Hey everyone,

was recently speaking with Mr. Christian Carlisi about fuel injectors and fuel consumption, and thought I would share the details of the 1610 mile trip I recently made from fort worth tx to nj in both cars

My FD, 850s and 1300s, Chris Ott (www.rx7.com) tuning, fresh off of a 342 rwhp at 12 psi low boost tune. Cruising at ~90 mph, just over 20 mpg. Cruising at ~70 mph, just over 22 mpg. This is with a newly ported motor, open exhaust, and a complete tune up done with the exception of an o2 sensor that prolly needs to be replaced.

As you can see, running 850cc primaries has no affect on fuel consumption, nor does it adversely affect driveability.

In my stock as hell FC vert, I saw just under 24 mpg cruising at 80mph the whole way. Complete tune up, to include new plugs, wires, o2 sensor. The TPS was giving me some problems with rich running at decel and idle, so there was some room for improvement.

Just wanted to throw that out there for comparison purposes

 

Not bad. My stock fuel injector equipped FD gets similar mileage. Just above 20mpg if I go a steady 90mph... but more like 25mpg if I go a steady 75mph.

 

i have 550's and 1600's. usually get 20-24 on the interstate depending on rpm. if i keep it around 3k, it does really good

 

Rich, what have you been getting around town?

I've never really had the car on the interstate for any length of time.
I only get about 10 MPG, but the car runs very smoothly, so I'm not really complaining.

Oh BTW I have 550s/1600s.

 

My near-stock (downpipe/catback/fresh motor) FD got 23.7 MPG on the way back from purchasing the car. That was cruising right at 80 the whole way. Nuttin' wrong with that!

Still haven't got a good estimate of in-town fuel economy .

Dale

 

Kinda ironic. I have a similar set up, also built and tuned by Rotary Performance. 360RWHP, street port, single turbo, at 13PSI. 850CC primaries. I average a little over 20MPG as well, during normal freeway driving. (WOT is a little less though )

 

umm the only reason you would get bad gas mileage with big injectors is if your dumping way too much gas cruising..... this is directly related to tuning, you could get the same MPG with 1680cc primaries........

 

/\ yea but the guys with big injectors like to use them!! consumption goes through the roof 95+

 

This reminds of something I read that totally blew my mind...I believe I remember reading that a stock FD gets 52 mpg cruising at 50 or 55 in 5th gear.

 

only if it is being towed by a geo

 

On my stock FD, I got over 27 mpg.

I am not kidding. I just recently bought this car. Did a first test, drove 75-80 on the freeway most of the time. Avg 27.4 mpg.

That's with 90% hwy, 10% city. Amazing huh?

I think the car is stock (1 cat, and no muffler).

 

I don't believe that for a minute.

 

Down the side of a mountain, maybe.

 

You know, if you KNEW for a fact that you could go on a long trip without going into boost or getting under heavy load, you could use a device like an safc or even a method to reduce fuel pressure, lean the thing out, and get 30+mpg very easily. It isnt realistic for this to be cost effective or even reliable, but it could be done. Just turn down the fuel little at a time while cruising until it begins to sputter, then richen it back up a hair. So long as cruise conditions didnt change much this would never do any damage to anything. With a car such as the FD, most people cant control their foot this long, so it's a moot point.

 

It's possible. I got 26 mpg w/AC on from Midland Tx to Las Cruces Nm in my stock Fd while going to sevenstock. The guys in the caravan didn't believe me either.

 

I vaguely looking at a post that someone did something similar to what you're saying. I think he used the PFC to tune the engine so that it would fool the engine to do something....I forget what but I vaguely remember something like that.

 

What cruising RPMs are you guys running at, city and highway? It feels like 2200 is starting to lug the poor Wankle, so I keep it above that and just below 3k.

I'm completely stock, and have been getting 11-12mpg around town and close to 20mpg "highway". Though my "highway" miles are 20-15% stop & go.

 

It IS possible to get "good" mileage! When I bought my car (stock then) I drove it from TX to MI, about 1100 miles all highway. The average for the whole trip cruising between 60-80 with intermitent use of the AC was just over 24mpg.

I wanted to test it and ran a full tank with no AC and with the cruise set at 65, got 27 mpg!! That I consider my ideal maximum as I haven't been able to repeat it. Maybe it was a slight downhill or I had a tail wind who knows...

I get about 14 all city though

 

he was refering to the comment made about getting over 50 mpg.
I tend to get around 24 mpg on the highway, and thats with a little WOT every once in a while when i get to a point where i want to pass somebody or when it is straight and open. I usually set the cruise at 75 mph though.

 

My N/A FC gets 27 MPG doing all the "good things" for mileage, running 87 Octane. My FD heavily modded and 4.3 rear gears gets 20 MPG doing those same "good things" for mileage running 93 Octane. The FC is 33% cheaper to drive on trips.

 

Oh, in the city i prolly get more like 8-10 mpg, of course, im running a t78 and love that gas peddle.

 

Now *that* is horrendous. As laggy as that turbo is, I can't imagine you boost all that much in the city. Why do you think it is so bad?

Rich

 

Well here's an update on my mileage. I took the Fd to Dallas this weekend. I filled up drove to the northeast side of Dallas from Midland. I even stoped in Abilene to watch a football game. I put 376 miles on the vehicle in this period and showed to have slightly below a 1/4 tank left. Went to fill up and I could only get 13.3 gallons in the tank. The math shows that I just got 28.27 mpg. This was cruising at 75 w A/C on up until Abilene. Now the funny thing is, I didn't get nearly the same mileage on the way back. I had to put gas in in Big Spring. This time I had my sister with me and some of her stuff in the back. Oh yea the A/C was on all the way back.

Hmm I guess the drive to Dallas is at a lower elevation compared to driving back?

 

I get pretty close to 30 MPG on the highway on nice long trips without out getting on it all that much. It can dip down to single digits easily though.

 

On the way home from purchasing my FD i got about 27mpg with the a/c on. After getting the mods in my signature and an on-the-safe-side pfc tune by phone with rx7trix. , get about 8mpg in the city WOT a lot tho... and about 15mpg on the highway.. Also my ecu is tuned for cat-back and fmic which i dont have on yet so it IS running a little rich. I'm gonna see in spring what i get with those parts in.