Picking up where we left off....
Oct '01: Experimentation revealed that I am at the limit of the stock Mitsubishi turbo. To verify this, I unplugged the wastegate actuator line; I still only see a high of 17 pounds of boost... which drops to about 15.5 psi by 5500 RPM. (This tiny turbine is choking my poor engine.) I even tried to cheat and shim the wastegate, but no such luck. That's all there is. So while I debate a turbo upgrade, I decided to experiment with lowering my minivan instead.
Dec '01: Decided it was time to do something about the horrible stock Mitsubishi turbo, so I dug up a crusty old TurboII Garrett off a Daytona and had it rebuilt. This was to be my 'in-between' turbo until I have a hybrid made. But when I went to install it, I learned this Garrett has the small size flange which wouldn't bolt up to my large flange exhaust pipe. Doh! Oh, well, guess I was gonna do that custom 3" downspout conversion sooner than expected.
Jan '02: While I was waiting for the mailman to drop off the pieces for the downspout conversion, opportunity knocked on my door: a "Super60" head came up for sale. That's what I'd like to have when I upgrade to the hybrid turbo, and the price was right, so I guess I better jump on it now! I sent off my money and was going to forget about it, but then it hit me: the head is off the van now anyway, so I might as well install the race head right away. Well, gee, if I go with a ported head and a bigger turbo it'd be a shame to choke them both with a stock exhaust manifold, right? So I mailed off an extra one to be ported. So much for a mere turbo upgrade!
Feb '02: I managed to install the new head, ported manifold and larger turbo. Drove it for a week or two very gently, making sure all was well. Then hooked up the wastegate actuator in preparation of making some good boost... only to spin a rod bearing while cruising down the highway at 65 MPH. (sigh)
Mar '02: I took the head assembly right back off, then pulled the rest of the engine and tore it down. The block survived but needed to be bored, so I ordered slightly oversize stock (cast) replacement pistons and one replacement connecting rod. The crankshaft was thrashed so I found another and had it ground and polished. This unplanned rebuild has drained the money I wanted to spend on a limited slip differential conversion. Oh, well.
Apr '02: All the machine work has been completed and the fresh engine was reinstalled in the van. Just when I thought everything was perfect, disaster struck: there is now some kind of problem and the van will not run properly (or even idle on its own). I kept checking various wiring possibilities, swapping sensors, pulling at strings, and the like but nothing works--the damn thing will not idle above 400 RPM nor will it rev above 600 RPM even at half throttle.
5-22-02: I've spent some time here and there, but all to no avail: I still have no idea what is wrong. My wonderful brand new engine has only three minutes run time on it, so the piston rings aren't even broken in yet. I'm getting quite frustrated.
6-5-02: I thought maybe--maybe--the stiff new rings were contributing to the low idle, so I fired the engine and ran it for 20 minutes at nearly WOT. The boost gauge read zero all the while and the cyberdyne air/fuel gauge was bobbing up and down happily, but it would not rev past 700 RPM. The rings did seem to seat, though, and I was happy about that. What gives? After trying some new theories and deciding not to believe what my sprockets and timing belt were telling me, I tested for true top dead center. Turns out my distributor was about 40 degrees retarded! After reassembling everything and dialing in a healthy amount of spark advance, the thing fired and jumped right to 1400 RPM, then settled into its usual 1200 RPM cold idle. Wow! I took it for a few victory laps around the parking lot--everything is great. Now I'm going to perform a tranny service ASAP, then I'll start racking up the break-in miles. After 500-600 are on the clock, I'll start leaning on it. Woo-hoo!
6-6-02: Tonight I performed the trans service and found something ominous: bits of clutch material in the pan. Hmmm. Oh, well, I'll worry about that later. So after work I started driving it. Already I've found it very difficult to resist the urge to go into boost; I'm up to about 60 miles so far.
Jul '02: I waited until the engine had almost 800 miles on it and then hit the track (on June 28th). Despite running only 12 pounds of boost, I managed a 15.81 @ 86.68 MPH on a 2.376 60-ft time. I can feel the engine kinda buck and sputter while at WOT for more than a couple seconds; it seems I have to re-learn my entire fuel curve now. I want to get that sorted out before going nuts so I'm still only running 12 psi. Now I'm wishing I installed an EGT gauge when I had the engine apart. In non-performance news, I completely removed my suspension alterations! Back up to stock height with new Gabriel el-cheapo gas-charged struts and it feels great.
Sep '02: With a few more miles on the odo I gradually began to up the boost. With 18 psi I managed to set a new record: 15.40 @ 88.21 MPH. I wanted more, so I raised the boost... and suddenly my fuel curve went way rich and I slowed down considerably. Dropped the boost back to about 19 psi and leaned it out as much as I could; this generated my best-ever pass of 15.13 @ 88.64 MPH on a record 2.262 60-ft time. That same day I laid down three passes at over 90 MPH, which is also a first for this van. Once I get my fuel issues sorted out things ought to be great; too bad my local track is now closed for the winter.
Modified: 2-19-08.