Wanted to open a discussion, with Dyno charts, on A/F.

I was reading a post on here, about the Dyno tail pipe sensor not being very accurate (they need to be clean, changed)
So I understand they can be off some, so I am installing the AEM wideband to compare.

Talking to the Dyno operator, that did both mine and Derek's Dyno, he says that the sensor is changed ever 6 months or so, and cleaned ever few weeks (this sounds of, from what Charles posted earlier)
He says his Dynojet reading is very close to the Wideband gauges customer are getting.
He did admit, he seen it off as much as 3/4 of a point
So take this is mind, when seeing mine.

BUT mine are still wacked.

Check it out

Here is my first run on this infloor Dynojet, a couple months
ago
(with GReddy TT, Test Pipes, and stock exhaust)



Here it is with adding the GReddy Evo exhaust


Why are mine (and Dereks) so much higher then everyone elses ?

And on mine, NO signs of hearing detonation

 

Here is Derek's
Done on the same Dyno
He has on 03, GReddy TT, pullies, test pipes, and Borla

 

omg that first one is scary if its with your turbo.

tailpipe sensors are worthless. have them use one that they screw into your o2 housing, those types are very accurate.

 

AND GROUNDING KIT!

-D

 

Grounding kit POWAH!

 

There are two main problems with tailpipe readings. The first is that sensors tend to get fouled up pretty quickly, becuase they arent being naturally cleansed by 1000 degree exhuast gases. I have to say the DYNO operators i have talked to are totally clueless when it comes to cleaning and maintaining those tailpipe sensor. Not trying to generalize...but from my experience...they are oftentime not very well cared for.

The second biggest issue is the "lag" between when the engine actually fires, and the time it takes for the A/F mixture to work its way all the way to the tailpipe....this lag can be significant....that's why my AEM is always many many steps ahead of the crummy tailpipe reading.

OK..one more issue. If you run a cat, your readings will be leaner as well.


My car was trending lean on the dyno towards redline...to almost 14:1 or something like that....on the tailpipe sensor. But my AEM with its BOSHCH sensor showed me at or below 12:1. So what would you believe...the shittttty tail pipe sensor, or a quality BOSCH 5wire wideband sensor. That thing can measure from 9.5:1 to 19:1. I'd put my money on the AEM....plummed on the driver side cat...upstream of the cat element.


ACP...NOW....what you need to do....for the benefit of the community of course.....is to datalogg your AEM wideband output on your laptop, and then compare that to the dyno tailpipe measurements. If you are really slick, you could put the two AF graphs together, and we could dissect the differences.

 

ACP, regarding your question about the difference between A/F's between you and Dereks car. I noticed this same thing when 350Now and I dynoed on the same day. He car was runnning much richer than mine....even richer than when I actually had my RPM wire connected.

Apparently, there are lots of variations of ECU's and fuel/timing maps. So each car is likely going to dyno slightly differenly. That is the danger with these kits. They are designed and tested to work on one car...but that may or may not be indicative of how it will perform on another car. That's why I also tell people to dyno A/F check your car after install...just to make sure everything is OK. My car was lightly pinging at 11.5:1 at 4000rpm without timing regard at 5psi. What's up with that?? Combination of 91octane gas and aggresive factory timing advance. But 350now's car is fine...and doesn't ping.

 

I will do my best to do that

I was also thinking of adding 2 more bungs holes in the GReddy down pipe. One for the AEM wideband, and one for the Dynojet, just to compare...

What concerns me is only on these 2 charts (mine and Dereks) do I see the A/F start off so HIGH, then drop down

Can others post theirs to compare the curve ?
Also if anyone has the raw dynojet files of their dyno, pm me, as I would love to view them in the Dynojet RunViewer software to compare

 

Not to throw a wrench in this, but the AEM analog output isn't linear, which is what the E-01 is expecting. For a narrow range, it will be very accurate, but not as "dead-on" as you may think. Here is a link to a PDF that shows the curve.

http://forum.aempower.com/bbs/download.php?id=1627

I have the same problem with my ZT-2. I plotted their numbers (it reads ~9.7 -> ~21.2 A/F) and found that between 10.5 and 13.2 the curve was almost straight, so I only read within that range.

