second half is up

http://www.youtube.com/watch?v=eEkrIEixEuQ

get to see the car compared to a couple of Z06 Vettes, 1 C5 and a C6. The black C6 has similar HP and a bit more torque so we have similar speeds in the straights, I have a slight advantage given my lower weight (around 600-700 lbs lighter).

I need to go to the slightly taller rear tire I think as I am hitting redline @ 110 mph in the short straight and just letting off but could run it out a bit more with a bigger tire. Get rid of the understeer and I could go thru T1 a lot faster as well.

Do you have a clutch type LSD?

yep. Ever since I went to LSD from open diff I had understeer, so I added the rear bar. Unfortunately just not enough bar, then had to disconnect it altogether.

As I see it, track cars want a slight bit of understeer.....a tail happy track car could scare the weewee out of a guy.....unless you're a drit track specalist.

Clutch type LSD keep the rear tires spinning at the same rate up to the clutch-unlock rate.....equal means straight ahead....I know, I'm telling you stuff you already know. I avoided this with a TB diff, but "they" say TB diffs don't work well
in high HP applications.

I don't know enuff to offer much good advice and certainally not a cure. I suspect that you will have to tune to get the car to a workable understeer on sweepers and live with what's left on the tighter stuff.....unless you are a Steve Kinser wannabe. Then again Mark Donahue put a locked diff in all his cars.....even where it wasn't strictly legal.
There is a clutch pack there is clutch packing

Tim,

Terry and I went through the same thing; good balance with the open diff to understeer with the LSD. Adding a rear bar got us a lot better. I think he can now go with a slightly softer rear spring rate, but we'll test first before changing.

Are you gonna get another shot at a track day before the winter hits CO?

I wasn't there, but I'll give it my best guess. I think I might go with your assessement of stiffer rear springs depending on how the rear of the car behaved. I'd be inclined to go slightly stiffer (and adjust shocks accordingly) if you need more control over the chassis in the rear. Otherwise, I might opt for a stiffer rear sway bar complimented with softening up the front just a little bit; perhaps a softer sway bar setting, and/or less dampening depending on the spring/shock. JP's right in that you don't want it tail happy, so you need to sneak up on it a bit at a time; but as I said, it's all a best guess. You know me, test and adjust and test and........

Too bad you're in CO; today's high in SoCal (Valencia) is forecast for 90 degrees, so winter is nowhere in sight.......yet.

Andys

I just want to get it so I can get it loose with my right foot, but I certainly prefer high speed understeer and it is why I left the wing on (I was going to leave it off at one point but last minute put it on again).

The Mendy only had a clutch type diff available - I asked about a TB diff but they didn't have that option on the S4 trans.

doubt it - but who knows... there are days that it will be 70 deg in Jan for instance, it just has to miraculously coincide with an open track day.

given how much motion I had at the rear and the fact I reduced the frequency value I calculated to based on the Penske tech recommendations, I am going to increase the rear spring rate based on what the car was doing. I obviously won't throw the existing springs away so if I find it affects my ability to plant the throttle out of a turn I will swap back and swap sway bars and put the stiffer one in the rear. Car was pretty flat watching the vids so I think my sway bars are about correct for what I want to do.

I definitely sneak up and specifically set the rear bar soft and the front bar stiff just to hopefully guarantee a start with understeer - oversteer on these cars tends to mean spin - it has to be very slight - so I too try to start under and tune to neutral with on-throttle oversteer which is quite manageable. Just gotta get there

And the more I think about it, those guys standing by Ken timed me at 2:02 and you can see me having to pass traffic that lap... I don't think I ever had a clean lap once I was running my timer (different topic altogether but it double clicks so I have to add two times together and I have to worry about consistency of the second click across the track in the back straight)... it is totally possible the car is faster than that already! I hope so, it feels fast as hell, and they got the black Z at 2:08 and I was gaining on him pretty quickly each lap, probably quicker than 6 seconds difference (tho' who can say how clean his laps were, but that is cooking for a Z06 so he had a good lap there). And the caution was out nearly the whole session with that white Porsche cup car.

