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Re: What is the largest LSA you ever saw on a Mech roll
[Re: 602heavy]
#548923
12/09/09 09:36 AM
12/09/09 09:36 AM
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Joined: Dec 2005
Posts: 293
Kansas City Metro
mbogina
enthusiast
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enthusiast
Joined: Dec 2005
Posts: 293
Kansas City Metro
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I concur with 602heavy on this, but to beat it down just a little more....using Leon's example that his 118 LSA ran better than the 115 LSA, Leon stated that he kept the durations the same. Examining what happened to the valve events by doing so, and assuming that both were degreed in similarly, with the 118 LSA, the IVO is delayed 3*, the IVC delayed 3*, the EVC delayed 3*, the EXO closes 3* later, the overlap is reduced by 6*, so what appears to be a simple change is actually a completely different cam with unpredictable results- he delayed opening the intake valve, closed it later, opened the exhaust later and held it open later, plus reduced the overlap by a large amount- the question arises- which valve events helped the motor, which hurt the motor, could he have increased power even more by changing only 2 of the events instead of 5? How about 3 events? When I am testing SS camshafts, we only change 1 event at a time, so we can truly see the result of that change. For example, if we had a cam that was 280-280-108, installed at 104, we have timing events of IVO36 IVC64 EVC28 EVO 72, overlap 64. If we wanted to determine whether the motor combo would respond the closing the intake valve 4* sooner, this would require a cam that is 276-280-107, which sounds completely different, but has events that are IVO36 IVC60 EVC28 EVO72, overlap 64, so the only change was the intake closing point, allowing more time for the cylinder to compression the mixture.
Be a Rebel- Break the Laws of Physics!
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: S/ST 3040]
#548925
12/09/09 10:11 AM
12/09/09 10:11 AM
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Joined: Dec 2005
Posts: 293
Kansas City Metro
mbogina
enthusiast
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enthusiast
Joined: Dec 2005
Posts: 293
Kansas City Metro
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Sorry to keep beating this, but my point is that the motor ONLY knows the events, IVO, IVC, EVC, EVO, overlap, the numbers used for duration and LSA are just the tools and method to get to the events. Yes, by moving the intake closing point I reduced the duration, but the motor doesn't care what the duration is, only when I opened and closed the valve. The intake opening point determines how soon before TDC the flow starts, the intake closing point determines how long you left the valve open for cylinder filling and how long the piston has to compress the mixture. The exhaust closing determines the length of the overlap period, which cleans the cylinder of residual gasses and readies it for a new charge, the exhaust opening point determines when the blowdown of the cylinder starts to push the exhaust gasses out the exhaust port.
Be a Rebel- Break the Laws of Physics!
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: RAT PATROL]
#548929
12/09/09 12:10 PM
12/09/09 12:10 PM
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Joined: Oct 2004
Posts: 1,752
detroit area
moderncylinder
top fuel
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top fuel
Joined: Oct 2004
Posts: 1,752
detroit area
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mr rat patrol,, for you your engine probably wanted the intake valve open longer/later so it didnt like to be advanced. most of the time the intake closing is the "trump" event.
the guy who started this post said earlier,, he wanted to "hit his turbo" harder,, therefore he wanted a wide lobe sep,, when really what he would want is an early exh open, then there is more pressure in the cylinder when the valve is opened therefore charging the turbo with more pressure, but if you do not have enough cylinder pressure to combust fuel effeciently in a short period of time you will loose power in doing so,, but im not a turbo guy..
really all lobe sep does is give you the distance between peak lifts from intake to exh
overlap should be measured at .020 tappet lift for solid rollers,, thats why my example above had an earlier int opening, that the exh closing,, usually its a 2 degree stagger to make up for the difference in ramp rate between them,, exh being slower than the intake. there can be exceptions to this, but its withiin a degree or two dependning on flow characteristics at overlap, port areas, valve sizes...
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: moderncylinder]
#548930
12/09/09 12:55 PM
12/09/09 12:55 PM
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Joined: Aug 2005
Posts: 760
Southington Ct.
turbobitt
OP
super stock
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OP
super stock
Joined: Aug 2005
Posts: 760
Southington Ct.
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Quote:
mr rat patrol,, for you your engine probably wanted the intake valve open longer/later so it didnt like to be advanced. most of the time the intake closing is the "trump" event.
the guy who started this post said earlier,, he wanted to "hit his turbo" harder,, therefore he wanted a wide lobe sep,, when really what he would want is an early exh open, then there is more pressure in the cylinder when the valve is opened therefore charging the turbo with more pressure, but if you do not have enough cylinder pressure to combust fuel effeciently in a short period of time you will loose power in doing so,, but im not a turbo guy..
really all lobe sep does is give you the distance between peak lifts from intake to exh
overlap should be measured at .020 tappet lift for solid rollers,, thats why my example above had an earlier int opening, that the exh closing,, usually its a 2 degree stagger to make up for the difference in ramp rate between them,, exh being slower than the intake. there can be exceptions to this, but its withiin a degree or two dependning on flow characteristics at overlap, port areas, valve sizes...
My thought in regards to the turbo question is to close the exhaust valve at a given point to reduce reversion. This point is probably the most critical point in the cam. Everything else seems like it would be driven from here. To keep overlap at a minimum(at a given duration), I would theorize that the LSA would need to be determined next. Then the intake event timing would be a result of the Exhaust timing and LSA.
I'm just thinking out load and of course related to Turbo cams.
This is good discussion, Keep it going.
Allan G.
1970 Challenger w/572 Hemi street car and my pride and joy.
1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno.
