Justin Fuller came yesterday with his R1 bike turbo kit prototype to do additional dyno tuning, and compare a different Garrett ball bearing turbo design with hopefully a bit less turbine inlet backpressure.
He had been here a few weeks ago using my rear wheel roller dyno for preliminary tuning, on 93 octane we made 195 DJWHP (DynoJetWheelHP) at 11,500 at 5.5psi boost and 11.5/1 A/F ratio. Leaning down to 12.5/1 added 5 HP to 200 DJWHP even, the number Justin was shooting for for pump gas advertising purposes. Some time during extensive road testing, Justin experienced some plug speckling (detonation) at high speed, top gear after over three miles at WOT(!!!), maybe 180mph plus?
I suggested to Justin that NA engines converted to turbochargers on pump gas are best used for acceleration in short bursts, and anyone who wants to do bonneville-style top end blasts should spend $20 for better gas to protect their $5000 engines. But Justin being a perfectionist was interested in seeing what we could get away with by switching to a Garrett ball bearing turbo with less backpressure. So he sceduled additional dyno time for yesterday.
This time we took the extra effort to dyno the R1turbo on my SF901 dyno. This required creating a custom shaft adaptor out of the R1 output shaft (please don’t call it a “countershaft”) sprocket. Measuring the torque and HP at the output shaft is perfectly accurate; the computerized absorber servo controls engine speed, and eliminates some guessing that accompanies drum acceleration due to mass value estimation and tire slip. With shaft connection, the dyno measures exact output shaft information, then computes engine RPM via the primary and transmission gear ratio. Also my 901 is more completely instrumented than my Cycledyn roller (that will change shortly). With the 901 engine dyno Justin could monitor fuel pressure, boost, exhaust backpressure, and get actual mechanical measurement of fuel flow with one meter measuring fuel from pump to rail, then another meter subtracting the fuel that gets bypassed back to tank. A fuel line nightmare, but very effective. The 4″ air turbine measures CFM, and converts that airflow to pounds of air per hour, and A/F ratio.
Justin brought the bike just as it ran on the Cycledyn at 195djhp with 11.5/1 A/F ratio to obtain a new baseline measuring, without any loss from chain and tire. He wanted fresh pump gas to test with and I sent him around the corner to a gas station that usually sells you 93 when you try to buy it. Being a single hose multi-grade pump, the first of the three gallons of 93 that Justin bought was pumped into his truck, the next two were saved for testing (there surely is a quart or two of 87 in the mixing chamber/ pump/ hose that hits your vehicle before the good stuff gets there. Whenever you see a motorcyclist cruising around slowly looking at gas pumps before he stops at one to fill up, he’s surely trying to find a pump that just delivered high test, meaning he’s more likely to get 100% of whatever is in the “high octane” tank in the ground.
With two gallons of his newly bought gas and the engine well warmed up it peaked at 171 SAE HP at the output shaft peaking at only 10,300 RPM then dropping like a rock. Exerything mechanically looked good, fuel pressure, boost etc were fine. Leaning the fuel down to 12/1 caused HP to drop even more! Remember last time we dyno’d the bike we picked up 5 DJHP by leaning to 12.5/1.
Then Justin connected his custom deto sensor to the engine block, and he detected severe detonation just as the HP dropped on our real time HP graph on the computer screen.
Justin then enrichened his fuel flow to 10.5-10.8/1 and the subsequent dyno numbers carried HP all the way to 11.800 rpm where it made 198 SAE output shaft HP! The quiet but deadly sound of deto had subsided, and HP returned as the result of cooling combustion chamber temps with extra fuel. I was miffed that I hadn’t thought of that, and Justin assured me that even with my moderate age-induced dementia I would have thought to enrichen mixture, eventually. This change was so dramatic, I need to try to post a Jpeg graph on this weblog.
So Justin sucked all of that mystery gas out of the tank, and refilled it with fresh 106 octane leaded gas. Then turning up the boost to 9psi, the engine was happy making 230 SAE output shaft HP at 10.8/1 A/F ratio, .60 lb/hphr BSFC. Justin tried leaning the fuel back down to 11.5/1 and the engine picked up enough HP to haze the clutch (stock plates w/ stiffer springs) so dyno info from that point on was useless. So those of you who might have heard Justin and I talking about 300HP, it was the engine slipping and grabbing the clutch, causing torque and HP spikes that mometarily fooled us.
Based upon Justin’s RX1 and Apex sled turbo numbers, 300-400 HP is surely doable with lots of octane.
But for now, I believe Justin has had an eye-opening experience with “high test” pump gas. If he is to sell these kits for pump gas, he must tune each kit to 10.5/1 on boost. Car and Driver Magazine just reported that of something like 1500 samples of high test pump gas purchased in Michigan then tested for octane, more than 10% were low octane. Also maybe 10 years ago Dateline NBC did a private assessment of gas grade cheating by gas stations in CA, where they found one in eight substandard, with the worst testing out at 75 octane! That’s too much of a gamble knowing that 8- 10% of fillups can destroy an engine tuned for max HP on high test gas, if deto sensing and protection is absent.
I complained to the Bureau of Weights and Measures about this bad gas purchase, and the director is going to that gas station, same pump, and take a sample today to be tested next week. I’ll be anxious to hear the test results when they are finished.