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Engine Vibration after Manual Swap

Yep. There’s a whole thread on the topic. Those of us with T5s have it particularly buzzy.

That mentioned, you should post video.
 
Harlard said:
That?s just 2nd order resonant vibration. This is why Volvo used a 30 lb flywheel and 10 lb harmonic balancer coupled with mushy soft mounts. 96mm bore FTL.
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You can only be sure of that by testing the frequency of the vibration. And half engine rpm (misfire) is also 2nd order.
 
mikep said:
You can only be sure of that by testing the frequency of the vibration. And half engine rpm (misfire) is also 2nd order.
Click to expand...

Would you be able to elaborate on this a little bit so I can understand better? When you say testing the frequency, how would I go about that? Are there other symptoms I could see that would indicate misfire? And when you guys say 2nd order, are you talking about the order of a modeling ODE or something else?
 
I suspect the rubber dampened crank pulley is partly to dampen pulsation/crank deflection from the power stroke on #1 on the new smaller bearing journal cast crank engine?

Not the kind of thing w/ larger inline 4 buzz vibes/noise the driver is likely to actually feel, hear or perceive…
Inline 6 engines with much narrower bores that we don’t *hear* the vibes from often have more rubber/damper there with the long crank, among other reasons…

As to the dished flywheel, I suspect that’s more an across the board change?;
reduced pedal effort (larger clutch swept area, lighter pressure plate springs on n/a models, especially for equivalent torque capacity, longer clutch life to cut down (potential) warranty claims), tall fuel economy & minimal crankcase windage oriented gears in most all models by ‘87 / no more carbed 2.0/2.1 or larger cam/shorter final drive models remained in all markets by then;

1 parts bin, no real sport model those years, stump puller 1st gear in compliance with the very stringent Swiss law to take off fully loaded on steep grades, less burning the clutch getting out of steep hills/driveways loaded down in the 4cyl 5-7 seat mid-size family car? Make sense?
Doubt it has to do with vibes that we hear/feel, really? :e-shrug:

I think they just had some clutches & flywheels to use up for 85 & 86 n/a models; all turbo models already had the dished flywheel by then…

Not sure I buy that the flywheel & damper on the crank makes all that much difference? (In what we hear/feel for NVH?).

In fact, my low mile flat flywheel 1986 beater M46 245s ran quieter than their fatter rod/more reciprocating weight w/more tooling drift/worse balancing from the factory I suspect dished flywheel big rod 90+ cousins (engine noise/vibes resonant thru the drivetrain wise, anyway?)? :lol:
Tho, the later model car was quieter overall of course, particularly the last of the cloth seat 244s 92-93…

As to auto or manual, the main shaft is longer in the M46 than Aw, so I’d say namely that the fluid filled converter (& its clutch if equipped) dampen power pulsation moreso than the trans itself…accumulator function for shifts & little if any damping on the clutches & steels in the Aw otherwise…

Trans mount shenanigans & the springs in the clutch disc can transmit a significant amount of noise as can solid torque rod bushings.

The tri-pod engine mountings in shear should absorb the inline 4 up and down buzz reasonably well, but if dimensions change or one mount is bearing a lot more load or weight that can throw it all off & make for lots of cabin noise…

M47 models with the rectangular mount farther (stiffer up & down) back compared to other manual trans models w/lighter alloy cases gearbox used a wider spacing rubber dampened (at the mounting bolts) x-member as opposed to other models with the trans x-member being hard mounted metal-metal to the body.

Models with larger stiffer driveline use a rubber damper on the rear of the driveline (even the odd m51 v6 cars) or the guibo flex disc thing on m47 240s and all but early inline 6 700 diesel manual models.

