Got a spare engine for cheap for my van, so I figure I can go a little crazy on it. Mitsubishi 6G72 SOHC 12 valve, 3.0L V6. This one is a '92 with the roller cam, so hoping that's a slight MPG gain before I start.
Just in the preliminary stages of planning the atrocities I want to wreak on it so far.
Here's what I'd like to work in.
High compression, with Singh grooves and "edging" to handle it.
"Velocity porting" for improved induction and exhaust (And it's about the only way to handle it on this, very little meat to play with) Deshrouding the exhaust valve might help too.
Concentrating charge/burn over exhaust valve. Shown to be effective in many concepts.
Piston mods to enhance tumble when piston low, and to enhance swirl at top of stroke. Also hope to work in a wedge shape to the piston to offset toward the exhaust valve.
Now the highest compression pistons available for 6G72s are 10:1 and it's a PITA to make sure that those are actually the ones you get. Very confusing info on the applications of those. I'm not sure those will be "enough" since by the time I've done any grooving, edging and deshrouding, the compression will probably be back down to 9:1, heads apparently have very little to skim to claw any back. I'm looking at the possibility of using pistons from the 2.6L 4G54 Mitsubishi Astron, which are the same bore and have the same pin diameter. The compression height on those is 35mm vs 31.8 for stock 6G72 pistons. I think that would work out at 14:1 if they don't pop out of the deck (Gotta find that out, and double check it on the engine when I've got the heads off) Now 14:1 is a bit too much in all likelihood, but I think that by the time I've carved at them a bit and taken a few CCs out of the head, that it all might work out nice and have me sitting at 12:1.
Trying to figure something out for the fuelling is giving me "conniptions" at the moment, dunno whether 88 should be 27 psi or 48 psi (conflicting info in the net) Can't use the injectors that came on the '92 'coz they're high impedance when my 'lectronics expect low impedance. Now I want to make provision for extra fuel, since I wanna make sure that nothing is toasted when the gas gets mashed. It's reputed that the SMEC can tune for up to 50% more and not lose MPG if you "keep your foot out of it" Also thinking that at lower engine speeds, normal driving, that getting all the fuel sprayed earlier in the induction cycle may have benefits for encouraging a stratified charge type of burn. Might turn back the fuel a bit later but want to be real careful at first.
I'm hoping that I can make a lot of power with these mods too, aiming to get 30% more flow out of the ports than anyone else is getting on these by using various tweaks to manage flow. Goals are 30 mpg (on 6 cyl) 225HP ...... and 14 second 1/4 miles. :twisted:
Other mods will include a crank scraper, intake plenum and throttle body porting, spacers and mods, ignition upgrades. Also trying to work out a "reliability" mod which is something like a windage arrangement for the camshaft, something like what's on K engines, (To solve PCV oiling and clogging problems on this one) which may give a fractional efficiency increase. Might try porting the headers, not sure yet, they appear to be doing something that's desireable for reasons of making 3 cylinder DOD work, and I don't want to mess that up.
Van will also (eventually) get an aerodynamics package, hmmm well maybe some of that will get on there before I finish with it's "new" engine.
Anyhoo, getting excited planning it, never seriously thought before about getting a spare engine at the $500+ the wreckers usually want around here, but I've got one now so can "go nuts" :D
Van will probably get emergency surgery shortly, and be on the road for a few months before this engine is near ready, and I may be testing some of the bolt-ons, some of the DOD stuff, some of the aerodynamics etc on it before it get's it's new motor.
So, that's the next thing in the works. Really need to get going on stuff though, Escort project is stalled still/again. I was celebrating winter's departure too soon the other week, had a couple of warm days, but this week it's been snowing a bit again, not hanging around though, and snow in the forecast for the next week too, grrrr. That makes 6 months of winter here, got our first snow early on October 13th, warmed up after until Jan but it was mostly that raining sideways blowing a gale weather I couldn't use either. Feeling like I've got screwed out of about 3 months of "doing stuff" weather with all that :roll: Figure as long as it's at least 7 or 8 C though I can tear into front end work on the van, whether it's raining or not, though I guess a couple of degrees above freezing is just as good if it will stay dry too, and at least get that in running shape, then pressure's off a bit and I might be able to concentrate better on the Escort and get that finished.