My 86 coupe with 4+3 transmission is an Interstate cruiser. Personally, if you gave me a tuning choice between 280 HP and 28 MPG, I would take the 28MPG for my driving needs.
There is the question: What tuning and driving tips can you give me to maximize the MPG?
Thanks for your advice.

 

frequent tune-ups. synthetic oil if applicable...a K&N filter...

 

I have the K & N filter in place with an open faceplate, so there is virtually no restriction on air entering the intake. I replaces the 'pleated' rubber connector from the Mass Air Flow to the intake, and I put an airfoil unit on the intake to smooth the airflow into the throttle.

I also switched to Amsoil synthetic 5w-30 oil and put Amsoil synthetic gear lube in the 4 speed and Amsoil synthetic in the automatic trans overdrive unit. Draining the differential proved difficult, so that won't get synthetic until the differential gets dismounted sometime.

I have used a set of Bosch Plus-4 plugs (they were Ok, but I didn't really notice big improvements), and recently switched to a set of Champions (Mark Salem did plug tests that showed that Champions had a longer spark time than others, leading to better, more thorough ignition of the gas mix).

Anybody have any experience with other plugs? Maybe Splitfires?[/b]

Here's a question: considering the reduced resistance in the air intake end of the system, should I disconnect the battery to reset the ECU and let it re-establish a throttle response and ignition timing curve for the new intake system? Speaking of resetting the ECU, there is a fuse for the ECU. Does anyone know whether removing the fuse will reset the ECU? Or must I actually remove the battery connection to make it official?

Anybody have any other ideas about tweaking the maximum MPG from it? Thanks,
LLL

 

hmmm..im not sure about the ECU reprogramming...some ECUs have to be actually reprogrammed, and will not learn a new curve thanks to more airflow on their own...hence a "chip"...you could certainly disconnect the battery and see if there is any difference. i put splitfires in my 12 second nonner, and i noticed no difference..i run champions in my V8, and NGK iridiums in my V6. are you sure that there isnt a plug on the rear diff case? youmay have to remove the cover to get the fluid out, but im honestly not sure of the setup of that case and cover.

 

I've read that the split fires are crap...I have no experience with them, just passing what I read. I don't have a source, I think I read it on another forum.

Take it FWIW.

Mac

 

I can attest to the "splitfires are crap" statement. I made a cool plug and wire tester that hopefully I'll have a patent on, once I get off my butt and draw it up and submit it. Anyway, Splitfires fire from the center, not from each prong. My invention, to come, proved it. Filing off the ground electrode to half way accross the center electrode makes a "ball" of fire! I was using a 40k Watt coil w/a Pertronix pointless system that threw pretty good juice. Enough to power my 72 Nova SS to 6 grand flawlessly. It worked good because of the ease of working in the proper timing curve. Loved that system. Just my $.02.

 

sounds like quite a system that you have there!

 

Can you tell us more about filing off the ground electrode? What plugs did you file? How did you do the filing? What gap did you use? Did you test an entire set of your re-worked plugs? How did you test them? Give us all the good details. Some of us may want to replicate your procedure. Thanks,
LLL

 

Its called sidegapping your spark plug, its been around for a very long time. If you dont know about this, you may also want to google "indexing sparkplugs" where you mark a sparkplug with a nonconductive mark, screw in the spark plug, see how its opening is faced, unscrewing, and putting in special spacers to turn its direction so the gap faces the center of the combustion chamber. Supposed to free up a few horses, and all it cost you was time.

 

I was told by a corvette repair guy with a lot of experience to just use the regular AC Delco plugs in your vette (not the spitfires). The engines were designed to use those plugs. those Bosh platinums tend to carbon up really easily in the c4's, so those arent worth it. And the AC Delcos are a lot cheaper too.

Make sure your tires have the correct pressure too.

Does anyone know if putting premium fuel in a '86 makes a difference in performance/MPG??