I'm just curious, because i get asked this a whole lot.... what makes all the N/A folk out there decide on a certain amount of boost they want to run. There's always someone asking "what do i have to do to run 15psi." I mean they have no clue how 4psi feels, 8 psi, let alone 12-15 psi u know. Where do people get these numbers from? Boost should be a progressive thing. Its good to know what your motor can run, but why go through all the trouble of planning to build your motor for 15psi of boost, if you arent even turbo'd at 8psi yet?
What's better is when this is done without regard to the compression ratio or other compromises you have to make to run obscene boost, or without consideration as to what is streetable.. or that boost isn't the only equation in making power. Oh well, some people (must) have a lot more money than me.
If you can get low amounts of boost stable on stock compression, that's the best of both worlds IMHO. The JRSC people seem to be holding up pretty well.. if nobody does their ride in, I might try that this summer.
Originally posted by 98turboSH but why go through all the trouble of planning to build your motor for 15psi of boost, if you arent even turbo'd at 8psi yet?
Marc
Because people need to build the motor for the MAXIMUM amount of boost they will handle, not the MINIMUM. Eventually people do plan to boost from 8 to 15 PSI. Besides people that do it that way are doing it the right way (IMO). You give yourself an ultimate goal and you work towards it. You dont give yourself progressively bigger steps, cause in the long run taking small steps could cost you more money, and more car downtime.
It depends on the timeframe too I guess If you plan to only boost 7 PSI at first then raise it too 15 PSI within a matter of weeks/months than its ok. It might also have to do with the fact that people are breaking in their new internals (if they built the block), or maybe they are just paranoid like that.
__________________ Blue
-1989 Ford Probe GT (stock, POS) **SOLD**
-1999 EBP Civic SI (modded) **SOLD**
-2001 EBP Prelude Base (almost stock) **SOLD**
-1993 VR RX-7 R1 (modded, 280 RWHP) **RIP**
-1991 Red CRX DX (built 1.9L B18C, SC61 turbo- in the works)
-1990 White CRX DX (stock, Bronze VX rims)
Every man has his own destiny: the only imperative is to follow it, to accept it, no matter where it leads him. -- Henry Miller
Because people need to build the motor for the MAXIMUM amount of boost they will handle, not the MINIMUM. Eventually people do plan to boost from 8 to 15 PSI. Besides people that do it that way are doing it the right way (IMO). You give yourself an ultimate goal and you work towards it. You dont give yourself progressively bigger steps, cause in the long run taking small steps could cost you more money, and more car downtime.
It depends on the timeframe too I guess If you plan to only boost 7 PSI at first then raise it too 15 PSI within a matter of weeks/months than its ok. It might also have to do with the fact that people are breaking in their new internals (if they built the block), or maybe they are just paranoid like that.
You missed the point completely. You set your goal at a pre-determined amount of power or quarter mile time, NOT boost. Remember, the people asking about what they need to do to run X amount of boost have never experienced any kind of boost what-so-ever. They just hear talk about it, but do not truly know the difference between 8psi and 15 psi. I mean its power that makes a car fast, boost is just pressure, and if you can make more power at lower boost pressures, even better. I'm simply saying, set your goal at hp, torque, or quarter mile times, and NOT boost numbers.
Originally posted by 98turboSH You missed the point completely. You set your goal at a pre-determined amount of power or quarter mile time, NOT boost.
well If you think about it POWER and BOOST are interchangeable.
What determines how much power you want? boost
or if you look if it from the flip-side,
What determines how much boost you want? power
For example, you start with the question "how much boost" do I need to run 300 HP? the answer, we'll say 12 PSI.
ok now the next question would be what do I need for my engine to run 12 PSI? the answer? a whole mess of stuff.
When I first tried selecting a turbo I used boost to determine the turbo size, afterwards I figure out about how much HP that would get me. Selecting a specific Compressor/Turbine trim for my engine requires several things.
but like I said you have to know what boost to get what HP and vice versa.
Quote:
Originally posted by 98turboSH Remember, the people asking about what they need to do to run X amount of boost have never experienced any kind of boost what-so-ever. They just hear talk about it, but do not truly know the difference between 8psi and 15 psi.
well a newbies got to start somewhere, somehow, right?
Quote:
Originally posted by 98turboSH I mean its power that makes a car fast, boost is just pressure, and if you can make more power at lower boost pressures, even better.
Unless someone made a big mistake less boost pressure should not be a faster car. maybe it can be "quicker" but not faster.
like I said you use boost to determine compressor and turbine size. And your PSI is based on how much HP you want to have. I dont think there is an exact way to calculate how much XX PSI will be in HP, There are too many other factors involved that could change you numbers in the end. The only other way to find out how much XX PSI give you in HP is to ask around, but then again you have to consider that persons setup. It wont be exactly like yours, so again there will be those "other factors" that could give you different HP numbers.
