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      03-22-2011, 10:23 AM   #1
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JB4 CPS offset dyno testing and logs

Some data and commentary from BMS you guys might be interested in as this was a topic covered a lot over the last few weeks. I haven't seen data like this presented before and find it very interesting.

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Hey guys,

Did a little dyno testing today with the new JB4 CPS module. Mainly to confirm what I've been observing during street testing and to quantify the numbers. In summary the results went about as expected. To clear the knock threshold and avoid drops much more CPS had to be offset than anyone performance oriented would want. Ultimately I'm still not sold on any significant benefits but understand that many of you want CPS and remain committed to providing you the product.

Testing was done in our 135i with full bolts ons, using 91 octane fuel. In theory the CPS offsetting should benefit us 91 octane users more than 93 octane users so this represents somewhat of a "best case" scenario for the offset. To keep things consistent map 2 was used for all runs with this first round of testing. Map 2 (14.5psi) represents an "aggressive" map considering the 91 octane. Temps were in the 50s and the only thing changed between runs was the CPS offset amount. Several runs were done in each configuration and an average/representative run was selected to avoid data overload.

CPS is mapped on boost and RPM on a preliminary basis and then globally user scaled from 0-100%. Giving us an easy way to compare various offset amounts. Ignition advance represents what the DME thinks timing advance is while CPS represents how many degrees of negative offset/retard are being applied. If you're interested in the actual timing advance you would subtract CPS from ignition advance.

First up the no CPS run. About as expected given the 91 octane with timing dropping off at 4200rpm (VANOS change over) and once more at higher RPM. Despite this the power curve was smooth and strong.



Next up I added a moderate amount of offset amounting to 2 degrees down low and 4 degrees up top. Similar to what others run. Despite this the timing drop at 4200rpm was still present, only not as severe, and strangely a new timing drop cropped up at 6500rpm. Power was largely unaffected as we're still apparently operating under the knock threshold.



Given the drops at 30% I moved up to 50% hoping to stomp them out. Unfortunately, very little changed aside from output being slightly reduced.



Finally at 60%, 4 degrees offset down low, and 8 degrees offset up top, I was able to eliminate the drops. So the knock threshold value appeared to be somewhere between 50-60% given this boost level and conditions. Although the timing curve "looks great" power took a huge hit. Which is exactly what I've been feeling on the street. Offset enough to reduce the drops and the car becomes a complete slug.



For the sake of thoroughness I did a run at 75% offset and was surprised by the result. With 10 degrees of offset, running around 2 degrees of actual advance at 6500rpm, another drop. Crazy. Power also really took a dump with this huge offset.



I did a run at 100% as well which I can share if anyone is interested. But with negative timing the whole run the power curve was quite odd and a good 80whp down from no offset.

Here are the actual dyno runs for each of the logs above.



Just to get a few more datapoints I did a few runs on map 1 (13psi) with 0% cps, and with 25% cps, to see what benefit there might be for the average map 1 91 octane user. The 25% CPS did help stabilize the advance but surprisingly both runs were almost identical on the dyno.





The dyno runs for those two logs.

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      03-22-2011, 10:39 AM   #2
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Imo you guys are applying the offset wrong that's why you.are killing the power. Notice how map 1 looked smooth with the offset and made similar power to map 2. I would personally start at 6 degrees offset and ramp down to 3-4 for map two.
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      03-22-2011, 10:48 AM   #3
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Why did you choose to dyno first with no cps, then with cps as opposed to first with cps, then without? Wouldn't after many dyno pulls the car would be more likely to drop timing, giving the no cps offset the biggest advantage?
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      03-22-2011, 11:43 AM   #4
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Isn't loss of power a result of too much advance or too much retard?
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      03-22-2011, 11:49 AM   #5
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Very interesting results, great info. Been waiting for this. I gues this help provide some people evidence to what all the fuss around here was lolol.
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      03-22-2011, 11:51 AM   #6
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I know you're trying to reduce "knock" but isnt it best to run at mbt. There wouldn't be any drops at mbt, correct?
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      03-22-2011, 11:58 AM   #7
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Cool data. The drops at the top are interesting... especially with the increased offset. There is a couple boost spikes and maybe dyno environment wasn't so great. IAT doesn't seem to be rising until the 60% cps graph though.

There is definitely a relationship between boost and timing. The reduced timing curve is important in reducing chance of knock, BUT also in reducing the advance slope which will reduce the frequency of knock events.

FYI: any sudden drop is NOT a VANOS event... timing due to VANOS shift happens over 1000rpm about 3deg gradually
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      03-22-2011, 12:00 PM   #8
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Quote:
Originally Posted by gbreeE90 View Post
I know you're trying to reduce "knock" but isnt it best to run at mbt. There wouldn't be any drops at mbt, correct?
I don't think we are anywhere close to mbt (min timing for max brake torque) with the n54 at higher boost on pump. detonation is the only concern.
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      03-22-2011, 12:07 PM   #9
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Quote:
Originally Posted by Clap135 View Post
Imo you guys are applying the offset wrong that's why you.are killing the power. Notice how map 1 looked smooth with the offset and made similar power to map 2. I would personally start at 6 degrees offset and ramp down to 3-4 for map two.
Good call didnt even think of that. I'm used to cars with torque near redline
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      03-22-2011, 12:12 PM   #10
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It looks like BMS has a lot to learn about HOW to properly apply CPS offset. Interesting...
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      03-22-2011, 12:24 PM   #11
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That's actually being nice. This is an incorrect crude application of the feature at best.
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Originally Posted by usc335 View Post
It looks like BMS has a lot to learn about HOW to properly apply CPS offset. Interesting...
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      03-22-2011, 12:33 PM   #12
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Yes, I was being nice. I know quite a few people in the "Industry" and they all just shake their heads at the notion about timing control (or lack thereof). They can't believe people are that gullible (I'm being nice again).
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Originally Posted by Clap135 View Post
That's actually being nice. This is an incorrect crude application of the feature at best.
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Originally Posted by usc335 View Post
It looks like BMS has a lot to learn about HOW to properly apply CPS offset. Interesting...
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      03-22-2011, 12:33 PM   #13
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Quote:
Originally Posted by Joshboody View Post
Cool data. The drops at the top are interesting... especially with the increased offset. There is a couple boost spikes and maybe dyno environment wasn't so great. IAT doesn't seem to be rising until the 60% cps graph though.

