How many degress out is a problem?

heady2010 · Post by **heady2010** » Thu May 28, 2020 8:19 pm

Hi all,

When comapring cam and crank signals to a known good, how many degress of difference is cause for concern?

I have found that comparing known good vehicles that are brand new to ones that have covered more miles (but with no problem) to be slightly different, i assume due to belt/chain/component ageing/wear. But where does it become an issue?

Thanks

Technician · Post by **Technician** » Thu May 28, 2020 8:25 pm

I suppose one might think it becomes an issue when an engine running fault occurs and maybe backed up with a fault code such as P0016 say!

heady2010 · Post by **heady2010** » Thu May 28, 2020 8:31 pm

Most of the vehicles that come my way have been "fixed" by the recovery company so no codes unfortunately.

liviu2004 · Post by **liviu2004** » Thu May 28, 2020 8:36 pm

It is the car maker which decides. I don’t see the point for anyone to start digging 50 car makers with hundreds of engine types and to post here all variables. Waste of time.
But if you have a specific car make and model and engine type in mind, go for it. Which one?

heady2010 · Post by **heady2010** » Thu May 28, 2020 9:24 pm

I am at a main dealer, can't say which due to "politics".

Maybe more so what I should be asking for is examples of where people have had problems with cam and crank being out of sync, and how many degress were they out. I am just trying to build an understanding of when to invetsigate.

Post by **Steve Smith** » Fri May 29, 2020 8:45 am

Hello and thank you for the posts.

How much deviation is too much deviation is a great question, thank you

Most certainly this is manufacturer specific & dependent upon engine type, camshaft drive arrangement and the demands placed upon Engineers to meet emission criteria

I think we accept that an ageing petrol or diesel engine without VVT will have a greater tolerance level to cam and crank deviation than a modern day multi- cam engine with VVT on all camshafts.

The following case study looks at one such Quad Cam engine where 3 degrees of camshaft deviation was sufficient to generate fault code P0016

Where camshaft deviation momentarily exceeds a specified value, (under rare and extreme operating conditions) the Vehicle Manufacturer may issue revised software in order to increase the parameters of deviation before a fault code is generated (Increase tolerance level)

When it comes to capturing cam & crank devation using PicoScope the following forum posts will help
here and here

Be aware that camshaft and crankshaft correlation may well be fine at idle speed, but also measure the same deviation during acceleration and deceleration too (VVT Disabled)

I hope this helps, take care......Steve

heady2010 · Post by **heady2010** » Sat May 30, 2020 6:22 pm

Thank you Steve!

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