2009 370Z - Questions about Data logs, confusing information.

[Sh0velMan]

Hi All.

Recently began modding my Z, getting some.. interesting data.

Basically there's a 'corner' at around 6300rpm where power gain drops off, this correlates to a flat spot in the GM/S log from the Cipher.

What is going on here? Is the ECU enforcing an artificial flow limit of some kind? The reason that I suspect that is the case because no other parameter clips at any point and friends with similar cars but with different parts (Aftermarket intakes for example) are getting the same clipping of GM/S.

Any thoughts?

Dyno and data below.. Thanks in advance!

RPM|  MAF-GM/S/|MAS B2|MAS B1
6063	258.4	4.09	4.01
6100	257.79	4.11	4.09
6138	257.18	4.04	4.15
6188	258.14	4.12	4.06
6213	262.09	4.05	4.2
6250	265.29	4.13	4.03
6288	268.79	4.07	4.17
6338	268.79	4.1	4.23
6350	268.79	4.18	4.1
6388	268.79	4.21	4.12
6425	268.79	4.1	4.23
6463	268.79	4.2	4.15
6500	268.79	4.2	4.15
6538	268.79	4.21	4.15
6550	268.79	4.09	4.23
6575	268.79	4.1	4.22
6613	268.79	4.17	4.22
6650	268.79	4.22	4.12
6688	268.79	4.17	4.22
6725	268.79	4.21	4.18
6738	268.79	4.23	4.19
6775	268.79	4.27	4.13
6813	268.79	4.2	4.26
6838	268.79	4.26	4.19
6875	268.79	4.18	4.28
6913	268.79	4.16	4.33
6950	268.79	4.23	4.33
6975	268.79	4.17	4.32
7013	268.79	4.25	4.33
7038	268.79	4.28	4.28
7075	268.79	4.22	4.37
7125	268.79	4.31	4.19
7150	268.79	4.32	4.2
7188	268.79	4.3	4.35
7225	268.79	4.31	4.29
7250	268.79	4.3	4.27
7275	268.79	4.28	4.25
7300	268.79	4.27	4.26
7325	268.79	4.28	4.26
7350	268.79	4.26	4.26
7375	268.79	4.25	4.24
7388	268.79	4.25	4.22
7413	268.79	4.24	4.2
7438	268.79	4.21	4.13
7450	268.27	4.16	4.08

[Mandingo]

I've noticed something similar in my datalogs. My MAF Gm/S usually maxes out to 268.79 at 6400rpm (and about 6200rpm in cooler weather).

This is with stock panel filters. What intake do you have?

[Sh0velMan]

I have the drop ins.

My concern is that something in the ECU is holding the engine back. If that is the case, I don't see how an aftermarket intake would yield any gains.

[Mandingo]

I think the issue is the intake capacity. When you look at overlaid dyno graphs of say, a Stillen G3 and the baseline with stock airbox, you notice the G3 graph continues on a more upward trajectory after 6400 rpm where the stock graph falls off more drastically.

Hopefully someone with more experience than me will chime in soon

[Megan370z]

all I know about this is when I asked Uprev , I received an answer that as long as the MAF voltage contiue , the rest doesnt really matter

[Jordo!]

It's probably the VVEL tuning... currently a non-adjustable parameter.

If the power doesn't drop off, don't sweat it. If it does, you can probably fine tune the AFR targets to gain some back.

[Sh0velMan]

That's the thing, power does drop off.

Once I have an aftermarket intake on the car we will dyno again and I can check the numbers for comparison. It may be of no consequence.

If it IS the VVEL tuning, well, that sucks. haha.

PS: I should say that the car will be getting an UpRev tune on it as well after we have added a few more parts, so it may be something we can add fuel and work around..

[Sh0velMan]

Okay, so it's definitely related to VVEL... Which is a little depressing. (because we can't adjust it)

See chart attached.

[ImportConvert]

Originally Posted by Sh0velMan

Okay, so it's definitely related to VVEL... Which is a little depressing. (because we can't adjust it)

See chart attached.

I'm sure even VVEL has limits on what it can flow. The limit is reached at that RPM I guess and so the MAF behaves as such maybe?

just a guess. Not pretending to know.

[Sh0velMan]

What's also telling is that you notice there's a hump at the end there, right before redline?

Check out the dyno I have posted in this thread, you can see the same hump..

DYNO - NISMO CBE and K&N Dropins

[Sh0velMan]

Originally Posted by ImportConvert

I'm sure even VVEL has limits on what it can flow. The limit is reached at that RPM I guess and so the MAF behaves as such maybe?

just a guess. Not pretending to know.

Well I think the 'Flow limit' is an artificial one that they have tied to whatever piece of software controls the VVEL. Think of it as the highest end of the scale for the VVEL's map of operation.

Now what is funny is the hump just before redline. That, to me, looks like something they have put in there for high peak HP for magazines and bragging rights. If they were being competent engineers (assuming that the hump's peak is the theoretical maximum the VVEL system can achieve) they would have it continue to scale as normal and not flatten out at 6300RPM just to peak again 800RPM later. I think they saved their last hurrah for just before redline to boost their peak HP numbers.

[Red__Zed]

Interesting

[Jordo!]

You should be able to tune around it tho' -- have you tried adjusting timing and/or target AFR's around there?

[Sh0velMan]

Originally Posted by Jordo!

You should be able to tune around it tho' -- have you tried adjusting timing and/or target AFR's around there?

Once we get the uprev tune in place we will do just that.

I will update this thread once I have more data in that regard.

[mikey1600]

nice find, will keep an eye on this post as looking to get a tune done in the next few weeks