Hybrid Transmission Parts - HF 5th & DX Final Drive

by **rankink** » Wed Jun 11, 2008 4:45 pm

As the title says I am looking into putting together a hybird transmission for my car. What I am trying to find is a CRX HF 5th gear and a CRX DX final drive gear separate from the transmission.

I have yet to find a place that just sells the gears online and was hoping anyone could suggest a place that might.

Thanks for your help in advance.

by **RamaCrx** » Wed Jun 11, 2008 6:03 pm

PM Mista Bone.

by **downest** » Wed Jun 11, 2008 6:30 pm

I'd prefer if you all post it publicly, that's the point of the forum after all.

by **crixer** » Wed Jun 11, 2008 7:53 pm

I would be interested in both of those as well if the good Dr. Bone comes into this thread....

by **Baker** » Wed Jun 11, 2008 8:17 pm

crixer wrote:I would be interested in both of those as well if the good Dr. Bone comes into this thread....

His infinite d series transmission wisdom comes in handy.

by **RamaCrx** » Wed Jun 11, 2008 8:35 pm

downest wrote:I'd prefer if you all post it publicly, that's the point of the forum after all.

Yes you are right!!

by **Mista Bone** » Wed Jun 11, 2008 11:06 pm

Paging Dr. Bone......STAT!!!!!!!!!!!

First, don't bother trying to find a HF 5th, settle on a 92-00 .702 5th, it fits.

No, I don't have one, just shipped my last one today, $25 shipped.

3.889 DX FD, I should have a few, I'm cheap!!!!!

OK, now lets find out about your car, it's mods, your plans and your driving style before deciding on 5th gear/FD choices.

by **crixer** » Wed Jun 11, 2008 11:13 pm

I want mpg on the hwy. I have a non-vtec sohc zc.

I am really interested in the jdm d15b 3 stage vtec. It sounds like what I am looking for. Great mpg driving normal, but If I need to pass someone or if I want to redline around it would give me a little bit of power.

any suggestions on a transmission setup for a d15b 3 stage? I spend most of life on the hwy, but I do like to rip around at night (I work at night, not much traffic so I can enjoy the streets... Under 60mph no racing...)

I was planning on using the hf 5th and dx final drive on my (i guess its the same as the si ) transmission. would that same transmission setup work on the d15b 3 stage good dr?

thanks,
Frank

:?:

by **Mista Bone** » Thu Jun 12, 2008 1:42 am

So your looking at 60 mph cruise yet stay on in the VTEC-E lean burn profile, I assume you plan on running the D15B 3 stage ECU right? Doesn't it need to stay below 3000 rpms for that?

Your best bet would be to get a DX tranny and swap the 5th gear

Now mind you my D15B7 did 53 mpg and them laid down 121 whp in same weekend without ANY changes.

4.058 FD with .702 5th. Don't think about gasmileage and low rpms, think about making the motor VERY effiecent at a somewhat normal RPM range.

You do courier work or something like it?

ALOT of the gains are in the ECU and driving style.

Stock P28 ECU timing maps on low cam

My chip Blundar of PGMFI.org did for me, fuel curves not shown, but leaned out at 10: vacuum and above

by **rankink** » Thu Jun 12, 2008 9:30 am

Mine is a 88 CRX Si. Stock. Working towards increasing mileage for daily driving and long trips. I don't care about power or having fun at night. I have a STi for that.

Right now I am dealing with the stock engine. I would normally like to just buy a DX transmission, but they are hard to find and do not want to pay the shipping for one elsewhere. Just easier to get the gears and have my friend install them in the tranny for free.

The 92-00 .702 5th is fine, too bad you are out.

I will take the 3.889 DX FD though.

by **RamaCrx** » Thu Jun 12, 2008 9:50 am

2 questions Mista Bone.

1) where can you buy the 5th gear you mentioned? Are they available other than junk yard?
2) If you lean your car out for highway driving, why is there no risk of detonation and frying things? What should be the goal for A/F ratio?

by **downest** » Thu Jun 12, 2008 10:23 am

I run my car a lot leaner at cruise. Since you're not under significant load, the cylinder pressures are relatively low and you won't break anything, if it gets too lean you'll just misfire. I usually can get it to around mid-16:1 AFR, then it misfires. Then you advance the timing a little and push it more, I can get my B17 to almost 19:1 AFR at cruise (350-400 mbar).

by **RamaCrx** » Thu Jun 12, 2008 10:46 am

downest wrote:I run my car a lot leaner at cruise. Since you're not under significant load, the cylinder pressures are relatively low and you won't break anything, if it gets too lean you'll just misfire. I usually can get it to around mid-16:1 AFR, then it misfires. Then you advance the timing a little and push it more, I can get my B17 to almost 19:1 AFR at cruise (350-400 mbar).

