how many rpms do you rev at starting off first gear?

[strat61caster]

Originally Posted by tahdizzle

Driving habits and Octane are mutually exclusive.

If a car is "tuned for a higher octane" then its probably a requirement to use Premium octane.

If we take use that logic, a car tuned for "regular" Octane would get better MPG. Which is not true. Octane has an effect on Performance, but not MPG.

Your driving habits typically do not change based on the output of your engine, for example person needs to reach 65 mph during the 200 feet it takes to merge onto the freeway. If an engine is running less efficiently i.e. one pulling timing due to a lower octane rating to prevent knock the engine will burn more fuel to reach the required speed over the allowed distance than an engine running more efficiently on the appropriate octane fuel that's capable of generating more power with the same amount of fuel.

Say it takes 50hp to maintain freeway speeds, in an engine that utilizes higher compression the combustion cycle is more efficient, a higher percentage of the energy in the fuel is converted to work. If all of a sudden you have to reduce that efficiency to prevent knock (again, pulling timing when using a lower octane) you have to increase the amount of fuel you are burning to compensate and maintain that speed.

Edit: I'm speaking very generally here, if you would like me to start pulling references and formulas I can.

[tahdizzle]

Originally Posted by strat61caster

Your driving habits typically do not change based on the output of your engine, for example person needs to reach 65 mph during the 200 feet it takes to merge onto the freeway. If an engine is running less efficiently i.e. one pulling timing due to a lower octane rating to prevent knock the engine will burn more fuel to reach the required speed over the allowed distance than an engine running more efficiently on the appropriate octane fuel that's capable of generating more power with the same amount of fuel.

Say it takes 50hp to maintain freeway speeds, in an engine that utilizes higher compression the combustion cycle is more efficient, a higher percentage of the energy in the fuel is converted to work. If all of a sudden you have to reduce that efficiency to prevent knock (again, pulling timing when using a lower octane) you have to increase the amount of fuel you are burning to compensate and maintain that speed.

Driving habits are mutually exclusive to octane. Octane has NO affect on MPG. Period. No discussion. This has been proven time and time again. You're engine retarding timing to prevent knock is because the nature of octane. And you may get a MARGINAL decrease in fuel efficiency, but its not the fault of the octane.

[Roadcone]

I'm not sure how you guys are pulling away at 1000rpm. Just to keep up with traffic i'm normally over 1500rpm and if i try and leave under 1100 the car will bog and actually kill the DRL Leds.

[OctaneFRS]

Originally Posted by Roadcone

I'm not sure how you guys are pulling away at 1000rpm. Just to keep up with traffic i'm normally over 1500rpm and if i try and leave under 1100 the car will bog and actually kill the DRL Leds.

You can do it but for me it takes a lot of slipping the clutch. I've had the DRLs dim on me too.

I know I talked about it earlier in this thread. I would think that slipping the clutch for a longer period of time would be worse for the clutch life than a slightly more aggressive launch and earlier clutch release.

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[SlammedSilly]

i dont slip the clutch at all.... i dont care for the guy behind me... they can wait until i get up to speed limit

[OctaneFRS]

Originally Posted by SlammedSilly

i dont slip the clutch at all.... i dont care for the guy behind me... they can wait until i get up to speed limit

You have to slip the clutch. The lower the rpm, the longer. Anytime the clutch isn't fully engaged, you are slipping it. To start without any throttle, you have to slip the clutch for a long period of time to avoid stalling.

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[strat61caster]

Originally Posted by tahdizzle

Driving habits are mutually exclusive to octane. Octane has NO affect on MPG. Period. No discussion. This has been proven time and time again. You're engine retarding timing to prevent knock is because the nature of octane. And you may get a MARGINAL decrease in fuel efficiency, but its not the fault of the octane.

You baffle me... We seem to agree on all the steps and then at the last moment you go right when I go left.

The combustion engine we know and love runs on the Otto cycle, essentially from a pure physics perspective the base amount of work an engine outputs is based entirely on compression ratio, a fluid is compressed and it's expansion generates work or power we know and love.

https://en.wikipedia.org/wiki/Otto_cycle

Now, if you don't feel like reading that we can jump down to the last paragraph in the 'cycle analysis' section where we see equation 6 which looks a bit like:
n= 1 - (1/r^(y-1))
Which translates to efficiency of an otto cycle is a function of compression ratio. Interestingly enough the paragraph right underneath is the next important thing. We both agree that knock is caused by a compression ratio that is too high for the fuel being burned. And we seemingly both agree that timing is pulled to artificially reduce the compression ratio to prevent knock.

Now the trick is we seem to tentatively agree that artificially reducing the compression ratio reduces engine efficiency, i.e. we burn the same amount of fuel and make less power which means that we need to burn more fuel to make the same amount of power. Now yes this is highly idealized but it is the basic principle by which combustion engines have been designed under for 150 years, there are heaps of variables to throw at these equations to be more accurate, but it is the physics behind which we use to understand engine performance, no ifs ands or buts.

