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Old 01-31-2016, 08:09 PM   #41
kr3w108
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Default Re: Best cams for ported head turbo, 800+hp range

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Originally Posted by REALDEAL View Post
Wondering why you you didnt elect to go with the pro156 program.
K mod has helped me in the past , i figured i would give them some business. give them a review. so we shall see.
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Old 02-01-2016, 12:11 PM   #42
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Default Re: Best cams for ported head turbo, 800+hp range

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...I will recheck all constants (material, geometry) in the fastener calculation model I took out of property tables. Maybe intrution amount assumption of rod material is too big...I will come back with it.
Did check the model constants like yield strength, spring rate of rod and bolt and so on. Beside some small corrections (ARP bolts has higher YS as typical values for same material found in books for e.g. 8740 Chrome Moly) nothing has changed.

Long story short, the 3/8" ARP2000 rod bolts are at their limits at 11.000 rpm, safety factor against yield (cold) is at 1.47 when bolts are torqued with 86 Nm, which is 12 Nm higher than recommended by ARP -> will likely fail

Going with 3/8" ARP625+ changes the story: 1.74 and 86 Nm, which is 2 Nm lower than recommended (according their cataloque + extrapolation for 260.000 psi material) -> will likely not fail

Going with 7/16" ARP2000 will better safety against fatique, but not yield, torque will be 20 Nm below there recommended 122 Nm. A bit surprisingly, but 7/16" is just an improvement in fatique (1.97 vs 1.32) and in yield when it has the 625+ stuff material.

Another point I found in the book (Maschinenelemente, Band 1, G. Nieman), yield strength reduction comes to play above 150 C, where they recommend to use the time bounded fatique of 10.000 h or so...so, according that yield strength can be taken as stated (= no reduction due to temp.).

Concluding, I still would at least install ARP625+ to reduce the risk of bending valves and other not so nice stuff. Joe would have used A1 7/16" (up to 280.000 psi...must be brittle stuff )

BTW, I strongly not recommend to use ARP's design approach for fastener load! Using that equation (= sort of centripetal force equation) will underrate the fastener load by about a factor of > 0.5. Firstly it is the wrong equation because of piston movement isn't sinusoidal and secondly the rod weight can't be divided by a third because around TDC piston and rod weight center are in first approximation inline.

So, what you will do now kr3w108? Still same way? ...

Markus

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Old 02-01-2016, 07:37 PM   #43
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Default Re: Best cams for ported head turbo, 800+hp range

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Originally Posted by LotusElise View Post
Did check the model constants like yield strength, spring rate of rod and bolt and so on. Beside some small corrections (ARP bolts has higher YS as typical values for same material found in books for e.g. 8740 Chrome Moly) nothing has changed.

Long story short, the 3/8" ARP2000 rod bolts are at their limits at 11.000 rpm, safety factor against yield (cold) is at 1.47 when bolts are torqued with 86 Nm, which is 12 Nm higher than recommended by ARP -> will likely fail

Going with 3/8" ARP625+ changes the story: 1.74 and 86 Nm, which is 2 Nm lower than recommended (according their cataloque + extrapolation for 260.000 psi material) -> will likely not fail

Going with 7/16" ARP2000 will better safety against fatique, but not yield, torque will be 20 Nm below there recommended 122 Nm. A bit surprisingly, but 7/16" is just an improvement in fatique (1.97 vs 1.32) and in yield when it has the 625+ stuff material.

Another point I found in the book (Maschinenelemente, Band 1, G. Nieman), yield strength reduction comes to play above 150 C, where they recommend to use the time bounded fatique of 10.000 h or so...so, according that yield strength can be taken as stated (= no reduction due to temp.).

Concluding, I still would at least install ARP625+ to reduce the risk of bending valves and other not so nice stuff. Joe would have used A1 7/16" (up to 280.000 psi...must be brittle stuff )

BTW, I strongly not recommend to use ARP's design approach for fastener load! Using that equation (= sort of centripetal force equation) will underrate the fastener load by about a factor of > 0.5. Firstly it is the wrong equation because of piston movement isn't sinusoidal and secondly the rod weight can't be divided by a third because around TDC piston and rod weight center are in first approximation inline.

So, what you will do now kr3w108? Still same way? ...

Markus
Yes i will use the the ARP 2000's. The recommended stretch is .058-.062 I plan to use .060 as my magic number for the clamping force. The motor will not be reved more than 11k , will most likely just take it to 10.5k rpm.

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Old 02-04-2016, 08:59 AM   #44
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Default Re: Best cams for ported head turbo, 800+hp range

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Hi DRAG, would you mind to share what would be a good valve spring for example?

Thanks in advance guys.

Markus
Generally speaking, if you stick to the spring brands that are used in high end racing engines then you are on the right track. PSI, PAC, etc. It takes decent seat pressure, good consistent opening pressure, and a good material that will last to handle the wild 2-step rev limiters and 11,000+ rpm that is turned on these big power 180mph 1/4 mile passes.

