https://www.rx7club.com/showthread.p...ghlight=timing

 

One question ... I'm not sure about the s1 and s2 ... but I know that on the s3's we can draw fresh air from outside throught the side air vents. That is the main reason that I said I could take mine out besides saving weight. I bet that is the best bet, atleast for highway ... because it does not create more drag (maybe just a tad bit less actually because you're not blocking the air from not entering at those passage), and does not need to use any extra engine power.

I was waiting for someone to bring that one up but I guess I had too. That is why I love my s3 so much .. just because of those vents. I think every car should actually have them.

 

Update on mileage.
Recent changes to vehicle.
Removed stock fan and installed Fiero electric fan.
Removed A/c belt, had to because lower Accessory pulled would not clear fan.
Removed Air ducting that went to only available incoming air for air box at battery side. Now draws air from front of vehicle.

Same 2 people and same 1st run. Early am with windows up. Average speeds between 65-70MPH all Freeway.
27.1 MPG
2nd run with average speeds of 65-70MPH, Approx 10 miles of in town driving at 35-45MPH.
Windows up for 1st 20 miles then temp rose and windows went down.
Mileage went down to 24.9 MPG
Electric fan was only used 1 time in stop light traffic for about 1 minute 45 seconds. Fan was never used after that point in any of the in town driving.
The rest of the driving was all out 65-70 MPH with the windows down.

 

good numbers

 

I'm pleased with the 27.1. I'm also shooting for 30MPG. :-

It will be interesting when I return to Oregon. Another car that I had got 32 MPG consisitently on the Highway in Ca. When I took a trip once to Oregon in it, I achieved 37 MPG.
This was not an RX-7 though.

 

All depends on the car.

With a weird shaped torque curve, you might end up making the power more efficiently at the higher speed. Efficiency is not linear. I noticed best fuel economy at about 80mph. Why? The engine was using the fuel to move the car more than just keeping itself warm, but air drag was still down.

Also, the throttle position needed for this speed was right in the middle of the flat spot before the secondaries opened, and the flat spot on my car was caused by running really lean. This was intentional. Running lean + low manifold vacuum = good fuel economy.

On the other hand, for a stock fuel injected car where they run it full pig rich over a certain engine speed in order to keep the converter from overheating, you'd notice a marked economy drop once your cruise RPM crossed that threshold.

 

I'm cruisin an 85 GSLSE with an 88 engine, 89 t2 tranny, 17lb flywheel, Stock lsd, 15" rollers, a fresh set of ngks with 10mm plug wires, no emmissions, racing beat dual pipe exhaust system, after market fpr, gen2 fuse box, k&n air filter...25 mpg spirited highway, and 20ish spirited city.

 

Pretty good numbers, especially city. It would be interesting to see what you could do on the highway driving a constant 65-70 MPH.

What do you have your FPR set at and are you still using the stock SE fuel pump?
Also are you running the S4 ECU?

 

well i just filled up on my way home from work, 3rd shift. the verdict: 23 mpg. thats all city, tires that wont stay inflated(i have to inflate one before i leave now to run errands), and not so easy driving. for the last 3 days ive raced the same employee to work when we hit the doubled country roads outside of town. thats full throttle up to about 80 or so. i dont drive too dangerously. plus this is the DD.

what did i do?

i added acetone to my gas. i know i know. my car is going to blow up. i dont care. ill run it until it does. if it does, ill stop. ive seen where many people have done this for YEARS without ANY problems. so if you dont agree with it, dont do it. i dont want to hear anyone bitch. ill keep doing it and get better gas mileage.

the amount you add is 3 ounces for ever 10 gallons of gas. if you add too much it actually makes your gas milage worse. when i added mine i wasnt sure of the ratio and i added a lot. so im certain i can get better numbers when i get the ratio correct and have tires thatll hold air better. with this i know i can get atleast 30 mpg on the highway. thursday i have to take the girlfriends civic on a highway trip for my preop for surgery. ill be putting acetone in it. i think ill break 40 mpg. our best in it so far is 37 on the way to DGRR.

i suggest if youre interested, try it. a gallon of acetone is $15. with using 3 ounces per 10 gallons, it should last a while.

