H22 LSD gas saving idea/tips...

[Straight Success]

I recently told this idea to JakfrostWhite. I have been calling around asking performance tranny shops if they could remove the 5th grear from the LSD H22 tranny and replace it with a F22 5th gear. I would still reatin gears 1-4 for the quicker acceleration from the H (when racing you barely use 5th). I would use the 5th gear off of the f22 tranny to lower rpm when driving on the highway.

Feedback is greatly appreciated.

This set-up:

JDM H22A 92-96 PRELUDE VTEC COUPE:

Diff Type & Tranny Codes:
STD = M2A4
LSD = M2B4

3.307 1
1.950 2
1.360 3
1.034 4
0.787 5
4.266 final

Changed gears:

3.307 1
1.950 2
1.360 3
1.034 4
0.685 5
4.062 final

[The G-Man]

You want to change the FD too?

[Straight Success]

Yup, if possible.

[C91BLX7]

Yup, if possible.

Then you fuck up 1-4

[Straight Success]

Well, how can I do this set up correctly?

[The G-Man]

Yup, if possible.

I would try and keep the FD and just simply put or get the F22 5th, or a custom ratio put in there.

I would say custom ratio, because I think you would need a gear cut for it anyways. Because AFAIK the F22 5th can't just be swapped in.

[Karl]

the gear change make a large difference if you can just keep the speed down. I swapped the other way from the accord gear to the final drive from the lude and only lost 3mpg highway @75-80.

[owequitit]

Overall drive with H22 gearing:

14.10 - 1st

8.32 - 2nd

5.80 - 3rd

4.41 - 4th

3.36 - 5th


Ratios with F22 5th and FD:

13.43 - 1st

7.92 - 2nd

5.52 - 3rd

4.20 - 4th

2.78 - 5th

% difference in overall drive:

-7% - 1st

-5% - 2nd

-5% - 3rd

-5% - 4th

-17% - 5th

So you can see that just changing to the Accord final drive with H22 gears 1-4 costs you about 5-7% of your gearing. While the combo of F22 5th and FD, costs you almost 18% of your gearing.

How does this affect performance? By reducing the amount of torque at the wheels. Let's assume the stock USDM torque rating of 156 lb/ft. For simplicity's sake, we will assume that the torque reading occurs without loss through the transmission, even though the actual wheel values would be smaller.

This is the torque you would see at the wheels with H22 gearing:

(overall ratio - gear # - total torque to the wheels)

14.10 - 1st - 2199.6 lb/ft

8.32 - 2nd - 1298.0 lb/ft

5.80 - 3rd - 904.8 lb/ft

4.41 - 4th - 688.0 lb/ft

3.36 - 5th - 524.16 lb/ft

With the hybrid gearing you propose, here are the results.

(overall ratio - gear # - total torque to the wheels)

13.43 - 1st - 2095.1 lb/ft (-5%)

7.92 - 2nd - 1235.5 lb/ft (-5%)

5.52 - 3rd - 861.1 lb/ft (-5%)

4.20 - 4th - 655.2 lb/ft (-5%)

2.78 - 5th - 433.7 lb/ft (-21%)

So you can see that the F22 FD will drop your wheel torque an average of 5% through the first 4 gears, and by using the F22 5th gear, you lose a whopping 21% of your wheel torque.

Here is why that is not necessarily a guaranteed fuel savings. If you use 5th gear at all around town or at less than say 70-80MPH, you will have to down shift into 4th gear, in order to maintain speed in situations when you could have stayed in 5th with the H22 tranny. The problem with that is, that you are now in a gear that is LOWER overall than 5th gear is on the H22, thus you are probably using more fuel. The lower gearing of the H22, will also make the engine feel more responsive. I routinely cruise around in 4th gear at 30MPH with my RPM's at or below 2000. If I had an F22 tranny, I would have to be in 3rd gear, and thus I would have to tool around in a gear that is 21% lower than my current 4th gear.

There is a lot more to saving gas with an engine, than just giving it higher gearing. While that will usually on the face value, or in the EPA test (which is useless for real world IMO) save you fuel, there are a whole slew of tradeoffs that go with it. That is why Honda pays a large staff of engineers to optimize things like gearing. On a high strung H22, it would probably do more harm than good. Not only would you end up cruising around in lower gears, but you would spend more time at WOT, in higher gears, which would in turn increase injector pulse width, which would in turn burn more fuel. Couple that with the longer duration that you spend accelerating at WOT, and you might not see any fuel savings at all, and dare I suggest a potential loss.

