The disadvantage here is that you really have to have a GREAT tuner because the combustion temperatures and pressure is HIGHER with this type of set up. The bottom line is the AVERAGE HP/Torque is higher than on most cars and is certainly higher compared to if I was running typical boosted compression levels. Because of the wider power band, at that point in time it is very difficult to run this car down even if you have a weight and peak power advantage. In roll racing which is my favorite type of competitive event, we typically jump out to a 2-3 car lengths advantage at the punch even over cars that weigh 800-900 pounds less and that have maybe 2-300 more PEAK HP. More compression makes the engine more efficient and helps make a broader power curve. Well I am running more compression than most at about 11.3 to one with about 22 pounds of boost. Part of me wonders if a middle of the road build with 9.5:1 and boost in the 10-15 psi range might be better all around.Īnd to be clear.this thread should be about all FI options with the LS engines. But most detailed discussions with builders who have experience with KB's say the same thing.lower the CR and let the big dog eat and control the detonation with timing. But then again with the lower CR, the octane goes a lot further too. The bigger the boost, the bigger the temp rise.yet that thin intercooler brick gets no bigger and therefore removes less heat. I think the rule of thumb is that your going to get heat to the tune of 10 degrees per pound of boost and then it's up to your intercooler to get that back down. For my KB, lower the CR and let the big dog eat.īut the thing that concerns me with top mount PD blowers on these LS motors is that there is such a tiny space in the valley to fit an intercooler brick (at least as compared to a DOHC engine). I've got a few thoughts running around in my brain but I'm kind of with you. If I had a bigger blower such as a whipple or kb like yourself, I would run the lower compression and let the blower do the work These guys run big boost 25+ range and have set the sbe records. The stock 5.3 guys like to use 317 heads, which net 8.4:1, while other guys like the 243 or 799 heads which net 9:1 compensate for the lack of blower!Īs far as the turbo goes. And I will add compression when this motor goes. with the 1.9l blower I have 10.9:1 compession. Maybe turbo is better with high CR while blowers better with low CR? I've got a feeling that there isn't a perfect right or wrong answer here.

I'm wondering if we can get some detailed write ups from those with experience explaining the logic behind their position? Mention all the variables and give some details. 10:1 is king? But then there are many tried and true 'old school' (low CR / high boost) putting up some impressive numbers as well. I've been reading a lot of strong opinions that the old school 9.0:1 CR for forced induction is not the way to go with these LS motors. So many variables and trade offs related to compression.octane vs boost vs timing (probably the 3 most dominant factors), IAT, bower type, turbo, throttle response, gas mileage, etc, etc, etc. Answers on this subject are all over the board.

I've been doing a ton of searches and reading a lot of threads. But I'd love to get a big thread going on forced induction compression ratio. Not sure if this thread will take off or not.

Ls1 compression ratio