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Unread 12-29-2014, 05:33 PM
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Join Date: Jul 2004
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Default Re: Vorshlag Budget TT Build: Project DANGER ZONE

continued from above

Where Did This Car Come From?

So about 3 years ago an old friend, Brian Matteucci, wanted to build a NASA Time Trial car. He was a long time autocrosser and former SCCA W2W Club Racer and watched what we were doing in NASA. He liked the cost-to-seat-time ratio of the TT series of classes, which was why we were in it as well. I helped him understand the NASA TT rules as well as the confusing TT classing formula and points classing system. We bench raced several builds over a few weeks and came up with the C4. That was no accident - because we had both raced these in the past. My history with Matteucci goes way back to about 1989, when he was a racer in the Texas A&M Sport Car club racing in a notchback 5.0L Mustang... I was about a year ahead of him and happened to be racing the same exact type of car.

We were competitors and friends through college, both helped create a new and popular autocross class called Super Street Mod in 1990 (we used this class to help push the SCCA to create Street Mod), and were roommates after college when we both worked at our first jobs in Houston as engineers. He and I both used to love digging through rule books looking for ringer cars and rules to exploit. After college we both autocrossed C4 Corvettes for a time - he was in a 1987 Z51 while I raced a 1994 Z07, both in SCCA's Super Stock class. When his 87 Corvette's fuel pump died on day 2 at Solo Nationals one year he co-drove my C4 - and hated it.

My 1994 Corvette Z07 running in Super Stock at Solo Nationals in 1998. It was on Hoosier DOTs but was otherwise bone stock

The differences between our cars was dramatic back then - at low speed autocrosses - but it was obvious to both of us that the LT1 was far superior to the TPI engines at higher speeds. Already owning a C5 Z06, when he suggested a letter class TT build 3 years ago I immediately suggested another Corvette, but one that was a 100% dedicated, no-compromise race car build. Jason and I here at Vorshlag had often talked about the TTC classing of the late C4, and after some discussion with Matteucci, he agreed that it had a lot of potential in this class. He went out and bought this mess for $3000, sold off the interior bits for $1000, and had a $2000 platform to build a TT lettered class car from.

During the next 2-1/2 years Matteucci proceeded to strip hundreds of pounds out of this car and replaced lots of broken OEM bits (24 years can take its toll on anything), while testing it at various autocross events along the way. He did this while he was very busy with work, building a new house and shop, building a chump car, and autocrossing his C5 Z06. In December 2014 he got to a good stopping point and I bought the car for a great price - along with a promise to let him co-drive the car with me in NASA TT. Amy and I did that last year and it was a good way to get us both out on track for less money spent - which fits this project well.

With our "Team Vorshlag" entry we can both drive the car for one entry fee, doubling the chances for a fast time (two sets of eyes and brains are better than one). Matteucci worked at Roush Engineering for several years, and while there was responsible for building and developing a fleet of Bonduraunt school cars when Ford was their supplier in the 2000s. He lived at the track for many months, driving these cars for hours every day, so he's no stranger to finding a good track set-up: he was paid by one of the biggest engineering/racing companies in the world to do just this.

Left: The factory power steering cooler is a huge double-pass unit. Right: I pressure washed underneath to help find an oil leak

Last but not least, Matteucci was also the designer of our first three initial camber plate designs when he started Motor-Force Engineering back in 2002. We bought his company (and IP) back in early 2006 and several of the current Vorshlag camber plates can trace their roots back to his initial designs. Other than some manufacturing aspects and tweaks to materials and coatings, they are for the most part unchanged. So he has a long history with me and Vorshlag, whether he wants to admit it or not, heh. When I picked up the car on December 20th I gave him a bunch of Vorshlag swag, which was part of the deal with the car - he has to wear this stuff at the track, especially if he is the one who gets the wins!

