Cherokee XJ Tune Up Parts List - Page 2 - JeepForum.com

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post #16 of 23 Old 07-27-2013, 07:59 AM
BS87
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Quote:
Originally Posted by DNFJ View Post

This is incorrect.
It's actually not. Warm air causes the ecu to run leaner and use less gas. You make less power for sure, but it does help mpg

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post #17 of 23 Old 07-27-2013, 09:47 AM
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Quote:
Originally Posted by BS87 View Post

It's actually not. Warm air causes the ecu to run leaner and use less gas. You make less power for sure, but it does help mpg
Less power = more strain on engine for the same momentum = more fuel used to gain speed.

Project ROLLplay
'00 XJ Locked on 35s

Previous:
'00 TJ 2" on 33" Grabbers
'00 XJ 6.5" on 35" KM2s
'96 ZJ 2" on 31" Baja Claws
'93 ZJ - Stock, Totaled
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post #18 of 23 Old 07-27-2013, 09:57 AM
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Put it this way

If an engine has 200 hp, and gets 20mpg. Let's say a warm air intake reduces power by 20% and increases fuel economy by 20%

This means you get 24mpg with 160hp.

Both going 60mph, engine 1 uses 3 gallons, at 2500RPM.
Engine 2 will use 2.5 gallons, but be at 2750 RPM, meaning extra fuel is being used to make up the difference in power that you've just given the engine.

So yes, you'll use 3 gallons of gas without an intake, and 2.7 with one, saving you a net of .3 gallons of fuel. How the hell is that worth it? I'd rather increase my engines power therefore reducing the amount of power I need to be at speed, and thus rpms + extra fuel costs for staying at that RPM.

Of course this is all subject to change with gears, tires, etc.

Project ROLLplay
'00 XJ Locked on 35s

Previous:
'00 TJ 2" on 33" Grabbers
'00 XJ 6.5" on 35" KM2s
'96 ZJ 2" on 31" Baja Claws
'93 ZJ - Stock, Totaled
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post #19 of 23 Old 07-27-2013, 10:32 AM
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With both going 60mph, unless it can somehow magically change the gear ratios in either the transmission or rear end, both engines will be turning the same RPM. Especially going that fast, because the torque converter would have long sinse locked up.

95' XJ Country - Stock Skids - D30/D35 Limited Slip - 3" Lift - 31x10.50R15 - 4.0 HO - AX15 - NP231

98' XJ Classic - D30/C8.25 - 4.5" RC Lift - 33x12.50R15 - 4.0 HO - AW4 - NP231
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post #20 of 23 Old 07-27-2013, 10:44 AM
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With both going 60mph, unless it can somehow magically change the gear ratios in either the transmission or rear end, both engines will be turning the same RPM. Especially going that fast, because the torque converter would have long sinse locked up.
My point is this (yes I obviously didn't do the best at explaining it last post, but I've been up for over 24 hours give me a break) If you need more power to maintain the same speed, (which you will because you've admittedly lost power by using a warm air intake), your "fuel savings" will be made irrelevant by the fact that it will take more fuel to maintain the same amount of power and thus the same speed.

Project ROLLplay
'00 XJ Locked on 35s

Previous:
'00 TJ 2" on 33" Grabbers
'00 XJ 6.5" on 35" KM2s
'96 ZJ 2" on 31" Baja Claws
'93 ZJ - Stock, Totaled
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post #21 of 23 Old 07-27-2013, 10:48 AM
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But that's just it, to maintain speed you don't need a huge amount of power. True getting up to that speed you sacrifice power and fuel economy, but to maintain it warm air intake would prove to be more economical.

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95' XJ Country - Stock Skids - D30/D35 Limited Slip - 3" Lift - 31x10.50R15 - 4.0 HO - AX15 - NP231

98' XJ Classic - D30/C8.25 - 4.5" RC Lift - 33x12.50R15 - 4.0 HO - AW4 - NP231
Quote:
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You can tell the character of a person in how they treat someone who can do nothing for them.
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post #22 of 23 Old 07-27-2013, 10:54 AM
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Quote:
Originally Posted by Holder350 View Post
But that's just it, to maintain speed you don't need a huge amount of power. True getting up to that speed you sacrifice power and fuel economy, but to maintain it warm air intake would prove to be more economical.

Sent from my phone
Unless you drive like a complete grandma and merge onto the highway at 35mph (if you do I hate you already), then the difference between the mileage you make up at maintaining speed and the fuel used to get up to the speed (especially if there's hills, etc) makes it largely negligible.

Project ROLLplay
'00 XJ Locked on 35s

Previous:
'00 TJ 2" on 33" Grabbers
'00 XJ 6.5" on 35" KM2s
'96 ZJ 2" on 31" Baja Claws
'93 ZJ - Stock, Totaled
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post #23 of 23 Old 07-30-2013, 02:28 PM Thread Starter
era86
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Thought I'd follow up. I have never worked on my own vehicle, so this seemingly short & sweet tune up turned into a couple of hours work! Nonetheless, I'm proud of myself for not blowing anything up.

Replaced spark plugs and wires.
Replaced distributor cap & rotor.
Changed oil and oil filter.
Reset the ECU.
Replaced air filter.

Is there any other low-hanging fruit any of you would suggest?
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