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Sigma (310R) high rpm vibration


DonDP

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Hello,

I have a vibration at high RPM over 7k which is definitely engine related. You can’t really notice it until flat out in 4th gear. I assume it’s because it spends more time getting to the shift point that makes it more noticeable.

It is however, always there, you can simulate in 3rd holding it at high rpm and equally there is some vibration in neutral both with clutch engaged and when released.

I am trying to work out if this is just a trait of sigma engine, possibly the 310 with the different cams?

Does anyone else have this? Is this a case of TADTS?

 

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So I made some noise this morning....

first of all I noticed that the crank shaft pulley is not quite straight - not sure if this is normal? I took a slow motion video here:

Once it was nice and warm I revved the engine right up to 7k-ish in the garage. There is more vibration coming from the front of the engine than the back (relative ro car). Again not sure if the amount is normal or not since all the belts and ancillaries are at the front?

 

 

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The vibration is through the chassis, but can obviously be felt through the gear lever too. I have checked all engine mounts and and gearbox mounts.

Clearance between the gearbox and chassis is very tight, roughly 0.5mm at its closest (lower left longitudinal). I removed the rivets under the gearbox mount (for the floor) as these seemed unnecessary considering the mount bolts over them. This has given a marginal improvement in clearance. Still need to test. 

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  • 11 months later...

I suspect its TADTS as mine does as well. Could be the way the engine is mounted, road cars tend to have a third top link         I don`t go to max rpm. the power curve drops quite rapidly above 7k `Short shifting` at 6800 gets you there quicker. Stress goes up as the square of rpm.,  6800 to 7500 is about 23% more stress. The engine may have the Ford flywheel and be balanced to production tolerances which don`t anticipate 7500rpm  And then there`s.........!!! 

Let us know what you find, if anything

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