MrBean Member 400 Member For: 18y 7m 12d Location: Melbourne Posted 06/04/10 02:35 AM Share Posted 06/04/10 02:35 AM (edited) The 698Kw with the right spec's and the right surroundings will spin safely to 7400-7500rpmThe 998Kw with the right spec's and the right surroundings will spin all the way to 7800-8000rpmOuch, I dare say that even if you can provide a custom crank with decent counter-balance weights, and lighter than stock rods to change the amplitude and frequency band of the inherent straight 6's harmonics, you most likely won't have a very reliable valve-train going past the 7k rpm mark on these engines. Good for dyno-runs, but not reliable for consistent high-speed operation.Not to dis Atomic engines, this is an inherent straight-6 characteristic.What's your expereince, guys? Of course the ultimate would be to have a 7,500 rpm (reliable/repeatable)revver, and spread this massive torque induced by 20+psi boost levels to a wider rpm band, preventing the crank hammering the poor maincaps to death - but, I just cannot see this make for a reliable and trouble-free engine? Edited 06/04/10 02:35 AM by MrBean Link to comment Share on other sites More sharing options...
Ace blind leading the blind Member 3,657 Member For: 16y 3m 7d Gender: Male Location: Mt Alford, Queensland Posted 06/04/10 04:52 AM Share Posted 06/04/10 04:52 AM spiros last engine was 77000kms old when it lost oil pressure - I dont know if its just the new engine or both but he spins them to 7400rpm and drives it daily Link to comment Share on other sites More sharing options...
SPIKO Gold Donating Members 1,924 Member For: 19y 8m 11d Gender: Male Posted 06/04/10 10:10 AM Share Posted 06/04/10 10:10 AM Ouch, I dare say that even if you can provide a custom crank with decent counter-balance weights, and lighter than stock rods to change the amplitude and frequency band of the inherent straight 6's harmonics, you most likely won't have a very reliable valve-train going past the 7k rpm mark on these engines. Good for dyno-runs, but not reliable for consistent high-speed operation.Not to dis Atomic engines, this is an inherent straight-6 characteristic.What's your expereince, guys? Of course the ultimate would be to have a 7,500 rpm (reliable/repeatable)revver, and spread this massive torque induced by 20+psi boost levels to a wider rpm band, preventing the crank hammering the poor maincaps to death - but, I just cannot see this make for a reliable and trouble-free engine?As stated previously buddy, with the right surroundings they spin where I said they spin all day every day... I will soon share with you the harmonics of a straight 6 spinning to 9000+rpm be patient. Link to comment Share on other sites More sharing options...
MrBean Member 400 Member For: 18y 7m 12d Location: Melbourne Posted 06/04/10 10:22 AM Share Posted 06/04/10 10:22 AM (edited) Thanx Spiro, appreciated.Experience with V8's tells me that valvesprings tires very quickly at 7,500 rpm, where you can do approximately 400 1/4 mile runs at this speed, and then, once hitting 8k rpm, only about 50 runs at that speed.Don't know the dynamics of a more modern valve-train on the inline 6 though, but, of course, if you have a very customised crank, with Mallory slugs et al, and very well counter-balanced crank, you might have the harmonics sufficiently up in the rpm band to have a trouble-free bottom end at around 7,500rpm mark. But, running "all-day/every day" at these rpm-levels, well, let's say I would like to see that first.Again, proof is in the pudding, and I'm not flaming or anything such, just that it's going to cost an arm and leg to try and get any sort of reliability out of these engines at the levels you're talking.I don't believe it can be achieved with the heavy rods used in the 998 motor, as the heavy rods are just aggrevating the harmonics'problem in an engine already suffering of to small/light counterweights on the crank - maybe using super-expensive Titanium rods will get you there wrt harmonics, but, then again, not reliably so.I would luv to see the trends done on each bearing-cap with vibration-sensors mounted and captured at say, 20-30ms intervals If you don't mind, please share those you have with the 9k rpm engine.Have a good one, and talk later again. Edited 06/04/10 10:27 AM by MrBean Link to comment Share on other sites More sharing options...
tray_182005 Member 1,226 Member For: 15y 4m 11d Gender: Male Location: Wee Waa/NSW Posted 06/04/10 10:22 AM Share Posted 06/04/10 10:22 AM 9000.What is it a 2 stroke ? Link to comment Share on other sites More sharing options...
