I'm fairly sure I'm clear on something.
Cams for turbos are made so both intake and exhaust valves are open at the same time.
Cams for superchargers are the same, but the exhaust valves are open less.
The stock L61 cams are good for just about everything it seems.
Assuming there's a change in the stock L61 cams and Supercharger cams, what is the drivability like outside of boost with Supercharger cams?
Being that it's a Daily Driver, I don't want to spend 70% of my driving in boost.
Point of post: Would Supercharger cams in an L61 yield less power at the same rpm and throttle position as the stock ones?
Do they 'come alive' in boost and keep out of boost driving the same?
I tought boost cams tried to avoid valves overlap. If the intake and exhaust valves are opened at the same time, you'll have a boost leak and freak out when the AF ratio goes lean. N/A cams have more overlap to scavenge the cylinder.
Gilles
2.3 Ho
^ You're right. I copied and pasted this post from another forum and forgot to correct my mistake.
Mfk-223 wrote:I tought boost cams tried to avoid valves overlap. If the intake and exhaust valves are opened at the same time, you'll have a boost leak and freak out when the AF ratio goes lean. N/A cams have more overlap to scavenge the cylinder.
Not quite, but you're right on the less overlap part. You don't have a 'boost leak', you have reversion (with a turbo). Basically, the pressure inside the exhaust manifold is greater than in the intake manifold and you have a giant EGR valve. If you have a giant turbine and high boost (or a supercharger), you could potentially have more intake presssure than exhaust pressure at higher rpm with an open wastegate, causing fresh air/fuel to go right through the cylinder without combustion, which doesn't necessarily hurt anything as far as I could imagine.
However, 'turbo', 'boost' and 'nitrous' cams are highly debated, and not necessarily what they say they are. IMO, buy the cams that give you the powerband you want for your motor, without putting consideration towards any above-ambient pressures. If you want a quick spooling turbo, you'd want less overlap, but having more overlap wouldn't make sense anyway because the turbo won't be efficient at higher rpm...and vice-versa. I'd be surprised if GM even used a different profile in the SC and NA motors.
fortune cookie say:
better a delay than a disaster.
Its general knowledge that you dont want a lot of overlap with cams being designed for a boosted application. Basically, the reason it is bad is, at high rpms, the air movement into the cylinder with be under greater pressure, and most of the incoming intake/fuel charge will scavange itself right out the exhaust valve, not only causing a blowtorch in the exhuast system but creating a situation where your loosing a lot of the initial charge of air that is being rushed in when the intake valve opens, so now you got to rely on the vaccum of the piston moving down the cylinder and the force from the boosted aplication to move the intake charge into the cylinder. High rpm/high boost situations...make comprimises, long duration and widen out the Lobe Separation Angle. Not the best of both worlds...but liek I said...cam design is all about making comprimises.
this book tells all, get it.
THE BOOK
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
Quote:
However, 'turbo', 'boost' and 'nitrous' cams are highly debated, and not necessarily what they say they are. IMO, buy the cams that give you the powerband you want for your motor, without putting consideration towards any above-ambient pressures
i agree.
turbo cams have less overlap. most turbo cam grindes are based on your powerband. stock cams are good for most turbo cars. but say on an eco. stock cams strart to dip off around 6k rpms. the turbo grind for them has a power band till around 7k.
http://www.myspace.com/15102113
So someone post a link to good Supercharger cams for the ECO for him....... I dont know any or i would!
Are the cams in the LSJ motor different than the L61?
Can you swap them? If so, would they be better? I don't really know that motor too well but seems it would come with different cams? Kind of like the secret cams from the Quad 4 to the 2.4 engine? Could be way off here as I've said, don't know much about that motor (LSJ).
I've thought of cams as well but really only looked at Patriot Performance for their stage I head and cams package. Most cams I've seen on here throw codes but the stage I head and cam package has not to my knowledge?
I know some have ran the Stage 2s from Patriot Performance and they threw codes.
Eh...old man with a Corvette now...it was bound to happen sooner rather than later right?
I'm pretty sure the LSJ head is different so LSJ cams wouldn't work on the L61 bottom end.
I know where to find cams, I was just asking about drivability outsid of boost.
OHV notec wrote:As for LSJ cam swaps:
The L61 cams can interchange with LSJ cams, both intake and exhaust. These cams are the exact same profile, only at different timings. The L61 timings are 116 intake, -103 exhaust. The LSJ timings are 100 intake, -115 exhaust.
http://www.gm.com/company/gmtunersource/downloads/ECOtec_CAMSHAFT_%20INFO_SHEET.pdf
So would they improve or hurt? I'm a newb when it comes to camshafts!
Eh...old man with a Corvette now...it was bound to happen sooner rather than later right?
