Regearing my Honda (1994 Del Sol VTEC)

[evolutionmovement]

JDM options are a good idea to look into. I don't know Hondas well, so you'd have to research the overseas ratios, but there might be something with an excellent combo not available in the US. The JDM Subarus generally had shorter FDs, but maybe the Hondas are different.

The problem with Hondas in general is their lack of torque which precludes tall gearing. Manufacturers have to compromise for the general public and give them enough power to pass on the highway, for inclines, etc. in top gear without having to downshift. Personally, I think that's what 4th and 3rd are for, but marketing departments seem to disagree.

[theunchosen]

The car should do better than 24 for sure. Check the exhaust. They have a habit or rusting out and falling apart. It radically reduces FE for some reason, if it happens right next to the muffler. Anywhere else and you won't notice but right there it has an effect. I think the way the under belly turns its creates a high pressure zone opposed to a low pressure one that exists at the rear(forcing exhaust out rather than it being sucked out).

I went from like 26 to 33 with just that. Went for lighter weight tires and wheels and now I am looking at Trans fd swap because I'm going to replace my clucth with a lightweight high performance clutch that I picked off a car that came through and the guy insisted on replacing it with a stock one. . .:rollseyes:

[Shortie771]

I realize i should be getting better than 24mpg and i used to get somewhere in the 30's (i got 38mpg when i took a trip to florida in november) but ever since my o2 sensor went bad my FE has dropped a lot, also i need to stop by the gas station and air up my tires a bit ive noticed they have gotten a bit low... Im not really too concerned about my cars HP because its a daily driver but i dont want to turn that thing into a commenly reffered "Del Slow" if i do a full tansmition swap i would fall out of VTEC and i made a point of getting a Del Sol with a VTEC because i wanted the the one with a little extra power. I think if i have the VTEC i might as well keep it a VTEC. You all probably think im being nieve or something because i make it seem like i want the perfect balance of FE and HP, but thats not really how it is i just dont see the point in having the bigger VTEC engine and then taking away the whole purpose of the VTEC. I know, i know im complicated i get that a LOT. I understand that it may be easier to do a full tranny swap but my friend and i have plenty of time on our hands and we dont mind doing something productive with that time, so i think i might end up being complicated and do a 5th gear swap with a taller one, but still havent quite decided yet. Either way i go ill still need money so ill have to wait for my paycheck from the army (takes forever sometimes, working on straightening out my direct deposit) so for now im just doing little cheap projects. Today i put a temporary cardboard grill block on that i spay painted black. Ill admit it doesnt look very good but i hope it will do a little for my FE

Oh and btw thanks everybody for all the advice and input

[MadisonMPG]

Buy a new o2 sensor.

[evolutionmovement]

Yes, get a new O2. You can get generic ones pretty cheap, just try to get one with the same number of wires for best results.

I've never rebuilt a transmission myself, but a friend of mine builds high performance ones and it's not as easy as just slipping gears on and off. Get a factory service manual if you want to go that route so you know all the tolerances, lash, etc. You'll also have to find out if the gears are compatible, though I would guess they are.

[theunchosen]

Originally Posted by evolutionmovement

Yes, get a new O2. You can get generic ones pretty cheap, just try to get one with the same number of wires for best results.

I've never rebuilt a transmission myself, but a friend of mine builds high performance ones and it's not as easy as just slipping gears on and off. Get a factory service manual if you want to go that route so you know all the tolerances, lash, etc. You'll also have to find out if the gears are compatible, though I would guess they are.

I've never rebuilt one either, although I've taken them apart and fixed pieces(by rebuilt I'm assuming replacing large chunks, for an engine replacing the pistons. . .?).

You'll need stable mounts to slide under your reinforced plate and to take apart half of the engine bay. If you go for a swap you just undo all the taking apart with the new trans. If you don't. . .you have to disassemble the trans housing, carefully take all the gears out and place them away from damaging particles(unless you want to thoroughly scrub them to remove all debris) and then swap the 5th gear and then rebuild.

