Straight Pipe / Ebay Catalytic

[phoondie]

I was wondering of those people that have installed straight pipes, and used the vfaq to spoof their second o2 sensor or used aluminum foil to spoof it, what has it done to your gas mileage. I drive about 100 miles a day and would like to keep it the same or better. I would like to put in a straight pipe or one of the supposed cats from ebay that are basically straight pipes. but don't want to destroy my gas mileage.

Thanks

 

[Cs4g63]

I would try using the spacer method before messing with the wiring.
http://www.obdloggers.com/o2simulator.htm
I used this method when I had my 99.

 

[romeen]

I would try using the spacer method before messing with the wiring.
http://www.obdloggers.com/o2simulator.htm
I used this method when I had my 99.

Just curious how that one works. Does that piece thread into the sensor bung in place of the sensor?

 

[rcrullamas]

right now i have a straight pipe on my GST and i get about 270-280 miles on a full tank of gas, it all depends on how you drive your car and if its city driving or freeway. also the rear o2 sensor is connect to the exhuast system, if it isnt you will check engine light will come on

 

[Mikelb]

Ok, the second sensor serves the purpose of telling the ECU if the catalytic converter is doing its job (tattletale). It shouldn't hurt anything to remove that sensor, other than throwing a CEL. The simulator would eliminate the CEL problem.

The only problem is, if you have to pass emissions, and they look and see that you don't have a cat. If you're tune isn't good, then you might also fail b/c of emissions levels (depends on the extent of the test they do).

If you really want to run an O2 Sensor, buy something like the OBX high-flow cat.
http://cgi.ebay.com/ebaymotors/OBX-...2QQihZ007QQcategoryZ33629QQrdZ1QQcmdZViewItem

If not, then just get a straight pipe and a simulator and you'll be good to go.

This should not affect gas mileage.

 

[Cs4g63]

Just curious how that one works. Does that piece thread into the sensor bung in place of the sensor?

You thread the sensor into that piece than you thread that into the exhaust. I found that it was easiest to install the spacer on the sensor first than install everything in the exhaust. Its literally that simple.

 

[phoondie]

right now i have a straight pipe on my GST and i get about 270-280 miles on a full tank of gas, it all depends on how you drive your car and if its city driving or freeway. also the rear o2 sensor is connect to the exhuast system, if it isnt you will check engine light will come on

I drive mostly highway miles, a little in town. Do you excelerate hard from lights or do you drive like a (excuse the pun) old lady. I drive slightly hard, don't take off real slow. I like to get to speed pretty quick. anyway lets see if we can get this post back on topic and get back to the gas mileage subject if you put the straight pipe or ebay cat in. Thank you for posting what you have so far.

 

[Mikelb]

These guys (in '04) seem to think you'd be ok: http://www.dsmtuners.com/forums/showthread.php?t=155534&highlight=cat+gas+mileage

These guys in '06 reaffirmed that when they told a guy that his gas mileage didn't go down due to a racepipe. More than likely, it was his exhaust ground strap: http://www.dsmtuners.com/forums/showthread.php?t=219583&highlight=cat+gas+mileage

I was running 2.5" pipe all the way back on my 1G FWD (no exhaust strap) and getting about 18MPG... That was with really beating on the car (100+ on the daily)

I really don't see the Cat(or lack of) affecting your gas mileage. If you're really worried about it, find you a 3" high-flow cat. They're almost hollow, and offer the least restriction for a catalytic converter, while still remaining legal.

In short; no, a racepipe(testpipe) or ebay "high-flow cat" should not affect your gas mileage. Just be sure to keep the exhaust grounded (If running the second O2 sensor).

 

[phoondie]

Thanks, just didn't want to spend the money with gas prices going over 3.30 a gallon, and then get crappy gas mileage. The simulator sounds like a good idea. I think I will try the foil wrap first and see how that treats my car then if I have to I will get the simulator. Thanks guys and everyone have a great weekend.

 

[gorf]

I really don't see the Cat(or lack of) affecting your gas mileage. If you're really worried about it, find you a 3" high-flow cat. They're almost hollow, and offer the least restriction for a catalytic converter, while still remaining legal.

In short; no, a racepipe(testpipe) or ebay "high-flow cat" should not affect your gas mileage. Just be sure to keep the exhaust grounded (If running the second O2 sensor).

To clarify, I used a 3 inch magnaflow high flow cat. You can see clear through this cat if you hold it up to light. very little if any restriction, especially if your exhaust pipe narrows down to 2 3/4 inch at the flange, like most do.

I just passed epa inspection with it.

 

[Mikelb]

To clarify, I used a 3 inch magnaflow high flow cat. You can see clear through this cat if you hold it up to light. very little if any restriction, especially if your exhaust pipe narrows down to 2 3/4 inch at the flange, like most do.

I just passed epa inspection with it.

Nice to see someone from NC. In my '97 RS, I had a testpipe, and never had any problem passing. It never threw my CEL though, and that's why. I didn't have to pass a visual.

 

[Eastwood95]

I wouldn't even bother with the "FOIL" crap. What are you going to plug the hole in your exhaust with?

The o2 bypass mod is simple and effective for running a straight pipe. It won't effect your gas mileage and you can leave the o2 sensor in it's place.

The other "simulator" mod link that was given above also works great.

 

[wret]

I was wondering of those people that have installed straight pipes, and used the vfaq to spoof their second o2 sensor or used aluminum foil to spoof it, what has it done to your gas mileage. I drive about 100 miles a day and would like to keep it the same or better. I would like to put in a straight pipe or one of the supposed cats from ebay that are basically straight pipes. but don't want to destroy my gas mileage.

Thanks

I would try it without any modification first. I've got a couple thousand miles on a cat-elminator downpipe without a CEL.