Cam timing.

[snaponbob]

Anyone tried tweaking the exhaust cam position (advance/retard) to change torque curve or power delivery?

[Mklock]

I'm pretty sure theres nothing to gain for stock cams but, I have seen a few threads where they have degreed after market cams. They do that so they can run full vanos travel which helps out quite a bit.

[jakermac]

My piston guy had me measure my cams (Metric Mechanic Rally cams) accurately for him. Then based on the build specs and the intended use of the car (autocross) he suggested that I install the exhaust straight up and the intake 6 degrees advanced. I dyno'd the car in June and the power dropped off a little sooner than I'd hoped. I asked him about retarding the intake to make the power carry a bit later in the rev range and he said leave the intake cam where it is and retard the exhaust cam 3-4 degrees.

I trust him, but I'm trying to wrap my head around how retarding the exhaust cam will make the power carry later in the revs. Is this increasing the overlap to promote better scavenging?

http://i392.photobucket.com/albums/pp10/jakermacdorey/FullSizeRender_zpsvugh7bdg.jpg (http://s392.photobucket.com/user/jakermacdorey/media/FullSizeRender_zpsvugh7bdg.jpg.html)

[snaponbob]

THanks for sharing. Without a "before" graph, one can't see the difference. That said, what else has been done to that engine?? That is not just CAMS on a M50B25 !!!! And, yes, scavenging as well as the burning charge stays in the engine a bit longer.

[jakermac]

The motor has many enhancements:

Imagineering 84.5mm 11.5:1 pistons (Paul Burke)
S52 lightweight crank
Lightweight Molnar rods
Mild port job
+1mm intake and exhaust valves
Metric Mechanic Rally cams
3.5" MAF/intake/filter
M50 manifold
RaceLand shorty headers and full single 3" exhaust
UUC 8.5lb flywheel
RK Tunes email tune with a couple small adjustments
All in an M52B28 single Vanos aluminum block from a 97 Z3 2.8

Wouldn't enhanced scavenging be the total opposite of the burning charge staying in the engine longer?

[snaponbob]

Don't know. That is why I asked.

[jakermac]

I did a bit of searching and found this which tells me what Paul Burke is suggesting is to increase overlap to improve scavenging:

http://www.hamotorsports.com/cam-gear-tuning.html

Now I'm trying to wrap my head around why he does not want me to retard the intake cam.

[snaponbob]

I did a bit of searching and found this which tells me what Paul Burke is suggesting is to increase overlap to improve scavenging:

http://www.hamotorsports.com/cam-gear-tuning.html

Now I'm trying to wrap my head around why he does not want me to retard the intake cam.

Good link. I wonder what the dyno curves on a stock engine would look like.

[Butters Stoch]

PM Chiknhed, he plays with cam °s a lot.

[jakermac]

PM Chiknhed, he plays with cam °s a lot.

We'll be exchanging texts about this sometime soon. I tried one day last week but he was busy. He got back to me Sat night, but I was at a wedding. We WILL connect eventually.

[328 Power 04]

It would be interesting to know how this goes for single vanos cars. I played quite a bit with the dual vanos system on m52tu, tuning the camshaft timing at wot in the ECU. You can totally change the behavior of the powerband. That's why I love dual vanos, you can make those camshafts do almost anything, and still no issues while at idle or cruising rpm.

[jakermac]

Well I spent a bit of time on the dyno recently, and I'm convinced there's a lot more in my motor with better cam timing. My current cam settings are significantly different from what the Metric Mechanic cam card suggests.

Current settings:

Intake advanced 6 degrees
Exhaust retarded 3 degrees

Metric Mechanic cam card (I think my interpretation is correct - anyone care to comment?):

Intake retarded 5 degrees
Exhaust advanced 10 degrees

http://i392.photobucket.com/albums/pp10/jakermacdorey/IMG_1721_zpsrdypelxv.jpg (http://s392.photobucket.com/user/jakermacdorey/media/IMG_1721_zpsrdypelxv.jpg.html)

http://i392.photobucket.com/albums/pp10/jakermacdorey/IMG_1720_zpsahdnblvg.jpg (http://s392.photobucket.com/user/jakermacdorey/media/IMG_1720_zpsahdnblvg.jpg.html)

http://i392.photobucket.com/albums/pp10/jakermacdorey/All_zpsb9x2zko9.png (http://s392.photobucket.com/user/jakermacdorey/media/All_zpsb9x2zko9.png.html)

[snaponbob]

That is a shit ton of power for an M50b25. What has been done to the engine, and what was the power like before the cam timing change?

