WBXmayo

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Re: WBXmayo

Postby CJH » 11 Jan 2018, 22:03

Cam profiles are usually plotted against crank angle, and the cam turns twice for each crank rotation*, so you might want to divide* your measurements by two. I don't know that the pip on the cam gear is necessarily zero - timing is usually referred to TDC - I hadn't thought to check whether the pip on the ring gear is at TDC, but I don't think it has to be - it's just for aligning it with the crank gear. So your measurements may not have the correct zero, but you should still be able to see where the crossover is - this will be close to TDC if you're measuring the cylinder 1 lobes.

For both of the above reasons (cam=2xcrank*, TDC is marked on crank pulley) it makes sense to measure with the cam in the case, and put your measuring scale on the flywheel. I found a protractor image on the web (saved it here) and then printed it to fit the flywheel - the bigger the better, to improve your precision.

Image

It doesn't matter about the precise orientation of the protractor image - just stick it on then record an angle when the pulley is at TDC and subtract this reading from all your measurements. I simply taped a piece of flat plastic to the case to give me a reading point - it doesn't matter where this is as long as you record the reading when you're at TDC.

To make the measurements I dropped a tappet into the case, and another one inverted on top to give a flat surface (don't use an old dished tappet) for the dti gauge to rest on. The pushrod protector bolt holes make a good place to screw the dti gauge shaft into.

The measurements you record will need to be offset by the reading you get at TDC, then you'll need to add/subtract 360 each time your readings go past 0 - easily done in a spreadsheet.

Good luck!

*E D I T - I got that wrong - the crank turns twice for every turn of the cam, so you'll need to multiply your cam angles by two to get crank angles. cam=0.5xcrank
Last edited by CJH on 12 Jan 2018, 07:32, edited 1 time in total.
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Re: WBXmayo

Postby itchyfeet » 12 Jan 2018, 06:21

Thanks CJH, I have 360 degrees twice on the cam scale it is probably the TDC out, I will plot a graph later then compare to the new cam.
I only have to work out the offset from TDC to the cam gear mark once then I can use the jig which I can do in the warm :D
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Re: WBXmayo

Postby CJH » 12 Jan 2018, 07:46

itchyfeet wrote:Thanks CJH, I have 360 degrees twice on the cam scale it is probably the TDC out, I will plot a graph later then compare to the new cam.


Ah, ok, so your scale is already showing 2x cam angle (=crank angle). I see that now - your major divisions are 20 degrees.

itchyfeet wrote:I only have to work out the offset from TDC to the cam gear mark once then I can use the jig which I can do in the warm :D


If I recall correctly, this cam has been cut to match the lobe orientation of the original cam, so in theory your vernier adapter will only need to be mounted at zero. But obviously it's important to get the crossover point where you want it, so checking the offset of the pip from TDC is a measurement you need to get right. On my worn DJ cam I think I found the crossover point to be 4-5 degrees BTDC.
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Re: WBXmayo

Postby silverbullet » 12 Jan 2018, 09:55

I bought one of these. Its thick steel and accurate. Just bolt it to the nose of the crankshaft with a centering collar.
https://m.ebay.com/itm/66791-PROFORM-9- ... mwBanner=1

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Re: WBXmayo

Postby itchyfeet » 12 Jan 2018, 11:01

So the cam gear dot is clearly not TDC thats why I was confused, I took a guess and rearranged the data and now it looks like Chris's graph
I will check the TDC to cam zero angle but for now I'm just comparing the two cams.


ImageWBX Mayo old cam by Paul_Barr, on Flickr
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Re: WBXmayo

Postby CJH » 12 Jan 2018, 12:06

Interesting - given that this is potentially a worn cam it may not be showing the same profile as a fresh OEM cam, but I would have thought it might be quite similar to the worn cam that I measured. Whilst the peak lift looks similar, the shape of the lobes looks different - mine look more rounded, yours look more 'pointy'. Is there possibly an issue with the rounded tip of your dti gauge? When it's perpendicular to the lobe (e.g. on the base circle or the tip of the lobe) it'll be using the very tip, but when it's riding up the side of the lobe it may be using a different contact point on the gauge tip. I think the gauge will register less lift unless perpendicular, which could account for the 'pointy' shape - not sure if the difference would be enough to explain it fully though.

Your new cam is one that Newman have produced from your fresh OEM cam - is that correct? So it would be interesting to see plots of both of those as well, firstly to see whether the lobe shape is more like your worn one or my worn one, and secondly to see how accurately Newman have reproduced your fresh OEM cam.
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Re: WBXmayo

Postby itchyfeet » 12 Jan 2018, 12:27

yes measuring method is different so plots may well be different, I'm mainly comparing the timing between old and new cams, yours was measured with tappets which are wide and so may touch in a diffetent place as the cam lifts.

Newman cam will be checked next, they have the profile on file, I didn't supply a fresh cam.


