H22Honda98

I have been kind of at a loss on how to proceed the last few days.

Im finishing up a turbo build on my 98 prelude. Im using an F22B DOHC non vtec. Prior to right now, ive always had the F22 transmission. The F trans has painfully long gears and in general will makes the car a total dog. I always held onto it because of the old notion that the longer gears would be better for a boosted setup. nowadays, it seems that the consensus is that the opposite is true and ET's will almost always be better with a shorter gearset.

Well, i came across a great deal on an H23 trans and went ahead and picked it up, took out the F22 trans, and installed the H23 variant. The car feels much better overall, but here is my issue:

With the gears being so much shorter than before, combined with the fact that the F22B has a safe rev limit that hovers between 6500-7000, i am now at 7000 rpms in 4th at right about 98mph or so and being forced into 5th much earlier than i expected. I didnt take into accout that the F22B has such a short powerband, and now i wil be hitting 5th gear in the 1/4 mile for sure. The car will make about 330whp or so, and im expecting it to trap around 108-110.

what is the right move here for the fastest ET? Stick with the trans i have now and deal with hitting 5th gear? The 5th gear is pretty short so maybe that will help. is it not that big of a deal? Go back to the F trans? its tempting to just ditch the engine altogether and go find an H22 with a powerbad thats better suited to these short gears, but i recently replaced all the seals, timing belt, hg, and installed ARP head studs in this F22B and dont want it to go to waste...not to mention id need a new turbo mani. Maybe im making too big of a deal out of hitting 5th, but it seems that everyone avoids doing so. Im also semi concerned about the heat/stress that would come down on the engine with full boost WOT in 5th gear.

If there isnt any way to answer this without going down the track with both transmissions and seeing which performs better, thats fine and ill just have to see for myself. However, id much rather deal with all of this during the winter and be setup right for the spring time if you guys have some insight on this.

For reference, here are the gear ratios.

H23: 3.307 1.857 1.320 1.034 0.812 4.266
F22: 3.310 1.810 1.232 0.900 0.710 4.062

hondaracing84

iTrader: (1)

You want to avoid going into 5th. While some people have to do it, if you can get it set up where you top out in 4th right across the line, that is ideal. The more you have to shift, the higher your times will be. Simply because you're taking the time to make that extra shift. Plus that 5th gear isn't as easy to get into as 1-4, so the shift into 5 is a little slower than the rest.
What tires are you running and how tall are they? You might have to mess with tire size to get it right.
Another option to figure out gearing vs mph, is a gear calculator. MFactory® Competition Products - Gear Ratio Calculator
Check out that calculator. You can select pre made ratios from the drop down, or input them yourself. Then you can mess with tire size until you get the mph you want in 4th. That is the easiest way of figuring this out without the test n tune at the track.

motoxxxman

I can assure you that you won't be trapping that high with only 330hp in a 5g prelude; they're too heavy.
Like the guy above said, it'll really just boil down to tire size. Ideally you want to be just shy of the rev limiter in 4th when you cross the finish line. or if power takes a crazy nose dive, cross the line right before the nose dive. tire size makes a HUGE difference in rate of acceleration as well as actual vehicle speed at the end of each gear.

mathematically speaking, if the gear spread is roughly the same in both transmissions, with proper tire sizing for each tranny individually, they would actually perform identically. IE: a 22" tire with the f22 trans, and a 24.5" tire with the h22 trans would be nearly identical