Who wants to teach me about Cams? (camshafts) - Page 3 - Nissan 350Z Forum, Nissan 370Z Tech Forums
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post #21 of 69 (permalink) Old 03-16-2006, 01:58 PM Thread Starter
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Actually, there is more of a range than that:

https://www.350z-tech.com/zwiki/Part:Camshafts

Note: I will use my new found knowledge from this thread to build on the Camshaft wiki page... OR someone that knows this better than me can do it.

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post #22 of 69 (permalink) Old 03-16-2006, 02:08 PM
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Lash refers to the amount of space between the cam and the pad, it allows for expansion of the various parts. That way the valves can come all the way back down on their seats. Some cams require different lash settings than stock for optimal performance.

The bigger the cam, the higher and more narrow the power band will be in the RPM range. I don't know the specifics about the VQ enough to tell you what numbers are the limits of a streetable cam vs. over the top.

As an example though, say you went with a full race cam, you may have an excellent power band from 3k to 8k but a dog from idle to 3k. On the race track that is no problem, you will have the car in the power band the whole time, on the street it would be a dog until you got it revving.

Chris


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post #23 of 69 (permalink) Old 03-16-2006, 02:20 PM
 
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Quote:
Lash refers to the amount of space between the cam and the pad, it allows for expansion of the various parts. That way the valves can come all the way back down on their seats. Some cams require different lash settings than stock for optimal performance.

The bigger the cam, the higher and more narrow the power band will be in the RPM range. I don't know the specifics about the VQ enough to tell you what numbers are the limits of a streetable cam vs. over the top.

As an example though, say you went with a full race cam, you may have an excellent power band from 3k to 8k but a dog from idle to 3k. On the race track that is no problem, you will have the car in the power band the whole time, on the street it would be a dog until you got it revving.

Chris
Thanks! That makes sense. However, I still don't feel I can make a good choice based on all the different setups available. My thinking right now is to go with the Nismo cams since they probably have the most intimate knowledge of the VQ. But that's about all I can come up with. Notice I can't make any argument with regards to the actual cam measurements. :(
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post #24 of 69 (permalink) Old 03-16-2006, 03:29 PM
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I'm with Conan. I'd like to know which one is the best. Is there a cam set that gives better low end power or has a broader power band?

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post #25 of 69 (permalink) Old 03-16-2006, 04:11 PM
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Here is something I thought was interesting about the 350Z and cams

From http://www.sportcompactcarweb.com/ro...0405scc_nismo/

"Valve lift is increased from 0.376 inches to 0.426 inches and duration steps up from 240 degrees to 262. The cams offer little downside, thanks to the Z's variable intake cam timing. With the system automatically dialing out valve overlap at idle and low rpm, there's none of the lopey idle you might secretly wish for. Instead, there's just a subtle occasional misfire at idle and the same responsive, torquey bottom end the engine already had."

So the stock cam is a 240 with 0.376" of lift.

Seems like the Nismo is a good choice and would still be a very drivable street car. For that matter, all of those cams may be fine on the street.

One thing that has not been addressed and for most it does not matter but Smog may be an issue with more radical cams because some of the intake charge may go out the exhaust, although this makes it sound as if even that is minimal based on the variable vale timing.

Chris


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post #26 of 69 (permalink) Old 03-16-2006, 04:25 PM
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Note: On the above article, take a look at the power figures in the table at the end and the motor mods.