Does that translate into better MPG's? How much improvement?

by **downest** » Thu Jun 12, 2008 11:55 am

Slightly over 40MPG highway on a 12.5:1 B17A1 engine on a B16 tranny (cruising on the highway at 5 grand with the B16 5th gear).

by **RamaCrx** » Thu Jun 12, 2008 12:15 pm

downest wrote:Slightly over 40MPG highway on a 12.5:1 B17A1 engine on a B16 tranny (cruising on the highway at 5 grand with the B16 5th gear).

Any speculation what mpg's you could get with a d15b 1or 2 with mpfi conversion and I guess you would need to be obd1 and chipped ecu for economy?

Is this the 5th gear part number that you need for the 5th gear swap?

23581-P20-C00

Huge Link

by **Mista Bone** » Thu Jun 12, 2008 6:01 pm

#7 would be 1/2 of the gearset needed, easier to find a junk tranny for $25 and steal 5th gear.

Lean mixtures take forever to burn, hence the more timing needed. VX VTEC-E motor does the same thing, but only with one intake valve open

by **kenthefireman** » Thu Jun 12, 2008 10:53 pm

I have an 89 DX with a D16Z6 from a 95 Si. I used the 89 DX tranny and it is slow. I get around 35 mpg on the highway (75-80 mph). I would like to switch to the 95 Si trans and get a taller 5th. would the 96-00 5th be a good choice, and are there any other gears 1-4 that might help acceleration? Guess I am asking what is the ultimate NA Z6 trans. ( I have the tranny, just need the gears) Thanks

by **Mista Bone** » Fri Jun 13, 2008 2:21 am

rankink, I have the parts you need, see PM, including the 5th gear

ken, 89-91 DX = 92-00 EX in 5th gear

3.89 * .771 = 4.25 * .702

Plus you have to mess with trying to mount up a hydro tranny......which IMHO a stupid idea!

by **kenthefireman** » Mon Jun 16, 2008 12:56 pm

Not really looking for a taller 5th overall ratio, just a lower 1-4. If I could keep the 5th overall ratio in the same neighborhood and lower 1-4th that would be great. There are two problems I would like to solve. The first is the DX 1-4 gears suck for acceleration. The second, I did the swap because when I bought the car everything was worn out. The motor mounts included. I filled them in with urethane but they still need replacement. I can mount the hydro tranny with an Innovative kit, still cheaper than buying all new mounts from honda. So with the hydro tranny that came with the engine is there a good setup for driving around with a taller 5th gear option? Anyway, if I stay with this setup (DX tranny) what would be a good idea 88-91 Si final drive? Thanks.

by **fireant** » Fri Nov 14, 2008 11:52 am

This is a great thread. I'd like to know exactly what parts are needed to put a .702 5th into an otherwise stock Si L3, and what kind of RPM changes would result at 60 or 70mph.

~edit~

THis thread looks promising:
http://crxcommunity.com/viewtopic.php?p=18946

by **Mista Bone** » Sat Nov 15, 2008 2:56 am

you need both 5th gears, aka gearset.

RPM vs. MPH of various 5th gears

5th gear-----FD------45------60------80------100---
0.702------4.058---1898---2530---3373---4217--
0.702------4.250---1988---2650---3533---4417--
0.750------4.250---2123---2831---3775---4718--
0.771------4.250---2183---2910---3880---4850--
0.878------4.250---2486---3314---4419---5523--

by **noypistah** » Sat Nov 15, 2008 4:53 am

238 miles and still 3/4 tank..... i wish my HF could do that..

by **Mista Bone** » Sat Nov 15, 2008 6:37 pm

noypistah wrote:238 miles and still 3/4 tank..... i wish my HF could do that..

First you have a 5L smaller tank but also the setup it overgeared. GREAT on flatland....but come to a hill and downshift....

by **noypistah** » Sat Nov 15, 2008 6:53 pm

so how much MPG do you really get?

by **Hybrid88** » Sat Nov 15, 2008 8:26 pm

hey bone do you mind sharing your bin file?

Hybrid Transmission Parts - HF 5th & DX Final Drive

Hybrid Transmission Parts - HF 5th & DX Final Drive

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