CRX HF Transmission into Civic Sedan
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From: Salt lake City, UT
CRX HF Transmission into Civic Sedan
Another similar thread got me thinking again about my desire to increase my gas mileage.
Before the head blew I was getting 40+ mpg on the highway. It may be the same now but I havn't had much of a chance to test it.
I'd love to increase that number.
FIrst question, could I just swap the 89 HF transmission into the Sedan (does it bolt right in)?
Second question, could I make a "hybrid" transmission where I took the 5th gear out of the HF Transmission and put it into a standard Sedan transmission?
Third question, how difficult would it be for me to make this "hybrid transmission?"
Fourth question, does anyone have a 89 HF tranny they want to donate/sell?
*edit: Looks like I forgot to mention I have an 89 Civic LX
Before the head blew I was getting 40+ mpg on the highway. It may be the same now but I havn't had much of a chance to test it.
I'd love to increase that number.
FIrst question, could I just swap the 89 HF transmission into the Sedan (does it bolt right in)?
Second question, could I make a "hybrid" transmission where I took the 5th gear out of the HF Transmission and put it into a standard Sedan transmission?
Third question, how difficult would it be for me to make this "hybrid transmission?"
Fourth question, does anyone have a 89 HF tranny they want to donate/sell?
*edit: Looks like I forgot to mention I have an 89 Civic LX
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From: colorado springs, co, usa
Re: CRX HF Transmission into Civic Sedan (SiMateoAko)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SiMateoAko »</TD></TR><TR><TD CLASS="quote">PM me if you are interested in unloading it.
Will a 88 HF Tranny be compatible with a 89 LX?</TD></TR></TABLE>
only if you also swap in 88 clutch disc
Will a 88 HF Tranny be compatible with a 89 LX?</TD></TR></TABLE>
only if you also swap in 88 clutch disc
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From: Salt lake City, UT
Re: CRX HF Transmission into Civic Sedan (dr_latino999)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dr_latino999 »</TD></TR><TR><TD CLASS="quote">No, the splines on the input shaft are different so you will need a different clutch disk.</TD></TR></TABLE>
Looks like I should just be on the lookout for a 89 HF tranny, eh? I don't need to swap everything out...
I'd actually just prefer to make the hybrid tranny. Maybe I should get a tranny from the salvage yard for a 89 LX and wait until I can get a 89 HF to play with.
Looks like I should just be on the lookout for a 89 HF tranny, eh? I don't need to swap everything out...
I'd actually just prefer to make the hybrid tranny. Maybe I should get a tranny from the salvage yard for a 89 LX and wait until I can get a 89 HF to play with.
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Re: CRX HF Transmission into Civic Sedan (SiMateoAko)
Don't do the Hybrid Tranny.
I LOVE when I see that people think that if they have a good 5th gear, they'll get the 50mpg...
THE VAST MAJORITY of your gas mileage is determined by your acceleration.
If you put the entire long geared HF transmission in, you'll get better mileage.
If you do just the 5th gear, you'll get good highway mileage...
Only problem is, drivability will become a concern.
I don't know if people notice, and so I point it out all the time, The HF is MUCH MUCH MORE than a long geared Transmission.
The Engine in the HF is paired perfectly w/ that transmission.
The HF has very long gears, BUT, the D15b6 makes 90ft lbs @ 2000 RPM.
Thus, despite the fact that one rarely goes over 2000 RPM, the performance is actually optimized for that.
If you put in any other Honda engine, it's going to suck...Torque (What little there is) is made 3-6K RPM. With that transmission, there's no way it would be driveable...
So, in closing, we have concluded:
1. To actually get the better gas mileage, you'll need more than a nice 5th gear, as most of your mpg is determined by your acceleration habits.
2. The HF transmission is designed w/ a Low RPM for Torque engine, which is nothing like pretty much any honda engine...In fact, the D15b6's performance characteristics are more similar to a diesel (I like to think of it as a Gas diesel
).
I LOVE when I see that people think that if they have a good 5th gear, they'll get the 50mpg...
THE VAST MAJORITY of your gas mileage is determined by your acceleration.
If you put the entire long geared HF transmission in, you'll get better mileage.
If you do just the 5th gear, you'll get good highway mileage...
Only problem is, drivability will become a concern.
I don't know if people notice, and so I point it out all the time, The HF is MUCH MUCH MORE than a long geared Transmission.
The Engine in the HF is paired perfectly w/ that transmission.
The HF has very long gears, BUT, the D15b6 makes 90ft lbs @ 2000 RPM.
Thus, despite the fact that one rarely goes over 2000 RPM, the performance is actually optimized for that.
If you put in any other Honda engine, it's going to suck...Torque (What little there is) is made 3-6K RPM. With that transmission, there's no way it would be driveable...
So, in closing, we have concluded:
1. To actually get the better gas mileage, you'll need more than a nice 5th gear, as most of your mpg is determined by your acceleration habits.
2. The HF transmission is designed w/ a Low RPM for Torque engine, which is nothing like pretty much any honda engine...In fact, the D15b6's performance characteristics are more similar to a diesel (I like to think of it as a Gas diesel
).
