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There is some nominal benefit in harmonic dampening with the two springs having a very slight interference fit, but that is outweighed by the stresses placed mostly on the inner spring so in modern designs it's not done these days, and the heat it generates. The inner spring design for about every 911 aftermarket spring on the market now is very overstressed even without the interference fit, and that's because they're based on decades old designs with no thought given to recent advances. I can't blame them really, if it works don't fix it, but if modern design can make it better then that should be pursued. The spring metallurgy around these days is a big changing factor, as they are far superior with alloys containing vanadium, nickel, silicon, and chromium. The material is also far cleaner than ever before resulting in ultimate tensile strengths being far higher. A modern design likely would never have worked decades ago simply due to materials. Advances are obvious but some of the fuddy duddies need to pipe down and let the engineers handle it. |
Fuddy Duddy
I have been called a few things before.So I will take this as a new form of endearment.But since I am old it is probably fitting.Ciao Fuddy Duddy Fred
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titanium retainers
Neil, your take on titanium retainers seems to conflict with Steve Weiner’s experience and advice. For instance, you say that most titanium retainers are cheaply made and full of sharp edges and are not coated.
Yet I’ve seen posts by Steve where he points out that titanium is an excellent choice for retainers and he further explained that the OEM sintered Metal has the propensity to crack and therefore the Ti retainers are more durable and lighter, too. There are a number of us that use Ti retainers from AASCO, EBS, etc., and I haven’t experienced these wearing any quicker than OEM ones. Is there some brand that we should stay away from? When did you discover this and in what engines? I understand that valve seat pressure must be optimized but I’m not in agreement yet on the use of Ti retainers. |
A clarification..
The 3.0 & later ones are sintered, not machined and that means they can fracture if you ever miss a shift. The 2.7 and earlier ones are machined steel and will not break. |
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Titanium has its place and its very common to run retainers made from this material, but here are some requirements when using these. They need to be inspected and crack checked often and replaced when any sign of wear exists. The trouble with selling them to the customers with street engines, inspection is never done unless the engine comes apart. Unlike race engines. If you have these retainers I would be shocked if there is not wear or damage to the contact face between the retainer and the spring. For sure the sintered streel retainers are junk and are known to fail. My suggestion for street engines was to consider a lighter tool steel alternative where the wear rate is a lot lower than Titanium. The use of this along with well design cam profiles will make a big difference. Yes we want to lighten up the valve train. No issue with this. Mine concern is, the retainers are often sold as an high performance upgrade, with springs that put 100+Lbs on the seat at installed height, and a poorly designed or copied cam is driving these parts. The cam induces huge harmonics, unknown to the driver, the springs go nuts trying to stay connected to the cam lobe, and the lighter retainer does not do what it was intended to do. The correct fitment of a retainer to a spring is with some interference so the spring does not move. But the springs are often with sharp corners too, and these dig into the retainer along with the contact faces. There is no way titanium running hard against a vibrating spring does not show signs of wear. |
Thanks Neil for the detailed post. It’s a good discussion for considering potential use of Ti retainers.
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Hi Neil,
I understand and agree with what you are saying about not using more seat pressure than necessary, and that a bad cam design could be compensated for by using heavy springs. I know you are being very diplomatic by not naming names. But I took a high performance engine building class with Dema Elgin (of Elgin cams) in 1990, after which he invited me to a tour of his cam shop in Redwood City. And even then he was using software that allowed him to analyze the velocity, acceleration and jerk of the cam shaft and he took all of that into consideration in his designs, even in the 90s. If other cam makers made poor copies of his cams or the GEs, I could understand, but the way you are presenting your analysis of existing cam designs seems to cast doubt on all currently available Porsche cams. If the improvement you are making is due specifically to the fact that you are able to CNC the cam to spec vs grinding a master with imperfections or that wears out of over time, that makes sense. But I'm less convinced by a general statement that currently available air cooled cam designs are generally bad copies and you can do better with no supporting documentation or examples. Looking forward to hearing more about the new products. cheers, dug |
We have started to compile a full list of the air-cooled cam profiles we will offer. This includes all the standard stock profiles, but our intention is to offer our improved versions of many of these along with some profiles we have done in the past years for custom engines.