The rear rubber vibe damper never seems to go bad in normal use before other parts fail/break in my experience on the large driveline M46 models & you don’t really notice it being so mushy on the clutch take-up like the flex disc on the trans output flange (tho stiffer discs were available & used on some Volvo models, butwas thinking if the M5 application flex disc…) , but no way to really service or replace the damper on models with rear section driveline damper, either?
3rd engine mount in rubber doesn’t seem to add vibes except on initial startup/ cranking…

Some of the 1980 model 242s I’ve had/driven were built crooked…but that was a road speed resonance thing…

Some late model cars had some noise from the axle & had rubber weights clamped to it. You see that on mid-late cycle cars sometimes…Volvo had some problems with them in warranty….

I went thru noise shens with the SR5 to GT-S AE86 bits (factory T50 which is a lot like a tighter tolerance Japanese copy of a borg warner T5, but smaller trans over-all) until I installed the rear rubber damper GTS driveline (same u-joint sizes except rear for the GTS LSD axle I had for it) but the SR5 driveline was much the same otherwise…
 
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TheLoganZilla said:
Would you be able to elaborate on this a little bit so I can understand better? When you say testing the frequency, how would I go about that? Are there other symptoms I could see that would indicate misfire? And when you guys say 2nd order, are you talking about the order of a modeling ODE or something else?
Click to expand...

Monitoring O2 sensor output (even better if you have additional wide-band one with the gauge) can help to register a misfire. Misfire will show as lean condition or very low voltage output.
 
Kjets On a Plane said:
Models with larger stiffer driveline use a rubber damper on the rear of the driveline (even the odd m51 v6 cars) or the guibo flex disc thing on m47 240s and all but early inline 6 700 diesel manual models.

The rear rubber vibe damper never seems to go bad in normal use before other parts fail/break in my experience on the large driveline M46 models & you don?t really notice it being so mushy on the clutch take-up like the flex disc on the trans output flange (tho stiffer discs are available & used on some Volvo models, even but I was thinking if the M5 thing?) , but no way to really service or replace the damper on models with rear section driveline damper,either?
3rd engine mount in rubber doesn?t seem to add vibes except on initial startup/ cranking?

Some of the 1980 model 242s I?ve had/driven were built crooked?but that was a road speed resonance thing?

Some late model cars had some noise from the axle & had rubber weights clamped to it. You see that on mid-late cycle cars sometimes?Volvo had some problems with them in warranty?.

I went thru noise shens with the SR5 to GT-S AE86 bits (factory T50 which is a lot like a tighter tolerance Japanese copy of a borg warner T5, but smaller trans over-all) until I installed the rear rubber damper GTS driveline (same u-joint sizes except rear for the GTS LSD axle I had for it) but the SR5 driveline was much the same otherwise?
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I think I remember seeing a rubber damper on the driveline of the later model, m47 240 that I took some parts off of. At the same time, I?m confident that the root of my issue is driveline independent, though I?m sure the mounting setup is amplifying the issue. I?m going to install a rubber version of the mount I?ve been using to see if that smooths things out.
 
PCH said:
Monitoring O2 sensor output (even better if you have additional wide-band one with the gauge) can help to register a misfire. Misfire will show as lean condition or very low voltage output.
Click to expand...

If the misfire was intermittent would a wideband gauge be able to respond to the rapid change in ratio fast enough to register? I?ve had an aem wideband installed for a while now ever since I had lean running issues soon after buying the car. I?ll try starting the car again tomorrow and really carefully watching the gauge while I hold the car at its ?beach boys? rpm.
 
TheLoganZilla said:
Would you be able to elaborate on this a little bit so I can understand better? When you say testing the frequency, how would I go about that? Are there other symptoms I could see that would indicate misfire? And when you guys say 2nd order, are you talking about the order of a modeling ODE or something else?
Click to expand...