For anybody that cares here is how I do it, It may not be right but its how I do it.
How BlueShadow translates Horsepower into Boost Pressure
H22 = peak power of 200 HP @ 7000 RPM
MY GOAL IS 350 HP
BASIC CFM = 260 CFM or 18.30 LB/MIN
200 HP = 260 CFM or 18.30 LB/MIN
350 / 200 = 1.75
1.75 * 260 = 455 CFM or 32 LB/MIN
I have an Excel Spreadsheet that I plug different PSI numbers into until 455 CFM pops up in one of the cells. for 455 I came up with roughly 11.3 PSI.
So Unless I'm way off (and I probably am) 11-12 PSI will give me about 350 flywheel HP. You'll get more or less depending on your DP and exhaust system. If there is anyone out there that is running 11-12 PSI on a Lude VTEC, can you tell me your HP numbers?
Quote:
Originally posted by 98turboSH I'm simply saying, set your goal at hp, torque, or quarter mile times, and NOT boost numbers.
Marc
like I said you need to know what HP to know what PSI to run and vice versa, so you really have to use all those things you mentioned. But in the end you'll need to use boost pressure to properly select a compressor/turbine for your car. And you use you HP goal to chose what injector size you'll have to use.
the HP is what you have to build your block for, and the 1/4 mile time is hopefully going to be low enough to make you happy.
Unless you're a die-hard drag racer, I think that anybody would be happy when going from a NA car to a boosted car.
__________________ Blue
-1989 Ford Probe GT (stock, POS) **SOLD**
-1999 EBP Civic SI (modded) **SOLD**
-2001 EBP Prelude Base (almost stock) **SOLD**
-1993 VR RX-7 R1 (modded, 280 RWHP) **RIP**
-1991 Red CRX DX (built 1.9L B18C, SC61 turbo- in the works)
-1990 White CRX DX (stock, Bronze VX rims)
Every man has his own destiny: the only imperative is to follow it, to accept it, no matter where it leads him. -- Henry Miller
Originally posted by BlueShadow just curious 98TurboSH,
What did you do when you decided to do turbo? like how did you do it? what were your goals?
be honest now
Well, my previous car was a 95 Tbird, 4.6L V8 with an AED (eaton) supercharger. It only ran between 6-8pounds, like most eaton's are setup for. When i got smoked by my friends hatchback with "just a 4 cylinder" i realized that honda's have potential. He had a B18c1 (GSR) with a 75 shot in a 91 hatch. I said "i dont care how much nos you wanna use, i'll still beat you" and he won. My car was running a consistent 14.0, 14.1, 14.2 in the quarter (automatic=consistency), and that was smoking quite a few Z28s, so my car was fast, and yet i lost to a 4 banger. So i joined up with the import scene, since most of my friends were already in GS-Ts and hondas. Bought a prelude, nice little high 15 second car, and my goal was to go turbo. I got an amazing deal on a custom setup, so i went with it. I never based my plans on a predetermined amount of boost or even power, i simply knew i wanted to be fast, and faster than i was before meaing 13s. I went turbo, it was poorly tuned, and it was setup for 8psi. I was thinking, well...... lets just turn this up a little bit more, cuz its still not fast enough, and i blew my motor on 11psi within 2 weeks. If i had spent the time paying attention to all the signs I would've known to not trust a fabricator that builds amazing manifolds to tune my car. Well, long story short, engine is built, bigger turbo now, SpeedPro and tuning solely by Harvey (and most of my wrenchwork now too), custom Direct port nos, (drilled into the manifold, not the butterfly plate holley offers), and many other things. So, thats my story.
quote--"Unless someone made a big mistake less boost pressure should not be a faster car. maybe it can be "quicker" but not faster."
I dont really mean anything negative by it when i made the post, but i do get emails quite often (which i will still gladly answer), asking me what to do to run 12psi, 15psi, sometimes i've been asked 20psi. I saw how much i've spent on my motor to make it able to handle as high as 20 psi, and i dont think just anyone can come close to affording it, thats why i try and try to get the point across, !!!!!!8psi of incredibly well tuned boost is much better than 11psi of poorly tuned boost!!!!!!!
Your chances of blowing the motor are greater, and the car will not necessarily be faster. If your car is well tuned, and you have 8psi coming on at 3200 continuing up to 7200, the fuel maps and ignition timing is all smooth and perfect, and you're getting nice cool air into the motor, not 150 degree air or anything, then yes, 8psi can be much better than 11psi. Think about it, 8psi with standalone, a good intercooler, and the perfect setup..... or 11psi running from an FMU that runs the motor way rich when vtec kicks in..... which will be faster.
