TT 408 numbers
TT 408 numbers I'm curious to hear from the Twin Turbo 408 owners on this board. What kind of numbers are you making and for how long? head lifting issues/concerns/things you would have changed etc.
I'm researching some potential options for increased power later down the road and just wanting to hear from people. I know the 6 bolt head is the real answer but i cant help but ask what you guys are making.
Also what effect does nitrous have on the motor at these levels/presssures etc.? A 200 shot seems like the quick awnser but im sure has its own set of BS problems
I'm researching some potential options for increased power later down the road and just wanting to hear from people. I know the 6 bolt head is the real answer but i cant help but ask what you guys are making.
Also what effect does nitrous have on the motor at these levels/presssures etc.? A 200 shot seems like the quick awnser but im sure has its own set of BS problems
Last edited by oscs; Apr 14, 2015 at 05:08 PM.
Not sure. I know there are quite a few though. Unfortunatley the type of racing (halfmile/mile/roll) I intend on doing is more of a numbers game.
[QUOTE=oscs;18757522]Not sure. I know there are quite a few though. Unfortunatley the type of racing (halfmile/mile/roll) I intend on doing is more of a numbers game.[/QUOTEp]
I believe skinnier went 174 in 1/4 but is also using the ARP625 studs for extra clamp.
In 1/8 mile people have gone 150plus with 4 bolt heads but no chance of that living in 1/2 mile and beyond. Your going to face issues with what you want to do and 4 bolt heads. The duration of abuse is so much longer.
I believe skinnier went 174 in 1/4 but is also using the ARP625 studs for extra clamp.
In 1/8 mile people have gone 150plus with 4 bolt heads but no chance of that living in 1/2 mile and beyond. Your going to face issues with what you want to do and 4 bolt heads. The duration of abuse is so much longer.
Here is his thread:
https://ls1tech.com/forums/forced-in...uilt-year.html
May not be 100% applicable to what you are doing, but it may be a good starting point.
https://ls1tech.com/forums/forced-in...uilt-year.html
May not be 100% applicable to what you are doing, but it may be a good starting point.
[QUOTE=asubennett;18757583]
Yup, This is my fear.
Not sure. I know there are quite a few though. Unfortunatley the type of racing (halfmile/mile/roll) I intend on doing is more of a numbers game.[/QUOTEp]
I believe skinnier went 174 in 1/4 but is also using the ARP625 studs for extra clamp.
In 1/8 mile people have gone 150plus with 4 bolt heads but no chance of that living in 1/2 mile and beyond. Your going to face issues with what you want to do and 4 bolt heads. The duration of abuse is so much longer.
I believe skinnier went 174 in 1/4 but is also using the ARP625 studs for extra clamp.
In 1/8 mile people have gone 150plus with 4 bolt heads but no chance of that living in 1/2 mile and beyond. Your going to face issues with what you want to do and 4 bolt heads. The duration of abuse is so much longer.
Yup, This is my fear.
Here is his thread:
https://ls1tech.com/forums/forced-in...uilt-year.html
May not be 100% applicable to what you are doing, but it may be a good starting point.
https://ls1tech.com/forums/forced-in...uilt-year.html
May not be 100% applicable to what you are doing, but it may be a good starting point.
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I’d think the low compression stuff would really shine if head clamping force is an issue, esp. in a 1/2 mile event. With low compression, you could make the same power with less overall cylinder pressure. IE less clamping force would be needed.
For example, let's say 28:1 is the highest level safely achievable before detonation creeps in on 2 identical engines where compression ratio is the only difference.
12:1 engine being boosted 20psi gives 28:1 effective compression.
7:1 engine being boosted 45psi gives 28:1 effective compression.
The lower compression engine would have roughly 70% greater power potential at the same effective compression.
Info and math behind the theory here...
http://www.modularfords.com/threads/...boost-pressure
For example, let's say 28:1 is the highest level safely achievable before detonation creeps in on 2 identical engines where compression ratio is the only difference.
12:1 engine being boosted 20psi gives 28:1 effective compression.
7:1 engine being boosted 45psi gives 28:1 effective compression.
The lower compression engine would have roughly 70% greater power potential at the same effective compression.
Info and math behind the theory here...
http://www.modularfords.com/threads/...boost-pressure
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Launching!