Even order harmonics (half, double, etc) would indicate the vibration is directly related to the engine rotating, but sympathetic (something shaking, tapping, droning in a separate part) or geared up or down at double or quadruple, or half (etc) speed. Even frequencies mathematically.
I worked in a few shops way back thad had a reed tachometer, kind of expensive but will show the frequency. If the engine was at 3000 and the shake was 50hz, that is 1:1, or first order. It?s probably a flywheel or balancer on the front of the crank in a car sittind still, or also possibly the driveshaft if in a 1:1 gear while moving. (3000/60sec=50) If it was half that, or 25hz, in a car moving in a 1:2 gear ratio, it is the driveshaft. Half speed could also be a misfire in a 4cyl, but it feels different and gets harsher under load.
You can also get even order vibrations in a broken motor mount or even a bolt or nut jammed in between 2 parts that should be isolated.
Random (unrelated mathematically) vibrations can be an odd gear ratio. Real slow mathematically related vibrations are usually wheel/axle, due to the final drive reduction.
Odd order vibrations that change order with rpm usually fall into the unattached random parts waving around due to rom or road shake or whatever.
Higher freq is usually a lightweight parts (cat shroud), lower freq is usually heavy (long exhaust pipe) when it comes to rando parts.

When picoscopes started getting popular i took some classes and we messed around with transducers. You can do up to 4 channels (i think?), and plug in a speed sensor, crank, pressure, shake, whatever. It?s pretty cool, but i never pulled the trigger on buying one.
https://www.picoauto.com/products/noise-vibration-and-balancing/nvh-overview
Is the link to a vid about it.
 
TheLoganZilla said:
Would you be able to elaborate on this a little bit so I can understand better? When you say testing the frequency, how would I go about that? Are there other symptoms I could see that would indicate misfire? And when you guys say 2nd order, are you talking about the order of a modeling ODE or something else?
Click to expand...

There are phone apps where you can clamp the phone to something somewhat firm on the car and it will tell you the frequency of the most prominent vibration. I used one recently to diagnose a very intermittent rumble on the highway in my truck-- it turned out to be one of the wheels. It takes some math to figure out the frequency of the wheels, engine, driveling rotating. and like stated, it could be a harmonic of something.
 
We have the Pico NVH kit with a magnetic base three axis accelerometer. The sensor gets mounted to the driver seat track.

I've also used a reed mechanical device to determine frequency of a vibration.
 
sbabbs said:
Pinion angle?
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With the entire driveline of the car removed, the buzz is still present at the same rpm, so I?m confident the transmission, driveshaft, and diff are all not the cause, nor are any of the angles between them. I am sure that reinstalling the transmission will make the problem more noticeable, but that?s due to the polyurethane bushing I believe.
 
esmth said:
There are phone apps where you can clamp the phone to something somewhat firm on the car and it will tell you the frequency of the most prominent vibration. I used one recently to diagnose a very intermittent rumble on the highway in my truck-- it turned out to be one of the wheels. It takes some math to figure out the frequency of the wheels, engine, driveling rotating. and like stated, it could be a harmonic of something.
Click to expand...

This sounds very interesting. I?ll have to look into the math and methods behind using frequencies to determine where my vibrations come from. How accurate are the phone apps compared to the expensive pico equipment to anyone?s knowledge, mikep, esmth, ZVOLV?
 
Vibration thread:

http://forums.turbobricks.com/showthread.php?t=352028

I haven't used a phone to diagnose a car. The Pico software is pretty neat. You enter tire size, rear axle ratio, and plug the laptop into the data link connector for a speed input. Connect the accelerometer to the seat frame, go for a drive, and it does all the math for you and spits out a bar graph showing whether the vibrations are Tire, Propshaft, and/or Engine vibration.

Spend some time on Youtube watching NVH videos.
 
esmth said:
There are phone apps where you can clamp the phone to something somewhat firm on the car and it will tell you the frequency of the most prominent vibration. I used one recently to diagnose a very intermittent rumble on the highway in my truck-- it turned out to be one of the wheels. It takes some math to figure out the frequency of the wheels, engine, driveling rotating. and like stated, it could be a harmonic of something.
Click to expand...

I?ll have to look into that, thanks.
 
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