Bruntingthorpe Boost Curves

[PhilT]

Andiroo

[img]images/rsul/13464-RPM%26Boost-Andy-RS4-BT.jpg[/img]

[PhilT]

RS4 John

[img]images/rsul/13466-RPM%26Boost-JohnS-RS4-BT.jpg[/img]

[PhilT]

SteveFitz

[img]images/rsul/13467-RPM%26Boost-SteveF-RS4-BT.jpg[/img]

[PhilT]

PhilT

[img]images/rsul/13468-RPM%26Boost-PhilT-RS4-BT.jpg[/img]

[jeffw]

Looks like Andiroos is the best boost curve (if I'm reading it right)

[Joshie]

Looks like Andiroos is the best boost curve (if I'm reading it right)

Like feelou I'm consused too.

Can anyone explain which is the optimum curve and why. To the uninitiated like myself it looks like Phil's is the best curve as it holds the boost in a more linear fashion but what do I know.

Who can explain what to look for?

[jeffw]

I was looking at the big momentary drop in Phils and Steves graphs. I always thought that it was sensible to roll off the boost as revs rise towards the red-line.

[rs4steve]

the top graph you see is the revs and changing of gears on the top speed straight the peaks are in 3rd 4th 5th 6th gears the drop off at the end is engine braking/brakes against engine revs the bottom graph shows exactly what boost at what revs, mtm i believe runs lowest boost but peaks at higher revs showing that 6550rpm in 6th =177mph do you agree phil?

[Dippy]

My response to Jeff is, "that depends on the definition of 'best'". In terms of performance the Revo is best as it reaches and holds 1.5 bar. The question is, at what cost to the engine? I also don't like the blip in boost at the end, for no apparent reason.

Remember that the higher the revs, the greater the air flow, so in order to maintain boost, the turbos have to spin faster.

My knowledge is a bit weak here, but turbos, being compressors, have a 'surge line' on the map, above which the turbine presumably surges, such that damage occurs. To stay within the surge line, boost needs to be even more closely controlled at high revs. When I worked in petrochemicals, we had anti-surge controllers for compressors, and the software was rather complex.

Anyway, I notice that the AmD and MTM maps have initial overboost of about 1.5 bar, dropping through 1.4 to about 1.3, yet the Revo one holds at 1.5 bar. Clearly AmD and MTM share the same engineering approach and Revo has another...

[PhilT]

the top graph you see is the revs and changing of gears on the top speed straight the peaks are in 3rd 4th 5th 6th gears the drop off at the end is engine braking/brakes against engine revs the bottom graph shows exactly what boost at what revs

True

mtm i believe runs lowest boost but peaks at higher revs showing that 6550rpm in 6th =177mph do you agree phil?

The MTM code seems to spike the turbos to get them spun up quicker, then levels off. Not sure why your graph is rougher than John's (Was it something to do with you easing your foot off the pedal during the run?). Hitting just over 6500 rpm, not sure of the speed conversion for 6th.

[DuncS3]

How can I read those charts, for example to see 1.5 bar? Please help thick bar stewards like me...

help


Dunc [img]images/graemlins/s3addict.gif[/img]

[s2driver]

2500 milibars absolute pressure = 1500ish millibar guage (due to atmospheric pressure of 1000 milibar) = 1.5 bar guage. It is just a ddifferent reference for zero bar(atmospheric pressure or hard vacuum)

Lee

[Andiroo]

The bar reading always includes atmospheric mate, therefore take 1.0bar from the reading and you will get the right figure [img]images/graemlins/wink.gif[/img]

Andiroo

[PhilT]

So take the reading on the left hand column, say 2500.

(2500-1000)/1000 = 1.5 bar