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Hi Folks - I've had some excellent offline discussions with reputable sources regarding a solid, low-budget, STU Build for C5 and thought I would share with you. The thought is for installation of those components which will shave off seconds to those which will shave 10th's or 100th's. (Of course, all else being equal - alignment, driver, etc.)
Desired Vehicle Characteristics;
- Neutral Balance w/slight preference toward understeer.
- Minimized sensitivity toward poor inputs.
- Can take wife in vehicle w/o ride being miserable (cruising).
Goal;
- Competitive Locally & Regionally (same state, different clubs)
- Compliance with 12-month planned build budget (disposable income I want to devote to the build).
- Availability of proven parts / component set-ups.
Installed Components;
- Z51 F/R Spring (will sell front)
- Z06 F/R ARB (will sell front bar)
- Metal End-Links
- LT's 1.75 + Catalytic's
- Z06 Titanium Exhaust (Noise Compliance)
- Bilstein Sport Shocks (25K miles)
- CAI (West Coast Hurricane - Requires no modification to existing structure w/Varam Air Bridge - chosen as this set-up minimizes water ingestion).
- LS6 Intake (Installed in 2001 models+)
- Stock Tire/Wheel Combination on Toyo Street Tires.
- Tune + Mustang Dyno
- Purchased Lifetime Alignment & Recheck / Balance - Firestone Auto
- Stock Bushings (90,000 miles on Vehicle).
Selected Components & Order of Installation;
- Bridgestone RE-71R (275/35/18's x 4) - [$1150.00 M/B]
- ZO6 Argent Gray Speedlines 18 x 10.5lbs [~$850.00]
- Hypercoil 12407HPT [$400.00]
- Strano 33mm ARB [$~280.00 + SH]
- Koni Sport Shocks #3013 [$1050.00 incl. SH]
- Borg Motorsports Delrin Bushings [$600 - $1200.00 + SH]
- Adjustable End-Links for Rear Bar [~110.00+ SH]
Total Cost; ~$4440.00 to ~$5040.00 / $370.00 to $420.00 monthly.
Additional;
- Z51 rear bar will remain in vehicle as will the Z06 rear ARB (torsion bar).
- Alternatives could be DRM Valved Bilstiens [~$600.00] (do you really loose seconds, stability, or only 100th's of seconds). Is it worth the extra $450.00 to go with DA shocks when the venue is just local / state events?
- C5 Wagon Wheels x 2 (~$200.00) - If you don't mind the ugliness. My OCD would not permit this.
(Price Reduction = $1100.00)
Questions;
1) The various years of C5 bases came with head casting numbers, 853, 241, & 243 seem to be the most prevalent. The 241 heads have a combustion chamber size of 66.67cc whereas the 243 heads have a combustion chamber size of 64.45cc & improved intake port & exhaust port volumes of 210cc & 75cc respectively. Are these "interchangeable" in STU considering they come factory, on the base platform, but the year is only 2004 models... I'm thinking this is updating / back-dating which is not allowed in STU. Just checking.
2) Fuel - what fuel is everyone running? I'm sticking with 91 (most locally available). E-85 is too corrosive & is hygroscopic in nature, its corrosive, and the potential of phase separation at relatively low moisture content is not appealing.
The 243 heads are the LS6 heads and are therefore not legal on a base C5 in STU. Same with the LS6 intake manifold. The only way to legally run that is to have the entire car converted to the years those intakes were stock. For example, an FRC would have to convert to a coupe. If you are an earlier coupe, you'd have to get the right cam, block, ABS module, potentially fuel system, etc. If you aren't already an 02+ coupe or convertible that needs a bunch of work (flood car, etc), it's really not worth the effort. If you are talking about the LS6 filter assembly, that would be fine.
E85 isn't legal because the C5 was not factory spec'ed as a flex fuel vehicle. Because of that it has to be E10 and under as well as street legal. That pretty much means anything up to 100 octane. No additives allowed. If you want to keep it streetable, just get it tuned to the premium fuel you can get in your area (91-93).
The 243 heads are the LS6 heads and are therefore not legal on a base C5 in STU. Same with the LS6 intake manifold. The only way to legally run that is to have the entire car converted to the years those intakes were stock. For example, an FRC would have to convert to a coupe. If you are an earlier coupe, you'd have to get the right cam, block, ABS module, potentially fuel system, etc. If you aren't already an 02+ coupe or convertible that needs a bunch of work (flood car, etc), it's really not worth the effort. If you are talking about the LS6 filter assembly, that would be fine.
E85 isn't legal because the C5 was not factory spec'ed as a flex fuel vehicle. Because of that it has to be E10 and under as well as street legal. That pretty much means anything up to 100 octane. No additives allowed. If you want to keep it streetable, just get it tuned to the premium fuel you can get in your area (91-93).