TT Classing Looks Solid

So if you look at the NASA TT (and PT) classification for Corvettes something jumps out at you (go to page 20 of the TT rules) - most Corvettes either require a dyno test for an initial base classing (C1-C3) or are just shoved straight into TT1/2/3 numbered classes (C5-C7). The lone exception is the C4 generation, which has 5 separate letter class listings:

MODEL........................................BASE CLASS...... MIN WT
Corvette C4 ('85-'91)............................ TTD**......3223
Corvette C4 ('92-'96) (LT1)................ TTC*.......3203
Corvette C4 (LT4 option) (330 hp)...... TTC**......3350
Corvette GS ('96).................................. TTC**......3350
Corvette ZR-1 ('90-'95).......................... TTB*........3500

While the TTD entry for the 1984-1991 "TPI" Corvettes might look the most attractive place to start at first glance, the minimum weight is higher yet they make a lot less power (230-250 hp) than the LT1s. With two stars it is already -14 points out of 19 in TTD class, and strapped with TTD's 245mm base tire size, so it would be nearly impossible to stay in TTD class, meaning it would need a lot of work to be competitive in TTC. Of course upclassing adds 20 points to play with, so it might make the 12:1 power to weight ratio of TTC, with some dollars and points burned on engine upgrades. The two LT4 powered cars (all 1996 6-speed cars and the '96 GrandSport) have an extra star (-14 points in class) and extra 150 pounds of minimum weight, but the only advantage being +30 hp over the LT1 it is not ideal (plus they are worth more money used). Likewise the ZR1 has +300 pounds more minimum weight (and boy were they heavy!) and its up a class (TTB) and has one star (-7), plus these are somewhat rare and pricey, and expensive to maintain and upgrade. Yuck.

So the lighter, rugged and simple 1992-1996 LT1 cars are really the best bet, in my mind. TTC seems like an odd place to class the 1992-96 LT1 Corvette - and it might well be, but it is pretty old and I doubt many (any?) have been competitively run in NASA TT or PT. We shall soon find out if this base class makes sense, because that's where we are going to run it.

TTC 1992 Corvette Build Basics

While several folks guessed we would be building a "C4 in TTB", nobody guessed the TTC angle. And why would you? With the base classing of TTC* we only have 14 points to play with in class, so how could it be as "fast" as I predicted? For one, it doesn't need any points spent on power mods to meet the max power-to-weight ratio, as it will easily make the 12:1 limit for the class. So we save points there. How do I know? I owned a nearly identical 1994 Corvette that I had dyno'd on a modern DynoJet, where it made 277 whp in bone stock form, back in 1996 (these cars were a hair under-rated at "300 hp" crank). Another TAMSCC racer (Mike Mclure) owned a 1996 LT4 Corvette and dyno'd it at 308 whp the same day on the same dyno (also under-rated by the factory). If you know your dyno numbers, you will see that the LT4 makes almost exactly what a stock LS1 makes in a C5 (~310 whp), and the LT1 just a little bit down on that.

Left: The 12" front brakes are adequate but can be upgraded to 13" rotors "for free" (no points). Right: The ABS system is ahead of its time

The factory brakes are also ahead of other cars from this era and not much if any off of the C5. GM developed its best ABS systems on the Y-body and this 1992 model has one of the best of the generation. And while the 12" diameter front brakes seem a little wimpy on the Base Trim Model, which this car has, they aren't total junk. The calipers are twin piston floating PBR units, a cast aluminum design used on the Y-body, F-body, and even the SN95 Mustang Cobra, to name a few. We have found a way in digging through the rules and Base Trim Level of the 1992-96 Corvettes to upgrade the discs to thicker, 13" diameter discs for zero points (more on that soon), so that saves us points and only costs a few dollars.

We will show better suspension pics in the next update, but these will do for now

Suspension is very advanced for the time period, and better than what many of us race with on brand new cars from today. Forged aluminum uprights at both ends pivot on double A-arms up front and a multi-link rear IRS. Both ends are sprung by a composite transverse leaf with factory monotube Bilstein dampers. Other than some freshening and an alignment we're going to leave that pretty much alone.

Last up is the tires. The late C4 was designed to house massive wheels and tires (factory used 17x9.5" on almost all packages and up to 17x11" out back). While we won't be making flares to house big wheels, which is kind of one of our "go to" first mods, we will blow almost ALL of the available class points on tires (more on that next time).

