NA AFR 205 build, 12:1 compresion ratio or higher?
08-25-2015, 06:53 PM
#1
NA AFR 205 build, 12:1 compresion ratio or higher? So I'm seriously considering getting rid of the giant heads on my 98 Z28 currently in favor of some AFR 205s. If I'm going for the max power I can get at stock naturally aspirated displacement, what is the max compression ratio I can run on 93 octane before its counter productive? The goal of the car is excellent street manners and the best optimal balance between fuel economy and power. I'm after atleast 475 rwhp. Current setup is as follows:
TSP Magic Stick 4 Cam 239/242 .649"/609" 111 LSA (Getting rid of this ASAP in favor of optimal cam for heads)
LS6 Intake
GM LS6 Race Heads- 61.9cc, 250cc Intake, 85cc exhaust
Yella Terra Rockers 1.7:1 Ratio
PRC Dual Valve Springs w/Titanium Retainers. Previous owner says the springs only have 300 miles on them.
Thunder Racing Hardened Pushrods 7.4"
GM CTS-V Race lifters (GM 88958689)
ARP Rod and Main bolts
Powerband Underdrive Pulley
BBK 80mm Throttle Body
36# injectors
Ported MAF
Jet Hot 1 7/8" Longtube Headers
S60 w/ 4.10s
Car is an M6.
TSP Magic Stick 4 Cam 239/242 .649"/609" 111 LSA (Getting rid of this ASAP in favor of optimal cam for heads)
LS6 Intake
GM LS6 Race Heads- 61.9cc, 250cc Intake, 85cc exhaust
Yella Terra Rockers 1.7:1 Ratio
PRC Dual Valve Springs w/Titanium Retainers. Previous owner says the springs only have 300 miles on them.
Thunder Racing Hardened Pushrods 7.4"
GM CTS-V Race lifters (GM 88958689)
ARP Rod and Main bolts
Powerband Underdrive Pulley
BBK 80mm Throttle Body
36# injectors
Ported MAF
Jet Hot 1 7/8" Longtube Headers
S60 w/ 4.10s
Car is an M6.
08-25-2015, 07:21 PM
#3
compression ratio is just a static calculation but the DCR or cylinder cranking compression is what is actually happening in the can. Camshaft timing (valve events), quench clearance, and combustion chamber shape (efficiency) all play vital roles in detonation prevention. The quality and consistency of the fuel is important as well. Are we talking 93 plus 10% MTBE or "good ol' gas" ????
The cam you have now would probably have a low enough cylinder pressure to work with 93 at 12 to one with a good tune and combustion chamber shape.
Unless you found a deal on the 205s, most will try to talk you into the 210V2 or Tony's new MMS220s and with 11.5 range squeeze plus a moderate 230 range valve tickler......475 would be quite achievable past an M6 with the right clutch and a FAST 102 intake.
The cam you have now would probably have a low enough cylinder pressure to work with 93 at 12 to one with a good tune and combustion chamber shape.
Unless you found a deal on the 205s, most will try to talk you into the 210V2 or Tony's new MMS220s and with 11.5 range squeeze plus a moderate 230 range valve tickler......475 would be quite achievable past an M6 with the right clutch and a FAST 102 intake.
08-25-2015, 07:44 PM
#4
TECH Fanatic
Join Date: Aug 2009
Location: Coast of San Mateo County Between Pacifica & HMB
Posts: 1,815
Received 215 Likes
on
128 Posts
Check out DarthV8r's MMS220 build thread. Then contact Tony!
MMS220s with light valves, MAMOFIED FAST102, NW102TB,
CAM MOTION 231*/235* 114*+2* .610"/.590" with optimized
Valve train, Light Clutch, Dual Exhaust, 11.0-11.5:1 Compression.
Would clear 475 RWHP on the low side, should Exceed
500 RWHP and be very drivable with a small/medium cam!
MMS220s with light valves, MAMOFIED FAST102, NW102TB,
CAM MOTION 231*/235* 114*+2* .610"/.590" with optimized
Valve train, Light Clutch, Dual Exhaust, 11.0-11.5:1 Compression.
Would clear 475 RWHP on the low side, should Exceed
500 RWHP and be very drivable with a small/medium cam!
08-26-2015, 12:01 AM
#5
Moderator
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,836 Likes
on
1,145 Posts
I would bet if you kept the cam and lifters, ditched the intake for a ported fast, mamofied the mms220 heads, you could clear 500. Mamofied would come with springs etc.
08-26-2015, 09:57 AM
#7
Do you guys forget about the OP's other thread?
Anyway, with something like a 228/232 cam, which is considered the sweet spot for all around power, tq, driveability, for a LS1... you are not going to want to run more then 11.5:1 compression.
I am sure you could send the AFR 205's to Tony and have them gone through, he is the man for AFR combos. Remember he helped Pat G make 500whp in a LS1 with a 205 and a XER cam.
Anyway, with something like a 228/232 cam, which is considered the sweet spot for all around power, tq, driveability, for a LS1... you are not going to want to run more then 11.5:1 compression.
I am sure you could send the AFR 205's to Tony and have them gone through, he is the man for AFR combos. Remember he helped Pat G make 500whp in a LS1 with a 205 and a XER cam.
