H23 IM upgrade....still get good mileage?

[Losiracer2]

I have a spare H23 intake manifold that's not being used. But I'm wondering if adding that to my F22A1 would hurt the great mileage its getting right now. I'm averaging 29mpg every tank including rush hour traffic. So I really don't want to drop below that....too much.

I know it'll bump up the power which is what I'm going after somewhat. I just don't want it to hurt my gas mileage. Think I should add it to my otherwise stock DD, just has a AEM Cold Air intake on it since it helped my mileage by 3mpg.

[PakaloloHonda]

MPG is also dependent on driving habits. If you're stuck in rush hour, do alot of city driving
as opposed to all freeway, cruise control, conservative driving .. your mpg may vary ..

But seeing as how one of your cb7's gets 37mpg, I'm assuming you're not sitting in rush hour,
and gunning it all over the place in the city.
I've been dealing with strong head winds lately, and I've noticed that even though I'm on the high-way,
my mpg has suffered .. and I haven't thrown the H plenium in .. yet.

Many varibles contribute to good mileage. I doubt that most folks who have done the swap,
will come in stating that they've seen a considerable decrease in mpg, unless of course
they're simply jack-rabbiting off of every green light or doing alot of performance driving.
I'd be willing to bet that a cb7 with the H mani swap, along with a properly tuned motor,
a conscience and responsible driving habit, could get considerbly better mpg
than a cb7 without the swap, and a poorly tuned motor.

I don't believe you'll notice much at all, if anything .. I know when I put mine in,
I'll be using the same driving habits to see what, if any differences actually show them selves.

[Losiracer2]

MPG is also dependent on driving habits. If you're stuck in rush hour, do alot of city driving
as opposed to all freeway, cruise control, conservative driving .. your mpg may vary ..

But seeing as how one of your cb7's gets 37mpg, I'm assuming you're not sitting in rush hour,
and gunning it all over the place in the city.
I've been dealing with strong head winds lately, and I've noticed that even though I'm on the high-way,
my mpg has suffered .. and I haven't thrown the H plenium in .. yet.

Many varibles contribute to good mileage. I doubt that most folks who have done the swap,
will come in stating that they've seen a considerable decrease in mpg, unless of course
they're simply jack-rabbiting off of every green light or doing alot of performance driving.
I'd be willing to bet that a cb7 with the H mani swap, along with a properly tuned motor,
a conscience and responsible driving habit, could get considerbly better mpg
than a cb7 without the swap, and a poorly tuned motor.

I don't believe you'll notice much at all, if anything .. I know when I put mine in,
I'll be using the same driving habits to see what, if any differences actually show them selves.

yeah i figure if anything the 2-3x plenum volume should help boost mileage since there'll be more air capacity for the engine at any time. Oh and the 37mpg car is the one I'm talking about. Thats what I ususally get all highway, but when driving to work and back in downtown phoenix and hitting rush hour there and back it drops it considerably to that 29mpg figure. All city I usually get about 27mpg

[Jarrett]

I'd definitely give it a go if you have it lying around. But something I think would help it even further would be a plenum spacer. The extra long runners will help low end torque. That higher low end torque will cause the engine not to be in as high of a rev range to produce the same speed on the freeway. That's my opinion, anyway.

[Losiracer2]

I'd definitely give it a go if you have it lying around. But something I think would help it even further would be a plenum spacer. The extra long runners will help low end torque. That higher low end torque will cause the engine not to be in as high of a rev range to produce the same speed on the freeway. That's my opinion, anyway.

h23 runners are shorter than F22A6 runners, so you're saying to add another spacer below the IABs to furthur increase the plenum volume? I think if I put it above the IAB plate, that it'll cause some turbulence in the intake manifold by forcing the air in that pocket caused by the 4 ports of the spacer.

[Jarrett]

If you define the plenum as the space that contains the initial volume of air before it gets divided then no, it won't increase the plenum volume. I simply mean it as a way to effectively increase runner length. It won't matter if it's above or below the IABs. The range that you'll be improving mostly is during a period when the butterflies are closed anyway. It's the primary runners that you're concerned with when considering fuel economy. Adding a spacer will increase the runner length after the plenum and produce more low end torque.

[jewelproject]

soo...
h23 throttle body+plenum+runner
+extra spacer(gutted iab)=more low end torque?

[The G-Man]

I'd definitely give it a go if you have it lying around. But something I think would help it even further would be a plenum spacer. The extra long runners will help low end torque. That higher low end torque will cause the engine not to be in as high of a rev range to produce the same speed on the freeway. That's my opinion, anyway.

That's wrong. Engine speed vs. vehicle speed is directly dependent on the gear ratios of the transmission

[cloudasc]

The h23 runners are longer then the a6, so using the h23 runners will provide more low end torque then their a6 equivalent. Adding the spacer to an a6 runner setup effectively lengthens the runners to be equivalent (or damn near close to) to having an h23 runner setup. Personally I didn't notice a different in mileage with my swap, but I noticed the added power and intake noise that can turn heads from 3 blocks away using a stock airbox

[Losiracer2]

The h23 runners are longer then the a6, so using the h23 runners will provide more low end torque then their a6 equivalent. Adding the spacer to an a6 runner setup effectively lengthens the runners to be equivalent (or damn near close to) to having an h23 runner setup. Personally I didn't notice a different in mileage with my swap, but I noticed the added power and intake noise that can turn heads from 3 blocks away using a stock airbox

na I think its the other way around, H23 are shorter and F22A6 are longer.

[8ball]

f22a6 short runner small plenum.

h23a long runner big plenum.

i think thats why they hybrid the a6 bottom with a h23 up top/ short runners big plenum= high end power.

[islandhopper]

Read both threads. Should answer some questions.

http://www.cb7tuner.com/vbb/showthre...ht=h23+runners

http://www.cb7tuner.com/vbb/showthre...ight=H23+F22A6

[Jarrett]

That's wrong. Engine speed vs. vehicle speed is directly dependent on the gear ratios of the transmission

Understood, but the torque produced plays a big role in how much the engine is working achieve a given engine speed. If the two factors you gave were the only considerations then we would have found the magic ratios for X engine and have all of us getting 1000 miles to the gallon now.

[GunRunner]

I think that MPG change was what the question was about.

To OP:
I have an h23 upper laying around that I have had for sale for a while. I am about to do a tune up on my dd accord which averages about 32mpg. I have wondered if the MPG would change with this. I don't need/want the mod, but I do have the part just laying around.

So my setup for my dd accord woud be f22a6 runners, standard iab butterfly plate (operational), h23 upper plenium, f22a6 throttle body.

[Jarrett]

The F22A throttle body will not bolt up to the H22/H23 upper plenum.