Lifter Research Findings - Final

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Lifter Research Findings - Final

Postby FRP » Fri Sep 26, 2014 2:54 pm

Hi All.
Thanks for your patience on me getting back to you all on this. The facts reported here are not meant to be critical of anyone or any organization in our community - they are - just facts.

I have not gotten my data back from my camshaft consultant in California (he went on vacation) but I do feel I have enough information to conclude what factors were involved with the failure of the new lightweight lifters in Nick's engine.

Before I move on to the lifters themselves, I think it would be beneficial if I took a moment to describe some of the mechanical and dynamic factors which effect valve train components in general and our 5 cylinder lifters in particular. You can all imagine that valve spring rates have an effect on the required material and design strength of the various components which activate the valves. In addition I am sure you are aware that cam lobe shape and more specifically what is referred to as "lobe acceleration rates" also impact the same components.

What you may not be aware of is the differences between factory and aftermarket cams in the way that they interact geometrically with the cam followers - be they bucket type, finger follower, lever arm and etc. It is an unfortunate circumstance that most aftermarket cams end up having smaller base circles than the factory cams they replace. This factor is consistent throughout the industry whether you are dealing American V8's or Asian or German engines. This is due to space envelope constrictions and in a lot of cases a lack of a appropriate core blanks from which cam makers work.

The case of the Audi I 5 is a good example of space restrictions around the cams limiting how large the base circle can be if adequate lift figures are to be obtained. The lobes can only be so tall before unacceptable amounts of machining and clearancing of the head become necessary to let the cams rotate. So, the base circle diameter must be reduced to achieve the desired net lift at the bucket / valve.

The downside to base circle reduction with Audi bucket style lifters is that the lifter then rides higher out of its bore, which mean it is less supported and more tippy in the bore which increases side thrust on the bucket and required opening force (to some probably unknowable degree). When you combine this factor with higher spring rates and more aggressive lobes, is it easy to see how the top of the lifter bucket
becomes more highly stressed. The factory Audi I 5 cams have a base circle diameter of 1.497 inches. The Cat cams in Nick"s motor have base circles of 1.455 on the intake and 1.460 on the exhaust.

The other factor, which is dynamic, is simply boost pressure. Turbo engines, particularly small displacement engines running on relatively high boost pressures, run in constant pressurization of the cylinders when under hi boost. In other words there is never any actual vacuum in the cylinders. Even at full exhaust blow down there is still residual pressure so intake valve opening forces are mildly affected. The exhaust valves are another thing all together. Turbo engine exhaust valves have to open against considerably more pressure than in N.A. motors.
Depending on dynamic conditions, (boost pressure, rpm, valve timing) the forces that exhaust lifter buckets see during valve activation increase dramatically. This is why all of Nick's failing lifters were on the exhaust cam.

Now on to the lifters themselves;

I dissected a factory lifter, an INA lightweight lifter and an INA OEM standard weight lifter and the lifters were all weighed on a gram scale.

Here are the particulars.

The factory lifter weighs 71 grams, the INA OEM replacement lifter weighs 64 grams, and the INA lightweight lifter weighs 50 grams.

Material thicknesses were;

Factory lifter- deck face .097 and side wall .060
INA OEM lifter - deck face .094 and side wall .060
INA Lightweight lifter - deck face .078 and side wall .039

There are additional differences in the internal bridging and buttressing which you will be able to see clearly in the pictures I have sent to Hank for posting with this article.

The factory lifter is typical Audi super robust meant to last 300K miles type stuff.
The INA OEM replacement "standard weight lifter" appears to be well constructed with adequate material thickness and stiff structure.
The INA LW lifter is, upon deconstruction, clearly inadequate - in material thickness and internal bracing - for use with aftermarket cams and springs in a high performance turbo engine.

These lifters may work adequately and have an acceptable service life with stock Audi cams (including 7A) with boost levels up to about 23 pounds - but I would not recommend them even for that type of use. They are absolutely unsuited for any type of real high performance use.

I am sorry that I was unaware of the inadequacy of these parts, but I had in fact, relied on statements and the belief that their use was wide
spread in our familiar engines in high performance specification / application. I have only installed 3 sets total in my customer engines and one set was supplied by the customer. Fortunately, 2 of the three are not yet in service and will have the LW lifters replaced with standard weight lifters. ALL of the other Audi I5's engines that have come from FRP have either retained the factory lifters or have been solid lifter conversions.