Great information.
There appears to be a gray area as to which model year the LS6 intake was a factory install for base C5's. Multiple documented sources, including the Corvette Black Book indicted 2001 was when the LS6 was introduced on all Corvettes, however, other sources indicate 2002. The GM consensus indicates early 2001 models with 6-speed transmissions were equipped with the LS6 intakes, and 2001 auto's had the LS1. All 2002+ regardless of transmission had the LS6.
Which document would a sanctioning body reference to determine which year had the LS6's and which did not?
There appears to be a gray area as to which model year the LS6 intake was a factory install for base C5's. Multiple documented sources, including the Corvette Black Book indicted 2001 was when the LS6 was introduced on all Corvettes, however, other sources indicate 2002. The GM consensus indicates early 2001 models with 6-speed transmissions were equipped with the LS6 intakes, and 2001 auto's had the LS1. All 2002+ regardless of transmission had the LS6.
Which document would a sanctioning body reference to determine which year had the LS6's and which did not?
The LS6 was definitely introduced in 2001. It was a 385 HP version. In 2002, it was bumped to 405 HP. I had always thought that the LS6 intake didn't go on until 2002.
Autocross doesn't really work in the way a sanctioning body would. It's basically self policed. SCCA puts out the rules, then at events competitors can protest other competitors for illegal modifications. It is then up to the person being protested to prove that their part is legal to a protest committee. If you feel you can reasonably do that, then you are good.
I would HIGHLY suggest not worrying about the intake. You rarely get high enough in the power band to get peak numbers. On top of that, power is about the last thing you need in an autocross. Spend your time and money getting seat time and making the car handle in a way you like. When you lose a National Championship by a couple tenths, then worry about things like this.
For some perspective, look at CP from Nationals last year. The second place car had less than half the power/torque of the winner. And those cars are on true slicks and can actually use the power they have.
My 2001 Z28, built in August of 2000 had the LS6 intake on it. So I'm sure a 2001 Corvette would have that. Now the LS6 heads... That I don't know about.
As for the shocks, they matter and it's silly to spend the time and effort to try and build a car that's good and not be able to tweak a very basic thing that has a lot to do with how the car acts and reacts. (not not ALL adjustable shocks are good, some suck, but good ones are worth it).
Rear bar, again, why not give yourself the best flexibility in tweaking the car? Some bars are super pricey, some aren't. See my 3 way rear bar, not even $200... and with it you have 3 setting and two on the front, so lots of things you can do. Add shock damping changes and you already have a lot more flexibility than you have with shocks that are what they are and a bar that can't be changed.
My 2001 Z28, built in August of 2000 had the LS6 intake on it. So I'm sure a 2001 Corvette would have that. Now the LS6 heads... That I don't know about.
As for the shocks, they matter and it's silly to spend the time and effort to try and build a car that's good and not be able to tweak a very basic thing that has a lot to do with how the car acts and reacts. (not not ALL adjustable shocks are good, some suck, but good ones are worth it).
Rear bar, again, why not give yourself the best flexibility in tweaking the car? Some bars are super pricey, some aren't. See my 3 way rear bar, not even $200... and with it you have 3 setting and two on the front, so lots of things you can do. Add shock damping changes and you already have a lot more flexibility than you have with shocks that are what they are and a bar that can't be changed.
For reference, I have experience with the DRM Bilsteins on my STU Corvette, and as Sam is getting at here, they just don't cut it. I had to learn the hard way. Sure, you could re-valve again, but it's probably easier and more cost effective to go with at least a single adjustable.
Going through this myself makes me urge you to skip a step. Only spending $400 on shocks is nice, but may waste your time more than your money.
My 2001 Z28, built in August of 2000 had the LS6 intake on it. So I'm sure a 2001 Corvette would have that. Now the LS6 heads... That I don't know about.
As for the shocks, they matter and it's silly to spend the time and effort to try and build a car that's good and not be able to tweak a very basic thing that has a lot to do with how the car acts and reacts. (not not ALL adjustable shocks are good, some suck, but good ones are worth it).
Rear bar, again, why not give yourself the best flexibility in tweaking the car? Some bars are super pricey, some aren't. See my 3 way rear bar, not even $200... and with it you have 3 setting and two on the front, so lots of things you can do. Add shock damping changes and you already have a lot more flexibility than you have with shocks that are what they are and a bar that can't be changed.
Originally Posted by Ramo7769
For reference, I have experience with the DRM Bilsteins on my STU Corvette, and as Sam is getting at here, they just don't cut it. I had to learn the hard way. Sure, you could re-valve again, but it's probably easier and more cost effective to go with at least a single adjustable.
