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Turbo Modifications

IHI RHB5 turbo piecesAfter finding all of the parts that were left of the stock IHI RHB5 turbo from the RS, I needed to get it repaired or replaced. The turbo shaft had broken in half, and also broken clean off of the turbine. I started calling around and found out that it would cost me a minimum of $800 just to get it repaired and rebuilt, or $1900 to replace(and the local Isuzu dealer- McCloskey Isuzu - actually had one in stock!). I was starting to get discouraged at that point, as my cheap find was gonna start adding up.

Well, I started doing research and educating myself about turbo technology and learned that I really only needed was a replacement Turbo Cartridge instead of the whole turbo. I found out that IHI made turbos for many cars in the '88-95 years, so it was just a matter of finding out which ones used the same cartridge.
My list grew into many possibilities:
IHI- Warner-Ishi (VF119011), RHB5 (also known as vf10), RHB51, RHB52:

  • 90-91 Ford Probe GT
  • 87-91 Mazda MX-6 GT
  • 90-91 Mazda 323 GT
  • 90-91 Mazda 626 GT
  • 90-91 Mazda RX7
  • 90-94 Subaru Legacy Turbo
  • 87-89 Ford Thunderbird Turbo-Coupe(.48 Trim)(Pre '87 came w/ Garrett T03(.60 Trim))
  • 87-89 Mercury Merkur XR4Ti
  • 84-86 Ford Escort
  • ??-?? Ford Laser, Capri
  • ??-?? Fiat Spyder, Ferrari GTO, Delorean
    I called around to a bunch of places to get some prices. . .they all averaged around $300-a lot better than $800!!!
    Then I did a search on Ebay and found them pretty darn cheap. I got 3 turbos in excelent shape-all for less than $150 each. One of the turbos that I got was from the Ford T-bird Turbocoupe, I discovered that it has a larger compressor wheel (.48 trim)--WhooHoo! The Ford Turbo was capable of 381CFM whereas the stock RS turbo is only capable or 200CFM. I disassembled the Turbine housing from the turbo, then took my housing and bolted it right on. . .it was a perfect fit. No machining needed!
    Note: To get the turbine housing off, you may need to use a propane torch. Heat up the Turbine housing evenly-not the center cartridge- for abour 5 minutes, The idea is to expand the turbine housing without expanding the cartridge inside. Tap it lightly with a hammer and it will slide right off. Make sure you disconnect the Wastegate actuator first, so that it doesn't get in the way.

    Warner-ISHI RHB5 Specs:
    Air Flow Rate: 1.4 - 10.8m3/min // 49.4 - 381.4ft3/min
    Max Pressure Ratio: 2.8
    Maximum Speed: 180 x103rpm
    Max Allowable Gas Temp: 9500C // 1742oF
    Diesel Engine Application: 54-154Ps
    Gasoline Engine Application: 73-208Ps
  • You can see the difference between the Ford Thunderbird compressor housing and the stock RS compressor housing. I have to do some custom plumbing to make it all fit together, but that should be the easy part.

    Garrett T3/T4 hybrid turbo

    I got a used Garrett turbo for $100 and spent $190 getting it rebuilt. Here are the specs:
    • .50 AR compressor housing
    • .57 Trim Compressor wheel
    • .48 Trim Turbine wheel

    Here is a comparison of the Stock Impulse RS turbo (Left), Saab T3 turbo (Center), and the Garrett T3/T4 turbo (Right). The Tbird turbo would be between the RS and Saab turbo for comparison. Impulse RS turbo, Saab turbo, Garrett T3/T4 turbo

    Geo Storm isuzu impulse performance parts