TedB, did you ever get LSA info on the GSC 272's? Just wondering if the +1/-1 cam settings will work on the GSC's as it does for the HKS 272's.

 

My tune didn't change at all even going from 0/0 to -3/-3.

 

Guys, I may have missed the ans to this question...how do the Brian Crower 272 cams compare to the HKS and the GSC 272 cams?

 

Jeff, so basically, the cam gears allow you to practically SHIFT the powerband without requiring you to make changes to the tune?

I just need to understand if tweaking cam gears is like adding a new mod to a custom tune, where you need to make adjustments to the map when you make adjustments to a part of the hardware.

Mine is currently set to -1 deg on the intake, -2 on the exhaust, and power is copious from especially strong all the way from 5k to 6.5k.

The reason I'm asking is, given that my rev limiter is currently set to 7.8k rpm, I was wondering if adjusting the cam gears would allow me to broaden that 1.5k range.

 

I tuned my car for max midrange power. My cam gears ended up at -2/-2. I then tried other combinations -1/-4, -3/-3, +1/-1 and a few more. None of the other settings caused my AF to lean out or go rich and I didn't see any knock.

Keep in mind I have a road race tune so its not on the bleeding edge of knock like MANY other dyno queens like to have. I imagine if you tune your car to the bleeding edge then you may see a little knock if you change the setting, but who in their right mind would want something that close to "knocking".

 

My logs show that my current track and street maps have very low knocksums (using Mitsulogger and EvoScan), between 0 and 1, so that should be safe enough.

If cam gears can be used to tweak the powerband, I would like to either use them to:

1. broaden the powerband. Currently, most of the power is spread between 4000 rpm (at spool-up), all the way to 6500 rpm, and I would like to bring that up to 7000 rpm.

OR

2. if possible, bring about a greater concentration of power by compromising the breadth of the powerband, and instead focus on getting more power between 5000 rpm and 7000 rpm

If either of the above can be achieved, which of the cam gears should I adjust? I just need to know the effect of retarding each gear

- e.g. if i retard the intake cam from -1 to -3, what effect would that have on the powerband?

Likewise, what would further retardation of the exhaust cam from -2 to -4 have on the powerband?

In case anyone's wondering why i got the cam gears when I know so little about them, it's because my tuner convinced me that it would not be accurate to try to use the stock cam gears to achieve zero TDC, hence i decided not to skimp on a couple of hundred and risk damaging the engine and got the cam gears.

 

Are we assuming you are using the factory cams? If so, that leaves something to be desired, regardless of what you do. As far as damaging the engine, you shouldn't do that unless you severely mis-time the cams (e.g. advancing the intake cam too far).

In a nutshell (and I am being very basic here), the position of the intake cam has the greatest influence on the powerband with respect to rpm. Retarding the intake cam delays the onset of power and improves things on the high side. The position of the exhaust cam (with respect to the intake cam) will influence the shape of the powerband (peaky vs. broad). Retarding the exhaust cam with respect to the intake cam tends to bolster and narrow the torque peak, while advancing the exhaust cam tends to have the opposite effect.

Goal (1) is achieved by retarding both intake and exhaust cams, as much as -5/-5 or so for the factory cams.

Goal (2) is achieved by retarding the intake cam sufficiently, then retarding the exhaust cam the same, plus a further degree or two (e.g. -3/-5).

Be advised that with the mild timing of the factory cams, changing the timing to improve power at either the high or low end of the rpm range will significantly impact things on the other end.

 

I'm using HKS 272 cams with HKS 272 cam gears. Good to know I won't be killing my engine, nor should I need to make any changes to my current map.

Based on your comment for (1), I should take my current cam gear settings from -1/-2 (in/ex) to perhaps -3/-3 and work from there?

What would really help in my area would be to have a dyno shop with a proper mechanic. Right now, my tuner's garage is a half hour drive to and from the dyno shop. With dyno charts, I should be able to see where the powerband is, and adjust the cam gears from there. Is that the correct approach to cam gear tuning?

Ted and Jeff, thanks for coming in on this. I've been trying to figure out cam gear influence on powerband and peak torque for the longest time.

 

For goal (1) with HKS 272 cams, I would go to -4/-1 or -5/-2.

 

Thanks, Ted.

You're talking about -4 degrees intake, -1 degrees exhaust. You're not referring to the number of 'clicks' on the adjuster knob, right?

Also, what would it take to be able to reliably run my engine up into 8500 - 9000 rpm? Will ARP headstud do, or will I need more than that?

 

youguys have a lot of great input.. hate to chime in so late, but just got done reading this whole thread and am curious if anyone has used the 20G-9LT turbo and retarded both in/ex cams?? I have GSC 272's and they have been set to 0/0 for some time with good power, but not what I would like at the higher RPM's.. Any suggestions as to what would be a good reference point. I think I have an idea from reading (-3/-3) but wanted to know if anyone is running the new turbo and what they might be set to with most bolt on mods (IC piping,IC,larger injectors etc...) thanks in advance all..

 

Ted, my current power/torque graph looks like this



Going by your advice, what effect will going to -4 (in)/-1(ex) have on the power/torque above?

 

Going from -2/-1 to -4/-1 will increase lag time slightly, broaden the powerband but possibly make it a less torquey in the midrange, and shift everything slightly to the right.

 

Okay, I went to the garage and had them retard the intake 4 degrees, and retard the exhaust to 1 degree.

I'm assuming that each short line represents 1 degree and not to use the longer line (which I'm assuming is 5 degrees) -- these are HKS cam gears

That said, it feels like the low and mid pulls earlier. will log and post the power/torque charts from DLL later tonight

 

Okay, here are the results based on 3rd gear (mine is a 5-speed) pulls using the same map. The only difference between the two charts is switching from a -2/-1 to a -4/-1 setting.

Here's the 'before' chart, using -2/-1 (or so I'm told by the mechanic who worked on my car)



And here's the power chart also using a 3rd gear WOT run, same map, just changed cam gear settings to -4/-1



As you guys can see, hp went up from 330 hp to 361 hp (is this whp or at the engine?), but torque remained pretty much the same. No idea why torque hasn't increased, but I've got my tuner on the case, so we'll see in a couple of days if we can get more torque out of this setup.