Originally posted by 98turboSH I dont really mean anything negative by it when i made the post, but i do get emails quite often (which i will still gladly answer), asking me what to do to run 12psi, 15psi, sometimes i've been asked 20psi. I saw how much i've spent on my motor to make it able to handle as high as 20 psi, and i dont think just anyone can come close to affording it, thats why i try and try to get the point across, !!!!!!8psi of incredibly well tuned boost is much better than 11psi of poorly tuned boost!!!!!!!
well if you know one number you can easily guesstimate the other.
example:
15 PSI = approximately 340 HP @ wheels
or
280 wheel HP = approximately 9.5 PSI
I just picked a PSI and HP and did the math just now, and it only took me about 3 minutes for both. Then of course you select you turbo, and build every thing else around the car, turbo and HP #'s.
Quote:
Originally posted by 98turboSH Your chances of blowing the motor are greater, and the car will not necessarily be faster. If your car is well tuned, and you have 8psi coming on at 3200 continuing up to 7200, the fuel maps and ignition timing is all smooth and perfect, and you're getting nice cool air into the motor, not 150 degree air or anything, then yes, 8psi can be much better than 11psi. Think about it, 8psi with standalone, a good intercooler, and the perfect setup..... or 11psi running from an FMU that runs the motor way rich when vtec kicks in..... which will be faster.
Marc
I agree with you on all that stuff, I think that the reason people ask what they need for XX PSI, is cause I guess your HP and 1/4 times will not be what you expected them to be. You cant shoot for say 300 HP in a Lude and get 300 HP out of a turbo setup, there are to many variables that could throw your numbers off.
Like I always say (and do), find a HP goal, translate that into how much PSI you'll need and select the IDEAL compressor and turbine trims based on the PSI. That only applies to the DIY'ers, for the people that dont know how to DIY they should ask both "what PSI do I need to run XXX HP?"
You'll have different power outputs at 8 PSI and 15 PSI no doubt, but to select the most efficient Turbo you need to know what boost pressure you'll run. I only say that though cause I get real technical when it comes to selecting turbos, cause its a turbo concept that I was able to grasp in a matter of hours. That and I need to do something in my spare time.
here is how I see everything else that goes along with a Turbo:
Internals
You either build your block or you dont, 8 PSI and less you dont, 9 PSI and above you do. Thats the rule I go by, everyone has something different, but this is mine.
Fuel Management
This is up to the owner, a lot of factors go into how and what he selects for this. everybody needs to do their own research on this though, cause like you said 8 PSI of good tuning can be better han 11 PSI of poor tuning.
__________________ Blue
-1989 Ford Probe GT (stock, POS) **SOLD**
-1999 EBP Civic SI (modded) **SOLD**
-2001 EBP Prelude Base (almost stock) **SOLD**
-1993 VR RX-7 R1 (modded, 280 RWHP) **RIP**
-1991 Red CRX DX (built 1.9L B18C, SC61 turbo- in the works)
-1990 White CRX DX (stock, Bronze VX rims)
Every man has his own destiny: the only imperative is to follow it, to accept it, no matter where it leads him. -- Henry Miller
well if you know one number you can easily guesstimate the other.
example:
15 PSI = approximately 340 HP @ wheels
or
280 wheel HP = approximately 9.5 PSI
I just picked a PSI and HP and did the math just now, and it only took me about 3 minutes for both. Then of course you select you turbo, and build every thing else around the car, turbo and HP #'s.
I agree with you on all that stuff, I think that the reason people ask what they need for XX PSI, is cause I guess your HP and 1/4 times will not be what you expected them to be. You cant shoot for say 300 HP in a Lude and get 300 HP out of a turbo setup, there are to many variables that could throw your numbers off.
Like I always say (and do), find a HP goal, translate that into how much PSI you'll need and select the IDEAL compressor and turbine trims based on the PSI. That only applies to the DIY'ers, for the people that dont know how to DIY they should ask both "what PSI do I need to run XXX HP?"
You'll have different power outputs at 8 PSI and 15 PSI no doubt, but to select the most efficient Turbo you need to know what boost pressure you'll run. I only say that though cause I get real technical when it comes to selecting turbos, cause its a turbo concept that I was able to grasp in a matter of hours. That and I need to do something in my spare time.
here is how I see everything else that goes along with a Turbo:
Internals
You either build your block or you dont, 8 PSI and less you dont, 9 PSI and above you do. Thats the rule I go by, everyone has something different, but this is mine.