CJH wrote:Interesting - given that this is potentially a worn cam it may not be showing the same profile as a fresh OEM cam, but I would have thought it might be quite similar to the worn cam that I measured. Whilst the peak lift looks similar, the shape of the lobes looks different - mine look more rounded, yours look more 'pointy'. Is there possibly an issue with the rounded tip of your dti gauge? When it's perpendicular to the lobe (e.g. on the base circle or the tip of the lobe) it'll be using the very tip, but when it's riding up the side of the lobe it may be using a different contact point on the gauge tip. I think the gauge will register less lift unless perpendicular, which could account for the 'pointy' shape - not sure if the difference would be enough to explain it fully though.

Your new cam is one that Newman have produced from your fresh OEM cam - is that correct? So it would be interesting to see plots of both of those as well, firstly to see whether the lobe shape is more like your worn one or my worn one, and secondly to see how accurately Newman have reproduced your fresh OEM cam.
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Re: WBXmayo

Postby itchyfeet » 12 Jan 2018, 16:39

Just popped the old cam and crank in the case and brought it to TDC No1

ImageP1090167 by Paul_Barr, on Flickr

placed a mark on the cam gear at case split

ImageP1090168 by Paul_Barr, on Flickr

back in the warm and with a scale attached it's clear the cam gear mark is -270 degrees from TDC No 1 as I had assumed in my graph above, it had to be a round number and somebody will figure out why, it's not going to be a random point.

ImageP1090169 by Paul_Barr, on Flickr
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Re: WBXmayo

Postby itchyfeet » 12 Jan 2018, 18:11

Cam adapter on next

ImageP1090172 by Paul_Barr, on Flickr
ImageP1090173 by Paul_Barr, on Flickr

then Newman cam on, had to rumage in the tool box for those imperial allen keys :roll:

ImageP1090175 by Paul_Barr, on Flickr

scale on

ImageP1090177 by Paul_Barr, on Flickr

in the jig for measuring

ImageP1090176 by Paul_Barr, on Flickr

and the results... mmmm the intention was to get the timing right with regard to the reference hole, if I was using a stock Aircooled ( unadjustable) cam gear the timing would be around 30 degrees out.
I suppose anybody fitting a non stock cam should check timing.
It's possible they just can't cut it due to the position of the raw cam lobes on the blank, they said there was some lee way on this but maybe not that much, I will ask.

ImageNewman cam timing by Paul_Barr, on Flickr

Imagemayo cam timing by Paul_Barr, on Flickr
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Re: WBXmayo

Postby itchyfeet » 13 Jan 2018, 10:53

Adjustment on the adapter does not go that far so I'm going to have to make a new mark and then use the fine adjustment if needed

50 teeth/gaps around the gear and two crank turns per 50 teeth means each tooth is 720/50 =14.4 degrees so two teeth/gaps is about right for my new mark ( which I will drill when I'm happy)

ImageP1090178 by Paul_Barr, on Flickr

quick check shows it's now the same as the old cam, peak for No1 inlet on old cam was about 110 degrees on graph above.

ImageP1090182 by Paul_Barr, on Flickr


I'm going to make a pointer to be more accurate and check cams for cylinder 1&3 and 2&4 again
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Re: WBXmayo

Postby CJH » 13 Jan 2018, 12:39

I think you're right, that the blanks don't have enough latitude to allow Newman to get the lobes aligned exactly as per the original, which means a vernier adapter is always going to be needed. Mine needed about 20 degrees of advance, so it's odd that yours needs more, given that I believe you specifically asked them to match the original - despite that request it's come out further away.

I achieved 20.4 degrees by going for one tooth and 6 degrees on the adapter. This photo shows 4 degrees on the adapter, but I think I took that before deciding to put the crossover a couple of degrees ahead of TDC, to be more like the OEM cam. I'm not sure how critical that is though.

Image
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Re: WBXmayo

Postby 937carrera » 14 Jan 2018, 11:07

itchyfeet wrote:50 teeth/gaps around the gear and two crank turns per 50 teeth means each tooth is 720/50 =14.4 degrees so two teeth/gaps is about right for my new mark ( which I will drill when I'm happy)


Fascinating reading. :) lots of great work going on.

I was wondering have you thought about introducing an "offset adjustment" to the Newman crank data and overlaying the two profiles on the same graph. I think you would be able to see / confirm what the target adjustment should be, validate that the max valve lift points are aligned and also that the ramp profile for the raising of the valves are aligned. Just an idea.
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Re: WBXmayo

Postby itchyfeet » 14 Jan 2018, 14:28

937carrera wrote:
I was wondering have you thought about introducing an "offset adjustment" to the Newman crank data and overlaying the two profiles on the same graph. I think you would be able to see / confirm what the target adjustment should be, validate that the max valve lift points are aligned and also that the ramp profile for the raising of the valves are aligned. Just an idea.


Yep that was the plan but my version of excel is old and graphs are easier in the later versions so I'm going to do it in my break at work this week.
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Re: WBXmayo

Postby itchyfeet » 14 Jan 2018, 18:04

I have added a pointer for more accuracy and rechecked both old and Newman cams, measured all lobes, (that's about 250 measurements), graphs tomorrow, then I'm going to do a brand new DG cam just for reference.

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Re: WBXmayo

Postby itchyfeet » 15 Jan 2018, 13:43

2 teeth isn't right, looks like my 1st measurement of the DJ cam and this measurement are different but I can't see why.

ImageDJ vs Newman 2 teeth adjust by Paul_Barr, on Flickr
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