"did you peeps know that a 4 cylinder inline engine has a bad vibration band at 3000 and 6000 revs...which is concentrated onto the no.3 bearing, well, now you do, so if you can avoid it don't run your hopped up engine at 3000 revs for an extended period of time (like at cruise speed), also don't shave the flywheel for the same reason- vibration is satan's spanner! "
Interesting Surely though the revs this happens at would alter due to stroke and piston mass. My old 4jb1 had a very definate harmonic at 2200 If you search back 10 years on here you will find my posts about it Only know about it because of an intercooler bolt that was too long meaning it was tight be the washer on it wasnt. Between 2150 and 2200 it fair screamed.
As far as Im aware these motors are just built from a parts bin where all parts have been weighed measured etc to within tolerances. They are not race engines and only rev to 4k so thats good enough. As it is modern techniques probably are better on mass produced parts nowdays than an expert blueprinter would of been 20 years ago.
4JH1T timing gears
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Roderunner
- Posts: 39
- Joined: Mon Feb 27, 2012 11:55 pm
Re: 4JH1T timing gears
geeves wrote:Interesting Surely though the revs this happens at would alter due to stroke and piston mass.
From what I understand the 3000 and 6000 vibration band is inherent in all inline fours, no matter what the stroke or piston mass, and is not really a problem until the engine is being stressed by loads that are beyond the engines design spec, like very high peak pressure spikes.
My old 4jb1 had a very definate harmonic at 2200 If you search back 10 years on here you will find my posts about it Only know about it because of an intercooler bolt that was too long meaning it was tight be the washer on it wasnt. Between 2150 and 2200 it fair screamed.
I don't doubt your claim at all, apparently there is a wide range of harmonics that can affect an engine, especially a diesel. The 4jg2 has a bad vibration at about 1000 revs, so going around a slow corner in top gear nearly vibrates the fillings out of my teeth, not that I like to lug the engine, I'm just trying to avoid a gear change.
As far as Im aware these motors are just built from a parts bin where all parts have been weighed measured etc to within tolerances. They are not race engines and only rev to 4k so thats good enough. As it is modern techniques probably are better on mass produced parts nowdays than an expert blueprinter would of been 20 years ago.
I wouldn't want to work on the later design engines after hearing how careful the assembler has to be, for instance when fitting a head gasket onto a certain late model Ford engine you arn't allowed to leave any fingerprints on the gasket's surface as this contamination can lead to another blown gasket. Finicky to the extreme. I have to say that the 4jg2 is very smooth when operated in the correct rpm band, but the tune plays a part too, injection timing seems to be the biggest factor, not to mention the correct viscosity oil.
There is a lot of info on engine harmonics, it gets a bit indepth though, here's one of the more interesting sites- http://www.epi-eng.com/piston_engine_te ... ngines.htm
From what I understand the 3000 and 6000 vibration band is inherent in all inline fours, no matter what the stroke or piston mass, and is not really a problem until the engine is being stressed by loads that are beyond the engines design spec, like very high peak pressure spikes.
My old 4jb1 had a very definate harmonic at 2200 If you search back 10 years on here you will find my posts about it Only know about it because of an intercooler bolt that was too long meaning it was tight be the washer on it wasnt. Between 2150 and 2200 it fair screamed.
I don't doubt your claim at all, apparently there is a wide range of harmonics that can affect an engine, especially a diesel. The 4jg2 has a bad vibration at about 1000 revs, so going around a slow corner in top gear nearly vibrates the fillings out of my teeth, not that I like to lug the engine, I'm just trying to avoid a gear change.
As far as Im aware these motors are just built from a parts bin where all parts have been weighed measured etc to within tolerances. They are not race engines and only rev to 4k so thats good enough. As it is modern techniques probably are better on mass produced parts nowdays than an expert blueprinter would of been 20 years ago.
I wouldn't want to work on the later design engines after hearing how careful the assembler has to be, for instance when fitting a head gasket onto a certain late model Ford engine you arn't allowed to leave any fingerprints on the gasket's surface as this contamination can lead to another blown gasket. Finicky to the extreme. I have to say that the 4jg2 is very smooth when operated in the correct rpm band, but the tune plays a part too, injection timing seems to be the biggest factor, not to mention the correct viscosity oil.
There is a lot of info on engine harmonics, it gets a bit indepth though, here's one of the more interesting sites- http://www.epi-eng.com/piston_engine_te ... ngines.htm