Turbo Works 1

The coupe is underway and… It’s October! And… being more experienced now, than I was three years ago, I can look at our long list of things to do, and realize that even though we have five months to get everything together, it’ll be awfully tight. Already I’m thinking about cutting down the work load by delaying a couple things until next year. We’ll see how it goes.

Last Sunday Ryan and I got together to pull the large port out of the coupe, and further discuss our options as far as powertrain goes. The final conclusion was turbocharger. We both concluded that NA tune simply wasn’t feasible for our power demands. Our SC motor, a zenkei unit rated at 145hp would also take a bit of extra investment to hit our numbers, and even then results have been questionable. Furthermore, various aspects of the SC motor have always been quite unappealing to me personally. First, it’s horribly unappealing aesthetically with that sick looking intake manifold that also happens to be very inefficient. The second is the general nature of superchargers… engine driven compressors seem quite archaic, and the Toyota SC12 is a particularly inefficient example. To reach our power goal, we probably would have ended up supercharging the stock 9.4:1 block, modifying the large port manifold and SC brackets to make the two fit together, and then plumbing it all together. Boosting only 7psi at that point, we’d probably need a pulley to get boost to around 9-10psi. Hopefully then we’d find 160+whp, but the success of others who have tried similar things has been questionable, and then… 10psi on the early block is even more so.

The turbo on the other hand, has proven again and again to make lots of power. As far as tuning MS, there are many good examples out there. A manifold, and turbocharger plus all the plumbing makes it a bit of a greater expense and mechanical effort than even a custom SC Intake Manifold, but in the end with much greater power and upgradeability. We’re so confident in this that we’ve raised our output hopes to 180whp. The downside of the turbo… lag… whether it will be an issue we don’t know: neither of us have much turbo driving experience.

So where are we right now? Cars 8 and 9 are gone which means most of our assets have been turned into cash and we’re ready to start buying. Our lightweight 20v flywheel showed up, along with some new Cusco motor and mission mounts. We’ve ordered a 3 puck clutch from Illegal Garage, but we’re still shopping for the rest.
– a turbocharger (more below)
– a manifold (I have other things to think about besides making one)
– an intercooler (GZE intercooler is an awkward front mount)
– MS… (just have to get off my ass)
– fuel pump
– brake bias adjuster

That’s the short list at least. Our next step is separating the GZE block from it’s tranny, and assembling the long block for turbocharging. We’re planning on using a large port head and cams, as well as retain the distributor. This will probably end up eating up a lot more time and money than a glance indicates, so I think it’s important to get over with. I want to get a motor back in the car ASAP so that we can fit the manifold and turbocharger, and proceed with the fabrications related to that (downpipe, IC etc etc). But… before the motor goes back in, we need to patch up a couple things in the engine bay. We’ve got the typical cracks at the junction of the strut tower and frame rail, and I want to weld a brace in, as well as some other stitches etc. My original plan was to strip everything out of the engine bay, stitch weld extensively and then repaint. I don’t see time for this anymore, and we’ll probably just clean everything up as best we can, and have a few places welded. Also want to fit the brake bias adjuster and do something with the steering rack before hand…

Meanwhile we’re shopping for a turbocharger, as that will determine the next most significant pieces we need: manifold and downpipe. The original plan was to run a T25 turbo from an S13 or S14, but these have proven to be somewhat difficult to find in good condition (tonnes of dead ones around… maybe not a good sign). I picked the T25 because… not knowing anything else… I knew that most of the Japanese tuners used them. Further research has revealed a couple other options. The TD504 from Talons, and various IHI turbos found in Dodge, Subaru and Mazda products. The objective is to find the fastest spooling turbo that can meet our power needs. If upgrading power past our goal is going to require a whole different turbo down the road… so be it.

Currently in our possession is a pair of used FC turbos. I picked these up from a friend not knowing much about it. In comparison to the T25, it’s quite ENORMOUS! This entry is getting quite long… and I don’t have the energy to explain more of what I’m thinking… but check out some pics I snapped tonight. The big one is the FC IHI, while the puny thing beside it is the renowned Garret T25 from S13.