Sorry if this has already been asked.

Has anyone noticed a delay from the time you push the gas pedal until the engine revs?

I heard it is because of the electronic gas pedal.  Also I have heard others have had it go away when they installed a programmer or cold air intake.

Do those mods void the warranty?

Thanks,
John
08 JK
Summit County, CO  

The lag you are feeling is not a function of the electronic throttle cable, but rather the calibration of the engine computer. If your Jeep is brand new (less than 1,000 miles or so) it is even more pronounced, the Jeep is still learning your driving habits.

Anyway, the factory computer provides this lag in different variations for several reasons.
1) As a way to preserve the drivetrain (especially important during break-in)
2) Better fuel economy
3) Cleaner emissions

A programmer will likely help alleviate the slight lag. It will also slightly increase overall power, decrease fuel economy and it is very likely that it will void the warranty if the dealer catches it. I'd also recommend that you wait until after the break-in period if you decide to go this route.  

What the programmer MFGs don't tell you in their advertising, that their recalibration of the timing and fuel maps requires premium fuel.

And if you don't use premium fuel then there are little to no gains in performance.

So, couple that with probably worse fuel economy and more expensive fuel on top of the cost of the programmer.

When looking at the performance data provided by the programmer MFGs, some even use 93 octane fuel to boast about their performance gains. Most states don't have 93 octane, and those that due won't for much longer.

Then they compare the 93 octane performance numbers with 87 octane performance numbers. Not exactly an apples to apples comparison.

One last point. Often the programmers tune your engine right up to the peak, which gives no margine for error in normal driving conditions. This peak performance can be detrimental to the O2 sensors and the catalytic converters. Then the ECM will start throwing O2 sensor and misfire trouble codes. And these will keep your vehicle from passing an emissions test.

The Jeep engineers purposefully back off the peak to provide you with the best in durability, drivability, performance and economy. They have your's and their best interests in mind. The programmer MFGs only have their intersts in mind.  

Is the same true for the cold air intake and cat back exhaust in running premium fuel and voiding warranties?  I know these products advertise hp and torque gains, but does the increased flow of air into the intake and the reduced back pressure cause the computer to rethink the parameters and put the engine into a premium hungry attitude.  Daily driving between 10 and 11K feet above sea level is sucking the grunt from my engine and I am looking to improve it with warranty friendly noticeable improvements.

Thank you,
John
08 Unlimited JK
Summit County, CO  

There are no secrets about engine performance and tuning.

You have to have faith in the Jeep engineers. They spend many millions of dollars in research, development and most importantly testing.

If it was really that easy, with only benifts to be had, don't you think the Jeep engineers would be all over it.

Two things to keep in mind. High RPM performance is at the expense of low RMP performance and your engine is the pump that moves the air.

High RPM, which helps in creating maximum HP is in direct opposition to low RPM torque and drivability. For the most part, you can't have both. The things that work well in a race environment, would be misserable on the street.

Your engine's current configuration has an airflow requirement. This requirement does not change just because you put on a bigger, more efficent air filter. Your stock air filter is already oversized for your engine's air flow requirements. So is the throttle body. These pieces are needed if you change your engines air flow requiremnets, but do nothing if you don't. The air does not flow by it's self, it's the engine that moves the air.

As for the header. Back pressure in the exhaust is part of the tuning that needs to be considered with cam profile. The current cam profile depends on the tuning of the existing exhaust system. When you remove the back pressure and don't address the cam profile, over-scavaging occurs.

Over-scavaging causes part of the intake charge to be sucked into the exhaust. This causes increased exhaust gas tempatures which harms the o2 sensors and overheats the catalyst in the converter causing it to break down and become ineffective or even plug the exhaust.

Over-scavaging also reduces the cylinder pressure at lower RPMs. And that is lost power. Headers make your engine breath better at higher RPMs. But, they actually can have a negative affect at low RPM.

These are the things that the Jeep engineers are trying to deal with. A whole bunch of compromises. They are smart enough to make 30 more hp in the upper RPM ranges. But, there would be a compromise.

