When Mark Tunzelmann needed to shift his dirt bike around, he bought a ute. He just never intended it to cover the quarter in 10-seconds.
The ute started out just as a way of carting my dirt bike around,” claims Mark Tunzelmann. I’m pretty sure he’s having a laugh. Turns out he’s not.
“It stayed pretty standard for the first couple of years of ownership,” he says, almost apologetically.
Figures. There’s no way someone could use a boost-snorting, 10-second-capable 2004 Holden Commodore VZ ute as just a bike carrier.
It’s a cliché, but modifying a car generally leads to a lack of coin and an end result you never thought you’d own the key to.
Mark also started with modest intentions. The original changes were low-key by modifying standards, comprising just an air intake, exhaust and a tune. While the gains weren’t ground-breaking, they were enough to have the LS1 mule delivering an easy 266kW at the wheels.
Next up: changing the “terrible” factory brakes. While some people fit a set of uprated discs and pads, Mark ditched the whole setup, fitting D2 eight-pot callipers, 330mm rotors and braided lines on the nose, and D2 six-pot callipers, 330mm rotors and braided lines on the tail.
You’ll have heard this next bit before: “Soon enough, I was after more grunt.” It was a simple solution, but he fitted a bigger cam that lifted power figures to 284kW at the wheels.
It wasn’t enough. The numbers read okay, but the ute lacked a familiar feeling he’d grown fond of in previous cars: boost. He linked up with renowned New Zealand turbo expert Steve Murch, and it all went downhill from there. “After talking to Steve from Motorsport Engineering, he said he had the perfect turbo for the job.” Perfection is subjective, and defining it can depend on a number of factors: how much power you want, what the car will be used for, how driveable do you want it to be, etcetera. The list could go on.
Steve Murch’s definition of perfection meant extracting some serious numbers from the setup. “Steve had an IHI RX8 turbo off a ’90s-era Indycar, with a magnesium compressor housing and a titanium turbine housing. It supports up to 900kW and weighs only just over five kilograms.” Told you perfect is a subjective term. Murch’s idea sat well with Mark though, and work begun.
While the LS1 is capable of withstanding boost-fed applications in standard form, it stood little chance of handling power of these proportions. So it was lifted from its hole and pulled down to ensure adequate components were fitted inside. These included a set of 9.9:1 forged pistons, Perfect Circle rings and ARP rod bolts. Because Mark is a spanner-spinner by trade, he completed all the work on his own.
With the parts bolted in place, the entire rotating assembly was then balanced.
Up top, a Kelford Camshafts naturally aspirated-spec camshaft was fitted, as were PAC valve springs and a set of ARP head studs. With the engine built strong, things were moving in the right direction. In order to filter enough air through the top half, the throttle body was ported and a 230mm K&N air filter fitted.
With an engine set to suck boost, it was a mere matter of providing it with the necessary ancillaries: a Turbosmart external wastegate, 600x300x76mm front-mounted intercooler, three-inch alloy intercooler piping and a Turbosmart blow-off valve.
Clearly, the factory fuel system would no longer be up to the task, so it was substituted for something more suitable.
In fact, the only component remaining from the original setup is the factory in-tank feed pump. It now feeds a six-litre surge tank, which sends the fuel via two Bosch 044 fuel pumps to the Turbosmart 900kW fuel regulator, custom fuel rails and a set of 550cc injectors before it enters the combustion process.
With the supporting work ticked off, it was time to fire the force-fed LS1 to life to see whether the modifications made the numbers. “After the turbo was fitted and all the piping was finished, a quick road tune was carried out,” Mark says. To get some figures on how that tune stacked up, Mark strapped the car to the rollers at Pro Tune’s dyno in Manukau. The results were underwhelming. “The ute made 334kW at the wheels at 0.4 bar, which was a little disappointing. We tried winding the boost up, but it didn’t seem to want to make any more.” Cue the first teething problem. “After a bit of investigating and testing, I found the three-inch exhaust and mufflers to be the restriction.”
With the problem identified, a new 3.5-inch exhaust and muffler were made which, Mark tells us, “brought the turbo to life big time — so much so that I needed to fit a second wastegate to control boost.”
The second external wastegate means the Commodore now packs both 50mm and 38mm Turbosmart examples.
Wanting to know what the LS1 could really produce, changes to the fuel system were made to bring it to how it currently stands, and the car was sent back to the dyno at Pro Tune to have the factory engine management system reflashed with the EFI Live custom turbo operating system. The first run spun 388kW at the wheels at the same boost. Mark lifted the boost to 12psi. It made 451kW at the wheels, which Mark describes as “pretty respectable”.
The tarmac of Fram Autolite Dragway, Meremere, is a good proving ground. Mark’s goal: a 10-second slip. Street tyres would never get him there, though. Nor would the factory driveline and suspension setup.
