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Cylinder Head swap-out...

Discussion in 'The Garage' started by Gato_Solo, Oct 27, 2004.

  1. Gato_Solo

    Gato_Solo Member


    Since you're the mech out there, I have a question. I have a line on a new cylinder head for my Audi...DOHC vs SOHC. Since this head will lower my compression from about 10:1 to about 8.5:1, will getting a turbo cause me heartache if I run at around 10psi?

  2. Kruz

    Kruz Moderator Staff Member

    8.5:1 is fine for turbocharging.. you should have no problems with 10 Lbs of boost. however an intercooler would help out alot..
  3. Gato_Solo

    Gato_Solo Member

    I wasn't too keen on the intercooler because I don't have a lot of room under the hood. I'm just looking for as close to 300HP as I can get without getting too expensive. The cylinder head is gonna cost big, though...around $750...but that's a complete head with the more aggressive cams (272's). The biggest worry I have with that cam setup is my engine will go from non-interference to interference, and the guys I get my ideas from are saying that, if you run boost, things can get ugly fast...Then again, some of those nuts are turning over 450 BHP in motors the same size as mine...
  4. Kruz

    Kruz Moderator Staff Member

    My brother runs 25Lbs of boost on his Grand National ! to do this he also runs alcohol injection using an external (60 psi) fuel pump to an alcohol tank (25% solution)through a nitrous nozzol at the throttle body.. the pump starts automaticly by a pressure switch tee'd into the MAP sensor. when the boost hits 15 psi the alcohol pump starts, and shuts off when boost drops.. so he can run pump gas (94 octane) with no detonation. (because the alcohol solution cools the combustion chamber). :shooter:
  5. Inkara1

    Inkara1 New Member

    You can get 94 Octane out there? The highest you can get at every starion I've been to in California is 92.
  6. leslie

    leslie New Member

    wow, yet another thread which I fully cannot comprehend. :retard:

    *feeling like a girlygirl*
  7. Gato_Solo

    Gato_Solo Member

    Just invest in Octane 104 with each tank of fuel...
  8. Inkara1

    Inkara1 New Member

    Gato said he had the hook-up for a new cylinder head for the engine in his car. The cylinder head is the top part, where the valves (what lets in gas/air and lets out exhaust) and the spark plugs are. The camshafts are what open and close the valves, and the new cylinder head has two of them instead of just one. This means the engine can rev higher because each camshaft has less work to do. The new head has a lower compression ratio, which means the gas/air misture will be compressed a little less when the piston is at top dead center. But this won't be a problem because he wants to slap on a turbocharger (a piece where the exhaust gas flowing out of the engine drives some gears which in turn compress the air going into the engine). Gato then asked if this turbo would be likely to cause a lot of problems if it's set to boost the incoming air by 10 psi.

    Kruz said he should be fine, but would be better off if he added an intercooler (a piece that cools down the compressed air to make the engine run more efficiently and control heat).

    Gato then said he didn't really like the idea of adding an intercooler because he doesn't have a lot of spare room under the hood. He also said that he wants to get to around 300 horsepower for as little cost as he can, although the new head will cost him a pretty penny; but the camshafts are more agressive (they're set to open and close the valves at the right time for higher performance at the detriment of fuel economy and smooth idle). But his big worry about all this is that the engine, with the new head on it, will now be an interference-type (that means that if the timing belt, which turns the camshafts, breaks or something else breaks, the valves could remain open when they should be closed, and as the pistons continue to move up and down they would strike the valves, resulting in an amazing amount of damage to the engine). The people who have done projects similar to his (new head and a turbo) have said that if something goes wrong, the problems compound fast. But then again, these same people run a lot higher boost and are getting 425 horsepower out of their engines, while Gato is only looking to get about 300 horsepower out of it, meaning he would be stressing the engine less.

