horse power per pound of boost
- Thread starter m8matt
- Start date
i heard it was 7-10 depending on setup and tuning
W
Woody1050
New member
Hello, i have dynoed some Apex with MC Express turbo and they gain 10hp per 0.1kg, hope that helps
I thought that more boost was not the same across the board.
Lets say you start with 8 and go to 10...you gain about about 15lbs of boost with that 2 pound addition...
BUT start with 12 and go to 14 and you gain much more like 20 right?
Lets say you start with 8 and go to 10...you gain about about 15lbs of boost with that 2 pound addition...
BUT start with 12 and go to 14 and you gain much more like 20 right?
yeah, i beleive its a semi exponential sorta thing, cant guarantee it, but as pressure increases, the amount of air being moved increases at a slightly higher rate.
M
m8matt
Well-known member
This is more complex than I thought! Some good points made that I would like to know more about. Is there any good reading material on this?
It is not a PSI/pound of boost issue.
It has to do with air volume.
There is a thread burried on here about this. You can have one turbo that is boosting 15 PSI and another turbo that is boosting 8 PSI and the 2nd turbo (8 psi) will be producing more power. Why? Because of a number of reasons:
1. It is more efficent
2. It is moving more air
Turbo A is charging the equivalent of a garden hose with 15 PSI
Turbo B is charging the equivalent of a fire hose with 8 PSI
Lets throw Turbo C into the mix that is boosting 25 PSI in line the size of a Straw.
Which one is moving more air/volume?
It has to do with air volume.
There is a thread burried on here about this. You can have one turbo that is boosting 15 PSI and another turbo that is boosting 8 PSI and the 2nd turbo (8 psi) will be producing more power. Why? Because of a number of reasons:
1. It is more efficent
2. It is moving more air
Turbo A is charging the equivalent of a garden hose with 15 PSI
Turbo B is charging the equivalent of a fire hose with 8 PSI
Lets throw Turbo C into the mix that is boosting 25 PSI in line the size of a Straw.
Which one is moving more air/volume?
B
Boyko
Well-known member
If it is a good kit and everything is sized properly and the over lap between the intake and exhaust cycle is not crazy, a motor that starts out with 150hp stock will make 10hp per pound of boost. A motor that puts out 75hp stock will make a extra 5hp per pound.
Keep in mind that is not all the way across the board, a 150hp motor at 3psi will not make 30 more hp, and at 25psi it will not make 250 more hp. Most kits are designed to run at 8 to 15 psi, that is the sweet spot and everthing in the kit should work together at that power level.
Keep in mind that is not all the way across the board, a 150hp motor at 3psi will not make 30 more hp, and at 25psi it will not make 250 more hp. Most kits are designed to run at 8 to 15 psi, that is the sweet spot and everthing in the kit should work together at that power level.
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HANDSOME
Well-known member
How would you gain 15 lbs of boost going from 8 lbs to 10 lbs ?
Simply not true....
There are so many other factors:
-Timing
-Intake temp (intercooled or not intercooled)
-Fuel (race, pump, combo)
-Turbo Efficiency (has a lot to do with intake temp)
-Turbo size
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flying pig
Well-known member
I thought it had to do with atmospheric pressure. Atmosphereic pressure at sea level is supposed to be 13.5psi or something so I thought in theory 13.5lbs of boost pressure should double your hp. ex. apex turbo 150hp stock 300hp 13.5psi 450hp 27psi?
Well I was just using those numbers for sake of discussion. Someone above asked something like.....if 1 pound of boost gained 10 hp...so thenis adding 2lbs going to make 20 more?
My numbers were just for the sake of choosing easy numbers to make my point. Just because you add a pound doesn't mean you'll gain the same HP each time you add a point of boost. That's all I was trying to say.
It can change with weather but it is typically 14.7 standard barometric pressure.
7,000 feet of elevation it is about 11.3
10,000 feet is 10.1
15,000 8.2 (yes we never deal with this in NA)
30,000 (just for fun, save Everest) 4.37- That is why it is so hard to breath, paired with less oxygen.
So you see you are dropping almost 5 psi from sea level to 10k feet, so a turbo has to make up that boost, but most are capable of that, which is why Turbo's are less effected at elevation than an NA motor.
The pressure you see on a boost guage would be +barometric pressure (14.7 at sea level).
So if you are at sea level and you are boosting 15 psi, you are really boosting 19.7 psi.
Something everyone keep forgetting about is not all turbos are equal. 15 psi in turbo A is not the same as 15 psi in turbo B.
So if you are at sea level and you are boosting 15 psi, you are really boosting 19.7 psi.
Something everyone keep forgetting about is not all turbos are equal. 15 psi in turbo A is not the same as 15 psi in turbo B.
