Performance mods for better mileage??

[swoody]

I have been thinking quite a bit lately, and still seem to be on the fence about this. I'm trying to figure out whether or not doing 'performance' mods to a car will yield better mileage. I'm not talking anything extreme here, just a couple simple things like replacing the intake or exhaust with an after market, high-flow version. I'd imagine the weight savings of a nice aftermarket mod would help us out a bit, but how about the extra performance itself? Would that wind up eating through more fuel, or would the extra power allow you to lessen the amount of work your engine will have to do? Any input would be greatly appreciated on this! I'd really like to hear your feedback - especially if you have done any kind of 'performance' modifications, and what it's impact was on your mileage. Thanks in advance!

Woody

[SVOboy]

Since your engine likes to run at a 14.7:1 air fuel ratio, extra flow would mean extra fuel. Extra fuel != good

[blueflame]

Economy japanese vehicles from the 70's oil crisis had really short headers and sometimes even 3/4" exhausts!

Answer is no to pod filters and free flow exhaust. Air restriction before and after helps economy by increasing torque and reducing HP. Forget the K and N ads re helps economy. Its crap.

[swoody]

Ah, well thanks for the quick replies guys!

So would it actually be better to choke my intake a little bit? Maybe by covering part of the air intake with some duct tape? Or possibly make a custom cat-back exhaust out of something smaller than OEM sized piping?

What about the weight issue? Would replacing the OEM muffler with a light-weight one be a good move? Possibly with a smaller pipe leading up to it?

[SVOboy]

People have experimented with choking the intake. I would experiment for yourself!

[Tygen1]

I prefer SVOboys responce over Blueflames responce. Although I'd really like to see some hard evidence vs. someone just saying it's crap, I haven't seen any evidence from anyone not selling something. In my expirience, pre-scangauge so I wasn't able to quantify it, the performance mods did not hurt my mpg, it pretty much stayed the same, much to my dismay However I did gain plenty of midrange torque which might help the pulse's, but I really can't say for sure. I have been able to drop more than 2 seconds off my quarter mile time all while bringing my mpg on my commute from 27-28 to around 42-43 currently. I've learned that the return on investment for performance parts for mpg is not good, especially compared to the ROI for aeromods, which dramatically help mpg and performance for cheap.

[tjts1]

Ditch the power steering, ditch mechanical fan, add the largest forward facing cold air intake you can fit. All improved both fuel economy and power on my cars.

[Christ]

True performance mods will not increase your economy, although they will increase your efficiency. Confused yet? Good!

In all seriousness - "performance" mods are geared toward high-RPM performance. Anything you can do to get more power from your engine without introducing more fuel, or increasing pumping losses, in the RPM range that you're normally operating with, will increase your economy. I.E. Any kind of engine load that ISN'T moving the car. Such as the alternator.

[silicon_toad2000]

As most people have touched on, it depends how the performance mod works. Any performance mod which works by reducung the load on the motor will help mpg eg electric fans, underdrive pulleys.
Tuning Mods which make the most of what you have, such as ignition advance curves, mixtures can definately help provided the guy doing the tuning knows thats what you're after.
Rebuild mods which help performace will certainly help mpg, such as increasing compression, balancing and lightening reciprocating and revolving parts, some smoothing of the head ports (although some turbulence in the intake is beneficial to keep the fuel mixed in)
As far as gas flows through the engine, it get s bit more complicated. Smooth airflow will help mpg, the biggest challend is getting the volume of tract correctly matched to where you want the engine to perform the best. Most of us want the best at normal cruising rpms.
In the intake and exhaust, the inertia of the gasses help the engine, particularly the exhaust side. asside form the sonic scavenging effects in tuned length extractors, there is also the kinetic energy built up in the moving exhaust which want to keep moving after the valve closes, this creates a low pressure ready for the next time the valve opens. If your exhaust is too large, the gasses won't have enough velocity and inertia to use this effect.
But really to get down to this stage, you'd need custom cam grinds to make the most of it all aswel.

[blueflame]

Originally Posted by Tygen1

I prefer SVOboys responce over Blueflames responce. Although I'd really like to see some hard evidence vs. someone just saying it's crap, I haven't seen any evidence from anyone not selling something. In my expirience, pre-scangauge so I wasn't able to quantify it, the performance mods did not hurt my mpg, it pretty much stayed the same, much to my dismay However I did gain plenty of midrange torque which might help the pulse's, but I really can't say for sure. I have been able to drop more than 2 seconds off my quarter mile time all while bringing my mpg on my commute from 27-28 to around 42-43 currently. I've learned that the return on investment for performance parts for mpg is not good, especially compared to the ROI for aeromods, which dramatically help mpg and performance for cheap.

Darin did a stock air filter vrs K and N vrs no filter and got almost no difference, I think the stock was slighly better for FE. I think the comprehensive test is somewhere here or on his Metro site...

I dont like my response either so at least we can agree on something

Maybe if you lower the suspension and get wide wheels to go with the pod and exhaust....