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Effects of changing cam timing, with dyno graphs

gross polluter

gross polluter

They see me trollin'
Joined
Dec 10, 2008
Location
DM12
I've recently purchased an RSI cam gear and figured I do some dyno pulls this evening to document the effects of changing cam timing. This should give a rough idea of what happens when you change cam timing. Different cams will have different results. Once I install my B cam I'll do a similar test to observe if the changes are vastly different between cam profiles.

The setup:
300k mile B230F
Auto trans
D camshaft
RSI Adjustable cam gear

I did a baseline pull with the cam straight up then proceeded to do a pull at 2, 4, and 6 degrees each side of zero. My injector timing got a little grumpy at higher RPMs so I ended the runs at 5200 rpm. Even stopping short, this should give you a good idea what's going on.

Here was the result of advancing the cam:
adv.jpg


I marked two of the lines with a pen to distinguish some of the lines as they're close in color.
The most pronounced changes are after 4500 rpm.

Then the results of retarding the cam:
ret.jpg


I found this to be the most interesting. The power takes a HUGE dive each time I retarded the cam timing. I was so baffled that I did multiple runs with each cam setting to make sure the run was consistent. Each run produced the same result.

Next week I'll be installing a B cam and I'll try the same test to see if the results are similar or different between differing cam grinds. Stay tuned.
 
scottyd said:
It looks like the D cam likes to be run straight up.
Click to expand...

conclusion: Swedish designer did an excellent job.

I guess the power dive is similar to what happens when the belt skips a tooth.

cool graphs! thanks for posting.
 
i find it very surprising that the torque peak and power peak don't appear to shift around that much (left to right), but the actual peak power and torque (up and down) do
 
You're missing out on some good information in those charts without having the data below 2500rpm and above 5250rpm(except the 6? advanced where you actually do see the HP peak at 5000rpm). That being said, you are still showing us what happens and we can guess what the result higher rpm result will be based on what's provided. In my experience, and I think yours as well, there's a noticeable change in performance off idle with the cam timing advanced for the better(more torque). I am surprised by how the torque actually goes down with you advancing the cam timing, as my experiences have shown that the torque curve at lower rpm noticeably is increased in every cam I've advanced(I haven't played with the D cam timing, though!).

You don't want to go from the D to the B cam unless you are searching for less power and/or more low end.

What do you mean injector timing? Looking at your sig I guess you mean in MegaSquirt... You sure are cutting off a lot of the info by not taking it up to 6k, lol. Did you do the lock it into 3rd gear thing?

Here's one of my cam timing adjustment charts from before the manual transmission and any head work. I should have one comparing my K straight up to a couple of different advanced settings but I don't see it. I may fire up the laptop to dig it up.

RSI+cam_+mike_s+chips+and+3+deg_+ign_+adv_.jpg


The rest of my posted charts:
http://www.ovtuners.org/gallery2/v/members/klr142_001/MY244/dynocharts/?g2_page=1
 
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gross polluter said:
Which would be?
Click to expand...
Meh, I doubt with any setup the cam retarded will make more power(, unless you are strictly looking at above 5500rpm and above(unless an aftermarket camshaft with a different "centerline" per say, or the super mild M and T camshafts). That being said, no cam is going to make peak HP above between 5500-6000rpm on a b230F with the stock intake(and potentially exhaust) manifold with a wide powerband and the most power under the curve.

NOTE: I am referring to use on a non-turbo engine, I have not played around with turbo engine camshaft timing.
 
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klr142 said:
Meh, I doubt with any setup the cam retarded will make more power, unless you are strictly looking at above 5500rpm and above. That being said, no cam is going to make peak power above ~5500-6000rpm on a b230F with the stock or near stock exhaust manifold(intake probably related as well) in my experience. At least not with the best powerband and most power under the curve.
Click to expand...

Precisely the point I was trying to make with that question. I did this to provide a general idea what happens when you adjust cam timing on a B230F, since the question seems to get asked often enough.

Any modification performed that affects power band will obviously have different effects at certain cam angles, however, there isn't one modification that's ABSOLUTELY required to see the effects of changing cam timing. Sure, certain modifications will be affected greater by a change in cam timing but I'd be willing to bet that those changes are relative to the changes observed in these graphs.

Different motors will act differently, but these graphs and the graphs I'll soon post up should give a general idea what happens with these particular engines when cam timing is changed.

We'll see what happens when the B cam goes in and I perform the same test.


What do you mean injector timing? Looking at your sig I guess you mean in MegaSquirt... You sure are cutting off a lot of the info by not taking it up to 6k, lol. Did you do the lock it into 3rd gear thing?
Click to expand...

