Quote:
Originally Posted by Alan M
An aftermarket Recic will work much in the same way as the standard item fitted to the side of the Td04hl series. If you remove the standard item then fit a blanking plate the aftermarket item can be fitted before the throttle butterfly, as near as possible for best results, then when the throttle butterfly closes the charge air will recirc back into the metered system, as it does with the standard item. There will be no false reading and no extra air being fed into the system as the metered air will not be exiting the system but will be 'recirculated'. The air being fed back into the Maf intake may be warmer than ambient but it is after the Maf and will be heated by the turbo, back to the charge temp before entering the intercooler, earlier on in the cycle. It repeats the same cycle again and again hence the 'recirculating' name.
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The recirculating valves fitted to all turbo charged cars flow the air behind the throttle plate, because when you lift off the throttle to change gear it closes the throttle plate stopping the compressed airflow from the turbo. This air has to go somewhere and without a recirc valve goes into the turbo again and CAN cause compressor stall. This generally only happens with drastic effect withover 14psi of boost. Manufacturers install recirc valves to flow that excess air passed the throttle plate so it keeps the engine running as it should, maximises turbo efficiency and boost and also prevents stall.
An aftermarket recirc valve will work in pretty much the same way. When you mention fitting it as close the the throttle plate etc your on about recommendations for fitting dump valves etc as they want the excess air to exit the system as fast as possible and with the valve being so close to where pressure builds it releases quicker, also it'll create a vacuum, drawing the excess air out of the pipework and away from the turbo, and also keep the turbp spooling. What they dont do however is supply air into the inlet manifold AFTER the throttle plate.