Seriously, buy a trans with low miles off either a wrecked one or a retired one. The advantage is saves lots of time and if or when you break something on the trans you have a whole second set to grab parts from.

Also. . .the V-TEC does have more power, but changing the gear ratios is going to sacrifice some of the quickness for top end speed. There is no way around that. If you want taller gears you have to sacrifice quickness.

I have two del sols to play with and personally 1st gear is way too low and second is pretty short as well. Both of them being taller would definitely increase quickness because you have to shift out almost immediately after you stomp the gas(93 and 97 V-TEC). With taller bottom gears and top end it would only get quicker IME. Also replacing the trans won't make it non VTEC anymore. Its still going to have its variable lift timing but its got a better transmission now.

The larger 5th gear is not worth it. It won't be totally cheap because either you'll have to order it or rip it from another trans and then they are going to charge you because its useless now.

[MadisonMPG]

For right about 650 you can get a good 15-20 more mpg out of that car. Which will pay for itself in a few...years?

[Shortie771]

Originally Posted by MadisonMPG

For right about 650 you can get a good 15-20 more mpg out of that car. Which will pay for itself in a few...years?

15-20mpg from swapping my trans? i dont think it will help that much, i was thinking it would give me about 3 more mpg maybe... lol but idk. BTW my friend who is the machanic doesnt think that swapping the 5th gear or even swapping the transmition is a good idea. He says it isnt worth it but since he himself has never done that for one of his cars he is unsure of the advantages/disadvantages it would have and is willing to help me when i figure out what im going to do.

[theunchosen]

a Taller fifth gear can do an enormous amount for your mpg.

If your Del Sol is stock then you're doing a good bit over 3K rpm in 5th just to stay the speed limit on the highway/interstate and any higher speed backroads.

All reciprocating engines are much much less fuel efficient at higher rpm. The problem is everything has to happen much faster. . .and it doesn't. Just because you can make the engine run at 7K rpm doesn't mean the dynamics of the event are going off right. The shorter your expansion stroke(overall time) the less time for the gas to absorb heat and expand, this is why Torque graphs usually peak out before HP
(and its usually about 2K rpm lower Del Sol I believe max ft-lbs is 4100 rpm and horsepower is I think 6300 rpm).

Engines do have a power band that they are strongest through. . .but they are not fuel efficient in that region for reasons mentioned.

Swapping your trans to a 5th gear that lets you do 65 at 2.5Krpm or less, filling your tires to 38-41(wherever your max sidewall is) PSI, dumping any extra weight and not running your AC will definitely get you to at least 35(assuming your exhaust system doesn't have a leak somewhere).

I get 35 with shorter gearing than stock, and if I had a taller gear I could stay below 3K rpm on the highway(3K is about the breaking point for FE on the Del SOl, lower and its really good, higher and it starts disappearing fast).

[hamsterpower]

I see a few choices for you. fix any other problems (o2 sensor...) and add a manifold pressure gauge for better feedback to technique. In my opinion this would be the best choice because it would save some gas and all of the fun factor of the car.
Next there is the full transmission swap from the integra LS (S80). This is the easiest and possibly the cheapest choice but I do not recommend it. I have this set up on my b16 powered civic and yes my mileage is better, yes the swap was done in one day, and yes I found the donor on ebay for $200. BUT, the fun is nearly gone, it drives just like it did with the original DX engine/transmission. And I still only average 30ish MPG. This is not a better transmission it just has different ratios. When I fix the bearing in the old transmission it is going back in. (sorry ecomodders)
If you have the budget the best balance of fun to eco may be a Integra GSR (Y80) transmission swap. This gives taller gears across the board but not as tall as the S80 set from the LS.
Finally the 5th/final gear swap into your S4C trans. This would be the most time consuming and expensive option unless you have free labor. but lots of people are happy with the results. It might be cheaper to just buy a disposable Kia to daily and keep the 'Sol for fun times. (no offense Kia owners)