compression
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It might help if you stated which Skunk2 Cams you were getting (stage 1, stage 2....). I talked to MD about this before, and I think he said somewhere around 10.6:1 CR??? Don't quote me on that, but it's somewhere around there. You can even run it on stock CR, but if you want the most out of the Skunk2 cams, you should raise the CR.
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It all depends, as Surfer X said, on octane rating, tuning and fuel. Can you tell us what all your engine mod plans are? and what is the highest octane rating you can get off the pump where you are?
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If your serious and money is not an issue, then 200whp would be a good realistic goal. For this, I would go with ITR pistons (11.1/1 CR). They are high enough to match your cam package without too much worry about a piston through the block. To be safe, you can mess around with the ignition timing, start it at 16 degress BTDC, and if your O.K. on that put it up to 18 degress BTDC, but DO NOT go past that. Make sure the cams and fuel are tuned for an N/A setup by a good tuning shop that has a wide band o2 sensor, you will need a fuel pressure regulator to get it done properly on this setup. If you want a good package, invest in a Hi-Tech or SMSP exhaust system, this will REALLY help in a good setup as well. Now you should be on your way. Good luck.
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it's not that you should go for the highest static CR possible. You should go to highest static CR that the cams will support. In MD's Tech Corner there was a thread I had started on the effect of the intake cam opening duration on dynamic CR. In there I linked to a website which had a dynamic CR calculator. You could plug in the intake cam's ABDC degree number off the manufacturer's spec sheet and then change the static CR to see what dynamic CR you would get.
With wild cams like the Skunk2 stage 2, the longer intake cam duration spec causes cylinder pressure to be lost up the intake port at partial intake valve opening points. Loss of cylinder pressure reduces the amount of complete burn you can get once the spark has ignited the compressed air/fuel mix.
If you place too much cylinder pressure in at the wrong time during the compression stroke , there is a loss of power at the top end from work used up in overcoming the extra pressure you added...similar to parasitic losses...So you should choose enough static CR to get just a high enough dynamic CR to support a clean complete burn.
As I recall, if the Skunk2 stage 2 cams have similar specs as the Jun 3, then 11.2-11.4:1 CR is more than enough for these cams...you don't have to go crazy on the static CR like you would on the Toda Spec B and C cams.
With wild cams like the Skunk2 stage 2, the longer intake cam duration spec causes cylinder pressure to be lost up the intake port at partial intake valve opening points. Loss of cylinder pressure reduces the amount of complete burn you can get once the spark has ignited the compressed air/fuel mix.
If you place too much cylinder pressure in at the wrong time during the compression stroke , there is a loss of power at the top end from work used up in overcoming the extra pressure you added...similar to parasitic losses...So you should choose enough static CR to get just a high enough dynamic CR to support a clean complete burn.
As I recall, if the Skunk2 stage 2 cams have similar specs as the Jun 3, then 11.2-11.4:1 CR is more than enough for these cams...you don't have to go crazy on the static CR like you would on the Toda Spec B and C cams.
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As usual MD (Chief Guru) is here with better advice. Please listen to him as he knows his $#!t.
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you look like you know your sh*t too man....
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Thanks MD, coming from you that's a real compliment. You just made my day. (sorry if it sounds like I'm greasing, but everyone really respects you. Cheers).
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u might wanna get JDM ITR pistons to give you 11.4:1 CR..USDM ITR pistons will give you 11:1 CR.
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480 Posts
dont do like the guys on this board and try and make power with these cams without pistons, headwork and
extensive EMS tuning. if you dont plan on going all that
far, I have SEEN two cars local in Orlando pulling 185-193/135-143s @ 80 deg or more with:
GSR head
ITR block
mugen gasket (11.2-4:1)
Skunk2 Manifold, 65mm TB
Skunk2 stage1 cams
STOCK GSR VALVETRAIN
9K rev limit (I know, I know... the cars are stock
upstairs and still pulling like a champ on these
cams...)
