twin gt35 61/62 on 6.0, why is it better on 4.8?
Oct 30, 2016 | 10:03 PM
#1
twin gt35 61/62 on 6.0, why is it better on 4.8?
I was a bit confused on this topic.
I saw denmah old twin gt35 on his lq4 where he was having issues of the turbo chocking the lq4. where he made something like 800trq and 550ish whp(unknown boost)(he decided to ditch it as i guess he wasnt happy with the numbers?)
then i saw 03regcab siera
https://www.performancetrucks.net/fo...-again-546291/
which seems to have no problem utilizing the twins and performs extremely well.
in his older dyno
Will there be a point where the 6.0 falls on its face while the 4.8(like in video just keeps going.?)
I guess im a bit confused on why couldnt you just push through?
I mean sure a bigger twin would net more power but if both cars are setup similar and the only thing different is one is 6.0 vs 4.8.
wouldnt the 6.0 make more power at equal psi?
and have wider powerband?
I saw denmah old twin gt35 on his lq4 where he was having issues of the turbo chocking the lq4. where he made something like 800trq and 550ish whp(unknown boost)(he decided to ditch it as i guess he wasnt happy with the numbers?)
then i saw 03regcab siera
https://www.performancetrucks.net/fo...-again-546291/
which seems to have no problem utilizing the twins and performs extremely well.
in his older dyno
Will there be a point where the 6.0 falls on its face while the 4.8(like in video just keeps going.?)
I guess im a bit confused on why couldnt you just push through?
I mean sure a bigger twin would net more power but if both cars are setup similar and the only thing different is one is 6.0 vs 4.8.
wouldnt the 6.0 make more power at equal psi?
and have wider powerband?
Oct 30, 2016 | 10:39 PM
#2
Joined: Jan 2006
Posts: 16,282
Likes: 438
From: Huntsville, AL
Nope, the bigger enine will peak sooner. HP is torque times RPM. A smaller engine can support the same torque at a higher rpm which means more power. Perfect example would be a crotch rocket vs a Harley. The Harley makes 100ftlb at 4000rpm whereas the crotch rocket does it at 16000rpm and has 4 times the power.
So why not just spin all engines faster? Sure, but parasitic losses go with the rpm squared, and tensile forces on the piston and rods is more like the rpm cubed. It's generally cheaper to add more cubic inches than spin something faster.
Don't get so caught up with boost, look at the airflow at the choke line on the turbo compressor map. When the turbo is choked, it won't move any more air even though the boost will increase. High boost needs a lot of exhaust energy so it's usually a net loss of.power when the turbo is choked with more boost. The answer is a larger turbo that goes further to the right on the compressor map and not further upwards.
So why not just spin all engines faster? Sure, but parasitic losses go with the rpm squared, and tensile forces on the piston and rods is more like the rpm cubed. It's generally cheaper to add more cubic inches than spin something faster.
Don't get so caught up with boost, look at the airflow at the choke line on the turbo compressor map. When the turbo is choked, it won't move any more air even though the boost will increase. High boost needs a lot of exhaust energy so it's usually a net loss of.power when the turbo is choked with more boost. The answer is a larger turbo that goes further to the right on the compressor map and not further upwards.
Last edited by Atomic; Oct 30, 2016 at 10:45 PM.
Oct 31, 2016 | 01:19 AM
#5
Former Vendor
Joined: Sep 2016
Posts: 280
Likes: 9
From: Madison, AL
Nope, the bigger enine will peak sooner. HP is torque times RPM. A smaller engine can support the same torque at a higher rpm which means more power. Perfect example would be a crotch rocket vs a Harley. The Harley makes 100ftlb at 4000rpm whereas the crotch rocket does it at 16000rpm and has 4 times the power.
So why not just spin all engines faster? Sure, but parasitic losses go with the rpm squared, and tensile forces on the piston and rods is more like the rpm cubed. It's generally cheaper to add more cubic inches than spin something faster.
Don't get so caught up with boost, look at the airflow at the choke line on the turbo compressor map. When the turbo is choked, it won't move any more air even though the boost will increase. High boost needs a lot of exhaust energy so it's usually a net loss of.power when the turbo is choked with more boost. The answer is a larger turbo that goes further to the right on the compressor map and not further upwards.
So why not just spin all engines faster? Sure, but parasitic losses go with the rpm squared, and tensile forces on the piston and rods is more like the rpm cubed. It's generally cheaper to add more cubic inches than spin something faster.
Don't get so caught up with boost, look at the airflow at the choke line on the turbo compressor map. When the turbo is choked, it won't move any more air even though the boost will increase. High boost needs a lot of exhaust energy so it's usually a net loss of.power when the turbo is choked with more boost. The answer is a larger turbo that goes further to the right on the compressor map and not further upwards.
Oct 31, 2016 | 01:32 AM
#6
how does one consider a turbo for twin application do you just split your desired net flow into two and compare that to the compressor map?
I think if i remember right denmah said his twin peaked out at 5k rpm. is there a downside to a setup that peaks early if desired power is achieved?. that means there would never be a need to rev to 6k? better for the engine right?
Im basically trying to figure out whats the best size twin on a stock 2000 lq4 thats going to have best throttle response for the street and make 650-700whp.
I think if i remember right denmah said his twin peaked out at 5k rpm. is there a downside to a setup that peaks early if desired power is achieved?. that means there would never be a need to rev to 6k? better for the engine right?
Im basically trying to figure out whats the best size twin on a stock 2000 lq4 thats going to have best throttle response for the street and make 650-700whp.
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Oct 31, 2016 | 02:07 AM
#8
funny you say 67mm because i was considering a pair Before i made this post. i was thinking that if the gt35 wont do it then the 67 should be right up in my alley before going twin 70mm.
Compressor 67mm Wheel Compressor
Turbine P Trim .81 A/R Turbine
Turbine Wheel 74.1mm/64.6mm
CXRacing T4 T67 Turbo Charger Turbocharger .81AR P Trim 67mm Wheel 500+ HP | eBay
Oct 31, 2016 | 02:10 AM
#9
are you talking about a $2000 turbo? or am i looking at a wrong one?
funny you say 67mm because i was considering a pair Before i made this post. i was thinking that if the gt35 wont do it then the 67 should be right up in my alley before going twin 70mm.
Compressor 67mm Wheel Compressor
Turbine P Trim .81 A/R Turbine
Turbine Wheel 74.1mm/64.6mm
CXRacing T4 T67 Turbo Charger Turbocharger .81AR P Trim 67mm Wheel 500+ HP | eBay
funny you say 67mm because i was considering a pair Before i made this post. i was thinking that if the gt35 wont do it then the 67 should be right up in my alley before going twin 70mm.
Compressor 67mm Wheel Compressor
Turbine P Trim .81 A/R Turbine
Turbine Wheel 74.1mm/64.6mm
CXRacing T4 T67 Turbo Charger Turbocharger .81AR P Trim 67mm Wheel 500+ HP | eBay
I am not sure if I bought Turbos and they came with the truck or if I bought a truck that came with the turbo's....
There was also a LQ4 in it as well.
