big inches or small inches for a turbo setup?
09-09-2005, 08:02 AM
#1
big inches or small inches for a turbo setup? like the title says, i was reading around and seeing that everyone has a iron 408 and then i come along this other thread taht says that a smaller inch motor would be better cuss of it revving up faster and not cousing a backpressure on the log. anyway i was confused on it, i'll find the thread that says that and i'll link it here. thanks for everyones help!
09-09-2005, 08:32 AM
#2
smaller motors can make more HP with the SAME turbocharger due to the fact that the smaller motor can have a higher pressure ratio, thing is though you have to rev it up a bit more to get the needed exhaust gas velocity.
bigger motor can make more power on pump gas
bigger motor makes more power down low if you dont want to rev it super high.
bigger motors will have a flatter torque curve.
its all on the parts you use together with your motor and how you want it to drive, then match the turbo system with the engine.
bigger motor can make more power on pump gas
bigger motor makes more power down low if you dont want to rev it super high.
bigger motors will have a flatter torque curve.
its all on the parts you use together with your motor and how you want it to drive, then match the turbo system with the engine.
09-09-2005, 08:49 AM
#3
so what would you recommend for a street/strip car? iron 408? forged internal 346? 5.2 block? any recommendations? i know tha the iron 408 is the popular of the 3, but is there more options? my goals are to have a motor that i can continue to upgrade to bigger turbo's when i want to go faster. the smaller/larger motor threw a curve ball to my original parts list, so clearing this up is a big help, i know of a few others that got confuised and hopefully this will help all of use. Thanks Hawk 
09-09-2005, 09:13 AM
#4
well how fast do you want to get in th end.
if its a street/strip motor then id go with a 370-403 cubes and do around a 80-88mm turbocharger. with that right there youll be able to run around a low 9 second pass at 3600lbs or so, no upgrading needed, and it will be ok on the street.
and for some reason you want to get into 8's or lower you can upgrade to a bigger turbo, but by that time youll probably have to go threw your engine again to refresh and upgrade all the weak links in there.
if its a street/strip motor then id go with a 370-403 cubes and do around a 80-88mm turbocharger. with that right there youll be able to run around a low 9 second pass at 3600lbs or so, no upgrading needed, and it will be ok on the street.
and for some reason you want to get into 8's or lower you can upgrade to a bigger turbo, but by that time youll probably have to go threw your engine again to refresh and upgrade all the weak links in there.
09-09-2005, 10:15 AM
#5
if both the smaller and larger engine have the same compression ratio, and you are pushing the same boost PSI into them, the larger engine will make more power. With a smaller engine, you can turn the boost up and make more power, but the bigger engine will always have more potential if you do the same thing. The bigger engine will also spool the turbo up more quickly.
09-09-2005, 10:44 AM
#6
ooh, got it then, i was reading this https://ls1tech.com/forums/forced-induction/375093-383-ci-tti-street-kit-good-combo-not.html thread and thats how i got confused, i dont think i'll be goin to the 8's any time soon, i'd be happy being in the 9's with a "street" car 
Thanks for all of ya'lls help!! cleared everything up for me
Thanks for all of ya'lls help!! cleared everything up for me
09-09-2005, 10:53 AM
#7
Originally Posted by Nine Ball
if both the smaller and larger engine have the same compression ratio, and you are pushing the same boost PSI into them, the larger engine will make more power. With a smaller engine, you can turn the boost up and make more power, but the bigger engine will always have more potential if you do the same thing. The bigger engine will also spool the turbo up more quickly.
I disagree..
So your telling me, a 408 with 15psi peaking at 6500rpm can make more power than a 348 15psi peaking at 8000rpm?
Sure apples and oranges, hyd roller va solid roler, but I think you get my point
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09-09-2005, 11:08 AM
#8
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Originally Posted by LIL SS
I disagree..
So your telling me, a 408 with 15psi peaking at 6500rpm can make more power than a 348 15psi peaking at 8000rpm?
Sure apples and oranges, hyd roller va solid roler, but I think you get my point
So your telling me, a 408 with 15psi peaking at 6500rpm can make more power than a 348 15psi peaking at 8000rpm?
