To "CAM or not to "CAM"? & Whats the ideal Comp ratio?

[Greg Z]

I have a lower compression eng. Its 9:5:1 right now but we are gonna change the pistons to CP Pistons, so obviously I can put whatever. What is the ideal Comp ratio on a single turbo NSX? The turbo will be the GTK series 650. and then should I use cams and if so which ones?

 

[nsxotic911]

What does "CAM" and compression in common..? If you mean camshfats, they shouldn't have anything to do with each other.

 

[HONDA_RJJ]

He did ask the cams as a second question and cams and static CR ratios make a difference but not really on turbo cars but on NA cars it you have all out cams becauce of the overlap? the the pistons CR ratio doesn't fully apply because the lack of a full seal and thats why they recomend 12:1+ CR ratios on more extreme NA cams.

BTW I'm bad at explaning this and its not really relative to this case due to FI

 

[Greg Z]

Yes, I am asking 2 seperate/different questions.

I will try to rephrase.

I have a lower CP engine. I have the oportunity to change it. What is the most/best ideal CP to go with?

ALSO::::::::::

should I put camshafts in. I know they are great in turbo cars as they wake lower compression engines up until the boost hits, but I've also heard that they complicate things a lil too much, and we all know simplicity is a good thing. Once I tune it I don't ever want to have to mess with it again. Rumor has it with cams/cam gears I will have to fiddle from time to time.

 

[eamelgar]

Compression ratio should be determined by how much boost you plan to run...lower compression pistons will allow you to run more boost on the same grade of fuel.

I will be running Webcams in my motor with their forced induction grind. Cams can't hurt, in my opinion.

 

[HONDA_RJJ]

Stupid questions if your engines already built why fix what isn't broken?
Cams will make power but depending on how extreme you go there may cause idle problems and i asuming your not caring about emission issues. Cams will usally make power in a higher RPM and loose low end if there more on the race side.

 

[Greg Z]

Stupid questions if your engines already built why fix what isn't broken?
Cams will make power but depending on how extreme you go there may cause idle problems and i asuming your not caring about emission issues. Cams will usally make power in a higher RPM and loose low end if there more on the race side.

Ok noob, are you just trying to get your post count up or what. That statement was completely useless.

My motor is down that is why I'm changing pistons duh. I'm not looking for "race side" cams, I'm looking for cams that will give low end until the turbo spools. Usually referred to as blower cams and such.


So far no-one has answered my question. The engine builder/tuner has his opinion of course I just thought I would get a feel for what the NSX community thought before I made a final decision.

questions are:

Should I use cams?

if so, which ones?

and is 9:5:1 the perfect CP with the GTK 650?

 

[HONDA_RJJ]

Motors are electric and you made no mention of anything being "down" DB

 

[nsxotic911]

Ok noob, are you just trying to get your post count up or what. That statement was completely useless.

My motor is down that is why I'm changing pistons duh. I'm not looking for "race side" cams, I'm looking for cams that will give low end until the turbo spools. Usually referred to as blower cams and such.


So far no-one has answered my question. The engine builder/tuner has his opinion of course I just thought I would get a feel for what the NSX community thought before I made a final decision.

questions are:

Should I use cams?

if so, which ones?

and is 9:5:1 the perfect CP with the GTK 650?

Honda_RJJ actually made a intelligent, informative and accurate post, but you chose to ridicule him.

No one has answered your question as you wanted because there is no off-the-shelf answer. I don't know any manufacturer that attempted to make a "blower" or "low-rpm tuned" camshaft. All aftermarket camshafts I've heard of are for the upper range because that's where the NSX has the most potential to make the most power, where it already makes the most power n so forth.. Who would want to spend thousands of dollars to get 10 extra horsepower at 2000 rpm..?

The BEST answer I could give you is, talk to Shad @ DA and/or Today Racing. I'm sure that they could grind you a camshaft for your particular application, that would be, at least marginally better than your current camshafts which are very good to begin with.

