1989 CRX aero mods - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

2000neon · 02-09-2013, 07:58 AM

What mudflaps? If you mean the ones in front of the rear tires, those are likely improving MPG as the act as tire spats to direct air around the spinning rear tires, instead of allowing the air to go straight into them.

coyoteX · 02-09-2013, 09:10 AM

ultimx, Does your crx have the shift light? If it does it is a 49 states Fed edition. Good start!!! your car does not need a bellypan. Look underneath from the rear. Does your car have A/C? If it does and you want to keep it that limits what can be done with a grille block. Getting your exhaust system all in a straight line is a good simple start. Then you can do a diffuser in the rear where the muffler is now. Oh yeah, I picked up almost 5 mpg with the skinny Sumitomo HTRT4 tires.

ultimx · 02-09-2013, 06:45 PM

Quote:

Originally Posted by coyoteX

ultimx, Does your crx have the shift light? If it does it is a 49 states Fed edition. Good start!!! your car does not need a bellypan. Look underneath from the rear. Does your car have A/C? If it does and you want to keep it that limits what can be done with a grille block. Getting your exhaust system all in a straight line is a good simple start. Then you can do a diffuser in the rear where the muffler is now. Oh yeah, I picked up almost 5 mpg with the skinny Sumitomo HTRT4 tires.

No but I have the transmission. Yeah I saw your album and might do the same thing but full rear enclosure. No ac so I'm good. What size wheels do you have? Idk if I can find this tires. I was looking for the LRR tires but didn't see any in the size I had.

coyoteX · 02-12-2013, 09:31 AM

I had 175/70R13's and went with the recommended, P165/70R13, Sumitomo HTR T4's and averaged almost 5 mpg better. These are LRR tires and they work pretty good in rain and snow. With all of the variables in real world driving, I don't think the full rear fairing is practical. If you are headed to Bonneville, then absolutely, you will need it. I still say, start with installing a vacuum gauge and learn how to use your right foot. I believe a few years ago, a guy entered one of these cars in a mileage event and averaged 108 mpg. That was on a closed course, fuel economy event, probably 45 mph top speeds, not the real world. Mirrors, passenger seat, spare tire and any unnecessary weight were removed. I believe he taped all body gaps and rolled window down to get in and out. Oh, he did make his own version of a nose that was quite a bit larger than mine. It reminded me of a cow pusher on the front of an old train.

ultimx · 02-12-2013, 01:31 PM

Quote:

Originally Posted by coyoteX

I had 175/70R13's and went with the recommended, P165/70R13, Sumitomo HTR T4's and averaged almost 5 mpg better. These are LRR tires and they work pretty good in rain and snow. With all of the variables in real world driving, I don't think the full rear fairing is practical. If you are headed to Bonneville, then absolutely, you will need it. I still say, start with installing a vacuum gauge and learn how to use your right foot. I believe a few years ago, a guy entered one of these cars in a mileage event and averaged 108 mpg. That was on a closed course, fuel economy event, probably 45 mph top speeds, not the real world. Mirrors, passenger seat, spare tire and any unnecessary weight were removed. I believe he taped all body gaps and rolled window down to get in and out. Oh, he did make his own version of a nose that was quite a bit larger than mine. It reminded me of a cow pusher on the front of an old train.

Aren't the stock tires larger than that? I do plan on installing a vac gauge. I'm pretty good at staying in constant pressure but this should help visualize everything. You are right on the milage but it wasn't closed course. Lol I do remember that article cause I plan on doing something similar

slownugly · 02-12-2013, 05:43 PM

im very intrigued. i was planning to do a similar rear diffuser for my 4 door. i like the nose. its not too noticeable on the crx. any pics of the rear diffuser and rear tire spats up close?

coyoteX · 02-13-2013, 07:32 AM

ultimx, This is the stock tire size for the HF. As for the VAC gauge, it's not constant pressure but the highest vacuum under any load condition that matters. You will see that conditions constantly change. On long hills I try to keep at least 2" of vacuum. On reasonably level terrain, I try to average 8" or better. Remember, I'm at 6000-7000 ft. elevation most of the time.
slownungly, What photos I have of the diffuser are in the Tadpole album. Basically, it's a 3 sided tapered box, that attaches at the rear, of the rear suspension, near the control arm pivots and at the bottom of the bumper cover. The front tire spats are more important than the rear ones. The leading edge of the front tires create as much drag as the mirrors do. Turbulence from everything else going on under the car minimize the need for the rear tire spats. Look under all newer cars at the body protrusions in front of the tires to get the idea. The side view of the car with my foot in the picture is the best profile shot. Note the thin flaps ahead of the front tires. Those create turbulence in front of the tire. I removed the ones you see in front of the back tires because they were to large and not really needed anyway. I also removed the small fins on the rear corners of the trunk lid. On new cars, the tire spats have a curb shape and are very short. You want to create a concentrated area of turbulence that will flow at the tire, so that it does not attach to the tire. Turbulence will set you free. Remember the divots on the cover of a golf ball.

slownugly · 02-13-2013, 10:00 AM

Ok so you want a spat in the front to direct the air at the tire and not around it? I took your advise and looked at a 2007 Toyota yaris I inspected this morning. It had front and rear spats but the front is only a small one while the rear is a little longer, I'll include pics.

And in regards to the rear diffuser why did you make it that box shape instead of a full pan? Does it direct the air out better that way?

Here's the yaris spats.

coyoteX · 02-21-2013, 09:49 AM

slownugly, Look at the diffusers under F1 cars to get an idea of how small they can be and still be very effective. The important aspects are; fences on the sides, roof has to face the ground, angle of the roof 3*-5*. If you can find wind tunnel tests, it's amazing how the diffuser under the bottom changes the air flow over the wing on top. Belly pan vs. no pan, are you headed to Bonneville? Get a vacuum gauge and learn to use your right foot first.

slownugly · 02-21-2013, 11:12 AM

Haha no bonneville. I'm about to start doing aero mods on my civic and I'm debating which routes to go. I like the mods you have done because they are subtle and barely noticeable and that's what I'm after. No crazy boatail or anything. I researched diffusers and learned their effect on f1 cars. I'm a mechanic and diagnostician by trade so I'm very in tune with how the car runs. It's a lean burn engine and I monitor it via afr gauge. I should have a vaccum gauge but that will come shortly. However, I'm a total noob at aero modifications so I'm just looking for a game plan