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Discussion Starter #1 (Edited)
Whats up guys, i current am in the middle of rebuilding my motor for next year. I am currious as to what you guys think is the best cam to support my motor. currently have ipskt1 cams , was looking into maybe kt2's or some prayoonto stg 2's or stg 3's ?

Previous setup: K20a2 , car made 761/[email protected] psi
stock ported head
excessive center feed intake
90mm Throttle body
PTE6766 t4
IPS KT-1's
11:1 cpr
86.5mm bore

New setup i am looking to change up a few things on the car to make more power and be more efficient. power goal is whatever the turbo will make.... rated at 950hp

New setup: k20a2
Kmod stg.2 ported head **Flows 355 cfm @ .600 lift **
ported excessive center feed
90mm Throttle body
PTE6766 t4
11:1 cpr
88mm bore
 

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Arouse the DAMPFHAMMER!
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Hi kr3w108,

nice power aim :D. The following is just my :twocents: as I see in the setup some disharmoniosly items. So please take it not as offend or as smartass talking, maybe as an inspiration to think the one or two development directions.

...Kmod stg.2 ported head **Flows 355 cfm @ .600 lift **
Bigger valves too? At high boost the valve cross section easly get into cram limit...the K20 port isn't main opstacle, the prior one limit is the valve cross section and shape.
...11:1 cpr...
What fuel rating you are using? If not oxygenated 50 % MFB will be retarded...maybe better to reduce to static CR of 9:1 or 9.5:1 for optimized 50 % MFB location. It would also help to gain with lower duration cams. A good indicator of the location of 50 % MFB is given by the ignition timing and some assumptions for ignition delay and combustion duration.
...88mm bore...
You will surely gain from a lower CR...44 mm has to be managed by the flame speed...about 1 °ca more 10-90 % MFB duration :D

I wouldn't go the high CR path, which needs cams of longer duration, as due to losses and heat handling at the turbine you have to wet your combustion too much to control the turbine temperature and loose combustion velocity...better going with a lower static CR, earlier combustion, bit higher lambda -> higher combustion velocity and a higher engine efficiency and power potential.

:twocents:

Markus
 

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Discussion Starter #6
I have an 88mm bore now do to me miss shifting back in December and bending all the valves in the head . 2 broke off and gouged the cylinder walls . Had to bore it to make it right again .
 

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Arouse the DAMPFHAMMER!
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Discussion Starter #8
Not sure what MOZ stands for lol , valves are going to be std size , bought them before I decided to port the head . Might go bigger later on. The sleeves are golden eagle .
 

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Arouse the DAMPFHAMMER!
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Not sure what MOZ stands for lol , valves are going to be std size , bought them before I decided to port the head . Might go bigger later on. The sleeves are golden eagle .
MOZ = motor octane number...sorry was an acronym used in my mother language, you guys say MON :D.

I just checked Prayoonto stage 3 specification and I have to correct myself, as I let myself misleading of the stage rating. The are specified as intake 245 °[email protected]" and exhaust 240 °[email protected]" which is in the range of the ITR cams, but with an higher lift. This change that thing a bit :D...so Prayoonto stage 3 could be even worther than ITR cams.

Prayoonto stage 2 has a lower lift on the exhaust side with a bit shorter duration. The stage 4 of Prayoonto is a pure NA cam, too long duration for boosted applications. So I would conclude the following...


...for your build aim (= 42.7 bar [email protected] krpm :new_slayer:) I would prefer the Prayoonto stage 3 over the ITR cam, because of the similar duration but the higher and faster lift up.



Sorry for my misinformation...but always great to learn more :D
 

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Discussion Starter #10 (Edited)
I have been doing some looking around and cant really find any clear data to support what cam is better, everyone on here likes to argue about cams. I have seen similar setups make around the same power level that i made with kt1's. i have also seen some 2.4l motors make a little more power with the kt1's nothing too impressive tho. I have seen folks making decent power with the pray 2's which is a similar spec to the ipskt2's . The 2.4 motors seem to react a little better with the pray 3's . I spoke with norris about which cams he would suggest for my setup and he insisted i stay with the pray stg 2's. Says that the stage 3' are for motors reving to atleast 10.5k rpm. Here is a few specs on the cams mentioned.