Reading up on a few resources may help you get more edumacated:
http://auto.howstuffworks.com/camshaft1.htm
http://auto.howstuffworks.com/question562.htm

The GTK sound like great turbochargers, but again, it's hard to say without realling looking at, thinking and tuning your engine. 9.1 might be good for 500, maybe 600whp, or it might fail at 450. Some have reported stock engines of doing nearly or 500WHP on stock everything and stock compressions. Others have blown up at 330RWPH with spiffy aftermarket stuff.

Make sense? Again, my best advaice is that since you're stuck on 9.5:1, get them, start tuning, and turn up the boost and timing until you start pinging, then report back to us on what you came down. Do leakdwon tests after a few thousand miles and a certain period after that to gauge how the engine is doing.

 

[Greg Z]

Honda_RJJ actually made a intelligent, informative and accurate post, but you chose to ridicule him.

.

WHAAAAT You are kidding I hope. Lets break down what he said.

Stupid questions if your engines already built why fix what isn't broken?
.

He chose to ridicule me first.

and even if my engine wasn't "broken" its my peragotive to change my CP at my choosen. There was no need for him to go there

Cams will make power but depending on how extreme you go there may cause idle problems and i asuming your not caring about emission issues. .

Cams make power? WOW didn't know that
idle problems? common knowledge.
Emmisions?, no question said nothing about emmissions.

Cams will usally make power in a higher RPM and loose low end if there more on the race side.

Really. I did not know this

Of course they do "usually" !!! I'm looking for turbo cams not NA cams and clearly stated that.

No one has answered your question as you wanted because there is no off-the-shelf answer. I don't know any manufacturer that attempted to make a "blower" or "low-rpm tuned" camshaft. All aftermarket camshafts I've heard of are for the upper range because that's where the NSX has the most potential to make the most power, where it already makes the most power n so forth.. Who would want to spend thousands of dollars to get 10 extra horsepower at 2000 rpm..?

To me that entire statement has a hint of "ridicule" in it also.

A supporting vendor has them on this site .

http://www.scienceofspeed.com/products/engine_performance_products/NSX/ScienceofSpeed/camshafts/

The BEST answer I could give you is, talk to Shad @ DA and/or Today Racing. I'm sure that they could grind you a camshaft for your particular application, that would be, at least marginally better than your current camshafts which are very good to begin with.

.

This IS ALL I was lookng for, good ol fashion help. Not to be riduculed or have life explained to me. thank-you for this peice of info, I will give them a call this week.

T

Make sense? Again, my best advaice is that since you're stuck on 9.5:1, get them, start tuning, and turn up the boost and timing until you start pinging, then report back to us on what you came down. Do leakdwon tests after a few thousand miles and a certain period after that to gauge how the engine is doing.

Who said I'm stuck on 9:5????? That just simply happems to be what I have in my "broken" motor at the moment and the sole reason of this threads question pertaining to the CP is only to find out if that is the best CP to go back with or should I change it?


Granted NSX's may be different and THAT IS WHY I'M ASKING THE QUESTION, "BUT" in the Corvette world we all run Turbo cams to help out untilthe boost hits. I was simply hoping that by putting turbo cams in the X will help it on the low end a bit. But I heard they can be problematic and I was wondering the pro's and con's and a list of the different available cams out there so I could chose one. Very simple questions I thought but, my bad.

 

[nsxotic911]

WHAAAAT You are kidding I hope. Lets break down what he said.



He chose to ridicule me first.

and even if my engine wasn't "broken" its my peragotive to change my CP at my choosen. There was no need for him to go there






Cams make power? WOW didn't know that
idle problems? common knowledge.
Emmisions?, no question said nothing about emmissions.





Really. I did not know this

Of course they do "usually" !!! I'm looking for turbo cams not NA cams and clearly stated that.




To me that entire statement has a hint of "ridicule" in it also.

A supporting vendor has them on this site .

http://www.scienceofspeed.com/products/engine_performance_products/NSX/ScienceofSpeed/camshafts/





This IS ALL I was lookng for, good ol fashion help. Not to be riduculed or have life explained to me. thank-you for this peice of info, I will give them a call this week.




Who said I'm stuck on 9:5????? That just simply happems to be what I have in my "broken" motor at the moment and the sole reason of this threads question pertaining to the CP is only to find out if that is the best CP to go back with or should I change it?