Case in point. Ray had an H22 with F22 tranny in it. I get better mileage than he did, routinely turning in 30MPG city or just less than that, depending how I drive it. If I stay out of VTEC, 30MPG is a reasonable number. If I stick it a lot, then it usually falls to 26-27 MPG. On the highway, I have seen as high as about 35-36 in steady cruising on relatively level ground, although a more reasonable estimate is probably about 30-32MPG. Both are substantially better than what my stock F22 did, and the H is pretty much just as stock as the F22 numbers I am giving.

On the highway, you would probably see a 2-3 MPG increase, which does amount to a 10% savings or so. But you could easily offset that in the city, if everything isn't optimized just right.

Either way, it probably isn't worth the effort. Figured at $5 per gallon, you would save approximately $8.50 per tank IF and only if you saw a 10% total fuel savings. Might be worth it, but then again, why would you swap an enthusiast engine into your car, and then cut down the responsiveness substantially by putting the wrong gearing on it? We haven't even gotten into things like powerband yet.

If you want MPG, take a stock F22 and do a few simple mods to open up the flow, and you will get good MPG.

Overall, IMO, the H22 works best with H22 gearing.

[customchord]

You can't put a F series 5 gear in a H trans. The housings are the same but the internals are a little different. Supergenus was talking about this in another thread somewhere but you could get a special gear made. I have always thought that would be the best setup ever. Or some kinda 6 speed.

[Granite CB7]

^Yup, many have tried, I remember reading threads about this from '04!

Scott really donated alot to this thread, I have to say, he had some great points I'd say just leave the H tranny alone, obviously the M2B4 has the longest or 1 of the longest 5th gears out of the H family.

When driving and not dogging on the motor, I rev. my F22 very low (F22a6 w/ stock H2U5 tranny + 205/50/15, M2B4 very soon) once I hit 40ish, I'm already in 5th revving at 1500, so I do rev it pretty low.

[owequitit]

^Yup, many have tried, I remember reading threads about this from '04!

Scott really donated alot to this thread, I have to say, he had some great points I'd say just leave the H tranny alone, obviously the M2B4 has the longest or 1 of the longest 5th gears out of the H family.

When driving and not dogging on the motor, I rev. my F22 very low (F22a6 w/ stock H2U5 tranny + 205/50/15, M2B4 very soon) once I hit 40ish, I'm already in 5th revving at 1500, so I do rev it pretty low.

I was driving around at 40MPH in 5th gear and the engine was perfectly happy with it. I was tooling at about 1800RPM, and had barely any throttle. usually, I cruise around in 4th at that speed.

Keep in mind it was a 90* day at 5,000-6,000 feet above sea level. With an F22 tranny, I never would have been able to do that. It would have been lugging down around 1300-1500 RPM, and would have been unhappy. Obviously, with the H22 in 5th gear at 1800 RPM, I didn't have TONS of get up and go, although I could generally maintain the pace of traffic without much issue. And if you are driving for MPG, then you don't want to accelerate fast anyway.

Personally, I think it would be easier and nearly as effective to just adapt driving style.

[Losiracer2]

man I wish I had a manual! its so much fun to "adapt driving style" in manual equipped cars, ugh. I hate my Auto and its jerky shifts.

[owequitit]

man I wish I had a manual! its so much fun to "adapt driving style" in manual equipped cars, ugh. I hate my Auto and its jerky shifts.

Adapting driving style applies just as much to autos, they just generally won't achieve the same numbers because they are less efficient, and they have fewer gears.

My mom's 06 equals my car in MPG with no issues or babied driving. I used to get GREAT gas mileage with my auto.

[Straight Success]

I drive my auto like it is a stick. I have been doing that for about 3 or 4 years now. See why I need a manual.

Oh yeah, before anyone comments about my driving habits, I will just inform you all that I service my tranny every year, and it stills shifts pretty damn good. I've heard that messes up the tranny, but it's been working pretty good so far. Even when I am normal driving and I leave the car in D4, the computer seems to generate smooth shifts still. Tiptroic without actual tiptronic. I know your thinking that I may run into problems down the line. As for now it's holding up pretty good. I'd say I have at least another 24 months on this tranny. Maybe Honda just builds a transmission that you can abuse.

An old friend of mine, beat the blood out of his Civic for years. He went about 18+ or so months without an oil change. The car just kept running strong.

[mj213]

Reminds me of that youtube video with the guy pouring water in the block, even while it was running, it took a while to kill the motor.