Turbo for T4 - Page 2

soro · Mar 18th, 2008, 10:54

Hi guys, it eventually took Volvo mechanics almost 4 hours to replace the turbo... and they even charged me extras for the gaskets and some admin time to actually get them from overseas so total was quite close to price of the unit itself...but the turbo is in and it just works great. I took my T4 for a good spin today and it passed with flying colours. No whine. The old twin stroll unit had its inner wall cracked and that was (probably) causing the whine. Not sure if it is worth repairing as brand new single stroll units can be bought cheaply. The crack in the wall makes me think that two stroll units are badly designed. The wall should have been probably thicker.

Now comparison between single and twin stroll turbo:

Low speeds: Single stroll is a winner. It has smaller fans and therefore it is faster to spool. Incredibly responsive, no lag and the revs don't even have to go over 2500 to enjoy acceleration. Twin stroll had a noticeable lag at low speeds and I had to push the pedal right down to make it to kick in, which was bad for fuel consumption I guess.

High speeds: Twin scroll seems to be the winner but only just. With its bigger fans it has slightly more grunt and it works best between 70-100 km/h. There is no noticeable lag with either unit at these speeds.

I am not after extra horse power and ultra performance but still want to reasonably enjoy driving so this turbo works for me just fine. Lets hope it will last...
Thanks again for all your input.

Cheers

Enigma666 · Mar 18th, 2008, 15:30

Erm...aren't the internals identical? It's all to do with the veins or something.
The twin scroll is meant to spool faster (only slightly though).
Maybe i'm wrong, but then again I will have nothing but lag to worry about soon....once th lag has gone though it'll be one hell of a ride

Dandle · Mar 18th, 2008, 16:27

The whole reason the twin scroll was introduced was to reduce the spool up time from the single scroll unit which reduces the lag slightly. Kinda proves your original turbo wasnt running correctly.

I have always been led to believe the difference between single scroll and twin scroll is as in the pic I have linked (i know they are two different size compressor wheels but its a good pic)http://i4.photobucket.com/albums/y11...vs-Big16G2.jpg. With the twin scroll compressor in the right hand turbo and the single scroll on the L/H unit. The twin scroll is able to grap more air as the turbine speed varies. Thats what gives it less lag.

thebigv · Aug 18th, 2009, 23:26

Quote:

Originally Posted by Dandle

The whole reason the twin scroll was introduced was to reduce the spool up time from the single scroll unit which reduces the lag slightly. Kinda proves your original turbo wasnt running correctly.

I have always been led to believe the difference between single scroll and twin scroll is as in the pic I have linked (i know they are two different size compressor wheels but its a good pic)http://i4.photobucket.com/albums/y11...vs-Big16G2.jpg. With the twin scroll compressor in the right hand turbo and the single scroll on the L/H unit. The twin scroll is able to grap more air as the turbine speed varies. Thats what gives it less lag.

The twin scroll is the turbine side, not compressor. It has two ports coming from the 1 and 4 cylinders and 2 and 3 cylinders that meet each other to even out engine pulses. The manifold and turbine side are different internally other than that the turbos are the same.

Dandle · Aug 19th, 2009, 06:26

Your right i was getting mixed up with the compressor wheels like the two turbos above.

Mar 18th, 2008, 10:54	#11
soro New Member Last Online: Apr 3rd, 2008 11:06 Join Date: Mar 2008 Location: Hastings	Hi guys, it eventually took Volvo mechanics almost 4 hours to replace the turbo... and they even charged me extras for the gaskets and some admin time to actually get them from overseas so total was quite close to price of the unit itself...but the turbo is in and it just works great. I took my T4 for a good spin today and it passed with flying colours. No whine. The old twin stroll unit had its inner wall cracked and that was (probably) causing the whine. Not sure if it is worth repairing as brand new single stroll units can be bought cheaply. The crack in the wall makes me think that two stroll units are badly designed. The wall should have been probably thicker. Now comparison between single and twin stroll turbo: Low speeds: Single stroll is a winner. It has smaller fans and therefore it is faster to spool. Incredibly responsive, no lag and the revs don't even have to go over 2500 to enjoy acceleration. Twin stroll had a noticeable lag at low speeds and I had to push the pedal right down to make it to kick in, which was bad for fuel consumption I guess. High speeds: Twin scroll seems to be the winner but only just. With its bigger fans it has slightly more grunt and it works best between 70-100 km/h. There is no noticeable lag with either unit at these speeds. I am not after extra horse power and ultra performance but still want to reasonably enjoy driving so this turbo works for me just fine. Lets hope it will last... Thanks again for all your input. Cheers Last edited by soro; Mar 18th, 2008 at 11:08. Reason: typo

Mar 18th, 2008, 16:27	#13
Dandle Master Member Last Online: Dec 29th, 2013 22:39 Join Date: Dec 2003 Location: Ashford	The whole reason the twin scroll was introduced was to reduce the spool up time from the single scroll unit which reduces the lag slightly. Kinda proves your original turbo wasnt running correctly. I have always been led to believe the difference between single scroll and twin scroll is as in the pic I have linked (i know they are two different size compressor wheels but its a good pic)http://i4.photobucket.com/albums/y11...vs-Big16G2.jpg. With the twin scroll compressor in the right hand turbo and the single scroll on the L/H unit. The twin scroll is able to grap more air as the turbine speed varies. Thats what gives it less lag. Last edited by Dandle; Mar 18th, 2008 at 16:38.

Mar 18th, 2008, 15:30	#12
Enigma666 Master Member Last Online: Apr 16th, 2021 11:32 Join Date: Aug 2006 Location: Chester	Erm...aren't the internals identical? It's all to do with the veins or something. The twin scroll is meant to spool faster (only slightly though). Maybe i'm wrong, but then again I will have nothing but lag to worry about soon....once th lag has gone though it'll be one hell of a ride

Aug 19th, 2009, 06:26	#15
Dandle Master Member Last Online: Dec 29th, 2013 22:39 Join Date: Dec 2003 Location: Ashford	Your right i was getting mixed up with the compressor wheels like the two turbos above.

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