Boost Profile With 2.8 Cams (Log Inside)

B5 S4/ RS4
#1

So I was able to pick my car up, and grab some logs on the way home with the 2.8L cams. Unfortunately, the only previous logs are with the OEM MAP sensor, as the car started misfiring shortly after installing the Zeitronix. So it is hard to compare the complete boost profile, but from looking at the logs on the OEM MAP sensor, it appears that boost to redline is the same. Spiking to 25 and holding around 21 to redline.

http://i805.photobucket.com/albums/yy338/temanuele91/Boost.png

Here is a log from the OEM MAP sensor. You can see that the taper at the end is nearly identical.

http://i805.photobucket.com/albums/yy338/temanuele91/BoostProfile.png

I expected the wastegate duty cycle to be lower, but it is just about the same.

http://i805.photobucket.com/albums/yy338/temanuele91/WastegateDutyCycle-4.png

Initial impression is that the cams aren’t worth it. While I was already changing my camshaft seals and valve cover gaskets, it made sense to throw the new cams in there. But if I were to do it solely for the purpose of installing cams, I might hold off. Granted this is a very preliminary analysis, so I’ll save the judgement for some further review.

More logs to come…

#2

nice update on this, thanks!
I wouldn’t expect the n75 duty to be any lower becasue you are working over the map sensor limit most of the pull… using the hard limit on n75 vs the soft limit variable table especially if the req boost is over the map limit.
The differenc you do see may be from the difference in starting load or rpm of the pull.

#3

Thank you!

Have you been able to test fats or something with the new cams?

Regards

#4

well that sucks i was hoping to see some nice gains

#5

That is a good point Jude, I hadn’t considered that. Driving the car more, it certainly feels like it builds boost much faster. It looks like this in the log, but that is more a matter of where I went WOT. But, aftering doing more logs, it does appear that boost is coming on quicker. When driving around, if I mash the throttle the boost seems to instantly hit 20 psi.

It will be hard for me to get an accurate FATS comparison, since the file I previously ran is no longer on my ECU. Sorry for the lack of hard results and data, the cam installation came as more of a result of my leaking valve cover gaskets than a straight need for cams. I’ll give some more updates once I have my fueling dialed in. But my impression at this point is that, while boost taper seems to be the same, the boost does seem to build noticeably faster.

#6

Usually the main reason for upgrading the cams is for the increased power/airflow (usually manifest at mid/high RPM//big turbo/high-ish boost points), and any spool attenuation is more an incidental byproduct than the actual goal itself. The gains (if there are some) should be seen in power, not necessarily increased/decreased lag (speaking generally about RS4/2.8 cams).

#7

Agreed, it was an entirely subjective thought and it could simply have been that I got used the the throttle response of driving another car while mine was in the shop.

As I think about it, I feel that it would be hard to quantify the gains of cams through logs. I had been told (and seen some logs) that the boost profile would be flatter to redline. Hopefully someone can chime in on this, but I don’t see how this would be so. The main difference is that you would be keeping the intake valves open longer, thus leading to more air in the cylinder (leading to higher pressures). With boost values being measured at the manifold, I don’t see how cams would make any difference to this. Possibly more airflow leading to lower compression surge, but this is just me thinking out loud.

I’m not sure how I would go about comparing cylinder pressures through logs. Since I already have the cams in there, it would be impossible to test before and after cylinder pressure. A direct result of the gains in cylinder pressure would be increased torque at the crankshaft, but I also do not have before or after dynos. So, it seems that it will be impossible for me to provide an accurate analysis of the cams given my lack of previous data.

#8

Thanks Jibber for the insight…So do you think it is worth the time to install RS4/2.8 Cams in a K04 platform like myself? I know as you said they are mostly for bigger turbo applications but just wondering if it would be worth trying?

#9

If you have nothing else to upgrade, then sure. It’s probably the last thing I’d do on a K04 setup, as better IC’s, meth, a custom tune, etc are all better upgrades, if they’re not done already.

#10

Time to put the car on the dyno and do some test with a racelogic device… for future data.
Regards

#11

For now, I have been doing some FATS times. I am going to throw my old file in the car and try to get a somewhat accurate comparison. From my early testing, the numbers do seem better but I will post some logs and explanation soon.

#12

where are you located? We probably know someone with a pbox near you.

#13

That is a good start .
Thanks for your time.

Regards

#14

I have a Racelogic. I am not concerned with obtaining the times, but rather producing comparable results. Once I have everything dialed in I will be taking a stab at the K04 60-130 record.

#15

I’d still be interested in seeing a spool/boost profile log of the 2.8 under the same conditions (same road, starting RPM, starting load, ambient conditions etc) as the 2.7 cams log, if you get time and have marked down where you did the previous 2.7 cam log.

#16

Here is the closest comparison that I could find. Load requested was at the same time, on the same stretch of road. Ambient conditions were much better in the previous pull though. I also think that I have found a solution to my boost taper, so I will post this up once I have tested it out.

http://i805.photobucket.com/albums/yy338/temanuele91/BoostOnsetBeforeandAfterCams.png

#17

Nice data with the cams. I’m sure I’ll throw 2.8 cams in whatever I end up doing down the road.

How many miles are on your K04s? Just curious… I have over 50K miles now on mine still running strong.

#18

Pretty new, less than 10,000 miles. Ya 2.8 cams are so cheap, that if you are already taking off the valve covers, it makes sense to just change the cams. I’ll have some better data for comparison soon.