Does this prove David Vizard's 128 lsa formula ?
273,
I am not missing any point....& most others aren't either. DV claims that cams sold by cam companies are generally too wide with LSA....because the cam company wants to save the hotrodder from him/her self, so they widen the LSA. DV says the correct way to moderate the function of the cam is to reduce duration.....not widen the LSA because power will be reduced; he has dyno tests in his books.
I tend to agree with that statement.
How many dyno tests does he have to do?
Are they available to us ?
Richard Holdener did a LSA comparison on a 5.3L LS engine [ three cams, identical except for LSA ]. The tight LSA cam made more average hp everywhere & IIRC, it actually made a little more at peak hp. So modern engines also like tight LSA. Maybe someone can link it.
It's one of the dyno results the guy uses, no one is arguing with that going tighter generally makes more mid range torque that's common knowledge, the question is does the formula get you optimal lsa and does this optimal lsa gain you 40-50 lbs-ft and get you near the 1.40 lbs-ft DV claims over the 110-114 most cams are ground on? What was the gain of this eg., like 10 lbs-ft or so 108 vs 112 most would be glad to lose 10 for driveability.
Every test I have seen shows tight LSA is better. The late Joe Sherman was quoted as saying 'The tighter I went [ with LSA ], the more power I made '.
No one arguing that, like saying does more duration tend to make more hp, question is does running tighter lsa then the formula recommends are you still gaining torque? And in the eg.. The guy shows seems you will, if that is true how's the formula recommendation optimal ?
Which is the whole bases of me posting this.
Here is yet another LSA test. Long before the 128 rule was known. Three big duration cams in a 350 Chev. Isky cams identical except for LSA: 106, 108, 110.
The 110 made 3 peak hp more than the other two : 583 [110 ], 578 [ 108 ], 580 [ 106 ]. The 106 made peak HP 500 rpm earlier. Average tq through to 7000: 106 was highest, 108 was down 13, 110 was down 23. In percentage terms, the 110 was down 5% on the 106 in average tq.
Just like everyone would expect, the question isn't does tighter lsa give more torque, it's does the formula give optimal lsa and more important match the claims of being up there choosing cams like 1% of engine builders.
Much to much criticism of the 128 rule. It was created so that hot rodders didn't have to guess LSA. DV wants you to buy his software program, which gives more accurate results. 128 was a freebie...
Like said before you could probably do worse than using the formula as a guide line.
And I like the basic idea of tighter lsa less duration for same type cam as you would normally pick.
And these aren't setup as a real test, to do that 1st you'd have to run recommended cam and a bunch of cams on either side of the lsa while keeping overlap the same, maybe in that scenario we'll se the 40-50+ gains for 1% builder type torque. But what evidence I've seen so far I'm a bit doubtful, so until then I'll take it with a grain of salt.
And the main problem with his formula is picking overlap which the next main step so you can figure out duration.
