I recently put on a set of Apexi N1 Duals, and ever since, I've been getting pretty bad mileage. Granted, 90% of those miles were put on in city, but I only managed to get 175 miles out of a 15.8 gallons. Before, I would be getting close to 280 with that amount of gas in city driving. Is the car just running too rich (since there's a weird smell coming out of the exhaust)? And if so, how do I get it to run leaner?

 

lol your just boosting more

 

It's an n/a. Any other ideas?

 

Is your exhaust maybe clogged in the cat or something? Were you driving it normal?

 

i only get about 150 with city driving and i have the same exhaust as u. even with my old stock exhaust, i still get the same amount.

 

Something is wrong with the car. Perform a full tuneup. Test the engine coolant temp sensor per FSM instructions.

Is the O2 sensor connected? Won't make a huge difference but will make somewhat of a difference.

 

I am happy to get 220 miles to a 15.8 gallon tank. granted a heavy SP and aux bridge probably isnt helping....


BC

 

sounds like 13b syndrome, similir to downsyndrome, takes more thought to express your self

 

The engine coolant temp sensor can ruin your gas mileage? You learn something new everyday. BTW my '90 GTU got amazing gas mileage and it had a fuel leak. I drove from salt lake city to denver (550 miles) on a single tank.

 

175 miles to the tank is how much i usually get. might change the coolant temp sensor,hmm

 

I changed my temp sensor because the engine wasn't revving to 3k rpm on start up. Had no idea it effected mileage.

 

175 miles? wow that's some pretty bad gas mileage!

 

yea idk wat it is

 

It's weird, I used to get around 275 miles before I swapped out my mufflers. Maybe I eff'd up somwhere? Hard to imagine 100 miles per tank being lost just because of new mufflers.

 

The ECU uses the ECT to tweak the fuel curve as the engine warms up. If the ECU thinks the engine is cold, it will be hosing in a lot more fuel then it needs.

In general most fuel mileage problems boil down to a few things (in this order):

1. Driving style too aggressive
2. Car out of tune (just regular maintenance)
3. Faulty component (sensor such as ECT or dirty injectors)

 

That's interesting Aaron...my GTU with no CAT ( just a muffler ) get's about 200miles to the gallon in the city. Also I had a dumb question, but should i get a cat re-installed on the car or just let it ride as a straight pipe?

 

^^^

1) If you're already getting 200 miles/ gallon I wouldn't change a DAMN THING

2) Your car sounds fine the way it is, so leave the cat off and save some $$$

3) I demand a new sig w/ updated wheels!


Slightly more on topic, I get 175-200 miles per fillup (10 gallons) all city driving (turbo)

 

HAHAHA shut up JP... I meant 200 miles on a full tank.

 

I am going to say the O2.

I assume your new mufflers allow more flow than stockers. I think it a sensor related to exhaust. being thats all that changed.

 

The O2 sensor does very little on these cars. It only operates in open loop mode (cruising), and even then it doesn't do a whole lot. As Aaron said, it doesn't do much, but it can add to other problems. This is something more than just a bad O2 sensor.

 

i called the guy from my shop and asked about the ECT. he said theres 2. one for the gauge and one for the ECU? should we replace both?

 

There's no need to replace the sensor for the gauge. If you want to replace the sensor for the ECU, it is located on the water pump housing underneath the alt. It has a green colored connector. I'm curious how the CTS would fail at the same time the exhaust was replaced, unless it were pure coincidence. You can't help but figure into the equasion the fact that you are likely driving more aggressively with the new exhaust, I know I would, to see how much more "kick" the engine had afterwards.

 

ECT will defiantly run your mileage into the ground. ECU sees that the engine is cold all the time, and it dumps in a LOT of fuel.

A new one is $40 or so from Mazdatrix - not too bad.

 

I get just about 10mp/g

stock everything besides exhaust and a cone-filter.... oh, and a Walbro...

:/

on my N/A ECU and the folks say it's good(which they're the only ones to confirm that)

I try the 'redline' remedy to clean the injectors etc. but it doesn't seem to help really(I redline twice+a day...)

 

where on mazdatrix site is it? i cant find it