This is somewhat as a follow-up on the threads about Supercharger bypass valve operation.
In my current set-up I'm not using the bypass valve any more.
The charger is downstream of the throttle valve so there is no necessity for a bypass.
The famous valve is still installed and operatable and I noticed a decrease in engine load when opening the bypass at idle. So for production cars it could be an advantage in terms of consumption to bypass a Lysholm charger at idle - at the cost of some supplementary parts and wiring.
In case of a Roots charger which has no internal compression, the gain will probably be a lot less.
This update is about throttle response in particular.
Just to make things clear I will describe shortly the two different set-ups compared.
In the first thread [URL unfurl="true"]http://www.eng-tips.com/viewthread.cfm?qid=233418[/url] the order of parts was:
1 air filter and hot-wire MAF
2 Eaton M45 charger with electric bypass valve
3 intercooler
4 from then on, all stock engine: throttle valve and inlet plenum.
In this thread (and the previous one [URL unfurl="true"]http://www.eng-tips.com/viewthread.cfm?qid=319537[/url]) the set-up:
1 air filter and hot-wire MAF
2 throttle valve
3 Lysholm LYS1200 charger
4 intercooler
5 inlet plenum.
While I got a more crisp and natural feeling throttle response with the throttle upstream of the charger, the measured time for boost build-up inside the plenum was longer (after a sudden WOT).
Time needed for the boost to rise till 95% of its nominal value, typically 510ms with the first set-up, 580ms for the second one.
What was then causing the better throttle response?
I could find only one reason.
In the first set-up MAF signal was lagging 230ms behind the TPS signal, while in the second set-up this lag was not even measurable (logging sample frequency was 10ms).
There are about 60cm of straight duct and one 90 degree bend between the MAF and the throttle.
I'll be glad to hear any comments about this response matter as well as about anything else with regard to this testing.
It is not unlikely that there is a rich spot in-between the moment that the sudden WOT is translated into a MAF signal rise and 580ms later when the engine -or at least the plenum- gets it boost.
The ECU gets its load information from the MAF, not from a MAP.
I could not feel any anomaly but unfortunately I did not log AFR this time so I can't tell for sure.
During summer I hope to find the time to run the car on its favourite track again and assess this new set-up in its whole.
What I also logged during this test carried out lately is the coolant pressure in the cylinder head, just upstream of the thermostat. But this is a different story and I will start a new thread for this soon.
Good night, and good luck,
Jean
When we all think alike, no one thinks very much. ---Walter Lippmann
In my current set-up I'm not using the bypass valve any more.
The charger is downstream of the throttle valve so there is no necessity for a bypass.
The famous valve is still installed and operatable and I noticed a decrease in engine load when opening the bypass at idle. So for production cars it could be an advantage in terms of consumption to bypass a Lysholm charger at idle - at the cost of some supplementary parts and wiring.
In case of a Roots charger which has no internal compression, the gain will probably be a lot less.
This update is about throttle response in particular.
Just to make things clear I will describe shortly the two different set-ups compared.
In the first thread [URL unfurl="true"]http://www.eng-tips.com/viewthread.cfm?qid=233418[/url] the order of parts was:
1 air filter and hot-wire MAF
2 Eaton M45 charger with electric bypass valve
3 intercooler
4 from then on, all stock engine: throttle valve and inlet plenum.
In this thread (and the previous one [URL unfurl="true"]http://www.eng-tips.com/viewthread.cfm?qid=319537[/url]) the set-up:
1 air filter and hot-wire MAF
2 throttle valve
3 Lysholm LYS1200 charger
4 intercooler
5 inlet plenum.
While I got a more crisp and natural feeling throttle response with the throttle upstream of the charger, the measured time for boost build-up inside the plenum was longer (after a sudden WOT).
Time needed for the boost to rise till 95% of its nominal value, typically 510ms with the first set-up, 580ms for the second one.
What was then causing the better throttle response?
I could find only one reason.
In the first set-up MAF signal was lagging 230ms behind the TPS signal, while in the second set-up this lag was not even measurable (logging sample frequency was 10ms).
There are about 60cm of straight duct and one 90 degree bend between the MAF and the throttle.
I'll be glad to hear any comments about this response matter as well as about anything else with regard to this testing.
It is not unlikely that there is a rich spot in-between the moment that the sudden WOT is translated into a MAF signal rise and 580ms later when the engine -or at least the plenum- gets it boost.
The ECU gets its load information from the MAF, not from a MAP.
I could not feel any anomaly but unfortunately I did not log AFR this time so I can't tell for sure.
During summer I hope to find the time to run the car on its favourite track again and assess this new set-up in its whole.
What I also logged during this test carried out lately is the coolant pressure in the cylinder head, just upstream of the thermostat. But this is a different story and I will start a new thread for this soon.
Good night, and good luck,
Jean
When we all think alike, no one thinks very much. ---Walter Lippmann
