Bonneville Salt Flats 2007 – A DSM Diary

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Photo by Thomas “Porkpie” Graf, Copyright 2007, All Rights Reserved

A good friend of mine has an AWD Eagle Talon with nearly 300,000 miles on it.  His daily driver is also used as a Bonneville racer.  Here is his tale of this year’s visit to the salt flats:

“We had a great time on the Salt this year all things considered! The car pulled strong and was way faster than its ever been with the new T67 turbo, but I definitely didn’t get the results I’d hoped for as I cracked/melted the #4 piston crown, melted off the spark plug electrode, and broke some pieces of both exhaust valves in that cylinder just past the 1 mile on the first run and coasted through the 2 mile trap at 123.xxx on 3 cylinders. #4 had the lowest compression to begin with, and the likely cause was some oil getting up past the rings igniting some carbon which caused severe pre-ignition. I hoped it had just burnt a valve which I could’ve gotten fixed in Salt Lake City, but when I pulled the head it was instantly apparent I was all done for this year. I don’t feel too bad as blowing up while racing wide-open at Bonneville after 283K is an honorable death for the engine. I attached a couple pics of the damage, and one about 100 yards off the starting line on that run taken by a professional photographer. I was surprised at how clean the piston crowns, combustion chamber, and valves were after only running one tankful of e85 through the engine. The last time I had the head off to replace a burnt exhaust valve in #4 at 255K all the crowns and valves were thick with carbon deposits. 105 octane E85 is a great affordable racing fuel($2.09/gal.), but I’m guessing it was the source of the carbon coming loose that pre-ignited.

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On the bright side, rather than re-build my 7-bolt engine, I’ve got a 6-bolt block and crank in the machine shop, a set of Ross pistons, Eagle rods, ARP head studs, 6-bolt ACT forged flywheel(to replace the almost brand-new 7-bolt ACT forged flywheel we installed < a month ago that I’ll be re-selling), Crower 280 cams, and an RRE 2G to 1G cam angle sensor harness in transit, picked up a new oil pump housing/gears, timing belt, balance shaft block-off parts, gasket set, and water pump from the Mitsu dealer yesterday, and will also be picking up a newly-rebuilt ported/polished head with SS valves that a CoDSM friend has ready at the machine shop (he ran out of money after dropping it off and can’t afford to get it for his car); and best of all, the back-ordered 4″ inlet/2.5″ outlet T67 compressor housing will finally be available next week that PTE is sending me even-exchange for the 3″ in/2″ out housing they mistakenly-shipped me in July, so I won’t have to pull the turbo off again after dropping in the race engine. So in a few weeks it should be up and running again better than ever, and with a few more safety mods over the next eleven months it should be able to run in BGT or PS at the SCTA-BNI meets as well as WoS next year!”

Rolling resistance on salt is much higher than cars see on asphalt or tarmac.  Here are photos of the difference in wheels and tires that this makes:

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The six bolt engine that he is talking about refers to the number of bolts used to hold the flywheel on to the crank shaft.  The earlier versions of the venerable Mitsubishi 4G63 engine used just six bolts and were known to be stronger and more reliable than the seven bolt version that came in the second generation Eagles and Eclipses.  So while it was frustrating for James to lose an opportunity to make some speed on the salt flats this will give him an excellent excuse to build up a much stronger engine for next year’s event.

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One Response to Bonneville Salt Flats 2007 – A DSM Diary

  1. markitude says:

    His explanation on the pre-ignition sounds plausible. While he didn’t mention, how did he retune for the E85? Alcohol has a lower specific density, so while the octane when up, and hence the resistance to detonation, it is also inherently leaner if you inject the same amount. Of course, with my reasoning, he should have burned more than one.

    Although it being so clean seems to indicate it ran hot and lean on all….

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