Matt Timion
09-29-2005, 09:56 AM
As many of you know, I'm building a setup for my car to get max MPG. I'm putting in a vtec-e engine, which is honda's most fuel efficient engine. I am also going to put in a CRX HF transmission due to the longer gears.
Recently someone on another forum said that the DX transmission is actually better than the VX/CX transmission (the VX is the car the vtec-e engine came from. The CX transmission is exactly the same). They have said that using the VX/CX transmission you have to use more gas to get up to speed, so it actually hurts fuel economy.
What they said:
The reason a Dx trans would be better than the HF or VX is simply because of traffic and hills; the super economy tranny's would lug the engine really hard in stop and go and climbing big hills. Provided if you live in the central midwest with no hills or neighbors, then I would say go for the H/V box.
You are going about this in a 88-91 civ chassis right? The gearing in the transmission is only a single part of this equation, and a very easy to anticipate the results of any change to it, ie. gear swaps, final drive changes. I think that using a DX 1-4gearset and FD (3.83) with a HF fifth(.690) or a hydro Ex,Dx,Lx fifth gear(.702) will give you a very streetable trans with great freeway cruising.
Exactly. The cx/vx trans are geared SO tall that it usually requires additional throttle input from the driver just to get the car moving at a reasonable rate of acceleration, more than what would be required with the dx gears. Plus to keep the engine rpms where fuel consumption would normally be at its most efficient with the cx/vx final drive, in 5th gear you end up travelling at speeds where wind resistance becomes a major drawback (and well over the posted speed limit on most roads in most countries).
So once again I'm torn as to what I am to do. Do they make good points? Should I not worry b/c the d15z1 has enough HP (92HP at 4500RPM) to overcome the tall gears?
Will my HF transmission end up hurting me more than helping me?
Recently someone on another forum said that the DX transmission is actually better than the VX/CX transmission (the VX is the car the vtec-e engine came from. The CX transmission is exactly the same). They have said that using the VX/CX transmission you have to use more gas to get up to speed, so it actually hurts fuel economy.
What they said:
The reason a Dx trans would be better than the HF or VX is simply because of traffic and hills; the super economy tranny's would lug the engine really hard in stop and go and climbing big hills. Provided if you live in the central midwest with no hills or neighbors, then I would say go for the H/V box.
You are going about this in a 88-91 civ chassis right? The gearing in the transmission is only a single part of this equation, and a very easy to anticipate the results of any change to it, ie. gear swaps, final drive changes. I think that using a DX 1-4gearset and FD (3.83) with a HF fifth(.690) or a hydro Ex,Dx,Lx fifth gear(.702) will give you a very streetable trans with great freeway cruising.
Exactly. The cx/vx trans are geared SO tall that it usually requires additional throttle input from the driver just to get the car moving at a reasonable rate of acceleration, more than what would be required with the dx gears. Plus to keep the engine rpms where fuel consumption would normally be at its most efficient with the cx/vx final drive, in 5th gear you end up travelling at speeds where wind resistance becomes a major drawback (and well over the posted speed limit on most roads in most countries).
So once again I'm torn as to what I am to do. Do they make good points? Should I not worry b/c the d15z1 has enough HP (92HP at 4500RPM) to overcome the tall gears?
Will my HF transmission end up hurting me more than helping me?