The car, on paper, should be good for 1:55s I would think and I suspect I can get there with tuning. Here are some results from groups that I follow for a good comparo since you guys have no way of knowing if 2:02 is fast, slow, or sorta

Rocky Mountain Vintage Group - I look at the big bore group as that is all the vintage Trans Am cars and typically where the Porsches run as well. Porsches prepped by 3R can be pretty darn fast and I have yet to see one clear the 2:00 mark, but they get real close-like. Oh yeah, be careful, you have to watch what track config they run, the full track is 2.55 miles and they sometimes to the shorter 2.0 mile version

http://www.mylaps.com/results/showevents.jsp?org=140

• Oct 3rd enduro, fastest lap of all cars = 2:02.872 I don't know what car model that is as I don't know that driver combo.
• Oct 2nd was qualifying on the short course, no comparo.
• May 16th Ken Petrie clicked off a best of the weekend of 2:00.891 in his big block 2nd gen Vette. That dude is seriously fast and a champion driver and holds most of the RMVR track records, has Formula 5000s, etc. I should be able to beat that Vette. Note there was a faster car at 1:53.305 - that was a Lola or similar if I understand correctly that was thrown in that group. If I could run with him I would be stoked! He ran a 1:57 in qual and got faster, so did Ken, so me thinks Sunday was best weather/conditions

SCCA stuff - again, watch the course length... July 3rd was 2.0 miles, the 4th was 2.55 miles
http://www.coloradoscca.org/results/201007...ainsRaceway.pdf

• Note that a GT3 Cup guy ran a 1:55.911
• Pettiford ran a 2:00 in his Solstice T2 car.
• Mike also ran a 1:57.968 in his C6 Grand Sport in the Sept 4th national event and I was there that day... he failed to qualify, started dead last, worked thru the whole group, then went on to lap the whole group in the session! Awesome driver and took 3 nat'l championships AGAIN that weekend (twice he has done it and the only guy to win 3 classes in 3 cars, let alone twice, in SCCA - amazing driver

I need to be running at the 1:55s to make all this effort worthwhile

weather has been in the 50s with no snow, and I was able to pick up 8 sets of Hyperco springs from a fellow Porsche racer late Wed night, so I bumped up to 1500 lb/in rears on Thursday, replaced a torn CV boot and rescaled the car, loaded up yesterday afternoon and hit the track today. Drove in heavy fog and cold until I was 5 miles from the track and literally the wall of fog disappeared and the sun came out as I pulled in The gods wanted to see some Porsches running today. I would say that by noon it was sunny and somewhere around 55-60 degrees (supposed to be 58 today and it felt like it).

Still have bad understeer, tire temps showed the fronts 25F colder than the rears and I need a bit more camber all around, but the car was running great and I ran a few 1/2 hour sessions, with my last tank of fuel around 2pm. The Cup car that broke the last time was back out there also - owner was a pretty cool guy. I was running right with him, another guy claiming he was faster than he was (told me he was running 55s... not true but nice guy nonetheless), and Mike Pettiford was running his Vette right at his SCCA T1 record just in front of me with high 1:57s to low 58s.

My best time 1:58.18 with consistent mid 58s to low 59s. In the top four cars today for sure, and it is amazing what shows up to HPR on open track days. At least 5 Porsche track cars, another two GT3 RSs, a Gallardo, Vettes, etc.

Good news is I picked up a full four seconds just going up 100 lb/in wheel rate in the rear I had been running 59s but figured out how to powerslide the car in the slow turns to overcome the understeer and picked up the other second.

My friend came out that is also a vintage racer which makes life so much easier - he was able to get tire temps for me the correct way in the hot lane, and pressures, etc. so I have a good game plan going forward. I was going to swap the sway bars today but was just enjoying the car too much and burned thru 30 gallons of fuel in 3 hours.

I had my GoPro HD cam setup but haven't viewed the footage yet... sadly it was off when I came in from the last, fastest session so I think I filled the card and am hoping I at least got some good footage following the cars I mentioned above before that happened.

Next iteration is to swap the sway bars, go to -1.0 deg front and -0.8 deg rear and I suspect I can tune the car in from there.

I love it when a plan comes together.

...well let's hope my future plans have similar returns! Picking up four seconds with a spring rate change and getting more used to the track is promising.

After taking forever to process, then have it take almost forever to upload to YouTube only to fail at the end, then reload again, I finally have the fourth session up online. Eesh. It does have a 480p max, I am not going to bother with trying a 1080p again.

http://www.youtube.com/watch?v=SliMdISeDmI

Not the most exciting thing you will ever watch So bummed I didn't get my next and last session on vid (my 8GB card is clearly not enough so I need to bring a spare) as it would be much more exciting as the two Porsches at the beginning of this vid, the SCCA T1 Nat'l Champ and I were out there really working thru the traffic and having a good time. All four of us were the fastest fendered cars on the track and running within 1 second of each other.

Hey Tim,

When I read your post, I have the same thought as Andy. We had developed the chassis by stiffening the rear and got it GREAT, but then I had hopeless inside wheel spin coming off corners.

I installed the Quaife Diff and went right back to UNDERSTEER! Andy pushed for a rear bar and after making one, WHOA, I had a car that would point AND put the power down. It was a "big swing" change and the first outing was way too oversteery. While I could drive it, I had to be "up on the wheel" to stay ahead of the loose condition. There was NO place to relax at the wheel and a few scary moments.

