Hybrid stroker project
11-27-2013, 01:28 PM
#526
Thanks. In what cases does it happen? Do you recall any general perameters? Are you differentiating hot-spot pre-ignition and actual detonation of the charge before the spark event due to cylinder pressures?
11-27-2013, 01:41 PM
#527
Race Car
Sid, I'm looking through a Wossner catalog, and found the same thing you did. The Mitsubishi rod at 26.4mm wide is closer than anything else out there to the 28.8mm wide Porsche rod. That is still a whole heap of slop, isn't it? How did you address that?
11-27-2013, 02:04 PM
#528
Sigh. There's a ton of misinformation out there. We used 108 when I was at Ford, Hot Rod is saying 105. http://www.hotrod.com/techarticles/h...l/viewall.html. As for the notion that it won't knock, given the right conditions, it will. Besides, continued increasing CR has diminishing returns. And on a 2V especially, the chamber shape can get really ugly, your surface area/volume ratio can get really unfavorable, and your thermal efficiency won't necessarily increase as it should.
On edit - Hot Rod differentiates between knock and pre-ignition. Knock really isn't a big deal, but it leads to PI, and PI is what breaks stuff. If E85 is more prone to PI, that makes it especially important you don't detonate, since the detonation creates hots spots, which cause PI.
On edit - Hot Rod differentiates between knock and pre-ignition. Knock really isn't a big deal, but it leads to PI, and PI is what breaks stuff. If E85 is more prone to PI, that makes it especially important you don't detonate, since the detonation creates hots spots, which cause PI.
I am reading that other link and will research more DSM people. I am simply in this conversation becuase I am building a stock block 32V V8 that will end up having about 12:1 CR. I will then start adding boost. I have a pulley for 28psi on the stock intake, so with my configuration it may be less than that as there is less restriction.
My theory (I have no applied knowledge of this package) is that warranting Pre ignition from hot spots, I will have a great motor that will not detonate with e85. If it detonates, its over.
These are all extra pieces, so its an experiment and no one will cry if it blows.
11-27-2013, 02:12 PM
#529
Race Car
Thread Starter
Harry, we used a wider radius. It really isn't much. Also, take a look at the width of the Porsche bearing vs journal. You'll see that it's a bit narrow in comparison.
There was no evidence of any excessive wear on the bearing edge to speak of. I posted a pic a couple pages back of well used bearings if you'd like to see them.
There was no evidence of any excessive wear on the bearing edge to speak of. I posted a pic a couple pages back of well used bearings if you'd like to see them.
11-27-2013, 03:26 PM
#530
Rennlist Member
The Eagle 4G63 Rods I am using have a BE width of 28.37 mm (small end for 7-bolt pistons, large end for 6-bolt crank). I discussed this with several local builders and all of them said it was not an issue. Like Sid, when I dis-assembled the 2.85L I found no evidence of a problem due to the small difference.
11-27-2013, 10:23 PM
#531
Burning Brakes
My personal engine is a 4V v8. Center plug. We found snowmobile plugs that have little protrusion to reduce PI on hotspots. Smoothed valve edges, etc. The head lift can still be a problem.
I am reading that other link and will research more DSM people. I am simply in this conversation becuase I am building a stock block 32V V8 that will end up having about 12:1 CR. I will then start adding boost. I have a pulley for 28psi on the stock intake, so with my configuration it may be less than that as there is less restriction.
My theory (I have no applied knowledge of this package) is that warranting Pre ignition from hot spots, I will have a great motor that will not detonate with e85. If it detonates, its over.
These are all extra pieces, so its an experiment and no one will cry if it blows.
I am reading that other link and will research more DSM people. I am simply in this conversation becuase I am building a stock block 32V V8 that will end up having about 12:1 CR. I will then start adding boost. I have a pulley for 28psi on the stock intake, so with my configuration it may be less than that as there is less restriction.
My theory (I have no applied knowledge of this package) is that warranting Pre ignition from hot spots, I will have a great motor that will not detonate with e85. If it detonates, its over.
These are all extra pieces, so its an experiment and no one will cry if it blows.
11-28-2013, 04:56 AM
#532
Addict
Rennlist Member
Rennlist Member
28psi @ 12.5, shouldn't that be equivalent to grenade?
11-29-2013, 01:08 AM
#533
11-29-2013, 01:08 AM
#534
11-29-2013, 07:02 PM
#536
11-29-2013, 07:24 PM
#537
Addict
Rennlist Member
Rennlist Member
12-01-2013, 10:05 AM
#538
Race Car
He also mentions that he failed to find the knock limit of E85 even with port injection (though he later shows it at elevated temperatures). He failed to do so even with E10. But he also points out that it was a 9.2:1 engine designed to run close to MBT on gasoline. BEWARE OF EXTRAPOLATION. Later on, he does run sweeps, and it appears that you can run about 50% higher cylinder pressures with ethanol, but it does, indeed show that it will become knock limited.
All that said, that's a great reference. Much more readable than most theses I've read (and the one I wrote!!!!). Great reference, for certain.
Interestedly, I'm familiar with one of the strategies he mentions in his literature reveiw. The dual fuel, turbocharged DI one, where E85 is used wiht the direct injection system, and gasoline for hte port. Saw huge numbers. But again, that was with E85 in conjunction with direct injection.
About the baseline, we did see a small amount of benefit by moving to open valve injection with PFI, to attempt to realize some charge cooling. But it was quite minimal.
12-01-2013, 11:52 AM
#539
I was just thinking that the injection timing could be changed for charge cooling.
Yes, I understand he is investigating DI. It was a very informative read, and the thread I am most interested in is the lengths he had to go to make the fuel knock. With a nominal intercooler, intake temps are more like 20c to 40c instead of the 120c he took to get any knocks at all.
Yes, I understand he is investigating DI. It was a very informative read, and the thread I am most interested in is the lengths he had to go to make the fuel knock. With a nominal intercooler, intake temps are more like 20c to 40c instead of the 120c he took to get any knocks at all.
12-01-2013, 04:57 PM
#540
Race Car
I was just thinking that the injection timing could be changed for charge cooling.
Yes, I understand he is investigating DI. It was a very informative read, and the thread I am most interested in is the lengths he had to go to make the fuel knock. With a nominal intercooler, intake temps are more like 20c to 40c instead of the 120c he took to get any knocks at all.
Yes, I understand he is investigating DI. It was a very informative read, and the thread I am most interested in is the lengths he had to go to make the fuel knock. With a nominal intercooler, intake temps are more like 20c to 40c instead of the 120c he took to get any knocks at all.
Not trying to be argumentative. Just trying to point out things it looked like you didn't fully consider when targetting 12.5:1 in conjunction with 28 PSI.