Dyno and datalog results - expected?

[Bob_L]

Hi all,

So I took my car up to one of the local sponsored dyno events to see what numbers the car would make. While we were at it, I decided to datalog the session as well.

The numbers were a tad lower than I expected, but I don't know anyone else who only has "some" bolts-ons (let alone the same ones I have), and as a result I don't have any basis for comparison. It seems like most everyone in the area are either stock, or they jumped head first into FBO+.

For powertrain mods I'm running an RV6 catted downpipe, RV6 frontpipe, and PRL intercooler; everything else is stock (charge pipes, etc).

My tune is a Phearable Stage2 OTS tune. I've had one revision - the first version was when the car was fully stock; the currently installed revision is supposed to account for the dp/fp/intercooler. At my request, the tune is rpm limited to the factory default 7k (no 7200 for me).

The temp during the dyno session was 80 degrees F. All three pulls on the dyno were very close together so there was significant heat soak in the later two pulls.

Anyway, the first pull showed max of 351hp at 5910rpm and 373fp torque at 3760rpm.

In regards to the results, is such a wide range of rpm between max hp and max torque typical for the CTR? Also, given what I've read I was sort of expecting to be a bit higher with the bolt-ons and tune I have, but maybe that's the difference between reading about something and actually doing it. Have others had similar results?

Also, when I reviewed the datalogs (which I'll try to attach), I saw that when at or near max rpm, the "Knock Level (%)" got very high - 175 during the first pull, and close to that for the other two. I'm vaguely familiar with knock at a high level, but I don't know what "knock level percent" is. Is this something to be worried about?

Thanks for any insight that anyone can provide.

-bob

Edit: One last thing, not performance related - After the car was strapped down, we did the petal dance before starting the dyno runs as indicated on the fk8.wiki to fully disable VSA. We got the expected instrument results - blinking VSA light and forced into sport mode. However, when the session was over, the computer was still freaked out and gave the usual warnings about everything either disabled or having a problem, just like when flashing the ECU. So, even though we followed the steps and got confirmation from the car that VSA was fully off, it didn't seem to make any difference. As expected, it cleared up after a few miles driven and a couple restarts. Just a heads up for anybody who may be interested.

 

[Lagos]

Don't worry about Knock level %. Thats just an output from the knock sensor and there are RPM/Load specific thresholds for it to stay below (not really one value that is good or bad).
What you want to look at is Knock Retard 1,2,3,4. Also, the knock count doesn't do anything.

In your run I see some timing being pulled out. I'm seeing like 1 degree, so it shouldn't be a big issue. I think the bigger factor would be the high IAT. You would probably do better coming back to the dyno in the fall when the ambient temperatures drop.

Its also interesting to see that you have -8% on your LT trim, which is a similar thing I noticed with my own car recently.

 

[Bob_L]

Thanks!

Out of curiosity, what does LT trim do or represent?

On a wholly different thread on another site, I found this:

"If the LAF is reading that the exhaust gas is too rich (showing Air Fuel ratios less than 14.7:1), the short term fuel trim goes negative, giving less fuel.

If the short term stays negative for enough time, the long term will start to drop as well."

So I take it that the ECU is measuring the exhaust and has determined that the mix is too rich and so is leaning it out by 8%, is that right?

-bob

 

[Lagos]

Thanks!

Out of curiosity, what does LT trim do or represent?

-bob

There is Short Term Trim and Long Term Trim. Short term reacts instantly to make adjustments to your air to fuel ratio based on the feedback it gets from the wide band o2 sensor. Long term looks a the adjustments that have been made, determines if they were valid, and learns a trend.

Your car is commanding 8% too much fuel. The computer sees this and is removing 8% to put things back into check.

Mine has been doing the same thing and I've been trying to figure out if its a problem or normal behavior based on the hot weather and ethanol content in our gas.

 

[Bob_L]

There is Short Term Trim and Long Term Trim. Short term reacts instantly to make adjustments to your air to fuel ratio based on the feedback it gets from the wide band o2 sensor. Long term looks a the adjustments that have been made, determines if they were valid, and learns a trend.

Your car is commanding 8% too much fuel. The computer sees this and is removing 8% to put things back into check.

Mine has been doing the same thing and I've been trying to figure out if its a problem or normal behavior based on the hot weather and ethanol content in our gas.

Ah, so what I found wasn't too far off.

I read recently that the Biden administration is temporarily allowing fuel to be 15% ethanol during this summer to combat high gas prices. Could it be that?

-bob

 

[BoostedDreams]

I’m on phearable stage 2 tune with the same mods plus the PRL HVI. My LTFT is also in the 7-8% range.

 

[sLing]

Ah, so what I found wasn't too far off.

I read recently that the Biden administration is temporarily allowing fuel to be 15% ethanol during this summer to combat high gas prices. Could it be that?

-bob

Add flex fuel kit and take advantage of the ethanol

 

[Lagos]

Ah, so what I found wasn't too far off.

I read recently that the Biden administration is temporarily allowing fuel to be 15% ethanol during this summer to combat high gas prices. Could it be that?

-bob

I'm usually not the type to take part in gas station conspiracy theories, but you might be right in this case. I know that the factory tune is supposed to be made with gas that had 0% ethanol. Hondata bumps this up in their 10% ethanol tune to add about 4-5% to the fuel trims. Maybe there is something to it, if more ethanol was added to the gas.

 

[Bob_L]

I'm usually not the type to take part in gas station conspiracy theories, but you might be right in this case. I know that the factory tune is supposed to be made with gas that had 0% ethanol. Hondata bumps this up in their 10% ethanol tune to add about 4-5% to the fuel trims. Maybe there is something to it, if more ethanol was added to the gas.

I love a good conspiracy theory as much as the next tinfoil heat wearing nerd, but I'm pretty sure this isn't one of them. Here's an article about it on NYTimes, plus a YouTube video from Bloomberg of the president announcing it himself.

-bob

 

[bbeem]

Ethanol is higher octane but less energy dense. Higher ethanol content makes you run positive fuel trim or lean. It's better to be on the rich or negative side and TSP OTS targets -2 for example not 0. Maybe it's trying to keep you rich at WOT and it's just a little fat.

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