The truth about LSA
04-26-2004, 08:20 AM
#21
6600 rpm clutch dump of death Administrator
Originally Posted by Lucian
thx j-rod
you are very quick at replying, in fact i thought i was double posting, yet you had already replied.
What about this??? something like a 224/224 (not sure which lift (either a .566 or a .588) and i will check on the ramp rates) on a 110 lsa..
Would this be to narrow of an lsa (in fact i dont even know where i would find this cam??
thanks alot
you are very quick at replying, in fact i thought i was double posting, yet you had already replied.
What about this??? something like a 224/224 (not sure which lift (either a .566 or a .588) and i will check on the ramp rates) on a 110 lsa..
Would this be to narrow of an lsa (in fact i dont even know where i would find this cam??
thanks alot
99-230/224-111 Thunder Racing Custom "Reverse Split" Camshaft - 230/224 .575/.563 111 LSA 2200-6800 RPM Power Band. Excellent mid-range & high RPM power. Automatic cars require computer tuning and it is recommend for optimum results on manual transmission cars . Due to the fast ramp rate of this camshaft, the use of 1.8 rockers is not recommended.
04-26-2004, 08:38 AM
#22
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Originally Posted by J-Rod
Think about this cam from TR or something similar...
99-230/224-111 Thunder Racing Custom "Reverse Split" Camshaft - 230/224 .575/.563 111 LSA 2200-6800 RPM Power Band. Excellent mid-range & high RPM power. Automatic cars require computer tuning and it is recommend for optimum results on manual transmission cars . Due to the fast ramp rate of this camshaft, the use of 1.8 rockers is not recommended.
99-230/224-111 Thunder Racing Custom "Reverse Split" Camshaft - 230/224 .575/.563 111 LSA 2200-6800 RPM Power Band. Excellent mid-range & high RPM power. Automatic cars require computer tuning and it is recommend for optimum results on manual transmission cars . Due to the fast ramp rate of this camshaft, the use of 1.8 rockers is not recommended.
04-26-2004, 08:49 AM
#24
TECH Senior Member
"Would it be better for drivability vs power to have less duration and a tighter LSA than more duration / wider LSA for a N/A setup? eg: a 234/232 106LSA with XE-R lobes vs a larger 238/240 112LSA."
The second cam would idle much better. If you made the LSA of the second cam 109.5 instead of 112 then they would idle very similarly.
I believe that Nineball, way back in '01, meant that increasing the lift (assuming the heads can support the added lift) will increase power all the way across the graph. It'll add power at all RPMs. I DO NOT think he meant that it will have a significant effect on where peak power is made. He did NOT mean that it will have an effect of the power curve such as is seen when increasing intake duration.
"Increasing lift moves the entire power curve upwards" (Upward as in on the HP axis, NOT the RPM axis.)
About LSA...
I do agree with J-rod that it should be viewed more as a resulting factor than an adjustable one in and of itself. However, I don't want anyone to misunderstand this. IMO, sometimes it's OK to change the LSA of a given cam but we should understand the effect that this will have before doing so. Of course, if we change the LSA, then we don't actually have the same cam anymore. Lemme give an example...
Let's say that I'm looking for a good street/strip cam and I narrow it down to a certain cam that makes peak power at 6000 and has an LSA of 112. Now, let's say that this cam seems to meet many, but not all, of my needs....it has an idle that is too rough for me. Let's also say this cam, in my setup, would need to be shifted at 6400 for best ETs....but I'm NOT looking to shift that low! I want the thing to turn at least 6800. Why? Maybe it's my gearing. Maybe I just loooooooove to hear an engine wind up. Whatever...point is, I want it to carry the power out higher. Ok, I can change a few different things to accomplish this. The most obvous thing to help it make power up high would be to increase the intake duration....but wait, this cam is already a little rough on the idle for my needs. NOT an option for me! Hmmm....well, I could retard the timing advance. That would help a little but I don't think it would help enough and I don't want to kill any power AT ALL just off idle because I do a good bit of parking lot driving you know. What's left? The LSA. I can widen the LSA to 115. That will smooth the idle out, it'll help power and smoothness at parking lot RPMs, it'll raise my peak power to 6200, and it'll carry the power out farther so that I can shift at 6800.