[jakermac]

That is a shit ton of power for an M50b25. What has been done to the engine, and what was the power like before the cam timing change?

Not an M50B25. Deets from my post above:

The motor has many enhancements:

Imagineering 84.5mm 11.5:1 pistons (Paul Burke)
S52 lightweight crank
ATI damper
Lightweight Molnar rods
Mild port job
+1mm intake and exhaust valves (http://www.bimmerforums.com/forum/#)
Metric Mechanic Rally cams
Riot Racing BBTB
3.5" MAF/intake/filter
M50 manifold
RaceLand shorty headers and full single 3" exhaust
UUC 8.5lb flywheel
RK Tunes email tune with a couple small adjustments
All in an M52B28 single Vanos aluminum block from a 97 Z3 2.8

I hit the dyno for the 1st time with the intake cam timing pretty much where it sits now. The June plot had the exhaust cam straight up. The latest plot had the exhaust at 3 degrees retarded.

I think it's time for a radical swing in the cam timing!!

[328 Power 04]

Seems your VANOS off is around 5500rpm? Have you tried holding it on even higher?

[jakermac]

Funny you should mention that. I only just now was looking a bit more closely at my dyno plots and realized that from the June plot above to the dyno runs I did last Tuesday, I picked up about 10hp at 5,000. I suspect that was from changing my VANOS from 4,250 to 4,750. Then from last Tuesday to the plots from my last post, I raised it again from 4,750 to 5,150. I also had a bit more ignition timing (2 degrees) on the latest plot. I don't know if raising VANOS any higher would help. I think that dip might be some detonation.

I'm also thinking that my TB (68mm) might be starting to hold me back. But 1st, I'll address the cam timing.

[gstuning]

But a vacuum gauge on your plenum to see if the throttle body is a restriction.

[328 Power 04]

Funny you should mention that. I only just now was looking a bit more closely at my dyno plots and realized that from the June plot above to the dyno runs I did last Tuesday, I picked up about 10hp at 5,000. I suspect that was from changing my VANOS from 4,250 to 4,750. Then from last Tuesday to the plots from my last post, I raised it again from 4,750 to 5,150. I also had a bit more ignition timing (2 degrees) on the latest plot. I don't know if raising VANOS any higher would help. I think that dip might be some detonation.

I'm also thinking that my TB (68mm) might be starting to hold me back. But 1st, I'll address the cam timing.

In my RomRaider logs ...(log load at WOT with VANOS completely off and with VANOS completely on, switch VANOS off where load graphs cross) on a 2.8 with mild cam upgrade, I had best airflow characteristics with VANOS off around 5800-6000 rpm.

- - - Updated - - -

It takes VANOS about 200-300 rpm to turn off. So I set mine somewhere around 5700 in the tune, but I am still experimenting.

[digger]

your engine builder probably didnt want you to retard the inlet cam because its already got alot of retard as specced by MM perhaps too much. that seems to be the MM way though. probably why alot of their engines under perform as they time their cams for reasons other than best area under the curve.

[328iJunkie]

Tuned this a week or 2 ago. Chris Smith Racing in Braselton GA did the engine swap and did some custom cam timing that i havent dived into to see how they did it but:
OBD2 S52 fresh build, Stock cams, M50 manifold, Headers/full exhaust. Had to add 3.5" MAF at dyno because stock one was maxing out... Pretty sure the crazy cam timing is why the torque is so high. Highest ive ever seen with a setup like this...
https://lh3.googleusercontent.com/-mRaGlHILoYU/VnCGUUrVjxI/AAAAAAACT6U/VpqNwz4zGaE/w973-h486-no/Philip%2BSmith%2BE36%2BM52%2BRacecar.jpg

[jakermac]

Well here's my best STD graph:

http://i392.photobucket.com/albums/pp10/jakermacdorey/STD_zpsunu5axze.png (http://s392.photobucket.com/user/jakermacdorey/media/STD_zpsunu5axze.png.html)

[328iJunkie]

Looks like vanos shutoff point could get pushed a little farther up. Nice numbers either way! Figured youd do 275+ with those cams.

[328 Power 04]

Tuned this a week or 2 ago. Chris Smith Racing in Braselton GA did the engine swap and did some custom cam timing that i havent dived into to see how they did it but:
OBD2 S52 fresh build, Stock cams, M50 manifold, Headers/full exhaust. Had to add 3.5" MAF at dyno because stock one was maxing out... Pretty sure the crazy cam timing is why the torque is so high. Highest ive ever seen with a setup like this...
https://lh3.googleusercontent.com/-mRaGlHILoYU/VnCGUUrVjxI/AAAAAAACT6U/VpqNwz4zGaE/w973-h486-no/Philip%2BSmith%2BE36%2BM52%2BRacecar.jpg

This is interesting.