GR8XR6 ANGEL EYES Silver Donating Members 1,683 Member For: 16y 4m 26d Gender: Male Location: SE Suburbs, Melbourne Posted 06/04/10 10:25 AM Share Posted 06/04/10 10:25 AM As stated previously buddy, with the right surroundings they spin where I said they spin all day every day... I will soon share with you the harmonics of a straight 6 spinning to 9000+rpm be patient. Mmmmmm looking forward to this! Keep up the great work! Link to comment Share on other sites More sharing options...
SPIKO Gold Donating Members 1,924 Member For: 19y 8m 11d Gender: Male Posted 06/04/10 10:46 AM Share Posted 06/04/10 10:46 AM Thanx Spiro, appreciated.Experience with V8's tells me that valvesprings tires very quickly at 7,500 rpm, where you can do approximately 400 1/4 mile runs at this speed, and then, once hitting 8k rpm, only about 50 runs at that speed.Don't know the dynamics of a more modern valve-train on the inline 6 though, but, of course, if you have a very customised crank, with Mallory slugs et al, and very well counter-balanced crank, you might have the harmonics sufficiently up in the rpm band to have a trouble-free bottom end at around 7,500rpm mark. But, running "all-day/every day" at these rpm-levels, well, let's say I would like to see that first.Again, proof is in the pudding, and I'm not flaming or anything such, just that it's going to cost an arm and leg to try and get any sort of reliability out of these engines at the levels you're talking.I don't believe it can be achieved with the heavy rods used in the 998 motor, as the heavy rods are just aggrevating the harmonics'problem in an engine already suffering of to small/light counterweights on the crank - maybe using super-expensive Titanium rods will get you there wrt harmonics, but, then again, not reliably so.I would luv to see the trends done on each bearing-cap with vibration-sensors mounted and captured at say, 20-30ms intervals If you don't mind, please share those you have with the 9k rpm engine.Have a good one, and talk later again.Looking at the carefull wording in your post's I would say that you have built or experienced an engine build or two in your time Mr. Bean.... Would this be correct?To answer your first question where do you live? If it's in Brisbane I have no issues proving this to you.. All day everyday....Do not take the current status quo of knowledge as an absolute my friend, because if we all did that we would still be in the stone age.... Get my drift? I will share as stated when I'm ready my good and curious friend, however taking in to consideration the firmness of your statements this tell's me that you have not done sufficient research on the straight 6's, because if you had done so you would already be aware that they have revved to 11,850rpm Link to comment Share on other sites More sharing options...
MrBean Member 400 Member For: 18y 7m 12d Location: Melbourne Posted 06/04/10 10:53 AM Share Posted 06/04/10 10:53 AM Heya Spiro,Point well taken Thanx. Yep, you're spot-on, I have quite good experience with Ford small-block V8's, having put together pretty powerful beasts back in the Republic up to the mid-90's - but I'm not that familiar with the Aussie 6.I have no doubt they can rev, but only concern was for the reliability at high-rpm's....but, I am always ready to learn from someone more experienced, and, wrt this particular inline 6, that is from almost everyone!But, appreciate the work that blokes like you and others are putting in so us noobs can put together semi-decent street-performers - my current UTE is making a measley 370rwkw....sad, I know.One of these days I will start a 500rwkw built - no need for more power for my application though, even though I would probably opr for something that would be able to accommodate 1000-1200hp....Will be in touch, and have a good one in Brisvegas. Link to comment Share on other sites More sharing options...
SPIKO Gold Donating Members 1,924 Member For: 19y 8m 11d Gender: Male Posted 06/04/10 11:23 AM Share Posted 06/04/10 11:23 AM Anytime.. Link to comment Share on other sites More sharing options...
winstor Member 611 Member For: 15y 9m 20d Posted 06/04/10 12:10 PM Share Posted 06/04/10 12:10 PM Must hear the 9000rpm sound....I NEED TO HEAR IT!!!! Link to comment Share on other sites More sharing options...
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