Valve timing "experiment"

[skewbe]

I had to do my timing belt and was intrigued by lots of posts on teamswift.net regarding advancing the cam timing (not the ignition timing).

The concept is real simple (at least on a metro), I took off the cam timing gear, made a radial line 185 degrees away from the centerline of the existing slot in the direction of rotation (just eyeballed the slot center and had a kids protractor that fit in the gear), then made a hole using my cheesey drill press. since I was WAY off on the distance from the gear center I carefully elongated the hole towards the center with a dremel and chain saw sharpening stone. This only took a few minutes and I took my time (grind a little, test fit, repeat) and had a nice snug fit when I was done.

Then I put it all back together with the cam gear on 180 degrees out from where I took it off (don't forget the new timing belt), retarded the ignition and viola, 10 degrees cam advanced.

Note, I've changed so many things in so short a time (and still havent found my timing light) that this isn't much of an experiment, but I did have my best commute yet (49.3 indicated) immediately following this mod, and I was "getting on it". It took off faster and climbed hills better, no doubt in my mind.

This is not a high speed mod, as I understand it, advancing the valve timing is supposed to allow the engine to make peak torque sooner, putting more of your around town driving closer to the engines most efficient rpm. Since I'm never on the hiway, this seems to be appropriate for my situation. Your mileage may vary

Standard disclaimers apply, this info is for entertainment purposes only. This isn't for everyone and you risk really screwing up your engine if you do something wrong.

[SVOboy]

Tempts me to get an adjustable cam gear.

Any plans for testing?

[skewbe]

I don't plan on any specific testing. The anecdotal evidence on the teamswift site is all over the place, so it's an unknown quantity but the general rule of thumb is advancing cam timing yields more mid-low range torque and retarding cam timing yields more top-end horsepower. If I didn't have to take so much junk off I might be more tempted (main pulley, water pump pully, right wheel and some plastic to get to the main pulley bolts, timing belt cover).

An adjustable gear with a seperately removable top part of the timing cover would make a nice test apparatus for the die hard experimenter.

I'm happy with it as is, tromp 'n glide

[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. I have drilled several holes around my pulley and just sort of mix and match the holes and what notch I put the belt on and I can pretty much hit anything from 0-18 degrees advanced or retarded if I keep playing with it.

You need a timing light though to see what you really ended up with. Set your base timing to 0 then set the cam to whatever you are shooting for then check your timing to see how much it actually moved. Timing lights are pretty cheap if you get a basic one. The dial back to 0 ones are really nice and if you are planning a lot of work on a car they are handy to have.

I tried my car at ~ 3,5,10,15,18 and I like the way 5 feels the best and it seems to put the power right where I need it but it really depends on how you drive. One notch on the belt is 18 degrees btw. And I just take the top bolts off the timing cover and use a tie down strap to hold the cover away while I move the cam sprocket around. Takes like 30 seconds to adjust it that way. I will probably just cut the cover in half this summer and not bother with the top of the cover though.

[MetroMPG]

Originally Posted by skewbe

I'm happy with it as is, tromp 'n glide

Funny. New technique name.

Good writeup (and links).

Originally Posted by Coyote X

I just take the top bolts off the timing cover and use a tie down strap to hold the cover away while I move the cam sprocket around.

Think I'll be able to get away with doing that for the cam swap? Or will I have to take the whole cover off?

[skewbe]

A non turbo image might give a better picture. The blue line represents a couple degrees of cam advance on a honda s2000 and also represents 7hp for all RPM's below 5000


from:
http://hondaswap.com/engine-building...e-build-20867/

[SVOboy]

VTEC hates cam advance.

[Coyote X]

should be able to for the cam swap. just put the crank on 0 degrees on the timing mark before you do anything so it is easier to line the new one back up. It is an easy swap in warm weather

I never take the cover completely off unless I need to change the belt. the cover can bend far enough to get a wrench on the cam sprocket easy. It is real easy to hook a strap to it and pull it way. I hook the other end of the strap on to the wheel or anything that it will stay hooked on. I guess you don't really have to use something to tie it up out of the way but it makes it a lot easier.

[rh77]

Originally Posted by SVOboy

Tempts me to get an adjustable cam gear.

