Help in understanding Power Balance Test

[Bayarea Q]

A little background on what I did so you guys can help explain my power balance test. Just got the Q back and put 4K into her. Running ver nice!

Here is a quick list of what I had done:

cross drilled & slotted rotors (from AZhitman)120K servicePulled transmission to replace bad sensors (leaking ATF)transmission Flush with pan drop & Mobil 1Rail flushPulled Plenum replaced all air & water hosesCompletely cleaned Plenum & intake...throttlebody.

Power Balance Data:

CMPS-RPM(POS) 675RPMA/F ALPHA-R 100% (Not sure what this is?)A/F ALPHA 102% (Not sure what this is?)Coolant Temp 179 degrees Fsomething I can't read

[Bayarea Q]

Sorry my post submitted prior to finishing...

Continued:

Help in understanding Power Balance Test A little background on what I did so you guys can help explain my power balance test. Just got the Q back and put 4K into her. Running ver nice!

Here is a quick list of what I had done:

cross drilled & slotted rotors (from AZhitman)120K servicePulled transmission to replace bad sensors (leaking ATF)transmission Flush with pan drop & Mobil 1Rail flushPulled Plenum replaced all air & water hosesCompletely cleaned Plenum & intake...throttlebody.

Power Balance Data:

CMPS-RPM(POS) 675RPMA/F ALPHA-R 100% (Not sure what this is?)A/F ALPHA 102% (Not sure what this is?)Coolant Temp 179 degrees Fsomething I can't read 0.03 V

Power Balance Results "OK"

#1 73 rpm#2 92 rpm#3 91 rpm#4 73 rpm#5 112 rpm#6 94 rpm#7 98 rpm#8 103 rpm

I have 117K on my 95Q and had been maintained to this boards standards from 50K.I'm concerned about the high & low variances! I read a post from Q45 tech stating that you should be within 12 rpm's in each cylinder. I'm hoping Q tech has an idea why, and what I could do to level out the power balance results?I'm hoping it's not a sign of injector trouble.

Much thanks in advance,Robert

[Q45tech]

The thing that concerns me is that the test rpm should have been above 1000 rpms............1100-1300 rpms is normal.

When ever you see variances you redo the test 2 or 3 times, to get more data more samples.

After the rail flush/plenum clean was the engine driven at high rpms [2nd gear] for a while to clean the crud out? What was the sequence were plugs changed before the rail flush and plenum clean or after?

Probably too early for compression problems?

[Bayarea Q]

Not 100% sure on the order of the work done. The Infiniti dealer had my car for nearly a week. It was all done at once, and I would think they would have to do the rail flush last? Also not sure if the car was driven hard after the rail flush. I know that is the first thing I did when I got it back!! Lots of WAT's (per Q45 tech's posts)

My engine looks clean inside, has had regular 2-3 month (usally 4K) Mobil 1 Oil changes, and does not burn any measurable amount of oil during that time span.

I asked the sevice manager about the variance in RPM's and he stated it probably just needs to be driven for a little bit.

QTech, what would doing the test at a higher RPM indicate?

[Bayarea Q]

Also, which I thought was funny....the service manager really tried to up my quote all week. When I picked up the car he stated, "That was the last plenum job were ever going to do, just to time consuming."

[maxnix]

Also, which I thought was funny....the service manager really tried to up my quote all week. When I picked up the car he stated, "That was the last plenum job were ever going to do, just to time consuming."

Duhhh! What, he doesn't have the flat rate book?

See what Q45tech means when he says there are few service writers and fewer senior technicians that were trained on the G50 at introduction?

[szh]

Also, which I thought was funny....the service manager really tried to up my quote all week. When I picked up the car he stated, "That was the last plenum job were ever going to do, just to time consuming."

Which dealership did you go to?

Z

[Q45tech]

103 rpm drop from a 675 rpm idle [is a lot more significant than 103 rpm drop from 1200.

Each rpm is the summation of the power created by 4 cylinders less the frictional losses of compressing the other 4.Each cylinder is fighting against the other 7.

But the Consult II [on which your test was done] generates finer resolution [rpms to the single digit] vs the older Consult I which rounds things in 12 rpm increments....50,63, 75, 87,100, 112

[Bayarea Q]

I went to Infiniti of Marin.

[Bayarea Q]

If I'm understanding this right....the lower the rpm the better.

Is this a significant difference, where I should look into it? I'm thinking of taking the Q back in and have 3 power balance tests done. Perhaps the average of the three will be better....

Q45Tech- does this mean that my engine is not putting out as much power as it could?

[Q45tech]

Low rpm power determination is problematic because there is no LOAD on the engine during the power balance test other than the drag of TC.

All one can say is the range of typical rpm drops is around 75-87 rpm with a Consult I.

The other problem is injector flow may not be equal at such low [2.4 millisecond open duration].

The 14 psi compression variation range could create an 8% variation and 5% from injectors could if the sun and moon aligned correct in Aquarius become totally additive at 13% even 15%.....87 +- 6.5%= 75-87-100 rpm.

If the idle feels perfectly smooth [hand on plenum] why worry?

[Bayarea Q]

That's just it. I thought my idle would be smoother after the plenum job, intake cleaning, and rail flush. It seems to be slightly ruffer. Even my friend noticed. Not rough like there's a problem...he commented that it now sounds like a V-8 at WOT, where before he stated it sounded like a "Jappanese V-8.

I will to the hand on the plenum test, like you suggest.

My only concern was if these power balance #'s were a little high that I may not get the longevity out of the engine as say Q45Tech's car.

I will note that there is an increase in acceleration at high RPM's now. (after the plenum job) Must be getting more air....

Thanks for your comments!Robert