STRoNG power to 8700rpm
I,H,E
Field SFC-VTEC or APEX-i take your pick
OBD1 computers with modified stock maps
and raised rev limits
stock injectors
B&M fpr
energy suspension mounts
Del Sol VTEC tranny
cams arent the only way to make power!
dont overcam your motor... you will lose
drivable power that Mr. Honda put there for
a reason!
extensive EMS tuning. if you dont plan on going all that
far, I have SEEN two cars local in Orlando pulling 185-193/135-143s @ 80 deg or more with:
GSR head
ITR block
mugen gasket (11.2-4:1)
Skunk2 Manifold, 65mm TB
Skunk2 stage1 cams
STOCK GSR VALVETRAIN
9K rev limit (I know, I know... the cars are stock
upstairs and still pulling like a champ on these
cams...)
STRoNG power to 8700rpm
I,H,E
Field SFC-VTEC or APEX-i take your pick
OBD1 computers with modified stock maps
and raised rev limits
stock injectors
B&M fpr
energy suspension mounts
Del Sol VTEC tranny
cams arent the only way to make power!
dont overcam your motor... you will lose
drivable power that Mr. Honda put there for
a reason!
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I'm waiting for the day those engines have valve float or coil bind and die.
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1,608 Posts
WTF? Why would someone use the stock GS-R valvetrain with stage1 cams? Wonder how fast those springs are gonna wear out....MikeSarrGSR on Sep/06/02 said:
It's one thing to make power. It's another to make reliable, long lasting power. If you are going to bother to do something, don't waste you time and do it half-assed...
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301 Posts
The Skunk 2 stage 1 cams have a much longer duration than type r cams which they are most comparable to, therefore allowing a shallower lift on the cam rotation. They are recommended for a valve train upgrade, but it is not neccesary for this reason.
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you have to ask what do they mean by "stock" valvesprings: stock ITR intake only, stock ITR valvesprings both sides, stock GSR both sides....each one has a different level of protection.
I think Skunk2 also made these recommendations that you can use "stock" valvesprings with a stock redline in mind...and they certainly do NOT expect that recommendation to hold up if you rev to 9000 rpm with stock valvesprings.
Those engines may pull like a champ but I'd like to see if their power dies off in the last 1000 rpm severely which is a tell tale first sign of valve float.
Those engines are ticking time bombs. It's only a matter of time IMHO before 1 day a piston will crunch a valve (the most likely scenario is an exhaust valve).
I think Skunk2 also made these recommendations that you can use "stock" valvesprings with a stock redline in mind...and they certainly do NOT expect that recommendation to hold up if you rev to 9000 rpm with stock valvesprings.
Those engines may pull like a champ but I'd like to see if their power dies off in the last 1000 rpm severely which is a tell tale first sign of valve float.
Those engines are ticking time bombs. It's only a matter of time IMHO before 1 day a piston will crunch a valve (the most likely scenario is an exhaust valve).
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I agree, I kept asking the guys... whY? WHY are you doing this and they said... no problems YET. If I hadnt seen it with my own eyes, I wouldnt have believed it. I asked Tong like 5 times, retainers at least? He was,
nope. Stock GSR. If I remember, there was a falloff
after 8500, but not by much I saw him dyno his car
last in mid april. He drives it HARD on the street, at
sebring and at the drag strip and "no problems yet."
My only point is to illustrate the fact that power can be made on medium sized cams. If one can get 200whp+ on an ITR motor on stock cams, you sure as heck can do it with skunk stage 1s. That is my only point here. I like the idea of cams in the 260+ range, I guess with tuning with systems like Hondata you can realize the power on them. I surmize based on seeing alot of charts with hot stage 2 and 3 cams on stock timing curves, the ECU cannot keep up with all those extra CFMs. Fuel tuning cannot compensate for this.