Here is a link to an M-250 that shows its analog output voltage (straight)

http://www.streetrays.com/catalog/pr...34478d47a93455

In the product description, it explicitly states:

"Wideband LINEAR Analog Output"

Again, I'm not tossing wrenches here...

-D

 

geezz....thanks for the wrench...ouch.

Well, this is really bizzare. This could explain why the AEM guage only displays 11-17 PSI, but the probe is good for about 9.5-19

Regardless, when I compare the output of my AEM with what displays in the Profec...they are identical...at least to 1/10 of an A/F point...I really cant notice the difference with my untrained eye.

Good research though...thanks.

 

Its not linear ?
Wow, found out just in time!
Just ready to install the AEM.

I will go with the PLX M-250 (the one without display, seeing I don't need the display)

I want to be as accurate as possible!

 

This is a problem!
The PLX gives Linear output which puts Stoich at 2.35 volts, while the AEM gives non-linear stoich at 4 volts. This is a huge difference. Both advertise this output as being compatible with a stand alone EMS. How does the EMS, or profec or whatever, know whether it is getting linear or non-linear input? (and what stoich is)
Look at the graph's, AEM is saying that 2.4 volts means 11.0 A/f, while PLX is saying that 2.35 volts equals 14.7. (which equals KABOOM!)
If gq's profec is even close to what his AEM is displaying, then it must be expecting a non-linear input. What happens if you plug in PLX? (It should read 8.8 on the profec and 11 on the plx, according to the graphs.)
About the ZT-2, it also advertises 0-5v output for a stand alone EMS. But they don't say anything about what the output looks like. Maybe it's linear, maybe it isn't. Does anyone have a graph of the zt-2 output?

This makes NO sense. These outputs graphs intersect at the very ends, but they are way off everywhere else.

 

ACP do you have A/F readings with Greddy TT and stock cats? I'm putting on a resonated test pipe and I am wondering if the test pipe will lean out the car that much. My A/F with Greddy TT and Nismo Catback was 15 @ 3100 rpm (close to stoich) and then drops to sub 10 @ 4800 rpm. I can attach my dyno if you guys need. Also you can try to do a dyno run on another shop just to cross checked the A/F readings.

 

Guys I've done many many WOT pulls in 2nd gear on a desserted street. The AEM and Profec Display are so freaken close....I cant even tell the difference. How could that be? The Profec takes a generic input...but it does have a feature where you set the measurement name...in my case...I slected A/F. Do you think the Profec automatically makes an adjustment becuase it now knows it getting a 02 sensor feed...and the assumes its non-linear??

 

I have HELIX testpipes with 2 bung holes, one for my AEM and one for the wideband on the dynojet.............my readings where identical........

 

GQ, that's what I was thinking maybe it was built into the Profec software that if it was taking an a/f reading for logging it is should not extrapolate the a/f to display linearly.

 

As long as the functions are linear, it doesn't matter if the numbers are different between manufacturers. You input the start/end voltage and the start/end A/F and the E-01 will calculate the function, giving an accurate reading.

-D

 

I don't think this is the case. Take a look at the curves from different non-linear wideband 02 sensors, they differ.

-D

 

And that it should be

What we are discussing, is something different
Read through the post
We are talking about sending the signal to the Profec e-01

 

Unfortunately I don't
The first Dyno place I went to, didn't have the A/F sensor hooked up.
I know the HP #s were the same in both places (but that doesn't help you)

But what I can help you with, is to show you my gains with the test pipes!
Big difference

Here is one of my early posts, that show my Dyno results with test pipes and high flow cats

https://my350z.com/forum/showthread....threadid=67663