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Discussion Starter #1
My car club had a dyno day yesterday, and I came away very confused.

I have a 2014 R/T, with a volant CAI and was only able to put down 308 hp to the rear wheels. A totally stock 2014 R/T dyno'd at 334 hp, and a 14 Challenger R/T with a volant CAI (same set up as mine) dyno'd at 338 hp. Another 2014 Challenger R/T with a Mopar CAI was able to dyno at 345 hp. We are all stock except for the addition of a CAI

What would cause my numbers to be roughly 10% lower?
 

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Every dyno is different and will give different readings, therefore they are only useful to compare before and after modifications. Do you have a tune installed, bad tank of gas, car in a poor state of tune, dirty clogged air filter, do you have a lot of mileage, etc. It could be almost anything, and every engine is a little bit different.

Dynos are only useful to track the progress of your mods, so pick your favorite dyno place (and only go there) and have the car tested in stock condition. Then when you add a mod have it tested again to see if it actually helped or hurt performance.
 

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Discussion Starter #3
These were all dyno'd on the same dyno, on the same day, one right after the other.
 

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Challengers always seem to get higher numbers. I've seen the same thing before. My guess is the parasitic loss is less for the Challengers some how.
 

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Maybe you got a Monday car and they got Friday cars :dunno:

Yeah dynos are only good for doing a baseline, modding then dynoing again to see the increase (really only even consistent if it's the same day and temps at the times of both pulls).
 

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A good dyno shop will correct for temperature, air pressure, density altitude, etc, so it doesn't matter what day you go, just as long as you keep going to the same place.

I'm wondering if the type of dyno that was used reads differently because of the rear axle ratio. I've seen one or two dynos that will show a car with 3.90's making a lot more power than a car with 3.20's....might be the difference in the OP's 1st post..2.65 vs 3.06.
 

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Gear ratio won't change peak HP or Torque. It only changes at what speed it occurs. As a general rule, higher ratio gears experience slightly more parasitic drive line losses.

The variation between the other cars seems normal to me (334-345 HP). Pulling a 308 HP is out of trend. This is most likely a result of the PCM pulling power due to KR. This is generally the result of fuel quality but can also be due to spark plug fouling or poor A/F ratio.

Since the dyno is done at WOT (open loop operation) the PCM runs on pre-programmed tables so the adaptives won't come into play...but knock retard will.
 

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I would not worry about it!!

My car peaked out at 372hp and 357tq with my mods. Now compared to other inertia motorsport cars with my same mods I should be around 395hp and 400tq......Yet I am not but the car runs 12.4x....so the track is the true test dynos are just for numbers and baselines

An example my buddy Bob runs a 05 300 and lays down more on the dyno but only runs a 13.3x...very simiiar set up but completely different dyno numbers......Its just a tool
 

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... As a general rule, higher ratio gears experience slightly more parasitic drive line losses.
I knew there was some reason lower gears showed more power, I just couldn't remember why, thanks for the explanation.
 

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Discussion Starter #10
Pulling a 308 HP is out of trend. This is most likely a result of the PCM pulling power due to KR. This is generally the result of fuel quality but can also be due to spark plug fouling or poor A/F ratio.
I was wondering about possible KR after the dyno run. If it had a lot of KR would that cause the dyno graph to look squiggle vs. smooth. The dyno graph looks more like an EKG readout than it does a smooth powerband. The A/F ratio looks to be a 12 on the graph.

I'm using Chevron 89 octane fuel. Guess I'll need to do some data logging.
 

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Discussion Starter #12
Actually I had not added extra fuel for the CAI when I went. I wanted to get a base line prior to adding fuel. I've read where most people are adding 5% fuel to compensate for the CAI, but will adding fuel make up for the 10% hp lost to a stock car?

The dyno I use is the same guy I've always used. Trying to set up another appointment with him, to set up a totally stock baseline, and then reintroduce the CAI and tune from there.
 

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I just had mine on the dyno yesterday. The best results came with +5% fuel added at WOT in the low and upper rpm ranges, and +3% in the mid range. The 91 tune fattened up the torque from 3500-5500 nicely.
 

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The ugly truth is, your car just made less power than those other ones. Look for easy mechanical issues to correct, such as dirty parts or wrong fuel.

If nothing jumps out at you, those other cars might have custom tunes or some other modifications, because 307rwhp out of 370 crank hp sounds dead on the money to me.
 

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The ugly truth is, your car just made less power than those other ones. Look for easy mechanical issues to correct, such as dirty parts or wrong fuel.

If nothing jumps out at you, those other cars might have custom tunes or some other modifications, because 307rwhp out of 370 crank hp sounds dead on the money to me.
Yes it is, almost exactly a 17% loss, which can be accounted for due to normal drive line losses. Is your engine bone stock?
 

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Discussion Starter #16
At the time of the dyno it was all stock except for the volant CAI. Since then I've gone back to the stock air box, and am trying some different fuel. I'm going to run a few tanks through and then redyno it. I've gotten over the initial shock of the day and have come to accept the numbers I got, and will work from there.

The night before the last dyno I did do the quick math and figured it would be close to 300-310hp. I used a high 20% parasitic loss figure. When I saw the other completely stock cars pulling 330-338 hp power, I have to admit I was a little excited, but you're correct mine dyno'd at what a stock 14 Charger should.

Krautmaster...with you bumping up your fuel levels, are you running an aftermarket CAI? If so, which CAI are you using.
 

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Discussion Starter #18
Looks great Krautmaster. Thanks for sharing.

I've read lots of posts and it appears that most people are adding 5% fuel for the CAI. Does any fuel need to be added for the stock air box, or is the 91/93 canned tunes set-up for that, and the fuel setting are already within standards?
 

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The computer will adjust for fuel based on what the oxygen sensors tell it to do, and it tries to keep the fuel ratio as close to lean as possible, so it adjusts itself nicely.

When you kick it wide open, the computer goes into"open loop" mode where it reverts back to a preset mixture that is richer. With most CAIs, the airflow is greater, so the engine needs more fuel to compensate, and it needs more than the preset program provides, so we add 5% to start with then data log to see if it is enough or too much.
 

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The 02's in our cars are not wide band and do not play a role in Afr. They are their to monitor efficiency of the catalytic converter. Afr is adjust/maintained by data from the map sensor and a few other things like load, tb position, rpm, coolant temp...just to name a few. The logic in a map system is pretty complex compared to a mass air flow system
 
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