Dodge Challenger Forum banner

Help read my dyno chart

3K views 11 replies 4 participants last post by  R/TWildChild 
#1 ·
Text Font Paper Receipt Document


'13 392 6 speed,CAI,magnaflow cat back, ported TB & intake, 180 stat, email custom tune. Sounds like a lot of crap for the meager gains but I wanted to know for my self. I'm sure when a get a dyno-tune,(hope), that will help.

Anyway, my question is why are two of the runs very close to each other and the third one way higher in comparison? All three were done with stability control full off, 4 gear, and to redline.
 
See less See more
1
#2 · (Edited)
Ide say its one, some, or all three of the following:

- Based on the dyno chart, I can't tell which exact run, but it looks like one of the 3 pulls was made/recorded at a tad bit lower RPM and dumped a nice curve of fuel at the beginning/lower RPM theb even out at the norm A/F ratios previously ran; maybe it allowed the engine to build up a little more recorded top end performance gains.

- Seeing it's the third pull that produced the greater RWHP, maybe the car for lack of better words was "warmed up" and ready to perform its most optimal performance pull.

- 419 to 430RWHP. That's only about a 3% change using "gorilla math" and probably in line with fluctuation expectations on a Dyno session. Now if it was off by 10% + (50hp), I would think something might be wrong.


Sent from AutoGuide.com Free App
 
#3 ·
Oh the days I remember hanging out/cruising in Deep Park.
It would help to know more about the time lapse in-between pulls, if there was any. Where all three pulls done consecutively, back to back? If they were, then that would be an interesting jump in power for no apparent reason. However, if that third pull was done after a brief cool-down period. Say, after a break for lunch, or such, that would explain it.
Did you ever do any pulls on the dyno before you had the parts installed? A baseline for the car?
 
#4 ·
Haa, yeah man, those were fun days! At 45 though I'm not sure if my wife would take to kindly of me ditching her and the kids on a Friday night!

There was approximately a 7 minute lapse in between all the pulls. No extended sitting. As far as that though, I've heard guys say the "cool down" was mainly for the rear end, but anyway who knows. I've never had any other pulls on the car, not even prior to the mods. I just thought it was weird. Three pulls, two mirroring each other, then the third a solid 20 more on HP/Q.
 
#5 ·
Lol. I hear that. We're the same age. Not sure what it's like nowadays. But, I suspect it's not the same as back in the day.
Just out of curiousty, did the dyno operators spend any time at the dyno's keyboard, between the 2nd and 3rd runs? I once did an article for an automotive magazine, where we were trying to hit the magic 300 RWHP mark in a new '96 Forumla with an LT1. We hit 292, and the dyno operator said we'll give it a few min and try again. He went to the keyboard and changed, or altered some inputs, and we made a pull 10 min later. Guess what. We went from 292, to almost 301 in 10 min, corrected numbers. That was funny. Now, I'm not saying that's what happened here. Just curious.
If not, maybe there's some validity to what R/TWILDCHILD mentioned with the car warming up. I know it's really cold out there right now. So, maybe as the runs progressed, the fluids thinned out, and allowed for less drag, or resistance during the pulls, as the car's driveline warmed up. Other than that, I think I'd just chalk it up to an oddity and move on to the next mods.

What are your next plans?
 
#6 ·
No, no fussing with any keyboards in between runs. The runs were performed in August last year and I drove the car about 12 miles to the shop. I'd say all the fluids were up to operating temperature. It always struck me as odd about that difference.

As far as future mods I'm looking at cam, long tubes, high flows, under drive pulls, dyno tune, and barton shifter. I'm going to go 275/40/20 all around.

Guess that about sums it up thanks for your input.
 
#7 · (Edited)
It would be cause for concern, if a 20-40RWHP/TRQ difference presented itself with runs on same dyno. Based on your 11.9RWHP and 9.41ft-lbs TRQ difference in numbers for your three dyno runs, which isn't noticeable in the seat, I would say the runs went as they should have with just small factors/mechanical engineering playing a role on how the car performed on the dyno.

With Dyno pulls there could be one or multiple contributing factors to the variation you see in RWHP/TRQ. We can rule out increase due to torque converter lockup since you have a 6spd. Since your TRQ ranges for the three pulls are within (417.07-426.48) 10ft-lbs of each other and having a custom tune through H/F, you can rule out the tune being off. Unless, ignition timing and A/F ratio is off, but doesn't look like it. To bad you didn't get another pull after the last and final pull which produced the greatest RWHP.

However, I will put my money towards my assumption on the "warmed-up" scenario and contributing factors below:

Usually, dyno testing starts off with a vehicle at normal operating temperature. If your car was started cold, partially cooled down, or already warm but not on WOT runs. After the two pulls, the engine components and mixtures were then probably at optimal operating performance/temps. Thus leading to maximum engine performance and on your third pull gaining 11.9RWHP.

1. Keep in mind, the electric control unit (ECU) uses the information it receives from the engine coolant temperature (ECT) sensor to operate or adjust timing and fuel mixture for it to run at its optimum level. Depending on what your ECT sensor was mechanically reading, adjustments may have been made by your last and final run.

2. When warmed up/hot, the fuel is less dense and therefore the ECU will compensate for a less dense fuel by injecting more which is when you see the A/F range drop on the dyno chart at WOT. A less dense fuel is more prone to combust and therefore will combust much easier and faster which may be why you see the not big but slight vartions of a mild vs. steep curve in A/F ratio.

******If "heat soak" was considered, it would be more geared towards losses than gains. I would think if this was the case, the ECT sensor would have picked this up and kicked on the cooling fans as well to eliminate the heak soak factor.


