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Where do you like cam? Adv or ret

Pietercc said:
10 degrees, and I smogged my 90 with an A cam in it, so you should have no issue
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this is a new to me car that has had neglected maintenance, so I have no idea how good the cat is. If I can get away with not replacing the cat for now I'll wait.

I wonder what the Acam at 10 degrees compares with T at 4?

Ive done T at 6, and all it did was lower the top end drop off rpm by 500. So that tells me 4 degrees is dropping the power close to idle where you want for a daily.
 
240 240 said:
this is a new to me car that has had neglected maintenance, so I have no idea how good the cat is. If I can get away with not replacing the cat for now I'll wait.

I wonder what the Acam at 10 degrees compares with T at 4?

Ive done T at 6, and all it did was lower the top end drop off rpm by 500. So that tells me 4 degrees is dropping the power close to idle where you want for a daily.
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I'll mess with it soon, I'm figuring out if I want to mess with my IPD turbo cam on my 760, I'll likely throw it on my 245 in another week or so
 
The A and B both are ground on a +2 retarded centerline. I am curious how timing affects reversion at idle. Everyone says if you advance a cam it will favor the lower parts of the power band, but if you're opening an intake valve sooner as the piston is still moving up, I feel like that would hurt vacuum at idle. Maybe there's a reason the A and B (which have a narrower LSA than the T, V, K, VX, IPD T) are ground retarded. When I went M to T, I must've set the crank retarded by a tooth and I didn't notice it for almost 2 years. It didn't run too smooth (the car never really did run well, I think the M that was in there before was also off), but it still had noticeably more power above 3k than the M. It still idled better than the B, and still got 27mpg once or twice.

I think testing by the seat of the pants isn't best. My T really "woke up" above 3k but if you dyno tested it against a T timed straight up I'm sure it was worse all across the board.
 
Bear in mind that a piston's speed and motion isn't linear. Because the vertical motion is controlled by a rotational motion, the piston moves both fairly little and fairly slowly at and on both sides of TDC. If you're selecting the hierarchy of valve events relative to engine character, IVC is the king.
 
I really want to do some retardation testing with my IPT T cam. I really don't care about idle or anything under 3500 RPM. The IPT T cam seems to start falling off at 5500 RPM in my car. There has to be a way I could determine if acceleration is better through megalogviewer.
 
it might tell you something useful if you could lock out the closed loop idle air control and ignition timing compensation.
 
OVERDRIVE said:
Has any one played around with where your cam makes the most vacuum at idle?
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remember when old timey car mechanics would test their tune with a cup of water on the engine to see how little engine would shake.?




No I dont remember either, but some boomer told me they would do that
 
OVERDRIVE said:
Has any one played around with where your cam makes the most vacuum at idle?
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When i had my car on the dyno i hit the rev limiter a couple of times during pulls. This caused the adjustable cam gear to slip all the way to max cam advance. (10 cam degrees of something like that)

With this much cam advance, the T-cam was idling at a a lot of vacuum, ~28kPa iirc, i noticed something was wrong during a dyno pull when i made 440nm of torque instead of 420nm and the torque curve fell off a cliff past 3500rpm...
 
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