Monthly Archives: April 2008

Current Updates

It’s been a long long time since I updated this page. I apologize :-) As is the case, life takes precedence every once in a while and those issues end up being more important than updating a website about a car, no matter how cool the car is. So, until I’m independently wealthy, I have to fit in updating the site when I’m not doing normal things required for life, or working the the car that this site is all about.

Speaking of the site, I have a lot of things swirling around in my head about what I want to do with it – I want to redesign it soon, but I don’t quite have it set in my head, and I don’t have the time to redesign it yet, so it will probably be like this for a bit longer. It hasn’t hurt yet…


You probably want to know what’s happening on the *car*, don’t you? Okay, I’ll get to that. Over the past four or five months, I’ve been doing a lot of random work on the car. There are hundreds of tiny projects, from making brackets to getting the rear tinwork finished up. And this is all I’ve been spending time on.

This series of events is in no particular order:

GT4202 covered in oil.

A lot of oil on the GT4202’s turbine wheel.

I took the turbo off the car to find out that the turbo’s sleeve bearings were leaking oil into the turbine housing (and the compressor housing – more on that later…) and that caused the car to burn quite a bit of oil. There are three things playing into this happening:

  • Oil Pressure
  • Oil Weight
  • Oil Drain

The oil pressure on the car is extremely high when the motor is cold. And by “high”, I mean around 85 psi. When I rev it, it shoots up to 90psi and higher. Why is it so high? (“Why wouldn’t he just port the oil filter housing?”)

My oil filter housing [i]is[/i] ported. It’s hogged out. The thing can’t get much larger than it is and still allow the relief valve to stay where it’s supposed to be without falling out.

I’m running 20w50 racing oil in the car. Racing is in the name, so it has to be good, right? No. That’s not why I’m running it. I’m running it because people have issues with 4g63’s and bearings getting beat up at high RPM with normal weight oil. Thicker oil seems to help with these issues. This doesn’t even begin to explain some other issues people have with oil pumps and stuff like that, but that’s for another post…

In addition to that, this engine has a natural tendency to want to run higher pressure. While that sounds naive, it’s not. The balance shafts have been removed, and the rod bearings are on the tight side of their specs. So, this means the oil pumping to the balance shaft passages isn’t being used, leading to higher oil pressure. It also means the oil coming out of the rod bearings has more restriction, even though it’s marginal (we’re talking a couple hundred thousandths) – and general engine freshness all lead to having naturally higher oil pressure. Even with a ported relief valve.

So, there are reasons that my oil pressure is high. Why would that affect my turbo? Well, I am running my oil feed right off the oil filter housing. This means that the turbo gets full oil pressure, instead of the restricted pressure that it would get if I fed the turbo through the head.

[b]So, really what I’m trying to say is[/b]: the turbo was normally getting between 85 and 90 psi of oil pressure, since the engine is normally on the cold side of things when it’s running, right now, when I’m playing with tuning and stuff like that in my garage. This leads to a lot of oil in my exhaust, all over my turbine and downpipe, and even a little bit in my intake manifold. Used burnt oil is gross.

Okay, back on track. Because of all this, I decided to find an oil pressure restrictor to put on the turbo oil feed line. After talking to Robert at Forced Performance, I decided to use an AN fitting I had laying around, and thought I would test some theoretical orifice sizing requirements. In order to do that, I’d have to have a way to independently measure the oil pressure to the turbo separate from the rest of the oiling system. This was accomplished by putting a gauge after the restrictor, inline with the turbo feed line. The result is another new gauge in the passenger wheel well, where I can see the turbo’s oil pressure at all times. Handy. So, onto testing. Here’s part of an email I sent to a friend:

I basically took an 1/8″ npt to 4an fitting, soldered it shut, and then drilled holes of various sizes in it. rinse and repeat. I started out with a ~.093 (3/32″ drill bit) orifice – and that resulted in about 5psi pressure drop around 80psi, but very little noticeable drop once the car was up to operating temp – full pressure was like 28psi. Then I went down to ~.078″ (5/64″ drill bit) but that was just around a 10psi pressure drop at 80psi, and about a 2psi pressure drop @28psi. Then, I dropped down to ~.0625″ (1/16″ bit) and now the oil pressure is 60psi at the turbo when the oil pressure is 80 psi. At idle, the oil pressure is 25psi when full pressure is 28psi. Anyway, I’m sticking with this for now. I don’t have a smaller drill bit ;-p And, the only step that I can go down to is the FP filter’s .030″ hole. I’m not ready to drop that low.

turbo oil pressure gauge

My turbo has it’s own oil pressure gauge

So, there you go – This is with, as the email states, around 80psi of oil pressure. The car was around 150 degrees operating temperature at the time of testing.