Sure apples and oranges, hyd roller va solid roler, but I think you get my point
i believe that the 408 would. the 348 had to spin that much higher to achieve 15 psi. why would it not? considering it had the same turbo
09-09-2005, 12:00 PM
#9
if you look at a compressor map and see the air (lbs/min) vrs pressure ratio that it supports, the map usaully peaks up in the pressure ratio producing more air in its effiency zone.
since a big engine will flow more it takes less boost which means it cant get to the higher pressure ratios a smaller engine can get too
i tried to show on this compressor map maybe it will make it clearer
since a big engine will flow more it takes less boost which means it cant get to the higher pressure ratios a smaller engine can get too
i tried to show on this compressor map maybe it will make it clearer
09-09-2005, 12:18 PM
#10
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Take a 76GTS, and a 346 and a 408. The 346 will make more total hp before the turbo reaches its choke limit. Efficiency is the name of the game, not cubic inches. The only thing the larger CI motor will get you is quicker spool up (which is marginal at best) and a few extra HP on pump gas since a lower boost pressure will equal more lbs/min for the larger CI engine.
http://forcedinductions.com/help.htm
The link above will explain this..
Jose
http://forcedinductions.com/help.htm
The link above will explain this..
Jose
09-09-2005, 01:46 PM
#12
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Originally Posted by 69firebird
yeah, smaller engines can make the same power as larger engines
all in what you want
all in what you want
Generally speaking, the larger the engine the more power potential it has. Not to mention that a larger engine will always make more power at lower rpm's, have a better tq curve, and be better suited for street use with the same components and octane.
I would agree at some point a smaller engine has some advantages, but this is really only true for a max effort engine.
09-09-2005, 01:53 PM
#13
another thing not mentioned here is torque production. i personally would want a smaller engine and reccomend as such to most people because i drive my car mostly on the street. with a turbo torque production is easy. you dont need huge engine sizes to make huge torque. yes the bigger engine will make lower torque also. but IMO thats not the best for a street car because it makes traction a huge problem as well as puts a lot more stress on driveline compenents vs the same hp level on a smaller engine. my .02 anyway.
09-09-2005, 02:18 PM
#14
you guys arnt getting the important fine print.
"WITH THE SAME TURBOCHARGER"
if you take a big engine with a bigger turbocharger, that the engine can support, then ya it will make more power.
but if you take the same turbocharger and a small and large engine, the smaller one will create more peak power before it chokes out, the larger engine will produce a better curve and such, but we're not talking bout that right now, just peak.
remember what is in discussion "THE SAME TURBOCHARGER"
"WITH THE SAME TURBOCHARGER"
if you take a big engine with a bigger turbocharger, that the engine can support, then ya it will make more power.
but if you take the same turbocharger and a small and large engine, the smaller one will create more peak power before it chokes out, the larger engine will produce a better curve and such, but we're not talking bout that right now, just peak.
remember what is in discussion "THE SAME TURBOCHARGER"
09-09-2005, 02:38 PM
#15
When we say the "same turbocharger" does that mean the one that is best matched to the larger engine or the smaller engine, or doesn't it matter?
I think from the first post it looks like he was thinking more cubes but is now considering less cubes...
I think from the first post it looks like he was thinking more cubes but is now considering less cubes...
Originally Posted by smokinHawk
you guys arnt getting the important fine print.
"WITH THE SAME TURBOCHARGER"
if you take a big engine with a bigger turbocharger, that the engine can support, then ya it will make more power.
but if you take the same turbocharger and a small and large engine, the smaller one will create more peak power before it chokes out, the larger engine will produce a better curve and such, but we're not talking bout that right now, just peak.
remember what is in discussion "THE SAME TURBOCHARGER"
"WITH THE SAME TURBOCHARGER"
if you take a big engine with a bigger turbocharger, that the engine can support, then ya it will make more power.
but if you take the same turbocharger and a small and large engine, the smaller one will create more peak power before it chokes out, the larger engine will produce a better curve and such, but we're not talking bout that right now, just peak.
remember what is in discussion "THE SAME TURBOCHARGER"
09-09-2005, 03:21 PM
#17
Originally Posted by FastKat
When we say the "same turbocharger" does that mean the one that is best matched to the larger engine or the smaller engine, or doesn't it matter?
I think from the first post it looks like he was thinking more cubes but is now considering less cubes...
I think from the first post it looks like he was thinking more cubes but is now considering less cubes...
09-09-2005, 06:19 PM
#18
I think the main question (as it always is) what does the person want out of the car?
Me, I wanted a low hp/tq less car to about 4,000rpm.
I wanted big power above that.
My combo I'm building is just that. 348ci / PT91.. Sure it'll be slower to spool than a 408+ ci motor. That's ok for what I plan on doing with the car.
Me, I wanted a low hp/tq less car to about 4,000rpm.
I wanted big power above that.
My combo I'm building is just that. 348ci / PT91.. Sure it'll be slower to spool than a 408+ ci motor. That's ok for what I plan on doing with the car.