Valve timing "experiment"

[rh77]

Originally Posted by diamondlarry

Both can be adjusted but I think the intake is the more important one of the two. We cut an elongated slot in my intake gear and moved it almost imperceptively and the difference was amazing. The torque band seemed to have dropped nearly 2K rpm's. Oroginally peak torque was in the 4000-4500 range and it ended up in the 2000-2500 range with noticeable improvement as low as 1500 rpm's.

Is the Saturn 1.9L DOHC a close-clearance design where it's possible to extend a valve to the point of being hit by the piston (such as when a timing belt/chain breaks)?

As I thought about it, that's my biggest concern with experimentation of this sort, as the Honda B18B1 engine suffers from this disaster if not carefully adjusted. I'll have to peruse the "tuner" area for their applications (albeit for horsepower gain, but maybe a degree range can be determined).

DiamondLarry- Would you recommend this mod -- with the torque moved, was a solid FE increase obtained? I'm wondering if a rev-limiter would need to be installed (if someone other than myself uses the car). I'm seriously considering getting an adjustable gear (at least the intake) if it's worth it. My car has no torque on the low end, which is where I drive 99% of the time anymore.

RH77

[skewbe]

Originally Posted by SVOboy

VTEC hates cam advance.

Yah, comparative valve timing dyno graphs are hard to come by. Still the effects of the cam advance before vtec kicks in at 5krpm (and it stumbles till 5.7k) are pretty apparent, the torque kicks in like 400 rpm sooner and theres quite a bit more area under the blue line under 5k rpm.

[diamondlarry]

Originally Posted by rh77

Is the Saturn 1.9L DOHC a close-clearance design where it's possible to extend a valve to the point of being hit by the piston (such as when a timing belt/chain breaks)?

As I thought about it, that's my biggest concern with experimentation of this sort, as the Honda B18B1 engine suffers from this disaster if not carefully adjusted. I'll have to peruse the "tuner" area for their applications (albeit for horsepower gain, but maybe a degree range can be determined).

DiamondLarry- Would you recommend this mod -- with the torque moved, was a solid FE increase obtained? I'm wondering if a rev-limiter would need to be installed (if someone other than myself uses the car). I'm seriously considering getting an adjustable gear (at least the intake) if it's worth it. My car has no torque on the low end, which is where I drive 99% of the time anymore.

RH77

The Saturn engine IS an interference engine. Fortunately, we only had to move it 2-4 degrees. I would think that going farther than that you would want to make some careful measurements. As for the FE increase, I unfortunately wasn't able to drive the car before the mod. I do think that it may contribute to the fact that I can cruise through city traffic in 5th at 20 mph; occasionally I can go as low as 15 if I can properly time the lights. This can also be done with no pinging/detonation even when the car is fully loaded. Also, a DOHC Saturn is supposed to get an EPA combined of 31 and, along with my driving technique, I'm averaging close to 51.

[skewbe]

Originally Posted by Coyote X

I seem to have slightly better mileage at 5 degrees cam advance on mine but I think it is mainly based on type of driving and speed.

It may be because you have an xfi also. suprf1y was pushing the 10 degree ones for my car, so I went for it. But I read a bunch of stuff you wrote about your experiment on teamswift also, and it was inspiring. Props. Nice to have the option to reuse a perfectly good cam gear, too easy.

Originally Posted by Coyote X

You need a timing light though to see what you really ended up with.

I did find my timing light last night, but couldn't bring myself to waste gas on a tune-up warm up, so waited till this afternoon to fiddle with it. I had the good sense to made a mark on the rotor at tdcc before I started and the original distributor position was obvious, the ungrimed area where the washer used to be. It looks like I wound up at 12 degrees +- 2 degrees. I discovered there is a lot of slop in the rotor, I thought it had a busted mechanical advance till this afternoon so I kinda forgot about the rotor mark. Good enough for now.

Originally Posted by Coyote X

I tried my car at ~ 3,5,10,15,18... Takes like 30 seconds to adjust it that way.

I think I just figured this out. I was worried about getting to the tensioner bolts down low. Do you just leave the tensioner locked where it is and bolt the gear back into the pre-existing belt tension? That would be quick enough to do.

[MetroMPG]

Originally Posted by skewbe

It may be because you have an xfi also. suprf1y was pushing the 10 degree ones for my car, so I went for it.

I think you're right there. If I'm not mistaken, Mike was saying that the XFi cam is ground on a different centerline than the stock one - which would mean it's got "built-in" advance relative to stock (I think).

[bobc455]

I played with cam timing a few years ago in my V8 and had similar results.

The cam that was installed at the time required about 4 degrees of retard when I indexed it, and I added about 4 more degrees of retard on my own (8 degrees total retard). Typical highway mileage was about 14 MPG. Then I advanced the cam about 4 degrees to increase low-end torque, and on a long drive to tennessee the car goto > 19 MPG! However I lost about 8 miles per hour in the 1/4 mile so I retarded it back.

I wonder if 10 degrees of advance isn't too far.

-Bob C.

[skewbe]

If I were real serious about it I'd get an adjustable gear and some dyno time, or at least one of them accelerometer jobbies I might make some more slots eventually.

Note, I originally was guessing on the ignition timing. It was more advanced than I reconed so I turned it back to a saner position and it definately lost back some of the initial oomph that I noticed. I want my little engine to last so I'm leaving the ignition timing in the retarded position.

ah yes, 1/4 mile times, I remember thee well

[lovemysan]

Originally Posted by diamondlarry

The Saturn engine IS an interference engine. Fortunately, we only had to move it 2-4 degrees. I would think that going farther than that you would want to make some careful measurements. As for the FE increase, I unfortunately wasn't able to drive the car before the mod. I do think that it may contribute to the fact that I can cruise through city traffic in 5th at 20 mph; occasionally I can go as low as 15 if I can properly time the lights. This can also be done with no pinging/detonation even when the car is fully loaded. Also, a DOHC Saturn is supposed to get an EPA combined of 31 and, along with my driving technique, I'm averaging close to 51.

How did you shim this?

[diamondlarry]

Originally Posted by lovemysan

How did you shim this?

I don't know. Mike handled all of the important stuff while I took care of things I couldn't screw up like valve cover and gasket, spark plugs, etc.

[lovemysan]

Originally Posted by diamondlarry

I don't know. Mike handled all of the important stuff while I took care of things I couldn't screw up like valve cover and gasket, spark plugs, etc.

Crud! Your worthless!

well not really. You did send me instructions about the kill switch. Well anyways I think your supposed to use some type of shim stock and the bolt washer keep it from sliding out of the cam gear. I need to find that stuff.

Do you have anyidea how long it would take to get the cam gear off my sohc? I'm a competent mechanic and have done a cam swap on a my nissan.