Guest MegaShaft_2000 Posted March 26, 2001 Share Posted March 26, 2001 For starters the "5252" is not a representation of a tangit of "Torque" or "HP" so the assumption that they should cross on a dyno is incorrect. Thanks for the story, but in the end you said it yourself that Horsepower = RPM x Torque/5252 So by that formula: Horsepower = RPM * Torque/5252 Horsepower = 5252*T/5252 Horsepower = 1T So as you see, torque *DOES* equal Horsepower at 5252 rpm. It's inherent in the formula and cannot be avoided. Since that is the formula, ALL dynocharts should show the HP/Torque intersection at 5252 due to the fact that it MUST, as per the formula. They are intrinsically linked, and the intersection cannot possibly be avoided. Since this dynochart doesn't comply, the results are inaccurate. [This message has been edited by MegaShaft_2000 (edited March 26, 2001).] [This message has been edited by MegaShaft_2000 (edited March 26, 2001).] Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 26, 2001 Share Posted March 26, 2001 I haven't been able to get that link to work, but what's the possibility that someone applied a correction factor and that's why they didn't line up. Maybe the HP had a correction factor applied and the TQ didn't? Maybe the dyno operator was clueless or made some kind of mistake with the software? BTW, if one were to have an engine tested, can one get raw data from these dyno runs, so as to check the plots? Anyway, yeah, HP=TQ (ft-lbs) at 5252 rpm I don't think theres any room for argument on that, since HP is a derivation of TQ that follows that rule - it's a defined unit. BTW, ft-lbs = lbs-ft, any day of the week, unless you're living in different universe, multipliction is communitive, so you can say it either way and you're correct. Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted March 26, 2001 Share Posted March 26, 2001 Ok guys; I'm no engineer but I'm still confused as to why we are thinking that HP/Tq must cross on the dyno at 5252. The formula HP = RPM x Torque/5252 doesnt say (at least not to me) it doesnt say: 500hp = 500lbs.ft at 5252rpms. The "/" (forward slash mark) is not an "Equal" sign rather it is am instruction for us to "Divide". As I understand it: the "RPM" part of the equation represents "RPM" not the "5252". The "5252" represents "lbs.ft torque of 1torque"...so maybe the hp/torqe will cross...but at 1hp/1torque at the very beginning/not at the assumed 5252rpm's. Still the RPM is not determined by the "5252" of the equation. The RPM is a separate Perameter of the equation. So IMHO I dont see where the equation states that HP/Torque must cross at 5252rpms's(?). ****Okay, all best are off**** I was looking at some SBC & SBF dyno runs while typing this post; their HP/Torque #'s were crossing a tad passed the 5252rpm usually at 5300 or 5400rpm's/so am I rambling now(?). Am I rambling now(?). Am I rambling now.....does that mean I'm confused(?); do we have any engineers in the house? If so-please step forward & show yourself worthy! Kevin, (Yes,Still "Not an Engineer" but Still an Inliner) PS: Just left the upper half of this post in so everyone will realize I'm not anal that when my "Lightbulb" goes off I have no problem admitting that it wasnt previously "On" given the discussion at the time. I enjoy a good discussion/hammer away till its meaning is fully understood! Enjoyed this post as all posts on this site!! [This message has been edited by Kevin Shasteen (edited March 26, 2001).] Quote Link to comment Share on other sites More sharing options...
Drax240z Posted March 26, 2001 Author Share Posted March 26, 2001 I think I see your problem Kevin. You seem to be going about it the wrong way... HP = RPM x torque/5252 When RPM is equal to 5252 RPM, the formula simplifies to HP = Torque. (the 5252's cancel) Dyno's are all different, and we all know that they are best used for comparisons (On the same dyno) because of their inaccuracies. Thats why you see some crossing at 5300, 5400, etc. Just the in accuracy of that particular Dyno. ------------------ Richard Lewis - 1972 240z, Powered by a Nissan 2.8L Turbo Inline 6. Drax240's Turbo Site Beginners Turbo FAQ & Answers Quote Link to comment Share on other sites More sharing options...
