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beepbeep beepbeep is offline
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Join Date: Jun 2001
Location: Sweden
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It all depends on what do you want. A stock C/R 3.6 N/A engine won't take much boost before it goes completly out of whack regarding effective compression ratio so C/R will be a limiting factor.

You can relieve this soewhat by using E85 (cheap, needs roughly 40% more fuel flow for same lambda) or race fuel (fussy, expensive). My wide-a$$ed guesstimate is that you shouldn't try to boost more than ~0.5 bar on stock C/R and best petrol found in US...and you should keep your eye on ignition timing while doing that. But yeah, it can probably be done. Go on E85 and you could maybe extend that to 0.7 bar...which would provide some serious power.

About "having 7000 RPM usable range" with cheapskate turbo-conversion: I advise against reving it past 65000. A lighttly boosted stock C/R 3.6 would utilize smaller turbos and give you very nice and usable torque. I bet that such setup would give you max torque around 3500-4000 RPM and max power between 6000-6500 RPM. After that, the huffers would just fall flat on their arses and blow hot air. Your rod bolts will also have a field day and engine will produce more racey noise but not so much power.

It can be relieved by using hotter cams and bigger turbochargers but then you are out of "cheapskate"-range and into "buying expensive parts"-range. And if you are going to buy those, you might as well buy new pistons

So yeah, mildly boosted 3.6 running on E85, using stock cams and fitted into lightweight car will give very driveable and troublefree ride (as long as boost and fueling are kept in check).

As we all know, it's not the top horsepower figure but swept area under power curve that makes things accellerate faster.

So to round it off: if planning to do all this w/o lowering the C/R, concentrate on getting fueling (=lambda), ignition (not too agressive) and boost (not too high) right and don't hunt for expensive 7000 RPM noise-making setup. Chances are the car will be very tractive and torquey even w/o wringing the motors neck. Especially so if fitted in lightweight car.

P.S.
On such turboconversion, you should pay special attention to your ignition system, especially so if using stock distributors. Snapped dizzy sync-belt will leave only one row of plugs firing which might be very problematic when running high effective compression ratio (due to stock C/R and turbocharging).
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Old 03-03-2008, 09:30 AM
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