Same here -- I'm not keen on replacing the whole cam just yet, but the cam gear is another story, and intriguing.

For Hondas this is a pretty common go-fast mod, right?

So for us DOHC-ers: intake, exhaust or both gears?

I would give up top end for low RPM response any day (providing the FE gains are there).

Wondering out loud: a VTEC head swap with 2 fuel efficient cam sets. One for in-town, up to 2000-2500 RPM operation, and the second set for cruising on the highway at higher RPMs to maintain power (but would efficiency increase, hmmm...)

RH77

EDIT: BTW, love the "Tromp 'N Glide" nomenclature.

[diamondlarry]

So for us DOHC-ers: intake, exhaust or both gears?

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.

[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.

[diamondlarry]

Originally Posted by lovemysan

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.

Now you see why I was assinged the non-critical jobs. Anyway, the hardest part will probably be getting everything out of the way to get the front cover off; power-steering, A/C, top enginge mount, etc. You will also make it easier on yourself if you jack up the car and take off the right front wheel and the inner fenderwell. Then you'll have to get all of the bolts out of the cover. It seems like there were some small bolts/screws down by the oil pan that could easily be missed. Then you have to pry up a little on the front cover then out. Using air tools like we did, you could probably have the gear exposed in an hour but, the first time you do it, plan on longer. Also, make sure there are no women or small children around in case of a slip of a naughty word or two. I did quite well on that though.

[Ryland]

insted of filing your timing gear to death, or buying an adjustable timing gear, I'm pretty sure I've seen offset keyway keys, and the differnt offsets give you differnt degrees of change.

[diamondlarry]

Originally Posted by Ryland

insted of filing your timing gear to death, or buying an adjustable timing gear, I'm pretty sure I've seen offset keyway keys, and the differnt offsets give you differnt degrees of change.

The problem is going to be finding things like that for a SOHC. There isn't as much of a market for SOHC performance parts since most people are modding the DOHC.

[lovemysan]

Originally Posted by diamondlarry

The problem is going to be finding things like that for a SOHC. There isn't as much of a market for SOHC performance parts since most people are modding the DOHC.

Well what I want to do would definately not be considered a performance mod. Well its sounds like its not possible to pull the gear from the top so I won't be able to do this. I can't spend a whole day taking apart a 64,000 mile engine fiddling with critical engine components. My family already thinks I'm a nut for attaching parts and removing spoilers on a practically new car. They actually made me sign a contract stating I wouldn't modify the car when I bought it.

My nissan was just plain easy. Take the valve cover off, unbolt/slide gear off and secure chain, remove cam caps, remove cam, reassemble was reverse process. Just press the oil pressurized tensioner back in and bolt together. I did the last in around 15 minutes on a nice warm engine.

[skewbe]

Originally Posted by lovemysan

...
My nissan was just plain easy. Take the valve cover off, unbolt/slide gear off and secure chain, remove cam caps, remove cam, reassemble was reverse process. Just press the oil pressurized tensioner back in and bolt together. I did the last in around 15 minutes on a nice warm engine.

Yah, it's been my experience that my sw2 is a PITA to work on also. Though I remember one particularly nightmareish starter motor on a stanza, took like 6 hours. It was like they built the car around the starter motor or something

[diamondlarry]

Originally Posted by lovemysan

Well what I want to do would definately not be considered a performance mod. Well its sounds like its not possible to pull the gear from the top so I won't be able to do this. I can't spend a whole day taking apart a 64,000 mile engine fiddling with critical engine components. My family already thinks I'm a nut for attaching parts and removing spoilers on a practically new car. They actually made me sign a contract stating I wouldn't modify the car when I bought it.

My nissan was just plain easy. Take the valve cover off, unbolt/slide gear off and secure chain, remove cam caps, remove cam, reassemble was reverse process. Just press the oil pressurized tensioner back in and bolt together. I did the last in around 15 minutes on a nice warm engine.

I talked to Mike yesterday and he said that there is enough room to get at the gear without taking the front cover clear off. You can pry the cover out just enough to allow access to the bolt that holds the gear on. He did say that if you end up dropping the bolt that you will end up having to take it clear off anyway.