The kt1's
Intake - duration (lift)

low speed lobe: 253 (9.25mm)
high speed lobe: 285 (12.7mm)

Exhaust - duration (lift)

low speed lobe: 246 (8.10mm)
high speed lobe: 278 (11.25mm)

the kt2's
Intake - duration (lift)

low speed lobe: 280
high speed lobe: 302

Exhaust - duration (lift)

low speed lobe: 273
high speed lobe: 295


Prayoonto stg 2's

ADV Duration 305/300
Duration @.050 235/230
Lift .530"/.470" 13.46/11.94

Prayoonto stg 3's

ADV Duration - 315/310
Duration @.050 - 245/240
Lift - 13.4/13.1

As you can see from the specs , the kt1's are a very small lift cam. The kt2's are a much bigger lift vs the kt1's. The pray stg 2's is very similar to the kt2 but a touch bigger in lift and way bigger than the kt1's. I can see why most people prefer the pray 2's over kt1s. As far as the pray stg 3 cams go they are a really big cam and will require you to rev to the moon just to make the power they are designed for.

From looking at specs and from what norris has said i might pick up a set of the pray 2s. That should be plenty of cam for what i am trying to accomplish. My motor will only be reving to around 10.5. Now these are not the only cams that i am considering..
 

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Call Luke and ask!

A good flowing NA cam makes a good flowing turbo cam. At high boost pressures there is a positive pressure differential across the engine. So a 'big' cam will become even 'bigger'. Hence, recommendations to run smaller cams for turbos. With a turbo a bigger cam will hurt low end more than it will improve the top end...

i ran a stage 4-type cam with an 83mm turbo (smaller than yours). It was good for 610whp @23psi on C16.

Anton

Anyone have feedback on the 4pistons outlaw cam for turbo cArs?
 

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Discussion Starter #13
Call Luke and ask!

A good flowing NA cam makes a good flowing turbo cam. At high boost pressures there is a positive pressure differential across the engine. So a 'big' cam will become even 'bigger'. Hence, recommendations to run smaller cams for turbos. With a turbo a bigger cam will hurt low end more than it will improve the top end...

i ran a stage 4-type cam with an 83mm turbo (smaller than yours). It was good for 610whp @23psi on C16.

Anton
Ive Emailed luke at 4piston , waiting on a reply. Now as far as big almotor cams go, ive heard from a few people that having to much overlap is a bad thing when boosted. To much overlap will have to much pressure build up and start to push out the intake . So a decent lift short duration cam is optimum ....
 

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I repeat, CALL Luke and ask. Usually get better luck of reaching him. :)

There is so much BS on this forum.. .and so many experts with sour cream for brains...

You are talking about reversion, below. Tell me how when there is 30 psi of pressure in the intake and 15 psi of (back-) pressure in the exhaust, the air will flow from 15 psi to 30 psi i.e. against the pressure gradient???
.. and the rivers flow up hill??? With high(er) boost, there is a positive pressure gradient across the engine. This is not the case with lower boost and smaller turbos or Naturally Aspirated (NA) cars.

The problem is the opposite. With high overlap, you will blow air and fuel out into the exhaust. It will get hot. It will spool the turbo faster!!! It may get too hot or backfire at low revs.... At lower boost levels it will reverse and flow exhaust into the intake and idle and run badly. This is the case of with a NA engine at idle and off idle with high-lift cam, also. So no difference.

Why have overlap on a cam at all?

Cams and valve timing is the most complex part of the motor. There are 4 different scenarios:

1. NA. Overlap, intake and exhaust can be tuned in such a way that the inertia of moving air will create a slightly higher pressure in the intake and a small vacuum in the exhaust. This will create maybe a 2 to 4 psi pressure gradient in a very narrow RPM range.

2. Supercharging almost always has a positive pressure gradient on the engine. Some charge tuning as in (1) still applies. Also air/fuel blowing into exhaust applies. Street cams go conservative and reduce overlap, give up the charge-tuning effect (as in 1). Look at grad cars with superchargers, they run a lot of overlap...

