87 CRX DX mileage questions/projections - Fuelly Forums

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Old 03-02-2012, 11:50 AM   #1
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87 CRX DX mileage questions/projections

Hey all,
I have purchased (in a moment of weakness) a rust free 87 DX with a set of bent valves. I was looking for an HF, but the outta sight pricing is kinda a deterrent. So I'm trying to find someone that uses/mods a 1st Gen CRX for FE. I'm curious as to what I could get out of it with a HF carb and intake, HF ECU, insight or VX wheels W/Moon discs, Passenger mirror delete, and (swapping in lighter HF as motivation allow, lighter drums, etc) and mild hypermiling (EOC down hills, shutting down at stop lights, 65MPH freeway, NO P&G)

That's my plan to start, any idea what that might get me? (the goal is 55MPG) I probably drive a little more highway than city, but not much.

If I need more, I may try a cam swap, can I replicate the cam grind of the 8 valve HF (same lift and timing and whatever witchcraft goes on in a cam ) and drop that in the 12V head? and if I ever do find an HF tranny, do a full swap? or just 5th gear? (if I had an HF head/cam, would match up to the HF tranny in terms of power band? Some have not been happy with a HF trans and a DX/SI motor)

Anyway, If anyone has some input I'd greatly appreciate it, most of the internet info regarding CRX's is for the "Go Fast" crowd. Nothing wrong with that, but it's hard to info on economy mods.
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Old 03-03-2012, 06:07 AM   #2
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Re: 87 CRX DX mileage questions/projections

I have an 87 CRX HF. Since the original 1.5 liter HF engine needed rings and a $250 oxygen sensor, I swapped in a 1.3 liter engine from an 87 civic (8 valves, higher compression ratio- but the non-HF cam) and was getting 48mpg on long interstate trips at 65-70mph.

I think that 50mpg at 65mph will be very doable for you if you swap in an HF transmission and do a few other small modifications to lean out the mixture. But if you do much stop and go city driving, it will bring your mpg way down.

I was able to get 44-45 mpg at 70 mph out of my 87 civic after an HF trans swap. Check out my gas logs for the blue mosquito and stingray just to the left of this message to see more details of all of the mods that I tried.

Try www.car-part.com and maybe you can find an HF head to bolt onto your DX block (rather than replacing all of the bent valves). It will have the low rpm cam and roller tipped rocker arms and will bolt up fine.
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Old 03-03-2012, 08:58 AM   #3
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Re: 87 CRX DX mileage questions/projections

I've been keeping my ear to the ground on Car-Part, and I'm willing to swap in HF engine/trans, but I really want to do them both at the same time. I like the idea of a 1.3L swap, how hard is it to find parts? and do you loss lots of power compared to the 1.5L HF engine?

Also, I'd kind of like to get my CRX weight down to the HF weight. Is that possible by finding everywhere they saved weight building the HF and getting the lighter parts? (and a ton of patience )

I see on the your to-do mod list for the stingray, a DFCO switch, How do you put one on a carbed engine?

do you have a hand throttle on the stingray?
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Old 03-03-2012, 03:10 PM   #4
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Re: 87 CRX DX mileage questions/projections

It wasn't too hard to find rings and bearings when I rebuilt the 1.3- if I had it to do over again I would have just reused the bearings. The old ones were fine and the new ones were about $100. The 1.3 has noticeably less power than the 1.5, especially at low rpms.

Yes- you could find most of the weight saving parts (half sized radiator, aluminum rear brake drums, lighter rear axle, aluminum air cleaner, plastic valve cover) but it would be very expensive just to save 200lbs or so.

The 84-87 civic/crx carbs have an anti dieseling solenoid that cuts off gas to the low speed passages in the carb when the key is turned off (it is on the rear of the carb next to the firewall)- so I wired it up so that I could cut power to this solenoid when I was decelerating. I was just beginning to test it last fall when I parked the car (the gas money that it saves doesn't make up for the extra insurance costs).

