Looking for compression vs cam sweet spot
09-08-2018, 05:50 PM
#1
Looking for compression vs cam sweet spot I am starting to think about what I want to do next year for my heads and cam selection. I am going to flex-fuel at the same time, so I want a good compression bump. I do not want to flycut the pistons, so the combo will need to clear the recommended P2V, which I think is .08 intake and .1 exhaust. I will be getting Trick Flow heads, so the valve angle allows more compression.
Is there a "sweet spot" between compression and cam size? i.e. 11.5:1 compression and 230/230 .630/.630 114 cam vs 12:1 compression and 228/228 .6/.6 114 (just examples off the top of my head, not real ideas)
My goal is <11sec 1/4 mile and the motor not trying to die when the AC is on in the summer.
Is there a "sweet spot" between compression and cam size? i.e. 11.5:1 compression and 230/230 .630/.630 114 cam vs 12:1 compression and 228/228 .6/.6 114 (just examples off the top of my head, not real ideas)
My goal is <11sec 1/4 mile and the motor not trying to die when the AC is on in the summer.
09-08-2018, 06:08 PM
#2
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Short answer is yes. I dont swear by dynamic compression (DCR) but I do refer to it for a daily driver. Compression calculated from the 006 IVC to TDC. On 91 octane, I like 8.3-8.5. On 93 octane, I'll push it to 8.75. For E85, you can do more, but if you are ever stuck with no E85 available you are screwed.
There are calculators out there that you can use or when you are soeccing a cam with a vendor just ask about the DCR. Most often they will put you near 8.3, which is a good balance between safe and good throttle response on the street.
There are calculators out there that you can use or when you are soeccing a cam with a vendor just ask about the DCR. Most often they will put you near 8.3, which is a good balance between safe and good throttle response on the street.
09-08-2018, 08:41 PM
#3
DCR is a good reference point. Not the be-all end-all, but a good benchmark. Use it as a starting point. Then kinda figure out from there which side of all the errors and compromises you want to err towards... give up a little power in favor of driveability, give up the price of fuel for power, etc.
09-09-2018, 07:34 PM
#4
Short answer is yes. I dont swear by dynamic compression (DCR) but I do refer to it for a daily driver. Compression calculated from the 006 IVC to TDC. On 91 octane, I like 8.3-8.5. On 93 octane, I'll push it to 8.75. For E85, you can do more, but if you are ever stuck with no E85 available you are screwed.
There are calculators out there that you can use or when you are soeccing a cam with a vendor just ask about the DCR. Most often they will put you near 8.3, which is a good balance between safe and good throttle response on the street.
There are calculators out there that you can use or when you are soeccing a cam with a vendor just ask about the DCR. Most often they will put you near 8.3, which is a good balance between safe and good throttle response on the street.
09-09-2018, 08:07 PM
#5
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Ok. That sort of caps compression at 11.5. That in turn means 43-44 IVC for best performance and still very driveable. So on the intake side, start with 228 duration on a 110 centerline. On the exhaust side, since you have 1/4 mile goals, that means RPM and carrying past peak. If we open that exhaust valve at 54, that should work great, so we can start with 236 on the exhaust with a centerline of 116. That puts you at 228/236-113+3, 6 degrees overlap, should drive good, tune good, still run your AC etc, and run good at the track. Should hit peak power at 6300, shift around 7000 depending on your intake selection.
09-09-2018, 08:16 PM
#6
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Eric, if you have E85 available in many areas, without issue, go big. I was always the conservative guy when it comes to compression, dynamic and static. The last thing I wanted was a car that couldn’t run on pump. Enter Tony Mamo, aka engine genius. I completely understand cylinder pressure, but tony taught me how I could make it work for me, reliably, on pump at high numbers, due to efficiency. I’m 12.42 static and 10.48 dynamic....on 93 pump. Zero, repeat, zero knock on the dyno, in TERRIBLE weather, with big timing numbers. Cylinder pressure is all that matters in this arena. Period. Don’t take my word for it. Call Tony. Super nice guy who will help you spec a camshaft and setup, that works for you, not him. You’ll be glad you did.
09-10-2018, 02:27 PM
#7
Ok. That sort of caps compression at 11.5. That in turn means 43-44 IVC for best performance and still very driveable. So on the intake side, start with 228 duration on a 110 centerline. On the exhaust side, since you have 1/4 mile goals, that means RPM and carrying past peak. If we open that exhaust valve at 54, that should work great, so we can start with 236 on the exhaust with a centerline of 116. That puts you at 228/236-113+3, 6 degrees overlap, should drive good, tune good, still run your AC etc, and run good at the track. Should hit peak power at 6300, shift around 7000 depending on your intake selection.
if advanced a degree or two would any of them be close?
BTR LS1/LS2 Stage 2 Camshaft
227/234 duration @.050 lift -.614"/.576" 113+2
Tick Performance "SNS" torqueMAX Stage 2 Camshaft
Standard Lobes: 227/235 | .618"/.605" | LSA110+3
Lingenfelter GT12 Camshaft
227/235 duration @ .050 lift - .614/.621 lift 115 CL
Comp Cams LSR Camshaft 5277LRHR13, 3-bolt, grind 277LRHR13
227/235 duration @ .050 lift - .614/.621lift 113 CL
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09-10-2018, 02:45 PM
#8
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Yup. All but torquemax are comparable. Torquemax has very early IVC. Great midrange, but will not play nice with compression.