Granted NSX's may be different and THAT IS WHY I'M ASKING THE QUESTION, "BUT" in the Corvette world we all run Turbo cams to help out untilthe boost hits. I was simply hoping that by putting turbo cams in the X will help it on the low end a bit. But I heard they can be problematic and I was wondering the pro's and con's and a list of the different available cams out there so I could chose one. Very simple questions I thought but, my bad.

I'd ask SOS what they mean by "FI cams" - whether it's expected to increase power down low or not. Without a dyno............................... I'm going to be a skeptic. Up high, yeah, probably.

 

[HONDA_RJJ]

I said stupid questions because i counldn't figure out why you with a built engine would spend a bunch of money to rebuild it, the stupid question was the question that I was asking as stated. Alot of people use "NA" cams in turbo setups for Hi end power even "turbo" cams are for high end power this is a Honda/Acura thats what there know for and thats what companys make cams for. I said the main difference is that amount of overlap because if both valves are opended at the same time for too long the boost will push through it but some overlap can help the cylider so its a trade off.

 

[Flexer]

WHAAAAT You are kidding I hope. Lets break down what he said.



He chose to ridicule me first.

and even if my engine wasn't "broken" its my peragotive to change my CP at my choosen. There was no need for him to go there






Cams make power? WOW didn't know that
idle problems? common knowledge.
Emmisions?, no question said nothing about emmissions.





Really. I did not know this

Of course they do "usually" !!! I'm looking for turbo cams not NA cams and clearly stated that.




To me that entire statement has a hint of "ridicule" in it also.

A supporting vendor has them on this site .

http://www.scienceofspeed.com/products/engine_performance_products/NSX/ScienceofSpeed/camshafts/





This IS ALL I was lookng for, good ol fashion help. Not to be riduculed or have life explained to me. thank-you for this peice of info, I will give them a call this week.




Who said I'm stuck on 9:5????? That just simply happems to be what I have in my "broken" motor at the moment and the sole reason of this threads question pertaining to the CP is only to find out if that is the best CP to go back with or should I change it?


Granted NSX's may be different and THAT IS WHY I'M ASKING THE QUESTION, "BUT" in the Corvette world we all run Turbo cams to help out untilthe boost hits. I was simply hoping that by putting turbo cams in the X will help it on the low end a bit. But I heard they can be problematic and I was wondering the pro's and con's and a list of the different available cams out there so I could chose one. Very simple questions I thought but, my bad.

Gregz,

Please stop talking like you are SO bright. There is no such thing as blower cams, or a cam that produces power down low. If anything that would be a stock cam that has a very low duration. You can't improve the overall VE of any motor with a cam, all you can do is shift its VE around. The only way you gain some VE is by going to a "boosted" cam were cylinder overlap is all but eliminated because cylinder scavenging is no longer important. Go get a book on cam tuning or something, or just trust your engine builder as he should know all this stuff. But really learn what volumetric efficiency of a motor is and go from there.

J. R.

 

[David]

my .02

I usually go with 9 to 9.5:1 compression for turbo motors. I have found it to be a good compromise between higher compression (which gives better response, but limits boost, all else equal) and really low compression (more boost, less responsive). For some perspective, in reality, 9.5 is only 'low' in our world. Many domestic guys would consider that fairly high compression.

It helps to think about the basic physics of the choice. If the fuel grade and tuning sophistication are equal, you have the same fundamental limits on both motors - heat, cylinder pressure, etc. In a lower compression motor, you are doing more of the compression at a point where you can pull some of the heat out of it and less in the cylinder itself, where the heat is trapped and contributes to pre-ignition thermal limits. In a high compression motor you are doing a greater percentage of the compression within the cylinder, so you have more heat and therefore are limited to a lower net/effective compression.

I have dyno tested a variety of cams on turbo motors and have found that a modest NA cam profile works the best for low to medium boost motors and an aggressive NA cam works well in high boost motors. The old concerns about too much overlap in FI motors has largely fallen by the wayside. The basic flow characteristics are essentially the same are the same as wtih NA motors. A big cam is great when it can move enough air to work effectively and is not when it can't. Its that simple.