zxtman Posted March 25, 2003 Share Posted March 25, 2003 lift 480/480 dur 280/270 lsa 110 for a 400+ hp L6 motor. Any comments appreciated. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted March 25, 2003 Share Posted March 25, 2003 That is virtually the same cam I ran, and will run again when I get my head swapped back on again. The specs on mine are 280/270 duration, lift of .460/.460 with a lobe separation of 114. There is an almost imperceptible lope with mine, I suspect you will have a bit more with less lobe separation. At .050" lift, my cam has -7 degrees of overlap (doesn't overlap very much). I love the way it pulls, doesn't seem to lack much on the low end compared to stock, but at 3500+ rpm it pulls to 6500 like a train. My fuel cut hits there, but it would keep pulling if it could -- very unlike the stock cam that noticeably runs out of steam by 6000 rpm. I can't tell you how it runs with lots of boost - the most I ran with it was 9psi (before I put on the IC). As soon as I get my ECU mods in place and tuned, I will put on the P90 with the turbo cam again and compare (I've run with a stock motor all last year). Quote Link to comment Share on other sites More sharing options...
jeffp Posted March 25, 2003 Share Posted March 25, 2003 I am running simalar to what you have. The thing I have noticed about the grinds is that they are running out of power at the top end. Now my cam is a 266 duration, with a 112 lobe center and a lift of .485 for the intake and the exhaust. You have a little more duration and lobe center and that is going to help out the top end power. I was right in the middle of testing my grind when I found out I had a defective damper so I have been waiting to resume my testing after I get the new part. I think the 280 duration will be the key to good hp and torque on the top end, but I just have to wait and see. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 25, 2003 Share Posted March 25, 2003 Why less exaust duration? It should be alot closer to a single pattern cam, unless they are just using a more aggressive ramp on the exaust side but by 10º would be very unusual. Sticking to a tight LSA usually keeps the turbo spinning, so I'd stick with that. You will also often times see a single pattern, with just less lift on the intake side. I'm guessing that .050 this is a 220 or 225 cam? If so that is about the most I'd go with, a 230 would take away the bottom end to the point that I'd feel like I was in an NA car on the low end, and alot of the reason I went turbo was for retention of the low RPM. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted March 25, 2003 Share Posted March 25, 2003 Turbo doesn't like choppy exhaust. Smaller duration, less choppy exhaust. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 26, 2003 Share Posted March 26, 2003 Since the intake is being force fed, you dont need nearly the total duration on the intake side. However if you dont have exaust velocity then the turbo wont make the boost that it could. More intake duration is a bandaid for poor intake efficiency, which is what the LS1 guys are using as thier bandaid. In a force fed app its not an issue. If this is being touted as a turbo cam then there could be more too it though, like some strange ramping scheme, otherwise from the specs provided it doesn't look like a turbo cam to me, but again without the whole picture there is not enough data. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted March 26, 2003 Share Posted March 26, 2003 Ok, how do you increase the exhaust velosity with more duration? I think it'll increase the volume and actually slows down the velocity. Would you not get more velocity from squeezing alot of air our in short period of time(more intake, less exhaust) than same amount of air going out in longer preiod of time? I know on N/A more split pattern usually have less intake because the air intake relies on the scavenge and the air velosity is higher with smaller intake duration(more vaccum and better response). But under boost, you don't need scavenge since the air is forced in. So the intake can stay open longer to have more air to compress. That's my understanding of it The downside is bad idle and poor respond off boost. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted March 26, 2003 Share Posted March 26, 2003 Ok, how do you increase the exhaust velosity with more duration? I think it'll increase the volume and actually slows down the velocity. Would you not get more velocity from squeezing alot of air our in short period of time(more intake, less exhaust) than same amount of air going out in longer preiod of time? I know on N/A more split pattern usually have less intake because the air intake relies on the scavenge and the air velosity is higher with smaller intake duration(more vaccum and better response). But under boost, you don't need scavenge since the air is forced in. So the intake can stay open longer to have more air to compress. That's my understanding of it The downside is bad idle and poor respond off boost. Not sure what you are saying is accurate. Less duration presents more restriction to the exhaust. If you restrict the exhaust less, you have more energy to feed the turbo. Obviously there is a limit though, you don't want to open the exhaust before you have finished pushing down the piston Quote Link to comment Share on other sites More sharing options...
Guest cfrench Posted March 27, 2003 Share Posted March 27, 2003 I think yo2001 is saying that with the restriciton comes high velocity. This is true, however with the restriction your result will be less exhaust leaving the cylinder but the exhaust that does make it out will do so at a much faster pace. His error in thinking is that a small amount of gas at a high velocity will turn the turbo faster. In actuallity, small amount of gas will have less volume behind it to maintian speed once it hits the turbo. OR using maximized duration will provide ample gas volume at a slower velocity which will do the same as a short burst at high velocity. MASS x velocity = mass x VELOCITY larger mass=MASS smaller mass=mass ect. A better method to speed exhaust would be to maximize duration and decrease (i think they're called primaries) the primaries size on custom headers. This, Therodically would push a large amount of exhaust gas to the turbo at a rapid velocity. If the restriction is too much, however, it may have a negative effect do to too much back pressure. This is were header size, length and shape become really important. If you like math and physics you'll have a blast making a well tuned set of headers. I'm only 18 so If I'm drastically wrong... well I haven't hit college physics yet. However, I am one of those kids that can't wait for it. Quote Link to comment Share on other sites More sharing options...
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