Going through this myself makes me urge you to skip a step. Only spending $400 on shocks is nice, but may waste your time more than your money.
Unfortunate to hear about the DRM valved Bilsteins. I'll take the advice and go with the DA's. These would allow the best options for flexibility & tuning of the chassis for the budget. As for the rear bar; also good advice.
I have been contemplating installation of adjustable end-links for the rear bar - pro's & con's of these vs., a three position adjustable rear-bar?
Unfortunate to hear about the DRM valved Bilsteins. I'll take the advice and go with the DA's. These would allow the best options for flexibility & tuning of the chassis for the budget. As for the rear bar; also good advice.
I have been contemplating installation of adjustable end-links for the rear bar - pro's & con's of these vs., a three position adjustable rear-bar?
I'm no engineer, but as I understand it, you'll need the adjustable end-links to corner balance the car.
I think it would be silly not to do adjustable end-links.
I'm a little confused, you say your on a budget, but want to do DA shocks now. I'd think SA shocks e.g. Koni's, Ride-tech, etc, would be more inline with a budget build and simplicity. That's the route I took. I'm not saying to not do DA, but it seems more complex and expensive.
I'm wrapping up my budget build.
Suspension:,
Ride-tech shocks
Sam's sway bars front and rear,
Hyperco front track spring
adj. end-links.
Folks *commonly* just assume shocks are DA, and I'm forever trying to tell them what's what. Some cheap shocks are Double acting, single adjustable (meaning bump and rebound both change). Ridetech and Koni are rebound only, and are what I'd recommend for the average bear (and what I prefer to run myself).
I'm no engineer, but as I understand it, you'll need the adjustable end-links to corner balance the car.
I think it would be silly not to do adjustable end-links.
I'm a little confused, you say your on a budget, but want to do DA shocks now. I'd think SA shocks e.g. Koni's, Ride-tech, etc, would be more inline with a budget build and simplicity. That's the route I took. I'm not saying to not do DA, but it seems more complex and expensive.
Adjustable bar and adjustable end links together would be ideal. Adjustable bar allows you to change the roll stiffness. Adjustable endlinks allow you to set zero pre-load so that the car doesn't handle differently turning left compared to turning right. A car with equal cross weights will likely have unequal ride heights at different corners and without adjustable end links, the sway bars will be pre-loaded.
Whenever I use DA I mean double adjustable, I am not sure what a double acting shock would be.
He's referring to the adjusters - some shocks have a single adjuster that changes both rebound and compression damping simultaneously. That's generally the cheap chinese coilover stuff though, dunno if anything that anyone would actually buy for an autox vette is like that.
I'm no engineer, but as I understand it, you'll need the adjustable end-links to corner balance the car.
I think it would be silly not to do adjustable end-links.
I'm a little confused, you say your on a budget, but want to do DA shocks now. I'd think SA shocks e.g. Koni's, Ride-tech, etc, would be more inline with a budget build and simplicity. That's the route I took. I'm not saying to not do DA, but it seems more complex and expensive.
I'm wrapping up my budget build.
Suspension:,
Ride-tech shocks
Sam's sway bars front and rear,
Hyperco front track spring
adj. end-links.
Next for me will be the Borg's bushing kit...
Originally Posted by troyguitar
He's referring to the adjusters - some shocks have a single adjuster that changes both rebound and compression damping simultaneously. That's generally the cheap chinese coilover stuff though, dunno if anything that anyone would actually buy for an autox vette is like that.
whoops, common acronyms can have vastly different interpretations as experienced here. I was using DA's in the general reference form "driver adjustable."
Also, thanks for the lead in on pre-load and end-links. Additional research and understanding is necessary. Like other modifications, this will to be prioritized on the list of needs vs. wants.
A selection of interesting pictures from Nationals below, I added a bit of commentary too:
3rd place, the OS Giken car. Medium rate VBP springs, Penskes, poly bushings with offset rear, Strano bar front and rear, LG Super Pros/intake, and of course the Dual Core OS Giken diff. Pretty low, very good camber up front, rear wheel looks like 0 degrees in this image.
4th place and 23rd place, the Borg Motorsports car. 1500# front VBP spring, MCS shocks, Strano bars front and rear, offset Borg motorsports bushings giving 3+ deg camber front and rear, ARH headers/intake/underdrive pulley, aftermarket gear diff. Rear wheel looks better than any other Vette but still not a ton of neg camber compared to the front wheel. Extremely low ride height.
