QA-1 are not going to work, at least in their stock configuration.

I left the anti-roll bars alone and didn't change their settings. I did feel that at the end of the SSes I was getting a bit of understeer but I will need to think about that at a later date. I am also very pleased with the ability to do my own alinements and being sure about what is on the car as far as settings.

Toe : F = in 1/16 both sides. Toe R = nearly straight ahead, biased towards in approx 1/32

Camber : F = -1.5. R = -1.25

Caster: both +5-6 best guess but the same on both sides. I want to really get this nailed down and calculate or measure where I am. I don't think that I want to change it but I would like to have the data in hand.

The steering ratio could be better (faster) at slow speeds and in turns of more than 70 degrees or so. I would also make the car easier to catch in an oversteer situation. As it is, once the car gets its tail out the car is much faster than the steering rack/ my hands. I work very hard not to slide the car around as a result. High-speed straight-line and 3rd - 4th gear fast corner feel is very good as is.

The car feels a lot better at high speed especially at the beginning of the brake zones. Before the spring changes, I was thinking that the rear of the car was being aero compressed and then destabilizing the front as the speed/downforce came down and the front responded to added loading resulting from the rear lifting. It just felt weird and now the car feels like it is much more balanced and stable from beginning to end under hard braking from 145-150mph down to 50 or so. A good change I think.

Lastly, It was a very hot day. Air temps were in the very high 90s and very little wind, full sun. I did get a vapor lock stall in the pit lane at one point and needed to open up the back of the car to cool it off for a couple of mins. Maybe cut some holes in the rear clam this winter. I still need to repaint the nose so maybe do it then and repaint the two clams at the same time. Water temps were good all day. 180-200F Engine Oil 200-220F Grbx 170-190F (no cooler)

So I hope this continuing saga of a "behind the curtain" look at a completely amateur attempt to build and develop what is really a homemade prototype is useful. The one thing I do know for sure is the car is never done. BUT you can learn stuff and do most of the work yourself if you just give it a try.

The journey continues........................................... I want to run the car at a much slower track with more slow corners next time.............and see what I see.
 

Attachments

Last edited:
I have tried the BP-20s and the A compound on the street. The 20s are way more powerful (awesome actually) than the As at high temperatures in my experience, regardless of what the chart says. Unfortunately, the 20s do not work cold, for street use it takes way too much leg to get them to stop in my experience. Although for sure, if I ever take my car to the track I will use the BP-20s.

Anyone have differing results to share?
Thanks
 

Howard Jones

Supporter
I took the car to Cresson Motorsports Ranch near Fort Worth a few days ago and ran the 3.1 mile track with Edge Addicts. This was their last event of the year I believe and it was well attended. Being one day it was a task to learn the track in a few hours given the elevation changes and many blind corners. It seemed like I was always trying to remember which way does this next turn go! After a couple of sessions, I took the offer of an instructor who was interested in a ride in my car and that really helped quite a bit.

By the last session (5th) I think I pretty much knew where I was going and started to build some pace. This track is not a high-speed track like COTA or WIllow Springs in Calif. I never needed to use 5th with my top speeds around 115MPH of so. But that was fine. It's a fun track and some of the up and down sections were really a blast. Lots of runoff and really nothing to hit. That's good because I did run off the end of a couple of short straight with blind corner entry at the end of them at very slow speeds (under 25MPH or so during the morning sessions.

The afternoon weather was perfect! The High was about 80ish F but the morning overnight low was pretty cold. I put too much pressure in the tires in the morning and since I was really taking it easy I never did get any heat in the brakes or tires until the second session after lunch. Then the pressure came up and I spun the car. At first, I was thinking a tire had gone down because it snapped so quickly and I really wasn't near the grip limit. I went back to the paddock to have a look and the rears had gone up to 35psi. No wonder it went around! Put everything back to 28 PSI and the car was really good after that.

This is a good track to compare to COTA in that it has quite a few slow corners. I am rethinking the steering ratio again. With tight slow corners, I was close to hand over handing the steering wheel and that just doesn't work well for me. Especially when the car quickly goes to oversteer if too much power is added in 2nd gear. In the end, I began just using 3rd. It is just a lot less drama and frankly not really slower anyway. The car will spin the tires with much more than 50-60% power in tight corners either way. In third it all just happens slower.

Changes:

1.The rear anti-roll bar needs another hole in the arms so that I can reduce effectiveness a bit at slow speed/no downforce. It is really on the nose as it is.
2. I counted the shock settings and the rears are about 90% of their full damping getting especially in bump. I/m thinking I might call QA1 and see what can be done.
3. The shifter (cockpit end) is getting sloppy. The hole that the for/aft main pivot shaft is using is getting opened up. Maybe a redo with much harder steel would be a fix.

Here's a couple of pictures:
 

Attachments

Howard Jones

Supporter
Since I was asked by another SLC builder about caster settings:

I went back and reviewed my setup notes and had a rethink about caster. Then I went out and did a quick front caster check. This is done by turning the steering wheel the same amount left then right and measuring camber at each point. Then so that it can be calculated the tire angle used should be 20 degrees in both directions.

for 20 degrees: left camber measurement subtracted from right camber measurement X 1.5 = caster

If you can't get 20 degrees you can use 15 degrees with a multiplication factor of 2.

So 15 degrees L - 15 degrees R X 2.0 = caster

I did this several times and came to the conclusion my SLC is set at about 5 to 5.5 degrees of caster on the front. It was pretty equal on both sides.

Now the question of the rear. I went back and did some reading and in Fred Puhn's book "How to make your car handle" he talked about rear caster on a trailing arm rear suspension. We have double A-arms but the point he makes still makes sense. Race cars usually use rear caster angle adjustment to compensate for and eliminate bump steer at the rear of the car.

Then I remembered that I had in fact had checked the rear bump steer on my SLC and could not produce any. At that, I left the A-arms mounting points alone. Looking at the upright it appears that the center of the top rod-end and the center of the bottom spherical bearing are very close to straight up and down or near 0 caster.

Fred Puhn also said in his book that the rear caster should be set to 0 as a baseline. So there you go.
 

Howard Jones

Supporter
So I did some more reading and thinking about the rear caster on a double A-arm versus a lower reverse A-arm and trailing links like a GT40. I think I am wrong in the above. With the trailing link GT40 setup everything is moving in arcs front to rear whereas with the double A-arm setup there is no forward/aft movement to change toe like with the GT40. Therefore I believe that setting the upright to straight up and down (0 caster) is more than likely the correct baseline setup. That's probably why my car seems to be fine as it is.

Does anybody have any thoughts on this?
 
Top