Considering a G8 Gt have a few questions
01-07-2009, 03:58 PM
#1
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Considering a G8 Gt have a few questions What are the gear ratios in the transmission?
Six speed auto is:
1st is 6.04, have also seen 4:02. Do not know which one is in the G8
2nd is 2.36
3rd is 1.53
4th is 1.15
5th is .85
6th is .67
What gear are dynos done? Is there a correction factor for the lack of 1:1?
What is the factory rpm fuel shutoff?
What rpm is peak hp? I have seen 5400rpm?, peak tq? Again have seen 4500rpm.
Most folks post peak numbers without rpm but performance appears similar to to an LS1 GTO, a bit more torque from the G8GT but more rpm from the LS1.
Six speed auto is:
1st is 6.04, have also seen 4:02. Do not know which one is in the G8
2nd is 2.36
3rd is 1.53
4th is 1.15
5th is .85
6th is .67
What gear are dynos done? Is there a correction factor for the lack of 1:1?
What is the factory rpm fuel shutoff?
What rpm is peak hp? I have seen 5400rpm?, peak tq? Again have seen 4500rpm.
Most folks post peak numbers without rpm but performance appears similar to to an LS1 GTO, a bit more torque from the G8GT but more rpm from the LS1.
01-09-2009, 04:53 PM
#3
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Received answers on another forum to confirm. I saw 6.04 1st in a GM press release. Now believe that was for other vehicles.
However, another G8 owner advises stock fuel shutoff/rev limiter is 6000rpm
However, another G8 owner advises stock fuel shutoff/rev limiter is 6000rpm
01-09-2009, 07:51 PM
#5
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Thread Starter
Tune will not change the gear ratios, gear ratio where dyno is measured, nor what correction factor is used for non-availability of 1:1.
Intake manifold torque peak is fixed as intake is tuned for maximum torque at a given rpm.
Max rpm is important is need to know at what rpm factory camshaft finishes producing power and where engine rpm limit is. For example, LS1 and LS2 peak at similar rpm stock but LS2 has 6600rpm limit. LS1 is 6120rpm. (Well at least mine is 6120rpm) LS2 has much stronger springs than LS1 which allow for safe use to 6600rpm. LS1 springs are weak and not recommended for regular high rpm use. L76 engine has same cam lift as LS1. Believe L76 is factory limited to 6000rpm to either save the transmission as it an auto or due to weak springs in the engine. L76 is new to me and prefer to research rather than mod down the same road as others.(I recall the fellow who installed LS7 rockers on his LS2 had numerous issues. A bit of research would have resolved the issue prior to installation) Owner is the final say on any mods and the only person responsible for success or failure.
Another point is that I always followed the advice of 4L80 owners not to build a car with shift points higher than 6000rpm, (particularly in a 37XXlb heavy car as the GTO) or the transmission will not survive for any lengthy duration of service. Do not know at this point if the 6L80 would follow the same advice.
I tend to distrust automatic transmissions in heavy cars with high power output. Am not convinced the G8 would make me happy. Might be best to save for a year an purchase a manual transmission car. -Camaro, G8, maybe a challenger.
Intake manifold torque peak is fixed as intake is tuned for maximum torque at a given rpm.
Max rpm is important is need to know at what rpm factory camshaft finishes producing power and where engine rpm limit is. For example, LS1 and LS2 peak at similar rpm stock but LS2 has 6600rpm limit. LS1 is 6120rpm. (Well at least mine is 6120rpm) LS2 has much stronger springs than LS1 which allow for safe use to 6600rpm. LS1 springs are weak and not recommended for regular high rpm use. L76 engine has same cam lift as LS1. Believe L76 is factory limited to 6000rpm to either save the transmission as it an auto or due to weak springs in the engine. L76 is new to me and prefer to research rather than mod down the same road as others.(I recall the fellow who installed LS7 rockers on his LS2 had numerous issues. A bit of research would have resolved the issue prior to installation) Owner is the final say on any mods and the only person responsible for success or failure.
Another point is that I always followed the advice of 4L80 owners not to build a car with shift points higher than 6000rpm, (particularly in a 37XXlb heavy car as the GTO) or the transmission will not survive for any lengthy duration of service. Do not know at this point if the 6L80 would follow the same advice.
I tend to distrust automatic transmissions in heavy cars with high power output. Am not convinced the G8 would make me happy. Might be best to save for a year an purchase a manual transmission car. -Camaro, G8, maybe a challenger.
