Compression Ratio Question - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

ss_redrum · 10-08-2020, 10:09 PM

Trying to decide on my compression ratio. Here is whats going on:

I have a single turbo set up. Going to run 12psi.

I am currently pulling the engine and purchasing the TSP 416 CID Forged Rotating Assembly.

Now. I keep reading different information and after talking with TSP I need to make a decision on the CR.
TSP said I should either run 10:1 CR with the -15cc pistons or run 9.63:1 with -20cc pistons.

I am wanting to stay on 93 pump gas for now but will eventually go to E85. I currently don't have e85 in my area.

It will mostly be a street car with trips to the strip. What do yall recommend?

madmikeismad · 10-08-2020, 10:41 PM

If you're going to run e85 permanently when it's available, then run the higher compression for sure. And honestly, 10:1 on 93 will take a lot of boost and timing. And if you're running meth, a bigger cam, ice box, etc..., you can get away with a bit more. Look at what guys are doing with stock ls3's with 10.7:1 or whatever they are.

EDIT: Also, not sure what size turbo you plan on, but remember the bigger you go, the less boost pressure you need to make the same power (usually). If it were mine, and I planned to run E, I'd run closer to 11:1, and I'd feel super safe at 10:1.

Black_SS10 · 10-09-2020, 05:24 AM

10.5:1. That will be fine for 93 and even better for E85. Also static compression isn't as important as your dynamic compression (DCR) which also takes in account your valve events, ie your cam specs. Higher DCR can better utilize or require higher octane fuel.

Greenhornet2 · 10-09-2020, 07:15 AM

Higher compression will feel a little better for you while not in boost i feel. If end goals are over 1000whp. Then I'd talk to someone like ted jannetty

JMI · 10-09-2020, 01:31 PM

I would go with at least 10-1 compression. E85 or 91-93 and Meth would be the best way to go.

hillshooter · 10-09-2020, 01:53 PM

Like any of us you wont be satisfied with 12 pounds. Give yourself room to grow. I have the -15CC pistons and can run up to 25 pounds on E85. I dont think you will see much of a difference in 5CC, maybe some pedal feel.

bayarea408 · 10-09-2020, 05:45 PM

What turbo are you running on this huron kit on a 416? 3" down pipe T4 stuff is already checking out due to back pressure for most 376 guys around 14-15 lb's. optimal CR's are important for sure, but you shouldn't just mindlessly plug a small turbo up to a 416, you will meet the ceiling due to back pressures before you push water.

Pump gas primarily - lower CR 9's you can run more boost before you reach the octane limits of pump

E85 primarily - higher CR mid low 10's" "stockish" E85 more efficiently works to make you additional power with additional timing and compression due to combustion behaviors of the fuel

You need to ask yourself are you REALLY going E85?

10-08-2020, 10:09 PM	#1
ss_redrum Drives: 2013 LS3 Camaro Join Date: Jul 2017 Location: Augusta, GA Posts: 94	Compression Ratio Question Trying to decide on my compression ratio. Here is whats going on: I have a single turbo set up. Going to run 12psi. I am currently pulling the engine and purchasing the TSP 416 CID Forged Rotating Assembly. Now. I keep reading different information and after talking with TSP I need to make a decision on the CR. TSP said I should either run 10:1 CR with the -15cc pistons or run 9.63:1 with -20cc pistons. I am wanting to stay on 93 pump gas for now but will eventually go to E85. I currently don't have e85 in my area. It will mostly be a street car with trips to the strip. What do yall recommend? __________________ 2013 LS3 - Huron Speed Single Turbo - Tuned by me. -Previous Setup- Texas Speed 1 7/8 LT Headers, no cats, xpipe, muffler delete, K&N Cold Air Intake, tuned by DynoSteve Youtube \|Instagram

10-08-2020, 10:41 PM	#2
madmikeismad Drives: 2012 ZL1 Join Date: Mar 2020 Location: Oklahoma City Posts: 66	If you're going to run e85 permanently when it's available, then run the higher compression for sure. And honestly, 10:1 on 93 will take a lot of boost and timing. And if you're running meth, a bigger cam, ice box, etc..., you can get away with a bit more. Look at what guys are doing with stock ls3's with 10.7:1 or whatever they are. EDIT: Also, not sure what size turbo you plan on, but remember the bigger you go, the less boost pressure you need to make the same power (usually). If it were mine, and I planned to run E, I'd run closer to 11:1, and I'd feel super safe at 10:1. __________________ '12 ZL1 - RPM 5", TSP 2" headers, Speed Engineering 3" header back, Dayco 8.66 lower/LPE 2.38 upper with solid isolator and 10 bolt hub, hand ported blower and snout and went way too far, ID1050x's, DSX aux harness with a summit 400lph pump on E, NGK TR8's with Taylor wires, 160* tstat, NW 102, UPR catch cans, HP Tuners, Stock unopened long block

