Off Boost Drivability w/ lower C/R engines?
#1
Instructor
Thread Starter
Off Boost Drivability w/ lower C/R engines?
Hey guys,
I'd like to hear from those of you who have lower compression ratio LS 2's and 3's and how they drive when off boost. How does the throttle response, torque and power feel compared to stock? Please post engine, C/R, what forced induction you're running, max psi, power and torque.
I'm trying to get an idea of what C/R I ultimately want to run since I do not want to lose too much off boost manners. Thanks.
I'd like to hear from those of you who have lower compression ratio LS 2's and 3's and how they drive when off boost. How does the throttle response, torque and power feel compared to stock? Please post engine, C/R, what forced induction you're running, max psi, power and torque.
I'm trying to get an idea of what C/R I ultimately want to run since I do not want to lose too much off boost manners. Thanks.
#3
Burning Brakes
#5
Burning Brakes
#6
Le Mans Master
Lemme put it differently. I've raised compression on an LS motor with no other changes other than tune. Off boost drivabilty, power, and fuel eco all went up.
This was basically an iron block LS2 with ported heads, mild blower cam, and 10psi of boost
This was basically an iron block LS2 with ported heads, mild blower cam, and 10psi of boost
Last edited by old motorhead; 06-14-2018 at 03:32 PM.
#7
Instructor
Thread Starter
I understand all those factors go up with increased C/R. But my car is already supercharger and I'm rebuilding the engine with lower C/R in mind and am trying to find a balance between lower (and safer) C/R and driveability. This is mostly a street driven car out of boost 95% of the time, but I do take it to the track on occasion and enjoy a hard pull every now and then. I don't care about end hp and torque figures, I care more about engine engine safety and manners. For an example, I went with a fairly mild camshaft instead of the alternative.
So again, if anyone has real world experience with these engines anywhere between 9/1 and 10/1 C/R, id like to hear about how the engine behaves off boost and how much boost/hp/torque the given C/R is ultimately handling, preferably without meth or E85.
I want to run straight 93 octane pump gas for ease. I don't plan on going above 15 psi or 700 rwhp and 600 rwt. I'm leaning towards 9.5/1 but if I can get away with higher I'll gladly too it.
So again, if anyone has real world experience with these engines anywhere between 9/1 and 10/1 C/R, id like to hear about how the engine behaves off boost and how much boost/hp/torque the given C/R is ultimately handling, preferably without meth or E85.
I want to run straight 93 octane pump gas for ease. I don't plan on going above 15 psi or 700 rwhp and 600 rwt. I'm leaning towards 9.5/1 but if I can get away with higher I'll gladly too it.
#8
Drifting
10:1 LS7 here running 13psi. There may have been a slight decrease in throttle response, but not much. Drives great and I only lost about 20 lb/ft of TQ after dropping 1 point of compression.
#9
Drifting
9:1 LS7 with 850/850 RWHP/TQ. I have twin turbo setup with GT30’s. 16 lbs. boost. Run 16 degrees total timing with meth and about 25-35* timing in MAP areas out of boost. Start cutting back on timing 4200-4800rpm through peak torque. No impact on torque with turbos off Boost.
#10
Melting Slicks
Hey guys,
I'd like to hear from those of you who have lower compression ratio LS 2's and 3's and how they drive when off boost. How does the throttle response, torque and power feel compared to stock? Please post engine, C/R, what forced induction you're running, max psi, power and torque.
I'm trying to get an idea of what C/R I ultimately want to run since I do not want to lose too much off boost manners. Thanks.
I'd like to hear from those of you who have lower compression ratio LS 2's and 3's and how they drive when off boost. How does the throttle response, torque and power feel compared to stock? Please post engine, C/R, what forced induction you're running, max psi, power and torque.
I'm trying to get an idea of what C/R I ultimately want to run since I do not want to lose too much off boost manners. Thanks.
I'd suspect most people driving two with say 1 full point CR wouldnt even be able to tell the difference....maybe even 2 full points !
#11
Melting Slicks
I understand all those factors go up with increased C/R. But my car is already supercharger and I'm rebuilding the engine with lower C/R in mind and am trying to find a balance between lower (and safer) C/R and driveability. This is mostly a street driven car out of boost 95% of the time, but I do take it to the track on occasion and enjoy a hard pull every now and then. I don't care about end hp and torque figures, I care more about engine engine safety and manners. For an example, I went with a fairly mild camshaft instead of the alternative.
So again, if anyone has real world experience with these engines anywhere between 9/1 and 10/1 C/R, id like to hear about how the engine behaves off boost and how much boost/hp/torque the given C/R is ultimately handling, preferably without meth or E85.
I want to run straight 93 octane pump gas for ease. I don't plan on going above 15 psi or 700 rwhp and 600 rwt. I'm leaning towards 9.5/1 but if I can get away with higher I'll gladly too it.
