Cam advance

[mightymouse]

As the OHC zuk motors are not dissimilar in basic layout to the Daihatsu I was wondering if/how much cam advance is being run.

I have seen references to up to +10 degrees being cool but havn't heard any real discussion and it is a very worthwhile and easy engine mod if you can buy a ready made sprocket

[cj!]

I put one on my old 1.6 16v lwb. If I recall it ended up being advanced about 6 degrees and it certainly helped. There are a couple of things to bear in mind for those considering this mod and it is worthwhile considering. Get it dialled in on a dyno and make sure that the ignition timing is adjusted as well. Just because somebody said that they could change the cam timing by "x" amount on their engine dosen't mean the same will work for yours. I had a different profile cam in mine compared to stock and you need to consider what is happening to the valves when you change the cam timing. Different engines will have different limits and there can be different amounts of advance or retard used and results gained between 2v and 4v cylinder heads. There is also potentially more to be gained with dohc heads as you can time the cams individually.

What I do like about using adjustable cam gears is the fact that you can get quite nice gains in power/torque at a more suited rpm. Basically what you are doing is taking the existing power/torque curves and shifting them further up or down the rpm range. For example you might be developing 100Nm @ 3000rpm and 130Nm @ 4000rpm and by adjusting it you might now be developing 120Nm @ 3000rpm which is a 20% gain in torque which is more user friendly in an offroad situation. The trade off is that you lose a little further up the rev range but for our needs I think that is a compromise worth looking at. On some engines a cheap rough and ready solution is move the timing pulley by one tooth but keep in mind you have no adjustability and it may be too much for that engine due to the amount of degrees it has changed by and this is the case with the 1.6 16v but it does work for the 1.6 8v.

A source for these gears for Suzuki engines is from Adam at http://www.occracing.com/pricing.htm which is where I got mine from. It was a good quality product and cheaper and better made than I could source locally. Unfortunately these are not suited to the "J" series engine and there is also nothing available for the "H" series V6 engines. One option would be to look into offset keys for the gears or re-dowelling the sprockets but again there is no ability to make adjustments.

[mightymouse]

Thanks CJ - and a warning to the novice - if you get it wrong ( too much advance / retard ) then you can bend valves and do serious damage. That's whey general info is helpfull - it gives you approximate limits rather than guesses. Also if the cam drives the dissy - you will need to retime the engine as a cam advance advances the ignition also

An endoscipe into the bore is really the best way - a couple of mm clraerance minimum is worth achieveing.

And whilst every engine is different the trends are universal - cam advance moves the torque curve down the RPM range.

[cj!]

Also keep in mind that if you have shaved the head, the valves are now sitting even closer to the tops of the pistons.

I can't remember exactly but I think with my setup when I retarded it by about 6 deg the curve was shifted by around 500 - 600rpm. It doesn't sound like a lot but it makes a real world difference in terms of driveability as I had more power and torque sooner.

I have added a pic of the stock 1.6 16v power and torque curves. The black is the original and the red shows the power curve moved lower in the rev range by about 500rpm when then the cam timing has been advanced. You can see the blue line shows that when the engine originally made 2500rpm the engine was developing just over 40kW but with the advance added now at 2500rpm it is making over 50kW or an increase in the order of 25%. Not too bad considering the engine has had no mods apart from the cam timing adjustment.

[mightymouse]

I really wasn't referencing my discussions to racing engines, as I don't see many common factors with our 4WD engines - I think a generous safety margin in clearances etc is a good idea given the wide variance in operating conditions and desired life span differences.

By the way the figures are presented - that's the running clearance not a static clearance like I am talking about and almost certainly set up during the engine build by people with a detailed knowledge of the particular engine - and often gained at great expense ( oops too much ! ), not in our backyards or garages.

When temping others into potentially engine busting mods I prefer safety - we are off the road enough as is..........
The gains are real as CJ has proven but please don't break you engine experimenting beyond "sensible" limits.

[gwagensteve]

In fairness - Mightymouse did say "a couple of mm" which is 80 thou. 5 thou is 0.127mm which is as good as rubbing AFAIK.

Even 12 thou is only 0.3mm. If your'e cutting it that fine....

Steve.

[Phantomzook]

I put one on my old 1.6 16v lwb.

Out of curiosity did you take this off your vehicle when you got rid of it?

[cj!]

I put one on my old 1.6 16v lwb.

Out of curiosity did you take this off your vehicle when you got rid of it?

No

[cj!]

Bumped for Daryl's benefit.

I also used Ivan Tighe Cams in QLD http://www.tighecams.com.au/ to regrind my G16B cam to suit my application after supplying as much relevant info as possible and I was pleased with the outcome after it was dialled in on the dyno using the adjustable cam gear from occracing.com along with the ignition timing. I did find that there were a couple of holes in the air/fuel ratio at different rpm points so it was dialled back a bit for safetys sake. An interceptor would have resolved this and also allowed more power to be developed but the car was gone before I got the chance to do it.