johnc Posted March 26, 2001 Share Posted March 26, 2001 Thanks for education guys. ------------------ John Coffey johnc@betamotorsports.com Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted March 26, 2001 Share Posted March 26, 2001 Its always cool when My lightbulb comes on as my elevator reaches the top & I hear that "DING-DING"; Yes, We have a winner! Thanks Megashaft/Richard & Pete for keeping us in the right track...this foryum is always an education! I know I didnt creat the universe; so that puts me somewhere in 2nd place to last place in the Bread Line. Kevin, (Yes,Still a Inliner) Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 26, 2001 Share Posted March 26, 2001 Kevin, my apologies. I am an engineer, and equations are a way of life for me - I should have carried through with the thought. Drax pointed out the important issue, that HP is derived from torque and if RPM is 5252: HP = RPM * torque/5252 HP(@5252RPM) = 5252 * torque(@5252RPM)/5252 The 5252's on the right hand side cancel, so HP(@5252RPM) = TQ(@5252RPM) Again, if the dyno sheets don't show this, it's round off error, software error, or user error. ------------------ Pete Paraska - 73 540Z - Marathon Z Project pparaska@home.com Pete's V8 Datsun 240Z Pages Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted March 27, 2001 Share Posted March 27, 2001 Hey Pete; I somehow thought you were an engineer from some of your posts. Richard did ring it home w/the cancelling common denominator; I even illuded to the "Cancelling Commen Denominator" in my story with the 33,000 lbs.ft cancelling out by the "2 x pi" but missed it in the actual formula. My hurdle I was unable to get thru was a mental block as I kept picturing RPM as a progressive parameter (as if I was looking at my tach) instead of a particualr rpm within that formula; it didnt hit me what I was doing till Richard hit me over the head w/the 2x4; then it was clear as a bell! I guess we owe it to Megashaft for not letting us railroad him into believing we thought we knew what we were talking about. Anyway, still made for a very intersting thread which I enjoyed. Kevin, (Yes,Still "Not an Engineer" but Definately an Inliner) Quote Link to comment Share on other sites More sharing options...
johnc Posted March 27, 2001 Share Posted March 27, 2001 The only exception I see to this are diesel engines. You can't rev most diesel engines to 5252 rpms, but I guess if you extrapolated the curves out they would cross. And what about two stroke engines? ------------------ John Coffey johnc@betamotorsports.com Quote Link to comment Share on other sites More sharing options...
Drax240z Posted March 27, 2001 Author Share Posted March 27, 2001 It should be true for any engine, granted you'd have to extrapolate if the engine didn't rev high enough. Its not a result of a 4 stroke engine, or 2 stroke, diesel, gasoline or otherwise. No matter what the engine tested, its 5252 for all of them. Its the matter of HOW torque and HP are actually calculated. (see kevin's earlier post) Its the same for horses pulling levers, and for that matter, even hamsters running on little wheels. ------------------ Richard Lewis - 1972 240z, Powered by a Nissan 2.8L Turbo Inline 6. Drax240's Turbo Site Beginners Turbo FAQ & Answers Quote Link to comment Share on other sites More sharing options...
Guest norm[T12SDSUD] Posted March 28, 2001 Share Posted March 28, 2001 Guys ,this one is too easy!! Look at the dyno chart. If you will notice the far left and far right numbered side values do not correspond!! The dyno sheet is accurate . Simply look at the Torque reading at 5252 and you will see it is at 137 . Now, look at the horsepower curve at 5252 and you will see it is also is at 137. This is typically done when engines have much more torque than horsepower or vice versa and the chart would simply be too long to show both values. So ,instead they will run the Torque numbers on the left side of the column from say 300-500 and then run the Horsepower numbers on the right side from 250-350. I don't know why the dyno chart on this Z engine was made this way since both Hp and Torque are so close there was really no need to use a confusing two tiered chart. It confuses people when they glance at the two curves and see that they don't cross at 5252 when in reality they do, you just have to take the time to look at both sides of the chart to see which numbers are correspondent to which curve! later,norm ------------------ "Ya Gotta Drive IT like ya Hate IT!" Quote Link to comment Share on other sites More sharing options...
Guest norm[T12SDSUD] Posted March 28, 2001 Share Posted March 28, 2001 Upon closer examination of the chart, I see that the reading I posted at 5252 should be 136 for both tq and Hp and not 137. Later,norm ------------------ "Ya Gotta Drive IT like ya Hate IT!" Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 28, 2001 Share Posted March 28, 2001 Ahh. I couldn't ever get a connection on that web page until now. Of course, you're right. The curve that peaks at the lower rpm is torque and it's units are on the right. The one that peaks at higher rpm is horsepower and peaks on the left. As Norm says, yeah, they look to be about 137-ish at 5252. Mystery solved - thanks Norm! ------------------ Pete Paraska - 73 540Z - Marathon Z Project pparaska@home.com Pete's V8 Datsun 240Z Pages Quote Link to comment Share on other sites More sharing options...
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