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jcd06 (Electrical) (OP)
5 Apr 12 7:52
thread71-233418: Supercharger bypass valve operation

I just noticed my previous thread beeing closed. The experiment is definitely a slow process pipe     
Here is some updat about this toppic.


I installed a Lysholm LYS1200 supercharger instead of the Eaton M45.
The crankshaft pulley I had before was of no use any more because the new charger has a displacement of 1.2L/rev as compared to the Eaton M45 that had only 0.75L/rev.
At the moment I am using a crank pulley which is slightly larger than the stock one and it gives me 0.85bar of boost which is enough for the time being.

First I did some tests with the throttle in the stock position and with the MB bypass valve still mounted. Throttle response felt just like with the Eaton charger, mainly influenced by the bypass valve operation.
Bypassing the Lysholm which is a charger with internal compression is of course not the way to go because the recycled air is pulsating and these pulses find their way out through the air filter.
Pretty noisy I must say smile

Then I moved the throttle body upstream of the charger. From then on, the charger itself, the intercooler and connecting ducts are under plenum vacuum when off throttle. That's why I ditched the Volvo intercooler which was not designed for this operating condition and I got myself a full aluminium welded item.

In principle the bypass valve is no longer needed but I prefer to keep it there for testing purposes. For driving I just leave it closed now.
I can not say too much about throttle response because I have not been measuring it yet, but what I can tell is that it feels much more natural than when the bypass valve was playing a role. I dare to say that it matches very closely the feeling of a naturally aspirated engine, even much better than the OEM Mercedes-Eaton combo where the bypass valve is ECU driven together with Electronic Throttle Control.

Further testing/playing will not be before autumn because of other priorities.
And even then there are a couple of other issues to be tackled first.
Remote oil filter has to be relocated and alleged coolant pump cavitation investigated.
To be continued...
 

Train dogs,
Teach people.

gruntguru (Mechanical)
8 Apr 12 3:41
It doesn't sound like you are experiencing the poor throttle response predicted by all the naysayers then?

Engineering is the art of creating things you need, from things you can get.

jcd06 (Electrical) (OP)
9 Apr 12 8:59
It does not at all feel a poor throttle response but I definitely need to measure pressure build up in the inlet plenum to support this statement.
I did pay much attention to the volume of the system downstream of the charger. The total of intercooler and ducts adds only about 8 liter to the stock situation.
The smaller this volume, the faster it gets pressurised.

In this respect, turbo's have no advantage over fixed displacement chargers but in their case it's conveniently confused with "lag".
 

Train dogs,
Teach people.

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