'95 Del Sol, need some advice!

[Ecky]

Hi all!

I have a '95 Del Sol VTEC trim, currently running a B18A1 motor mated to the stock B16's very short Y21 transmission. I'm getting 30mpg +/- 2 per tank, and it doesn't seem to vary as much as I would expect when I'm driving primarily in the city vs the highway.

I'm running the stock B18B1 computer with OBD1 wiring. The closed loop mix seems to be moderately rich, but it runs very lean once warmed up. Strangely, I don't seem to get *much* of a mileage difference when running on only closed loop fuel mappings, but I don't have any gauges yet, which leads me to my first question:

What gauge do you guys recommend? MPGuino? I know exactly zero about these gauges, so please help me get started!

I'm thinking swapping the transmission out for one with longer gears (LS tranny, GSR tranny?) would be helpful. At 75mph I'm running around 3800rpm with very low engine load. How hard would it be to swap out the 5th gear only in my tranny? I've never done any transmission work.

I've also been thinking of swapping the cams out with B18B cams. I've read that they have higher lift, but also that the intake cam is advanced 5 degrees over the B18A1 cams. Anyone have experience with advancing cam timing on B-series motors? Any suggestions on cams?

I'm running 195/60R14 tires right now, at 32psi. What pressure should I be running? When it comes time to swap tires, what would be an ideal replacement? My speedometer is currently off a few mph (high) so I'm thinking taller, skinnier tires would both fix my gauge issue and reduce rolling resistance.

I have coilovers and I'm currently riding at about stock height. Will dropping the car an inch or two significantly reduce my Cd?


Thanks all! Will post more questions if I think of them.


Some pics:






Under the rear bumper:


Terribly un-aerodynamic front end:

[payne171]

Well, I know there are a lot of people more knowledgeable on here than I am, but here are a few things I can tell you:

First, and I'm just throwing this out there, but if you're game for swapping major drivetrain components out, can you find one of the lean burn honda engine/transmission combos? 1992–95 Civic VX 1996–2000 Civic Hx 2001-05 Civic Hx. You can't do much better and especially the 92-95 ought to be really simple.

I have heard good things about MPGuino and there are more than a few scanguage users, but I have no firsthand experience with either. Once you get one, you will know why closed loop is so close. I would guess open loop might be pulling some timing, but guess is the key word there.

I wouldn't open the transmission. There is a reason good mechanics often farm out tranny work to other shops. It is way easier to get a taller geared trans. Avoid the higher lift cams. You are driving a Honda b-series. If you want more cam advance, every japanese tuner company under the sun makes an adjustable cam gear for it. Easier to do as well, I hear.

You are probably not running enough tire pressure. On my Insight I am running 50 psi, but the Insight is a different animal. Most ecomodders are at least at max sidewall pressure, and many are well over. Be forewarned, it does have consequences on ride and handling. When it is time for a new set of tires, it is worth looking into tires built for fuel economy. You are right on with skinnier tires,although again with handling consequences.

Lowering will definitely help with aero, or you could fab some underbody trays to do the same. You might be able to fab some aero to smooth the air path from the roof to the trunklid. If I remember the shape of the Del Sol, that can't be a good aero shape.

[Ecky]

I have some pictures in my garage, take a look.

Reading some threads here, I was under the impression that a gear swap can be relatively easy on *some* transmissions. Not so with a Honda?

I believe the max pressure printed on the tire is 36psi, would that be the max sidewall pressure? I was told by a mechanic that increasing tire pressure past a certain point would cause it to wear more quickly, what's the truth behind this?

I'd love to swap a 3 stage or I-VTEC engine in, but money is really tight right now. The LS motor is fairly lean-burning anyway. I can probably make a little by trading my Y21 for an LS tranny though, since this is the shortest B series transmission available and is relatively hard to find in good condition.

I was already thinking about some under-trays, the rear bumper looks like an aerodynamic nightmare, but I haven't made any decisions yet. I think it would be really cool to make the Del Sol into a hatch by putting a contoured piece of glass over the trunk, kinda like on an Integra.

I'll post some pics once I'm up to 5 posts.

[some_other_dave]

You have an LS motor, so the LS transmission would be a natural match to it. Should be a relatively easy swap, too.

I've opened up my old D-series transmission, and it was of medium difficulty. I'm not sure how tough the B-series ones are to do. Some of the measurements may be tricky, if my reading of how to work on transmissions from other cars is correct--and that might be the case in any gear swap.

Chances are pretty good that at least some of the shortness of the gearing of your current trans is from the "final drive", the ring and pinion ratio. So swapping the 5th gear for a taller one will only get you some of the way to lower revs at freeway speeds. That's another point for just swapping in the LS trans.

Taller tires would also help you run at lower RPM (and slightly higher load), which would be good for fuel economy. But the speedometer and odometer are only based on how fast the ring gear turns, so they don't "know" anything about the wheel and tire size. So your speedometer would still read 75 MPH at 3800 RPM, even though your actual speed would be higher.

We usually tell people to go up to the max pressure that is listed on their tires. Some go higher, very few people who are serious about fuel economy go lower.

75 MPH is really bad for economy. If you slow down to 65, you'll see results. Drop it to 55, and you'll see even better results.


The ScanGauge only works on OBD-2 cars. The MPGuino is pretty much your only choice. You'll have to figure out the correct wires to tap into.

-soD

[Ecky]

I typically cruise at ~65, sometimes I have to be somewhere quick though. ^^


Tall tires might be a good idea as my speedometer reads too high. I have a new cluster on the way so that might fix it, but if not, maybe I'll switch to 65 or 75's? When it's reading 75mph, I'm doing closer to 70mph.

[Ecky]

Added some pics to the first post.

Anyhow my biggest thing right now is getting a gauge working, like MPGuino, but I don't even know where to begin. If I buy a pre-assembled or kit from the MPGuino section here, is it guaranteed to work in my OBD1 Honda? Are there any differences in kits, or is it 1 size fits all?

Also, I'm thinking of replacing some of my lights with LEDs to reduce alternator load, are there

EDIT: Just occurred to me, my mileage isn't significantly different with the top on and windows up, or with it off. I'm guessing this is because I'm losing a relatively much larger amount of efficiency somewhere else, like with the gearing or maybe the underbody.

EDIT2: Just finished reading on the cams, my A1 is of 92-93 spec so it has the same mechanical cam timing as the B1, so scratch that idea.

[Piwoslaw]

Have you seen jedi_sol's threads on his Del Sol mods? He got some pretty good MPG numbers.
Del Sol, Underbelly Pan
Project Del Sol Kammback Dead; New Ideas

[Ecky]

I just finished reading those two. I think the first items on my list are to play with tire pressure, and to fill in some of the gaps around the wheel wells and under the bumpers. I'm guessing that'll see the largest improvement short of a boat tail or tranny swap.

I'm a little wary of over-inflating though, as I blew the sides out of one of my rear wheels a few weeks back, drifting around an on-ramp.

[some_other_dave]

MPGuino is one-size-fits-all. The trick is that you have to find the appropriate signal wires to tap into. One of them is the VSS signal, the other being the injector signal.

-soD

[Ecky]

I was reading on spoilers (as a cosmetically better choice than a boat tail - gf would kill me), would a small spoiler do anything toward fixing the horrible aerodynamics of the back of my car? What shape is best?

This site has a pretty broad selection, I'd get a shape in mind and hit some junkyards, I think:

Honda Del Sol Spoilers

EDIT: Here is an aftermarket spoiler that looks to attach to the trailing edge of the roof and direct airflow downward. Thoughts?

http://www.speedzonemotorsports.com/...productid=4885