In addition to the new turbo oil restrictor, I also replaced the -8AN oil drain fitting with a -10AN fitting, along with a new -10AN turbo drain line, and -10AN bung on the oilpan. That was an enormous pain in the ass, but you’ve got to do what you’ve got to do, right? If I had to do it all over, I would have started out with -10AN, and probably fed the turbo from the port on the head for the factory turbo oil feed line. It’s still a possibility for the future, but right now, It’s going to run how it’s set up. As my email suggests, I also purchased a turbo oil filter from Forced Performance, which has a nifty built in restrictor for ball bearing turbos. Since I’m not running a ball bearing turbo, I will have to drill it out to the restriction size I feel like I need to use. At this point, my turbo on my engine will probably use a .0625″ hole. It’s hard to find actual pressure information from anyone online, so I’m hoping this will help someone Googling for it :-)

Turbine Housing

Oh, yes, I forgot about the Turbine housing. After taking the car down to the shootout, the turbine housing started to get a little orange. [b]I am not a metallurgist[/b], but the GT42 housing appears to be a cast steel housing (it could be cast iron, but I don’t think it is – I think it’s steel) and the evening of the shootout, it rained. A lot. The car was outside on the trailer, so that led to a whole lot of exposure to generally humid conditions. All in all, the turbine housing has held up great. I’ve seen housings on race cars used for three months that are completely rusty, so the fact that this housing went three+ years sitting in a modestly controlled environment without much oranging at all is really quite nice. Even still, aside from me having personal issues with rust, it was time to get the housing coated so that it was protected and would also help with the underhood temps.

Ceramic coated GT4202 turbine housing

The GT4202’s turbine housing, coated with ceramic

So, after doing a bit of searching, I changed my mind and decided I wanted to go with someplace local – well, relatively local anyway. Kiggly suggested a place in Romulus Michigan called Exotic Coatings. And while I’m not so hot about their website, I’m very satisfied with their coating. They properly cleaned and media blasted my turbine housing, doing all the right prep work (they even understood what v-band flanges were ;-p) and then coated my turbine housing with a cast iron gray 2000 degree high temp coating. I’m very pleased with how the housing turned out, and they were even ahead of the schedule they gave me. they told me a week at least, but called me three days after I dropped it off and told me it was all set. Not only that, but their price was awesome – it cost me $75 to get the housing coated. Jet Hot’s gaudy iced-out blinging silver coating would be $180 on a T4 housing, and this T6 housing is larger than most cute T4 housings.

The turbine housing is now nice and pretty. I can also hold my hand about an inch away from it after running the car for a short period of time, and before the coating the housing would just radiate heat for a long time. This is a very unscientific method of testing it, but if I can feel that it’s cooler, then I know more heat is going through the header and *out* the turbine, not through it.

Switch Panel

Custom switch panel

A switch panel I fabbed up.

Back when I put together the wiring harness, I spent a lot of time thinking about where I was going to mount the switch panel. It was clear to me early on that I didn’t want to use an off-the-shelf switch panel, because they’re generally setup for circle track cars, or cars with a dash of some sort. Plus, I’ve never been happy with rollbar mounted switch panels from Painless or Moroso or any other place – they seemed too large and inelegant. So, because of that, I made my own switch panel from aluminum. I also decided then that I wanted to mount the panel out of the way, but easy to get to if I needed to. So, I mounted the panel next to the shifter mount, located on the driveshaft tunnel. This was really kind of a pain because of the shape of the driveshaft tunnel, but I’m very happy with how it turned out. these brackets are going to end up with a brushed finish, because I had to weld on them to do what I wanted to do with them – they mount directly to the driveshaft tunnel. The good news, though, is that the switch panel itself comes right out with the removal of four DZUS fasteners. Neat.

Fire Suppression

Safecraft fire suppression

Safecraft fire suppression bottle, installed and lines ran.

How can I forget about the fire suppression? I have a lot more pictures that I took, but I haven’t yet uploaded them to my server. Until then, you’ll have to check out the panorama that I digitally stitched together above.

The fire suppression system was a long time in the making. The system itself is a Safecraft RS system – it has three nozzles, and three discharge outlets on the bottle itself. I’m using two of them – one of the outlets runs to a line routed up through the interior of the car to my feet, as mandated by NHRA rules. The other outlet runs to a T fitting on the firewall, which splits that into two lines running running around the firewall. They go through a bulkhead on each side of the car, into the front fenders, and then into the engine bay. The bottle is mounted where a passenger seat would be, and is out of the way, for the most part. I could probably actually mount a seat there if I wanted to, but I wouldn’t be able to have passengers anyway ;-)

All in all, I’m pleased with how it all turned out. I will have to get those other pictures I’ve taken of the inner fenders uploaded soon.