It almost inherently begs the question in saying Stage 2. Why are they calling it a stage 2 cam? Well, tuning with NA what do you first, I,H,E maybe a piggyback fuel computer and a stage 1 cam. When you move up, raising the compression a bit, adding full ecu tuning and port work seems to be the formula for stage 2 cams, perhaps even some properly sized injectors for the added output and upper RPM power. valvesprings and retainers could be added here with lighter valves for more slightly more accurate valve timing. I reccomend using CTR or stage 1 skunks until you can do nothing else but change the cam. Just buying cams is not a shortcut to 220whp
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nope. Stock GSR. If I remember, there was a falloff
after 8500, but not by much I saw him dyno his car
last in mid april. He drives it HARD on the street, at
sebring and at the drag strip and "no problems yet."
My only point is to illustrate the fact that power can be made on medium sized cams. If one can get 200whp+ on an ITR motor on stock cams, you sure as heck can do it with skunk stage 1s. That is my only point here. I like the idea of cams in the 260+ range, I guess with tuning with systems like Hondata you can realize the power on them. I surmize based on seeing alot of charts with hot stage 2 and 3 cams on stock timing curves, the ECU cannot keep up with all those extra CFMs. Fuel tuning cannot compensate for this.
It almost inherently begs the question in saying Stage 2. Why are they calling it a stage 2 cam? Well, tuning with NA what do you first, I,H,E maybe a piggyback fuel computer and a stage 1 cam. When you move up, raising the compression a bit, adding full ecu tuning and port work seems to be the formula for stage 2 cams, perhaps even some properly sized injectors for the added output and upper RPM power. valvesprings and retainers could be added here with lighter valves for more slightly more accurate valve timing. I reccomend using CTR or stage 1 skunks until you can do nothing else but change the cam. Just buying cams is not a shortcut to 220whp
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there is no such thing as any order in building engines in terms of parts. There is such a thing as planning though. You determine the power needs and location of where you want the power to be made along the rpm range and then choose the set of parts that will get you that goal. You have to know ahead of time what combination of parts will give you that. You dictate the behaviour of the engine by selecting compatible parts with the correct design feature to achieve it rather than the engine dictating to you what you should buy next.
The problem is people start in this with very little useful info from the other honda boards or magazines. We then just get things we can afford and do relatively mild changes in performance. So we become ignorant of the relationship between parts. We get things "in a certain order" or at least we think there is a set order...incorrectly.
The fact that we don't even have the notion of "engine combination" in our radar scopes shows how little useful info we actually receive from the magazines or manufacturers about combinations. They would like you to get things in order...they make more money that way. You end up with the wrong part and then have to sell it to buy another part that has the right design feature.
So a mild cam will work with a certain CR. Engine builders in racing do not build piece by piece in a given order. They look at the cam and say okay, will that get me the powerband I want at the correct part of the rpm range? If it does, then what other parts work with it or are affected by it? What is the RELATIoNSHIP between the cam to another part that affects my power goals? Obviously if you have been here lately, I've described the cam-CR relationship and the cam redline-port volume relationship.
The kid that gets a cam after i/h/e is missing the boat big time. If he thinks the cam is the "next part", he will probably get suckered into buying a wild cam spec that will be too big for his combination with stock CR. He will learn soon enough to his horror that the $1000 cams he bought that had made 200 whp on someone's dyno posted somewhere on the net, makes less power than his stock cams because he did not understand the effect of CR on cams and vice versa. He did not realize that the guy posting that dyno didn't tell everything about how he got that 200 whp or the tuning tricks to get there. he just thought : well so and so makes 200 whp with these and so, I'll get them, pay someone to install them, and I'll automatically make 200 whp...slap em in and they'll make power right?....doh!
The stages are another "red herring" to get you away from the engine combination awareness. They make you focus on one part and it's spec. It does not tell you what package would work with that spec. You just think it's like a leggo block and you upgrade up the staircase level...stages...the bigger leggo block, once plugged in, must make more power than the little leggo block regardless of what engine package it goes in...stage 3 must make more than stage 2 and stage 2 must make more than stage 1...right? well if you put stage 3's into a stock CR engine you will soon find that the leggo block assumption goes down the toilet and so does your power...
