240Z Turbo Posted October 11, 2002 Share Posted October 11, 2002 I will start by saying I have NEVER said I know how to design a cam and my cam is based on info I have tried to gather. I also ran across some specs of a JUN turbo cam. I have heard ramp rates are critical so I tried to find a cam whose gross duration was close to the duration@.050" which would signify a quick ramp rate. Anyway, ran across WEB cams and Grind 155: WEB CAMS I had them spread the LC from 109 to 110.5 and it seems to work well. Unless you have the proper modelling software and specific information for a specific engine, you have NO WAY to properly design a cam. Guessing at specs and trial & error IS NOT designing a cam. I agree that there is no substitute for experience and that experience can get you in the ballpark, but that is as good as it gets. If I chose 100 grinds and 1 of them happened to work just awesome could I say I designed that cam? NO, I could say I god damn lucky! How many have gotten a cam and been unhappy even after Mr. Iskidarian or Mr. Crower themselves made the recommendation? My problem is this, when you say the word design and you have only guessed at specs based on experience and not modelled it based on your particular engine, ie. discplacement, flow, port configuration, reversion, yadayadayada, then to me, it is not cam design. JUST my opinion. I am going to be fortunate because TimZ is going to baseline his new motor with his ISKY stage I cam and then swap to the cam I am using to get some hard data as to the performance increase. So to end my story, I think the best we can hope for are a couple of different cams that can encompass a particular style of setup, power range and that are application specific. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted October 11, 2002 Share Posted October 11, 2002 JWT designed theirs. That cam is the same spec as my NA cam in my 2.8 with the exception of .5 degree more LC. If I put that cam in my turbo engine, I could probably turn the thing to 8 grand. How is it that it doesn't have to much overlap? Seems to me it would have to have overlap. I don't even see datsun/nissan listed on ISKY's site anymore. http://www.iskycams.com/ Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted October 11, 2002 Author Share Posted October 11, 2002 JWT designs their own cams. According to JeffP, design=theft. So JWT has a new Turbo cam A. Well let me tell you a little about this cam. I could be wrong, but it seems they have adopted a grind I designed and now are making a few bucks off of it. That really sucks. And according to JeffP, I had Elgin cams grind a cam for me and that was installed on my cylinder head. So, we know the following:design=trial&error design=theft design=calling Elgin cams for a proposed grind Please nobody go ballistic here, just intended this post to clarify the capacity to actually DESIGN a cam. I would hope in the end we can compile a list of cams used and the results so someone can atleast select a cam that will benefit their particular setup and not waste money getting 5hp. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted October 11, 2002 Share Posted October 11, 2002 WHat about the overlap though? That is what I want to know about. A cam as big as yours has to have some overlap doesn't it? How is it that a cam with overlap works in a turbo engine when everything out there says it is not the way to go? I mean I have tried an NA cam in one of my turbo engines before and it ran like junk. What makes this one different? Is it the wider lobe center, what? Why not answer questions instead of trying to push peoples buttons? Your post is technical in nature, and is about cam design, and I want to know why a cam that you have that judging by the spec's, would not necessarily be one people would think to use in a turbo application, yet it works for you. Based upon what I see, I could take the cam out of my NA 2.8 and stick it in my turbo engine, and even with 40 plus degree's of overlap, it should work. I don't see how. Break it down for me, I am missing something. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted October 11, 2002 Share Posted October 11, 2002 I am also curious about this ramp rate thing. I have two cams from the same grinder, both billets. Both are listed as 288 advertised duration, yet one is 234 @50 and the other is 218. What is the deal with that? Does it mean the one that is 218 has a slow ramp? What are the advantages/disadvantages of that? I had always heard that the advertised duration was "creative" which is why there is the 50 thousandths spec. That is what keeps the people honest. Come on somebody tell me what the deal is with this stuff. I am curious. Quote Link to comment Share on other sites More sharing options...
Mike C Posted October 12, 2002 Share Posted October 12, 2002 "Advertised" duration cam only be used to compare cams if they are all "advertised" equally. For instance with SBC cams, Crane specs their cams at .005 tappet lift for advertised duration, and comp specs theirs at .006, while GM specs their cams at .001". That is why a compareable Crane cam seems "larger" than a comp to get equal .050 numbers. GM cams for a 69 Z/28 is something like 345/345 advertised duration, but .050 is only in the 250 range. .050 is the industry standard and is quite useful in comparing cams, and like James said, the closer the .050 number is to the advertised number, the faster the ramp COMPARED TO ANOTHER CAM THAT HAS THE SAME ADVERTISED DURATION POINT! There is also a law of diminishing returns in effect. The ramp speed can only be so fast before exceeding the design range of the tappet assembly. Thus the high failure rate with the early Comp Xtreme energy cams... Not Datsun cam specific, but hopefully sheds a little light on the subject. Quote Link to comment Share on other sites More sharing options...