Fuel Management
This is up to the owner, a lot of factors go into how and what he selects for this. everybody needs to do their own research on this though, cause like you said 8 PSI of good tuning can be better han 11 PSI of poor tuning.
Your hp figures sound a little high for that amount of boost. I'd kinda like to know what calculations you do to obtain those numbers, and what factors are included in the equation. Based on psi, 9.5psi making 280 at the wheels (350 at the crank) sounds a little optimistic, and those are numbers that i think could only be obtained with very precise tuning, most likely on race gas with a standalone ecu. No amount of tuning from strictly an FMU and FPR could net those numbers. Also, i dont recall what size the stock injectors are.... but i dont think they are large enough to raise hp 75% over stock. Thus.... a standalone ecu is required, or at least a well tuned v-afc. With this said, i still go back to my original statement that you should stick to 8psi of boost on the stock motor, and go standalone ecu with everything well tuned before you start concerning yourself with the needs to run 15psi. Chances are, 8psi of well tuned boost will be more than enough power. The only reason to consider more than 8psi and building your motor is if you are track racing and you need a better time for whatever reason, or you blew your motor and you dont want to blow it again.
My closing statement..... with your numbers 15 psi is worth 340 at the wheels, thus 20% drivetrain loss is 425hp at the crank. People who are wanting more from their 15 second prelude with i/h/e, asking how to run 12-15psi dont realize just how much 425 hp on a fwd 4banger. Just to point out, Corvettes are rated at 350hp.... so why do people want so much when they're running so little? That is still my question i'm sticking with... If you're n/a and have never been in a 12 second car on the street... dont worry yourself with running 15 psi.... worry yourself with how much power you can make at 8psi. Trust me, you can spend more than enough money on just the motor without trying to build it and spend thousands more. Everyone who wants to go fast should go stand-alone and turbo @8psi first.... build motor second if that is still not enough. Personally, i think most people dont realize how satisfied they can be with "only" 8psi.
Your hp figures sound a little high for that amount of boost. I'd kinda like to know what calculations you do to obtain those numbers, and what factors are included in the equation. Based on psi, 9.5psi making 280 at the wheels (350 at the crank) sounds a little optimistic, and those are numbers that i think could only be obtained with very precise tuning, most likely on race gas with a standalone ecu. No amount of tuning from strictly an FMU and FPR could net those numbers. Also, i dont recall what size the stock injectors are.... but i dont think they are large enough to raise hp 75% over stock. Thus.... a standalone ecu is required, or at least a well tuned v-afc. With this said, i still go back to my original statement that you should stick to 8psi of boost on the stock motor, and go standalone ecu with everything well tuned before you start concerning yourself with the needs to run 15psi. Chances are, 8psi of well tuned boost will be more than enough power. The only reason to consider more than 8psi and building your motor is if you are track racing and you need a better time for whatever reason, or you blew your motor and you dont want to blow it again.
My closing statement..... with your numbers 15 psi is worth 340 at the wheels, thus 20% drivetrain loss is 425hp at the crank. People who are wanting more from their 15 second prelude with i/h/e, asking how to run 12-15psi dont realize just how much 425 hp on a fwd 4banger. Just to point out, Corvettes are rated at 350hp.... so why do people want so much when they're running so little? That is still my question i'm sticking with... If you're n/a and have never been in a 12 second car on the street... dont worry yourself with running 15 psi.... worry yourself with how much power you can make at 8psi. Trust me, you can spend more than enough money on just the motor without trying to build it and spend thousands more. Everyone who wants to go fast should go stand-alone and turbo @8psi first.... build motor second if that is still not enough. Personally, i think most people dont realize how satisfied they can be with "only" 8psi.
Marc
Well those numbers were "guesstimates" so they might be off by a little (or a lot ). The way I guesstimate HP to PSI and vice versa is on one of my previous posts on this thread. I just assume that 200 HP = 260 CFM, when I raie one of those numbers I raise the other one by the same factor.
I know its not accurate, but if anyone has a better idea I'm open to ideas.
__________________ Blue
-1989 Ford Probe GT (stock, POS) **SOLD**
-1999 EBP Civic SI (modded) **SOLD**
-2001 EBP Prelude Base (almost stock) **SOLD**
-1993 VR RX-7 R1 (modded, 280 RWHP) **RIP**
-1991 Red CRX DX (built 1.9L B18C, SC61 turbo- in the works)
-1990 White CRX DX (stock, Bronze VX rims)
Every man has his own destiny: the only imperative is to follow it, to accept it, no matter where it leads him. -- Henry Miller
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