Discussion in 'Stage II Tech' started by Alky V6, Feb 18, 2012.
Who's to say a 3.625 stroke can't turn 9,000 rpm??
That's kinda like saying, who says a 200-4R can't stand up to 1,000+ hp?? Or, building up a 109 block to do 8s.
It might. But, for how long?
Traction may not be as bad as you think. Power will probably ramp in slower and help get off the line.
Traction has not really been a problem at the launch. Actually, I could use a little more power about 15-20 feet out. Power wasn't ramping in quick enough. A problem associated with having the boost ramp-up closely tied to the rpm ramp-up. The ramp-up association was very safe. There was little chance of ending up with too much boost at too low of a rpm. Still, I was able to coax a 1.27 60' out of the car.
The traction problem came in at the 1-2 shift, about 80 feet out. Much of the problem is associated with the track, though. The owners of the track have been discussing what to do about the track, lately. Maybe they'll have the track fixed by the time I have the car back together. Otherwise, I'll be traveling to Vegas, or some other well prepped track to do the big boost testing.
What's different in a Buick than every other engine in the world that doesn't allow it to turn 9000 rpm with a 3.625 stroke when there are engines with more stroke than that turning that same rpm?
An interesting quote from a book in my library.
"In comparing and contrasting the even-fire/odd-fire 90-degree V-6s of Buick and Chevy, the even-fire design appears preferable (though marginally so) for performance applications. Torsional stresses imparted to the crank by uneven torque pulses seem to be more detrimental than unbalance forces. Use of a heavier flywheel to dampen torque fluctuations (as is Detroit's practice) also reduces engine response. And the uneven firing sequence could cause some ignition problems."
Another early book I have states, even before the unmachined BMS forged cranks would actually become available, the announcement from Buick's Product Engineering department was that the stroke capability for the expected new forging would be 2.66" to 3.40".
Why the early recommendation to only 3.4"? Were the Buick engineers skittish about suggesting pushing the split journal to a 3.625" stroke?
The initial plans are to pull the old engine, tear it down and mount the block and new heads back in the car so that I can start fabricating the new intake and exhaust headers. I have a Stage II tunnel intake that I may use as a starting point for the intake. It's had some modifying done to it by a previous owner, but that shouldn't be a problem.
The exhaust headers are going to be like nothing ever seen before. The specs will be surprisingly outrageous.
Hmmmm. I know of several 3.625 stroke engines turning 9000 rpm. I have never heard of a problem with it if the engine was built right. To me if rpm is the issue then it's time for more stroke...less rpm....same power. Benefits will be extra low end torque and increased reliability.
The issue of the split journal 3.625" stroke has nothing to do with the engine being 'built right'. The issue is the cycle life of the part. Lessening the area of the split journal AND pushing it to extreme stress levels (high rpm) has to lower the cycle life of the part. For those shooting for a record, and can afford to pull an engine down after so many cycles and have the crank checked for cracks, I'm sure it's worth the expense to them. For me, I can only afford to worry about valve springs. I expect this engine to last around 3 years with nothing more than valve adjustments, oil and filter changes, and maybe a valve spring set replacement.
Didn't Neal bring up that he recently came across a couple of stroker cranks that had cracks in them? Obviously coming from a source that had learned when to change out their stressed to the limit cranks before the whole engine got taken out.
Donnie what gear is in your car that will bring you to close to 9000 rpm at the traps?
3.73:1 with 29.5 x 10.5 - 15W tires. Actual running diameter 28.4" with a 3.3% tire growth. With the present TC, 12% slippage, should cross the finish around 8500-8600 rpm.
I would talk to Dusty 12% slippage is unacceptable.........the ptc units slip about 3.5-4% max.
I know, Norbs.
It's best to fully understand an application before a TC is picked out for it. When I feel I have enough information to relay to Dusty, I'll be looking for his help. Picking out a TC using sim work alone isn't going to do it. Let's wait until this thing is running, first.
I'm sure this is going to be a very unique match up for Dusty.
First things first.
Lately, I've been revamping the ECM software for the upcoming changes. More rpm, more fueling and more boost.
The fuel demand for a 1500 hp target using a BSFC of 1.35 for methanol fuel will be 2025 lbs/hr.
I plan on using 2 large Weldon electric fuel pumps, 2 - 160 lb/hr electronic injectors per cylinder and one mechanical nozzle per cylinder. This should cover the fueling needs, just barely.
Funny thing about short stroke motors. Sometimes they prefer more slip. 8-9% may be needed for it to perform the best. Donny will have a unique application for sure. I've done a few converters for these engine that will see 9,000 rpm and I can say the commonly used 9.5 like I use in most of these cars will likely be too tight for that much rpm. I feel I would end up with something more like a blower converter in it. Something with a high flash rpm that won't get so tight with rpm. This is the great thing about a high rpm range. It allows you to loosen it up down low to aid in spool-up.
When I say "built right" I'm meaning avoiding the Chinese junk. A billet crank and good rotating assembly is a must. Usually these types of engines are ran on the ragged edge so something usually gives up before the crank. Head gaskets...aluminum rods that need replaced at 60-80 passes. But these are also pumping out 1800hp so you can expect some maintenance on them.
Holy smokes... This thing is going to be busy!
The preliminary fuel map is ready for testing.
Two step downs. The first for when the other set of E injectors come online, and the second for when the set of mechanical nozzles come online.
The fueling will be just enough to allow a 42 psi boost level at 9,000 rpm. The fueling will be maxed out at that point.
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