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@Array,

I didn't get an invoice... The tech actually worked on our KL until after much of the place had shut down, since it was all warranty, I just left... I'm sure it's documented though so I will get it.
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@IRSmart,

I think the issue is how the 3.2L's power comes on... I took the dyno chart from the AFE website, but you can see that it almost behaves like an old 2-stroke that hits a powerband. There are pretty drastic changes in the power it generates from 2000 RPM through 2400, and it makes little to no power at all at idle. Since the ZF9 has so many gears it is doing it's best to work with what it has but adding even the slightest of wind drags would force the power requirement up and this means dropping gears.

Now, the question is if a turbo or supercharger would help more (if we pretend one existed). A small quick turbo may be what the Dr. ordered, but IMO a supercharger and for low-end is what the KL desperately needs to make the most of that ZF9.


I know lots of people won't agree with me, but I know what you are talking about the drastic power increases from 2000rpm to 2400rpm, however I think that is a limitation on the tuning. Something is holding back the power below 2400rpm on these vehicles.
 

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Is this dyno on the engine or at the tires if at the tires the power reading show as the torque converter locks up
 

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Is this dyno on the engine or at the tires if at the tires the power reading show as the torque converter locks up
with a maximum power of around 200 hp, i am guessing that it's a wheel dyno. i don't really know of anyone outside of a manufacturer who dynos at the crankshaft.
 

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Discussion Starter #205
That would explain the steep curve at the bottom of the chart
It could... but most street automatics have a stall of at or just off idle. If we are seeing the torque converter still working to it's stall that means it would be around 2300-2400. That would be pretty crazy.
 

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... I took the dyno chart from the AFE website, but you can see that it almost behaves like an old 2-stroke that hits a powerband. There are pretty drastic changes in the power it generates from 2000 RPM through 2400, and it makes little to no power at all at idle.
Please enlighten me on what this chart is representing. How can there be NO hp below 2k rpm? What's going on when the KL is cruising at 1.5k rpm; perpetual motion?

And is this chart saying that hp and torque numbers scale in the exact same way?
 

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Please enlighten me on what this chart is representing. How can there be NO hp below 2k rpm? What's going on when the KL is cruising at 1.5k rpm; perpetual motion?

And is this chart saying that hp and torque numbers scale in the exact same way?
The test vehicle probably was controlled to Wide Open Throttle until just above 2,000 rpm.

There is nothing wrong with the scaling. The power and torque cross each other as expected at 5,252 rpm for units of hp and ft-lbs.

Sent from my VS995 using Tapatalk
 

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The test vehicle probably was controlled to Wide Open Throttle until just above 2,000 rpm.

There is nothing wrong with the scaling. The power and torque cross each other as expected at 5,252 rpm for units of hp and ft-lbs.
Thanks, now I understand. The hp/torque are represented by heavy/light lines. Missed that first time around.

Still don't understand the controlled-to-WOT part. Does this have to do with the vehicle being in 1st gear and not much twisting at the wheels until the engine got over 2k rpm?
 

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Cars are dynoed in the gear ratio closed to 1:1, on a six speed usually 4th gear. No clue of a 9 speed vehicle. Lets just say it is 5th gear. The vehicle is driven at the slowed speed to get it in 5th gear, and then WOT is applied. When this happens the engine is already at 1.5-2k RPM since it is already in motion. That is why dyno'ss really don't show much down below 2k.
 