Joined: Oct 2006
Posts: 289
Likes: 0
I'm not sure I buy into his math/reasoning...and he mentions it right in his first paragraph: "the cylinder pressure at the end of the compression stroke (prior to ignition) goes up exponentially with an increase in static compression ratio, versus a linear increase with boost pressure." The boost pressure is 20-45psi and that is with the intake valve open. The valve closes and ignition happens. Cylinder pressure goes to over 300psi. How can the 20-45psi be lifting the heads and the 300psi not? With more boost you should get more fuel and air and more cylinder pressure after ignition (and more torque). I think that is the real key...not any extra boost PSI. The only way to make more torque is more cylinder pressure (regardless of measured boost).
I’d think the low compression stuff would really shine if head clamping force is an issue, esp. in a 1/2 mile event. With low compression, you could make the same power with less overall cylinder pressure. IE less clamping force would be needed.
For example, let's say 28:1 is the highest level safely achievable before detonation creeps in on 2 identical engines where compression ratio is the only difference.
12:1 engine being boosted 20psi gives 28:1 effective compression.
7:1 engine being boosted 45psi gives 28:1 effective compression.
The lower compression engine would have roughly 70% greater power potential at the same effective compression.
Info and math behind the theory here...
http://www.modularfords.com/threads/...boost-pressure
For example, let's say 28:1 is the highest level safely achievable before detonation creeps in on 2 identical engines where compression ratio is the only difference.
12:1 engine being boosted 20psi gives 28:1 effective compression.
7:1 engine being boosted 45psi gives 28:1 effective compression.
The lower compression engine would have roughly 70% greater power potential at the same effective compression.
Info and math behind the theory here...
http://www.modularfords.com/threads/...boost-pressure
Staging Lane
Joined: Jul 2012
Posts: 86
Likes: 0
From: Detroit, MI
I don't agree with that cr to boost theory either, but this statement is also wrong. If you look at a P-V diagram(or cyl pressure with respect to crank angle), power generated is the area underneath the curve. With proper hardware setup, calibration and fuel choice you can lower the peak pressure that is reached in the cylinder while actually increasing the area under the curve, thus increasing power output. It is really an optimization problem, maximizing power while minimizing peak pressure, and there are thousands of people who work on it everyday, I would follow what they are doing.
I'm not making any specific HP # VS head lift claims, just throwing out the theory.
"Bear77" put it this way...
As the 7:1 compression motor is 5 compression points less, it is already down 16% power potential on the 12:1 compression motor. Since the 7:1 compression motor needs 25psi more than the 12:1 compression motor to see the same effective compression it is up 87% in power potential. Taking the 16% compression loss away from the 7:1 motor leaves it with 71% greater power potential at the exact same 28:1 effective compression. In essence it takes 5psi more boost at any given point to make the same power with 7:1 compression than with 12:1 compression and each psi more boost from there is pure profit!
Last edited by Forcefed86; Apr 14, 2015 at 11:57 AM.
Launching!
Joined: Oct 2006
Posts: 289
Likes: 0
Lower compression ratio also has a negative impact on HOW the pressure is applied to the piston and the crankshaft. I went for a walk at lunch and was thinking about this (I really need a life...LOL). The higher the compression ratio, the quicker the expansion on the down-stroke. This is important because you want your pressure acting on the piston in the first few degrees (15-20 ATDC is the magical area I believe) because it gives you better turn on the crank. The first internal combustion engines running off of Otto's cycle were close to 1:1 compression ratio. The pressure wasn't used up until BDC (not good!). This is the reason why manufacturers (boosted or NA) are wanting higher and higher compression ratios.
NoorJ is correct...it is area under the curve and I wasn't thinking about that. We also completely derailed this thread! Sorry OP!
NoorJ is correct...it is area under the curve and I wasn't thinking about that. We also completely derailed this thread! Sorry OP!
Why not? You're not just looking at peak pressure, you're looking at average pressure over the entire stroke of the piston. Boost is more efficient at making power over the entire stroke than raising SCR, period. Otherwise we could build a 28:1 compression engine and leave out the turbo. The more boost you run, the more average power over the entire stroke you'll make. So by lowering the SCR and raising boost, I'd think it would be possible to have the same or less peak pressure, and maintain more average power over the entire piston stroke?
I'm not making any specific HP # VS head lift claims, just throwing out the theory.
"Bear77" put it this way...
I'm not making any specific HP # VS head lift claims, just throwing out the theory.
"Bear77" put it this way...
