Cam Selection and Timing

[Raven18940]

I'm looking to change the cams on my engine to make my car stronger passed 4000 rpms. I'm looking for info on cam selection, what more duration and lift will yield, what the downsides are. Also looking at adjusting the valve timing, but can't for the life of me find info on which way it should be adjusted to do what. I've got a DOHC engine so I can adjust intake and exhaust cams independently.

[Im2Slow]

for finding the best cams you will need to look into your existing mod list,
For example turbo cars with upgraded turbos should look into getting a cam that will suit the powerband of the turbo.

[Im2Slow]

Also with upgraded cams it would always be a good idea to get a nice set of adjustable cam gears as well,

[Raven18940]

Originally Posted by Im2Slow

for finding the best cams you will need to look into your existing mod list,
For example turbo cars with upgraded turbos should look into getting a cam that will suit the powerband of the turbo.

Unfornately there's very little info on different cams on a SAAB B235R (my engine). So I'm on my own and taking a bit of a stab in the dark. So need more theory theory than hard facts, I'll play with it and see what happens.

[yellow2000S/R]

boost cams = a lot of lift... little duration

[Action Park]

93
You're gonna want a little more duration than stock and a moderate amount of more lift. You do'nt want a cam too rampy because that'll be hard on the valvetrain. But a little more duration(get the number at .050 lift, it's better at determining a cam's performance than advertised) will provide the higher powerband you want. Also, if you can, get the cam(s) ground with a wider lobe seperation angle. Turbo cars love wide lsa's. And if you're only going to do 1 cam, do the intake. Btw, excuse me for not being more knowledgeble about your car, but do you have an upgraded turbo or anything? The cams wont reach their potential when the turbo is the choking factor. As far as cam timing goes, thats one of the things that a dyno knows best. What makes power on one car might reduce on another. One can theorize as much as possible on cam timing, but that's the truth. When in doubt, keep it simple.
93 93/93

[Raven18940]

Originally Posted by Action Park

93
You're gonna want a little more duration than stock and a moderate amount of more lift. You do'nt want a cam too rampy because that'll be hard on the valvetrain. But a little more duration(get the number at .050 lift, it's better at determining a cam's performance than advertised) will provide the higher powerband you want. Also, if you can, get the cam(s) ground with a wider lobe seperation angle. Turbo cars love wide lsa's. And if you're only going to do 1 cam, do the intake. Btw, excuse me for not being more knowledgeble about your car, but do you have an upgraded turbo or anything? The cams wont reach their potential when the turbo is the choking factor. As far as cam timing goes, thats one of the things that a dyno knows best. What makes power on one car might reduce on another. One can theorize as much as possible on cam timing, but that's the truth. When in doubt, keep it simple.
93 93/93

I don't have an upgraded turbo, but tuning my car costs so much I'm looking for cheap ways to get a little more power. I'm going to try the cams from a 9000 (model the preceded mine). 9-5 heads flow better so they got wussy cams. These cams have more lift, slightly more duration, wider lobe seperation, less overlap, and the intake cam is a bit later so it should flow better at high revs. If it works like I think it will I'll gain 15-20whp, if not then I'll just throw the stocks back in. I can get em for free so it's worth a shot.

[Action Park]

93
Awesome. You might even gain a lot of power down low with the added lift if your head promotes good velocity.
93 93/93

[Raven18940]

Originally Posted by Action Park

93
Awesome. You might even gain a lot of power down low with the added lift if your head promotes good velocity.
93 93/93

I've got the turbo and 15 psi of boost to promote good velocity.

[SuperHatch]

I can tell you what worked on my Evos...

With stock cams, going to -5/-5 significantly increased the power in the higher RPM range with a sacrifice of off-boost power and about 300RPM worse spool.

With 272's, -2/-2 helped fight detonation with no sacrifices over 0/0

I switched to +2/0 with the 272's and it helped increase response with a greatly fattened midrange, however I sacrificed peak power overall. This didn't concern me though, since I heavily autocrossed the car and I wanted the torque.

I know that retarding the cams helps top end, advancing helps the low range (to a point), tightening the LSA narrows the powerband, and widening it broadens it.

You can do combinations as well... I.E. - If you do a tighened LSA with advanced overall timing, you can get a serious punch in the low RPM range. with a sacrifice up top...