DOHC turbo ?

Discussion in 'Front-Engine Rear Drive Fiats' started by Dr.Jeff, Mar 23, 2019.

  1. I would guess you are in the right ballpark. In the mid 90s, Volvo had a low pressure (~8 psi) version of their turbo that put out 160 hp from 2.4 liters. It had thinner cylinder walls than the high pressure 2.3 liter turbo, and lacked the sodium filled exhaust valves, and probably a few other things.
     
  2. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    More 'modern' engine designs with those boost levels get considerably higher results than what I speculated in my last post. But I was being conservative considering what we are working with here.

    The improvements gained in turbo and engine management technologies makes whatever was done in the 80's or 90's less relevant now. But these engines themselves really haven't changed, so I imagine the outcomes will be better than in past experiences but not what newer engines see. The kind of things that should be significantly better are drivability, reliability, economy, etc.
     
  3. fiatfactory

    fiatfactory Steve Cecchele

    Location:
    Western Australia
    dohc 8v draw thru turbo setup....that's a 55DCOE in front of it... approx 300hp with 22psi boost

    UnoT2000.jpg

    SteveC
     
    rachaeljf likes this.
  4. rachaeljf

    rachaeljf True Classic

    Location:
    Northampton UK
    Now that's old school! Love the pressure switches.
     
  5. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    That was EXACTLY my thought when I saw the pic! Are the springs that hold the downpipe to the turbine housing actually the wastegate? :D Only joking.

    Based on that result, I imagine 22lb of boost with FI, intercooler, and modern ECU controlling the fuel and spark would yield somewhere closer to 350hp? But not sure if the engine would hold it for long.
     
    gene cooley likes this.
  6. fiatfactory

    fiatfactory Steve Cecchele

    Location:
    Western Australia
    The Uno 2000 Turbo is my Dad's work, so yes very old school.... the Hobbs pressure switches control the solenoid valves that allow fuel and water / methanol mix to be injected at different boost levels into the inlet manifold and just ahead of the compressor turbine.... there are four lights on the dash...at something like 5, 12, 17 and 20psi various solenoids would switch open and allow additional fueling...and they came on pretty quickly when you got on the loud pedal (always reminded me if an old pinball machine "tilt" lights) as when all lights were lit the thing sat you back in the seat.

    EFI, intercooled and electronically managed 8 valve turbo.... just think group A 8 valve lancia integrale with about 550 hp....16valve examples of lampredi twin cams with turbochargers get up around 950hp for hillclimbing in europe when the engine builder gets serious.

    You underestimate the internal strength of these engine Jeff, that 300 hp (which is conservative) at 22 psi is all day... for hours at a time in long distance (300km long) races, and up to 28psi (that's two bar) in qualifying.... with all stock internal engine parts except or the forged pistons and the big end bearing shells (chevrolet V8 b/e brg conversion to allow for use of high quality bearing materials)

    SteveC
     
  7. Chad C.

    Chad C. True Classic

    Location:
    Eugene, Oregon
  8. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    That same manifold is also available directly from the manufacturer:
    https://spaturbousa.com/products/sp...iat-124-spider-131-lancia-coupe-2-0l-8v-tmf04

    I have no specific application in mind. As I work through the 'turbo SOHC' application project it seemed an obvious choice to do the same to the DOHC. In my opinion either format of engine will yield greater performance levels, with a more "usable" power band, for less money than the traditional NA performance build.
     
  9. gene cooley

    gene cooley Autocrosser

    Location:
    Henrico, Va
    Jeff, I was changing out the throttle body on the 600 and I took some pics of our 58mm GM tb. Not a suggestion of what to use but just an example of what's available, cheap, and easily adapted to almost any intake manifold.
    As shown it has a cable throttle, TPS is built in and replaceable, idle system is the same.
    All are usable with Megasquirt. 20190412_110556.jpg 20190412_110556.jpg 20190412_110536.jpg 20190412_110536.jpg
    These are usually available at "Pick Your Parts" complete with sensors and some wiring for $15-35.
    (And again I got double pics but I know why now)
     
  10. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Nice. Looks like you have it mounted on a carb manifold? What are you doing for injectors?

    For my SOHC (X1/9) turbo project I was attempting to keep things as simple and easy as possible. It already had the factory FI system, so I'm retaining the whole intake manifold, throttle body (had to use a different TPS on it, for MegaSquirt), injector rail, etc. But I agree for maximum performance a larger throttle is needed, along with different type of injector rail.
     
  11. gene cooley

    gene cooley Autocrosser

    Location:
    Henrico, Va
    The manifold is one I was using on the Ecotec, it's from the Turbo 2.0 (Solstice, Cobalt etc.). I adapted it to our 2.2L engine. Just using it to make an adapter plate right now. We are doing a test, removing a 72mm tb and replacing it with the original 58mm on yet another manifold. We have 3 different manifolds.
    With a Fiat SOHC or DOHC I would stick with our GM parts. Other than being usable with Megasquirt, most of the parts are readily available either new or used. Some parts would be aftermarket--crank position sensor, knock sensor and the turbo related parts. I would probably adapt a GM tb to a Fiat carb manifold and do whatever to install the GM injectors.
    As I said, this is all personal preference on my part, using what I'm familiar with.
     
  12. carl

    carl True Classic

    Location:
    Virginia
    You are getting a ton of great advice here but you might also want to query MIRA since that's mostly the twin cam guys. Over there, James Seabolt is the only guy I know doodling around with turbos on his spider but I think his build is several years old and was mostly an update of the factory setup.
     
  13. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Thanks guys. I'm not looking to build a TC engine, turbo or otherwise. I just wondered if anyone has done it, what's been learned from it, and if anything would offer information toward my SOHC turbo project.
     

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