David Floyd

Luke, flywheel was lightened and balanced, shifter does not shake but the rest of the car does.

Has anybody had a new motor mount that turned out to be bad ? I will have to get back under the car and do some measuring on the mounts, but that will be next weekend.

Mike S.

David et als,

Balance shafts cancel the engine vibration harmonic that naturally occurs in our 4 cyl. engine. The harmonic is always present. There is no way to configure a 4 cyl to eliminate this vibrational harmonic. Thus balance shafts were invented. A properly designed V8 naturally eliminates this vibration harmonic. So the balance shafts are not there to "tune out" a vibration at a specific engine rpm.

One more vote for a left motor motor mount!

Good luck,

Mike

MAS

"... So the balance shafts are not there to "tune out" a vibration at a specific engine rpm."


No, but depending on the mass of the engine, certain RPMs will cause more vibration (resonation) than others. All objects will resonate at set frequencies, depending on their mass and the materials they are made of. So balance shafts will have more effect at certain RPMs than others. (This is how tuning forks work)


-MAS

Robby

MAS-
No, but depending on the mass of the engine, certain RPMs will cause more vibration (resonation) than others. All objects will resonate at set frequencies...balance shafts will have more effect at certain RPMs than others...
**************************************************

True, and what really seems odd, is the "turning left" thing. I don't have much experience w/this stuff, but it sounds like it could be a motor mount prob to me- maybe a flyhweel, but it seems that if turning a certain direction settles it out, then there would be some type of friction OR weight OR rotational change that helps to balance it out. That just doesn't sound like the balance shaft to me, but again, I don't know too much about that stuff...

*************************************************
MAS-
I think that Ferrari had this problem with the old 3 litre four cylinder engines they used...
**************************************************

I didn't know that ANYONE used a 3.0L 4cyl besides Porsche. I've even read that they were the largest engines ever produced. As a matter of fuct, I thought even the 2.7L's that the 944NA had for a year or so, were larger than any OTHER 4cyl made, and the 2.5L was next, but I HAVE seen some other's round to 2.5L, as well as some pick-em-up trucks and there are several 2.4L's, but I thought the 3.0L 4's were in a class by their own. Were Ferrari's 3.0L 4's in production cars, or maybe race cars, etc? Which cars were they used in? Just curious... Also, was there ever a larger 4cyl engine than a 3.0L? Anyone?

cruise98

David:

Are you using the factory distributor rotor?

The factory unit is supposedly balanced as an assembly, whereas the aftermarket replacement parts are just the one plastic piece.Just a thought.

The turning left thing is very weird. Are the engine mounts tight? Both the cast pieces bolted to the block and the rubber mounts?

David Floyd

After more driving today in the problem RPM range, I am now thinking it could be a left wheel bearing causing the vibs, even tho they have less than 1500 miles on them, freshly repacked and have been double checked for correct torque (screwdriver and just move the washer trick )

I will pull the wheel assembly apart Tue night and see if something is wrong there.

MAS

The large Ferrari fours were racing cars. I'm not sure of the exact dates, but I think from the '30s.

-MAS

billybones

Look left? look right? look forward and back? THat is classic blown clutch RPM's.. Maybe torque tube is loose? front or back? Loose clutch bolts? I would look at the drive train.. something forgotten? or not aligned right.. One last thought. the driveshaft conector is loose?... sounds like some one forgot something. RPM's dictate that thought. HTH.. good luck!

David Floyd

Ok vibration cause found, the new 3" exhaust is hitting the left side rear a-arm mount. After an hour on my back with a chisel and hammer I was able to make about 1/4" clearance between the two, went for a test run and much much better but still there, so I just need to make the gap larger, guess I need to remove the exhaust and flatten that area of pipe.

Happy to find the problem and to be a lot easier fix than it could have been but still a pain in the butt.

Luke

I beleive it was Dave Finch that designed the S2 motor? and he said something along the lines that without the balance shafts the micro vibrations will break the oil pickup and destroy refrence sensor. Even if you cn't feel them, it's a harmonic thing, I would assume.

SO I guess, as long as you run dry sump and have a DFI you'll all set

Ski

David,,you have SFR exhaust right? Man I wish I had remembered mine hitting my sway bar a year or so ago. I remember too that after I posted it on the list, Tim came back and said that his jig had gotten bumped or someone knocked it over. He offered complete new systems or to repair the old one for free. I had already used a 5# shop hammer on the spot. Wow,,that is really interesting..

Glad you found a simple solution.

TurboTim

Ski,


The jig was fixed;^)


David,

Stop! Do not wack the exhaust with a hammer! You have to index the testpipe properly since it is in two pieces. Basically if you rotate the back half of the testpipe with it attached to the cat-back it will allow the bend on the cat-back to clear the trailing arm much better then the way it is now. It is an easy adjustment without having to pull out the hammer. All you have to do is loosen the clamp on the testpipe and the muffler.

David Floyd

Tim,

The front section that connects to the down pipe is the problem, as I see it there is no adjustment in that piece.

I will give you a call

Ski

Tim,

I know you got it fixed and I was just laying good faith on your great customer service. BTW, at the dyno the other day many, many people commmented on how the car sounded. They really commented on full throttle. Sounds Great! One guy stated it was a cross between a Porsche on steroids and a Ferrari at full throttle.

David Floyd

Tim's customer support has been great, he called me this morning before I could call him and with his cell phone I have been able to reach him after hours on several occasions with questions during my install and debugging stages.

Thanks Tim


<img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />