940 turbo wastegate pressures

[bluebrickrick]

High ? how so ?? true the pipe is currently loaded with something entirely legal despite looking like sliced tow-rope, which I never smoke in bed, as for a Micra, I suspect it would require a large liquidiser and a funnel to get me into one of those :)

Rick

[aardvarkash10]

Course it will. A 15g at 10psi flows more air than a 13c at 10psi.

http://www.stealth316.com/images/te04h-13c11-raw.gif

http://www.stealth316.com/images/td04-15g-raw.gif

Yes it will, although I subject that to the proviso that "more" refers to both volume AND mass. However, this comparison assumes different downstream conditions. On a like-for-like basis, 10psi will flow exactly the same volume of air through an engine regardless of how that 10psi is produced.

The mass of air is a different story and temperature sensitve as noted above. But for real-world measures, disregard that (unless you are going mental-level boost).

[960kg]

I came across this page in a Volvo document I was browsing through a few days ago (Pocket Data Booklet - Cars - 700, 850, 900, 1991-1997). It seems to indicate the official values for the wastegate opening pressures - something that I've been unable to find previously. As there are various values quoted on the web I thought I'd share it with you.



I've converted the kPa values to PSI using an online tool, which gives us:

B230FT/GT 7.4psi (165bhp)
B230FK/GK 4.5psi (135bhp)
B200FT/GT 8.1psi (155bhp)

... which is quite different to most of the values generally quoted lol.





So I decided to play with some maths - what would a B230FK make with a B200FT wastegate ;)

The difference between a B230FT and a B230FK is 30bhp and 2.9psi, so approx 10bhp per 1 psi.

Wastegate opening pressure difference between B230FT & FK is 8.1psi - 4.5psi = 3.6psi, so approx an extra 36bhp? Call it a 35bhp improvement. So 135 + 35 = 170bhp :) very approximately lol

Hope this is of interest. I can see a sudden demand for B200FT wastegates :D

Your chart is correct as i had the 1991 940 Wentworth 2litre Turbo and the pressure was 8.1psi as std.

General rule of thumb is for every 1psi you get 8bhp according to the Turbobricks site.......http://www.turbobricks.com/

You can only set the wastegate actuator to via an MBC to 13 to 14 psi as the fuel cut comes in between 14 and 15psi to safeguard the engine!

If you set it to over this the engine will either just suddenly cut or the boost will drop to around 4psi as it senses the fuel cut.

Some say set the MBC to max. but some say don`t but the thing is the extra is there if you want it when set on max. so you may as well get bang for buck...!

I also had the 1989 2.3 turbo which was rated at 185bhp as std. but if you used the MBC on this monster you could only set the MBC to half way otherwise the engine did not like at all.

Also it came with a 20mpg tag ...not good at all.

[TonyS9]

An understanding of basic physics can't argue with years of experience of changing every variable at the same time for 'more'. All this Victorian Steam engineering discovering thermodynamics has no bearing on turbos. ;)

[bluebrickrick]

An understanding of basic physics can't argue with years of experience of changing every variable at the same time for 'more'. All this Victorian Steam engineering discovering thermodynamics has no bearing on turbos. ;)

Glad you appreciate that we are looking at precisely the same rules from differing areas of expertise and experience ;)

[jonnyf90]

I also had the 1989 2.3 turbo which was rated at 185bhp as std. but if you used the MBC on this monster you could only set the MBC to half way otherwise the engine did not like at all.

Also it came with a 20mpg tag ...not good at all.

Love that beast! What was the std pressure for 185bhp?!
And yeah my 940 didn't like having the MBC set to anything more than 14psi. 12 is quite sufficient ;)

[TonyS9]

If you want to increase beyond 14psi you need more charge cooling or less mechanical piston compression. Dynamic boost also allows short bursts of higher pressure until heat soaks in. This is what modern cars use.