Nitrous: the race tuner’s biggest challenge

Nitrous: the race tuner’s biggest challenge

By Fergus Ogilvy, February 4, 2015

GibtecLogoLrStarting a competition piston company in the second decade of this century could be a bleak proposition.

Finding new customers isn’t easy. Engine builders have a stubborn tendency to remain faithful to their existing suppliers, unless something goes awry. You could play the game grimly and die of ulcers or you could play it with a light heart and dedication and perhaps survive without losing sleep.

GibtecShopGibtec Pistons, the Denver-based operation did exactly this. But they had one other valuable resource to rely upon: decades of experience at the competitive edge, including several ten-year development programs with NHRA Pro Stock teams

But when asked where they see the biggest challenges in race engine tuning, company founder, Robbie Giebas, responds with one word: Nitrous!  Why so? “Well, the top tuners will tell you nitrous engines have never been completely mastered—there’s still an element of mystery about them. Nitrous oxide induction requires a totally different approach, and it’s a volatile science; if the tune-up is off a little, parts need replacing.

“Unlike the turbo or blower guys, who might get fifty or sixty runs from their pistons, when those nitrous guys are really pushing hard they’re replacing rings every three or four runs—it resembles the Top Fuel class in many ways. If they ease off a little on the tune-up they’ll become uncompetitive. And when the racing gets close, they’ll routinely dismantle the engine after every pass. Leak-down tests, ring end-gap checks, raised ring lands, pinched rings these are constant topics in their world.”

What provokes a raised ring land or a pinched ring?

“Race fuel burns relatively slowly, and if the motor detonates it doesn’t burn the charge properly. As the piston travels down the cylinder, fuel under the ringland and around the ring ignites, causing the ringland to jolt upwards as it fires and the gas expands. Or it might pinch the ring if the mixture is too lean. When you’re forcing a nitrous engine onto the ragged edge of ultimate performance, an elevation change of just 200ft can induce a fatal difference.”

Why do the nitrous builders want billet?

“It’s not just them—most professional engineers who are involved in piston design are constantly making changes. If they didn’t have access to billets they’d probably need several entirely new forgings, which are expensive and take weeks to get.”

What’s the advantage of pistons with buttons?

“They are popular for two reasons. When the piston pin bore breaks into the oil control ring groove, the button prevents the expander in the oil control ring from distorting around the half moon opening, a deficiency more prevalent in power-adder engines. But their biggest advantage is convenience: changing pistons with buttons slashes the servicing time. It also eliminates the frustration of fiddling about with the round wire locks or the double spirals.”

If there’s one thing that sets a premium piston apart from a mediocre one, what is it?

“Ultra flat ring grooves—they’re the key to power.”

Source

Gibtec Pistons
Denver, Colorado
(303) 243-3340
RGiebas@GibtecPistons.com
 

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