Vortech Centrifugal Supercharger Wastegate Install - A Gateway to Street Supremacy

The "Oh s**t" switch. If the... 

   

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The "Oh s**t" switch. If the Cobra competition starts to get tough, Grundman just needs to add high-octane race fuel and flip this switch. It changes the engine tune in the DFI (jumps timing to 18 degrees) and closes the wastegate (enables 19 psi).

The wastegate was set up to drop the boost to 14-15 psi when Grundman runs pump gas. Essentially this Saleen will be making greater average boost rather than just a peak number. Because the YSi-Trim unit spins hard, impeller speed at low rpm is greatly increased. The final result is a super-aggressive boost curve up to 15 psi, then a flat line across to the peak rpm.

Hell Bent Race Cars was responsible for mounting a custom air-to-air intercooler in the front bumper and adding the wastegate kit, which Turbo People sells. The chassis shop also upped the safety margin by installing a custom-bent, six-point rollbar and racing harness. Once the hardware was mounted, Super Street Performance (Farmingdale, New York) wired up the boost controller and interfaced it with the Accel DFI Gen 7 computer system. Spetter tended to the tuning and engineering of the combination. Super Street Performance also added a switch in the ashtray to activate the system. A quick flip of the switch enables the wastegate and dials up the pump-gas tune-up in the computer system. In the heat of battle, the switch is thrown (on the fly, if necessary), the wastegate is slammed shut, and the DFI switches over to the race tune-up. The wastegate control solenoid is wired into the Gen 7 thanks to utility ports that are normally used to control nitrous solenoids. The wastegate kit requires the use of an aftermarket fuel-injection system or blow-through MAF sensor setup.

To put Spetter's theory into practice, chassis dyno testing was completed at Crazy Horse Racing (South Amboy, New Jersey). Its Dynojet chassis dyno is capable of data logging boost so we could follow the curve under all conditions. A quick analysis of the graph shows how effective the wastegate was. On pump gas, the wastegate restricted boost to the desired 14.9 psi. It ramped up quickly, and by 5,000 rpm the manifold saw nearly 15 psi of boost, and the wastegate opened to relieve pressure down to the 14-psi range. In this trim, Spetter coaxed 655 rwhp and 655 rwtq from the stout pushrod contender. It was a tune that was regarded as safe, with only 15 degrees of timing and 11.3:1 air/fuel ratio as read by an Accel DFI O2 sensor.

Thanks To the wastegate and... 

   

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Thanks To the wastegate and boost controller, we could run a small pulley on the YSi-Trim. It will make 19 psi with the wastegate shut and Spetter regulated it to 15 psi, perfect for the street. Spetter did say he could have set up a knob on the controller, giving Grundman a few more boost choices. He said a knob would allow 10 psi, 12 psi, and 15 psi settings.

One observation about the car was that the air inlet temperatures would actually go down as the engine increased in rpm, showing the extremely efficient heat-reducing capabilities of the intercooler. We were also quite amazed at how timid and mild the '90 Saleen sounded, despite throwing out 655 raw horsepower. The boost curve was nothing like any centrifugal blower we have seen, as right at 5,000 rpm the wastegate opened and dumped boost. The curve flat-lined until the peak rpm of 6,400.

"The curve looks like a turbo car," Spetter says. "It may not be as aggressive as a Kenne Bell or Whipple Cobra, but if you compare this graph to another one of my customer's Cobras, you can see that Grundman's car crosses past the Cobra at 4,000 rpm. From a roll, this Saleen would be all over a Cobra." The Whipple Cobra made 614 rwhp at 17.99 psi of boost (on race fuel), while the Saleen knocked down a best of 655 rwhp with a wastegate regulated 15.02 psi. Spetter couldn't find a similarly prepped turbo car that had been saved in the Dynojet program, but he said a turbo street car would have a boost curve that looks similar to Grundman's Saleen.

The battle for blower supremacy is getting tougher, and the centrifugal blower camp now has another weapon to use in fighting the enemy.

An Accel DFI wide-band O2...        read full caption An Accel DFI wide-band O2 sensor was used to monitor the air to fuel ratio.	Spetter kept it at a rather...        read full caption Spetter kept it at a rather safe 11.3:1 ratio on all the runs.	Spetter Handled all of the...        read full caption Spetter Handled all of the DFI Gen 7 tuning chores and wrote a few programs for the Saleen. He kept the pump gas and race gas tune-ups conservative. That means 11.3:1 air/fuel ratio and 15 degrees of ignition timing for pump-gas use and 18 degrees for use on race fuel.
The Wastegate was fastened...        read full caption The Wastegate was fastened to the blower tube near the intercooler. Just above the dump pipe (arrow) is the vacuum block and boost controller solenoid. The Tial wastegate is properly sized for this application, and Spetter reported that he could configure the boost controller to have up to four settings; we utilized only two for this test.	Dyno Testing was performed...        read full caption Dyno Testing was performed at Crazy Horse Racing.	This Graph represents Grundman's...        read full caption This Graph represents Grundman's Saleen versus a recently dyno'd Whipple-blown '03 Cobra. The boost curve (lower graph) is intense as the twin-screw blower is all over the centrifugal blower in the low-rpm range. But once 4,100 rpm hits, the centrifugal power curve overcomes it, despite the Saleen making nearly 7 psi less than the Cobra. According to Spetter, this Saleen would outrun most Cobras if they ran from a roll.
Our Test subject had a peaky...        read full caption Our Test subject had a peaky torque curve that topped out at 655 lb-ft at around 4,800 rpm. Max horsepower came at around 6,400 rpm and was 655 at the rear wheels. Spetter says the boost curve was more indicative of a turbocharged car.	No-Holds-Barred performance...        read full caption No-Holds-Barred performance requires rear-wheel power numbers like these-829 hp and 722 lb-ft. This type of performance is just a high-octane fill-up and flipped switch away.	A Vortech bypass valve is...        read full caption A Vortech bypass valve is also employed to dump boost once the throttle body is closed. This prevents boost from backing up into the supercharger head unit.