So again, if anyone has real world experience with these engines anywhere between 9/1 and 10/1 C/R, id like to hear about how the engine behaves off boost and how much boost/hp/torque the given C/R is ultimately handling, preferably without meth or E85.
I want to run straight 93 octane pump gas for ease. I don't plan on going above 15 psi or 700 rwhp and 600 rwt. I'm leaning towards 9.5/1 but if I can get away with higher I'll gladly too it.
Lets face it....GM chose 9.1:1 for the LS9/LSA.....are people running around saying they're turds or crap off boost ? And you can fuel them anywhere and beat the crap out of them all day long.
Last edited by stevieturbo; 06-15-2018 at 04:35 PM.
#12
Instructor
Thread Starter
#13
Instructor
Thread Starter
#14
Instructor
Thread Starter
9:1 LS7 with 850/850 RWHP/TQ. I have twin turbo setup with GT30’s. 16 lbs. boost. Run 16 degrees total timing with meth and about 25-35* timing in MAP areas out of boost. Start cutting back on timing 4200-4800rpm through peak torque. No impact on torque with turbos off Boost.
#15
Instructor
Thread Starter
Then that answers it for you. There is nothing in your post that even hints towards a higher compression offering any real world benefit at all. 9.5 will be ideal.
Lets face it....GM chose 9.1:1 for the LS9/LSA.....are people running around saying they're turds or crap off boost ? And you can fuel them anywhere and beat the crap out of them all day long.
Lets face it....GM chose 9.1:1 for the LS9/LSA.....are people running around saying they're turds or crap off boost ? And you can fuel them anywhere and beat the crap out of them all day long.
#16
Melting Slicks
If you have E85 available to you, then it would be a no brainer.
But like me....it isnt. Regular pump fuel is all there is here hence build accordingly.
I've ran my CR at low 9's for years and I've run 20psi boost many times on pump alone. Although when racing or for speed events where traction may be better I would also use meth and for higher boost levels too.
But 90% of the time I simply do not need meth as I've access to more power than traction away.
Although I do live in a relatively cold climate so rarely have high ambients or charge temps to deal with.
Although if you're in a very hot climate that could be even more justification for adding a little safety into the build.
Obviously the LSA blower itself will resolve any concerns anyone might have about low rpm performance, but I'm sure there are many out there who just run a Crate LSX376 B15 etc which is around 9.0:1 and have no complaints and there have been users making over 1k with them
But like me....it isnt. Regular pump fuel is all there is here hence build accordingly.
I've ran my CR at low 9's for years and I've run 20psi boost many times on pump alone. Although when racing or for speed events where traction may be better I would also use meth and for higher boost levels too.
But 90% of the time I simply do not need meth as I've access to more power than traction away.
Although I do live in a relatively cold climate so rarely have high ambients or charge temps to deal with.
Although if you're in a very hot climate that could be even more justification for adding a little safety into the build.
Obviously the LSA blower itself will resolve any concerns anyone might have about low rpm performance, but I'm sure there are many out there who just run a Crate LSX376 B15 etc which is around 9.0:1 and have no complaints and there have been users making over 1k with them
Last edited by stevieturbo; 06-19-2018 at 05:02 AM.
#17
Burning Brakes
On the other hand, who cares if underhood temps are ok with your setup while cruising.
#18
Instructor
Thread Starter
If you have E85 available to you, then it would be a no brainer.
But like me....it isnt. Regular pump fuel is all there is here hence build accordingly.
I've ran my CR at low 9's for years and I've run 20psi boost many times on pump alone. Although when racing or for speed events where traction may be better I would also use meth and for higher boost levels too.
But 90% of the time I simply do not need meth as I've access to more power than traction away.
Although I do live in a relatively cold climate so rarely have high ambients or charge temps to deal with.
Although if you're in a very hot climate that could be even more justification for adding a little safety into the build.
Obviously the LSA blower itself will resolve any concerns anyone might have about low rpm performance, but I'm sure there are many out there who just run a Crate LSX376 B15 etc which is around 9.0:1 and have no complaints and there have been users making over 1k with them
But like me....it isnt. Regular pump fuel is all there is here hence build accordingly.
I've ran my CR at low 9's for years and I've run 20psi boost many times on pump alone. Although when racing or for speed events where traction may be better I would also use meth and for higher boost levels too.
But 90% of the time I simply do not need meth as I've access to more power than traction away.
Although I do live in a relatively cold climate so rarely have high ambients or charge temps to deal with.
Although if you're in a very hot climate that could be even more justification for adding a little safety into the build.
Obviously the LSA blower itself will resolve any concerns anyone might have about low rpm performance, but I'm sure there are many out there who just run a Crate LSX376 B15 etc which is around 9.0:1 and have no complaints and there have been users making over 1k with them