So as I said before: what's the next part? flip a coin and get any part you want because you just don't get it and will soon find out that you got suckered. the problem is these people don't come back on and have the courage to admit they made a huge mistake and the other problem is they don't know why they didn't make the "big power"...but stage 3's make 225 whp on so and so's dyno I saw on the web!
LOL...
The problem is people start in this with very little useful info from the other honda boards or magazines. We then just get things we can afford and do relatively mild changes in performance. So we become ignorant of the relationship between parts. We get things "in a certain order" or at least we think there is a set order...incorrectly.
The fact that we don't even have the notion of "engine combination" in our radar scopes shows how little useful info we actually receive from the magazines or manufacturers about combinations. They would like you to get things in order...they make more money that way. You end up with the wrong part and then have to sell it to buy another part that has the right design feature.
So a mild cam will work with a certain CR. Engine builders in racing do not build piece by piece in a given order. They look at the cam and say okay, will that get me the powerband I want at the correct part of the rpm range? If it does, then what other parts work with it or are affected by it? What is the RELATIoNSHIP between the cam to another part that affects my power goals? Obviously if you have been here lately, I've described the cam-CR relationship and the cam redline-port volume relationship.
The kid that gets a cam after i/h/e is missing the boat big time. If he thinks the cam is the "next part", he will probably get suckered into buying a wild cam spec that will be too big for his combination with stock CR. He will learn soon enough to his horror that the $1000 cams he bought that had made 200 whp on someone's dyno posted somewhere on the net, makes less power than his stock cams because he did not understand the effect of CR on cams and vice versa. He did not realize that the guy posting that dyno didn't tell everything about how he got that 200 whp or the tuning tricks to get there. he just thought : well so and so makes 200 whp with these and so, I'll get them, pay someone to install them, and I'll automatically make 200 whp...slap em in and they'll make power right?....doh!
The stages are another "red herring" to get you away from the engine combination awareness. They make you focus on one part and it's spec. It does not tell you what package would work with that spec. You just think it's like a leggo block and you upgrade up the staircase level...stages...the bigger leggo block, once plugged in, must make more power than the little leggo block regardless of what engine package it goes in...stage 3 must make more than stage 2 and stage 2 must make more than stage 1...right? well if you put stage 3's into a stock CR engine you will soon find that the leggo block assumption goes down the toilet and so does your power...
So as I said before: what's the next part? flip a coin and get any part you want because you just don't get it and will soon find out that you got suckered. the problem is these people don't come back on and have the courage to admit they made a huge mistake and the other problem is they don't know why they didn't make the "big power"...but stage 3's make 225 whp on so and so's dyno I saw on the web!
LOL...
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oh BTW, people lie. Some people say yeah I have stock valvesprings and they have no problems revving to the 9k redline.
did you look at the springs? did you confirm they were stock GSR?
if you have ever done a spintron test on valvesprings you would know right off these guys are lying.
I see this happen a lot. People give out wrong info to ensure their competition is 1 step behind at least. If they don't lie, then they won't tell you the entire story. I can assure you with confidence that if those were stock GSR springs you will soon meet Tong or whatever his name is at the side of a road at Sebring with smoke billowing out of his engine bay after a piston smacked his exhaust valve at 9k rpm and the broken valve cuisinarts the entire internals of his cylinder and head.
did you look at the springs? did you confirm they were stock GSR?
if you have ever done a spintron test on valvesprings you would know right off these guys are lying.
I see this happen a lot. People give out wrong info to ensure their competition is 1 step behind at least. If they don't lie, then they won't tell you the entire story. I can assure you with confidence that if those were stock GSR springs you will soon meet Tong or whatever his name is at the side of a road at Sebring with smoke billowing out of his engine bay after a piston smacked his exhaust valve at 9k rpm and the broken valve cuisinarts the entire internals of his cylinder and head.
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