In the fastest K series turbo cars out there, we run our PSI Pro Stock spring...that includes TAE on their 8.2 car, Speedfactory on their 8.4 car, etc. We use a heavy PAC spring from Ferrea in Fast Guy's car that he has been very happy with...2 seasons now with no engine issues at that power level is pretty impressive. Skunk2 HP springs are also a PAC as far as I know, and their newer HP spring has sufficient pressure for these cars if installed properly.

The $350 springs that some guys install...that's the guys floating valves and having failures throughout the season. There is also horsepower in keeping that valve in control. If you are bouncing the valve on the seat when it closes, then you lose cylinder pressure up into the intake and causing all sorts of pressure waves back up into the intake. That hurts power.

Here is a tip for guys in the class that may save you an engine (competitor engine builders can thank me in person at the track). Soften up the 2 step and keep your stuff off the rev limiter! That oscillates the valve spring and beats the shit out of them...wears them out in a couple passes!! I know the fireballs are cool and the 2 steps sound awesome, but its REALLY hard on valve springs. If you can limit your time there, you will have longer lasting engines. Having a competent driver will save engines.
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Old 02-04-2016, 10:50 AM   #45
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Default Re: Best cams for ported head turbo, 800+hp range

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...if you stick to the spring brands...PSI, PAC, etc....will last to handle the wild 2-step rev limiters and 11,000+ rpm...
Thanks DRAG for the insight . My application isn't that hard to spring spec , it's a more mild hill climb race spec (9.5 krpm designed rev limit, 8.5 krpm peak power) with a shifted emphasis on friction optimization and covering safe valve dynamic up to 9.8 krpm. Had oviate beehive springs in mind, which has a nice relation between pressure and valve control ability (valve efficiency), e.g. Ferrea's 14 mm lift covering beehive spring. Those spring propably don't cover drag racer's engine speed demand?

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...Soften up the 2 step and keep your stuff off the rev limiter...fireballs...
Seems to be common technique, I don't know...does it mean first step ignition of, fuel flow still on = fireball and second step some rpm's higher fuel cut finally...bouncing in between that two points when keeping "end" gear shortly before quarter mile is finished due to "hard" (not to say to short) gear ratio design?
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Old 02-04-2016, 11:53 AM   #46
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Default Re: Best cams for ported head turbo, 800+hp range

Their beehive will float valves at that rpm. Beehives are a great spring design, but that one doesn't have enough pressure. You need to be looking at the S10100 spring as a minimum, and I would consider something with more pressure if the rpm will hold there longer than short bursts.
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Old 02-04-2016, 12:27 PM   #47
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Default Re: Best cams for ported head turbo, 800+hp range

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Their beehive will float valves at that rpm. Beehives are a great spring design, but that one doesn't have enough pressure. You need to be looking at the S10100 spring as a minimum, and I would consider something with more pressure if the rpm will hold there longer than short bursts.
Thanks DRAG, I appreciate your valuable time very much! Engine torque is designed to fall of hard at 8.5 krpm, about 22 ftlb/0.5 krpm (flywheel), therefore operation range in race will be up to 8.9-9.0 krpm max.. The rotaring assembly is designed to be capable of 9.5 krpm to give misshift safety and 9.8 for valve train to prevent fatal damage form engine when driver did a misshift. Finally the engine won't rev continious beyond 8.6 krpm (power falls already off) and only for accelerating it will touch the 8.9-9.0 krpm margine. Was in the hope to be able to utilize the beehive spring efficiency ...

It is a mild build engine as the money pit's are all around the engine too .

Markus
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Old 02-04-2016, 01:08 PM   #48
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Default Re: Best cams for ported head turbo, 800+hp range

I think the S10100 is perfect for your application. Do you have a thread that has some details of your engine?
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Old 02-04-2016, 07:10 PM   #49
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Default Re: Best cams for ported head turbo, 800+hp range

Im running the ferrea 155lb Valve springs in my setup this year...
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Old 02-04-2016, 11:47 PM   #50
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Default Re: Best cams for ported head turbo, 800+hp range

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I think the S10100 is perfect for your application. Do you have a thread that has some details of your engine?
Thanks DRAG. If you are interested check details out

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Old 02-05-2016, 12:01 AM   #51
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Default Re: Best cams for ported head turbo, 800+hp range

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Thanks DRAG. If you are interested check details out

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Old 02-05-2016, 02:47 AM   #52
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Default Re: Best cams for ported head turbo, 800+hp range

As OP did decide for Prayoonto stage 2 cams with specification according to website:
  • ADV ____ duration 305/300 ("___" = not clear)
  • cam [email protected] of 235/230 ("cam" definition stated by SickSilver_ep3)
  • Lift .530"/.470" or 13.46/11.94 mm
and we both (kr3w108 and I) unfortunately don't know the valve [email protected]", I would really appreciate to know it: IN low and high, EX low and high speed. This would enable one to compare these with other stuff of the cam market.

Does anyone know the valve duration (stock rocker rollers) with those cams at 0.05" (0 lash)? I would appreciate that knowledge.

Markus
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