1976 Cee Bee Avenger Jet Boat - 460 Ford powered.
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: Locomotion]
#548932
12/09/09 02:35 PM
12/09/09 02:35 PM
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Joined: Dec 2006
Posts: 1,178
Indy
FlyFish
super stock
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super stock
Joined: Dec 2006
Posts: 1,178
Indy
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Quote:
Quote:
Sidebar - why do people like to put a period in front of the duration number? i.e. .286 duration. This started about ten years ago in magazines and it's plain wrong in my book. What, just over 1/4 degree of duration? I'd like to see that cam lobe. It would look like a stick on a round bar. 
lol
Since there isn't a "degree" key on the keyboard, I like to use the "asterick". I.E.: 263* @ .050"
Hold down Alt and press 0176, then release...it should give you the degree symbol °. ...and back to the topic at hand!
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: S/ST 3040]
#548934
12/09/09 02:57 PM
12/09/09 02:57 PM
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Joined: Jan 2003
Posts: 3,504
DFW
mr_340
master
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master
Joined: Jan 2003
Posts: 3,504
DFW
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I use ALt+248 on a keyboard with a keypad. I can't make it work using the number keys at the top of the keyboard. I made a MS-Word document with some symbols I use frequently in engineering (we use Greek symbols a lot). See attachment.
Floyd Lippencott IV
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Re: What is the largest LSA you ever saw on a Mech roller
[Re: turbobitt]
#548936
12/09/09 03:25 PM
12/09/09 03:25 PM
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Joined: Jan 2003
Posts: 2,923
A shed in England
Tig
master
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master
Joined: Jan 2003
Posts: 2,923
A shed in England
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About 80ft  (7000rpm SB Chebbie that probably went 8000rpm, York Dragway may '95)
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: RAT PATROL]
#548937
12/09/09 04:02 PM
12/09/09 04:02 PM
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Joined: Dec 2008
Posts: 1,200
UK
602heavy
pro stock
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pro stock
Joined: Dec 2008
Posts: 1,200
UK
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Quote:
I'm not sure what it all means either, but I did try advancing my cam 4 and the results were 60'=same, MPH=slowed 2.5, ET= slowed .2 The big Hemi didn't like it at all so I put it back where it was 298 duration 108 LSA @ 111 centerline. 
If solid maybe tighten the lash & see if it picks up , going by you're results maybe the motor wants a larger cam , or maybe you just messed up optimum valve events.  
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: 602heavy]
#548938
12/09/09 05:05 PM
12/09/09 05:05 PM
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Joined: Dec 2005
Posts: 293
Kansas City Metro
mbogina
enthusiast
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enthusiast
Joined: Dec 2005
Posts: 293
Kansas City Metro
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It makes sense. I guess I'll have to start looking at camshafts in a different
way. Too bad I don't have 30 cams and a dyno to know what it all means.
This brings to mind a NASCAR story. Supposedly Roush was testing NASCAR cams, when asked what they were testing- the reply was "all of them". they supposedly tested all combos of the valve events within a certain range of duration and LSA, in 1 degree increments. The story goes that they had several 55 gallon barrells of cams. Of course, Roush also has over 20 dyno's, so I guess they were busy for awhile.
Be a Rebel- Break the Laws of Physics!
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: maximum entropy]
#548939
12/09/09 05:21 PM
12/09/09 05:21 PM
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Joined: Oct 2004
Posts: 1,379
Airdrie, AB
Mills
pro stock
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pro stock
Joined: Oct 2004
Posts: 1,379
Airdrie, AB
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Quote:
Quote:
Too much overlap leads to reversion, lazy throttle response, low dynamic compression, poor idle. Too little overlap sacrifices mid range torque and increases the sensitivity to detonation.
more overlap can improve throttle response, and increases dynamic compression if the overlap increase was realized by way of lsa reduction. the old man always (always) told me, " it's all about when the intake valve closes." lsa increase will flatten the power band and reduce dynamic c/r, lowering cylinder pressure, and making the engine more resistant to detonation (in an appropriate combination).
He had the Overlap info incorrect. A tight LSA will have a higher cranking compression
1967 Satellite, CNC Eddy Headed 500ci Street Mauler
(Dyno'ed @ 600 HP / 650 ft-lbs)
2016 Challenger Hellcat - Holy Hell
2012 Hemi Ram Sport Crew Cab
2011 Avenger, Pentastar V-6
2007 SRT-8 Charger (Dyno'ed @ 470 RWHP)
1986 Caravelle, 318, aka "Rosco", Back Road Burner!
ALL Black...Bad Boys always wear Black!
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: Mills]
#548940
12/09/09 06:23 PM
12/09/09 06:23 PM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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The engine Absolutely sees the results of LSA, because that moves around the Valve Events. Its been tested over and over and well documented over the last 50 years. LSA can be used to Tailor your valve events. But LSA works hand in hand with duration and overlap. As the duration increases so does overlap, that can be adjusted by Picking a Different LSA. Leons Example just showed a example of what LSA Changes can do. Ive Tested it my self, With the same duration LSA changes makes a Difference that You and Your engine will notice. Knowledge learned from history shouldnt have to be relearned over and over again. But if needs to,  Its fine. mike 
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: Sport440]
#548941
12/09/09 06:50 PM
12/09/09 06:50 PM
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Joined: Oct 2004
Posts: 1,752
detroit area
moderncylinder
top fuel
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top fuel
Joined: Oct 2004
Posts: 1,752
detroit area
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no knowledge that needs to be relearned here....mills said above that a tight lsa cam will have higher cranking comp,, thats not true in all cases,,, closing the intake valev earlier will make more pressure...
when "smart" people pick cams they look where they want the four events to occur,,, then figure the durations and seperation from there,, not think they will run it high or low and determine a lsa befroe they even think of the actual events... thats all me and i think mike were saying
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