940 turbo wastegate pressures

[RollingThunder]

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

[bluebrickrick]

Is it a like for like comparison or is there an exhaust backpressure component missing which may not be the same between models ?

I'm more comfortable with steam, it generally happens slower but these days not always slowly enough ;)

Regardless, a very interesting bit of research !

[RollingThunder]

No, the exhaust, cat etc is common to all Turbo variants, about 2.25in dia. Same downpipe, plus of course same engine inc turbo, injectors etc. ECUs have minor ignition/fuel map differences AFAIK.

The TurboPlus kit ups the output to circa 190bhp by increasing the boost to 13psi (0.9 bar) temporarily which adds 25bhp - but only activates at wide open throttle.

[barkster1971]

15g

Or just put a 15g in and run that at 12psi:thumbs_up:. The Sport edition should have had a 15g and V cam, 200 bhp and done away with the turbo + that never worked well.

[RollingThunder]

Agreed, but Volvo was running down the 940 production - the 'youthful' new FWD 850 was supposed to be the 'fun to drive, sprightly' car, replacing the outdated RWD 900s... so they couldn't have one of the old battleships out dragging the new comer could they :D

[barkster1971]

when

They weren't running out of 940's when the sport came out, they were replacing the 850 with the s70/v70 then. But then again why do a sport model in estate only?! What they lacked was a tuning division like Polestar now.
My point is a slightly bigger turbo ( as an option ) instead of the turbo+ option would have worked better.

[Dirty Rooster]

I think the Turbo+ was a clever device to make it 'sporty' but prevent hooligans like Barkster from overstressing the engine due to its clever time limit at max boost.

[loki_the_glt]

I still think that a supercharger is a better bet for road use: the response is almost immediate and it comes in at idle.
After all, how often do you get the chance to drive flat out in this country, as opposed to wanting (needing?) some more low-rev/mid-range lift?
Plus you don't have to let the engine idle for a couple of minutes after use...

[TonyS9]

Good to get the specs finally.

Running a bigger turbo at the standard pressure will not add anything atall. It won't be more efficient at the 165bhp level, you will just get more lag.

[barkster1971]

utter bollocks

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

[360beast]

I still think that a supercharger is a better bet for road use: the response is almost immediate and it comes in at idle.
After all, how often do you get the chance to drive flat out in this country, as opposed to wanting (needing?) some more low-rev/mid-range lift?
Plus you don't have to let the engine idle for a couple of minutes after use...

Have you seen mighty car mods on YouTube? They got 2 mx5's and turbocharged one and supercharged the other. From a standstill the supercharged one was in front but only for a short time something like in to 2nd gear but after that the turbo blew it away and they ran the same psi IIRC with near identical maps. So when you do want to give it the beans a turbo will be better, however for day to day use and usability on the UK roads yes a supercharger would make more sense.

[baggy798]

[youtube]sKLF_qcwyg0[/youtube]

[TonyS9]

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

10 psi is not standard, 7.4psi is standard. For air flow this couldn't be any simpler it will absolutely not flow more for the same pressure. Air flow is dependant on the stuff after the turbo and the pressure in the inlet. Bigger turbos are just more efficient for bigger flows (bigger bhp), meaning a little less heat and probably a stronger turbo.

There is a discussion about heat, air mass and so on, but if you think that air flow is more because the CSA is bigger you are completely wrong. I think that for the same pressure the 13c will be more efficient for 170bhp, do correct me if you know otherwise. The 15g should then in theory be hotter and therefore less bhp but we are talking very small differences, I doubt it is measurable.

I can't access the links

[bluebrickrick]

How? the backpressure develops opposing that pressure regardless of the capacity of the blower, while it will deliver more volume to open air I cannot see how it crams any more through at the same pressure than the smaller unit, the pressure equates to voltage the volume to amperage in electrical circuit terms the back pressure is the resistance surely ?

If you could put more air through at that pressure the smaller turbo would show a drop in boost when flat out ?

As far as I can see it all the bigger turbo will be doing is generating more heat due to churning all that air it can't get rid of which will increase exhaust backpressure too which may impair scavenging.

That is why I asked the question to the original posting (although that was primarily about exhaust backpressure).

Always found thermodynamics fascinating if at times confusing but default to 'Marshes Laws' - (a Norfolk teachers delivery of the Laws of Thermodynamics designed to assist remembering and thinking about them)

You can't win
You can't loose
You can't get out of the game

Rick :)

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

[barkster1971]

what?

Put the pipe down. You're too high. Step away from the Volvo and get in the Micra.