3. Low pressure turbocharging has a very narrow range where the pressure gradient is positive, as the turbine chokes the motor at high end. The charge tuning is offset by high back-pressure and overlap would not be good.


4. Hogh-pressure (big turo and turbine, like yours) will create a positive gradient across the motor at over 15 psi boost al the way up the rev range, until the turbine will become a restriction. Overlap is good because there is a charging effect, even more so with more air mass, and better flow across the engine at high RPM where the intake/exhaust events are shorter in duration (but still need to fill same cylinder volume with more air and fuel). Larger can will seem even larger with a turbo i.e.move torque and power up the RPM range. Again, it all depends on what you have and what you want to achieve. A Stage 4 cam would be a great 7000 to 11,000RPM cam, but would suck at 4000. A turbo cam may work in 4500 to 8500 range and have OK idle. What are you after? A Stage 4 will make much more power, but at the very top. Not to mention that VTC helps....

Above, is a very simplistic explanation.

Listen to less people with sour cream for brains on this forum and call the experts that build these engines every day. Serious motor deserves serious advice.

Anton


Ive Emailed luke at 4piston , waiting on a reply. Now as far as big almotor cams go, ive heard from a few people that having to much overlap is a bad thing when boosted. To much overlap will have to much pressure build up and start to push out the intake . So a decent lift short duration cam is optimum ....
 

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Arouse the DAMPFHAMMER!
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There is so much BS on this forum..
LOL :D...let's have a look at it:

Tell me how when there is 30 psi of pressure in the intake and 15 psi of (back-) pressure in the exhaust, the air will flow from 15 psi to 30 psi i.e. against the pressure gradient???
Not at scavenging phase Anton, where pressure drop effects mixture flow through the chamber (scavenging). I guess he was talking about ramming phase at the end of inlet duration. The reflected wave comes back from the runner inlet (at plenum) and idealy arrives at inlet valve when its get closed.

Now, inlet cam opening timing has some needs for VE production, also inlet cam closing timing too. As the cam lobe isn't flexible like rubber, compromises has to be done. One is, the higher the engine speed, the better is to retard the cam (less scavenging) for better ramming as speed of sound doesn't change but the opening duration timeslot. So the reflected air wave increasingly comes "later" when engine speed increases, because valve opening duration gets time scale based shorter. Therefore longer duration cams produce better VE at higher engine speeds, you mentioned that, I will get to that later.

Same physics for NA and TC, just different system requirements. If duration is to long for the choosen engine speed range, it could happen that pressure wave comes back for ramming, but the intake valve is still open and the pressure wave from the up coming piston push some mixture out back into the manifold. So, it could be that cam duration is too big for the choosen engine speed range, it just depends on the system surrounding (displacement, turbine map, compressor map, cam duration, CR, ignition timing, lambda, valve size, head flow, and so on).

So maybe an internal combustion engine is a bit more complex as a river, not saying a river isn't complex :wink:

A Stage 4 cam would be a great 7000 to 11,000RPM cam, but would suck at 4000.
:up:. As I said I will come back to that. But did you see his setup? When a Prayoonto stage 4 for begin to make fun, he should be on the way to press the clutch. Maybe a Prayoonto stage 3 would help, depending on the application (circuit, drag, dyno numbers :wink:, daily driving, ...) which is not mentioned yet by kr3w108.

1. NA. Overlap, intake and exhaust can be tuned in such a way that the inertia of moving air will create a slightly higher pressure in the intake and a small vacuum in the exhaust. This will create maybe a 2 to 4 psi pressure gradient in a very narrow RPM range.
Thats interesting :D. Try to calculate the velocity over the valve with the isentropic equation with that tiny pressure drop, the air molecules will may laugh, depending on overlap duration and engine speed :D, running from in to ex at those pressure drop.