I'm running sequential injection which also allows me to time the injection events. My injector timing map does not precisely match the configuration I had at dyno time. Basically my injection event did not end before valve closing at higher rpms so the engine would run lean and break up. At the time it would not rev beyond ~5500.
 
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Interesting results. I'm not seeing any "shift" in the power band that would be worth the 5 minutes it takes to change the cam timing. I did not expect that. You seem to have some good access to a dyno. Any chance you'll be able to snag a member with a turbocharged car and do some tests of a more common setup? The D and B cams are pretty rare and not many people on here are running NA.
 
If someone with a turbo car and an adjustable gear wants to perform the same test, I'd be more than happy to do so on our dyno. I doubt the results would differ from the results posted in this thread thus far. KLR's dyno sheet pretty much backs mine up in the fact that the power goes up and down with cam timing change, not left and right as everyone thinks it would.
 
I wish I had sequential fuel injection... Very nice! I don't want to have to adjust it though, I just want it to work perfectly, haha.
varg said:
Interesting results. I'm not seeing any "shift" in the power band that would be worth the 5 minutes it takes to change the cam timing. I did not expect that. You seem to have some good access to a dyno. Any chance you'll be able to snag a member with a turbocharged car and do some tests of a more common setup? The D and B cams are pretty rare and not many people on here are running NA.
Click to expand...
I adjust my cam timing at least once a month! Then again, I'm using larger cams than mentioned here, and I use my car for different things at different times. When I'm going for gas mileage or strictly around town without the urge to have fun above 5500rpm, I'll typically run ~4 deg. advanced. When advancing the cam I don't pick up peak power(typically), but I can increase my peak torque as well as drivability and intake vacuum at low rpm.

Before doing the headwork, manual swap and what not, I would run ~2 deg advanced on the stock cams(A/B/IPD Turbo/D, etc.) almost all the time for a good all around setup. For maximum fun I'd run straight up.

gross polluter said:
KLR's dyno sheet pretty much backs mine up in the fact that the power goes up and down with cam timing change, not left and right as everyone thinks it would.
Click to expand...
Well, the band does shift left and right... But the higher rpm power peaks are definitely more effected. It's not always easily visible with the automatic car(but it IS felt) because you can't see what's happening at really low rpm. With my ENEM K13 I can go from ~9-11" of vacuum at idle when warmed up(horrible) to ~12-14" with it advanced 4+ degrees. That makes a large difference in torque at and off idle where a lot of daily driving happens but it isn't something that's shown on most of the dyno charts because a dyno pull usually starts at higher rpm. This advance is at the expense of power at high rpm, so it DOES shift the power band left when advancing the cam in my experiences.

If I'm driving the car around the street or going for gas mileage and low end power, I will definitely advance the cam at least 2 degrees(even in a stock configuration). Past 4 degrees of advance I usually see too much power diminished up top for me to enjoy it, because I like to rev. Different amounts of head shaving and headgasket thicknesses will cause the preffered advance amounts to vary. Even so, on my car with an .040" gasket and .040" off the head, I am currently running "straight up" for maximum fun and reduced detonation. I will be advancing it 2 degrees when I go out to the garage this morning, lol.

I'll see if I can make two other charts showing mostly just cam timing adjustments.
 
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What did you do for a cam sensor for sequential? I would like to try to run COP sequential on my 16vt with Haltech E6X.
 
Back when I dynoed my intake manifold swap (stock vs sheetmetal) We adjusted my ipd cam advance and retarted. We acutally found more tourque down low and more upper HP with the cam retared. This was at 4 degrees on my 180K all stock with a 13c/15g hybrid, stock exhaust, 15psi, with ipd cam gear and aw71 tranny.
 
klr142 said:
Meh, I doubt with any setup the cam retarded will make more power, unless you are strictly looking at above 5500rpm and above. That being said, no cam is going to make peak power above ~5500-6000rpm on a b230F with the stock or near stock exhaust manifold(intake probably related as well) in my experience. At least not with the best powerband and most power under the curve.
Click to expand...

I had more low-down torque and more high-end power with 2.5* Retarded!
The difference to 2.5*Adv was VERY obvious.
Exactly as Nathaninwa reports.

To original poster, great stuff!
I'll be interested to see the B cam results as previously I ran both the B and D cams.
At present I run the IPD turbo cam, and have to say, I didn't find it any better than the B or D cams on my set-up.
 
Maybe this suggests theres alot of advance ground into the cams already.
 
Who knows, it definitely disagrees with anything I've experienced... Maybe the IPD cam gear is off?

EDIT: Or, maybe it's different with turbocharged engines, I've only played with non-turbo applications.
 
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