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Discussion Starter #210
I'm not saying this is the most accurate dyno chart for the 3.2L... it was the only one I saw. I was just looking at the steep angle of how the power seemed to come on until the torque flattened out. If this dyno is accurate, it makes sense to me why the 3.2L/ZF9 gets so shifty and can't hang onto gears down low.
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I'm an old-school drag guy that knew my tuning was better by Thursday night test-and-tune time slips. I never used a dyno ;)
 

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Since this is going into dyno talk, I will add this. No dyno is accurate. They will give you a ball park number, but depending on the type of dyno, your numbers could be very different from one dyno to the other. Dyno's are really just used for comparisons. If you dyno a car on a dyno, mod it, and dyno again on the same dyno, then you get the ball park add of the part, environmental factors will throw these numbers off, that is why I said ball park. I know some people have dyno'ed a car in hot weather, 90+, and then dyno'ed again in 40 degree weather and got a gain in performance, all do to the weather changing. I know vendors like to do this to show bigger gains then actual.


Example, when I had my Evo, I only put down 200awhp on a dyno. Not very good considering it puts out 300hp stock, but again types of dyno's play into your number. I modded it and went back to that same dyno, and my car put down 240awhp. From that you could tell my mods increased my HP by ~40awhp. I really didn't care about the total number, I just wanted the gain. That same car went to another dyno and put down 319awhp. I gained 80whp just by changing dyno's. Man I miss that car it was fast.
 

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Back in my dyno days, the Mustang brand dynos always gave lower numbers than the Dynojets. I never used a Mustang dyno, but my Trans Am was run on three different Dynojets between 2001 and 2004, and the results were within a couple of hp each time.

If I recall correctly (and was told correctly), the Mustang dyno design applied a drag to the drum that was supposed to take into account the vehicle weight, but the Dynojet was only spinning up the drum's mass.

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Discussion Starter #214
10+ days, @SS_Syndicate. How's the fuel economy holding up?
Seems to still be better, but it's tough to tell. My wife's commute is pretty short so we are still on the same fill up from after our trip. Our little errands of late have been in our new toy. (I got my new 4runner)

For a few reasons.... we have opted to take the KL on the big overlanding trip in a few weeks. In prep, I plan to make an airfoil or wing to help direct the wind above the tent more efficiently on the trailer.
 

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I see two things that are hurting you with that trailer. First, a very non-aerodynamic piece protruding well above the roof height of your vehicle (flat plate being forced through the oncoming air) will cause much more drag than an aerodynamic shape of the same total surface area. The Coefficient of drag of a flat plate is 1. Any improvement in the leadedge shape will reduce that and improve your mileage.

Second, the empty space between your upper level and lower storage area on your trailer induces interference drag. Two bodies close together cause more drag than a single body of the same surface area because the airflow between them becomes turbulent and adds drag to both surfaces.

The third thing is your speed. While I understand your concerns about driving slower, the total drag increases exponentially with speed. Slowing down just 5 MPH, so long as that doesn't put you into a poor gear ratio range, will show a significant improvement, while 10 MPH may be dramatic.

Here's a good article on drag. Ignore the part about induced drag (which results from generating lift in an airplane), but pay particular attention to the paragraphs on FORM DRAG, and most especially INTERFERENCE DRAG. Understanding those two may help you improve on your trailer's design in relation to drag, and therefore gas mileage.

https://en.m.wikipedia.org/wiki/Parasitic_drag

My recomendation would be: since you designed and built the trailer yourself, either lower the top level closer to the height of your Cherokee, or add a vertical "V" shaped fairing to the front. If possible close the space between the upper and lower levels at the front of the trailer, and don't leave holes that generate turbulence, which increases drag. Good luck!
 

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Discussion Starter #216
I see two things that are hurting you with that trailer. First, a very non-aerodynamic piece protruding well above the roof height of your vehicle (flat plate being forced through the oncoming air) will cause much more drag than an aerodynamic shape of the same total surface area. The Coefficient of drag of a flat plate is 1. Any improvement in the leadedge shape will reduce that and improve your mileage.

Second, the empty space between your upper level and lower storage area on your trailer induces interference drag. Two bodies close together cause more drag than a single body of the same surface area because the airflow between them becomes turbulent and adds drag to both surfaces.

