h22 tranny vs. f22 tranny

[JohnD1079]

ok i know that H anf F tranny are interchangable. but my question is, on a H22 when you have a F22 tranny are the RPMs the same as it would be on the H22 tranny. like i kno a H22 with tranny is around 3200 rpms at 69 mph. and a f22 with its tranny is at around 2600 rpms. so if a had the H22 with a f22 tranny which rpm would it be. If its the same rpm as f22, wouldnt it be better to have that setup bc you get the power of the H22 but the rpms of a f22 which equals somewhat of better fuel economy?

[N9netwoAccord]

ok i know that H anf F tranny are interchangable. but my question is, on a H22 when you have a F22 tranny are the RPMs the same as it would be on the H22 tranny. like i kno a H22 with tranny is around 3200 rpms at 69 mph. and a f22 with its tranny is at around 2600 rpms. so if a had the H22 with a f22 tranny which rpm would it be. If its the same rpm as f22, wouldnt it be better to have that setup bc you get the power of the H22 but the rpms of a f22 which equals somewhat of better fuel economy?

the power of the motor has nothing to do with the gearing, thats all inside the tranny. the f22 tranny has longer gearing for better fuel economy while the h22 has shorter geras for quicker acceleration

[SleepersOwn]

I think he realizes that. The question is which would better for fuel economy. I could have sworn there were some threads on here that has some people with that setup comments. I could be wrong though.

If i'm not mistaken most people only have that setup because they're saving for an h22 tranny.

Eh, i'll try to find more info for you if no1 else chimes in.

[mozzandherb]

I'm assuming having an f series tranny would have better fuel economy, but I doubt it would be all that much better and in the end you will probably want the h series with the h22, so I would sacrifice the little amount of fuel economy for the better acceleration.

[palinix]

so if a had the H22 with a f22 tranny which rpm would it be.

Same RPM as with an F22 motor.

If its the same rpm as f22, wouldnt it be better to have that setup bc you get the power of the H22 but the rpms of a f22 which equals somewhat of better fuel economy?

Yes, better fuel economy, but longer gearing meaning slower acceleration.], just to name one performance disadvantage.

[areem57]

If your looking for fuel economy, you shouldnt be swapping in an H22.

[JohnD1079]

i am asking this bc my cousin has a h22 prelude, and he cruises on the highway at 69 mph bc if he goes any faster stage 1 of vtec kicks in and his economy drops. if i swap in a h22 i dont wanna have to drive like that just bc of economy. cuz i kno stage 1 of vtec kick in at like 3500 rpm, i think. i want to be able to cruise down the highway at like 80-85 without getting drastically worse fuel economy. do you guys get what im trying to say. i know about the acceleration wise, im asking about the cruising. when i travel, which i do alot, i like to go 85-95 and i dont want to really change that.

[cloudasc]

In the end doesn't all just come down to gear ratios? Shorter = more tq, longer = more hp. TQ is for accelleration, HP is to fight aerodynamic drag at high speeds. I'd say tune your 4th gear to 3500rpm at 60mph, which at 7k would take you to 120. Tune your 5th gear to 3500rpm at 100mph, which at 7k would take you 200mph. You'll probably never go that fast, but you'd be using your 5th gear as gas saver. This makes it under the assumption that 3600rpm is when stage 1 vtec kicks in on your motor.

[NAiL05]

Where did you get longer = hp? Short gears are a torque multiplier. IF you want gas mileage go for the f trans. Dont be tuning gears whatever the F trans is fine as is. H trans if you want performance. Either way the H trans doesnt get that bad of gas mileage if your car is properly tuned up and you dont hit the go pedal as much. I cruise at 3800-4000 all day doing 80 and I can careless. If your so worried about fuel just get the F trans. Or just keep the stock motor as is.

[AccordXRacer]

I agree with Nail 100%

[owequitit]

The F tranny should provide better economy as has been mentioned.

But there is a downside.

The taller gearing means you spend more time accelerating, and thus spend more fuel while accelerating.