In other cases I would say that if you're looking to raise your shift RPM by widening the LSA then your cam is too small to begin with. But then there are cases like these. This was a similar case to mine when I designed the Stealth II cam. I wanted to shift at ~6700, I didn't care about a midrange power loss since I planned to run a 4000 stall and would never see this range at WOT, and above all else I wanted to have a silky smooth stock sounding idle. The cam accomplished all of this perfectly. I could have gotten the same idle from a smaller duration cam but I wouldn't have been able to turn the RPMs that I was looking for (nor would I have made as much power.)
Now, in RACING, where power is the ONLY thing that matters, throw LSA considerations out the window! It is indeed only a result of the valve timing events.
The second cam would idle much better. If you made the LSA of the second cam 109.5 instead of 112 then they would idle very similarly.
I believe that Nineball, way back in '01, meant that increasing the lift (assuming the heads can support the added lift) will increase power all the way across the graph. It'll add power at all RPMs. I DO NOT think he meant that it will have a significant effect on where peak power is made. He did NOT mean that it will have an effect of the power curve such as is seen when increasing intake duration.
"Increasing lift moves the entire power curve upwards" (Upward as in on the HP axis, NOT the RPM axis.)
About LSA...
I do agree with J-rod that it should be viewed more as a resulting factor than an adjustable one in and of itself. However, I don't want anyone to misunderstand this. IMO, sometimes it's OK to change the LSA of a given cam but we should understand the effect that this will have before doing so. Of course, if we change the LSA, then we don't actually have the same cam anymore. Lemme give an example...
Let's say that I'm looking for a good street/strip cam and I narrow it down to a certain cam that makes peak power at 6000 and has an LSA of 112. Now, let's say that this cam seems to meet many, but not all, of my needs....it has an idle that is too rough for me. Let's also say this cam, in my setup, would need to be shifted at 6400 for best ETs....but I'm NOT looking to shift that low! I want the thing to turn at least 6800. Why? Maybe it's my gearing. Maybe I just loooooooove to hear an engine wind up. Whatever...point is, I want it to carry the power out higher. Ok, I can change a few different things to accomplish this. The most obvous thing to help it make power up high would be to increase the intake duration....but wait, this cam is already a little rough on the idle for my needs. NOT an option for me! Hmmm....well, I could retard the timing advance. That would help a little but I don't think it would help enough and I don't want to kill any power AT ALL just off idle because I do a good bit of parking lot driving you know. What's left? The LSA. I can widen the LSA to 115. That will smooth the idle out, it'll help power and smoothness at parking lot RPMs, it'll raise my peak power to 6200, and it'll carry the power out farther so that I can shift at 6800.
In other cases I would say that if you're looking to raise your shift RPM by widening the LSA then your cam is too small to begin with. But then there are cases like these. This was a similar case to mine when I designed the Stealth II cam. I wanted to shift at ~6700, I didn't care about a midrange power loss since I planned to run a 4000 stall and would never see this range at WOT, and above all else I wanted to have a silky smooth stock sounding idle. The cam accomplished all of this perfectly. I could have gotten the same idle from a smaller duration cam but I wouldn't have been able to turn the RPMs that I was looking for (nor would I have made as much power.)
Now, in RACING, where power is the ONLY thing that matters, throw LSA considerations out the window! It is indeed only a result of the valve timing events.
04-26-2004, 03:59 PM
#25
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Guys please correct me if i'm wrong, but I always thought that a 112 LSA cam will peak at a higher rpm and that a 114 LSA cam will peak a little lower but have a broader range of powerband.