The third thing is your speed. While I understand your concerns about driving slower, the total drag increases exponentially with speed. Slowing down just 5 MPH, so long as that doesn't put you into a poor gear ratio range, will show a significant improvement, while 10 MPH may be dramatic.

Here's a good article on drag. Ignore the part about induced drag (which results from generating lift in an airplane), but pay particular attention to the paragraphs on FORM DRAG, and most especially INTERFERENCE DRAG. Understanding those two may help you improve on your trailer's design in relation to drag, and therefore gas mileage.

https://en.m.wikipedia.org/wiki/Parasitic_drag

My recomendation would be: since you designed and built the trailer yourself, either lower the top level closer to the height of your Cherokee, or add a vertical "V" shaped fairing to the front. If possible close the space between the upper and lower levels at the front of the trailer, and don't leave holes that generate turbulence, which increases drag. Good luck!
You are a little late to the show but I appreciate your efforts...

The tent on the trailer has to be where it is for several reasons. If it were able to be lower I would gladly lower my GOG. Remember, this trailer is used with several vehicles. This is actually the whole point to having the trailer. We use several vehicles depending on how far and the type of terrain we are covering. My large complaint (and foundation for this post) was that it caused such a drastic change with the KL yet only yielded small losses when towing with other vehicles. I don't want to drone on about these other vehicles, but trust me.... there is absolutely no reason they should perform more economically than the KL, Especially given your drag argument.

Since our firmware updates we have seen some economic improvements. (A measured 3-5 MPG, and vehicle calculated 2-4 MPG, improvement). This puts us in a realm where I really don't have an argument anymore. This said... Jeep still has a ton of work to do when it comes to economy. Our KL really should be our highest economy vehicle and it isn't. Compound this with the rather limited fuel capacity and Jeep missed the mark pretty big given the demographic they are targeting. (Explore.... but don't get to far from the pump, LOL)

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Discussion Starter #218
I know some would rather see this thread go away... but I wanted to make one last update.

We just wrapped up our overlanding trip which was just over 4100 miles. This included a an interstate blast to the area and home but had about 1200 miles of gravel/dirt roads and trails in the middle.

Our fuel economy was all over the place but even the worst tank was far better than we had prior to the transmission update and AFE intake.

Keep in mind, we were MUCH heavier as well. We were packed for 11 days (food, water, everything). While we did need to stop for fuel, we also had 13.5 gallons extra we were carrying.

Our worst economy was 12.7 MPG. This happened twice and both times I was on the interstate going 72 into a STRONG head wind. Over the whole trip we averaged 15.9 MPG. One thing I found interesting was the KLs love of altitude. We had two tanks where we were in mountains and stayed between 6500 and 11000 feet. In spite of the fact there was lots of ups and downs, we averaged over 18.5 MPG!

Over-all I am pretty pleased with this.
 

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I know some would rather see this thread go away... but I wanted to make one last update.

We just wrapped up our overlanding trip which was just over 4100 miles. This included a an interstate blast to the area and home but had about 1200 miles of gravel/dirt roads and trails in the middle.

Our fuel economy was all over the place but even the worst tank was far better than we had prior to the transmission update and AFE intake.

Keep in mind, we were MUCH heavier as well. We were packed for 11 days (food, water, everything). While we did need to stop for fuel, we also had 13.5 gallons extra we were carrying.

Our worst economy was 12.7 MPG. This happened twice and both times I was on the interstate going 72 into a STRONG head wind. Over the whole trip we averaged 15.9 MPG. One thing I found interesting was the KLs love of altitude. We had two tanks where we were in mountains and stayed between 6500 and 11000 feet. In spite of the fact there was lots of ups and downs, we averaged over 18.5 MPG!

Over-all I am pretty pleased with this.


I found that weird myself. High up in the mountains running on 85 octane I can get really good gas mileage.


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At altitude:
Less air = less fuel mix = better MPG..... also = less power

Better MPG's is assuming you don't floor it everywhere to compensate for the lower power available
 
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