In regards to what Perfracer was saying:

1. Some dyno shop owners with the Dynojet graphs, have been know to perform "smoothing" calibrations on the dyno reading from 0 to 5 with 5 being the highest amount of smoothing. The smoothing function flattens the mountain peaks along the power curve thereby adjusting the HP reading. The little peaks you see in the power curve can come from slight jerking motions of the tires on the dyno rollers due to unoticeable slack created due to the immediate pull/torque. Most dyno owners, make runs without "smoothed" curves so you can know truly and how efficient your engine runs. Smoothing can vary power readings by approximately 10HP.

2. Dynos that also have the option for vehicle inertia correction, a "sneaky" operator can take this route and enter faulty information to specify inertia value for your vehicle which will lead to the alternate RWHP/TRQ readings.

Each of these two actions can be done in a matter of minutes between runs. NOT saying any of the two dyno adjustments above happened, just in response back to Perfracer.

By all means, I am no expert on tuning a car or running a dyno. This is all just from my basic understanding, asking questions, knowledge extended to me by my buddy who owns the dyno shop and buddies who have had this question arise on many other occasion at our HEMI dyno events.

Sent from AutoGuide.com Free App
 
#8 ·
Anybody else have any ideas?? Thanks.
 
  • Like
Reactions: R/TWildChild
#9 ·
It would be really helpful to figure out if you had a tuner and data logged each run. And use your own wide band installed up ahead of the cats instead of the dyno shop's sniffer. My aftermarket wide band discovered a horribly lean condition at the top end 5400+ that my local dyno shop's sensor didn't pick up. And this was on a tune from one of the top shops on this forum.

Anyways, looking at the graph, and reading what you posted, it could be that your engine was sensing knock and pulled some timing on the first two runs. Really hard to say without more data. The first two runs look like a classic example of back to back runs without having anything adjusted. The third run is far enough off from the other two that I suspect something changed, somewhere, from the first two. And I'm not talking operating temperatures.

I have had this phenomenon happen to me several times. My tune is maxed out on ignition timing so much so, that some batches of pump gas from the same pump will knock a little, and some won't. Summer gas does better for me.

Possibilities:
1. Knocking caused retard timing
2. Engine ingested better air third time
3. Computer changed fuel trim slightly
4. Combo of any above
 
#10 ·
It would be really helpful to figure out if you had a tuner and data logged each run. And use your own wide band installed up ahead of the cats instead of the dyno shop's sniffer. My aftermarket wide band discovered a horribly lean condition at the top end 5400+ that my local dyno shop's sensor didn't pick up. And this was on a tune from one of the top shops on this forum.



Anyways, looking at the graph, and reading what you posted, it could be that your engine was sensing knock and pulled some timing on the first two runs. Really hard to say without more data. The first two runs look like a classic example of back to back runs without having anything adjusted. The third run is far enough off from the other two that I suspect something changed, somewhere, from the first two. And I'm not talking operating temperatures.



I have had this phenomenon happen to me several times. My tune is maxed out on ignition timing so much so, that some batches of pump gas from the same pump will knock a little, and some won't. Summer gas does better for me.



Possibilities:

1. Knocking caused retard timing

2. Engine ingested better air third time

3. Computer changed fuel trim slightly

4. Combo of any above

Ok. Have a custom email tune from a reputable tuner, H/F, can't use there name here. They had me data log, sent it back to me, install, then they looked at it again and said good to go. This tune was installed prior to the run. Would it still help to install my own wideband? I do have my Diablo. Also, I'm a mechanically inclined guy, did my cat back, lowering springs and other bolt ons by myself, so would I be able to do the install of the wideband you think? Any type you recommend? Thanks for your help.
 
#11 ·
Having a wideband hooked up to your trinity is a must for us guys doing performance upgrades, A MUST! Especially with the mods you plan on doing in the future. If I had gotten might right at the start of my tuning, it would have saved me so much headache in trying to know why my car was behaving one way or another.

I went through the same thing the first couple times I received e-mail tunes. I data logged the car with the PIDs that were on the trinity, and was told that it was good to go from two separate well known tuners on here. WRONG both times! Each one was off on the actual A/F ratio at different points. The open loop FA PID on the trinity is worthless for tuning IMHO. I will never go without a wideband again.

I use the Innovate LC-2 wideband sensor hooked up to my trinity instead of a gauge. I have the little box hidden behind the lower dash panel under the steering wheel. Then I got a 3.5mm stereo jack wire coming out of the V shaped space under the steering wheel with a 1.5mm jack adapter to plug into the aux port on the trinity. When I get done data logging, I simply stuff the wire back down into the V space to hide it. The sensor cord is really long, so I just wound it back a forth under the car by the transmission. Weld the O2 bungs in before the cats, one on each side. Get a couple screw in plugs for them incase you want to remove your sensor. I recommend welding in the bungs with the pipes off the car. The old exhaust I had I did them under the car = PITA + ugly welds. I had a shop weld in a couple stainless steel bungs on my new ARH mid pipes this time. Totally doable for anyone IMO. There is a youtube video that shows how to setup the trinity to read the wideband.
 
#12 · (Edited)
X2 on what Mopar R/T said, it's a must if you want to get her dialed in right and in a speedy fashion via email tune. Same or similar brand, this is what you would want to look into when looking into data logging A/F ratio and other parameters with the Trinity. Very easy to set up.

I purchased all my mods through one vendor but to each his own on their pricing and considered parts. :)

A/F wideband gauge controller/connection:
http://www.maperformance.com/aem-wideband-uego-afr-gauge-install-review-30-4110.html

Analog cable to data log through Diablo:
http://diablosport.shptron.com/p/t1015-diablosport-trinity-analog-pigtail-cable

Vent gauge pod for the A/F ratio gauge:
http://www.highhorseperformance.com/mobile/Product.aspx?id=6869


Sent from AutoGuide.com Free App
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top