Dyno flatlines after 5500RPM

[JimMueller]

That took care of it. Pretty impressed with the new scanning rates. The MAF error worked okay but VE didn't and I was like WTF? Found I had the axis labels reversed :

[mowton]

That took care of it. Pretty impressed with the new scanning rates. The MAF error worked okay but VE didn't and I was like WTF? Found I had the axis labels reversed :

Good deal, this new scanner is great.....

Ed M

[JimMueller]

I don't understand how to setup a filter to mimic steady state while calibrating tables such as VE & MAF. I presume I'd want to select the TPS parameter, but Unit, function & period?

[JimMueller]

I only intended to log a WOT pull, but when I saw how quickly the cells were being populated I decided to make a longer log. It seems something is wrong... PE EQ Commanded is showing as ~1.17 in the log, but for lambda it needs to be reporting the reciprocal, right? Can I correct this math without having to make another log?

Also, when I look in Math Parameters > EQ Ratio Error, the 50119 sensor is in red, even though the WB sensor is connected in the channel list. With it highlighted in red, it's confusing because it indicates the parameter is not being logged, even though it is.

[mowton]

I only intended to log a WOT pull, but when I saw how quickly the cells were being populated I decided to make a longer log. It seems something is wrong... PE EQ Commanded is showing as ~1.17 in the log, but for lambda it needs to be reporting the reciprocal, right? Can I correct this math without having to make another log?

Also, when I look in Math Parameters > EQ Ratio Error, the 50119 sensor is in red, even though the WB sensor is connected in the channel list. With it highlighted in red, it's confusing because it indicates the parameter is not being logged, even though it is.

Yes, you will need to generate an EQ Ratio to Lambda math paramater which is simply 1/[Eq Ratio commanded]. Then you will have to develop a new error math parameter which is 100*([WB]-[1/eq ratio command ]/(1/eq ratio command ). Remember we cant use a Math parameter within another Math parameter so you need to type out the EQ Ratio to Lambda conversion equation. The you take that new Lambda Err Math Parameter and insert it into you Graph(s).

Ed M

[JimMueller]

Things I noticed on the partial WOT pull and pair of full WOT pulls is:

1) the fuel pressure drops to low 50's around 4400RPM and isn't smooth, sometimes with large spikes. People on tech advised that if I added a little more fuel and it stayed the same, not to worry about it.
2) the CylAir bounces around while I'm in PE
3) the MAF g/s bounces around also
4) the MAP goes a little low beginning at 6100RPM but randomly recovers. People on tech thought it was pressure waves from the intake valves.
5) IPW maxes out around 16.x around 4600RPM
6) MAF Hz maxes out at 8915Hz, but table extends to 11250Hz
7) Not getting any KR while in PE above 2400RPM

Do you see anything in the pulls which indicate a tuning problem or failed physical part such as lifters bleeding down, weak valve springs, bent valve (misfire detection is still enabled just desensitized, so I'm not receiving any P0300's), bent pushrod, etc.? I was hoping to validate the concern prior to randomly throwing money at parts to resolve it.

[Keith@HPTuners]

Looks like an airflow restriction. Maybe your intake is collapsing somewhere.

[mowton]

Post the pulls so we can take a look....

Not sure if you need them but here are the Charts and Graph files to go with the math from last night...

Ed M

[JimMueller]

Post the pulls so we can take a look....

Not sure if you need them but here are the Charts and Graph files to go with the math from last night...

Ed M

Which pulls are you referring to? The dyno pull is in post #1, and the WOT pulls are contained in the log attached to post #24. The longest WOT pull in the log starts at 33:12.

Intake tract is pretty short, and the tubing is pretty thick. It starts with a Fram paper air filter, the lid with an 85mm neck, then there is a thick rubber hose, then the 100mm MAF with a Saxon PC airflow straightener in it, then another short tube which connects to a 92mm throttle body, which connects to the LS3 intake. The last time I took part of it was when we did the compression test in September... I can take it off again looking for debris but historically it hasn't been an issue.

[JimMueller]

Any other feedback, guys? I've seen where you can diagnose engine problems with a physical vacuum gauge. While I have one, would it be better to use a handheld gauge or the log the manifold vacuum parameter?

http://www.earlycuda.org/tech/vacuum2.htm

[GHuggins]

Any other feedback, guys? I've seen where you can diagnose engine problems with a physical vacuum gauge. While I have one, would it be better to use a handheld gauge or the log the manifold vacuum parameter?

http://www.earlycuda.org/tech/vacuum2.htm

Map sensors the same way - reads manifold pressure... Basically your looking for something withen 2 or 3 kpa of baro durring a wot pull. It'll be perfect baro with a completely unrestricted setup. Then possibly above baro with a really nice designed system (natural boost so to speak) - You can also use the engine load cells to determine this durring a pull = vacuum gauge not necessary, but still really nice in diagnosis to understand not only how to use, but what your looking at

[JimMueller]

My bad. We still don't know what is done to the motor? Heads/ cam/ intake???

Can go with what ever gear gets you to the issue the fastest and safest. Look at the log when complete and we are looking for signs of issue like MAF Hz maxed, IPW >19ms at or over 6000 rpm, maybe even Torque management (spark, Fuel or TPS%) in play etc. Maybe ad a pedal parameter so we can see where it is during the pull.

Ed M

I provided the log and build details two weeks ago. Still waiting on a review of the log & tune to see whether anything in the tune represents either a calibration issue or if the log indicates a physical parts issue.

[GHuggins]

You cylinder airmass drops off right where your flat lining... Some possibilities are exhaust or even cam degreeing or design...

[JimMueller]

I'm going to pickup a exhaust back pressure test kit and check the pressure before and after the cats with the cutout closed, and again with the cutout open.

[JimMueller]

Finally had a chance to test exhaust back pressure today. Ordered one of these from Amazon:

http://www.amazon.com/Tool-Aid-33600..._prd_ttl_sol_4

Tech said he tested it manually before we attached it and got the needle to move. Plugged it into post-cat both banks, and pre-cat bank 2, tested at both 2K and 4K. Only received a slight flicker post-cat B2, others didn't move the needle at all.

I found another dyno with similar graph behavior (below, albeit designed for a LS1 not LS3) and similar design goals. His dyno peaks a few hundred RPM higher but mine seems to carry past peak better:



Compared to mine:


So I guess it must be the cam valve events, unless you see something which would indicate a lifter problem or weak valve springs?