 

install an after market pump and FPR- set it at 2 psi
run the stock nikki
use the nipple all the way to the left for the vacuum advance
give him a header and better breathing exhaust
im using a RB filter set up, thats optional. you could just modify the stock one
im using a 2nd gen coil for leaking and MSD blaster for trailing
ive recently started running with 3 ounces of acetone to every 10 gallons of fuel an noiticed a great improvement. some will be against this but im all for it.

with that being said, i know i can get better numbers. my car is in need of tires that hold air better. i have some exhaust leaks. my car idles at 1100rpm. my timing light got broke. so after i get all this taken car of im sure ill see a gain. im VERY certain i can easily get atleast 30 mpg on the highway. my current best for all city is 23. for all highway was 27, but that was before i started using acetone and i changed how my vacuum advance was hooked up.

 

^^^ thats what Im talking about. Simple things that can make a difference. Keep it coming. Hopefully, it will help the youngsters.

oh yeah, I will give that an 8 for the acetone idea. I havent tried that yet.

 

wacky-- if youre interested in teh acetone trick, check out this site about it:

http://www.pureenergysystems.com/new...00069_Acetone/

many people are saying itll destroy your car. my boss is an industrial chemist and he told me i was an idiot when i told him he should try it. tomorrow ill rub in his face how i gained 5 mpg. i dont want to use anyones name, but theres a person here on the forum that owns a well reputated rotary shop that has been using this in his and his wifes daily drivers for over a year with nothing but good results.
he did say it may not hlep much in the summer. i say you should give it a try.

 

What about trying peejays trick with the timing and using the sidefire plug trick?

I am going to be experimenting with the timing and fuel pressure on the Se but that won't help you much since your carb'd.

If running the stock carb not only will the lowering of the FP help but you have the advantage of rejetting also.

With AWS140's best of 27 so far in a 12a and my best in a 13b of 27.1. I am far ahead of the pack.
With the size of the injectors and the antiquated ECU of the Se that only uses the O'2 sensor at cruising speeds pulling over 27 is not bad.

I think with that FC trans I am hurting the mileage staying at the lower speed range. Probably a cruising speed of 75 would keep it in a better power band and use less fuel.
I also have mixed feelings about whether the ported intake I am using is help or hindering the mileage also.
I do know that the difference between mileage of having the electric fan install
is around a 1 MPG on freeway usage. This is from the numbers that were taken for the same distance to the same place with the stock fan and then with the electric fan.

As far as the usage of Acetone. I am going to do some reading up on this. Our mileage drops considerably during winter here in Ca because of the additives in the fuel. Ca fuel is known to also have some of the worse types of fuel also. Anytime I have gone out of State and checked my mileage, it has gone up.

 

I tried many plugs but as they say, u get what you pay for. Besides, i have a much better solution to them...plugs are pocket items at the junkyard. its free and most of the time, they just need cleaning in which I do once a month. In addition, I dont like running my engine lean. But again, thats just my preference since Im always looking for the unexpected street light to light runs.

 

A guy did the acetone trick over on the GN boards using a mid-90s Civic and noticed no difference. I he also tried different amounts.

 

well, i put the acetone to another test today in the girlfriends stock 98 civic 2 door ex auto. i drove it to atlanta for my preop for surgery. i filled up before i left, added acetone, and filled up when i got back. the trip was 174.9 miles, i rounded to 175. when i started filling it up, the pump initially stopped at 3.12. i added more until i got it to 3.76, which i rounded to 3.8. you do the math, i got about 46 mpg. thats DEFINATELY not possible stock. the best ive been able to get before was 37 on the way to dgrr. this was with AC on at times, windows down at times, sunroof open a lot, and speeds ranging from 60-85.

 

Thats really the only reason i REALLY don't want one of these cars..
But if you can get 28mpg with little modifications then thats not a problem for me..

But there is a way to tune more airflow and reduce the amount of gas needed?
More breathing room, less thirst?

other wise.. uhh No..
I would think hell 1.3 liters is SMALL SMALL SMALL
and yet it drinks so much?! ah... there must be some easy solution
the d16 or whatever in honda gets like 36+ or whatever it is.
and thats even bigger.

 

more airflow would mean more fuel required, not less, or your mix would be lean.

 

You have to remember that the injection system in the SE is not very sophisticated. It is not like todays OBD2 systems. It also only utilizes 2 very large injectors and has a very high volume/pressure fuel pump.

I am going to be doing further experimentation as I stated with timing and with cutting back the fuel pressure.
I will probably wind up experimenting with the Mega squirt system also.

When I get back to Oregon I am going to do a test for fuel mileage again and compare to my Ca mileage.
Afterwards I am going to try the acetone trick.
The 1st test on the acetone will be in my Dodge truck as I am towing the 7 back home.

