Judder and loss of power in hard left hand turns

[Gus-350z]

Hi All, quick question below and open to ideas as to what the cause could be.

 

Problem:

 

• Under hard left hand turns (e.g. either turning off an A road into a side road, braking and then getting hard on the throttle. Or, on left hand hairpins on track) my 350z will judder and it feels as though power is being cut.
• Vibrations come through quite strongly through the transmission, but not the steering or brakes.
• It kicks in just before the car might reach the point of under or oversteer, but not quite.
• It also happens regardless of whether EPS is turned on or turned off. With EPS turned on, I can also notice the effect of it killing the power (in addition to the strange effect above).
• With EPS off, it doesn't trigger the light to come on the dash which normally signifies that EPS is kicking in.
• The effect definitely comes from the rear wheels, and much more noticeably in left hand turns rather than right hand turns.

 

My instinct is that it's diff, drive shaft, or ABS related - but I'm open to ideas and suggestions if anyone has had this happen before!

 

Cheers

 

[ZMANALEX]

Just back off the throttle a bit as you are unsettling the car.

 

You can still carry good speed in and out of the corners when driven aggressively but sensibly and smoothly.

 

Or if you want to get techy just turn the stuff off that affects this.

 

Switching off the EPS is not the answer as it does not completely switch off 100%, but is usually enough for most people.

[Gus-350z]

12 minutes ago, ZMANALEX said:

Just back off the throttle a bit as you are unsettling the car.

 

You can still carry good speed in and out of the corners when driven aggressively but sensibly and smoothly.

 

Or if you want to get techy just turn the stuff off that affects this.

 

Switching off the EPS is not the answer as it does not completely switch off 100%, but is usually enough for most people.

Thanks for the reply Alex! Although, I would say that the juddering starts to kick in even before I push the car too hard/apply too much throttle too early. My reference for this is that on right hand turns, the car comes out of the corners fine with a similar throttle application.

One idea that just occurred to me is that I have a new MPS4 on the driver side and a relatively older one on the passenger side. Could the difference in grip between these two perhaps be confusing the system?

If I wanted to "turn off the stuff that affects this" how would I go about this? Whether to get techy, or just to test whether or not it is EPS related, this will be useful.
 

 

Thank you again

[ZMANALEX]

I would be looking at the tyre set up.

Try swooping them around and see if the fault follows

[Gus-350z]

1 hour ago, ZMANALEX said:

I would be looking at the tyre set up.

Try swooping them around and see if the fault follows

Good idea - thank you. I suspect you're right wrt the tyre set up. I shamefully have quite a mix of tyres on the 4 corners and I suspect the track exposes this.

 

Out of curiosity, I have attached a drawing of the tyres (all MPSS apart from new one which is PS5) and a score out of /10 for condition (based on tread & sidewall condition). From a tyre/dynamics perspective, how could this explain the juddering on hard lefts?

 

[ShortPaul]

I would start with replacing the tyre's then a four wheel alignment, certainly wouldn't have mix match of tyre's buddy 

[ZMANALEX]

Tyres first and then the techy options:

 

 

 

 

 

 

[Gus-350z]

Quick update on this. I now have new PS5's on all 4 corners and have had the alignment done, but the juddering problem remains (albeit much improved compared to before).

 

Now, on hard right hand turns, it is almost impossible to break traction without driving like a muppet on the roads - the PS5's are amazing tyres. However, on hard left hand turns, although far less than before, I still get a sense of breaking traction/juddering through the rear end and transmission.

 

The same sensation occurs when the rear left wheel (or both rear wheels) go over bad pot holes for example.

 

Next steps, my plan is to use CS2000's kit to disable the vdc - to see if it is the system getting upset with stability on the rear left hand wheel (might indicate some sort of sensor issue perhaps?)

 

More than happy to hear any thoughts/advice on what to look at next.

 

Gus