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Discussion Starter #1
I've tried to do searches on this but I can not find anything that specifically relates to my questions. Here's the main question: for regular daily driving, what is the optimum shift point to improve gas mileage? This last tank of gas, I tried to keep my rpm's below 2200rpms and on highway below 3000rpms. I experienced 23mpg. Before, I usually kept the rpms below 3500 and I was able to get 24-25mpg. -- this is about 20% city / 80% highway - light throttle.

What is the lowest rpm that is safe for the motor to be driven? 1000rpm? 1200rpm? 2000rpm? Does the SR20 actually run more efficiently above 2500rpms?

Currently, I have the following mods: HS CAI, Stillen 4-1 header, high flow cat, 2.5" mandrel exhaust, JWT S3 Cams, Mobil 1 Synthetic motor oil, 300zx radiator cap, NGK wires, 17degrees timing, and nprobe tuned ecu (10% leaner than stock). I dynod at 150whp and 138wtq.

Can the settings on the AGX struts affect the gas mileage? Right now I have front/rear @ 1. (They are matched up with Hyperco Gen2 springs, 15" Rota Slipsreams, and Yokohama ES100 205/50/15 tires.)

Anyone know the actual fuel consumption @ certain RPMS (stock?)?

Also, what kind of damage can be done to the motor if driven at too low of rpms?
 

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sleeper
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I know my motor doesn't like being anywhere below 2k, even cruising. If I were trying to save gas, accelerate very slowly and coast to stoplights. Lugging the motor can add stress and is not too good of a thing to do. I'd probably shift between 2.5-3k rpms.

I doubt suspension settings will affect mileage but tire pressure will.
 

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Discussion Starter #3
spdracerUT said:
I know my motor doesn't like being anywhere below 2k, even cruising. If I were trying to save gas, accelerate very slowly and coast to stoplights. Lugging the motor can add stress and is not too good of a thing to do. I'd probably shift between 2.5-3k rpms.

I doubt suspension settings will affect mileage but tire pressure will.
What tire pressure would you recommend?
 

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lower rpms doesnt mean higher gas milage....i cant really explain how it works, but keep the rpms up. when i had my se-r, cruising around i kept rpms around 3k, on the highway, 3k-3.5k. i usually got around 32mpg combined.
 

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dho said:
What tire pressure would you recommend?

I usually run about 30psi all around street.....do you have a fatory manual fo royu car...i actually looked at mine, and it had the optimal shift points for gas mileage. I usually shift are 3000-3500 and get about 26 or so MPG city.
 

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Discussion Starter #6
djmayhem said:
I usually run about 30psi all around street.....do you have a fatory manual fo royu car...i actually looked at mine, and it had the optimal shift points for gas mileage. I usually shift are 3000-3500 and get about 26 or so MPG city.
Thanks, I'll check out the fsm. It's buried somewhere in my room. I think I'll try what you said. My car has a little resonance around 2800 rpm so I'll keep it around there. The exhaust kind of drones around that rpm so that's the only reason why I haven't been keeping it around there. What gear would ya'll be in around 20mph, 35mph, 40mph, and 45mph? Those are the speeds I have to obey around the city. (school zones, speed traps, and college roads)

The tire pressures... 30psi? I have yokohama es100's and they have a max pressure of 44psi. Usually I have the fronts at 38 and rears at 37. Is that bad?
 

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Discussion Starter #7
When you're starting to accelerate (regularly), what rpm do you let out the clutch? I've been used to 1700-2200rpm. I've also been through 2 axles since I bought the car in August and I have a clunking noise that sounds like another axle breaking.
 

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Here are my shift points 1-2 @ 14-18mph, 2-3 @ 25-32mph, 3-4 @ 38-45mph and 4-5 @ 45-50mph. I have a techtom mdm-100 so I can monitor o2 condition, injector pulse, A/F feedback ratio %. From the data I've noticed when slowing down its best to leave the car in gear rather than with the engine not under load. For example slowing down to a stop light in neutral (5spd) would have the injector at 2.0-2.4msec at idle, where as if its left in gear its 0.5msec. Then the o2 shows 0.00v while decelerating with throttle closed so very little extra fuel is used, the A/F ratio goes to 90% in the same condition.

So far I average around 26-29mpg depending on how many WOT gear runs I do ;). Another thing is closed loop operation doesn't usually got to open loop unless the TPS is more than 1.5v. Generally up to that point the ecu will keep toggling the o2 from rich-lean.

IMHO to get better fuel economy leave the car in gear when coasting to a stop (I leave it in 5th till the engine slows to around 1300rpm). Below 1300rpm the injectors go back to 2.2-2.5msec so that is when I put the car in nuetral. Another tip is to driver slower lol! Driving at 55-65mph will net better economy than 70-80mph even though it seems to take longer.


dho said:
I've tried to do searches on this but I can not find anything that specifically relates to my questions. Here's the main question: for regular daily driving, what is the optimum shift point to improve gas mileage? This last tank of gas, I tried to keep my rpm's below 2200rpms and on highway below 3000rpms. I experienced 23mpg. Before, I usually kept the rpms below 3500 and I was able to get 24-25mpg. -- this is about 20% city / 80% highway - light throttle.

What is the lowest rpm that is safe for the motor to be driven? 1000rpm? 1200rpm? 2000rpm? Does the SR20 actually run more efficiently above 2500rpms?

Anyone know the actual fuel consumption @ certain RPMS (stock?)?

Also, what kind of damage can be done to the motor if driven at too low of rpms?
 

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Veritas
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Engine RPM has nothing to do with fuel mileage. It's all about engine load. How far down you press the gas pedal to maintain speed, in simpler terms.

Here's an example: I cruise on the interstate at 3,600rpm at 75mph in fifth gear. I also blow through the timing lights in the 1/8th mile at 3,600rpm in fourth gear. Which one uses more fuel?

When I have the gas mashed to the floor at the track, obviously.

Same RPM, but two different engine loads.

Moral of the story: It's not what RPM you drive at, it's how heavy your foot is. IMHO.
 

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Discussion Starter #11
I actually timed how long it took me to accelerate from 30mph-60mph on the 'saving gas' method for the last tank of gas... took 18 seconds. How much of a load do you think I was putting on it?

Also, how much fuel is used at idle? I have a remote start system on this car. I didn't use the remote start feature with that tank of gas that I got the 23mpg. For instance, how many lb/hr, g/hr of fuel consumption at idle?
 

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SERprise In WV said:
Engine RPM has nothing to do with fuel mileage. It's all about engine load. How far down you press the gas pedal to maintain speed, in simpler terms.

Here's an example: I cruise on the interstate at 3,600rpm at 75mph in fifth gear. I also blow through the timing lights in the 1/8th mile at 3,600rpm in fourth gear. Which one uses more fuel?

When I have the gas mashed to the floor at the track, obviously.

Same RPM, but two different engine loads.

Moral of the story: It's not what RPM you drive at, it's how heavy your foot is. IMHO.
Very well put G.P.
 
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