Why not bump up to TTB? Sure, we think this car could be just as competitive there at this class' more aggressive 10.5:1 pounds-per-hp ratio, but it would allow for a lot more mods, and that costs $$. The goal of this is to keep costs down, but with +20 more points to play with after upclassing we could easily spend an extra $10,000 chasing down the points and the top cars in TTB (S2000 + E46 M3). While this would be fun, that's not our goal for the 2015 season. We want to instead focus on the "free mods" that TT allows as well as spend our precious 13 points as wisely as we can, as well as show some of our best "race prep" and safety upgrades - that are the same for virtually all classes.

In the next post we will sow our first few mods - brakes and shocks - that are both zero point upgrades. We will also show our first point mod and show the behind the scenes upgrades and race prep.

What's Next?

I always close my build thread posts with a teaser for the next entry. Well we haven't done much to the car yet, so there's still a lot of track prep to knock out. We did order OEM replacement brake parts and shocks, all zero point upgrades which I will explain in my next post. The next biggest things the C4 needs before the first event are all safety related.

In early 2014 our crew here built the cage and did all of the fire/safety/lighting upgrades for a 1987 Corvette convertible that was initially run in Lemons and Chump but lately has been competing in WRL series endurance events (also known as - the Poorvette). We learned a lot working on that car that will apply to this TTC build, of course. One of the items we will replicate on our car is the roll cage, but due to time constraints (3 weeks to go!) before the first race we will only make the main hoop, harness bar and rear downbars (4 point roll bar) for now.

We will go back and complete the full roll cage structure this car after the first event, to make everything safer (and to add some more ballast weight). Unlike this black 87, our 92 C4 has a roof - but its just a bolt-on targa panel, like all hardtop C4s. That removable roof panel makes it easier to build the cage and provides some aerodynamic advantages over the drop top, but the rear (glass) hatch main roof support structure will still be in the way and make this one a bit more challenging to build.

Left: This is the seat we'll be using in the TTC car. Right: An adjustable seat back brace is visible in this pic

Another area that needs some attention fast is the seat mounting. The OEM seat that came with the car BROKE at an autocross event, which Matteucci warned me about ahead of time. We bought this Kirky 56700LW aluminum seat (see above left) for the Poorvette, but the driver wanted something different so we were stuck with it. This TTC4 project will get a lot of those cast away parts, some of which are brand new. Since the seat is a touch on the big side (17" width) we will make a poured foam seat insert, as well as a seat back brace tied to the cage (see above right)

Due to the weird floor structure of the C4 chassis (some parts are composite and some are sheet metal), and some damage from a previous owner (aka: the Crack Head that tore up the interior and drove through the barbed wire fence), we need to repair and reinforce the floor areas. These cars are tricky to safely mount a racing seat into, as well as ballast plates, both of which we will need to do. The car is already 200 pounds under minimum weight (including a 200 pound driver) and that will only worsen as we (legally) replace OEM body panels and rear glass with lighter weight alternatives. We will run this car at the 3203 pound stated minimum weight and NOT burn points on running a lower weight. Running lighter might seem advantageous but we would have to lower the power output as well (the 12:1 ratio doesn't change for TTC class even if you burn points to "run lighter than minimum").

Two zero-point mods Matteucci already added include the Moroso 20185 road race LT1 oil pan (allowed under TT rules, page 36), which at $288 includes more capacity, a Kicked-Out Sump and Trap Door Baffling for improved oil control, built-in Windage Screen and a port for an oil level sensor. The QuarterMaster 7.25" triple disc clutch ($599) and flywheel are also zero point mods (see page 36) and knocked nearly 50 pounds out of the drivetrain mass. It makes this little LT1 rev quite nicely and shift very well at speed - but driving it around at low speeds is a BITCH and it unlocks a LOT of transmission noise. Don't have accurate pics of these mods yet, but when we take them apart I will get better images and weights. I will include these "zero point" aftermarket part upgrades costs into our build budget, below.


That's all for this time. I will post another update before the first race, January 17th at MSR-Houston, where we will debut the car in NASA's TTC class with me and Matteucci at the wheel. That's assuming everything goes smoothly! The next update will show some actual work being done besides my initial clean-up, and I will also lay out more of our game plan for the season, including which tires we plan to run with. They are 30mm smaller the stock size, but it will make sense why soon.


Last edited by Fair!; 11-06-2018 at 10:07 AM.
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