Exhaust help (Part II)

[ClassySolaraGuy]

Once I replaced the muffler & stock piping which I believe is 2.25in (correct me if I'm wrong) the first time to the Magnaflow & 2.5in piping, I noticed a huge drop in MPG. Yeah...I know...Its from toying with the new sound but 235-255 miles on a full tank? That's using the odo reading. The computer says I'm getting on avg 16MPG which is just sad. I also noticed my RPM's during cruising.

Stock
80mph @ 2500 RPM
New Exhaust
80mph @ 2750 RPM

There are 53,000 miles on her & I know the following are in spec:

Tires: 225/50/17 Toyo Proxy4 @ 36.5psi. Stock tires are 215/55/17 with a diameter of 26.3in. The Toyo's are 25.9. Very close to stock.
Oil: Full Synthetic 5w30
Gas: Chevron Premium
Filter: K&N drop in (clean)

I would think it is the exhaust since the RPM's differ at speeds from before. Any idea would be much appreciated! There are times I almost what it back to stock because of it!

[Biggi_e]

hmm not so sure but ive been getting anywhere from 260ish-280 a full tank. maybe its the heavy lead foot i got and i use 93 octane..

[kwyse]

Increased piping size will let the exhaust flow more freely providing more power because it is possible to burn more fuel (less restriction.) So there should be a slight drop in miles per gallon. There was a thread in regards to the drop in mpg with the Greddy Evo catback for the gen1 guys.

As far as the different RPM's, I'd think that they'd always be the same for the same speed. Can't help u with that.

[Sebas007]

Since your tires are smaller on overall diameter size but it doesn't explain all the difference...In fact tire size difference explain only 1.77% almost nothing ! I don't what it can be too....I remember an other guy wit that kind of post...some months ago (maybe several months ago...)

[godshippy]

I have a 2005 with the L4 and I get about 400 miles on a full tank of gas. If you're experiencing a very significant amount of MPG drop then I suspect that the K&N air filter that you put in is the culprit. The oil from the filter is drawn into the intake and gets stuck on the MAF. This contamination will block the actual amount of air that is being brought into the intake as seen by the PCM, which will usually decrease your fuel mileage.

My suggestion, clean out the MAF VERY THOROUGHLY AND CAREFULLY and road test.

Also, drop back down to the stock size tire!

[gnegroni]

I have a 2005 with the L4 and I get about 400 miles on a full tank of gas. If you're experiencing a very significant amount of MPG drop then I suspect that the K&N air filter that you put in is the culprit. The oil from the filter is drawn into the intake and gets stuck on the MAF. This contamination will block the actual amount of air that is being brought into the intake as seen by the PCM, which will usually decrease your fuel mileage.

My suggestion, clean out the MAF VERY THOROUGHLY AND CAREFULLY and road test.

Also, drop back down to the stock size tire!

How can I clean the MAF? I think my K&N got a little bit too oiled the last time I put it back in, and might have gotten something clogged. Anyway, has anybody seen those Stainless Steel filters around?