Trending Topics
08-26-2015, 09:59 AM
#8
I don't mean to be the bearer of bad news, but you're not going to reach those numbers with a LS6 intake. With a FAST 102/102 setup, maybe, but definitely not with a LS6 intake. You need to also take into consideration that the S60 is going to eat up some HP on the dyno.
08-26-2015, 10:29 AM
#9
I ran 11.7 with my old car. She ran fine. 27* timing, #'s in sig. Mine were milled to 59cc and I ran GM MLS .051 gaskets (my only regret) as I should have ran a Cometic .040.
The 205's are still an excellent head and VERY cheap used compared to anything new out there. If you can find a deal, I say go for it.
The 205's are still an excellent head and VERY cheap used compared to anything new out there. If you can find a deal, I say go for it.
08-26-2015, 10:39 AM
#10
I don't mean to be the bearer of bad news, but you're not going to reach those numbers with a LS6 intake. With a FAST 102/102 setup, maybe, but definitely not with a LS6 intake. You need to also take into consideration that the S60 is going to eat up some HP on the dyno.
Yeah I realize that the LS6 will be a bottleneck but as long as I know the potential is there and the car dynoed within what a Fast could give me, I'd be happy.
And thinking about it, maybe I should have just bumped my old thread regarding this but wanted this one centered around the fact that I have pretty much made an iron clad choice to go with AFR 205s. The other thread for reference is:
https://ls1tech.com/forums/generatio...big-heads.html
This is possibly a complex question but is there any guess on how much power I would pick up by going from 11.5 to lets say 12:1 compression? If the only change needed is going with a thinner Cometic gasket, are there ANY downsides to doing this? (Other than knock of course but this is assuming 93 is good enough to avoid that.)
08-26-2015, 10:59 AM
#11
You are not going to get away with 12:0:1 compression on 93 with a reasonable sized cam. If you kept the large cam like the MS4 which will bleed off some dynamic compression then yes it would be possible. Research it or call and talk to a expert like Tony and he can explain it in further detail.
08-26-2015, 11:25 AM
#12
You are not going to get away with 12:0:1 compression on 93 with a reasonable sized cam. If you kept the large cam like the MS4 which will bleed off some dynamic compression then yes it would be possible. Research it or call and talk to a expert like Tony and he can explain it in further detail.
08-26-2015, 12:23 PM
#16
Moderator
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,836 Likes
on
1,145 Posts
We're all trying to live vicariously through you
08-26-2015, 01:47 PM
#19
TECH Fanatic
Join Date: Aug 2009
Location: Coast of San Mateo County Between Pacifica & HMB
Posts: 1,815
Received 215 Likes
on
128 Posts
1.0 Pt of Compression optimized is approximately = to 4% depending
On several factors, ie going from 10.0-11.0:1 worth a little more than
11.0-12.0:1 so .5 going from 11.5-12.0 worth at best 2%, so on
500 RWHP were talking 10 RWHP at best, with a lot more detonation
Likely! 227*-231* Intake duration is the sweet spot for 347" and
AFR 205-215 heads for a street/strip engine with HP Peak 6400-6800
Rpm. Adding 4-6* to the exhaust depending on True Dual Exhaust
Vs Y Merge, maybe up to 8* if not so good. LSA from 113*-115*
with 2-3* of advance provides best Performance,Driveability, and
Fuel Economy (should you care).LS6 Intake will hold back at least!
20-25 RWHP On this build compared to an out of the box FAST102, 35+
MAMOFIED on the results you are looking for.
Don't necessarily need AFR205s MAMOFIED just
Want to be sure the heads you get are still good and don't need
A bunch of work! Light valves the correct springs,rockers,pushrods
And geometry are all critical at 6500+ RPM & 450+ RWHP!
CAM MOTION Cams provide the best lobe profiles IMHO for valvetrain
Stability which adds to power, along with better quality steel for durability
and longevity.
Good Luck just my .02
On several factors, ie going from 10.0-11.0:1 worth a little more than
11.0-12.0:1 so .5 going from 11.5-12.0 worth at best 2%, so on
500 RWHP were talking 10 RWHP at best, with a lot more detonation
Likely! 227*-231* Intake duration is the sweet spot for 347" and
AFR 205-215 heads for a street/strip engine with HP Peak 6400-6800
Rpm. Adding 4-6* to the exhaust depending on True Dual Exhaust
Vs Y Merge, maybe up to 8* if not so good. LSA from 113*-115*
with 2-3* of advance provides best Performance,Driveability, and
Fuel Economy (should you care).LS6 Intake will hold back at least!
20-25 RWHP On this build compared to an out of the box FAST102, 35+
MAMOFIED on the results you are looking for.
Don't necessarily need AFR205s MAMOFIED just
Want to be sure the heads you get are still good and don't need
A bunch of work! Light valves the correct springs,rockers,pushrods
And geometry are all critical at 6500+ RPM & 450+ RWHP!
CAM MOTION Cams provide the best lobe profiles IMHO for valvetrain
Stability which adds to power, along with better quality steel for durability
and longevity.
Good Luck just my .02