photogenic turbos
02-02-13, 03:26 PM
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Join Date: Dec 2012
Location: New Mexico
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Turbo System with Air to Air Intercooler
Here are a couple of pictures of the turbo system on my '94 SC300. It was installed over ten years and 60K miles ago. When initially installed with stock exhaust manifold gaskets the return pipe from the large air to air intercooler (mounted at the bottom in front of the radiator) was touching the caps on the spark plug leads on the distributor. This caused intermittent loss of power when the high voltage arced through the insulation to the pipe. The other problem that arose was that the exhaust manifold warped and stripped several of the manifold bolts out of the block. Two years ago I took matters into my own hands (after several shops failed to properly diagnose and fix the problem) and removed the turbo and exhaust manifold. I installed Helicoils in the block where the threads were stripped and had the manifold mating surface machined flat.
To move the turbo and inlet pipe further away from the distributor cap I used doubled graphite gaskets on both the manifold to block joint and also the manifold to turbo joint. I had to slightly enlarge one of the mounting holes on the turbo housing because of the change in geometry. Try hand filing 1/4" thick cast iron to remove about 1/8" of material! I also slightly flattened the strut tower adjacent to the turbo to make sure that when the engine moved slightly on it mounts that it wouldn't hit the sheetmetal. There is also a piece of white PVC pipe slit and placed over the pipe joint where it is close to the distributor cap as an electrical insulator. I also slit a piece of clear vinyl tubing and put it over the wire from the coil to the distributor and secured it with a Ty-Wrap since the wire was touching metal parts. Since those modifications the system works better than it did when new. Ever shop that has ever worked on the engine has disabled the turbo by reconnecting the vacuum lines to the pop-off valve to the wrong port. I finally learned just to correct the mistake myself after getting the vehicle out of the shop.
When I first had the turbo system installed I lived at sea level and the shop in San Diego that designed the system was also at low elevation. When I moved to New Mexico and had the car on a dyno it was found that the fuel mapper didn't have sufficient dynamic range to give the right mix at 5k plus feet. It has run slightly rich ever since. At that time it was producing about 380 hp at the rear wheels (at a mile high), corrected for elevation and drive train losses that is probably equivalent to nearly 450 SAE hp. A performance shop with a dyno just opened in my town and I've talked to them about testing the car again and possibly replacing the mapper with something that can deal with driving in the 5 - 10K foot elevations in my neck of the woods (e.g. the Million Dollar Highway (Hwy. 550) from Durango, CO through Silverton, Ouray and on north.)
The first picture below is an overview of the engine bay. The air intake is at the lower left, the K&N air filter was removed when the picture was taken. The air flows in through the mass sensor and enters the turbo compressor. The pressurized (and heated) air exits downward into a pipe leading to the intercooler. The return from the intercooler is the pipe that runs over the turbo and into the intake manifold.
The second picture is a closeup of the turbo itself.
I've been thinking about designing a custom strut brace since ones designed for a stock SC probably wouldn't clear the pipe going into the manifold but if anyone has info otherwise please reply. Note how close to the passenger side strut tower the pipe is. I have to determine the clearance between the pipe and the inside of the hood when it is closed. I think I'll get a chunk of Plasticene (synthetic clay) and place it between a couple of small pieces of Masonite, place that on the pipe and close the hood. It should squish down when the hood is, slowly, closed and then I'll be able to measure the available height. I'm thinking two mounting brackets on the strut towers held on by fasteners screwed on the strut mounting bolts and then a brace between them that attaches to the brackets on the outboard side of the strut towers..
To move the turbo and inlet pipe further away from the distributor cap I used doubled graphite gaskets on both the manifold to block joint and also the manifold to turbo joint. I had to slightly enlarge one of the mounting holes on the turbo housing because of the change in geometry. Try hand filing 1/4" thick cast iron to remove about 1/8" of material! I also slightly flattened the strut tower adjacent to the turbo to make sure that when the engine moved slightly on it mounts that it wouldn't hit the sheetmetal. There is also a piece of white PVC pipe slit and placed over the pipe joint where it is close to the distributor cap as an electrical insulator. I also slit a piece of clear vinyl tubing and put it over the wire from the coil to the distributor and secured it with a Ty-Wrap since the wire was touching metal parts. Since those modifications the system works better than it did when new. Ever shop that has ever worked on the engine has disabled the turbo by reconnecting the vacuum lines to the pop-off valve to the wrong port. I finally learned just to correct the mistake myself after getting the vehicle out of the shop.
When I first had the turbo system installed I lived at sea level and the shop in San Diego that designed the system was also at low elevation. When I moved to New Mexico and had the car on a dyno it was found that the fuel mapper didn't have sufficient dynamic range to give the right mix at 5k plus feet. It has run slightly rich ever since. At that time it was producing about 380 hp at the rear wheels (at a mile high), corrected for elevation and drive train losses that is probably equivalent to nearly 450 SAE hp. A performance shop with a dyno just opened in my town and I've talked to them about testing the car again and possibly replacing the mapper with something that can deal with driving in the 5 - 10K foot elevations in my neck of the woods (e.g. the Million Dollar Highway (Hwy. 550) from Durango, CO through Silverton, Ouray and on north.)
The first picture below is an overview of the engine bay. The air intake is at the lower left, the K&N air filter was removed when the picture was taken. The air flows in through the mass sensor and enters the turbo compressor. The pressurized (and heated) air exits downward into a pipe leading to the intercooler. The return from the intercooler is the pipe that runs over the turbo and into the intake manifold.
The second picture is a closeup of the turbo itself.
I've been thinking about designing a custom strut brace since ones designed for a stock SC probably wouldn't clear the pipe going into the manifold but if anyone has info otherwise please reply. Note how close to the passenger side strut tower the pipe is. I have to determine the clearance between the pipe and the inside of the hood when it is closed. I think I'll get a chunk of Plasticene (synthetic clay) and place it between a couple of small pieces of Masonite, place that on the pipe and close the hood. It should squish down when the hood is, slowly, closed and then I'll be able to measure the available height. I'm thinking two mounting brackets on the strut towers held on by fasteners screwed on the strut mounting bolts and then a brace between them that attaches to the brackets on the outboard side of the strut towers..
Last edited by davmar; 02-09-13 at 10:22 AM.
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