These include starting with, 356, 904, 951, and 928 cams we have created. The later water engine profiles will also be included dating back to the custom 962C grinds up and including the very latest 991.1 GT3 solid finger profile. We intend to offer both 47.00 and 49,00mm journal sizes, including a 3-journal cam with a bolt instead of the early style large nut. All cams will be supplied on new billets with DLC coated lobes. A re profiling service is also offered, but welding repairs are not something we wish to offer. I have also authorized new Valve covers to be designed that include a secondary oiling system for the camshaft. We have all the stock profiles, including the 911E, 911T, 911S, 911 SC, 964, 993 Hyd. Profiles. Of our custom grinds we have many variants of the following including some of our A symmetrical designs. 356, 904, 911 improved, SC ½ step, 911 race, 930, 930 race/GT2, 964 improved, 993 Hyd improved, 993 non-hyd. All 911, 964 and the 993 non-hyd cams can be used with our solid version of the forged 993 rocker arm. Of the water profiles we have 962C, 951, 928, 996 and 997 GT3, street and race, 996/997 Turbo street and race, and the very latest 991 GT4 and GT3 non-hyd. These later 4V cam shafts are being manufactured in house and we do intend to make the 2V shafts the same way in the future. This will lighten up the shafts, allow for additional performance to be added and center oiling if ever required. I will have a more complete list up on our web site every soon with the seat durations and lifts included. We will not show the 0.050” durations on any of our improved, ½ step or custom designs. Our sales model is to offer a better match for each engine with modern designs, lower manufacturing tolerances, and quicker turnaround times. Custom designs will continue to be a large part of our business and with the Landis CNC grinder up and running shortly, we will be able to do this without the need for masters to be made each time. Neil Harvey Performance Developments |
I am behind in posting on our web site our cam choices. Is there some sort of Porsche event happening soon?????
Our business model is to offer more modern designs, but we will offer the standards as well. We use head flow numbers along with other engine data to better match a profile to the engine. This is not for all, but for those that want an engineered solution. All cams will come on new billets with DLC lobes. We suggest that the rocker arms are coated as well, as these two parts run better against one another. The friction is dramatically reduced, removing lot of the damaging temperature that causes the wear. We have been using this technology on our own engines for many years and now are offering it to all. |
http://forums.pelicanparts.com/uploa...1537665399.JPG
http://forums.pelicanparts.com/uploa...1537665808.jpg http://forums.pelicanparts.com/uploa...1537665842.jpg An example of a set of cams we just did for a customer. |
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Firstly, I would like to say that I am sincerely excited about the custom cam manufacturing service that you intend to offer. This prospect has raised a number of technical questions in my mind, which I hope you will be able to share the answers with us on this forum. Background to my questions Big OEMs and the top Motorsport companies have dedicated specialist engineers that use engine simulation and design software such as Ricardo Wave or GT Power. The rest of us (mere mortals) do not have the money nor the specialist know how, to play with that league of “toys”. Fortunately, there are some alternative options that are within a more realistic cost ballpark, should someone choose to invest in such means. For example, EngMod4T for the engine design and simulation and 4stHEAD for valve train analysis and design. This opens up the possibility for “mere mortals”, to conduct multiple “what-if” scenarios of inlet lengths, exhaust primary & secondary pipe lengths combined with the various available camshafts profiles. This approach will enable you to derive a package that is improved over the next guy which has only guessed at it. We need the basic valve lift profiles in order to conduct the “what-if” scenario simulations in EngMod4T. The cam/valve data typically published by the popular camshaft suppliers is adequate for ball-park simulations and rough comparisons. It is even better if one physically measures the actual valve lift per deg of crank rotation and uses the measured data in the simulation. Obviously, this is not possible if you don’t have the desired camshaft in your possession. Without digressing into boring nitty-gritty details, EngMod4T & 4stHEAD both include Prof Blair’s cam design tools. Which then brings me to my questions: Q1) I have access to 4stHead. 4stHead can export the designed camshaft to a .p manufacturing data file compatible with Landis-Lund . Would you be able to use this data to grind a custom camshaft? (off course, I would need to tell 4stHEAD the Dia of the grinding wheel intended to be used). Q2) What type of opening ramp do you use for your improved camshafts? (constant velocity? Or something else) |
Very useful information there Neil, thanks,, Samuel.
