WBX "improved" cams in the pipeline

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CJH
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Re: WBX

Post by CJH »

OK, I see the point you're making, but an oil cooler and the associated pipework will drop some pressure. I have no idea whether it's a significant amount of pressure in the scheme of things though. So, next question about the oil path. Where in the path is the pressure relief valve - before or after the filter? If it's after, then it's also after the cooler, so if the pressure is still too high after returning from the cooler, won't the pressure relief valve dump the excess? So the net effect of the high volume pump would be to move more oil round the cooler, without exceeding the relief valve pressure at the bearings?

silverbullet wrote: (This is also why you never re-use a cooler after a blow up or fit a used one: they handle unfiltered oil and are impossible to clean out. Fact.)

Isn't the first place this unfiltered oil goes to, the filter?
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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

The length of hoses wont have an appreciable effect on pressure or flow rate unless desperately undersize.
The pump delivery ia governed by the pressure releif valve first and foremost.
If you have a sandwich plate then the oil goes out to the cooler then returns to be filtered. The filter is always the last thing before the oil enters the gallery.

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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

Back to camshafts.

I have been thinking on the possible benefits of gun-drilling the shafts and taking an oil feed from the centre cam bearing, to allow a small (1.5mm or so) oil drilling to be made on the heel of each cam.

My thinking is that despite the cam's proximity to the sump oil, the lobes and lifter faces may not necessarily be adequately cooled by oil, which would contribute to lobe wear.

The VW flat four cam does work hard for a living because each lobe has to open two valves in rapid succession. I can see how the cam ramps could be wiped almost dry by the first lifter and then have no chance for the surface to pick up any oil or cool off before meeting the second one.

The cam is quite large, near enough OHC sized so surface speeds must be quite high compared to some other engine designs I can recall.

A spinning cam only wants to throw oil off the lobes after all...

On the other hand I could be wrong. The lifter gallery effectively channels all the draining oil down towards the camshaft, but I have no idea of the windage effects inside the wbx, which could just as well hold oil around the crankshaft and restrict drain-down.

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Re: WBX

Post by tencentlife »

I don't know whether that kind of work would be worth it. They are a hard-working cam but are also very heavily spray-lubricated by the rod and main bearings, they receive much more oil than a typical OHC setup does. Granted, the oil coming out of the bearings is pretty hot, but as long as it's within the working temp envelope of the lubricant that in itself isn't a problem. In decently-maintained engines, they do go amazingly long miles with surprisingly low wear.

I have noted, as you have, that the lubrication is uneven side-to-side, as the lobes rotate toward the 3-4 side they are bathed by the rod splash, the 3-4 side lifters wipe the oil away and then they go around the underside where they aren't exposed to the same heavy spray. If that were a problem, though, we would see more lifter wear on the 1-2 side, and in my experience such unevenness has never been apparent.

Surface speed is one issue, but I think it is outweighed by the fact that for a given amount of lobe height, starting with a larger base circle decreases the spot pressure on the sliding faces as well as the side-pressure on the lifters. Due to the effects of valvetrain inertia, the peak pressure location on cam lobes varies with rpm; at low rpm, peak pressure is over the nose, but as rpms increase the peak pressure moves farther and farther down the flank of the lobe. Where pitting begins on cam lobes shows this, it's always a bit down from the lobe peak, which is where peak pressure would fall at moderate rpms and the wear there reflects that the engines spend most of their running hours in that band.

So, interesting idea, similar things have occurred to me as well. I kind of think just taking care that there is good steady oil flow and not at extreme temperature does the job as it is.

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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

Thanks Chris, I value your opinions. Once again, it all boils (!) down to controlling oil temperatures and so maintaining oil film strength.
I shall put the 15xD drills back in the toolbox drawer for another day.

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Re: WBX

Post by matteochiochetta »

Hi everyone,

I'm a newbie in rebulding engines and not a tuning-lover but I came across this thread and would like to know if this improved camshaft is a sort of plug and play thing and it's safe to use it even for me who don't want to open up the engine again in the next few years. Do I need to do nothing but swap the camshaft? I red about the oil pump and I understood that the stock 26mm oil pump should do the work fine. Is there any camshaft ready to be shipped from silverbullet's workshop?

Any advice for me and the mechanic who is going to do the work with me?

Many thanks everyone!
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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

No such thing as plug n play, fuelling and ignition will require some adjustment.
All aftermarket cams dictate use if the pre-1970 type 4 cam as previously discussed.
Nothing ready to ship, very much a R&D project at the moment.