Now I 'm set for my next event with slightly SOFTER rear springs and my Big Bar. I believe the car is now in the right range to make final adjustments to achieve PEFECT HANDLING! (or at least, That's the story I'll tell)

Best of luck, your car looked SO good on-track. Dontcha' LOVE blowing off 'Vettes?

Terry

well, don't know about blowin' off all the Vettes, Pettiford's T1 Vette is still faster and a heavier car, so I need to beat him to be able to feel I can blow by all the Vettes What would be fun is to run with the Cup cars, that would be really fun as those cars are truly fast cars. Specifically if I can do it with a car at about half the price tag.

Talked with my good friend that has raced for a long time and talked about my tire temps, camber, etc etc and it is always good to have a resource like that to bounce ideas off of, so I have a game plan for sure. 4 day weekend coming up so may mess with the car this weekend to be ready to roll out if the weather continues to work out well. He also mentioned a word I had forgotten about a bit but as soon as he said it, I was reminded I was concerned about it since the tube chassis was built and the rack was moved - Ackerman. It would make total sense that the car has turn in and mid corner issues on the tight turns like I am seeing if the Ack is outta whack (whoa, that was a Johnny Cochoran moment there!) and I believe it to be so and have threatened to relocate the rack.

So I am going to mess with the other items that are just adjustments, no fabbing, and see how the car reacts. If ultimately it wants to persist, then I know I need to relocate the rack.

What is your ackerman? You can use ackerman to generate more slip angle in the front tires if necessary. Need to see where you are, 100% is way to much, you might try for almost none and see how the car does. Also, do you have any roll steer in the front? What kind of caster curves are you running? Caster will transfer weight diagonally across the chassis. You could be unloading the front tires in a turn.

Tim,

Thanks for the video; that was fun to watch. It looks like you were having fun in the cockpit as well. You should be proud of your results after so much work.

The understeer was very evident, as you pointed out. There's just no way to get a fast lap when the car doesn't want to turn. I'd wager you'll pick up a couple of seconds just by getting rid of that understeer. Judging by the video my guess would be you need more than some subtle adjustments to get where you need to be. I wish I was there, but then I would've been wanting you to change xyz and being a real PITA :-)

On the Ackermann issue, I just sort of assumed you worked all that out in your design; if not, then by all means do plot it out and adjust accordingly assuming you want to start at normal Ackermann.

Andys

This 914 > * .


Wayne's world not worthy moment.

thanks ghuff

I haven't measured the actual Ackerman values but can say I know there is too much as I have turned the tires on a smooth garage floor, pushed the car and have heard the inside tire squeal, which means too much. Not an exact science but when I started questioning Ack before I did that as a test. So when I get into these tight turns and have the wheel really cranked around the inside tire is leading way out and then just scrubbing v. steering so the outside tire has to carry everything.

I did not move the rack with the new suspension design and figured I would start with what I have and see how I want to make new mounting after running a couple days. I need to relocate the rack up as it is (I am running spacers to get the bump steer down to essentially zero which answers that question) so I am going to work on making new mounting bracketry so I can relocate the rack fore and aft to tune to whatever Ack works for the track. Just need to add a slip joint into the steering arm so I can move it back and forth at will.

In the meantime (and this is likely where you are going Brett) I am going to go to toe-in settings on the front instead of toe out - that would have the effect of bringing the inside wheel in and the outside wheel in as well, essentially countering the Ack affect for now. I can also add toe in on bump to get the outside wheel to turn in dynamically. Having no bump steer as well as toe out static settings is exacerbating the Ack issue.

You don't want toe in on turn in. That will make the car hard to drive. You want toe out. Toe out will keep the car from turning more than you ask it as it rolls into a turn. Roll steer out is more predictable and easier to drive. Obviously you don't want a lot of it, but just enough.

I would agree w/ toe out if the Ackerman is not an issue - having too much Ack the inside tire is turning in too much compared to the outside tire so by running toe in v. out I am bringing the inside tire back in, as well as, turning the outside tire more into the turn, attempting to cancel the over-affect of too much Ack. Keep in mind these changes are all small, not like I run 1/2" of toe out It is just something I am thinking of trying in the interim... if I have a gain then I know I have an Ack issue for sure.

Hay Tim, this is not strictly on topic but I have a question.

Are the louvers in your hood the sole venting for your radiator?
Venting out the hood looks like the cat's ass and since the shitbox is going water cooled next season, we're trying to finger it out. Brit has sourced the louvers. Anythng to watch out for? The radiator itself is 14 X 18 and my eyeball says your vents are big enough to do the trick......what size is your pannel? I dunno shit about water, cept it's good to drink but in excess, it will kill ya.

the louvers would be the main source of venting, but I haven't sealed the back side of the radiator shroud to them so air can get out elsewhere but they are the primary source. I had a lot of heat in the cabin before and it has helped a ton to have the louvers. The nice thing is that as air travels over them it helps to suck the air out. Every other way for the air to get out should look like a higher pressure area to the hot air.