Take for example the ASA cars, they run a 110 LSA because they have all of their power in the upper rpms for the track racing.
I know that a 114 LSA or higher will have a smoother idle than a low LSA, but with the smoother idle, you also get a broader powerband, but leave a little bit of power on the table.
Take for example the ASA cars, they run a 110 LSA because they have all of their power in the upper rpms for the track racing.
I know that a 114 LSA or higher will have a smoother idle than a low LSA, but with the smoother idle, you also get a broader powerband, but leave a little bit of power on the table.
04-26-2004, 04:06 PM
#26
TECH Senior Member
A 112 should peak just a smidge lower than a 114 and the power will fall off slightly quicker. It will make slightly better power before the HP peak, however. In this way, yes, it will give a slightly broader power range...it's just that more of that power will be before the HP and less of it afterwards. Make sense?
04-26-2004, 04:06 PM
#27
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The real truth of the matter is camshafts are the brain of your engine. Unless you are a real professional, or an amateur with an engineering/physics background with an AMAZING amount of experience, you will never be able to correctly design a camshaft. You may be able to get a half-assed camshaft that functions, but it will never be very good.
What you need to know is the basics of camshaft function and design. You need to know enough to pick a good designer and notice BS when you have to. It is an incredibly specialized field.
If you really want to know more, you're going to have to find a mentor.
What you need to know is the basics of camshaft function and design. You need to know enough to pick a good designer and notice BS when you have to. It is an incredibly specialized field.
If you really want to know more, you're going to have to find a mentor.
04-26-2004, 04:11 PM
#28
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Originally Posted by Colonel
A 112 should peak just a smidge lower than a 114 and the power will fall off slightly quicker. It will make slightly better power before the HP peak, however. In this way, yes, it will give a slightly broader power range...it's just that more of that power will be before the HP and less of it afterwards. Make sense?
I understand now, thanks
10-18-2005, 12:28 PM
#32
Tony lets keep this one going.....
JRod could probably get together a few popular cams (I mean a few here boss not the whole selection) and put out duration, lift, LSA and Overlap numbers for a comparison and we could go from there.
Overlap area does effect idle but it also effects the power... as much as the chassis dyno wants to say that a 112 and a 114 LSA cam are the same, a 108 and a 112 cam aren't going to be the same at all.
Bret
JRod could probably get together a few popular cams (I mean a few here boss not the whole selection) and put out duration, lift, LSA and Overlap numbers for a comparison and we could go from there.
Overlap area does effect idle but it also effects the power... as much as the chassis dyno wants to say that a 112 and a 114 LSA cam are the same, a 108 and a 112 cam aren't going to be the same at all.
Bret
10-18-2005, 05:07 PM
#36
Take the popular cams from the usual suspects..... T-Rex, F13, LGX whatever.... along with some of the smaller ones. Don't really need a F13 and a F14, but something in the mid 220's range is a good comparison to make. IMHO 2° of duration on identical lobes isin't going to show up on a chassis dyno anyways so lets not nit pick here.
Bret
Bret
10-18-2005, 05:21 PM
#37
LS1Tech Co-Founder
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Originally Posted by SStrokerAce
Actually LSA is a by-product and shopping by LSA is a bad thing to do, now doing it by overlap that's a better idea.
Bret
Bret
10-18-2005, 08:58 PM
#39
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I would like to see the TR224 and the F13, because I have no idea what the advertised duration and overlap is for these cams. People are recommending the F13 to me, but the powerband of 2500 to 6800 seems to high for the street. I also would like to understand the Hotcam with it's 59 deg. overlap. How does overlap relate to duration and the powerband of a cam?
10-18-2005, 09:31 PM
#40
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I would like to see some of the whopper cams on the list too. HPE's S-Cam, some of Rapid's 'Dominator' cams, Futral's Ron Jeremy (my personal hero) cam, and LG's G5XWhatevercamtheyjustputout.