09-11-2018, 07:17 PM
#9
Ok. That sort of caps compression at 11.5. That in turn means 43-44 IVC for best performance and still very driveable. So on the intake side, start with 228 duration on a 110 centerline. On the exhaust side, since you have 1/4 mile goals, that means RPM and carrying past peak. If we open that exhaust valve at 54, that should work great, so we can start with 236 on the exhaust with a centerline of 116. That puts you at 228/236-113+3, 6 degrees overlap, should drive good, tune good, still run your AC etc, and run good at the track. Should hit peak power at 6300, shift around 7000 depending on your intake selection.
09-11-2018, 07:20 PM
#10
As if right now, I am planning to just have Advanced Induction do the cam when they do the heads, so they can match the cam to the compression. I just don't want to go too far with compression, and end up with a low 220's cam being as big as I can go.
09-11-2018, 08:08 PM
#11
TECH Senior Member
Actually matching cam to heads.... how many do that but don't.... that SHOULD??
09-22-2018, 03:06 PM
#12
I don't know anything about dynamic vs static compression. This is all of the heads/valvetrain stuff that I am thinking about:
- Bone stock 1999 LS1 short block (probably 70k miles by the time I pull the trigger)
- Not fly cutting the pistons
- AI TFS 220s, milled to whatever will work best with the cam an E52
- AI cam (whatever specs will work best with heads and E52)
- BTR .660 titanium
- 3/8 pushrods matched to heads/cam
- Scorpion roller rockers
- Johnson 2110 Slow Leakdown lifters (not really sure about lifters yet)
- Bone stock 1999 LS1 short block (probably 70k miles by the time I pull the trigger)
- Not fly cutting the pistons
- AI TFS 220s, milled to whatever will work best with the cam an E52
- AI cam (whatever specs will work best with heads and E52)
- BTR .660 titanium
- 3/8 pushrods matched to heads/cam
- Scorpion roller rockers
- Johnson 2110 Slow Leakdown lifters (not really sure about lifters yet)
09-22-2018, 03:38 PM
#14
TECH Senior Member
09-22-2018, 05:06 PM
#15
Our high lift asa is in that range also and has less advance than some allowing for better ptv with a larger valve.
With some milled 243s it made some impressive hp and tq on pump gas.
Another option there.
We may have a sale on them soon also.
Let us know!!
With some milled 243s it made some impressive hp and tq on pump gas.
Another option there.
We may have a sale on them soon also.
Let us know!!
10-09-2018, 04:17 PM
#18
Are you going to have the ability to change timing on the fly for the fuel you have in at the timel? If not it's kind of a waste, and it would be better to choose a fuel to run full time and build for that.
To expand on that. If timing is going to remain the same then you won't be getting the full benefit on all fuels, or will ping on lower octanes. For example, if you tune for the lowest octane you're going to run, and don't change timing, then there's no point in running the e fuels with higher octane. And if you tune for e85 and run 91 but don't change timing it will ping/detonate.
To expand on that. If timing is going to remain the same then you won't be getting the full benefit on all fuels, or will ping on lower octanes. For example, if you tune for the lowest octane you're going to run, and don't change timing, then there's no point in running the e fuels with higher octane. And if you tune for e85 and run 91 but don't change timing it will ping/detonate.
10-16-2018, 01:07 AM
#19
Are you going to have the ability to change timing on the fly for the fuel you have in at the timel? If not it's kind of a waste, and it would be better to choose a fuel to run full time and build for that.
To expand on that. If timing is going to remain the same then you won't be getting the full benefit on all fuels, or will ping on lower octanes. For example, if you tune for the lowest octane you're going to run, and don't change timing, then there's no point in running the e fuels with higher octane. And if you tune for e85 and run 91 but don't change timing it will ping/detonate.
To expand on that. If timing is going to remain the same then you won't be getting the full benefit on all fuels, or will ping on lower octanes. For example, if you tune for the lowest octane you're going to run, and don't change timing, then there's no point in running the e fuels with higher octane. And if you tune for e85 and run 91 but don't change timing it will ping/detonate.
11-16-2018, 10:10 PM
#20
So....bone stock LS1 bottom - I will not fly cut pistons.
Here is what I am thinking
- Flex Fuel system and tune
- AI LS1 TFS 230 heads 56cc for @12:1 compression
- AI ported LSXR 102
- something like 228/232 .650/.650 cam....probably going to Brian Tooley since AI isn't doing one off cams anymore.
Stock weight.
I want sub 11s on 345 DRs
Inputs?
Here is what I am thinking
- Flex Fuel system and tune
- AI LS1 TFS 230 heads 56cc for @12:1 compression
- AI ported LSXR 102
- something like 228/232 .650/.650 cam....probably going to Brian Tooley since AI isn't doing one off cams anymore.
Stock weight.
I want sub 11s on 345 DRs
Inputs?
Last edited by FCar2000TA; 11-16-2018 at 11:02 PM.