    Kruz then posted an anecdote about his brother's Buick Grand National, which has some very agressive turbocharging. The gist of it is that he's got a trick setup to allow him to run that much boost while still being able to run gas you can buy at a regular gas station. The higher the octane rating, the more it can resist detonation ("pinging," when the gas ignites before the spark plug fires... which can really damage the engine too). Kruz's brother has to run supreme unleaded, but at least he doesn't have to use racing gas.

    I was surprised because he said his brother buys 94 octane cas for it, and the highest octane rating I've seen out here is 92.

    Then, you said you don't understand the thread.

    Next, Gato said you can get 94-octane gas from 92-octane if you add in a bottle of Octane 104, which is an octane booster that you pour into the gas tank when you fill it up.

    Finally, I summarized the thread.

    Clear now? :D
  9. leslie

    leslie New Member


    That is absolutely perfect, Inky! Plain English makes things soooo much easier :D
  10. Kruz

    Kruz Moderator Staff Member

    Hey Ink...... we got an opening down at the dealership here.... Interested? :beerchug:

    *You know more than our service people do* :retard:

    ps.*94 octane fuel is here in the east coast... there are even 2-3 sunoco stations locally that sell 100 octane unleaded*
  11. Inkara1

    Inkara1 New Member

    What's the position and what's the pay? I'm sure I could adjust to Georgia life... :D
  12. Gato_Solo

    Gato_Solo Member

    Just found out I'd have to replace the ECU as well. This looks like it's really going to cost, as the 'new' ECU will cost more than twice the price of the head. :banghead: I'll also need a new fuel injector system... :banghead:

    Let's whip out the handy calculator and see what this 'package' will eventually cost me...

    Cylinder Head....................$609.45 + $150 core charge
    Fuel Rail...........................$115
    Custom exhaust manifold.....$525 (includes turbo "downpipe")


    Since I'm not as 'mechanically inclined', labor has to be included. I figure, roughly, $65.00 per hour. Swapping out the head is about a 2 to 3 hour job. Changing the fuel rail could possibly be done at the same time...if not, add another hour. Since I can run wiring (if it's labled properly) I could take care of the ECU myself, but there's still that nasty problem of the fuel distributer...Will it be up to the task?
  13. leslie

    leslie New Member

    why? why do you have to replace the ECU? it won't adjust and compensate?
  14. Gato_Solo

    Gato_Solo Member

    Because it's hard-wired to do the job specific to the standard motor/head combo. I'm going to be building 'Frankenstein', so I need an A.B.Normal brain. One that can, basically, adjust and compensate for the new head, and fuel distrobution system.
  15. Inkara1

    Inkara1 New Member

    Did you remember to throw in the cost of a gasket set too? They're not as cheap as one would think, and you can't re-use a head gasket, after all.
  16. Gato_Solo

    Gato_Solo Member

    Actually, the gasket comes with the 'complete' cylinder head. The one question I really have before plunging into this is...will I be able to get this all together, and working, with that budget. Most likely not, but it's a real nice dream. ;) :smoke:
  17. Gato_Solo

    Gato_Solo Member

    BTW...this is what the engine compartment looks like...which is why there will be no intercooler if I can get the scratch to pull this off...

  18. Inkara1

    Inkara1 New Member

    I know what you mean about the cramped compartment.

    Oddly enough, though, there's a good bit of room between the engine and firewall in my Neon. I could probably fit a lot of turbo stuff back there.
  19. Gato_Solo

    Gato_Solo Member

    I discovered that the new head doesn't come with an intake manifold, and my existing manifold won't work with the new head, so I went out searching, and I found an intake manifold...a new intake manifold... :clap:

    Then I saw the price...

    1690 Euros...which comes out to over 2100 USD. :banghead: It's supposed to be good for over 380 horses, though... :evil:

    Anyhow...once I get the head in, the engine compartment should look similar to this...


    ...just without the '20V' symbols...
  20. Professur

    Professur Mushroom at large

    This is the part where I usually suggest saving the money, and buying an old Buick and dropping in a crate 572.

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