So the rest of the power jump was through being able to read more airflow, and fueling appropriately? I can't see much of it coming from ignition advance...

Actually I should ask if before and after is due to just software, or both hardware mods and software?

[328iJunkie]

This is interesting. So the rest of the power jump was through being able to read more airflow, and fueling appropriately? I can't see much of it coming from ignition advance... Actually I should ask if before and after is due to just software, or both hardware mods and software?
All software.
The 3.5" maf was just added as when stock maf maxes out it causes car to breakup sometimes.
3.5" maf alone adds no power 99% of time.

[jakermac]

its already got alot of retard as specced by MM perhaps too much. that seems to be the MM way though. probably why alot of their engines under perform as they time their cams for reasons other than best area under the curve.

Very interested in hearing more about this. If you don't feel its appropriate to post here, feel free to PM me.


Looks like vanos shutoff point could get pushed a little farther up. Nice numbers either way! Figured youd do 275+ with those cams.

That was just my highest peak horsepower. The VANOS has since been set to 5,150 and the torque dip is ALMOST gone.

http://i392.photobucket.com/albums/pp10/jakermacdorey/All_zpsb9x2zko9.png (http://s392.photobucket.com/user/jakermacdorey/media/All_zpsb9x2zko9.png.html)

[328iJunkie]

Very interested in hearing more about this. If you don't feel its appropriate to post here, feel free to PM me. That was just my highest peak horsepower. The VANOS has since been set to 5,150 and the torque dip is ALMOST gone. those afrs right? M50 family engines NA don't like 12:1... Too rich.

[jakermac]

those afrs right? M50 family engines NA don't like 12:1... Too rich.

They sure are. And that's at the tailpipe after a cat and 3 mufflers. My wideband in the car is reading 11.5-11.75:1. However my tuner doesn't want to mess with the fuel too much until I get the cam timing sorted. What sort of power do you feel I'm leaving on the table without being in the prime 12.5-12.8:1 range that these motors like?

[328iJunkie]

They sure are. And that's at the tailpipe after a cat and 3 mufflers. My wideband in the car is reading 11.5-11.75:1. However my tuner doesn't want to mess with the fuel too much until I get the cam timing sorted. What sort of power do you feel I'm leaving on the table without being in the prime 12.5-12.8:1 range that these motors like?
I see rich misfires a lot below 12, I'm surprised you don't. I run low 12s on s52s with knock tables augmented for cyls 5-6 (prevent HG issues) and high 12s low 13s on m52s... I can't speculate how much power you're leaving on the table but it's a good bit....

[digger]

Very interested in hearing more about this. If you don't feel its appropriate to post here, feel free to PM me.



on their old site they used to mention often about the late valve closing and so forth of their rally cams. the wide LSA on a sohc (or retarded intake cam on vanos) makes use of wave tuning to keep the cylinder being filled well after BDC which can help topend power if the rest of the engine is built around high rpm, but if the timing is too late it may never reach an rpm to actually make use of it.

the thing is if the valve is closing too late for the rpm you get reversion and you lose a bunch of torque because the trapping efficiency of the engine goes down (piston pushes air back out before valve closes) and you dont get as much benefit from the exhaust (not enough overlap).

Anytime ive seen a dyno of MM stuff its down on torque across the board their inlet valve closing point they use on their cams seems to far exceed what their motors are capable of IMO. The reason they do this is to keep idle quality, emissions and fuel economy. these reasons are also why their exhaust work on heads, cams, and system is extremely mild.

[jakermac]

Thanks for the insight. So would you think I'm wasting my time by trying to set my cams to MM's cam card and going back to the dyno? It's an autocross car and the last thing I want is to lose the midrange power I have now. And as far as the peak power, what do you think is currently holding me back?

Now I'm wishing I hadn't sold the S52 cams last week. Think I'd have made more power with them?

[digger]

cant help feel that setting to MM specs you'll lose chunk of midrange for a tiny bit of topend but ultimately the dyno will tell you where it needs to go, maybe they have actually dynoed and know it does work better. look at the spec that other cam grinders use and see how that compares to what MM have on the camcard.

one thing is dont go chasing peak hp look for area under the curve