The lever on the left side of the steering wheel is a hand operated clutch- pulling the lever toward the steering wheel pushes down the clutch pedal.

www.redpepperracing.com is a great resource for these cars.
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Old 03-03-2012, 06:05 PM   #5
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Re: 87 CRX DX mileage questions/projections

Weight reduction would be a bit challenging with the lack of early 84-85 parts. The front "bumper" on the 84-85 is a strip of steel that can't take any impact at all, but it weighs about 20 lbs less than the 86/87 front. The recessed headlamps are about 6 lbs less, but are not as aerodynamic. The rear axle could be swapped for the dx1300/hf axle but does not have an integral sway bar. The hf or dx1300 cars had solid small front discs that were much poorer for stopping.

Basically what I'm getting at is that there is not much weight to be saved without performance (handling/crash) degradation.

My favorite weight reduction in my 84 that I did was to ditch the factory battery location and use instead a comparable AGM mounted in the passenger footwell. It saved 22lbs off the nose of the car and cleaned up the bay.

From here:


To here:


Bay without a battery:
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Old 03-03-2012, 06:11 PM   #6
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Re: 87 CRX DX mileage questions/projections

Here's the best weight to add:

http://www.redpepperracing.com/forum...howtopic=48385

An additional few pounds in the rear isn't a big deal and the handling prowess it adds is amazing! My full setup cost me less than $30
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Old 03-04-2012, 07:58 AM   #7
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Re: 87 CRX DX mileage questions/projections

one thing I am considering is finding lighter wheels. I believe the 13" wheels weighed 17 pounds. some vw rims weigh 13 pounds. lighter rims would have the most impact on power and mpg.
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Old 03-04-2012, 08:39 AM   #8
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Re: 87 CRX DX mileage questions/projections

Quote:
Originally Posted by mikehallbackhoe View Post
one thing I am considering is finding lighter wheels. I believe the 13" wheels weighed 17 pounds. some vw rims weigh 13 pounds. lighter rims would have the most impact on power and mpg.
HF/VX/Insight rims are all supposed to be really light. What size rim/tire would make a DX have close to the same gearing as an HF? (I know gearing isn't the perfect word, but bigger tires will simulate a taller gearing)

I'm super excited about getting mine back on the road. A Honda with pillar mounted seat belts, that is older than GA's stupid emissions testing rules. This is going to be fun.
Thanks
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Old 03-04-2012, 11:05 AM   #9
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Re: 87 CRX DX mileage questions/projections

Bigger than would fit. The final drive on a hf is very tall.
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Old 03-04-2012, 03:41 PM   #10
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Re: 87 CRX DX mileage questions/projections

Quote:
Originally Posted by hondaguy72 View Post
Bigger than would fit. The final drive on a hf is very tall.
don't take this personal, but that wasn't what I wanted to hear, so I did the research I was hoping some else had already done for me. This is what I found.... per this site..http://www.ehow.com/how_8195187_calculate-mph-rpm.html
I took the transmission numbers from the 1st gen HF and DX. (HF final drive 2.954 and 5th gear .694) (DX final drive 3.888 and 5th gear.771) That gives us 2.05 for the HF and 2.99 for the DX, (http://www.crxsi.com/specs.htm)

I multiplied that by 60MPH per EHow, and the magic number 336 divided by the 22.6 (diameter of 175/70-R13s) and came up with 1828.67 for the HF and 2674.00 for the DX for RPMs. Using T and E, because I suck algebraic stuff, I sound like I would need a 32 inch diameter tire.

Are those numbers correct?

So anyway, I'm just putting that here because I need a place to park that while I go look for an HF transmission, or an HF CRX . Does that data also show that its not really worth my time to swap in an HF 5th gear? (Tuners do it) but because that doesn't change the final drive, the gain is next to nil?
Thanks for all the help.
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