90 crx hf how can i increase gas mileage?
 

I just bought a 90 crx hf with 144000 miles on it. still has orig. engine (d15b6) and tranny. the only mods on it is a stage 3 racing clutch dc headers and a flow master exhaust with a 4 inch tip. I would like to make it stock again what do you guys think i should do? thanks

tyler

I can't imagine those mods would affect MPG that much.

Leave the headers and exhaust.. change back to a quiet muffler if you prefer.

Free flowing exhaust will most likely give you a slight mpg boost..

okay thanks. The car also has a cold air intake but it doesnt fit the car. the owner before took it off a lower 90s civic and put it on. you can pull it right off pretty much. is there a cold air intake that would fit for this model? i have looked for some and found a couple but some sites offer them and others dont for the same intake. so i dont know if they really only fit the 1.5l base 90 crx.

Cold air intakes are good for horsepower but generally bad for mileage..

In fact people are doing the exact opposite and making warm or even hot air intakes to increase mileage.

Cold air intakes have been reported to increase mileage, I would assume by reducing intake restriction in badly designed systems. Either way, if you're interested in monkeying around with your intake, might as well give it a free-flowing Warm Air Intake.

okay thanks tons. so change the muffer and get a warm air intake? anything else i could do to the car to increase mileage? I know I want to change out the clutch to a stage 1 cuz you have to get the car to 2k just to get it to move. and it bogs out if i go under that with the stage 3. Im going to try hypermiling i just read up on that.

I also had another ? have any of you guys used that water for fuel thing? does it really work? thanks

tyler

I don't think bogging under 2k rpms is the clutch. Mine used to do that. It is a CA car. I put the Fed ECU in it and that fixed it. I'm not sure if the old ecu was bunk or not though.

With mine it can start out at 1K in first provided I give it very little throttle until it hits 1.5K then it can be floored

The best part to modify is your driving.

Your clutch could be no good for FE, and a WAI would probably help (though I haven't yet tried one). Be sure to add air to your tires if they're not already at the maximum pressure stamped on their sidewalls (see the tire pressure link in my sig). There's probably other things you can do.

All added up, those modifications won't have anywhere near the effect that changing your driving habits will.

I don't believe in any of the miracle FE products like water for fuel stuff. I may eventually consider a DIY HHO experiment, though.

If your car has a lightened flywheel that will cause low rpm bogging.. Heavy flywheels tend to produce a more even and usable low end torque.

If you do have such a beast, it wouldn't be hard to trade your custom parts for the stockers and probably make some money to boot.

If your car revs very quickly when throttled up in neutral you might have a lightened flywheel.

I have seen flywheels lightened to the point where the gears in the tranny were rattling in neutral.

You should be able to engage the clutch at 1000 RPM. The performance clutch should not really affect your mileage as long as you drive economically. If the pedal pressure is objectionalbe you might want to replace it.

regards
gary

I think I have that happening in my sedan. I have a clatter that I can't isolate while idling in neutral. Sounds like its coming from the tranny. I have a 9 lb CrMo flywheel in it.

If the prior owner swapped in a tranny from another model (Which would give better performance) swapping it back will give you better FE. Geared far taller.

Okay thanks everyone for the help. I will check out everything you guys said. Ill post again with an up date thanks again :)

tyler

The high flow exhaust will totally kill your low end torque, your car should have plenty of power at 1,500 to 2,000 rpm, if you study fluid dynamic, air intake and exhaust design you will see that a smaller around exhaust and smaller intake help with low rpm power and efficiency, the HF exhaust is smaller then the exhaust on all of the rest of the CRX's for a reason.
When I went back to the stock exhaust on my crx hf I saw almost a 4mpg increase, when I fixed my air intake on my civic vx I saw a 2mpg increase and in both cases it made the car easier to drive.

lol why would anyone put a stage 3 clutch on an HF engine. :confused: you might have a problem finding stock equipment, i hardly ever see crx's at the junk yard much less an HF.

Yeah I dont know why anyone would put a stage 3 in unless they planned on a swap or something. I do plan on trying to find a stock 1 or find a oem replacement. I also planned on replacing the exhaust 2 thanks again

tyler

intake issue
 

I think what probably happened with your intake hose (since you mentioned being able to pull it right off of the throttle body since it doesn't fit tightly) is that it more than likely came off of an Si model. These have the same air cleaner box, but the hose that runs from the box up to the throttle body is much wider on the Si model...which would cause it to fit very loosely on an HF throttle body.