How much is 1psi equal to in terms of power?
How much is 1psi equal to in terms of power? lets say its 8:5/1 or 9:1 with a 408 ls1.
how much boost(psi) would it take to make close to 700 rwhp, and is it possible to keep it as a daily driver(meaing i can drive it whenever on pump gas). i want to make as much power on 91 oct(its the only stuff we have here) and im not sure what i should expect when its being put together.
the turbo will be a gt55 turbo.
how much boost(psi) would it take to make close to 700 rwhp, and is it possible to keep it as a daily driver(meaing i can drive it whenever on pump gas). i want to make as much power on 91 oct(its the only stuff we have here) and im not sure what i should expect when its being put together.
the turbo will be a gt55 turbo.
TECH Senior Member
Joined: Apr 2004
Posts: 6,157
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From: Texas
Good question. This is the setup I plan on getting in my "daily driver" Ill be on 93 octane and a bigger turbo. Does anyone know the answer to this? Or is it one of those questions that cant be answered?
i just got my 408 put in last night, stock 6.0 heads and a nice sized cam. it is an 8.5-1 motor and i am seeing 60lb's of air at 8psi. from past experience that is 500rwhp thru a 4l80e and tcase. this is on it's first day out on pump gas. i think 550+rwhp on pump gas is likly and ~700rwhp on good gas. stock heads are probably holding me back a little as is the single 3" down pipe. with a t76 is spools instantly and is a torque monster out of the hole.
this is a very, very rough calculation, but 1 atmosphere = 14.7 psi. so if you're NA power is 500, it wold take ~5.88 psi. simple math, double the atmosphere and you double the power.
This is an almost impossible calculation.. Understand that the more psi or power your motor puts down, it incrementally as you raise PSI and RWHP, the effective RWHP per psi gets lower and lower..
A Motor is very responsive to say 4 to 5 psi of boost. A Gain of 125RWHP for a mere 4psi is not unheard of. But a Gain of 250RWHP on a 8psi blown motor, is much harder to achieve. Efficiency comes into a major role, as some kits are more efficient than others. Cam, Heads, Exhaust all play a role. Good example. My car put down 524RWHP with a Bone stock motor, 7psi of boost 3.73 12bolt.. Before the blower I dynoed 328RWHP on the same setup minus the blower. That's a gain of 28RWHP per 1 psi of Boost. Later I dynoed gain with 11psi of boost with a lower compression motor, (which lost efficiency) but should have gained it back with my cam, even though it's a 112LSA, and my stage 1 heads. All other factors stayed the same. My now 11psi motor had 621RWHP. That’s now 26.6 RWHP per 1 psi of boost. So using my car as an example, my RWHP per 1 psi of boost has gone down , even though I have better heads, and a decent cam for the blower.
I'm sure others will chime in.
Clint
A Motor is very responsive to say 4 to 5 psi of boost. A Gain of 125RWHP for a mere 4psi is not unheard of. But a Gain of 250RWHP on a 8psi blown motor, is much harder to achieve. Efficiency comes into a major role, as some kits are more efficient than others. Cam, Heads, Exhaust all play a role. Good example. My car put down 524RWHP with a Bone stock motor, 7psi of boost 3.73 12bolt.. Before the blower I dynoed 328RWHP on the same setup minus the blower. That's a gain of 28RWHP per 1 psi of Boost. Later I dynoed gain with 11psi of boost with a lower compression motor, (which lost efficiency) but should have gained it back with my cam, even though it's a 112LSA, and my stage 1 heads. All other factors stayed the same. My now 11psi motor had 621RWHP. That’s now 26.6 RWHP per 1 psi of boost. So using my car as an example, my RWHP per 1 psi of boost has gone down , even though I have better heads, and a decent cam for the blower.
I'm sure others will chime in.
Clint
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12 Second Club
Joined: May 2004
Posts: 52
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From: Georgia
Originally Posted by HUGGER ORANGE SS
Remember Boost is just back pressure. The fact Efficiency come into play has to do with heat coming from the compressor...
Clint
Clint
either way, i think we will both agree that there are way too many variables to accurately say 1 psi = XX amount of hp/tq.
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Originally Posted by ChrisJ
Doesnt the size of the compressor also effect how much power per psi? I would think something like a 101mm would make more power per psi then say a 66mm.
The bigger the compressor wheel...the longer it will take to spool...the 101mm would flow alot more air, but the RPM range also moved up alot. When choosing a turbo, you have to look at the efficiency range, most big turbo's are not efficient unless they are making 15+ psi of boost. The best al around turbo for single turbo set-ups seems to be the T76.
Hugger....your motor lost hp per psi, but is now alot safer, since the compression dropped.
I did a thread about this and posted alot of results just to get an idea on how different setups react in rwhp per psi. Check the thread here. My car gained 21rwhp per psi. https://ls1tech.com/forums/forced-induction/137685-efficiency-fi-setups-out-there-ii-final-results.html
When i have free time on my hand i will do a new list and include the FI kits results in.
When i have free time on my hand i will do a new list and include the FI kits results in.
12 Second Club
Joined: May 2004
Posts: 52
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From: Georgia
Originally Posted by chevysrule94
The bigger the compressor wheel...the longer it will take to spool...the 101mm would flow alot more air, but the RPM range also moved up alot. When choosing a turbo, you have to look at the efficiency range, most big turbo's are not efficient unless they are making 15+ psi of boost. The best al around turbo for single turbo set-ups seems to be the T76.
Hugger....your motor lost hp per psi, but is now alot safer, since the compression dropped.
Hugger....your motor lost hp per psi, but is now alot safer, since the compression dropped.