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From: 32514, fl, usa
Re: CRX HF Transmission into Civic Sedan (SiMateoAko)
Part of the HF's fuel economy was also it's low weight (and less drag because of the body style compared with the sedan) and it's cylinder head/intake setup. The engine is choked up from the get go and just doesn't use a lot of fuel.
40mpg is pretty damn good.. my old mini-me was getting 37mpg with the A/C on at 80mph.
It seems that the A/F mixture is better around 4k RPMs than it is at 2500 RPMs.
So if you take all that into consideration, plus the cost of actually doing the swap and a new clutch, it could potentially take you years to make up the $ saved in fuel.
Just some things to consider before you start tearing into it.
40mpg is pretty damn good.. my old mini-me was getting 37mpg with the A/C on at 80mph.
It seems that the A/F mixture is better around 4k RPMs than it is at 2500 RPMs.
So if you take all that into consideration, plus the cost of actually doing the swap and a new clutch, it could potentially take you years to make up the $ saved in fuel.
Just some things to consider before you start tearing into it.
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From: Salt lake City, UT
Re: CRX HF Transmission into Civic Sedan (d357r0y)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by d357r0y »</TD></TR><TR><TD CLASS="quote">Part of the HF's fuel economy was also it's low weight (and less drag because of the body style compared with the sedan) and it's cylinder head/intake setup. The engine is choked up from the get go and just doesn't use a lot of fuel.
40mpg is pretty damn good.. my old mini-me was getting 37mpg with the A/C on at 80mph.
It seems that the A/F mixture is better around 4k RPMs than it is at 2500 RPMs.
So if you take all that into consideration, plus the cost of actually doing the swap and a new clutch, it could potentially take you years to make up the $ saved in fuel.
Just some things to consider before you start tearing into it. </TD></TR></TABLE>
You make a very valid point. Sometimes I get such a hard-on for gas mileage that I forget about the cost of saving a few pennies. All this for a car I don't drive too often (I work at home).
40mpg is pretty damn good.. my old mini-me was getting 37mpg with the A/C on at 80mph.
It seems that the A/F mixture is better around 4k RPMs than it is at 2500 RPMs.
So if you take all that into consideration, plus the cost of actually doing the swap and a new clutch, it could potentially take you years to make up the $ saved in fuel.
Just some things to consider before you start tearing into it.
</TD></TR></TABLE>You make a very valid point. Sometimes I get such a hard-on for gas mileage that I forget about the cost of saving a few pennies. All this for a car I don't drive too often (I work at home).
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From: Madison, WI, United States of America
actually, if you do a mini-me on it with an mpfi conversion, it will get better gas milege.
the mpfi conversion will add better control of the gas going in, and the mini-me will make it into a 12-valve in lower rpm's, giving you more efficiency and low end torque.
the mpfi conversion will add better control of the gas going in, and the mini-me will make it into a 12-valve in lower rpm's, giving you more efficiency and low end torque.
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From: Central Texas
Re: CRX HF Transmission into Civic Sedan (TheSSG)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TheSSG »</TD></TR><TR><TD CLASS="quote">
I don't know if people notice, and so I point it out all the time, The HF is MUCH MUCH MORE than a long geared Transmission.
The Engine in the HF is paired perfectly w/ that transmission.
The HF has very long gears, BUT, the D15b6 makes 90ft lbs @ 2000 RPM.
Thus, despite the fact that one rarely goes over 2000 RPM, the performance is actually optimized for that.
The HF transmission is designed w/ a Low RPM for Torque engine, which is nothing like pretty much any honda engine...In fact, the D15b6's performance characteristics are more similar to a diesel (I like to think of it as a Gas diesel ).</TD></TR></TABLE>
The HF gets its long gearing from the combination of the gearset and the final drive. He's only talking about using the HF 5th gear.
Put that HF 5th into an otherwise Si tranny and you will see a 500rpms drop compared to an Si 5th.
ie
Stock Si: 4000 rpms @ 80mph in 5th
HF/Si hybrid: 3500 rpms @ 80mph in 5th
I don't know if people notice, and so I point it out all the time, The HF is MUCH MUCH MORE than a long geared Transmission.
The Engine in the HF is paired perfectly w/ that transmission.
The HF has very long gears, BUT, the D15b6 makes 90ft lbs @ 2000 RPM.
Thus, despite the fact that one rarely goes over 2000 RPM, the performance is actually optimized for that.
The HF transmission is designed w/ a Low RPM for Torque engine, which is nothing like pretty much any honda engine...In fact, the D15b6's performance characteristics are more similar to a diesel (I like to think of it as a Gas diesel
).</TD></TR></TABLE>The HF gets its long gearing from the combination of the gearset and the final drive. He's only talking about using the HF 5th gear.
Put that HF 5th into an otherwise Si tranny and you will see a 500rpms drop compared to an Si 5th.
ie
Stock Si: 4000 rpms @ 80mph in 5th
HF/Si hybrid: 3500 rpms @ 80mph in 5th
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