FastLaneTuning

Okay, guys. Here are some questions that I've been pondering over the last couple of weeks. I figure that since things are starting to take off for the USDM Lancer (tuning wise... CONGRATULATIONS ON THE SCC SPREAD ROCK AND BONI) I would post up some tech questions that I haven't seen answered yet.

First Question: The US Lancer redline's at 6K. Why? I've heard talk about connecting rods, but is that the only limiting factor? If not, what else are we dealing with that can't handle the stresses of high RPM's?

Second Question: This one's directed more at ROCK than anybody else (since RRM seems to be the MOST serious about tuning the US Lancer). What are your goals when increasing power in the Lancer? From what I know about RRM, you guys know your stuff when it comes to competition racing. Are you trying to get a lot of low end power while sticking to the 6000RPM redline, or are you trying to gain a lot of high end power (possibly by raising the rev limiter after doing mods)?

Third Question: Speaking simply of the overall engine design... Did Mitsubishi design the 4G94 to be a formidable race engine? I believe the current Evo uses a 4G63, but what is the purpose for our engine? The current Cavalier Ecotec engine (pardon my domestic powertrain example) was designed with the aftermarket in mind. Most of you don't read the domestic tuning magazines, but a friend of mine who's a mech. engineer gave me an article that showed how a stock Ecotec wouldn't even sweat after a 300hp buildup. What are the tuning LIMITS of our car? 200HP, 300HP, 350HP??? Did Mitsu simply "detune" our engine for gas mileage and city driving? Is there A LOT of hidden potential there without needing to rebuild internals?

Fourth Question: WHY IS OUR RADIATOR SO HUGE???? Is it a hand-me-down from a high comp. forced induction Mitsu??? I mean, the radiator on my 4.0L Northstar V8 Aurora was about that size!

Just some stuff I've been thinking about. Any input would be much appreciated.

pjal84

Well, yes, the low redline is partially due to the con rods being to long. The stroke is really long but this gives us our torque advantage over other small displacement imports. However, because of the long stroke, that makes for a slightly weaker rod. All about the give and take I suppose. Plus, cam timing also has a lot to do with it. A single came engine won't be able to effectively rev to the stratosphere because it only has one cam to control the intake/exhaust timing of the valves. I 'll leave the second question to Rob, the third I'll take a shot at. I highly doubt the 4G94 was designed to be a "competition" engine considering it's based on the older 4G9X engines (w00t to our Mirage guys). It seems that the 4G6X engine such as though found in the higer up Colt/Mirage turbos, the Evo, and the Eclipse seem to have more performance in mind (albeit I think the Eclipse is 2.4L). Any engine can probably be comp spec but it just require copious amounts of cash. The boost limit for the 4G94 seems to be around 9-10 psi before you have to start getting new internals. However, as the turbo guys have learned, the 4G94 does seem to enjoy takin' boost so that's definitely a good sign for future tuning. As for the radiator size, you got me. Might just be a Mitsu thing.

bahamut

pjal84 is absolutely correct.

The 4g9x engine series came into existant from the 4g92 MIVEC (using similar Caddy valvetrain tech before full blown ultra conservative, untunable MIVEC-MD) to the 4g93T (baby evo w/o the price tag). Then, it died in 00 w/ the FTO in favor of GDI cyl head and engine management.

Basically, the 4g9x block is Mitsu pushing tech stuff w/ economy and performance in mind, except the US spec car (on the very conservative side of the equation).

dude in a mirage

Sorry to dig up old topics as I haven't been here in awhile:

What I believe should be done is to drop a 4G93 crank into a 4G94 block. That would give 1857cc displacement (vs the 4G93's 1834cc and the 4G94's 1997cc) but the extra long rods from the taller deck height of a 4G94 would give a better rod ratio than the 4G93...you'd be able to safely rev up to 7000rpm without too much fear of spinning rod bearings (the 4G93 has a 6500rpm redline and 6800 fuel cutoff). Since your block starts at 81.5mm vs the 4G93 81mm you should be able to bore it out to 82mm with OEM oversize pistons and no reliability issues (mitsu makes the engine in a fashion that allows up to .5mm oversize pistons with no problems). This would give you a displacement of 1880cc and a higher revving capacity then the 4G93 and the 4G94. With a good cam this would allow it to outperform either engine (the higher revving makes up for the slight loss of displacement).

The greater mass from a SOHC valvetrain (long rocker arms) does limit the rpms somewhat but 7000 is well within reason.

pjal84

By all means DIM resurrect that post...quite the technical insight you have. By all means grace us with such high quality info.

bahamut

DIM, I thought the max bore was 81.5 out of the 4g9x block. I've glanced at Felix's block and can't imagine boring that thing as 82mm w/o weakening the cyl wall.

dude in a mirage

4G93 is 81mm and can be bored to 81.5mm which is the limits by mitsubishi (82.5mm with O-ringing of the block according to mitsiman).

Since the 4G94 starts at 81.5mm and almost all car manufacturers (including mitsu) create engines so that they can be bored out for repair purposes it stands to reason that the service manual will probably show 82mm as the max overbore size...(they should actually list 81.75mm as the first oversize and then 82mm as the second oversize).

Now one problem that I see is the reduced stroke means less compression but that would be good for turbo use or you could put in the 1.8L .5mm oversize pistons (81.5mm pistons) and that would probably get the compression back up to stock...maybe use the 4G93 overseas .5mm oversize pistons and get a compression ratio that is a good 10.0:1 or so...

AdamJ39

iTrader: (51)

bringing this post back from the dead...what DIM is saying sounds realistic...as long as all pistons all lined up with the top of the head everything should work out correct...i could be the first one to do this also (i've still got me G93 Block and Head in the yard)... but anyway in order for this to work wouldnt we need to have G93 Cams, or would we need a custom...also if we could use the G93 cams and crank that means that we would have to use the G93 Ecu as well...i wonder what sort of gain or loss would be assosiated with a swap like this...assuming that it would even work...i see not to many people saw to investigate this topic as the post has fallen away...anyone else have any comments?

-Adam

AdamJ39

iTrader: (51)

damn i didnt realize this post was allmost 2 years old...