My 1990 300zx Twin Turbo build by megaDan

7 minute(s) of a 731 minute read

This weekend was great. Sure the weather didn't cooperate and I had to leave early, but it was another enjoyable experience.

I found an AirB&B in St Charles near the shop we would be spending all weekend at, as I wanted off street parking for the Z (and Chicago hotel prices can be kind of nuts). I picked my buddy up around 7:30 at his place on Thursday night and we headed out. Unfortunately the forecast was for rain all evening. Driving the Z at night is just about my favorite driving condition, but night in the rain is a thoroughly unenjoyable experience. Thankfully a road trip with a good friend changes things. We made it to the Chicago area at a reasonable 10:30 and crashed for the night knowing we would have to be up somewhat early.

Much of the group was doing a tech day on Thursday to make sure everyone was ready for the stress test to come; I was unable to spare two vacation days for this event. The instructions were to meet at the shop between 8:15 and 8:30 on Friday to get everything situated so we could get the first car set up right when they opened at 9AM. Thanks to a stop at McDonalds, we were a bit late and showed up at 8:45. This is the same shop I was at 5 years ago for the same event, so I knew I was at the right place. We arrived to an empty parking lot...and started to worry. Was this the right day? Did they change the date again?? After a quick chat with the owner it sounded like everyone was running late so we just hung out. Phew. Given that it was warm and sunny and I'm a morning person; I could think of worse ways to kill time.

I wasn't really sure when I would be up, we had a very rough tentative schedule that put me at the end of the day Friday, allowing for time. I was somewhat nervous on the drive down, and I had to sit and wait nervously all day. Don't get me wrong, I was excited; but nervous something would go wrong or fail or whatnot.

First up was a 240SX with an SR20DET recently converted to Haltech. I believe most of us were there for E85 tunes, and this one was going full flex-fuel. Thanks to the new software, there were some issues with base timing correlating with what the ECU was seeing. As a result, he melted a couple sets of plugs before they were able to determine what the problem was. The car was pulled off the dyno to solve the issues in the parking log while the next car was prepped.

Second up was a heavily modified Z32; he had put down 650+ last year, but lifted he heads when trying to up the boost. He was back this year with all the weak points hopefully addressed. Unfortunately he was having laptop issues and couldn't get Haltech customer support to get back to him. Since I was the only other person ready to go; it was my turn. We drained the remaining 93oct from my system and put in 10 gallons of E85 that we got from the BP down the street. According to my backwoods ethanol content sensor, it was E75....not bad! Especially considering BP's disclaimer that their E85 won't get better than E83:

All told, my time on the dyno only took about 90 minutes. We spent about 15 minutes diagnosing a lean condition that ended up being a result of unfamiliarity with the injectors instead of a fuel pump issue (phew).

Once compensation was made the time went quickly (thank god, because I was a nervous wreck) and I was mostly pleased with the outcome. I expected more with the boost cranked, but ultimately it is what it is. More regarding this later. Graphs first: Red is E85, blue is 5 years ago on 93Oct. Look at the torque gain between 3-4k rpm!! For those without pictures: 477whp/473tq.

The only surprise came when we rolled the car off the dyno and found a puddle of what I hoped was water from the night before. When I realized it was coolant my heart sank. After a few minutes of poking around, someone kindly chastised me for using the Mishimoto radiator cap that came with my radiator and recommended I go with an OEM cap. The tabs on my cap were bent slightly, preventing the radiator from holding adequate pressure. I bent the tabs back in place, topped up the radiator, and haven't had an issue since.

It would be a while before I got to test drive as I was waiting for the car to cool down following the coolant situation. Meanwhile, another super clean Z32 showed up, and ended up being next on the list. He was running a stock motor with a 2.5" exhaust and upgraded intercoolers. He ended up making 362whp/345tq on 93 and 442whp/448tq on E85!! Super jealous, that is a very healthy motor.

I finally got to take a test drive when we ran out to grab lunch for everyone. The roads were all quite busy and low speed limit so I didn't get to really open it up; but I didn't need to in order to have fun. The increase in torque in the mid-range is unbelievable. From 3-5k it feels 50% stronger than it did before. With my 93 octane tune I needed to rev it out to really feel the pull. Now that happens as soon as the turbos start to spool. Driving enjoyment has increased a full 100%. It's hard to describe how much driveability has improved. With the somewhat chilly weather we've had, its difficult to tell if I've truly run out of traction. 2nd gear is a rolling burnout above 4k rpm at full throttle, and third gear is where the fun is at now. I have been wondering about the lifespan of these turbos being run at 23+ psi; so I took a test drive yesterday with my boost controller reconfigured to be ~17.5psi on the low setting. Thankfully this doesn't seem to have affected perceived power levels whatsoever. It is still a riot even with the 'low' boost levels. I'll continue to play with these settings as the weather warms up; but there is nothing but rain in the forecast for the next 5 days. Nothing like getting a new toy and not being able to play with it.

There were a handful of other cars that got on during the course of the day; and it ended up being a lot of fun BS'ing about our cars and working together to solve the mostly minor issues that cropped up. Unfortunately as they day progressed, so did the forecast for Saturday. The weather went from unpleasant, to full on winter storm warning starting at 10am. I realized that if we didn't go home Friday night/early Saturday, we would have to stay until Sunday which wasn't in the cards. They were projecting 6-8 inches in our area with snow around 1" per hour. If it was a light dusting, I felt okay about taking my chances; but even with warm ground an inch per hour is going to accumulate quickly. We ended up making the decision to leave first thing Saturday morning. It was a tough decision to make as the group of guys was really cool, and I was looking forward to seeing who showed up on day 2.

All in all it a great experience. We met some really cool people and made the Z much more enjoyable to drive. Hopefully this puts the itch to bed for good. Thanks for reading!