Stop me here if we don't agree.

Now translating that to real world driving. Looking back at the post I've quoted, awesome, we agree that driving habits are mutually exclusive to octane, that means that no matter if you're driving a 5.0L V8 or a 1L I3 when you're cruising along at 65 mph on the freeway or merging up to speed from say 25 to 65 you have roughly speaking the same demands from either engine if you're not playing around.

So if you have two engines sitting there, one using the recommended octane running at it's designed state and the other using a lower octane and pulling timing, it would stand to reason that the engine pulling timing is less efficient right? It takes more fuel to produce the same amount of power, correct? So I take both cars, drive them up to 65 mph along the exact same profile of speed vs. time, the one producing less power will require me to open the throttle more, burn more air and fuel to keep up with the engine running at optimum tune, or do we disagree with that logic?

I will not argue the magnitude of the benefits of higher octane in a high compression engine designed for it, but mpg is undoubtedly one of them. You are correct the differences are small and unnoticeable to most but I have a problem when people try to contradict something I firmly believe to be true given my training in physics and engineering. I also have an abundance of time because I'm a loser.

[SVTSHC]

no clue to be honest. I usually do it by feel or sound but I tend to blip the throttle a bit when pulling off, and I very well may give it a little too much as I usually take off from a dead stop faster than most at stop lights.

I also drove an SVT focus with a bad intake manifold running control actuator for near 3 years... seeing as the runners wouldn't switch properly I got used to having borderline no power from a dead stop. It's been a challenging habit to overcome.

My assumption though would be anywhere from 1-2k depending on the situation. 7k on hills .

[SlammedSilly]

Originally Posted by OctaneFRS

You have to slip the clutch. The lower the rpm, the longer. Anytime the clutch isn't fully engaged, you are slipping it. To start without any throttle, you have to slip the clutch for a long period of time to avoid stalling.

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so youre telling me that ive been slipping the clutch for the past 5 years?? but when i drive a high hp awd evo i stall? and i know for a fact i slip the shit out of that!! but you must be right bc you drive with me all the time

[OctaneFRS]

Originally Posted by SlammedSilly

so youre telling me that ive been slipping the clutch for the past 5 years?? but when i drive a high hp awd evo i stall? and i know for a fact i slip the shit out of that!! but you must be right bc you drive with me all the time

If you don't dump the clutch at a launch, you are slipping it. My question was if it's worse to slip the clutch at launch for a longer period of time at lower rpms or engage the clutch quicker at higher rpms.

Not sure why you are getting defensive.

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[SVTSHC]

Originally Posted by SlammedSilly

so youre telling me that ive been slipping the clutch for the past 5 years?? but when i drive a high hp awd evo i stall? and i know for a fact i slip the shit out of that!! but you must be right bc you drive with me all the time

don't be upset

[SlammedSilly]

Originally Posted by SVTSHC

don't be upset

im not upset, haha

[chaoskaze]

At low rpm wear is very minimal thou, just stay in first till 6-8 miles then into 2nd. It drives like an auto that way. Just be gradual & smooth on ur gas.

Just so u know I just let go of my clutch & it's very smooth.

PS: please only do this in first gear

[Big D Design]

What kind of car are you guys driving? Not the same one that I am.

1 We are driving a 4 cylinder car here. This means that there is no torque down low. Have you ever heard of lugging the engine by having the RPMs too low. What this leads to is drive-line lash. All the components like your drive shaft, U-joints that deliver power to the rear wheels will get a certain amount of play in them from stressing them with such low RPMs while driving. Only a V8 can be lugged from such low RPMs.

2 There are essentially 2 ways to launch our car (other than drag racing clutch dumping).
Quick Launch.. 2500RPM smooth letout of clutch
Slow Launch... 1700-2000RPM fast letout of clutch. This would be used in heavy traffic that is stop and go

3 The FRS is not designed to be shifted at 2500 RPM or even 3000RPM unless you are stuck in traffic and you don't have a choice. The car is designed to go thru the gears properly. This means shifts at 3500 and all the way up to 5200RPM just to drive the car normally. See yourself how everything shifts much smoother and goes hand in hand with how this engine was designed. I'm talking about half throttle driving here. Do not lug your engine. Period. The whole point of this car is having a NA engine that gives you such a broad powerband to rev it all day long. Porsche drivers would laugh at the silly RPMs most of you are driving the car. Porsche is a boxer engine also.

4 Have fun with this car. I go out every day in a place where the traffic is not so bad most of the time. The roads are glass smooth with almost no bumps whatsoever. I used to live in a place where the roads sucked so bad and my race cars felt like driving a Jeep. Now for the last 3.5 years I have lived with sports car loving smooth roads that just love to let you rev the car to redline at will. What a difference this makes when driving and feeling the rush of this boxer engine. Everybody please stop driving this car wrong. Lugging the engine will just lead to wear and tear on the drive train. Enjoy the madness the FRS brings. Only we know what fun we have here. Shhhh!