Camshaft Data

You could do it on the back side of the cam where the lock goes?

Wong data!!!!

EDIT 12March2012 - I found an error in my model - I did not account for valve protrusion from the cylinder head so the piston to valve clearances are a LOT less than they were before. The data and charts in Post 1 have been corrected and are accurate to the best of my knowledge with an OEM ALH cam, 0.040" valve protrusion from the cylinder head, 0.020" piston/head clearance, 0.040" piston valve reliefs (all ~ nominal OEM ALH numbers) at TDC.

Red Bold numbers have been edited

My profound apologies for this mistake - I hope no damage has been done as a result.

PD gear works fine for this, just needs some shaving at the back to clear the plastic casing, would be good to add a degree scale somewhere for quick changes..



About piston to valve collision, its seems that even when it happens, the engine does not really care about it, I found this when I pressurized the cylinders to prevent the valve from dropping in while changing the stem seals, most of the valves where leaking slightly, altough the engine started perfect (17:1 CR) and day before it dynoed 255hp smokefree.

That's pretty amazing with the exhaust valve making indentations in the top of the piston...Do you know how many miles the engine ran like that? The theory I've heard is that the valve stem buckles and then fatigues and breaks the head of the valve off and it's all downhill after that.

I think adjusting the cam might be a bit easier with a graduated cam pulley - I'll have to see if I can find one.

Thanks for the info

I think it must about 5000 miles like this, then I just pulled the pistons andmake the pcokets deeper, valves where all straight and are still in now.. so I don't thin they really cared about it too much

wow what's happend Rub? why you pulled of the head.
that exhaustvalve have made a nice cr drop@

Forgot to deepen the pockets

I only made them bigger the first time, not deeper, as you can still see on the intake valve pocket where it has been made bigger

All 4 pistons look the same?

nope, middle ones looked worse

oke but you run with dbilas 260 cam 9,9mm lift ?

nope, when this happened was stock cam, I was going to change the stem seals to be able to run 10mm lift, as the stock ones where too tall

oke is this because of the larger valves uses with different valve height.
so the hydro stoters pushes the valves already more than stock lift..

valve height was actually equal, problem was I used BHW pistons which have less deep pocket than ASV

so that's the problem.. Im using the ASV pistons with dbilas 250 9,5mm lift then I no need to be worry of valve contact.

I had some more time to play with cam timing this weekend. I took my $30 Harbor Freight compression gauge kit, removed the hose and gauge and put a 1000 psi pressure sensor on it. This reduces the additional volume that gets added to the combustion chamber by a LOT. I used the same data acquisition system that I used for taking intake and exhaust pressure measurements, put a 1000 psi sensor on it, cranked the sample rate up to 1kHz and took cranking compression data with this instead of the typical dial gauge. The advantages of this are that you can save data, review it later, evaluate rise rates, first stroke compression, leak down, etc.

I've been curious about the effect of cam timing on performance in TDI's. Part of the reason for measuring an ALH cam profile and calculating valve to piston clearances is to know how far the cam can be advanced/retarted before valve to piston contact.

In my recently rebuilt engine, I measured piston valve relief depth, piston protrusion from the block and valve protrusion from the cylinder head. This paired with the cam profile and a very accurate TDC mark, gives me the ability to pretty accurately know how far I can go before getting into trouble.

Generally speaking, advancing the cam should bring the powerband down in the RPM band. Focusing in on this detail a bit more, I theorized that advancing the cam should raise the cranking compression. With the intake valve not closing until 50+ crank degrees after the start of the compression stroke, there is likely quite a bit of reversion at cranking speeds and advancing the cam should show up with higher cranking compression.

I tested 0.00, 2.66, 5.33, 8.00, 10.66 degrees advance (this corresponds to 1, 2, 3 & 4 flywheel teeth). Below are the results of this testing.



The 10.66 degree advance (4 teeth) is a bit of an anomoly (in the opposite direction of the theory) during the first few cycles, but catches up and ends up highest at the later cycles.

The rest of the conditions are more/less the same and didn't show any significant difference in cranking compression.

Once done with this experiment, I set the advance at 8 degrees (3 teeth) and drove it. I'll leave it at this setting for a while, but in the ~250 miles I've driven it this way, it has noticably quicker response/spool up and feels a bit "snappier" in the lower RPM range (1500-2500 RPM). The cruise control does not seem to work as hard (undershoot/overshoot) with this timing. EGT's are higher - probably 100F or so. Maybe a bit less smoke as well.

I went back and repeated 0 and 3 teeth settings and the test did not repeat well for some reason.



The significant drop in pressure between cycles makes me think there is some delay in the check valve closing on the glow plug adapter. This could also be causing the difference in readings as it seems to have some delay in opening as well with the spikes on the 2nd and 3rd, etc cycles.