<table>
<tr >
<td>*</td>
<td>Stock</td>
<td>S-Tune</td>
<td>R-Tune</td>
</tr>
<tr >
<td>Claimed Crank Hp:</td>
<td>287 hp @ 6200 rpm</td>
<td>No claim made</td>
<td>Approx 305 hp</td>
</tr>
<tr >
<td>Claimed Crank Torque:</td>
<td>274 lb-ft @ 4800 rpm</td>
<td>No claim made</td>
<td>No claim made</td>
</tr>
<tr >
<td>Measured Wheel Hp:</td>
<td>239 hp @ 6000 rpm</td>
<td>243 hp @ 6000 rpm</td>
<td>249 hp @ 6100 rpm</td>
</tr>
<tr >
<td>Measured Wheel Torque:</td>
<td>237 lb-ft @ 4700 rpm</td>
<td>238 lb-ft @ 4800 rpm</td>
<td>242 lb-ft @ 4400 rpm</td>
</tr>
<tr >
<td>Internal Modifications:</td>
<td>None</td>
<td>None</td>
<td>NISMO cams</td>
</tr>
<tr >
<td>External Modifications:</td>
<td>None</td>
<td>NISMO stainless cat-back exhaust</td>
<td>NISMO stainless cat-back exhaust,</td>
</tr>
<tr >
<td>*</td>
<td>*</td>
<td>*</td>
<td>NISMO stainless headers, Nismo cold-air intake</td>
</tr>
</table>


Considering the price of the mods, that is not a lot of gain. On the otherhand peak torque actualy arives earlier with the R-Tune cams (and all the other stuff).


Chris


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post #27 of 69 (permalink) Old 03-16-2006, 04:32 PM Thread Starter
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Good find.. this is the kind of topic i was hoping for. I could read howstuffworks.com, but that would not reveal the secrets of the Z

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post #28 of 69 (permalink) Old 03-16-2006, 04:34 PM
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Just out of curiosity, why do you say that the Nismo is a good street choice? Based on the duration and lift posted by Conan, I couldn&#39;t even begin to understand why one would be better than the other.

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post #29 of 69 (permalink) Old 03-16-2006, 04:45 PM
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The Nismo&#39;s seem like a good street cam based on the review because they say that it keeps the torque down low and opens it up at the top. Basically a well mannered car with more top end.

Keep in mind though, after reading the whole review and looking at the numbers, they have headers, intake and cams and the amount of extra power they make is pitiful for the $3000+ in those three mods alone (with install).

While I was at it, i found this

http://www.nissanperformancemag.com/august02/ask_sarah/

"Q: I&#39;ve heard a lot about how cams work, but I&#39;m still a little confused. Can you explain how aftermarket cams can add power to my ride?

A: The camshafts control how long and how much your valves are open. There are three important factors of the cam that affect their performance: duration, or the number of degrees the valve is held open by the cam; lift, the height the valve is lifted on the valve seat; and overlap, the period when both the intake and exhaust valves are open at the same time. At high rpm, there is less time to fill the cylinder. A cam with greater duration keeps the valves open for increased degrees of crank rotation allowing the cylinder more time to fill. The more lift a cam has, the more flow that passes through the higher lifted valve. For all out crazy engine setups, you want a long duration and as much lift as possible. However, stock and mild race cars shouldn&#39;t use such a wild cam. When the duration is increased, the exhaust valve opens earlier and you may experience blowdown, which is gasses expanding during the power stroke that are blown back down the exhaust pipe. Blowdown creates a power loss during the power stroke because it quickly rids the engine of the pressure it needs to create power. Increasing overlap increases the time between the opening and closing of the cams points. Overlap can cause reversion at low rpm, which is exhaust gas pushed back up the intake port. Reversion dilutes the intake charge preventing the cylinders from completely filling, and decreases the cylinder pressure at low speeds causing low speed misfire. This low speed misfire causes lots of hydrocarbon pollution which is why stock cams have very little overlap (do you want to chew your air?). Full racing cams usually have around 305 degrees of duration and 0.5" of lift, which produces raging top end power at the expense of low end power, but idle poorly and will blow emissions tests off the charts! A good aftermarket cam pulls around 4000-7500 rpms with a faint lopey sound at idle and will have about 265 degrees of duration, 0.42" lift, and 30 degrees of overlap. This type of cam will work well with all the bolt-ons and can be used in a daily driver. A stock cam has about 240 degrees of duration, 0.39" lift, and 15 degrees of overlap. The stock cams work well between 700-6500 rpm and idle very smoothly. One caveat: if you aren&#39;t too familiar with your engine bay, have a professional install your cams. You can easily blow an engine if you don&#39;t take all the necessary precautions during installation. "



Chris


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post #30 of 69 (permalink) Old 03-16-2006, 04:56 PM
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I&#39;m beginning to see the light...

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