Your theory would imply you could run a 2:1 compression ration and 50lbs of boost from a 106mm Turbo and have less cylinder pressure then same turbo at 20lbs boost with a 10:1 motor therefore the motor will live with 4 bolt heads.
It's not a linear analysis. Diminishing returns are had on both sides. Kind of a bell curve in my view related to CR and Boost. Too low - bad. Too High - bad. Something in the sweet middle just right dependent upon set up and desired outcome. CR is just a way to quickly compress the mixture. If the fuel is amazing CR doesn't matter as much as it gets higher. Low CR is a bandaid and for a max effort combo, far less than ideal.
Go 6 bolt head and block and don't look back for 1mile racing.
Not disagreeing with your theory, just saying horsepower is horsepower and torque is torque, given the same cubic inches.
Your theory would imply you could run a 2:1 compression ration and 50lbs of boost from a 106mm Turbo and have less cylinder pressure then same turbo at 20lbs boost with a 10:1 motor therefore the motor will live with 4 bolt heads.
It's not a linear analysis. Diminishing returns are had on both sides. Kind of a bell curve in my view related to CR and Boost. Too low - bad. Too High - bad. Something in the sweet middle just right dependent upon set up and desired outcome. CR is just a way to quickly compress the mixture. If the fuel is amazing CR doesn't matter as much as it gets higher. Low CR is a bandaid and for a max effort combo, far less than ideal.
Go 6 bolt head and block and don't look back for 1mile racing.
Your theory would imply you could run a 2:1 compression ration and 50lbs of boost from a 106mm Turbo and have less cylinder pressure then same turbo at 20lbs boost with a 10:1 motor therefore the motor will live with 4 bolt heads.
It's not a linear analysis. Diminishing returns are had on both sides. Kind of a bell curve in my view related to CR and Boost. Too low - bad. Too High - bad. Something in the sweet middle just right dependent upon set up and desired outcome. CR is just a way to quickly compress the mixture. If the fuel is amazing CR doesn't matter as much as it gets higher. Low CR is a bandaid and for a max effort combo, far less than ideal.
Go 6 bolt head and block and don't look back for 1mile racing.
2:1 is taking it a bit far, anything under 6.5:1 Isn’t practical for most racing applications. Not sure how you can say SCR/DCR doesn’t matter. Even with “good fuel” it matters… a lot!
HP is not HP when one method makes power more efficiently at the same peak Cyl pressures on an otherwise identical engine. Lower CR (if used properly) is not a band-aid for a max effort combo. Too many think this way. Not only does it allow for more boost but it also is increasing the size of the CC. (Think Lady Finger VS M80) The only thing you are giving up is response. In the non class limited drag racing world it is easy to work around this (to a point anyway) as you can dial up the boost before the launch. Top fuel engines are around 6.5:1 for example. The reason you don’t see the low compression stuff is because very few classes are truly “max effort”. With all the restrictions/rules in place the low CR stuff can’t be competitive in most turbo classes.
While I’m not suggesting we all run 6:1 engines, I am saying low CR engines have more power potential and *may be* more beneficial in a longer race… ½ mile, mile, salt flats… etc. if head clamping force is a major concern.
In a longer run you are generating more heat in the system. You need to greatly increase cooling systems and watch the tune. As chamber gets hotter it becomes more detonation prone. A more conservative tune is required imo.
Look at some of the landspeed racing stuff. Cooling is important but sustaining wot for so long is way different than an 8 sec drag race.
But i have seen two personal friends use 6.0 block based builds with 4 bolt oem heads run 8.3-8.6 at 165-167 mph in 3400-3500 ish lb setups
One is a Ly6 dyno'd 1052 thru th400. Other is a 408 dyno 1091 on 20 lbs but 8.3 run was on 23 so its closer to 1150 whp.
Ly6 hasnt had issues. The 408 is lifting heads. Used arp studs and still pushed alittle. Had o ring block and heads but machine shop screwed it up i guess and it didnt work. Still pushed.
Some have luck some dont. Tune is important too. Too rapid of a cylinder pressure rise could upset things. Controlled rise over entire stroke can extract power without necessarily a high peak pressure
My sbc is a lower comp type setup, 9:1 but decent cam it cranks low pressure. Guess its why i can run 25+ psi on just 93 oct and not have issues. Interesting to see a test of two identical setups but one 8:1 and one 10:1 and see what happens, as long as fuel isnt a detonation concern.
Look at stock ls7 with boost. 11:1 run 5-6 psi somewhat safe and make 650 whp lets say. Any higher boost on pump gas things become a concern. Throw in low comp pistons you can run higher boost now and make more power.
