Wednesday, February 15, 2012
Octane cheating either intentional or otherwise seems worse this season than ever before! Why do we suspect that? We can hear pump gas detonation on the dyno more this year than in years past! It appears that more than ever before, people come here to tune their trail sleds with their own “fresh high test” and discover here that it’s really “low test”. Often, when we experience unusual detonation we can buy 93 octane from another gas station, and the knock goes away. I often talk about the NYS Bureau of Weights and Measures who reports that roughly 10% of gasoline they test in this state is substandard. Dateline NBC took it upon themselves to test octane at California Exxon stations, and out of 85 samples of high test gas one in eight was substandard—the worst of which tested at 75 octane! Car and Driver wrote that the state of Michigan’s Bureau of Weights and Measures found that out of 2,816 samples of high octane pump gas, 217 were low octane. Is your state or province any different?
How can we hear detonation occurring on the dyno? Sean Ray learned about listening to engine knock several years ago at Delphi where he is employed as a calibration engineer. Hyundai engineers came from Korea to Sean’s Delphi dyno cel with a roll of ¼” ID copper tubing that they attached to the engine Sean was calibrating for them. They drilled a hole in the control room wall, bolted the copper tube to the Hyundai engine and inserted the other end into the control room, just dangling in the air. Delphi engineers could now hear every click of detonation—which makes a loud snapping noise that emanates from the copper tube in the control room—sometimes even before the engines knock sensors could notice it! Sean brought the copper-tube deto sensor concept from his Delphi engine dyno cel to DTR several years ago. It’s an incredible tuning aid, and has saved many hundreds of pistons to date! We now listen for detonation here and usually can abort any test before engine damage occurs. Three or four audible clicks and we quit the test. On two-strokes we will never hear more than about twelve clicks of detonation—the engine will have seized by then! Last season Sean and Tim Bender ran over 700 max power dyno tests on one mule 600 race engine for Hentges Racing, and lost zero pistons because Sean could hear clicks and abort. During similar max power testing in years prior to the copper tube, Tim used to bring a box of pistons and a jug of muriatic acid to clean the bores after seizing. Back then it was more wrenching and less testing. But today it’s much more efficient thanks to Sean’s Korean engineer pals!
Four-strokes can be more forgiving—each detonating compression stroke is followed by a piston-cooling intake stroke. This means that a few more intermittent clicks of deto can be heard and tolerated by the engine before really bad things happen. Four-stroke piston seizures from deto are rare. Instead, when continual deto makes spark plug ground straps red hot, preignition can occur which can create the worst damage! Then, peak pressure will climb to the moon, which can crack ring lands, stretch the head bolts/ studs and either blow the headgasket(s) or just lift the heads enough to allow combustion pressure into the coolant passages, spewing coolant out the reservoir overflow. Too often people try to rectify detonation problems not by increasing octane or more conservative tuning, but instead by using stronger head bolts/ studs, O-ringing combustion chambers, copper headgaskets, etc. Then, instead of blowing headgaskets we might see studs being pulled out of the crankcase threads, conrods bend or break and cylinder and head gasket sealing surfaces fried into junk as though attacked by a plasma torch! Tune those high boost engines! Don’t scrimp on octane!
With proper tuning for the available octane, stock fasteners and headgaskets will survive incredible power increases! Justin Fuller of Full Power Performance prefers stock head fasteners in his 200-400+ HP turbocharged Yamaha four strokes—noting that stock fasteners are designed to stretch and continue clamping properly as the aluminum heads grow with normal heat expansion. Heavier larger diameter high tensile strength fasteners may not stretch enough as the aluminum heads expand and can instead create severe cylinder head distortion that can cause compression/ coolant leaks even where no severe detonation occurs.
So, back to the issue at hand—what do we do about this awful situation regarding cheating on octane? To be safe and conservative, ALL HOTROD TRAIL SLEDS SHOULD BE TUNED TO BE DETONATION-FREE ON 87 OCTANE! A conservative tune for 87 octane might result in only 3-4% reduction in peak HP so it’s not a great penalty to pay. Then, leaner jetting or a second more powerful Boondocker or PCV map can be used for lake racing etc when a few gallons of race gas/ av gas can be added to the tank for safety.
It’s quite possible that when we tested Gary Berwind’s Z1 turbo with the Turbo Dynamics’ 4 stage tune, he may have had less than 93 octane in his tank even though he paid for 93 octane that day. Severe detonation made it impossible to run the high power settings without water/ methanol and lots of it! But now, after this dyno tuning session Gary can probably run his sled anywhere with any octane gas. He just needs to have his water/ methanol reservoir topped off, typically with windshield washer fluid. My opinion is that anyone with an overboosted Z1/ F1100T should run race gas, and/ or invest in a water/ methanol injection system. So WHEN (not IF) you buy 85-87 octane even though the pump sign indicates 91-93 octane you won’t need to depend upon factory knock protection to save your engine. And remember, the factory Z1/ F1100T ECU will not look for deto above 8300 RPM!
My own experience with boost and water/ methanol is with the used Whipple supercharger I bought from my pal Rusty in Rapid City SD for my 2002 Chevy Avalanche 5.3 liter V8. Based upon Sean Ray’s calibration work at Delphi we understand that the 5.3 is tuned to the edge of deto NA. So adding boost, especially with no intercooler, is almost guaranteed to create knock. With 6-7 psi boost, my Whipplecharged 5.3 would just pull lots of timing in reaction to light deto even with Sean’s reprogrammed EFI Live tune that gave us 11.0/1 A/F ratio on boost. The knock-induced retarded timing severely limited the power increase. But by adding a water/ methanol injection system the compressed charge temp is drastically cooled to about ambient temperature, and I can run knock-free now with 6psi boost on 87 octane gas. The water/ methanol condenses the compressed intake air thus dropping observed boost pressure a bit with the fixed speed supercharger.
ANOTHER EXCELLENT AFTERMARKET ARCTIC CAT 1000 Y-PIPE
Ted from Terra Alps Racing in British Columbia, Canada (www.terraaplpsracing.com) sent us a stamped Y pipe he makes and sells for Cat 1000 twins. Local Cat wrench Don Zuzze brought this 2007 F1000 bone stocker for a PCV tune, and we tested the Terra Alps Y-pipe compared to the stock Y-pipe as shown here. Adding 5% fuel at 100 and 80% throttle positions with a PCV, the A/F ratio was held constant. As shown in the following graph, HP is improved from midrange to top end. And note the precision of the control of fuel flow by the Power Commander.
SHRINK WRAPPED vs BATHTUB HEADS and BLOCKS
A few weeks ago I got my first close look at the Ford FR9 NASCAR race engine designed by RoushYates on an episode of “How It’s Made”. In this program, we can see how both the heads and block have that “shrinkwrapped” appearance—the external surfaces closely match the perceived shapes on the internal structures of the heads and block!
Here’s a good side view photo of the engine:
HTG POLARIS 1080 TRIPLE w/ GUS BOHNE TURBO SYSTEM
Gus has the carb issues on Art Bass’ turbo 1080 resolved, and now we were able to tune it on the dyno. But it didn’t take long to see that the triple pipes on this sled were too short, causing HP to climb with revs until I let off the throttle at 9800! Note that torque has not yet peaked at 9800. But if I stayed into the throttle the torque and HP peaks would surely have gone beyond 10,000, totally unnecessary with a big boosted engine like his. So Gus is going to lengthen the pipes enough to bring peak power down into the 8500-9000 RPM range. Then he and Art can come back to DTR and turn up the boost!