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Long time Honda owner, first time EX Coupe. Question:

My other two Honda's (05 Accord EX Sedan and 98 Civic LX Sedan), both hit around 3000 RPMs when driving 70MPH on highway. I just picked up this 2003Civic EX Coupe last week and noticed it is around 3400 RPMs at 70MPH. **Note that all are manual 5spds.

Is this normal? Is the Coupe geared differently?

She sure drives nicer than my 98 that has 168k miles on her!! And sportier feeling than the 05 Accord.

Thanks,

Ted

 
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Yes, the gearing is a bit shorter on the EX compared to the LX/DX. 80 MPH is about 4000 RPMs in 5th gear on the EX.

 
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Yeah, I noticed that also.

 
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Thanks for the info Ronaldo9. I was hoping it was normal and not something that was going to cause me poor MPG outcome.

Ted

 
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ummmm my ex goes:

60mph at 2.6k
70mph at 3.0k
80mph at 3.4k
90mph at 4.0k

havent had it any higher

 
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Envy - Is yours 100% stock? That seems odd.

I checked speed via GPS today and seems dead on. Speedo reads 70, gps 70 w/ RPMs at 3400.

First full tank gone. Filled up and checked mileage. Only 33.7MPG. Almost all highway, 100% stock and between 65-70MPH crusing speed. Other than slow down, what can I do to get her up to around 38-40MPG?

Thanks,
Ted

 
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Stay out of VTEC or under 4k youll be getting 400 miles per tank. Clean your air/filter make sure ur tires up inflated to spec (30psi) and run some fuel system cleaner ever other oil change.

 
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nahh i have a short ram intake. possibly the cause of the drop in rpm's.

^^n what he said for 38mpg

 
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I have read on here conflicting points on air intakes. One would think that if you can do 70mph at 3000rpms, that is more efficient and thus better fuel economy. But I was also reading your ECU would adjust to the extra air intake and inject more fuel, thus lowering MPG??

What's the real school of thought on this? If one adds air intake and travels highway at fixed speed, won't it increase MPGs?

 
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Im thinking yes because:

at 3000rpm, even if more gas is being injected is still less than less gas injected at 3400rpm. not only is the engine working less, but its saving 400revolutions per minute

 
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So I have seen these short ram intakes anywhere from $20 (fleebay) to $200+ on auto sites. So, what is the most cost effective solution?

 
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Update:

Spent a full tank doing the following:

Traveling my highway commute @ 3000RPMs. Out of 80 mile round trip, 74 is highway.

Town travel, shifting at or below 3000RPMs and watching my pressure on the gas (letting gears do the work increasing speed).

Air filter is clean.

MPG for entire tank doing the above was only 34mpg.

So - yesterday, I did the following:

Added fuel system/injector cleaner to tank. Checked tire pressure - was really high on the new tires/wheels instaled by the shop (Bridgestone Potenza G 0009 stock 15" size). They were at 40psi, door said 30psi, so I adjusted all to 30psi. Installed new NGK Iridium IX plugs, gapped to .044.

Over next two weeks, I will see what this does to help get closer to the 38mpg mark.

What else am I missing??

Thanks,
Ted

 
Rep Power: 812

there is alot that will affect mileage. make sure alignment is good too, cause that can cause the tires to drag. 30psi is a bit on the low side, usually running a bit higher than stock is better for handling and mileage. i run no more than 35psi altho the ride is much rougher. buy lubecontrol.com gas and oil additives. raised my mpg from 38 to 42 on the highway just after using them for a month. on colder days mpg will drop. i only get around 34mpg highway in the winter.

 
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hypthothesizing here:
cold days causes gas to condense, therefore a denser gas gets injected into the cylinder to combustion versus warm days, where the gasses pressure is decrreased, and the particles become more spread out?