ICEngineering Subjects

Monday, March 14, 2016

SM RX-8: Not STX Anymore!

Because I can't leave well enough alone, I'm taking my very well-sorted, cheap-to-operate, reliable, streetable, and competitive STX RX-8 and turning it into an expensive ticking time bomb that I'll probably never win anything in. I'm moving to the Street Modified class, aka SM, aka Spend Money, aka $M.

For those who like to read, the ruleset for that class is here. For those that don't, here's the rundown of what I'm doing:

1. Add power. In my case, I'm turbocharging the RENESIS. Yes, that's an ultimately futile endeavor.
2. Squeeze on as much tire as I can fit. And then add a little bit more.
3. Add silly huge aero because even the fastest autocross cars are still slow.
4. Make small upgrades to the suspension. Really, my suspension is already quite good.
5. Add lightness. I'm allowed to be as little as 2700 lbs without driver.

Doesn't sound like much when I put it in a list like that. We'll see how that goes.

Let's start with #1. Everybody who is trying hard in SM is making at least 400 whp. I can't do that with a RENESIS and make it through more than one event. Luckily, there are a lot of precedents for very successful rotary engines in SSM (two-seater version of SM), so I know it can be done with a 13B-REW from a third-generation RX-7. However, I don't want to deal with an expensive engine program right now so I decided to pick up a cheap GReddy turbo kit and shoot for ~300 whp just to get myself pointed in the right direction. The goal is to blow it up at some point which will force me to build a good engine. In the meantime, I can get the chassis and aero tuned without breaking drivetrain parts.

Sure, I guess that's what a turbo kit looks like
I got a kit with an upgraded turbo by BNR Supercars that has upgraded compressor and turbine wheels and a watercooled CHRA. Still a tiny turbo though because it has to fit in the space where there used to just be an exhaust manifold. I got a good deal on the setup because the manifold was cracked, which is a pretty common problem on these kits due to...shitty engineering? I don't really know. Easy enough to fix though. Other than that, this kit had a BOV added and a couple other mods made that supposedly improve how the turbo functions.

Step 1: Remove engine

Step 2: Add turbo

The only real change that I made to the kit is that I added an oil take-off to the oil filter stand. The kit uses a T-fitting off of the oil pressure sender on the side of the engine, but it's pretty clunky looking. A popular alternative is an oil filter sandwich plate, but most of those take unfiltered oil and also cost money so instead I just added some material and tapped it for an AN fitting.

Step 3: Impulse buy an S2 ('09-'12) transmission. They're supposedly a bit stronger
The biggest benefit is that it's cleaner
Step 4: While I'm in there, I should clean and powdercoat the subframe, right?

Step 5: Installation is the reverse of removal. Check for leaks.

With the entire induction system changed, the mass airflow (MAF) sensor doesn't know what to think about the air coming in anymore so I spent a few hours driving around, logging data and getting my real-life airflow to match what the computer thinks it should be. Now that it functions predictably, I'm going to strap it to a dyno in April and turn up the boost. Stay tuned. There's a lot of other stuff happening here too.