Naked AV

No contradiction.

Let's say the peak, as defined by duration, is at 3000 RPM's.

If the peak is 500 HP at 3000 RPM's, but the powerband only really covers 2000 to 4000 RPM's, that would be a narrow LSA.

If the peak is 480 HP at 3000 RPM's but the powerband now covers 1500 to 4500 RPM's, that would be a 'broad' LSA.



Using the above example (the first one - narrow LSA), if you wanted to move the 2000-4000 peak, down to, let's say, 1800-3800 RPM's, you would simply advance the cam 2-3 degrees.

TWISTEDTA

Confuseing sh%$ huh? LOL

I have an A4 N i just ordered the 224/224 114 LSA and a 3000 TCI stall & im just gonna stick to it!-Hopefully im ill be happy with that set up...

MNR-0

There is no hard and fast rule with cams. I will be fitting a low teens cam at 110LSA to my A4 very soon. The same design has been fitted to many other cars and power peaks at 6200RPM then begins falling away. With a stall, its less important to have a wide LSA IMO. I want all my power to have peaked and start wasting away from 3000-6500.

Shorter LSA will peak earlier and higher but fall away quicker. Wider LSA will peak later and lower but hold on longer, representing a wider spread of torque.

SPIV

The tighter the LSA the harder it will hit in the mid range with a "peakier" power curve and it will fall way sooner after it has reached its peak. Me I prefer a tighter LSA of 110 as long as you have a gun tuner you will certainly feel it when it comes on in the mid range

Adrenaline_Z

Betting on answers from a theoretical scenario will get you no where fast.

Are you referring to HP peak, or torque peak?

Which specific engine would this cam be used for?

How about the exhaust configuration?

Typically, a tighter lobe separation (112) will shift the horsepower UP the band.

114 will peak HP earlier.

With more valve overlap, the exhaust pressure and tuning ultimately determines the
efficiency of the lobe separation.

At "low" RPM, exhaust pressure tends to be higher creating a lower scavenge,
and lesser intake draw with a bigger valve overlap (112). Once the exhaust
and intake tuning become efficient, VE increase, Torque increases, power increases.

If you were able to provide valve timing for each camshaft, I could enter the
values into DD2K and get you a graphic representation.

Having said that, DD2K is probably the worst $2.00 engine simulator you can
bank on!

Without proper engine configuration, a 112 vs. 114 in the same engine is
going to rob power in either case.

Anyone could be correct, or everyone could be wrong.

11SECDWS6

iTrader: (3)

This was my thinking too. But according to some posters in the dyno section, these LS1 engines w/ stock heads and 112 LSA cams and a good tune are making some impressive numbers. Makes you wonder how much of it is though....

Adrenaline_Z

I believe there are gains even with a mis-matched setup.

The question remains: How much more power is gained once the entire
system is tuned to the cam.

eb02z06

iTrader: (18)

Did anyone even pay attention to this? If the ICL is the same say +4 then they will peak at the same points-BUT the 112 will make more at peak.

fastbasser

iTrader: (1)

From Adrenaline Z..

"Welcome to the Internet, where everyone's a mechanic and has a 10 second car."



Ya gotta admit it,,, thats funny!! (but SOOOOOOOOOOO true)

silverTA2002

iTrader: (1)

Sorry, but this post is confusing.

When talking cams, we should be talking about peak tq, not peak hp. HP is a function of tq and rpm, so when you change the cam, you're changing TWO variables, both TQ and RPM, and they both affect HP (a third variable).

We need to just compare ONE variable - TQ. And compare that to RPM.

Plus, your example doesn't even work. If you have peak HP at 3k, your powerband couldn't extend to 4500.

Change "hp" to "tq" in your example and it could work. Then in the example, the first engine would make more peak tq, at a lower rpm, and less peak hp. The second engine would make less peak tq, at a higher rpm, and more peak HP.

Naked AV

Right, TQ is what should be in that equation for it to 'work.' I was simply spouting off what little knowledge I got from 3 months of studying (and trying to understand) camshaft duration and LSA.

However, HP is simply a function of TQ, correct?

HP = (TQ x RPM) / 5250

skewba98z28

iTrader: (14)

Got this from from jrp's sticky and the link is from ls1howto.com and I don't think jrp is going to be wrong http://www.ls1howto.com/index.php?article=23 scroll down until you see LSA

Naked AV

No, jrp is never wrong, that's why I had him help me install my cam...

silverTA2002

iTrader: (1)

Yes, the equation is correct. And, it explains why we can't just talk about peak hp.

If peak HP changes, it could be because either tq, or rpm changed. If tq changes, it's because tq changed. A little simpler to discuss. And once you know the tq curve over rpm, you know the hp.

gaga

wow this thread is nuts!!!!!


i thought that the lower the lsa the higher the rpm of peak horsepower...


how could this still be so misunderstood?????

silverTA2002

iTrader: (1)

I'm surprised there aren't more understood absolutes with cams and LSA

So far, the following seems to be generally agreed upon:

Lower LSA:
Bumpier idle
More narrow powerband
Better for manuals due to idle

Higher LSA
Smoother Idle
Broader powerband
Better for autos due to idle

However, the following seems to be argued upon still:
Which LSA has the highest peak TQ?
Which LSA has the highest peak HP?
Which one hits peak TQ at the highest RPM?
Which one hits peak HP at the highest RPM?
Which one makes the most power OVERALL (i.e. area under the tq curve)?

11SECDWS6

iTrader: (3)

Your posts sums it up nicely. But those questions can and will be argued to infinity because there is no definite answer to whether 112 or 114 peak sooner. It depends on the other specs of the cam, such as intake/exhaust duration. I think it has more to do with valve overlap than LSA. A 114 cam CAN have a lopier idle than a 112 if the valve overlap is higher than the 112. Therefore, higher rpm range, higher peak hp etc.

Here is the formula:

VO = Valve overlap
ID = Intake duration
ED = Exhaust duration
LSA = Lobe seperation

VO = [(ID + ED)/4 - LSA]*2

The higher the VO, the higher the lope, rpm range, peak hp, etc.

Racehead

Generally speaking a 114 LSA cam will peak later ( higher rpm ) than will a 112 LSA cam. Usually the only reason to choose a wider LSA, like a 114 over a 112 LSA is to give you a better idle. However, doing this also removes ( scoops OUT ) some power under the curve in order to do this. The reason why most "racing" cams are narrow LSA's ( 106-110 degrees ) is because this allows more cylinder pressure ( meaning torque ) to be created under the curve. In my experience, even though a wider LSA cam will peak at a little higher hp number and a little later ( higher rpm ) in the band, the narrower ( 112 ) cammed car will be the faster ( slightly ) car.

You should choose the rpm range you want your car to make torque in, the pick the duration to make the torque in the range that you have chosen, and forget about the LSA. That # will be whatever it will be. Most people who purposely choose a wider LSA, do so for it's better idle characteristics. This is fine, but they need to know that generally speaking they are also removing torque/hp under the curve. The car may peak a little higher, but usually the car will actually be slower than the narrower LSA cammed car will be. This is because high peak #'s don't make a fast car, high average #'s within the powerband that you'll be running in DO. This is also assuming an N/A engine of course.

bowtieman81

iTrader: (35)

Out of all this I agree with Racehead. That is the info that I used when selecting my cam, and I researched for months before deciding.

Var

iTrader: (1)

But you've just entirely changed the cam. The discussion is for identical cams with different LSA's.