Above picture shows the crank angle related pressure at inlet (blue) and outlet (red) valve, and in green the cylinder pressure in the region of cam overlap (TDC = 360 °ca). Dashed lines shows mass flow of in and ex. Pressure drop during scavenging phase of the shown example is about 0.5 bar at maximum (7 psi). With optimized exhaust and intake manifold design up to 9 psi at scavenging phase are possible (fuel consumption wasn't the criteria :D) with a NA concept.

Listen to less people with sour cream for brains on this forum and call the experts that build these engines every day.
That's interesting. Do you think, being able to copy books and sell it, inherently means understanding what is the content of those books? I would say the probabilty is increased :D. My team and I develope (simulation, construction and so on) and test highly boosted, one or more staged TC engines and everyday there is a change to learn more about it. But most over the time it is like copying the same steps again and again, engines are just engines. If there is no interest for learning, you wont get forward in your knowhow. Most knowledge is generated when theory and practise are combined, at best in a sportive competition to see what works at the limit :D...as I wrote, the probability is just increased.
 

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Discussion Starter #16
Spoke with someone at 4 pistons i believe it was josh and i asked about the outlaw cam . told him what cam i have now . Told me that i would prob pick up make 30-40 hp over the cam i have now. said that they dont really have any thing to compare it too. Told me that i should just stick with what i have and see how it turns out and if later on i want to swap cams that would be the best route.
 

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I repeat, CALL Luke and ask. Usually get better luck of reaching him. :)

There is so much BS on this forum.. .and so many experts with sour cream for brains...

You are talking about reversion, below. Tell me how when there is 30 psi of pressure in the intake and 15 psi of (back-) pressure in the exhaust, the air will flow from 15 psi to 30 psi i.e. against the pressure gradient???
.. and the rivers flow up hill??? With high(er) boost, there is a positive pressure gradient across the engine. This is not the case with lower boost and smaller turbos or Naturally Aspirated (NA) cars.

The problem is the opposite. With high overlap, you will blow air and fuel out into the exhaust. It will get hot. It will spool the turbo faster!!! It may get too hot or backfire at low revs.... At lower boost levels it will reverse and flow exhaust into the intake and idle and run badly. This is the case of with a NA engine at idle and off idle with high-lift cam, also. So no difference.

Why have overlap on a cam at all?

Cams and valve timing is the most complex part of the motor. There are 4 different scenarios:

1. NA. Overlap, intake and exhaust can be tuned in such a way that the inertia of moving air will create a slightly higher pressure in the intake and a small vacuum in the exhaust. This will create maybe a 2 to 4 psi pressure gradient in a very narrow RPM range.

2. Supercharging almost always has a positive pressure gradient on the engine. Some charge tuning as in (1) still applies. Also air/fuel blowing into exhaust applies. Street cams go conservative and reduce overlap, give up the charge-tuning effect (as in 1). Look at grad cars with superchargers, they run a lot of overlap...

3. Low pressure turbocharging has a very narrow range where the pressure gradient is positive, as the turbine chokes the motor at high end. The charge tuning is offset by high back-pressure and overlap would not be good.


4. Hogh-pressure (big turo and turbine, like yours) will create a positive gradient across the motor at over 15 psi boost al the way up the rev range, until the turbine will become a restriction. Overlap is good because there is a charging effect, even more so with more air mass, and better flow across the engine at high RPM where the intake/exhaust events are shorter in duration (but still need to fill same cylinder volume with more air and fuel). Larger can will seem even larger with a turbo i.e.move torque and power up the RPM range. Again, it all depends on what you have and what you want to achieve. A Stage 4 cam would be a great 7000 to 11,000RPM cam, but would suck at 4000. A turbo cam may work in 4500 to 8500 range and have OK idle. What are you after? A Stage 4 will make much more power, but at the very top. Not to mention that VTC helps....

Above, is a very simplistic explanation.

Listen to less people with sour cream for brains on this forum and call the experts that build these engines every day. Serious motor deserves serious advice.

Anton
This x1,000,000.

CALL LUKE!!!
 

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Discussion Starter #20
Looking to get feed back on the skunk 2 ultra 2 cams???? ive sen where they perform better than the DC4 cams. To much cam for high hp boost?
 
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