I've been following the reports & comments on the DynoTech blog & HCS. Some folks put way too much weight on dyno reports but I thought that Jim did a nice job & gave an honest report. Even fessed up to a burn down during the process. It looks like the Polaris 8 makes the advertised HP even though it took some help from a Polaris tech & good fuel. With low Octane fuel the sled made 145 HP & the second day they got it to 153. Some of my observations:
1. Good fuel is key to making HP-DT discovered that they had some bad fuel even though it was supposed to be 93 octane. With Ethanol on the rise & questionable fuel it's going to be a struggle to maintain peak performance.
2. Pipe temp isn't mentioned but the P 800 fuel map requires a hot exhaust to reach peak HP. The first dyno (last year) by Extreme in CO was low on HP but they ran with a cold pipe. Later Extreme gained HP when they tested with a hot pipe.
3. DT ran slightly lower coolant temps the second day, still not clear on cooling & they leaned the fuel mix using power commander. Assume that the fuel map is still on the rich side at that elevation.
4. They are testing several A.Mkt pipes but remember that DT is near sea level so a high elevation pipe like the SLP may not shine.
5. Why test 87 octane?, an Ethanol test would have been more appropriate. Then there's oxygenated fuel mandates in some areas. How do you know what you bought at the pump?
6. Octane decreases about a point per 1000' rise in elevation according to a Chevron friend. It is rated at the source so fuel shipped from sea level may show 93 octane yet be the equivalent of fuel from a higher elevation rated at 91. Are we going to need our own octane tester? Carry an octane booster?
The fact that DT spent 2 days on the dyno gives some indication of the complexity of the process, leaving room for variation in results. And the sled is not in the snow in real world operating conditions. Ambient temp, air density & adjustment for elevation are some other "estimates" that make dyno comparo's subject to interpretation.
I can't believe the posts on HCS-some folks making a buying decision based on dyno numbers. Lest we forget, clutching, track, & HP at the track are kinda important.
Here is Jim's post from HCS.
Just got home after 12 hours at the dyno. Not done just yet. As you guys have heard while watching the dynocams we had issues with detonation. Casey and his Dad and brother are heading home tow hours to Jamestown. Casey's sled is still on the table.
This is a hugely powerful 800 twin. Joe DiSpirito just autopsied their first dragon 800, and after degreeing/ measuring ports concluded that if he were building a full race 800 twin this is the port timing/ size he would use. It's all done.
So here we are, with piss 87 octane gas, and this engine is pumping 110 lb/hr fuel flow. No sign of knock either on the Digital Wrench Polaris diagnostic software, or my dandy copper tube bolted to the thermostat housing! 110 lb/hr = .80 BSFC and 145 HP. I dont care how you do the math this is the best HP possible out of a 800 twin with 110 lb/hr fuel flow.
With 87 octane, we tried sLP and BMP pipe mods, both detonated and had timing yanked into the cellar, no HP. So our pal Don Heale (White Lake Polaris dealer) bought us a jug of Sunoco 93. Better, but still some knock that yanked timing excessively. It was so bad, we unplugged the deto sensor and depended on the rattling copper tube to keep us safe. We made 157 with the BMP pipe mod, 150 with SLP single, 157 w/ SLP w/ Exxtreme pipe mod, with a few rattles along the way. Then being greedy and dumb, looking for 160, I used the Power Commander to tweak fuel lower with the Stock pipe BMP mod, and in midrange I heard 12 deto clicks and stopped the test at 7800 but it was too late. Wafted piston, but cylinder OK. Next time I will stop the test at 6 clicks!
Back at it with fresh parts, we used the Power Commander to lean down fuel flow with stock pipe, got to 152-3 HP with a few clicks at maybe 85 lb/hr on even newer 93 octane., but now we have an 1/8th inch thick nylon spacer between the knock sensor and head.
We stopped there, some anonymous Polaris tech support will be here tomorrow so we can assess this situation. Thank you guys who have been bugging Polaris about this today. The engine is very excellent--we just have to figure out these details to get all those nasty active radicals to mellow out and let us have some fun.
And you guys owe a thank you to Casey- Team Bayport for blowing off another day of work (and another tomorrow) to help you guys maximize your enjoyment of this sled. He's probably just getting home now as I post this.
Post from DT Blog:
10/1 AM Casey Mulkin production 09 dragon 800, pipe mods, SLP single, etc my brain is shot after 12 hours of testing changing swapping stuff. This is a hugely powerful engine, but it has been detonating easily, and when it does the ECM seems to overcompensate. Casey's sled baselined at 145, leaned out with Power Commander to 152ish but on the edge of rattling the ECU to big retard. Polaris technical people are flying in tomorrow, cams off, I need to show them what is happening here, maybe changes are in store...
10/2 Casey day 2--another 12 hour session, this one much more enjoyable, excellent technical support provided by Darren Hedlund of Polaris Engineering, finally were able to increase HP knock-free by operating at slightly lower coolant temps (increased airflow and reduced active radicals), monitored pipe backpressure, with what appeared to be real 93 octane gas (we were surely boned yesterday by rattling fake 93 Sunoco)...we tuned fuel down to 153hp with Power Commander, then were able to add custom exhaust parts and further fuel tuning to over 162HP, limited there by the octane of the fuel. 50 plus dyno tests to review with Casey, will try to compile that information this weekend, including four single pipes and the actual PCIII numbers we used to optimize fuel flow for each combination.