 

if you want good gas mileage, get a toyota or a honda, dont get a rotary. period.

i wanted a rx7 for a daily driver. afterwards i wanted to improve the gas milage. i didnt want a rx7 for gas milage, thats rediculous.

ive done very simple thing to get what i feel is good numbers. i got 27 mpg highway one time, but i am sure i can break 30. this is highway. city my best is 23. i also live in a rural city so it isnt constant stop and go.

i have my fuel pressure turned down to 2 psi, which is what my stock pump was putting out anyways. i think due to the way i have my car set up it kind of lacks fuel in the high rpms, but i dont care. this is my DD. i have my SA for speed/fun. with this car it seems i have a problem hitting high speeds and it doesnt really feel as though its pulling like it should in high rpms. that could also just bet he lack of torque. im used to riding in highly modded LS1s and a HIGHLY modded MS protege. both of which are torquey.

the way you drive the car will also be a factor. when i got 23 i was dring rather civilized, but also a little spirited. towards the end of the gas tank i was racing an employee every night on the way to work. that was full throttle for a good bit. i feel i can get better than 23. i am happy if i can maintain 20 though.

to get these numbers you will definately want to add a header with better breathing exhaust. my exhaust is a straight through design, but is very streetable. i also have a RB filter set up installed that adds more air to the mix, but i didnt add more fuel to the mix. i know im running lean, but im not worried. if it blows, i have a spare engine and thats why i bought a scooter, back up.

could my car have more performance? i believe so, but i dont care to try. like i said, this is my DD and economy is more important to me.

im curious if my fuel pump set up would be any different from a stock pump. i have the same FPR set up on the stock pump and it held 2 psi steadily. i dont know if any other factors would come into play or not.

 

Did you used the exact same pump? Some pump's filters are dirtier and will stop you sooner - you didn't say that you filled it by repeatedly restarting the pump when initially filled up - its hard to say "I got X mileage" definately w/o doing it more than once - I filled up my old 5.0 mustang (rated 15 - 22) drove it(but not the whole tank, like in your experiment) and refueled and I got 35 mpg! I redid it doing the same driving and filled up at a 1/4 tank and I got like 20 or 23 mpg.

 

this was just the initial test. i will be doing more test in the future. i am constantly running the acetone in my DD rx7. i only use one gas station. i will be conducting more tests with the rx7 than the civic. my girlfriend will only run acetone on long trips, not around town. i dont see any long trips it our near future, so it may be ahile before i get to test it again. id like to test the civic on a long trip where i use the majority of the tank. id also like to test the rx7 on a highway trip.

 

Since getting my latest 85 GSL-SE, I had been consistently getting about 13-14 mpg around town and 24 mpg on long freeway trips (180 miles/tank in town and 320 miles/tank on trips up to Seattle and back). Over the last couple month, however, I have been improving the in-town milage to the point where I now get (as of yesterday) 250 miles per tank...19.2 mpg!

What I have done is (1) increase tire pressure to 38 psi from 32, (2) delete the A/C, (3) installed RX-8 fine-wire plugs, (4) ran a bottle of straight Techtron on a 1/4 tank and (5) started flogging the car a bit more often to help blow out the carbon (I beat a Merkur XR4Ti 2.3L Turbo the other day that didn't want to let me merge into his lane ahead of him when my lane ended ). The result is about a 39% improvement or 70 miles per tank. I'm pretty happy with that. Economy on long freeway trips has not improved much, if at all, but that wasn't expected.

The Acetone "trick" is an old one. One of the kids in the shop tried it and swore on it for a couple tankfulls...then it stopped working. I think it just caused a sensor to mis-read and it leaned out the fuel for a while but then everything went back to normal. Or perhaps it just cleaned out the injectors. Long-term it does nothing substantial, just as sceptics would expect. Fuel economy is big business. Auto manufacturers would kill to get better economy from their fleet and have the resources to investigate every lead.

 

You new intown mileage is very good.
What mods are done to the engine?

 

Nothing. Stock block. Stock Intake. I do have a full Racing Beat long-primary "streetport" exhaust system, but that was on there both before and after. The new engine for this ride is a streetported 4-port 13B that will use a 50mm IDA-style throttle body, but it won't be installed for a while.

Just for reference, I did once manage to get 19.5 mph (highway) with a peripheral port 13B with Weber 51 IDA carb and 4.88 rear end gears...windows down. This was from Gainesville, FL to Dallas, TX, during the one and only stretch without pulling my tire/tool trailer behind the race car. Fuel economy with the trailer was 14.5 mpg, based on the trip from Portland, OR to Gainesville, FL and Dallas, TX to Portland, OR.