What I have:

2 spare Z6 heads
1 spare Z6 engine
Skunk2 intake
ebay header
2 P28 ecu's
1 DX trans, 1 EX trans, 1 SI trans

89 EF 4 door with mpfi / d16z6 swap - dx trans.

Build a P29 / cam / pnp NA and shoot for 12:1 & 160 whp?
Build a low boost 6-7 psi pnp / cam / pistons? - hp / milage?

DD - 80/20 freeway at 80mph

Can a trans be rebuilt with 1-4 SI gears and economy of DX or HF 5th gear?

Few grand is the budget but could go a bit more if I buy a turbo / intercooler setup.

 

If you're concerned with fuel economy as a top priority, I wouldn't go the turbo route. Go for a turbo if you're looking for a fun DD. Not to say you'll automatically get poor mileage, but under boost/power you'll always use more gas and a safe turbo setup usually runs on the richer side.

As far as transmissions.. The L3 trans has the same ratios between Si, LX, DX. The only difference is the final drive (being shorter in the Si). You could just swap a HF 5th gear into an LX/DX trans, but it wouldn't offer too much of a difference.

If you do decide to go the turbocharged route, I'd recommend using a Go-Autoworks kit. Greg has built a few nice boosted D-series and his kits are recommended over anything eBay. There are others available as well, but I would avoid eBay or anything Chinese. Pay once and do it right.

 

What are you talking about man, plenty of people have low-hp turbo builds that get great gas mileage. There's a reason why a lot of fuel efficient cars from the factory are turbocharged. They aren't simply taking more fuel for power, but are increasing the efficiency of your engine; thus, you can actually use less fuel and save gas by using less throttle than you would NA. Word is even builds in 4-500whp range can get pretty good gas mileage, obviously depending on your driving style.

 

Yes its possible to get even BETTER mpg with a turbo setup. It just depends on the tune and your right foot.

 

+1

I got some decent fuel economy on my S13. Was it better than non-boosted? Not really, but for the power it put down (385/360), I averaged 27mpg highway.

 

my 500 hp civic gets damn near 35 mpg. with a turbo motor u don't need all the fuel at low load like a high comp engine would want. also you might have longer gears or final drive combo to get higher traps in 4th since it makes more power than only on motor. just make sure u don't use a turbo that spools at real low rpm or with any slight blip of the throttle. once in boost thwts when u start chewing through fuel.

 

I got about the same boosted / non boosted stock for stock. All in the tune and the cams. My LS with big cams was about 5-10mpg less then my LSV is now.

 

If you able to keep your foot easy and stay outta boost once in a while you should be fine going to turbo route. Listen to everyone above lol

 

the vtec motors seem to get better mpg than nonvtec. be careful with a z6 that u don't go too low with static compression that you have to dip into the throttle just for mild acceleration around town that will hurt mpg

 

400whp LS/VTEC on E85 and I used to get up to 30mpg on the highway. Honda's natural lack of low-end torque is nicely complimented by turbocharging. It makes highway driving effortless because at 3600rpm, you're in or damn close to full boost with a "normal" sized turbo.