Look at some of the landspeed racing stuff. Cooling is important but sustaining wot for so long is way different than an 8 sec drag race.
But i have seen two personal friends use 6.0 block based builds with 4 bolt oem heads run 8.3-8.6 at 165-167 mph in 3400-3500 ish lb setups
One is a Ly6 dyno'd 1052 thru th400. Other is a 408 dyno 1091 on 20 lbs but 8.3 run was on 23 so its closer to 1150 whp.
Ly6 hasnt had issues. The 408 is lifting heads. Used arp studs and still pushed alittle. Had o ring block and heads but machine shop screwed it up i guess and it didnt work. Still pushed.
Some have luck some dont. Tune is important too. Too rapid of a cylinder pressure rise could upset things. Controlled rise over entire stroke can extract power without necessarily a high peak pressure
My sbc is a lower comp type setup, 9:1 but decent cam it cranks low pressure. Guess its why i can run 25+ psi on just 93 oct and not have issues. Interesting to see a test of two identical setups but one 8:1 and one 10:1 and see what happens, as long as fuel isnt a detonation concern.
Look at stock ls7 with boost. 11:1 run 5-6 psi somewhat safe and make 650 whp lets say. Any higher boost on pump gas things become a concern. Throw in low comp pistons you can run higher boost now and make more power.
In a longer run you are generating more heat in the system. You need to greatly increase cooling systems and watch the tune. As chamber gets hotter it becomes more detonation prone. A more conservative tune is required imo.
Look at some of the landspeed racing stuff. Cooling is important but sustaining wot for so long is way different than an 8 sec drag race.
But i have seen two personal friends use 6.0 block based builds with 4 bolt oem heads run 8.3-8.6 at 165-167 mph in 3400-3500 ish lb setups
One is a Ly6 dyno'd 1052 thru th400. Other is a 408 dyno 1091 on 20 lbs but 8.3 run was on 23 so its closer to 1150 whp.
Ly6 hasnt had issues. The 408 is lifting heads. Used arp studs and still pushed alittle. Had o ring block and heads but machine shop screwed it up i guess and it didnt work. Still pushed.
Some have luck some dont. Tune is important too. Too rapid of a cylinder pressure rise could upset things. Controlled rise over entire stroke can extract power without necessarily a high peak pressure
My sbc is a lower comp type setup, 9:1 but decent cam it cranks low pressure. Guess its why i can run 25+ psi on just 93 oct and not have issues. Interesting to see a test of two identical setups but one 8:1 and one 10:1 and see what happens, as long as fuel isnt a detonation concern.
Look at stock ls7 with boost. 11:1 run 5-6 psi somewhat safe and make 650 whp lets say. Any higher boost on pump gas things become a concern. Throw in low comp pistons you can run higher boost now and make more power.
Look at some of the landspeed racing stuff. Cooling is important but sustaining wot for so long is way different than an 8 sec drag race.
But i have seen two personal friends use 6.0 block based builds with 4 bolt oem heads run 8.3-8.6 at 165-167 mph in 3400-3500 ish lb setups
One is a Ly6 dyno'd 1052 thru th400. Other is a 408 dyno 1091 on 20 lbs but 8.3 run was on 23 so its closer to 1150 whp.
Ly6 hasnt had issues. The 408 is lifting heads. Used arp studs and still pushed alittle. Had o ring block and heads but machine shop screwed it up i guess and it didnt work. Still pushed.
Some have luck some dont. Tune is important too. Too rapid of a cylinder pressure rise could upset things. Controlled rise over entire stroke can extract power without necessarily a high peak pressure
My sbc is a lower comp type setup, 9:1 but decent cam it cranks low pressure. Guess its why i can run 25+ psi on just 93 oct and not have issues. Interesting to see a test of two identical setups but one 8:1 and one 10:1 and see what happens, as long as fuel isnt a detonation concern.
Look at stock ls7 with boost. 11:1 run 5-6 psi somewhat safe and make 650 whp lets say. Any higher boost on pump gas things become a concern. Throw in low comp pistons you can run higher boost now and make more power.
Right I understand all this. I'm pretty sure my 9:5.1 370 is making 1k already. Lower CR pistons are not going to get me to 1300whp.
I am by no means saying a 408 is the awnser as I honestly don't even like the idea, never have. I'm simply listening to ideas from guys that make/hold these numbers.