what determines and engines RPM max?
Evolving Member
Joined: May 2008
Posts: 138
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From: Long Beach, CA
based on my experience with k20a and this 4b11t.... check out the following
86x86 meaning this is a square motor
k20's stock can rev to 8600 daily, 8000 rpm road race on stock valve train
k20's limiting factor is the piston, anything after 8600 rpm is suspect and your just asking for the piston to break away at the wristpin... the stock rods and rod bolts can take 9000rpm road race and 9200 drag race b4 they become suspect; the most power i seen on a stock k series rod is a lil over 700 crank hp reving to 8600
with the above being said...
the 4b11t is built for boost where as the k20 is not, both the 4b11t and k20a have the same bore and stroke
we know when the stock springs float on a k20a which is 9200, when does this occur on the 4b11t?
we know what the danger zone for the k20a piston which is anything above 8600 daily or 8000 road race, at what point is this the same for the 4b11t?
now, what is the weakest link in the 4b11t, is it the piston, or is it the rod?
based on the power delivery of these engines and how they breath, i dont think anyone is really going to be able to push the limit in a practical sense
piston speed 86mm stroke
7500rpm 4232.28 FPM
8000rpm 4514.44 FPM
8600rpm 4853.02 FPM
most high performance stock engines stay under 4700 FPM so i see no reason why you cant rev the 4b11 with its given stroke to 8k+ daily granted its making power that high, if the power is nose diving starting at 7600, no need to take above 8k
my 2c
86x86 meaning this is a square motor
k20's stock can rev to 8600 daily, 8000 rpm road race on stock valve train
k20's limiting factor is the piston, anything after 8600 rpm is suspect and your just asking for the piston to break away at the wristpin... the stock rods and rod bolts can take 9000rpm road race and 9200 drag race b4 they become suspect; the most power i seen on a stock k series rod is a lil over 700 crank hp reving to 8600
with the above being said...
the 4b11t is built for boost where as the k20 is not, both the 4b11t and k20a have the same bore and stroke
we know when the stock springs float on a k20a which is 9200, when does this occur on the 4b11t?
we know what the danger zone for the k20a piston which is anything above 8600 daily or 8000 road race, at what point is this the same for the 4b11t?
now, what is the weakest link in the 4b11t, is it the piston, or is it the rod?
based on the power delivery of these engines and how they breath, i dont think anyone is really going to be able to push the limit in a practical sense
piston speed 86mm stroke
7500rpm 4232.28 FPM
8000rpm 4514.44 FPM
8600rpm 4853.02 FPM
most high performance stock engines stay under 4700 FPM so i see no reason why you cant rev the 4b11 with its given stroke to 8k+ daily granted its making power that high, if the power is nose diving starting at 7600, no need to take above 8k
my 2c
Oh, well that's interesting.
Thing is, there might not be room on that on the 4B11. I can barely manage to use a rod bolt stretch gauge on other engines when they're out of the car! I usually just keep track of the bolts and rods and tighten them in a vice, torque until I get the desired stretch, and make notes. Gets it pretty spot on typically. I know it can be argued that that is completely pointless and counterproductive, but meh
Thing is, there might not be room on that on the 4B11. I can barely manage to use a rod bolt stretch gauge on other engines when they're out of the car! I usually just keep track of the bolts and rods and tighten them in a vice, torque until I get the desired stretch, and make notes. Gets it pretty spot on typically. I know it can be argued that that is completely pointless and counterproductive, but meh
Last edited by Bighec; Dec 1, 2009 at 09:30 AM.
Evolving Member
Joined: May 2008
Posts: 138
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From: Long Beach, CA
what was the oil pressure and oil temps when the bolts gave? has the motor ever been overreved and or has the owner or drive had/have a habit of laying on the rev limiter while racing, etc...
there is alot of untold abuse that kills engines....
Quite true, revving to 8500 is one thing, doing so with engine knock, rev limiter bouncing, or over revving past the limiter is quite another.
Newbie
Joined: May 2009
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From: Southside Chicago, Illinois
Evolved Member
Joined: Jun 2007
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From: tsukuba turn 4
another thing to consider that was not mentioned yet is rod length and/or rod ratio. rod ratio has a big effect on piston acceleration as well as piston side loads, etc.
the4B11 happens to have a rod ratio of about 1.75... if i remember correctly the K20A had something like a 1.62 rod length/stroke ratio. and the JDM Type R had a 8600 redline so in terms of internal engine geometry, the 4B11 already has a leg up....
and it also approaches the F20's rod ratio of about 1.8 so as long as everything else holds up happy revving
mitsu/GEMA did a good job on this one. 4G63 what? LOL!
the4B11 happens to have a rod ratio of about 1.75... if i remember correctly the K20A had something like a 1.62 rod length/stroke ratio. and the JDM Type R had a 8600 redline so in terms of internal engine geometry, the 4B11 already has a leg up....
and it also approaches the F20's rod ratio of about 1.8 so as long as everything else holds up happy revving
mitsu/GEMA did a good job on this one. 4G63 what? LOL!
Last edited by madfast; Dec 2, 2009 at 02:13 PM.
Evolved Member
Joined: Jun 2007
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From: tsukuba turn 4
And for what its worth the K20 has already answered the open deck question. the 4B11 just reinforces it. 600 and now 700 hp evo x's on stock block? just 2 years ago IX owners were balking at that idea...
Don't worry about the rod:stroke ratio on this motor. Your biggest limitations on the stock motor are the rod and controlling valve bounce
Last edited by DRAG; Dec 4, 2009 at 03:12 PM.
Evolving Member
Joined: May 2008
Posts: 138
Likes: 0
From: Long Beach, CA
another thing to consider that was not mentioned yet is rod length and/or rod ratio. rod ratio has a big effect on piston acceleration as well as piston side loads, etc.
the4B11 happens to have a rod ratio of about 1.75... if i remember correctly the K20A had something like a 1.62 rod length/stroke ratio. and the JDM Type R had a 8600 redline so in terms of internal engine geometry, the 4B11 already has a leg up....
and it also approaches the F20's rod ratio of about 1.8 so as long as everything else holds up happy revving mitsu/GEMA did a good job on this one. 4G63 what? LOL!
the4B11 happens to have a rod ratio of about 1.75... if i remember correctly the K20A had something like a 1.62 rod length/stroke ratio. and the JDM Type R had a 8600 redline so in terms of internal engine geometry, the 4B11 already has a leg up....
and it also approaches the F20's rod ratio of about 1.8 so as long as everything else holds up happy revving
mitsu/GEMA did a good job on this one. 4G63 what? LOL!and good point on the r/s ratio, i havent looked that far into the 4b11 yet
Evolving Member
Joined: May 2008
Posts: 138
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From: Long Beach, CA
revs to 9600 rpm and maintains a rpm of 8600-9600 over a minute and a half....
with that being said, the 4b11 is fine especiall since it has more bracing...
all this paranoia with a aluminum block should be thrown out the door especially seeing what hondas can do...