So, this may all be somewhat garbage data. If I do this again, I think I'll take the check valve out of the adapter and just get cylinder pressure up/down each cycle. With the reduced volume with the pressure sensor it will be relatively close to actual cylinder pressure and might do a better job of identifying differences of cam timing.

I'm not sure if this has any value at this point or not. Ideas, comments, suggestions, etc are welcomed.

Thanks for reading

crank encoder would be nice =)

Yes it would, but unfortunately I don't have one.

A couple things I didn't include in the above post

The Y axis is in PSI, the X axis is in seconds and the cranking RPM is 144 (edit cranking rpm is 288 because there are TWO crank revolutions between compression pulses)

isn't that a bit slow?

FUB, what DAQ are you using ?? I need a new one... any recommendations ?

DPM - are you referring to cranking RPM?

CharlieT - Send me a PM with what you're using now and what you're trying to do and I'll see if I can recommend something.

yup. isn't it meant to be 200-250?

were the other GPs removed?

Ahhh - silly me - there are two crank rotations between pressure pulses, not one

Cranking speed was ~288 RPM

All other glow plugs were removed and there was a battery charger on the battery.

So, since the above cranking compression test was more/less useless - I repeated it a couple months ago. Same conditions more/less - Battery charger on the battery all the time, glow plugs removed, injector lines removed, warm engine, etc. I've finally taken the time to compile the data. Each run was started from #1 cylinder TDC.

I used the same 1000 psi pressure sensor installed in a Harbor Freight adapter as before, but this time with the check valve removed. I was also able to get a very accurate crank speed measurement with a sensor on the flywheel. The DAQ was configured to know how many teeth were on the flywheel and plotted RPM directly. Below is a screen shot of the live data - Pressure on the bottom in green, RPM on the top in light blue.



Peak pressures and minimum RPM's were picked from the above data and entered into the below table for each cam and it's cam to crank timing. I'm able to run these timings because I know all the dimensions on my engine. See first post in this thread for more details on this and what you can/can't get away with in your particular engine without piston/valve contact.


The above data was plotted for an easier visual interpretation.


The ALH cam at 8 degrees advanced was repeated at the end of the testing with that cam (runs 1 & 4) and they repeated reasonably well as can be seen on the top two curves.

Here is what I was able to summarize from the above data...

1) The more advanced the cam, the higher the cranking compression pressures
2) The more retarded the cam, the lower the cranking compression pressures
3) Even advancing a the Colt Stage 2 cam by 6.6 degrees, it still can't match the cranking compression of the stock ALH cam that has been retarded by 8 degrees
3a) This might be due to differences in the ramps below the 1mm lift that duration is specified at

Anyone have any other observations from the above data?

I guess it just depends on amount of crank angle after BDC that the intake valve closes

Bumping an ancient thread, drove mine 70 miles with the cam retarded by 5 starter ring gear teeth, so that's 13.3 degrees. Had it up to redline a few times, too. Oops. Lesson learned, don't align the cam to the head by eye, it isn't good enough even lining up a couple machinist's parallels.

Valves are sunken to around .020" protrusion, though, so I've got around the same of extra clearance (forgot to measure the valves' protrusion before cutting the seats, think it's around .040"), along with .004" or so of extra clearance in the head gasket thickness. ARL pistons, ALH motor, .039" of piston protrusion, two hole gasket.

All fixed up and it starts like normal. pulls pretty well for not being broken in yet.

Couldn't get the fiber optic camera on a stick thing at work to see the piston through the GP hole (might pull an injector next time I'm there, give a bit bigger hole to look through, 7mm instead of 4) to look for contact marks, so I'm just gonna hope for the best until the head comes off to be swapped for a much more extensively modified one.

ETA: it was VERY hard to start, had to heat the intake manifold up with a torch and give it plenty of propane to get it running from cold (10 degrees F). Seems to start a lot better now.

Subscribed to this awesome thread .................. more room for error than the average individual understands.

oldpoopie said:

Am I the only one who sees the irony of this?

Click to expand...

Not even close bro.

If you've not already subscribed to this thread, I'm putting in a good word to ask that you do so soon. If you've not seen, this thread, I'll have results a little later this week. Nothing is ever perfect and the old adage of your milage may vary does apply. However, there is a distinct/substantial/clear difference in a variety of driving or operating characteristics between the Colt cam and the OE cam. Please recall the OE cam in reference is a 1Z/ALH profile cam. The type of driving the car is used for should be a heavy factor in the decision making of this cam.

I'm checking my subjective observations, which don't have decades of automotive experience let alone, with those who've been kind enough to lend an ear and are respected on the forum before I post them up to keep things concise. In addition, I aim to keep things in one place and given that the visible work FUB has listed here, once I've had a chance to organize the data I've collected, I'll be posting the dyno graphs, VCDS graphs & logs, along with analysis and observations from Saturday's results.

-See you soon!

Subscribed.
Looking forward to your results.
Thanks!

Subscribed also...


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