If you have factory lifters that do not exhibit leak down and clacking, ticking etc. and do not have a discernible wear pattern on the contact surface I would suggest keeping them and just going with up rated valve springs and lightweight retainers. If you are installing new cams I suspect that using cam break in lube during install and zinc treatment in your oil for the first oil change after install will allow the cams to mate just fine to your used factory lifters.

If your factory lifters are in bad shape I am relatively certain you will have good luck with the INA OEM replacements. I have just purchased a
set for a customer engine currently under construction and I will be stocking them from here on.

Lightweight on left, Stock center, stock replacments right

Image
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Re: Lifter Research Findings - Final

Postby ringbearer » Fri Sep 26, 2014 3:14 pm

Awesome info Jeff!

I have a 3 year old NIB set of INA lightweight lifters I will not install in my engine.

I need less "upgrades" of this sort, thanks.
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Re: Lifter Research Findings - Final

Postby scubagli » Fri Sep 26, 2014 3:32 pm

Good info too bad Nick had to learn this lesson for us.
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Re: Lifter Research Findings - Final

Postby audifreakjim » Fri Sep 26, 2014 4:13 pm

It will be interesting to see what goes first, my LW lifters or my stock exhaust valves. I am really glad I didn't pull the trigger on bigger cams a few months back.
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Re: Lifter Research Findings - Final

Postby All_Euro » Fri Sep 26, 2014 7:11 pm

Jeff, thanks so much for detailing the process and sharing so much info - really helpful stuff. Nick... this really sucks for you but again, thanks for sharing :beer:
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Re: Lifter Research Findings - Final

Postby yodasfro » Fri Sep 26, 2014 9:11 pm

Jeff, here's a question for you when installing lifters does the orientation of the oil feed holes matter? Should the feed in the lifter bore be lined up with feed hole in the side of the lifter?
Or should they be 180* degrees of each other? Maybe it does not matter one way or another?
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Re: Lifter Research Findings - Final

Postby loxxrider » Fri Sep 26, 2014 9:53 pm

Again Jeff, thanks for sharing this. It's a great lesson learned for all of us here!
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Re: Lifter Research Findings - Final

Postby kieron_32v » Sat Sep 27, 2014 1:52 am

yodasfro wrote:Jeff, here's a question for you when installing lifters does the orientation of the oil feed holes matter? Should the feed in the lifter bore be lined up with feed hole in the side of the lifter?
Or should they be 180* degrees of each other? Maybe it does not matter one way or another?

Can't see it making any difference as the lifters likely rotate in the bore due to the slightly offset on the cam lobes relative to the bore. You can see it in the wear pattern on the top surface. I would imagine intentionally too otherwise you'd just be wearing on one surface and end up with a ridge.
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Re: Lifter Research Findings - Final

Postby PRY4SNO » Sat Sep 27, 2014 7:37 am

Great read as usual, and I appreciate the learning opportunity gained from everyone's hard work.
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Re: Lifter Research Findings - Final

Postby FRP » Sun Sep 28, 2014 7:35 pm

Regarding lifter orientation within the lifter bore : They rotate constantly within the bore. Lobes are slightly offset and the lobe face has about .0005 of camber grind which works with the offset to insure they rotate. Hence no wear pattern. Bazzillions of lobe cycles spread over zillions of lifter revolutions.

Same thing with push rod engines and cam in block.
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Re: Lifter Research Findings - Final

Postby yodasfro » Sun Sep 28, 2014 8:20 pm

Good to know.
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Re: Lifter Research Findings - Final

Postby SEStone » Mon Sep 29, 2014 1:01 am

One other lifter option might be Porsche 997 GT3 exhaust valve lifters. They are built like a solid lifter bucket, but where the peg and lash cap go is a little version of the hydraulic lash adjuster you usually find in these lifter. We have a whole bin of them at work, I'll try and get some dimensions if I can this week.

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Re: Lifter Research Findings - Final

Postby ringbearer » Mon Sep 29, 2014 10:44 am

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Re: Lifter Research Findings - Final

Postby Mcstiff » Mon Sep 29, 2014 11:10 am

:hide: OT

Are these more robust?

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:hide:"
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Re: Lifter Research Findings - Final

Postby audifreakjim » Mon Sep 29, 2014 11:19 am

You din't
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Re: Lifter Research Findings - Final

Postby SEStone » Mon Sep 29, 2014 5:49 pm

Damn, my bad, the small lightweight guys are on the intake side. They're smaller outside diameter than the exhaust lifters, which I believe are the same size as the old vag stuff.
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