There is definitely a relationship between boost and timing. The reduced timing curve is important in reducing chance of knock, BUT also in reducing the advance slope which will reduce the frequency of knock events.

FYI: any sudden drop is NOT a VANOS event... timing due to VANOS shift happens over 1000rpm about 3deg gradually
It was quite interesting that the runs without CPS were the smoothest despite having the worst timing curves. And the runs where timing "looked great" produced less power and were less smooth. If dropping timing 10 degrees didn't eliminate drops at 14.5psi nothing will. That boost level is just too much to consistently support on 91 octane without drops regardless of the timing curve IMHO. It's looking like the best way to use CPS is to offset 2-3 degrees and maybe 1 degree more per gear and call it a day.

Any guesses on how "powerful" this dyno run was? Note smooth negative timing the entire run...



Mike
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      03-22-2011, 12:36 PM   #14
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That run probably looked like dog shit as you are affecting injection timing and a bunch of other things. You have a lot to learn in regards to how to correctly apply this useless feature.
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      03-22-2011, 12:38 PM   #15
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Quote:
Originally Posted by usc335 View Post
It looks like BMS has a lot to learn about HOW to properly apply CPS offset. Interesting...
Looks more like CPS isn't all its cracked up to be which isn't surprising at all. That said they will make the best of it. Offsetting 2-3 degrees doesn't seem to hurt much and cleaned up the timing curve a little. And all you "pro tuners" out there will be able to setup whatever CPS curve you'd like with the JB4 interface soon. Similar to how you can setup your own boost curve.

Mike
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      03-22-2011, 12:40 PM   #16
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Actually all the people with tuning experience are amazed at your lack of understanding in regards to how timing is applied....
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      03-22-2011, 12:45 PM   #17
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Quote:
Originally Posted by Clap135 View Post
Actually all the people with tuning experience are amazed at your lack of understanding in regards to how timing is applied....
+1 (and I never do this)
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Last edited by usc335; 03-22-2011 at 01:42 PM.
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      03-22-2011, 12:55 PM   #18
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Quote:
Originally Posted by Clap135 View Post
Actually all the people with tuning experience are amazed at your lack of understanding in regards to how timing is applied....
LOL why don't you break it down for me then. If 4 degrees didn't eliminate the drops, and 6 degrees didn't eliminate the drops, and even 10 degrees didn't eliminate the drops, your big plan is what? 2 degrees? The big fly in the ointment here is the drop with 10 degrees offset at 6500rpm.

Also the runs with the most "knock" according to "e90post pro tuners" proved to be the smoothest and most powerful on the dyno. Hmmm.

Mike
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      03-22-2011, 12:56 PM   #19
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Quote:
Originally Posted by Mike@N54Tuning.com View Post
Looks more like CPS isn't all its cracked up to be which isn't surprising at all. That said they will make the best of it. Offsetting 2-3 degrees doesn't seem to hurt much and cleaned up the timing curve a little. And all you "pro tuners" out there will be able to setup whatever CPS curve you'd like with the JB4 interface soon. Similar to how you can setup your own boost curve.

Mike
I hope this isn't the approach BMS takes due to one dyno session. From the graphs you can see that there needs to be more testing on when and how to apply cps AND play with boost more... if the boost is too aggresive for the environment, the timing will be crap no matter what. keep in mind that the tune is telling the the ECU the load... determines timing. And actual load curve is different... so applying cps in relation to actual / fake load would be a good start.
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      03-22-2011, 12:57 PM   #20
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Quote:
Originally Posted by GeorgiaTech335coupe View Post
Why did you choose to dyno first with no cps, then with cps as opposed to first with cps, then without? Wouldn't after many dyno pulls the car would be more likely to drop timing, giving the no cps offset the biggest advantage?
Response?

It can easily be verified on a dragstrip that a cooler engine will yield more hp, holding all else equal.
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      03-22-2011, 01:00 PM   #21
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Quote:
Originally Posted by Mike@N54Tuning.com View Post
LOL why don't you break it down for me then. If 4 degrees didn't eliminate the drops, and 6 degrees didn't eliminate the drops, and even 10 degrees didn't eliminate the drops, your big plan is what? 2 degrees? The big fly in the ointment here is the drop with 10 degrees offset at 6500rpm.

Also the runs with the most "knock" according to "e90post pro tuners" proved to be the smoothest and most powerful on the dyno. Hmmm.

Mike
Don't worry once I get home I will educate you and terry. It's simply too much to type using my phone. Hates a hint though. If you drop timing in the low rpm range you will knot knock up top where as before you did. Do you actually understand how that works? Elimination of timing at exact drop outs is not the solution. Also pick up a book and understand what happens to egts as you drop timing....
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      03-22-2011, 01:04 PM   #22
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Clap are you saying that this is in some way a more crude application of CPS offset than what procede did in v5 prior to dynamic ignition timing release (current)? Personally wouldn't think so as procede would apply a static CPS offset prior to DIC, no? Exception being boost was being auto-tuned as well
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