Looking for some input/help on an idea i have to put together a high mpg highway car. So far i have a 98 civic hx longblock and a 94 vx trans. Trying not to use the expensive 5 wire wideband that the hx comes with since i don't have one. Here is what i'm thinking.

-98 HX longblock
- y8 intake manifold/TB
- unsure of which wiring harness to use (don't think i need a y5 harness)
- 4-2-1 header to stock exhaust
- unsure on which ecu to use (possibly chipped p06, p28) ((want the car to be tuned for mpg))
- rdx injectors (heard they atomize fuel spray better)

Please help me figure this all out, I'm wanting to put this setup in a 96+ civic

 

You wohld be better with a D15B (the 3 stage vtec one) and a ttiiiinnnyyyy turbo.

 

Totally agree with F22. Or you can use a D15B6 (HF CRX motor). The ECU should match depending on the motor, but will have to be OBD1 since you should definitely go with a tiny turbo.

After that, you'll want to lower the car as much as you can. 13" rims with solid hub caps. An air dam for the radiator and possibly a radiator block (partial) if you aren't having issues with cooling. Side mirror deletes will help too. You can take some aero designs from the Insight and block off the rear wheels flush with the side skirts/rear bumper.

A vacuum gauges and possible TPS monitoring will help you improve your driving style for maximum fuel economy. You could go with an ULTRA gauge or something similar if you end up with an OBD2 vehicle. Neptune RTP has tunerview which would be something similar for a chipped OBD1 ECU. But the basic monitoring can be done with aftermarket gauges quite easily.

 

I already have the HX longblock and the VX trans so that's what i will be using.

 

Since you are stuck on that as your powerplant, you can give a tiny turbo a shot and see how that works out, but you very well could lose MPGs. I don't think that going with the 4-2-1 headers in a N/A setup are going to help, but I have nothing to back that up.

I don't know what harness will work for you, but find a harness that works/make your own/buy a pre-made one and hook it all up. Get a tune on whatever flavor of hardware your heart so desires and see what happens. You will probably get the best results on something nicer like an S300 or Neptune, but that is just more money put into the project in attempt to save money.

Beyond all of the things that Freemananana said, there really isn't much else to try. You could try a weight reduction, but I wouldn't get extreme into that like removing body structures like the bumpers (not the covers) and door beams, well, because safety.

Overall, how much money are you willing to spend to save some in gas? How long is it going to take you to recuperate that cost, if you do at all? Just a couple things to think about.

- Frizzy

 

Ultimate high MPG car?

Sell the Civic. Buy a 1st gen Insight.

You'll end up with significantly higher MPG for far less effort (and probably cost). Highway mileage is most affected by aerodynamics, and you just aren't going to beat the Insight there, especially with the super skinny tires it is intended to make use of.

 

I'm sorry, but was the term "ultimate high MPG" ever actually defined?

 

Ever heard of diesel?

 

I can't find it but there's already a thread about this full of information in the EMS / Tuning forum. In any event you are wasting your time without having the lean burn. That is the whole purpose of having the 5 wire O2 setup with the ECU that can benefit from it. Cheaping out won't get you extremely far. You would have been MUCH better off starting with a CRX HF. With the right aero done, tuning, and proper driving 100 - 120 mpg is achievable.

You really are in the wrong forum for this. And just what kind of gas mileage are you trying to achieve.

 

you shall go and visit ecomodder forum bro. people been HIPERMILING there for ages now and you probably will find that what you doing been done before.

d15z1 already gets around 50-60 mpg with its leanburn why reinvent the wheel with these Frankenstein engines. u should spend 2-3 weeks plowing through the internet and see who done what and what the result was before spending money and then having your hopes crushed when it doesn't work out as you imagined