JapCarForum Cars, Cars, Cars! General Car Maintenance Help me understand something regarding boost...

Help me understand something regarding boost...

Help me understand something regarding boost...

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Tango
Senior Member
314
01-06-2018, 05:32 AM
#11
speedfreek Exactly as I see it Stav.

The pressure is the same from the output of the charger as it is in the chamber as there are wastegates to regulate the pressure to a set max.

The psi guage doesn't measure how much air there is, merely the pressure of the air that is there - so in practice I don't believe that it is a measure of unused boost.

Isn't that what I said earlier??

IS 200 Sport with a few mods, Standardish IS-F. The IS250 SE-L with a few mods has gone to a new home.[SIGPIC][/SIGPIC]
Tango
01-06-2018, 05:32 AM #11

speedfreek Exactly as I see it Stav.

The pressure is the same from the output of the charger as it is in the chamber as there are wastegates to regulate the pressure to a set max.

The psi guage doesn't measure how much air there is, merely the pressure of the air that is there - so in practice I don't believe that it is a measure of unused boost.

Isn't that what I said earlier??


IS 200 Sport with a few mods, Standardish IS-F. The IS250 SE-L with a few mods has gone to a new home.[SIGPIC][/SIGPIC]

FirebirdPhil
Posting Freak
7,101
01-06-2018, 07:46 AM
#12
Tango Isn't that what I said earlier??

yes

"Life's goal is not to arrive safely at the grave in a well preserved body. But, rather to skid in sideways........
totally worn out and broken, shouting 'Holy ****, WHAT A RIDE!'"
FirebirdPhil
01-06-2018, 07:46 AM #12

Tango Isn't that what I said earlier??

yes


"Life's goal is not to arrive safely at the grave in a well preserved body. But, rather to skid in sideways........
totally worn out and broken, shouting 'Holy ****, WHAT A RIDE!'"

Tango
Senior Member
314
01-06-2018, 08:05 AM
#13
Thanks for the confirmation, thought I was posting to myself :laugh:

IS 200 Sport with a few mods, Standardish IS-F. The IS250 SE-L with a few mods has gone to a new home.[SIGPIC][/SIGPIC]
Tango
01-06-2018, 08:05 AM #13

Thanks for the confirmation, thought I was posting to myself :laugh:


IS 200 Sport with a few mods, Standardish IS-F. The IS250 SE-L with a few mods has gone to a new home.[SIGPIC][/SIGPIC]

RichyUK
Member
113
01-06-2018, 09:20 AM
#14
forget the blurb, more boost = more power Smile (and more likely to det)

when i map cars i will genrally make 2 boost settings. last one i did that was fairly powerful made 495 bhp @ 1.5 bar boost and 535 @ 2 bar boost Smile
RichyUK
01-06-2018, 09:20 AM #14

forget the blurb, more boost = more power Smile (and more likely to det)

when i map cars i will genrally make 2 boost settings. last one i did that was fairly powerful made 495 bhp @ 1.5 bar boost and 535 @ 2 bar boost Smile

Rolex
Senior Member
512
01-06-2018, 11:49 AM
#15
I think boost gauges are more to indicate the density of the air being but into the cylinder. Boost cars will always have air that can't make it into the chamber reaction thats the purpose of dump valves to release any built air pressure that can not phsically be put into the engine.
Rolex
01-06-2018, 11:49 AM #15

I think boost gauges are more to indicate the density of the air being but into the cylinder. Boost cars will always have air that can't make it into the chamber reaction thats the purpose of dump valves to release any built air pressure that can not phsically be put into the engine.

RichyUK
Member
113
01-06-2018, 11:47 PM
#16
boost gauge is a measure of the pressure of the air which has been compressed by the turbo/supercharger. The more you compress the air (ie increased psi/bar on your boost gauge), the denser it is, so effectively you've shoved more air in. at 5 psi you'll be putting in 'x' amount of air as its compressed by that much. at 10psi its compressed more so you physically have more air able to go into the same space in the combustion chamber, hence always needing more fuel as boost increases.

dump valves are used to vent of pressure between the charger and the closed throttle body butterly valve. When you are on boost, and shut the throttle completely, the charger is still making boost but has nowhere to go as the butterfly is shut so the dumpvalve opens to vent this pressure and prevent the turbo from stalling. if you have no dump valve you will get the 'chatter' sound when you lift of as all that compressed air in the boost pipework has nowhere to go, so rebounds off the closed butterly & back towards the turbo and the compressor blades then 'chop' the air up into pockets of air causing that chatter sound.
RichyUK
01-06-2018, 11:47 PM #16

boost gauge is a measure of the pressure of the air which has been compressed by the turbo/supercharger. The more you compress the air (ie increased psi/bar on your boost gauge), the denser it is, so effectively you've shoved more air in. at 5 psi you'll be putting in 'x' amount of air as its compressed by that much. at 10psi its compressed more so you physically have more air able to go into the same space in the combustion chamber, hence always needing more fuel as boost increases.

dump valves are used to vent of pressure between the charger and the closed throttle body butterly valve. When you are on boost, and shut the throttle completely, the charger is still making boost but has nowhere to go as the butterfly is shut so the dumpvalve opens to vent this pressure and prevent the turbo from stalling. if you have no dump valve you will get the 'chatter' sound when you lift of as all that compressed air in the boost pipework has nowhere to go, so rebounds off the closed butterly & back towards the turbo and the compressor blades then 'chop' the air up into pockets of air causing that chatter sound.

Tango
Senior Member
314
02-06-2018, 12:48 AM
#17
I think everyone is in violent agreement on this subject:bored:

IS 200 Sport with a few mods, Standardish IS-F. The IS250 SE-L with a few mods has gone to a new home.[SIGPIC][/SIGPIC]
Tango
02-06-2018, 12:48 AM #17

I think everyone is in violent agreement on this subject:bored:


IS 200 Sport with a few mods, Standardish IS-F. The IS250 SE-L with a few mods has gone to a new home.[SIGPIC][/SIGPIC]

RichyUK
Member
113
02-06-2018, 01:28 AM
#18
Tango I think everyone is in violent agreement on this subject:bored:

huh?:glare:

i was just trying to give a nice informative post about what boost is, and what a dump valve is used for.
RichyUK
02-06-2018, 01:28 AM #18

Tango I think everyone is in violent agreement on this subject:bored:

huh?:glare:

i was just trying to give a nice informative post about what boost is, and what a dump valve is used for.

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