jeffp Posted October 12, 2002 Share Posted October 12, 2002 I agree with you James that you need to know th specifics of the engine Ie Head you are working with. The flow through the haed is significant. For instance, a fully ported and polished P90 head will folw X amount @ .500 lift. Increasing the lift further actually hindered the flow of the head by a few CFM. This was the case with the exhaust port. I have a data sheet on the P90 head and its flow rates at .200-.600 lift of the valve on the flow bench. According to the data anything higher then .500 lift only decreases the flow rate of the head. Lockjaw: in a turbo application, the best grind will be the low overlap cam in most cases. The fact that you are say pushing 20psi into the cylinder along with what the swept volume of the assembly is is dependant on the overlap and how much you will actually pressureize the cylinder. There are tricks you can do to increase the overlap and hinder the charge trying to excape through the other valve. For instance, in a N/A engine you want the intake/exhaust ports matched to the port on the head. With a turbo application, if you make the port a little larger then the intake manifold port, when the air/fuel tries to excape through the valve that is cracked open slightly the smaller port opening into the manifold hinders the reverse action of the air/fuel mixture. The N/A application you want them matched, because you want the best flow and a good smooth passageway into the cylinder. Then if you put a tunnel ram for the intake manifold and provide a longer passage way into the cylinder head, the tunnel ram helps in packing the cylinders with the air/fuel mixture. This doesn't apply in the turbo application as it is forced air induction. So you can cheat a little to get a slightly larger cam (for topend power) then you would think. The londer overlap will make the cam more of a midrange to top end power producer and the bottom end will begin to suffer. The @ .050 reading is the industry standard for the most part, However with the new cam machines being produced and the addition of a computer controlled grinder (in stead of the older cam lobe master for each grind) you can hold a tighter tolerance. You get closer to the actual opening of the valve this way and a more accurate indication of when the valve lifts off of the seat. For example, a cam that opens @ 36 degrees BTDC @ 50 well the lobe has already lifter the valve off the seat .050 so in reality the cam opened the valve earlier. anyway just some of my thoughts. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted October 12, 2002 Share Posted October 12, 2002 Well it sounds to me like the advertised duration doesn't tell you jack unless you are comparing cams from the same manufacturer. I mean if you have a crane that is advertised at 280, a comp cam at 268, a crower at 288, and an isky at 270, and they all are 220 at 50, then it sounds like to me, they are all pretty much the same cam. I don't see how you can say you have a more aggressive ramp rate with one versus the other, since it sounds like some of the grinders are less than truthful about what they are truely grinding. Then I looked at the Webcam link James put out there, and the larger cams would appear to have a faster ramp rate based upon his criteria, so wouldn't that make them better suited than the cam he chose? Sounds to me like I could pick a cam from each manufacturer and put them all in a hat and pick one and be just as well off. Jeff I have seen some numbers on head flow that showed what you describe, to much lift starts to hurt flow. I guess I won't have to worry about that with this little cam I have. I also thought one area that was improved on the p series heads was low lift flow. I hope that is the case. Quote Link to comment Share on other sites More sharing options...
Mike C Posted October 12, 2002 Share Posted October 12, 2002 Another reason to use .050 lift numbers is it allows you to make reasonalbe comparisons of mechanical and hydraulic cams because it removes the valve lash variable which can be as much as .030 on the exhaust of an older cam and as little as .015 on the intake of a modern grind. Quote Link to comment Share on other sites More sharing options...
jeffp Posted October 12, 2002 Share Posted October 12, 2002 One thing to remember is that the more common heads today dont use the hydrolic lifters. The Amreican engines still use them in their standard builds for the most part. Ford for instance uses a hydrolic lifter with a roller cam in the 3.8 liter engine. Subaru uses hydrolic lifters. The L series head uses a mechanical lifter, except for the P90A head. So yes a hydrolic lifter engine is a consideration when selecting a cam. Quote Link to comment Share on other sites More sharing options...
TimO Posted October 12, 2002 Share Posted October 12, 2002 OK Donna I'll wade in. For those of you who don't know me my engine is very similiar to Joel in La and TimZ(when he gets his TWM's). Donna's motor will soon join us. I normally don't join in on these posts but after reading the many and varied posts about camshafts, heated exchanges, and the mine is the best way comments, I'd like to say that I'm concerned that when posts are made, the newcommers check the advise on these posts with the professionals at turbo shops, cam builders, and the major Nissan speed shops such as Sun Belt and Rabello, etc before they take as gospel, the advise of those who appear to have limited experience and may be expermenting with their unproven set ups., as we all are as hobbiests. A number of comments and posts I've read lately are not based on sound science and correct physics. I think when we give advise, especially to the new guys (and gals..sorry Donna), that we make sure and let them know that our successes, and yes our failures, are just ours individual experiences and are not to be taken as an absolute. A simple example is camshafts....comparison of camshafts is a science that must be base on an established baseline of data which is virtually impossible to generate on a forum because many factors change from one engine to another especially when you consider different heads, porting, cam timing, etc. I think its great to learn what works for each of us,and whey you think it worked, but lets be careful especially for the new poeple, to let them know the perameters in which we have successes and failures with our motors. Hope I didn't affended anyone. TimO Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted October 12, 2002 Share Posted October 12, 2002 I don't know who Joel is either. Quote Link to comment Share on other sites More sharing options...
D83ZXT Posted October 13, 2002 Share Posted October 13, 2002 Welcome aboard Tim:D Hehe.. finally! Lockjaw, Joel aka: J.Soileau 260ZT is his user name here. http://zdriver.com/rides/detailride.php?cat=1&relIdx=23&vehId=944 Donna Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted October 13, 2002 Share Posted October 13, 2002 WELCOME TIMO Quote Link to comment Share on other sites More sharing options...
D83ZXT Posted October 13, 2002 Share Posted October 13, 2002 James, What about the Web's 155A? (CL moved to 110.5) Right now Dave Robello is talking with Isky, and we (TimO and I) have Reed is working on configurations also. I know TimZ likes his Isky and you are happy with your's from Web. Decisions, decisions........ Are we having fun yet? Come on Guys us fellow Z'rs need more info TimO....Are you going to speak up here? Donna Quote Link to comment Share on other sites More sharing options...
Mudge Posted October 22, 2002 Share Posted October 22, 2002 Do any of you folks have Engine Analyzer or Destkop Dyno files to play with? I haven't been able to find any straight 6 files on the net, for stock or other Datsun setups. Quote Link to comment Share on other sites More sharing options...
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