The best, most enjoyable engines are "tuned" as a complete package. Without taking everything into account, your asking for irritations.

If your not happy with your performance now, you still won't be after you spend a bunch of money on stuff that will ALLOW more air flow but doesn't do anything to actually MOVE more air.

Turbos work, Superchargers work, and increased displacement works. Then you'd be happy with your performance.

One last thing. A gear change can also make a big difference in performance. That's where I would start if I wanted a little extra.  

That is the most thorough response I have ever received...haha.  Thanks.  This isn't a ungrateful response but an fyi......Mopar has cold air intake kits for the following.

Heat up your Jeep Grand Cherokee, Commander, Wrangler, Liberty and Cherokee with a steady flow of cold air. This bolt-on system is designed to allow cooler outside air in through a directional cone filter and funnel it directly into the intake manifold. These kits provide noticeable horsepower and torque gains under varying atmospheric conditions.

Kit includes all mounting hardware and a pre-oiled, washable/reusable filter. Please select engine above.

Item # 77060010 - 5.7L Engine (05-08 Grand Cherokee & 06-08 Commander) Replaces Item # P5153374
Item # 77060011 - 6.1L Engine (06-08 SRT8 Grand Cherokee) Replaces Item # P5153471
Item # P5153636 - 3.7L Engine (05-07 KJ Liberty) Replaces Item # 77060013
Item # P5007828 - 3.7L Engine (02-04 KJ Liberty)
Item # 77060021 - 3.8L Engine (07-08 JK Wrangler)
Item # 77060007 - 4.0L Engine (97-06 TJ Wrangler)
Item # P5007830 - 4.0L Engine (91-01 XJ Cherokee)  

It's very easy to sell things that don't provide any real benefit, if someone really wants the stated benefit. Everybody wants to loose weight, look younger and get more horsepower. Look at all the stuff for sale to address these wants.

Eat less calories than you burn, no magic pill or diet needed there. Increase your engines ablity to pump more air, no secrets there either. I think the verdict is still out on the looking younger thing...

Find the before and after performance data for your Jeep with just the cold air intake installed. If it really does "provide noticeable horsepower and torque gains under varying atmospheric conditions", then it should be easy to find.

But, you'll find irrelevant statements like "30% more efficient" or "stock intake is restrictive" or "more air equals more horsepower and this will give you more air".

None of those statements are incorrect. But how does it apply to your vehicle. Does it decrease your acceleration time or increase your mpg. You'll not find that data. If they could make that claim, don't you think it would be right upfront.

Remember your engine is the air pump. Anything that contains a filter and some ducting is "restrictive". But it can be sized to provide the engine's air flow requirement.

Notice the advertisements don't state the airflow requiremnets for your engine and then tell you how much the stock intake flows in order to make the claim that it is undersized and their's is correctly sized.

If you have 5 gallons of water to store and you have a 6 gallon bucket in which to store it, does increasing the bucket to 7 gallons benefit you. That's all your doing by buying a "less restrictive" intake setup.

Stu Olsen of Stu-Ofroad.com has done years of testing with cold air intakes. He found that they provide no performance gains, no mpg gains and in fact just allowed more fine dust into the intake than the stock setup.  

I do understand your reasoning and it seems you do have factual information to back it.  I myself do like to understand the why's and how's of how things work or do not work.  For the most part I am skeptical until proven otherwise and I am pretty analytical in my research.  The info from Mopar on the cold air intake was interesting to me.  I thought they might have identified an area where either they thought their engines could be better or may have identified a restrictive intake problem and offered a solution for those who had noticed it.

Thanks,
John
08 JK
Summit County, CO  

It's a huge money maker for them and everybody else who sells them.

The biggest money maker is the throttle body spacers. 80 bucks for a hunk of anodized aluminum. These have been shown in many test to have a negative affect on performance with port fuel injection.