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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

Testing, testing...
Image
...very testing :x

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Re: WBX

Post by matteochiochetta »

silverbullet wrote:No such thing as plug n play, fuelling and ignition will require some adjustment.
All aftermarket cams dictate use if the pre-1970 type 4 cam as previously discussed.
Nothing ready to ship, very much a R&D project at the moment.

Thanks... I think I'll get a standard cam shaft from VW Heritage...
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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

I went round the M25 today to visit the cam manufacturers; there had been a bit of a mis-communication and assumptions had been made on both sides, resulting in the cams being not quite as expected...

Anyway, it was four hours well spent. They used their computerized cam profile measuring machine to check my NOS DJ cam so that we had that as a known baseline from which to work and make comparisons.
Then one of the new cams was measured, followed by my very worn Oettinger 2500 cam.

The results were interesting, to say the least, but the upshot is that we have decided on a fresh set of timing and lift figures that will improve the breathing of any 2.1 or larger wbx without wrecking its idle quality or emissions, but will give performance a boost especially if you have been driving around for years on a worn out camshaft!

Hard data for tech fiends to follow shortly...

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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

Here is how the durations stacked up, as measured at 1mm lift:

DJ (average values, some variation)
Inlet 232, Exhaust 224, lobe seperation 112 (111.7)

Cam lift: Inlet 8.5mm, exhaust 8.1
Lift @ TDC: in 1.3, ex 1.0

Oettinger: too badly worn to accurately profile, but suggested a 110 lobe sep and 8.5 inlet and exhaust lift.

Holman profile:
Inlet & exhaust both 234, 110 lobe sep.

8.5 in and ex cam lift, both 1.65mm @ TDC.

The lift at TDC is the most telling thing. The new cams will be opening & closing faster, being open for slightly longer overall and having just a little more overlap to help the incoming charge to purge the exhaust gases.
It is a series of subtle changes that add up to a sensible modern cam for an efi flat 4, but isnt just a lazy copy of come old Aircooled profile meant for a 69mm crank and carbs.

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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

PS particular attention has been paid to ensuring that the profile is within the working envelope of the wbx 24mm diameter cam follower, to avoid any chance of the corner of the tappet digging into the flank of the cam, which is essential for a long service life ;)

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Re: WBX

Post by toomanytoys »

Would have been interesting if an alternative cam could have been checked at the same time.. I have a brand new one on the shelf that could have been put into the pot... :wink: :wink:

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Re: WBX

Post by ozzi_in_the_uk »

Top work silverbullet! :ok

I too have contemplated all the usual conversion routes But deep down (being old school mecahnic from OZ), I (like probably most of us on this forum) have often contemplated 'What would she? ..Just what would she be like?, ..with a warm cam, some simple tract work, tuned length extraction and fully closed loop Engine mangement system??
Probably just as expensive to do, ..and probably not as powerful, economical, and heaven forbid mabye not even as bullet proof?
But boy it would'nt half put mahoooosive grin across my face with a nicely stroked, big bore Megasquirted WBX ...burbling away under the back hatch. Just like nature intendid :D

I aplore your courage and committement to this great cause Silverbullet, as it is probably not everybody's cup of tea. Especially when there maybe(?) more popular options out there. But I for one will be more than willing to spend my hard earned cash on a modern purpose ground 'bumpstick', stroker crank, O/S 'slugs N jugs' and asscoiated head and 'case' work etc, over an alternative. Cos I think (just like you) there is still plenty of fight in the ol' boxer yet! And it is a great shame that there appears to have been very little interest in trying to optimise the 'old girl' (apart from tencentlife), like the old Aircooled little sister has been over the last 50 odd years.

So keep up the great work, and I am wishing all the best of luck and truly hope you realise the dream you are chasing (as I 'm sure you will), and you get the chance to reap all the rewards that it deserves. Because I for one am busy saving my pennies.

Note: Plus my missus will never clock a 'big block' WBX slowly morphing into life, deep within my garage ...like she would a scooby conversion!!
:rollin


And it'll be twice as much fun ta-boot!!! 8)
1988 - 2.1i wbx - Microbus SA Import

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Re: WBX "improved" cams in the pipeline

Post by silverbullet »

Thanks Ozzi! Compliments like that are what keep me going and convinced that I am on the right track!
If my SA has taught me one thing it is that any loaded bus needs at least 130bhp/200Nm of petrol power to cope in modern traffic.
Add MS to a well built 2.5 wbx and you should see more like 150 very reliable bhp that wont have you stopping at every tankstelle.

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