Interesting thread. For me, performance means more than burn out type performance. Remember, pro racers tear their stuff apart all the time & those machines are time consuming to maintain due to running near the limits. For me, I go for things that will give some power increases but also increase the mileage also. I use zmax additive & no other. I have ngk iridium plugs. In iowa where I live, no smog test so I removed the cat & replaced it with straight pipe. I do have a flowmaster 40 muffler & it sounds real nice. I also did an upgraded intake with high flow air filter. For me, that was stage 1 for my budget. Next, will be headers & a y-pipe. I have used various programming chips in the past & they are just ways of advancing the timing some. That helps performance yes, but can decrease the lifespan of an engine in my experience. It reduces the lifespan somewhat depending on how much you hammer it. If you don't mind working on it more, then the chip option along with turbos are okay, but not something I will ever use again. I have been told by pro racers that forced induction usually works best if you reduce the compression of your engine first to increase reliability, but that also means you have to use higher octane fuel and means much worse mileage as a trade off. I have owned a few supercharged factory cars & had customs with turbo set ups. They were fast for sure, but man I nearly went broke keeping gas in them. Higher octane fuel burns off faster, plus a lower compression motor gets worse mileage anyway. Not good if you have a budget. I only say these things like this because I have seen some enthusiasts get tired of poor mileage & sell their truck off for something smaller, without knowing that some of the mods they did really tanked the mileage to start with. I do like a lot of what I read in this thread so far though.

 

Glad I am not really worried about my gas mileage, I mostly just drive my truck to work which is only 2 miles away, other than that I drive it locally around town a little

 

I love driving my truck but I think its a downside I only drive 2 miles to work

 

Removing the cat and replacing it with a straight pipe will do what?

 

Prevent the added exhaust cleaning provided by the cat and break federal emissions equipment requirement laws in the process.

It will also eliminate one potential source of exhaust flow restriction and that's why you see all the outlaws on here gut or remove the cat.

 

yup.

chips? or programmers? Chips don't do a thing but temporarily deceive the PCM.. their benefit is gone in a matter of miles.. programmers, on the other hand, work.

advancing timing does nothing to reduce engine lifespan, unless you are using some sort of device to deceive the PCM... for instance: by deceiving the PCM, it may advance timing when it is dangerous to do so.. that could make a 'ping'.. pings definitely reduce engine life. If you are using a programmer, and have supporting mods to 'safely' advance timing, the PCM will allow such when conditions are right.. and it won't hurt engine longevity..

forced induction is just that.. cramming more air in the engine than it is capable of pulling on it's own.. compression isn't in play as much as what is implied here.. a lower compression engine has less compression because the head space is greater.. It's a mechanical thing, plain and simple.. cram more air in there than what is naturally pulled in, and pressure increases.. higher octane fuel is used for one reason and one reason only: to more positively control when it blows up.. the chemicals and compounds we call octane has a singular purpose- to be inert, meaning, harder to ignite.. meaning, it is less likely to go boom before spark is applied.. with a compressed load of a/f in a forced induction engine, pre-ignition (aka ping) can be catastrophic..

no, it doesn't burn off quicker.. you're confusing higher octane with higher alcohol.. lower compression engines produce less power per equal volume stroke than higher compression- but the forgiveness factor is much greater. it's simple physics: an equally charged explosion in a smaller container will expand rapidly with more power per square inch... lower compression=more head space=less powerful explosion, higher compression= less head space=more powerful explosion- if we're talking equal displacement engines.. the opportunity for something to snap in a higher compression engine is much greater than that of a lower compression engine, but the higher will out perform it every time..


I'm not trying to be a jerk, I'm just passing accurate information so as not to create confusion..

on a well maintained engine, and one well tuned and with all sensors operating properly, advancing the spark via alterations in the PCM is safe as can be.. tricking the computer (via 'chips') is a good way to get an engine to damage itself not knowing any better..

 

"Higher octane fuel burns off faster, plus a lower compression motor gets worse mileage anyway".

Just wanted to underscore what Drew said. It seems to be a very common misconception that high octane gasoline either "burns better" or "faster" or will make an engine that runs well on low octane somehow go faster (not saying you said the last one). Just as Drew said, it burns more slowly/less readily, to control the combustion in a higher-compression engine, or a lower-compression engine with forced induction (turbo- or super-charged).

Speaking of turbos, they don't necessarily reduce gas mileage significantly, or at all; I think the trick is to not drive the car like you stole it.

 

Turbos usually have lag, which means one must romp on it to get higher up in the power band. That is why turbos sometimes get poor mileage.

As for the high octane gas, my truck does better with it, and I get a 2 mpg increase on a tank.
I'll take that

 

that turbo lag everyone talks about is a condition created by bad tuning, or the wrong turbo for the application.. if done right, lag is so slight you won't notice it at all.

 

I think turbos are getting unduly slammed here, both for fuel economy and lag. Gasoline engines are about 30% efficient; the energy that doesn't get put to the ground is wasted as heat. Turbos use some of that heat to power the engine, and also move the power band farther down so the engine turns fewer rpm's at a given speed (you can be in a lower gear).

Chevy is coming out with a new fuel-efficiency car that will have a 1.4 turbo and a six-speed manual:

"Chevy Unveils 2011 Cruze Eco; Turbo Compact Gets an Estimated 40 MPG Highway"

Chevrolet today revealed the 2011 Cruze Eco, a high-efficiency compact model featuring a 1.4-liter turbocharged Ecotec engine generating an
estimated 40 miles per gallon on the highway, at the 2010 New York Auto Show.

The model achieves that fuel economy when fitted with a six-speed manual transmission, Chevy spokesmen said, adding that the Cruze Eco is
expected to deliver the best fuel economy in the compact segment.

Cruze Eco's 1.4-liter Ecotec turbo is said to perform like a larger engine when needed, but retains the efficiency of a small-displacement four-
cylinder in most driving conditions; it is standard on Eco, LT and LTZ models.

http://www.autoobserver.com/2010/03/...g-highway.html


And an interesting article from Autospeed.com:

"Having driven both engines [2.0 liter turbo and non-turbo VW] on the road in recent times, the turbo engine is massively better – and in fact in
freeway travel, we scored an even greater fuel economy win to the turbo engine than the above official test figures show....

But if we’re chasing fuel economy rather than performance, wouldn’t it make more sense to use a smaller engine and then turbocharge it to
match the performance (but not the thirst) of the larger naturally aspirated engine? With another engine, the 1.8 litre turbo TSI, that’s exactly what Volkswagen/Skoda have done ....

Modern engines using well matched turbos and other technologies like direct fuel injection are capable of exceeding the performance of larger
naturally aspirated engines across the full rev range – from just off idle all the way to the redline. Their immense bottom-end power and
intrinsically higher thermal efficiency also allows them to develop much better real-world fuel economy. As turbocharging is a technology
already well developed and understood, expect to see a lot more turbocharged, downsized petrol engines performing for all the world like big
engines – but without the thirst and emissions production.

http://autospeed.com/cms/title_Turbo...1/article.html

And a bit about lag:

"Turbocharger manufacturers continually improve their turbocharger systems and introduced new technologies. Although turbo lag is not
completely eliminated, it’s effects has been compensated by the introduction of the new technologies that can increase throttle response time in
turbocharged engines to the same level of naturally aspirated engine".

http://turbochargersworld.com/7-meth...uce-turbo-lag/

Lastly, I have my doubts that an engine that runs well on regular will get better mileage on premium. I just don't see any physical reason for it. Anyone?