BSE how many of you can feel the vibration?

[turboglenn]

Just as it says, i BSE'd this motor the "ghetto" way by taking out the rear and putting in a mirage stub shaft and then pulling the belt of the front one (it was done with the motor in the car) Anyway, I've always felt a little extra vibration, but yesterday i was driving and lugging around at about 2500 - 3k rpm and i could watch the mirror vibrate and the window shake in the door frame repeatedly.. Under light load it doesn't do this and it really only does it when you are lugging the motor in that RPM range.. 1st gear wont do it, i can feel it in 2nd and 3rd but once the load is off the motor you can't feel it and it's starting to make me wonder.

My last BSE motor was only in the car 1500 miles or so because the mains were sized wrong at the machine shop so i pulled it to throw this motor in as a "temp" and still haven't finished my other motor yet.

Anyone else feel this vibration from 2500 - 3500 when bogging around at low speed?

I can't find anything wrong, but am taking advice!

 

[turboglenn]

43 views and i'm only fortunate enough to have Defiant leave his signature in the form of an edit I feel loved

 

[Black_Bullet]

Anyone else feel this vibration from 2500 - 3500 when bogging around at low speed?

Yup, thats about were the messager kicks in, especially if you have prothanes...
More so at 2500-3000 for me, and the mirror does vibrate enough that when I look at the cars
behind me at this rpm they are all blurry and I have trouble identifing what kind of car it is if its far enough away... My car probably vibrates more than yours since I run open DP when my cutout is open, and Its dumps right under the driver seat pretty much , and Ive found that it intensifies sounds and vibrations and harmonics a lot more than a regular full exhaust setup would....

Try bogging your car in fifth at too low of an rpm, it feels like your motors about to snatch off your dashboard... My interior ( despite how gutted) actually does not vibrate too much which i am glad... Ive noticed 2g interiors are a lot more cheaper and flimsy than 1g interiors though.

Some ppl who ride with me dont say nothing about it, because they figure my car is just some kind of monster since I can pretty much destroy at least 90% of the street cars on the road out here in any kind of race...
Some ppl who ride with me who dont know about BSE or Prothanes just say my car runs rough.

 

[92awddsm]

I notice the vibration but I also have it the same in my 2g n/t with prothanes.

 

[spoonman]

I feel it bad but my car has no interior and has solid motor mounts. The worst vibration is felt at 2500-4000 RPM for me, when I am driving fifth at 45MPH. I do not find the vibration irritating at all though.

 

[Mr Peepers]

If I'm not mistaken, balance shafts are there to cancel the 2nd order force and have nothing to do with the load of the engine at all, only the accelerating and decelerating of the pistons/conrods. If it were balance shaft related, it would vibrate exactly the same depending on rpm no matter how much/how little load.

 

[2point3Tsi]

If I'm not mistaken, balance shafts are there to cancel the 2nd order force and have nothing to do with the load of the engine at all, only the accelerating and decelerating of the pistons/conrods.

Ah yes they are there for comfort. I have a 2.3 no BS and prothanes. minimal vibration at 1k, mirrors jiggle a little but once your on the throttle, smooth as silk. Its all about balancing your rotating assembly

 

[Mr Peepers]

Ah, I don't mean to sound like an ass, but balance shafts aren't related to the balance of the rotating assembly; only the second order vibration inherent with inline 4 cylinders. Sorry, I just have this thing where I don't want it to be taken wrong

 

[TunaTalon]

The 4G63 engine has balance shafts to cancel second order harmonic vibrations due to the velocity differences between the pistons. The piston going up does not exactly balance the piston going down because of the geometry.

Balance shafts have no effect on the balance of the rotating assembly. Balancing the rotating assembly has no effect on second order harmonics. The crankshaft and pistons are at the base frequency of the engine so that there is no way possible for them to compensate for the second order vibrations at two times the base frequency.

Second order harmonic vibrations are a function of RPM and reciprocating mass. The faster the engine goes the more vibrations. The reason we feel the vibrations more around 2500-3000 RPM is that's where the second order vibrations reach resonance with the chassis natural frequency. Kinda like blowing over a bottle and making a tone at the natural frequency of the bottle.


If you feel the need to learn more of the technical details, and have a high threshold of boredom, then please see my StrokeOrNot document at http://www.kidzuku.com/StrokeOrNot.pdf)