The extreme AreoCRX-HF project

[ebacherville]

Originally Posted by fritz

for gear ratios this might help. also looks like swapping 5th gears is easy

http://hondaswap.com/civic-crx-ew/hf...-tranny-70579/

yeah according this this post you can do it in the car.. HMMM may have to investigate that and see if i can find the new gears..

"for the 84-87 trany's...to get the 5th gear.....you don't have to swap the trannies. You don't even need to remove the tranny. Just pop the tip cap nearest to the passengers wheel, and the 5th gear is located right there...pop the gear out of the SI tranny, put the HF gear in, button it up, call it done....some oil might be spilt out, but not enough to even worry about adding more oil."

[ebacherville]

well did a vin search and it comes back as a 49 state model no metion of CA or high alt .. odd..

However cant find any speek of this final gear in parts lists or any how tos .. but sounds simple enough , may have to go under the car to see what up under there and see if i can getto this magic panel on the transmission

Then the next step to find new gears..

The tire option is still there but it will raise the car up a inch or so.. that could actually be beneficial with these long nose and tail sections..lol

[ebacherville]

I made a sample drawing of the top down view of the CRX with the tail and nose.. to get aide of what ill be building next..

[ebacherville]

on paper with both views it doesn't look quite so drastic.. well it may end up a bit longer then.. if I'm going to go through the effort might as well make it worth it..

[mattW]

Originally Posted by tasdrouille

Matt, you are contradicting Hucho.

Oh thats interesting... I was assuming the stuff from Katz about the top boat tail angle would be the same upside down:


also note "When inverting the body so that now the lower surface of the body is slanted (Fig. 6.4D), a similar trend can be expected."
Quote is from here.
I haven't read Hucho, haven't justified spending that much money yet.

[tasdrouille]

Matt, that is interesting too. But the underbody flow being affected by the ground proximity, it was to be expected that it would be pretty much impossible to get the same optimal angle for the bottom as the top.

Hucho's book is very interesting, I went through it in 2-3 days, I love this stuff. I got lucky and borrowed it at my local university library. It was the '88 edition but still valuable.

[fritz]

However i think i found something interesting, my car at 55mph is about 2200 rpm and i have read reports of 88 CRX HF's at 1850 rpm at 55.. so i think my tranny ist a true HF tranny, the owner said it was original.. however i have herd of diffrent tranny's being in CRX HF's in diffrent places of origin.

If the numbers on that hondaswap page are correct it looks to me like you have the correct tranny. My 88 HF CA model pulls about 2000 rpm at 55mph. With the high gear at .65 and the final reduction at 3.58:1 for a first gen hf, and the high gear at .694 and the reduction at 3.25:1 for the CA second gen hf the 1st gen would have about 4% difference in gearing. So if mine is going 2000rpm at 55 then yours would be 2080. I think this is close enough to be accounted for by inaccuracies in the tachs

[ebacherville]

yeah but I DONT want the CA or High Alt tranny, I want the true 5th gear of the HF the one that nets 51mpg stock.. if that page I spotted is correct its a easy swap of the fifth gear.. if not ill go to 155/80-15 tires for a 10% gain.

The difference in mileage is 5-6 mpg with the shorter 5th gear.. I want the really tall one. no sense in making all these mods to the areo then revving the engine at 2250 to go 55-60 mph when the drag is cut down so much.. just waisting gas at that point.

Doesn't matter to much at this point I got lots of areo work to do .. and even if its not a simple gear swap without dropping the tranny, I can always just swap tires and wheels to get a better final drive ratio.. the goal is to lower the revs as much as possible for any given speed once areo mods are done. The motor in the 1st gen of the crx isnt a rpm hogg.. they really weeken out in the upper RPM range they were tuned for that really tall fifth , low rpm and torque there bit not up on the top of the rpm range... totally opisite of the honda engines you see iin the newer hondas..

but if any one spots a first gen HF tranny with the .0655 fifth gear set, I'd be willing to make it worth your time to get the set and ship it to me

[fritz]

Don't get me wrong I'm rooting for you to succeed here but

According to those numbers the gearing in the 1st gen hf is with the correct tranny is 14% lower than the 88 federal 2nd gen hf. So as a stock one it should run at 1850*1.14 or 2109 rpms at 55 mph. The dx tranny would be more like 2600 rpm at 55mph. If the final reduction from the 88 federal could be put in the 1st gen that would get you there.

So I guess you would need to oversize your tires to get it up to what you want. The biggest worry would be that you would have to go an inch bigger in diameter per every 4% in raised gearing so you would end up having a car that is 1.5" taller to raise the gearing. But I suppose if you lowered the car a couple of inches that would make up for the drag. If you used HX rims you could go with the low rr sumitomo htr 200s in a 175/70-14 which would be 7% taller than the stock 165/70-13s that were the originals. That ought to get you down to around 1950 at 55.

Anyway keep up the good work. I'm going to butt out now but will be watching your progress. Don't be to discouraged in your first results. It looks to me that the real gains are in the rear and the underside of the car judging from basjoos's ride

[ebacherville]

Originally Posted by fritz

Anyway keep up the good work. I'm going to butt out now but will be watching your progress. Don't be to discouraged in your first results. It looks to me that the real gains are in the rear and the underside of the car judging from basjoos's ride

Good info about the gears.. any way yeah i also feel the rear and underside is going to make big gains.. not to mention that first tank had 1/3 of its miles in bad weather conditions .. high winds and heavy rain..