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Need help analysing this cam for my application

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Old Oct 25, 2005 | 03:54 PM
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Default Need help analysing this cam for my application (Twin Turbo)

Just got off the phone with Dave at Comp Cams and he recommended a cam for my application. I would appreciate some opinions on why he chose these specs.

Application:
LS2 402
Twin GT30R turbos
AFR225 heads
8-15 lbs boost

Cam Specs:
3722 in. lobe
3723 ex. lobe
224 in duration
223 ex. duration
115 LSA
+3 deg. advance ground in
ICL 112

There has been a lot of analysis of cams for N/A applications. This could be a good oportunity to discuss turbo cams.

Last edited by hpcubed; Oct 25, 2005 at 07:23 PM.
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Old Oct 25, 2005 | 04:13 PM
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Default 224/228 114 Lsa

i think that the 224/228 114 LSA customed for AFR 205 Heads would work great with your set up .... nice idle quality and good overall camshaft
it has more exhaust duration than the intake and i think that is what you are looking for to spool up your turbos faster and you dont need much intake duration and thats because of the turbo forced air
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Old Oct 25, 2005 | 07:12 PM
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That cam would probably work ok but turbos usually do not benefit as much as a blower from a split pattern with a longer ex. duration (from what I have read).
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Old Oct 25, 2005 | 08:21 PM
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Originally Posted by disposer
i think that the 224/228 114 LSA customed for AFR 205 Heads would work great with your set up .... nice idle quality and good overall camshaft
it has more exhaust duration than the intake and i think that is what you are looking for to spool up your turbos faster and you dont need much intake duration and thats because of the turbo forced air
That's the thinking behind supercharger cams, but Turbo's are completly diffrent. Turbo's actually like the reverse split. Contrary to the specs that are posted, the 3723 is a 226 lobe. This would make a 224/226 XE-R cam. Personally, for th eapplication at hand, I'd turn it around to a 226/224. That would make a 3723 intake and a 3722 exaust.
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Old Oct 25, 2005 | 09:29 PM
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Originally Posted by Beast96Z
That's the thinking behind supercharger cams, but Turbo's are completly diffrent. Turbo's actually like the reverse split. Contrary to the specs that are posted, the 3723 is a 226 lobe. This would make a 224/226 XE-R cam. Personally, for th eapplication at hand, I'd turn it around to a 226/224. That would make a 3723 intake and a 3722 exaust.
You may be right, maybe I have the in. and ex. lobes switched but he told me the duration would be 224 in. 223 ex.. It is an XE-R lobe.
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Old Oct 25, 2005 | 09:34 PM
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Why do you think he went with +3 deg advance as apposed to +4 or zero for the matter? The +3 will get the intake valve open quicker and ex. valve closed sooner which will give a bit higher cylinder pressure to get the turbos moving but will this be OK at 15 lbs of boost?

A 115 LSA seems to be a good choice for the 402. I think it will give good area under the curve. Correct?

I'm learning. Keep the discussion going please.
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Old Oct 26, 2005 | 08:39 AM
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115 LSA is to reduce overlap. Boosted engines do not need much overlap, as it bleeds of boost if the valves are held open too long at the same time.

Turbo setups generally work well with reverse splits like this, supercharged setups tend to work slightly better with traditional split duration cams.

I'm not sure there is anything "advanced" about this discussion, camshaft choices have been discussed at least 1000 times in the internal engine forum. Maybe someone can post about the theory or engineering data to back up the statements above, otherwise this one will be moved soon.
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Old Oct 26, 2005 | 03:32 PM
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Originally Posted by Nine Ball
115 LSA is to reduce overlap. Boosted engines do not need much overlap, as it bleeds of boost if the valves are held open too long at the same time.

Turbo setups generally work well with reverse splits like this, supercharged setups tend to work slightly better with traditional split duration cams.

I'm not sure there is anything "advanced" about this discussion, camshaft choices have been discussed at least 1000 times in the internal engine forum. Maybe someone can post about the theory or engineering data to back up the statements above, otherwise this one will be moved soon.
That is exactly what I was looking for - someone that knows more than I do to post about the theory of a turbo cam which would back up the specs above. I have seen a lot of discussion on NA cams but not much on turbo cams. I have done searches and do not find any detailed information other than like what you stated above. That is why I posted this in this section hoping that the people that wrote some of the other "advanced" topics here would chime in.
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