As for 76mm being the best turbo.... Id say that depends on your goals, CI of your motor, etc etc. Everybody has different expectations
ok, next question. i guess it all depends on where your motor starts from, but is it possible to have 0 psi on a turbo motor, assuming the setup is working correctly? if thats the case, im sure they can do some tests per psi to show gains. that might be kind of cool to see.
I would say atleast 13psi to do it. On a 370CID motor and a procharger, we hit 687 RWHP and that was Maxing out the MAF too. So with a turbo there is less power lose because of the charger. So I would say 13 psi should be a good goal.
12 Second Club
Joined: May 2004
Posts: 52
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From: Georgia
if thats possible (i dont think it is), it will still be different from setup to setup... seriously, there are too many variables. One turbo will make different power at different boost levels than the next, and even with the same turbo on a different motor, it will still be different. Way too many variables to accurately say. Plus, boost doesnt build power in an even amount.. It can add 10 hp for 1 psi and then 17 more for the next, 26 more for the next (just throwing out random numbers, thats not from any particular setup).. From my experience,boost/power curves are not linear.
This is very true. You cant ever just add up numbers and hope for it. But if I were to take the same vehicle we did and make it turbo, there would be an easy 100 more hp in it just because the charger is robbing power. Also, the cam profile will help alot and how the heads are done too.
Rick
Rick
well this is my basic setup:
fully built 408 motor by FMS
stage 3 hand ported afr heads by meaux
prob somewhere around a 232/232 cam, im thinking
12 bolt with no higher then 3 73's, prob just 3 42's though
gt55 turbo, by garrett(i havent seen any specs released on it yet though)
my goal is to make as much power on 91 oct. as possible, that is my real question.
what would be your guesses i can make as far as boost and power goes?
fully built 408 motor by FMS
stage 3 hand ported afr heads by meaux
prob somewhere around a 232/232 cam, im thinking
12 bolt with no higher then 3 73's, prob just 3 42's though
gt55 turbo, by garrett(i havent seen any specs released on it yet though)
my goal is to make as much power on 91 oct. as possible, that is my real question.
what would be your guesses i can make as far as boost and power goes?
Lot of variables not being taken into account here.
Let's go with the ultimate dyno queen combo:
M6
stock rearend
open exhaust
good fmic (i question whether an obx is big enuff)
I will say 12 to 15psi for you to hit 700rwhp.
Variables that affect the amount of boost needed:
-engine compression
-turbo size
-down pipe/exhaust housing
A lower compression setup like 8:1 will need more boost to hit the same number as say a 9:1 setup, but your bigger concern should be about detonating on 91 pump gas. I would not get greedy with compression.
My combo is the worst dyno combo you can imagine as a comparo:
YSi supercharger
T400 trans, 4500 non lock up yank converter
9", 28" slicks
dual exhaust, 3", dual magnaflows dumped
Griffin FMIC (good thing)
I've done 746rwhp w/17 psi, 13:1 AF, 22 degrees of timing, 110Leaded
I've done 738rwhp w/19 psi, 11:1 AF, 23 degrees of timing, 110Leaded
(but have picked up 50rwhp under the curve and it's not as peaky, and it peaked at 6200 vs 6800 like last time)
My motor has recently seen 21psi but my combo was dropping off well before 6500 rpms.
I think any 9:1, FMIC combo can hit 650rwhp on pump gas 93. I think that 700rwhp is possible especially if it's a really peaky combo. But 9:1 won't leave you much room for safety. Running the car on the dyno for 3 seconds is not the same as running the car WOT for a few minutes racing a dude in a Viper. Think about my last comment and explain to me what the different is.
Let's go with the ultimate dyno queen combo:
M6
stock rearend
open exhaust
good fmic (i question whether an obx is big enuff)
I will say 12 to 15psi for you to hit 700rwhp.
Variables that affect the amount of boost needed:
-engine compression
-turbo size
-down pipe/exhaust housing
A lower compression setup like 8:1 will need more boost to hit the same number as say a 9:1 setup, but your bigger concern should be about detonating on 91 pump gas. I would not get greedy with compression.
My combo is the worst dyno combo you can imagine as a comparo:
YSi supercharger
T400 trans, 4500 non lock up yank converter
9", 28" slicks
dual exhaust, 3", dual magnaflows dumped
Griffin FMIC (good thing)
I've done 746rwhp w/17 psi, 13:1 AF, 22 degrees of timing, 110Leaded
I've done 738rwhp w/19 psi, 11:1 AF, 23 degrees of timing, 110Leaded
(but have picked up 50rwhp under the curve and it's not as peaky, and it peaked at 6200 vs 6800 like last time)
My motor has recently seen 21psi but my combo was dropping off well before 6500 rpms.
I think any 9:1, FMIC combo can hit 650rwhp on pump gas 93. I think that 700rwhp is possible especially if it's a really peaky combo. But 9:1 won't leave you much room for safety. Running the car on the dyno for 3 seconds is not the same as running the car WOT for a few minutes racing a dude in a Viper. Think about my last comment and explain to me what the different is.
A veteran racer said to me earlier this year that in general any combo, assuming same block, heads, but maybe using a lot more or a lot less cubes, and using intercooling, will tend to max out pump gas at 650-700rwhp. If you look at all the combos out there, it's very hard to find any engine that makes 800rwhp in a car. I've been dynoing with 110 leaded and my target has always been like 14-15:1 total compression with the blower. Look at VP's website and how they rate fuels like C12 and C16. I guess my point is that at 700rwhp, you are right at that edge of what pump gas can do.
Staging Lane
Joined: Oct 2004
Posts: 96
Likes: 0
I could drive my car daily and it makes close to 700rwhp on pump gas! The last dyno numbers on the car were in horribly hot and humid weather so I figure right now in good weather it would do around 685 to the wheels.