11th place, this is my car. HPT front spring, Ohlins TTX shocks, non-offset Delrin bushings so only 2.4 camber front 1.5 rear, Strano bar front, headers/intake, stock diff. At least 1" higher ride height than the Giken car and probably 1.5" higher than Lane's, even though I am on the low profile Hyperco adjusters threaded all the way into the spring. Definitely need a flat spring to get my front ride height down. Front camber seems decent but could use more, rear wheel is starting to lean over towards positive so could use 1-1.5 degrees more for sure.
15th and 19th, Ramos' car out of Michigan. Decently stiff VBP springs, DRM Bilsteins, Strano bar front, otherwise very stock! Similar alignment to me, a bit lower in the front and a bit higher rear. Camber in the turn looks basically exactly the same as my car. Andrew's co-driver was in the trophies after Day 1 on the east course which was very impressive, but the West was tricky with how little damping he has. I'm sure he will chime in...
22nd, Nick's car out of Florida. Never seen this car before Nationals and didn't get a chance to talk to him to see what he was running. Looks like more camber front and rear would help. edit: see Sam's post below for info on this car, it is Sam's old car.
Finally, the 1st place 350Z driven by Jeff Stuart. Unsure on spring rates but probably 1100ish front 700ish rear, Penske dampers setup by Ankeny, OS Giken diff. Very flat in the corner compared to even Lane's car, and rear camber is significantly higher than any Vette. Front camber is about even with the top two C5s. Watching his videos it is interesting to see how much less you have to move a steering wheel in a 350Z compared to a C5, and how hooked up that car is on throttle. Less torque than us for sure but it seems like he was floored 50% of the time on the East course, and it changes direction very nicely. Also not sure if he was on 11" wheels or 10.5, anyone know?
Some videos I have found so far:
Jeff Stuart East: Jeff Stuart West:
Great post above, for a couple of reasons. Mostly pictures are worth 1000 words, but I have to add some anyway.
First, unless something changed Lugod's car had my bars front and rear both, so did Lane's and Nick Dunlap's car that I sold to them a few months ago as they wanted one and only found cars that folks thought were gold plated. And I had a lot done already.
That's right, Dunlap's car was mine. I know it *well*. It's also on stock springs, stock bushings. StainlessWorks headers, K&N intake, Ridetech HQ shocks, a few other things. Of the three running my bars at both end, it's the only one on stock bushings (including the associated deflection). Some camber is being lost to the squish that Jonathan's and Lane's car don't have with bushings. Also it sounds dumb but should be noted because of the road I live on, the center under spoiler is worn a lot in the middle, which makes the car look a bit higher than it is (it's not high at all) because you can see so much more light under there.
Here's the thing. Notice the fact none of those cars are rolling massive amounts. Now you see why I'm not one to go bonkers on springs. Considering there are 3 examples of cars there all on the same bars front and rear, the same wheel size, same tires too it's a pretty good comparison.
I'll add that Lane's car appeared to be the worst across the bumps on the showcase turn on the West Course. I watched what looked like the front of it skipping across the bumps, running wide, and then picking up the cone at outside of the gate.
I'll add that Lane's car appeared to be the worst across the bumps on the showcase turn on the West Course. I watched what looked like the front of it skipping across the bumps, running wide, and then picking up the cone at outside of the gate.
Christian
That's because I had the damping all jacked up. I fixed it at the Trials and it was much better.
I'm late to the party here. Work trips with public road testing out west and working on a new house right after nationals was eating up all my time.
Nice post, Matt. Thanks for the sum up. Had a great time at my first nationals with my BS+ car in STU. I'm looking forward to improving the car and myself for 2016. I really enjoy the Corvette brotherhood going on even though we're all competing against each other... and that really goes for the whole solo nationals group in general.
I believe Lane on what he says regarding damping causing his issues rather than being oversprung. Like he's shown in his build thread and measured ride rates with his "extreme" springs, wheel rates are still very reasonable and all under 300 lb/in according to his measurement.
But, I was very impressed with the feel of Lugod/ OS Giken's car being on the low rate springs. If you reference Mr. Borg's measurements, the OS Giken car would be considerably higher spring rate up front with even less rear spring rate in the rear than stock, albeit only slightly. It felt great with the Penskes he had tuned very well. Still loose on entry with a lot of dive though, I found. I know I'll personally stick with my 1200/800 combo I have currently. If anything, I'll go up from there, but don't see the need at this time with so many other factors requiring more improvement.
The OS Giken diff felt great in the car too. I'm not affiliated with them and I can honestly say it was night and day from the stock diff in my car. The biggest difference I could distinguish from the passenger seat was all the steady state push that vanished from the car, despite having similar balance in terms of springs and sway bars to mine. OS Giken has, with a clutch type diff, achieved a lot of the same performance attributes mechanically that you get from an eLSD in a newer high performance GM product. It's a very impressive piece.
07-28-2015, 07:27 PM