So to some extent, the difference is offset by time spend accelerating.

What that means to you is that the fuel economy won't be much different.

I routinely get 26MPG city without babying it and 32 Highway without babying it. That is with the H tranny.

Also, there is only 1 stage of VTEC, and it doesn't engage until 5K or so.

The only other thing there is are the secondary butterflies in the intake, and they shouldn't open until at least above 4K.

[cloudasc]

Where did you get longer = hp? Short gears are a torque multiplier. IF you want gas mileage go for the f trans. Dont be tuning gears whatever the F trans is fine as is. H trans if you want performance. Either way the H trans doesnt get that bad of gas mileage if your car is properly tuned up and you dont hit the go pedal as much. I cruise at 3800-4000 all day doing 80 and I can careless. If your so worried about fuel just get the F trans. Or just keep the stock motor as is.

So the whp doesn't increase as the gears get longer, while the torque decreases?

[Hondatuner998]

I have a friend who has had both trannies with his H22 and is a nut about gas mileage. Now he didnt originally change them for gas mileage. The F went and he went with the H22 because he was more interested in the acceleration over the gas mileage. Anyways, he did the math and found out that there was only an average of 2 to 3 mpg difference. But more often then not it was 1.75 to 2.5 mpg difference.

[deevergote]

The F22 has a longer 5th gear, so if you spend a lot of time at 65+ mph, you'll see better highway mileage. But as owequitit said, you spend more time accelerating, so you burn more when you're not just cruising.

The difference is negligable. I like the H22 tranny because the gearing matches the powerband of the motor. I regularly get 28-32mpg, about half highway, half city. That's with a decent MRX tune though! I got about 25 before that.

[owequitit]

So the whp doesn't increase as the gears get longer, while the torque decreases?

The gearing has nothing to do with "WHP" per se, at least not in the context that people consider it.

Most people consider "WHP" to be the % of power that makes it to the ground. So if my engine is 100HP with a 15% loss, I expect 85HP to make it to the drive wheels.

You are getting confused by the application of torque via gearset.

A gear simply multiplies torque.

Let's say for example that our H22 is producing 161lb/ft of torque.

And our H22 tranny is in 1st gear, which has a ratio of 3.28, and an axle ratio of 4.266.

To get our wheel torque, we take our Engine torque, and mulitply it by the 1st gear ratio, and then the axle ratio.

This gives us the final drive ratio. In our case it would be 3.28 * 4.266 = 13.99

So we get:

163*3.28*4.266 = 2280lbs/ft of torque.

Now if we go down to 2nd gear, which has the same axle ratio, but the gear ratio changes to 1.956, this is how the result changes.

163 * 1.956 * 4.266 = 1360 lb/ft of torque.

So you can see that even though we aren't producing more torque at the engine, we are producing more at the wheels, by virtue of the gear ratios and their multiplier effect.

It also makes it very clear how lower gears make you accelerate faster. By the time the torque is multiplied through the system, we get more at the ground with lower gears.

The downside is higher RPM's for a given speed.

Normally, dyno runs are done in the gear that gives the ratio closest to 1:1, which on most modern 5 speed cars is 4th gear.

This helps to minimize the error associated with the gearing, because at 1:1, we are only multiplying by the axle ratio.

If we know that number (4.266 with our H22 tranny) then we can take our dyno results, and have the computer correct them back a 0 multiplier.

So in a sense, you are correct about the torque decreasing with speed and higher gears, but the HP doesn't really change. Mathematically, HP is a function of torque and RPM, but if torque goes down, then calculated HP would also go down, so if anything, it would decrease also with speed and not increase.

For the sake of keeping argument and discussion simple, the gearing is usually left out.

Dynos are another matter entirely. They basically measure how long it takes to accelerate a weight. They know the RPM, so they can calculate from there.

And yes, gear ratio on the dyno does have an effect on measured HP. Obviously the weight will accelerate faster in 1st gear, that it will in 4th by virtue of the torque multiplier.

It can get complicated quickly. LOL!