While the factory-fitted six-speed Tremec in the car remains standard — albeit with a modified shifter — the clutch connected to it does not. To transfer the power to the ground, a custom chromoly flywheel, carbon/Kevlar clutch plate and 5600lb pressure plate combination has been fitted, along with a 3.46 ratio shimmed LSD. The suspension assembly remains factory, with Monroe GT shocks and ultra low King springs fitted.
To tighten the setup a little, Nolathane adjustable camber and castor bushes were fitted, as were Nolathane rear differential mount and subframe spacers.
The final piece in the strip setup came in Mark’s choice of treads. While the car sports a set of DTM Hiro wheels — measuring 19×8.5-inches on the front and 19×9.5-inches on the rear — it’s the dedicated strip rubber that does the job. Chosen because of their popularity in street-legal setups, a set of 26×11.5×16-inch Mickey Thompson ET Street Radials grips the starting line.
Itching to see how the modifications spoke on the quarter, Mark took the car to Meremere. “The first trip to the drag strip resulted in an 11.4 at 126mph (203kph), but with the drag tyres on we found the turbo was dropping off boost between gears,” Mark says. “I figured a small shot of nitrous would fix the problem.” It did, although he was left largely without traction in the first four gears, which made tuning the nitrous a problem. Even though the nitrous system comprised only a 50hp (37kW) wet shot and a nitrous intercooler sprayer, it was enough to lower ETs significantly.
“The next meeting the ute ran an 11.04 at 133mph, which was oh-so-close to that 10-second slip. So a bit more fine-tuning was carried out, and then at the following meeting I ran a 10.89 at 135mph, followed by a 10.92 at 135mph.”
Built at home, capable of 10-second passes and still able to carry a dirt bike if needed… That’s our kind of car!
2004 Holden Commodore SS Ute – Specifications
Engine: 5.7-litre (346ci) LS1 ohc 32-valve V8, 9.9:1 forged pistons, Perfect Circle rings, ARP rod bolts, balanced rotating assembly, Kelford naturally aspirated camshaft, PAC valve springs, ARP head bolts, modified throttle body, 229mm K&N filter, IHI RX8 turbocharger, two Turbosmart external wastegates – 50mm/38mm; 600x300x76mm intercooler, three-inch alloy intercooler piping, Turbosmart blow-off valve, 37kW (50hp) wet nitrous system, nitrous intercooler sprayer, two Bosch Motorsport 044 fuel pumps, factory lift pump, Turbosmart 900kW fuel regulator, six-litre surge tank, custom fuel rails, 550cc injectors, MSD spark plug leads, custom stainless turbo manifold, custom 3.5-inch exhaust, custom stainless steel muffler, factory radiator, custom radiator overflow, EFI Live reflashed factory ECU, billet power steering reservoir, power steering cooler, custom oil catch can, custom coil covers
Driveline: Tremec T56 six-speed gearbox, modified shifter, custom chromoly flywheel, 394kg/cm2 (5600lb) pressure plate, carbon/ Kevlar clutch plate, 3.46 ratio shimmed LSD
Suspension: Monroe GT struts, ultra-low King Springs, Nolathane adjustable camber bushes, castor bushes, rear diff mount bushes, subframe spacers
Brakes: D2 eight-pot callipers, 330mm rotors, braided lines – front, D2 six-pot callipers, 330mm rotors, braided lines – rear
Wheels/ tyres: 19×8.5-inch DTM Hiro wheels, 245/35R19 Dunlop tyres – front, 19×9.5-inch DTM Hiro wheels, 265/35R19 Federal tyres – rear, 26×11.5×16-inch Mickey Thompson ET Street radials – drags
Exterior: Factory exterior, tinted headlight covers, rolled rear guards
Interior: Factory interior, tinted windows, twin gauge pod, Auto Meter boost gauge, Aeroforce scan gauge, Orion two-channel amplifier, Soundstream 6.5-inch components
Performance: 451kW at the wheels at 12psi, 0-400m in 10.89 at 135mph
Mark Tunzelmann – Owner Profile
Previously owned cars: 300kW RS Subaru Legacy, JZA80 Toyota Supra, RB30DET R33 Nissan Skyline, V8 Toyota Soarer
Dream car: Koenigsegg CCX-R
Build time: 18 months
Length of ownership: Three years
Mark thanks: My good mates Lance, Zac, Bling, Stiff, Jeremy and John for all their help with the car, Wayne at Protune – 09 912 9912 – for the dyno tuning, Steve at Motorsport Engineering, Nick at Frank Allen Tyres Waiuku – 09 235 9034, and my girlfriend Ashlee for putting up with all the late nights
Words: Gray Lynskey Photos: Adam Croy
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