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Horse Power vs Fuel Economy


Guest tony78_280z

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Guest tony78_280z

Roller Rockers reduce friction and therefore increase horse power and economy. What other mods other than weight reduction will get the same or similar results? These are the mods I would feel justified in making. Any Ideas? :twisted:

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Electrice water pumps are supposed to increase HP but some people think its BS because the alternator has to work "harder"...

 

Same thing with an electric fan.

 

Also doing anything to reduce drag on the car will help with fuel economy.

 

Guy

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Compression and the right cam are major contributors to mileage & power. Higher compression makes it more efficient and you don't want too much overlap from a cam, keep the duration under 280 degrees in most cases. Definitely the electric fan, don't know if the electric water pump is worth the money for the little you'd get. Good exhaust system, one that's not too big, either!

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Here are a few others:

Skinny tires

Thinner oil in engine, trans, and diff

A lot of ignition timing (35 degrees) during "low load" conditions

Lean mixture

A lot of overdrive to reduce rpms

Headers and free flowing exhaust

Don't use high volume oil pumps

If you have a Holley carb, use a bigger spring in the vac secondary and lower numbered power valve.

Roller cam

Lighter feet

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Roller Rockers reduce friction and therefore increase horse power and economy. What other mods other than weight reduction will get the same or similar results? These are the mods I would feel justified in making. Any Ideas? :twisted:

 

I'll bet you a dollar you won't see a measurable change in fuel mileage from the lower friction of roller rockers. You will probably spend more money to upgrade the rockers then you will ever see in fuel savings.

 

And yes, the idea that electric fans/water pumps save gas is BS provided they are doing the same work as there mechanical counterparts. Think about it. If alternators didn't put load on the engine, why not hook up 10 of those bad boys and power your house for free?

 

Unfortunately most changes you make to conserve gas comes at the expense of HP. David Vizard wrote a book about building for economy and power. Might be worth a look.

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Roller Rockers reduce friction and therefore increase horse power and economy. What other mods other than weight reduction will get the same or similar results? These are the mods I would feel justified in making. Any Ideas? :twisted:

 

I'll bet you a dollar you won't see a measurable change in fuel mileage from the lower friction of roller rockers. You will probably spend more money to upgrade the rockers then you will ever see in fuel savings.

 

And yes' date=' the idea that electric fans/water pumps save gas is BS provided they are doing the same work as there mechanical counterparts. Think about it. If alternators didn't put load on the engine, why not hook up 10 of those bad boys and power your house for free?

 

Unfortunately most changes you make to conserve gas comes at the expense of HP. David Vizard wrote a book about building for economy and power. Might be worth a look.[/quote']

 

I would have to agree about the rollers and the small amount of HP you'd actual feel. (maybe) Probably wouldn't feel it with the butt dyno. The key with rollers is that you can get steeper ramp for more lift w/o having to have a ton of duration, which makes for better power.

 

You can't think that a stock fan and electric fan take the same amount of energy, do you? At least the electric can be turned off most of the time, but turning a big fan at 3-4k rpm takes some effort, more than the alternator would by just doing it's job. I would have to think the same would apply to the electric water pump, but probably not worth the money. I'd recommend a lightweight flywheel to free up HP actually at the wheels. I've always run electric fans & aluminum flywheels. Like you said, you always sacrifice something.

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Electric fans are kind of a reoccuring theme with me so I know I sound like a broken record.

 

You are absolutely right, if you can run with your electric fan off then you are putting less drag on the engine. Hence my "doing the same amount of work" caveat. But keep in mind that is what the clutch assembly on a mechanical fan is suppose to do so the difference is not as great as some people expect.

 

But my point is power is power. It doesn't matter whether it is electrical or mechanical, it all has to come from burning gasoline in the engine. ("Energy can be neither created or destroyed...") The only way an electric pump or fan saves you energy is if it is not pumping the same amount of water or air. So the only reason a mechanical pump/fan would be inefficient is if it is pumping more than you need. The same savings could be realized with smaller mechanical device, but then you are giving up cooling capacity. Hence my personal aversion to electric fans on street cars: you are generally trading cooling capacity.

 

But, as pointed out to me by many different members, a good electric fan with a proper sized radiator AND the alternator capacity to run it is more than adequate for a V8Z, so why worry about it? Comes down to personal prefference at that point.

 

Now for drag racing you can put in an alternator cut out switch and just run everything off the battery. This uses energy stored in the battery thus freeing up some HP for the rear wheels. But that is not really a fuel savings because the engine will just have to work that much harder to charge the battery back up once the alternator is cut back in.

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I hear ya. I have to wonder who would use a mechanical fan on their V8 conversion, anyway. They are ugly! At any rate, most accessories will draw a little power, but not enough to make a huge difference the to daily driver. Shoot, even the new AC compressors only take 7HP when on and it's not like you'll feel much if you have 400RWHP to begin with. Bottom line is that almost all your power comes down to compression, headwork, & a good cam. Other factors are intake & exhaust. So, no magic HP "silver bullet". It's all about "how much do you want to spend". :-D

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