My new FR-S!

[serialk11r]

Originally Posted by wdb

Those are interesting experiements but speaking for myself I think I'd last about 2 tankfuls before saying "too much hassle!" and just filling up at a single location. (Although it might be a fun way to amp up a tank for the STi, hmmm....)

Hahaha, well, the fact that these cars are known to ping a little on 91 is a good motivator to put the E85 in there, plus the direct injection makes ethanol contribute disproportionately to knock resistance so I can even save money by adding E85 to 87 or 89.

So unfortunately my test results aren't looking good, I was driving a bunch yesterday and noticed my instant mpg meter reading quite low. At some point I decided there was no way there was a headwind the whole way since even drafting another car I couldn't get it to go over 42mpg on the exact same stretch of road where last time I hit 41 cruising. It's possible that the lower ethanol content is reducing efficiency as my tank is now under 20% ethanol, but if my theory was working correctly I feel like I should still be seeing a net increase not a decrease.

Gonna drive on the map with no exhaust cam changes to see if it does any better.

[Daox]

I was just updating the wiki with some new car info. I've been wondered how you so easily got up to 41 mpg (yes I know with tuning), but then I punched in the aero info for the FRS and wow it is actually really good. It has an estimated cda of only 5.57. It is actually #6 on our list of production cars!

Also, make a fuel log!

[serialk11r]

Hahaha I've been procrastinating on the fuel log because I really don't want to keep track of E85 vs. gasoline...I'll run this tank down to empty and do a full tank of 91 to keep the "accounting" easier. With a consistent gas/ethanol blend a fuel log should be a little easier.

Today I drove to work on the modified intake timing map, and results were good! 60mph cruise was averaging around 42.5mpg. I tested 65mph and the mpgs were still pretty good at about 39.

I then put the cruise control at 70mph and the mpg plummeted to a tad over 36 I took a glance at the MAP reading and unfortunately it had gone down to only 7.5psi despite the 0.4g/rev load (for comparison, it was around 7.5 at 60mph when the load was just 0.33g/rev). I may need to dial the cam back a little to allow more EGR flow at 3000rpm. Need to think more about this...

Speaking of aero, this car actually has quite a bit of room for improvement. A bellypan and diffuser would drop the drag another 10% or so, the ride height could be lowered a little more, and the mirrors are HUGE, but I'm probably going to sell the car after a few years so might as well keep more things stock.

[Daox]

I'd just log it all as fuel. You can say what you filled up with or just the total amount, at least there is something in the log then.

[serialk11r]

This tank is half gone, so I'll start logging in a few days.

In the meantime, the trusty (or not..) dash mpg display said I got 42mpg average on the way home the other day 60mph cruise on rougher pavement yields about 40-41, smooth pavement gives 42.5ish. Parking in SF brings the tank mpg down a lot though.

One thing that's not so good about this car is that the efficiency of the engine drops off very fast at lower rpm. I can cruise at 60 and get 42mpg, going down to 50 only brings me up to 46, going down to 40 brings me up to 50, and then somewhere around 1500rpm (like 36 ish) the mpgs actually start dropping if you try cruising in gear. That means at lower speed I have to pulse and glide in 4th, sometimes 3rd, which I still haven't gotten used to.

[gizzardgulpe]

Thank you for putting so much of this information down. I've been wanting an 86 for a year or so now and I wanted to do exactly what you're doing. Unfortunately, the added cost of buying a car and insuring it would quite outweigh the savings in gas for me. It'd be great to go from 26 to 42 mpg, but I don't have any monthly payments on my old Toyota.

Down the road though, there's a good chance I'll be referring back to this for my setup.

[serialk11r]

No problem! Yea these cars are kind of expensive right now. I think in a few years time a used one would be a pretty attractive daily driver option. Honestly, when I drive this I'm constantly reminded of the fact that it's kind of questionable value as just about everything on the car makes some rattling noise, especially the gearbox. It's just nice to have a newer engine which doesn't have weird VVT lag (cable throttles do that), gets good highway mpg, and warms up quickly and stays warm for a while, plus has a minimal history of possibly questionable servicing so I decided to just pay up.

This tank was doing okay in terms of MPG until today, when it got completely murdered while I was looking for parking in SF for...1 whole hour -_- Doing diligent engine off coasting to try and save this tank's average lol.

[gizzardgulpe]

The rattling concerns me. I helped my mother-in-law shop for a new car and we both spent a lot of time on Consumer Reports. The 86/BRZ/FR-S has a below average reliability rating. I kinda figured it was because it's a sports car and people will drive it hard and hence premature wear, but if that's not the case, I would be much less inclined to buy one.

I've only been to the bay area once about ten years ago. My cousin had a motorcycle and made it sound like it was the only way he could ever find parking there. I do not envy you.

[serialk11r]

First log is in, 31mpg. I'm surprised it's that high because I go 70 on the freeway (40 miles in traffic gets really boring...) and this tank has several hours worth of wading through stop and go traffic + searching for parking in it, plus lots of ultra steep SF hill climbing and steep downhill runs with stop signs every block.

I decided it's pretty dumb looking for a free parking spot for half an hour when I can just pay 15 bucks to park for the day so the next tank should be quite a bit better.

So far, not bad for a 2800lb car.

One problem I'm running into with engine off coasting is that this engine is very good at starting itself back up, so I need to key off for a considerable amount of time to kill the engine, and during that time it's not tracking my miles. I imagine I probably travelled like 3 miles with the engine off which wasn't taken into account by the odometer. Too lazy to put in a kill switch, whatever.

[serialk11r]

Today I was doing my engine off coasting thing, and when I almost reached my destination, the check engine light came on and I freaked out.

Then I scanned it: Catalyst efficiency below threshold. I'm pretty amazed that I was able to trigger that light.