S2kJoshh

So I have an AP1 with HKS exhaust, cold air intake, and high flowing cats. Not getting good gas mileage, hopefully the tune would help with power and MPG. What is the best tuning option for AP1? Looking for a plug and play type of tune. Opinions on this?
Thanks!

s2000Junky

The ecu installed in your car has a closed loop/open loop operation, meaning its taking in information and correcting your fuel tune in closed loop to maintain the most efficient target at all times no matter what breathing mods you do, but not in open loop. Closed loop is idle to generally less than 35-50% throttle opening. Ive observed it to be 35% in my 01 as the transition point, and would assume its the same for 00-03+. Point in telling you this, is so you can understand why a tune isn't going to do a damn thing for your mpg, how you drive the car will. OEM/Closed loop targets a 14.7afr which is the most fuel efficient. This again is from idle to at least 35% throttle opening, to where beyond this goes into a open loop/WOT tune which can be manipulated mechanically outside of your ecu influence. This is the area of your tune where bolt ons have a more direct effect on afr the engine sees, for better or worse. If your seeing worse mpg and not driving the car any different, then id assume your mods are worse breathing then stock equipment. The only sure deal on the mods you have done is the higher flowing cats (TP being better) but HKS is not know to be a power maker, some have even reported losses. CAI are not a sure deal either depending on what you got.

In a nutshell dont let someone in here convince you to invest a couple thousand in a full EMS and tune to solve your problem, I find more times then not tuners struggle to even meet a partial throttle tune half as good as OEM/closed loop, and your bolt ons are not offering you enough of anything to effect your open loop tuning to make an investment in that part of the tune either. Unless you have a maintenance issue or poor driving habits ie in open loop throttle a lot more then you have/need to be, mpg is going to be what it is. You certainly dont want to throw $1500+ at a EMS and tune to save you $15 a month in fuel. The math doesn't make sense and not sure about you, but I didnt buy this car as a commuter, its purely for fun, so mpg is secondary to fun.

freq

AEM V1 or what Junky said.

S2kJoshh

Thank you for the response I appreciate you taking the time. One thing I have noticed is that even shifting at 3k RPMS at most, I still get bad gas mileage. So I know for a fact it has nothing to do with how I drive it. The warning about throwing lots of money down on a tune when it won't help is helpful. Thank you again for that

s2000Junky

No problem, hate to think of someone going down that road for these reasons. I would focus on making sure maintenance issues are sound ie proper tire pressures. Proper NGK 7heat range plugs at proper gap, valves adjusted to spec, not sucking in a bunch of hot air from your "cold air intake", filter clean/flowing. IAC valve clean, brakes, wheel bearings not dragging, working properly/smooth. Diff and trans fluids have been changed at proper intervals etc. Just some things off the top of my head to keep mental note of, or anything else that may have changed with the car when you first noticed a stray form your typical fuel mileage such as modifications.

Miner2003

Was just reading some of the posts on your inquiry and just wanted to add some info. I have a completely stock 2001 with 58000 miles. Around home I obtain 23 to 25 miles per gallon; 55mph and below. I live in the Pittsburgh, PA region so there are mild terrain changes. I took the "S" to Birmingham, AL this summer and cruising at 75 mph I was receiving 30 to 32 mpg. I thought this was very satisfactory. I have not had the car tuned up at this point. Have pulled plugs and they look brand new.