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Regardless of what level of software you have and use, the data inputted is critical to getting accurate results. We have several of the Ricardo programs and have taken a lot of time to get the results from these to give accurate collation to the dyno and track. This is key. But these lower level programs can be extremely useful in doing the hard math. They can give really good cylinder filling info, component speeds, all the indicated data, along with crank, piston positions and valve lifts etc. Very useful when doing Piston to valve clearances for the average DIY builder. Buying cams has being mostly based upon someone else's idea of what performance you want. Head flow numbers all the way through the complete intake system should be used, along with the engines performance goals. Where do you want the torque and do you need wide flat torque curve or is peak torque your needs? There are drawbacks to each. Slower engine acceleration comes with a wider LSA along with more area under the curve, a broader flatter curve and higher RPM possibilities. But if you want a quicker rev'ing engine, shifting the peak torque value down the RPM band, you need to narrow up the LSA. Pretty basic stuff but every engine is different, its use is different and the driver probably drives differently. So should the cam design. There are "tricks" that can be done in the design to fool the engine into thinking it has different specifications. These 2V Porsche engine react well to these 'tricks". The later engines with longer strokes can be influenced by cam design to help fill the big chambers they have. Its like having your cake and eat it too. The LSA numbers can come down from where they need to be on the earlier shorter stroke engines. It needs to be decided by the owner what performance expectations he or she wants taking into consideration fuel economy and emissions compliances. To answer your questions, if I understand what you are asking, the ramp design is critical and one of the reasons why we will give the duration numbers at 0.050" only. The ramp controls the velocity, acceleration, jerk and any follow on harmonic orders. When talking about the cam lobe, you want the velocities and accel numbers to be "continuous" during the whole cam motion but these can be "modified" by rocker/finger pad radii, followers with radius curvatures etc. Flat tappet designs are somewhat constant and the lobe is the only factor on how the valve is controlled. Without saying "yes we can use anything" it would be best to know exactly what you have etc. I would not like to say something we cannot do or use. Hope this helps. nh |
Neil it is great that you have entered the fray I am sure you will not suffer from instrumentation for data collection and that you would not be just re branding others products, what are you using to quantify this bad behavior of Dema Elgin, John Daugherty, Jim Dewar of mega cycle and Schrieck?
I am sure your have Audie or Adcole it would be informative if you would show the basis of your assumption. regards |
The acid test or proof is always in the “pudding”.
Our business model is to offer a solution where the customers car use, engine specification and especially the engines air flow ability is used to better match one of our existing profiles or design one to suit. There are certainly different levels of quality currently offered. Some designs are based on copies, some good, some bad. The same can be said for other areas of the engine, machine work, other engine components and assembly procedures. In the end, you decide what you wish to sell and to whom. You can sell a Rolex or a Timex. The customer decides what level they are comfortable with. That comfort level should be based upon a known performance expectation and their budget. It’s not for all. But for those that want something with less compromise and suited directly for their use and the engines specifications, our model is to offer this solution. This is a natural follow on to our normal engine programs. |
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Oddly enough Porsche and I believe Schrick employ a constant velocity ramp on both sides of the lobe be it intake or exhaust closing and opining and no independent grinders utilize this feature and go to constant acceleration. I swear it has been physically apparent to the naked eye on some 964/993 Factory racing cams. That being said the grinds of John Daugherty and Dema Elgin will be able to tailor to ones needs vs, the sedentary Porsche lobe engineering, maybe they know better or they have other fish to fry. anyway great input and questions as far as your grinding question I think the typical grinding wheel is 24" (for cost reasons) by the way for inverse flank it can get down to 6" but that is another story. And most of the guys here are grinding on Berco not Landis and definitely not the landis CNC grinders. regards |
^^^ How about you leave these cam grinders names off this forum so you don't cause them to run away and not come back? It sounds like you are stating their grinds are not good. I guarantee you, one of these guys you mention is part of a club of big, big power; not the club of 200hp which a lot of Porsche flat-6 motors hover around.
It's like a lawnmower engineer calling out imperfections on a NASCAR engineer's work. Comes off silly. Point is, not everyone can go to Schrick or others and are lucky to have budget friendly grinders....last I've heard, no valvetrain failures linked to a poor camshaft grind... |
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There used to be some lightweight chromoly ones out there, but I can't find them. Does anyone know of a source for good retainers? Is titanium my only option for race springs and high lift cams? |
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On the one hand, we should never underestimate the value of the tried and tested recipes of upgrade parts available to us (for example camshaft/valvetrain). Very few amongst us will have the budget to develop & test truly novel new designs...the cost of failure (which is an important part of learning) is just prohibitive! On the other hand, there is a wide range of customers, with a wide range of understanding of the engineering involved behind these things. Just because I can’t afford to play with high end stuff from company XYZ, doesn’t mean I am fool. I respect the work done and products offered by all the various suppliers of Porsche aftermarket camshafts. I also appreciate that each design has its constraints, limitations and maybe even shortcomings.....that is the reality of engineering. I also understand that most technical details and information will not be “shareable”... But if we are going to be talking about the availability of “better” products (than those offered by competitors), can we at least consider to discuss the actual technical details/merits of these “better” products? ....and not base the sales pitch purely on bashing the competitors I am not a camshaft guru....but I am keen to hold a discussion along the lines of: Prof Blair & Associates - 4stHEAD: Valve Lift Design - HMB Method Engine Professional magazine https://www.tildentechnologies.com/Cams/CamDesign.html |
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