Dump valve differences

[RSF]

Might seem a silly question but I have a idea but don't know the exact answer,hence the question.

What is the difference between single and double valved dump valves?
What differences do they make?
What exactly is the idea behind them except woosh?
Why is the single no good for the 850 t5?
will it harm my engine at all?
Thank's.

[RSF]

Originally Posted by RSF

Might seem a silly question but I have a idea but don't know the exact answer,hence the question.

What is the difference between single and double valved dump valves?
What differences do they make?
What exactly is the idea behind them except woosh?
Why is the single no good for the 850 t5?
will it harm my engine at all?
Thank's.

Double pistoned I ment.
Reason I am asking is I was advised to take mine off,1 it wasnt fitted right and 2 it was a single piston.
tbh I dont like the noise of them but if there helping the car then hey I'l live with the noise.
Forgive me for silly question's,playing with turbos,ecu's,dump valves,mbc's are quite new to me.

[thebigv]

Dump valves act in the same way as a recirculating valve, once the throttle plate is closed the compressed air in the inlet pipes cannot go anywhere and the recirc valve pushes it through the smaller pipes passed the throttle plate to A) keep the turbo spooling and B) keep the ecu measuring properly. All the dump valve does is bypass the recirc feature of putting the air passed the plate and dumps it to air. Although the ecu thinks its stopped flowing etc and runs poor, leana nd then rich.

[RSF]

Thanks for reply.
Whats the difference with the single and twin pistons?
Do I have to use a blanking plate on the 850 T5 or am I ok to plum in to the re circ pipe?

Think this is a single piston I have here and fuel consumption was very poor while it was on,all I know is,single pistons cant go on cars with mass air flow metres but cant understand why and what is the difference as the one I have I've seen in single and twin piston.

Thanks

[thebigv]

You cant plum the recirc and the blanking plate in together, well you can but i wouldn't advise it because your ecu will get too many different messages, basically when the throttle shuts the compressed air has nowhere to go, the recirculating valve, recirculates the air through it and passed the throttle plate keeping the air flowing and the fuel air ratio sweet, however a dump valve does what it says on the tin, dumps it into the air,thereby stopping airflow during closed throttle. The ecu thinks its starving of air so retards fuel, therefore your engine runs lean, then when the throttle opens again it gets a great big boost of air and the ecu throws a load of fuel in, making it run rich, then you change gear agian and it goes on and on until the engine doesn't haha. Some cars it affects greater than others, my T4 doesn't like one at all, whereas another guy swears by his. Twin pistons split the air intake and dumping so that the loop isnt totally open to the atmosphere giving some pressure to push back through the system Still not great but better.

[Alan M]

It is possible to fit your blanking plate then fit an aftermarket recirculating valve back into the pre turbo Maf pipework.

[thebigv]

Originally Posted by Alan M

It is possible to fit your blanking plate then fit an aftermarket recirculating valve back into the pre turbo Maf pipework.

Recirculating valves supply air flow post turbo and post throttle plate. They plum directly into the inlet manifold. If you plum it pre turbo it'll have even more lag and will also have warmed air being pushed passed the MAF giving a false reading to the ecu. The engine will still run with no air on the engine side of the throttle plate. It needs t flow to the inlet manifold only, nowhere else.

[Alan M]

Originally Posted by thebigv

Recirculating valves supply air flow post turbo and post throttle plate. They plum directly into the inlet manifold. If you plum it pre turbo it'll have even more lag and will also have warmed air being pushed passed the MAF giving a false reading to the ecu. The engine will still run with no air on the engine side of the throttle plate. It needs t flow to the inlet manifold only, nowhere else.

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.

[thebigv]

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.

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.

[Alan M]

Are you for real????

Originally Posted by thebigv

..... Manufacturers install recirc valves to flow that excess air passed the throttle plate so it keeps the engine running as it should....... (No they don't, thats what an IACV does)
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............(No I'm not)
.....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....(no it wont).........
....What they dont do however is supply air into the inlet manifold AFTER the throttle plate....(but you said in the previous paragraph) that- 'Manufacturers install recirc valves to flow that excess air passed the throttle plate so it keeps the engine running as it should.......' (No they don't)

I really do think that a little knowledge is dangerous. You obviously have little knowledge as clearly written by yourself in such a few posts regarding such a simple system.

For you amusment I have supplied the following link of a widely available aftermarket recirculation valve that, as in my above post, is best fitted close to the throttle plate, to reduce the pressure rise against the closed valve (throttle butterfly), and release it back into the intake/induction pipe, after the MAF, as the air is constantly being taken in here to keep the car running. Your IACV supplies a steady amount of air to keep the car at idle whilst the throttle plate is closed and where does this air come from? The intake from the filter housing through the turbo compressor, just where the air is recirculated to (pre compressor after the MAF of course)!!

Link for sample aftermarket Recirculating valvehttp://www.rtecshop.com/index.php?p=...product_id=326

Just so you know, the standard Td04hl series recirc takes air from the discharge side of the compressor and dumps it back into the compressor intake, hence the recirc bit in the name!!! The air is getting recirculated!!

Another jem for you - Compressor stall would occur at high pressure/air volume when the throttle butterfly closes and if it has no where to go so the high pressure/volume of air is forced back through the turbo compressor over the compressor wheel causing a stalling affect as it cannot keep spinning against this opposing force. To remedy this a recirculation or atmospheric release valve is fitted either on the body of the compressor, or as closest to the throttle butterfly as possble (for best results).