madteg
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| posted on 17/12/07 at 10:23 PM |
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how much boost can i run
Dors anybody know how much boost i should be running on 2.0L black top zetec.
Running 803 bosch injectors (330cc) throttle boddies, subaru turbo,running 7psi at the moment.
[Edited on 17/12/07 by madteg]
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oadamo
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| posted on 17/12/07 at 10:43 PM |
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with a decompression plate my mate runs 1 bar.
adam
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Confused but excited.
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| posted on 17/12/07 at 11:06 PM |
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I would have thought it depends how long you want it to last.
Running at 7psig won't put as much strain on your engine, as tuning it (hot cams, ported head etc) to rev substantially higher than standard
will. IMHO.
Tha' dun't get owt f'r nowt.
[Edited on 17/12/07 by Confused but excited.]
Tell them about the bent treacle edges!
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BenB
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| posted on 18/12/07 at 08:52 AM |
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It kinds of depends how much the decompression plate decompresses it, what intercooler you have etc etc etc.... At the end of the day there are two
answers here
1) get a book like Graham Bell's forced induction tuning, get a rough estimate then aim for 10% less boost (ie keep on the safe side)
2) initially set it up with little boost then gradually increase it until the engine goes pop and then run your new engine at 10% less than that 
And hope the new engine doesn't have coked pistons or anything else that would increase detonation....
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Volvorsport
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| posted on 18/12/07 at 10:59 AM |
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i would say with 330cc injecctors around 12-14 psi , any more , needs bigger injectors , but that depends on lots of things
www.dbsmotorsport.co.uk
getting dirty under a bus
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djtom
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| posted on 18/12/07 at 01:35 PM |
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My silvertop Zetec Turbo is set up with a decompression plate that lowers the C/R to about 8.5:1, running megasquirt and 460cc injectors with a turbo
from a JCB (!) (also used on the Volvo T5).
I've been running mine at 5-6 psi for the last few months with no issues, and a couple of weeks ago I wound it up to 12psi. Holy sh*t - what a
difference! It was quick before, but it's ridiculous now!
Only problem is that I have now had to wind it back down to 6 psi as whilst I was at a trackday at Bedford on Sat I discovered that the clutch was
slipping at anything over 5000 rpm in 3rd, 4th and 5th (and not just slipping, but just giving up in a cloud of smoke and a horrible smell while the
engine bounced off the limiter...)
Once back down at 6psi it seemed ok, but I'll be looking for a new stronger clutch soon.
Anyway, back to your question:
Long answer:
The main factor affecting you is detonation, which will kill an engine (holed / melted pistons, broken ring lands etc). This is a factor of several
things, like static c/r, boost, fuel octane, air-fuel-ratio under boost (aim for 12:1 under boost to keep things reasonably safe) and perhaps most
importantly, ignition timing.
All of these things work together to determine the amount of boost that you can run before things go horribly wrong. I strongly suggest reading Forced
Induction Performance Tuning by Graham Bell and also the Turbobricks forum (lots of crazy swedes turbocharging Volvos - they are very helpful with
things like ignition retard under boost), and developing your own idea of what to look for and monitor under boost.
Short answer:
No more than 12-14 psi as said above, and that assumes that your ECU allows you to retard the spark under boost and that the rest of the drivetrain is
up to it (clutch and gearbox!)
Good Luck!
Tom
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Toady1
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| posted on 18/12/07 at 04:59 PM |
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I was going to say it all depends on what sort of compression ratio you're running, and what means you have of detecting det.
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MikeRJ
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| posted on 18/12/07 at 05:02 PM |
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Squish is one of the parameters that can delay the onset of detonation. Unfortunately, fitting a decompression plate removes any squish band the
engine may have had.
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