10-09-2020, 05:24 AM	#3
Black_SS10 SomeguyK Drives: 2010 Black 2SS/RS Join Date: Nov 2014 Location: FL Posts: 1,947	10.5:1. That will be fine for 93 and even better for E85. Also static compression isn't as important as your dynamic compression (DCR) which also takes in account your valve events, ie your cam specs. Higher DCR can better utilize or require higher octane fuel. __________________ TMS 427, Dart iron Block, Forged assembly, Frankenstien heads, AGP TT 62/62 BB turbo's, AGP/Fore triple fuel system, Tilton clutch, Holley 1 7/8 shorties, Technostalgia tail lights,Oracle, Aeroforce, MGW shifter,Flowmaster, Pegasus subframe bushings,BMR trailing & toe arms,Z28 UCA bushings,Zl1 rear sway bar,Prothane,BMR,Goodridge brake lines,Ridetech HQ coilovers,3.91,Trutrac,billet caps,DSS axles,HE offest,built TR6060,1LE diffuser,Havoc spoiler,SSclones,20in MRR 017, Pirelli P Zero, Nitto NT555RII More to come.

10-09-2020, 07:15 AM	#4
Greenhornet2 Drives: 2011 Camaro 2SS LS3 Whipple Join Date: May 2019 Location: Connecticut Posts: 1,925	Higher compression will feel a little better for you while not in boost i feel. If end goals are over 1000whp. Then I'd talk to someone like ted jannetty __________________ Whipple 2.9 CAI ID1050x injectors ZL1 Pump JRE FPCM JMS Voltage booster JRE Rough Idle blower cam BTR .660 springs CHE trunnion kit 1 7/8 Speed Engineering Borla Atak JRE scoop 1.5" lowering springs BMR trailing arms and toe links Cradle inserts 704WHP 603WTQ 93 octane

10-09-2020, 01:31 PM	#5
JMI Drives: Red Jewel Camaro SS Join Date: Mar 2014 Location: East Coast Posts: 393	I would go with at least 10-1 compression. E85 or 91-93 and Meth would be the best way to go. __________________ BTR LSX388,AGP Twin Turbo.6L90,GM 9.9" Diff.Fore Innovations Level 4 fuel system.Great fuel economy !!!! 1xxx RWHP

10-09-2020, 01:53 PM	#6
hillshooter Drives: 2015 Camaro SS commemorative Join Date: May 2015 Location: Utah Posts: 425	Like any of us you wont be satisfied with 12 pounds. Give yourself room to grow. I have the -15CC pistons and can run up to 25 pounds on E85. I dont think you will see much of a difference in 5CC, maybe some pedal feel. __________________ 2015 Camaro SS, LS3 Stroker, PRC heads,CUSTOM CAM. AGP 68/68 with custom Hot and Cold side. Fore triple pumps, Holley terminator X. BMR drag suspension with carlyle brake kit. 15" ET drags and 17" skinnies. ZL1 3.73 gears , aluminum driveshaft. TH400 with circle D converter.

10-09-2020, 05:45 PM	#7
bayarea408 Drives: T Join Date: Mar 2015 Location: CA Posts: 803	What turbo are you running on this huron kit on a 416? 3" down pipe T4 stuff is already checking out due to back pressure for most 376 guys around 14-15 lb's. optimal CR's are important for sure, but you shouldn't just mindlessly plug a small turbo up to a 416, you will meet the ceiling due to back pressures before you push water. Pump gas primarily - lower CR 9's you can run more boost before you reach the octane limits of pump E85 primarily - higher CR mid low 10's" "stockish" E85 more efficiently works to make you additional power with additional timing and compression due to combustion behaviors of the fuel You need to ask yourself are you REALLY going E85? Last edited by bayarea408; 10-09-2020 at 05:56 PM.