These manufacturers state that the spacer helps with atomization of fuel. Funny thing is, there is no fuel in the intake of a port fuel injected engine. So, how could it help with atomization? These are left over from the days of throttle body injection when there was fuel in the intake. But they don't have any problems selling them for applications that have port fuel injection.

They're just money makers cause people want more horsepower.

They look cool and they sound cool. And for a lot of people that makes them feel like they're getting performance.

I actually read this on the internet somewhere. Some guy put on an intake system and actually said he could really hear the engine breathing better. A happy customer??

But, if you buy an intake system so that your Jeep has more performance at 10,000 ft elevation, and do nothing else to your engine to take advantage of the increased air flow capacity, you'll just have a pretty silver tube that no one will see.

Seriously, you will get some real performance that you'll notice and be happy with if you re-gear. Just going from a 3.73 to a 4.11 or from a 4.11 to a 4.56 would make a big difference. And I'll even give you a guarantee!  

Please, anybody that has an answer for this;

For a cold air intake, where does the cold air come from?

And why is this cold air not available without the cold air intake?

One of the Auto manufacturers did some testing with a little AC evaporator in the intake. It cooled the intake air temp by 40 degrees. That would represent a hp increase of about 4 percent. They found that the restriction of the air flowing through the evaporator nearly cost the entire hp gain potential. Seems like a really cool idea though.  

The idea I have always heard is that it isn't actually cold air, it is just cooler air than that of what a stock air box delivers and that cooler air creates better combustion along with the increase unobstructed higher volume of air.  I do not know how they come to that reasoning with most cold-air intakes being located in the same place as stock and most of the time with less thermal protection.....I dunno.  

Ftgiles,

I was curious about turbos and superchargers.  If an engine can not take in anymore air than it is designed for or can pump how do these two add-ons work?  I understand some who install these performance mods must also alter the way the higher amount of air is consumed but like you referred to it can only take as much air as it is designed for.

I am not challenging your feedback, I just do not know and am curious.

Thanks for your patience.  

There are two terms, normally aspirated, and forced induction.

When the piston moves down in the cylinder, it creates low pressure or vacuum. Atmospheric pressure will rush in to fill the low pressure area. Once the pressure is equal, no more air will flow.

So, at 100% efficient, meaning no intake obstructions (valves, ports, runners, throttle bodies etc), the physical capabilities for moving air is limited by the amount of air that the piston displaces while moving down in the bore.

Now, there are some things that you can do to obtain greater than 100% efficiency, but that is generally high dollar, race engine stuff. Stock engines are generally 75% efficient. Well built engines will be 90-100% efficient.

Efficiency is a technical term in physics used to express the losses involved with any mechanical device. These losses are mostly caused by friction and heat.

Forced induction, turbos and super chargers, change the efficiency, with regard to air movement, to something much greater than 100%.

They accomplish this by pressurizing the intake system to something much greater than atmospheric pressure. This increased pressure forces air into the cylinder as opposed to be drawn in.

Now you have more air, therfore you can mix in more fuel, and that produces more power.

So, in a nut shell, a smaller displacement, forced induction engine can produce the same power as a larger diaplacemnt, normally aspirated engine. This is because they both use the same amount of air and the same amount of fuel.

Always remember there is an optimum air/fuel ratio. And the energy to create the power is in the droplet of fuel. So in order to get more power there has to be more fuel. And if there is more fuel, there has to be the right ratio of air to mix in.

More air and more fuel equals more power.

Now in your case, at 10,000 feet above sea level, there is less atmospheric pressure to fill the cylinder than at sea level. So the efficiency of your engine is even less.

It's all about pressure and the laws of physics that state pressure must equalize.

Wind is the result of air moving from a high pressure area into a low pressure area.

When you walk through the door into a building and you feel your hair move, that is the high pressure inside the building rushing outside into the lower pressure area. The high pressure inside is created by the Heating/Air conditioning system.

Your engine is working the same way. Higher pressure equalizing with lower pressure.  

ftgiles...just wanted to say thanks, that was a very informative post!! Great stuff there!