Mine are the "wide" Genesis louvers.
http://www.hrpworld.com/index.cfm?form_pro...;action=product

I have threatened to make a simple box to seal up to the louvers to reduce in cabin temps a bit more but just haven't done that yet. Lazy

For any sort of Suby conversion they should be more than adequate. The openings are 0.75" x 8.5" approximately and there are five per piece.

little update - swapped the sway bars (thicker wall one in the rear now), added some camber to the front and went to toe-in since the last track day. Messed with tire pressures a lot today looking to get some heat and some grip (it was 49 deg peak today around 1pm) and the max tire temps I got were only around 135 deg at the core on the best lap.

Good news is I managed to pull one clean lap and get the best time yet of 1:57.9. There was a fair amount of traffic today since anybody with a V8 or roll bar somehow assumes they are good for the "fast" group but there were some fast guys, couple GT3 RSRs including the one from previous vids (that broke the first time) and I was rolling faster than him today, and a Cayman racer that was running pretty strong.

The rear was really skatey in some turns even tho' I still have have to power slide thru the tight ones to get the car to rotate but overall it was feeling pretty good. Not going to do any major changes going forward until I get good temp days, real temp in the tires, etc.

I hadn't seen the in-car video until now, but could tell you were having fun. Made me smile just watching.

If I remember correctly, your time was competitive with that fast Vette from the previous time out, so that's good news for such a cold day. It's difficult to make an assessement of what the car's doing in low grip conditions (where you'd otherwise want to soften everything up). As you say, you'd probably be best served to wait for that next warm(er) track day. Why you decide to go with toe in?

Andys

I went toe in to reduce the Ackerman in the turns. Even with toe in I had positive Ackerman on the front, to the tune of around 1/2 degree at my tightest turn on the track.

Tim:
A bit off the wall but need to know.
How tall are your hood louvers? SCCA solo rules allow 1 inch of height above the front hood for louvers. Since your louvered pannels are 150ish bucks a pop it would be good to know if we can make em' work.

The SEB just released a rule "clarification" for XP that threw a wrench in the werks.
As per usual practice it is pretty mindless. The old saw that says "You no play the game, you no makey the rules" doesn't apply here.

I think the key will be to mount the louvers from the underside, through the hood. This is how I mounted mine, and if you take a tape measure and measure from the hood surface and look across they louvers they are under 1" by a smidgen. It is a rough average of about 7/8", of course it varies as eye level/angle and molding tolerances mean it can move around a bit, but they appear to stay juuuust under 1" pretty much consistently if you mount them like that.

I think you should be okay unless you get a total JackA doing the measuring, which there is no rule that can work fairly with a JA enforcing it. I would be surprised if you had an issue if you are allowed a full 1". Worse case put a washer or two between the louvers and the hood on the underside and push the louvers down. Technically they will be below 1" from the top surface and you get the largest louver possible.

Thanks.
The Sheridan hood is around 3/8" thick out in the middle ....foam core/CF *I think*.
We won't really know till we start cutting. We wanted to make a duct to direct the hot air out away from the gas tank....but that's illegal . Looks like an air deflector is next best. If you have a Lotus Elite it is legal because they came from the factory with ducting from the radiator exiting the hood......hay, don't ask me, I just play the game.

Thanks for the info, I will get a pair of these on order.

BTW, I think you told me before but can you remind me...are yours the narrow or wide version?

Louvers

-Britain

for Britain. With a foam core hood you may be able to sand down from the top and create a pocket to drop the louvers into, then just bond them in and finish the edges with bondo/similar and make a nice smooth install, and also be able to create a pocket depth just right to get 1" total height.

some good, overall shots of the suspension while I am going thru the bearings. There were some requests for good, final shots and here they are. I have the front bearings fully replaced and hubs back on, the rears I got apart today but need to get bearings - should have them early next week. I will try to remember to get some rear shots with the uprights reinstalled.

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this shows the bearing spacers made by Patrick to use Carrera hubs with 914 bearings.
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awesome work!

OH NO....ROD ENDS IN BENDING!!

Just poking fun Tim. It looks great! Thanks for the pictures.

yeah, plenty of people like to freak out about rod ends in shear I have to admit, I did the math over and over again convincing myself it was going to be okay... and that is starting out knowing how difficult to impossible it is to bend 3/4" diam steel.

For integrity tho' and just a point of discussion if someone decides to use ends in shear like this, note the "jam" nut is really a full size, tall nut - this taller nut helps to both stabilize the rod end and also serves to reduce the length of the 3/4" section of thread which then increases the moment capacity.