blower cams...in general.
07-28-2009, 04:40 PM
#1
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blower cams...in general. What does make a good blower cam ? for a good spread of power, and wide rpm range etc ? whilst also retaining a decent, fairly smooth idle.
Query more biased towards centri's as thats what I have.
Obviously more lift should be good....up to the point where it affects valve control for high rpm ? How much lift is too much ?
You'd assume duration is also good....but where is the line drawn at too much, or too little and restricting the engine ?
Then LSA....most favour a wide LSA, but why ?
What would be the outcome of using a tight LSA ?
And then the even more awkward one....cam timing ? Is dialling to the cam card specs always best, or is deviation from this worthwhile ? ( Bit of a bollox to test though )
Query more biased towards centri's as thats what I have.
Obviously more lift should be good....up to the point where it affects valve control for high rpm ? How much lift is too much ?
You'd assume duration is also good....but where is the line drawn at too much, or too little and restricting the engine ?
Then LSA....most favour a wide LSA, but why ?
What would be the outcome of using a tight LSA ?
And then the even more awkward one....cam timing ? Is dialling to the cam card specs always best, or is deviation from this worthwhile ? ( Bit of a bollox to test though )
07-28-2009, 05:57 PM
#3
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That thread seemed to head towards turbos.
I'd like to discuss primarily centrifugal blower requirements.
Someone suggested to me ages ago, to choose a cam that will offer very good low-mid range increases on a n/a engine, and let the blower sort out the top end.
Best of both worlds really.
But TBH, on these engines, what sort of cam would do that ?
Or would simply chucking on a biggish, tight LSA n/a cam work well all round with the blower's assistance ?
If the topic has been done to death, which it probably has...just slap me and tell me to search more.
I'd like to discuss primarily centrifugal blower requirements.
Someone suggested to me ages ago, to choose a cam that will offer very good low-mid range increases on a n/a engine, and let the blower sort out the top end.
Best of both worlds really.
But TBH, on these engines, what sort of cam would do that ?
Or would simply chucking on a biggish, tight LSA n/a cam work well all round with the blower's assistance ?
If the topic has been done to death, which it probably has...just slap me and tell me to search more.
07-28-2009, 06:15 PM
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a cam that will offer better low end- middle power like you were suggested is probably the way to go. turbo and centri blower cams are kinda based on each other since the relationship of the power band is remotely similiar.
big thing to watch is vavle overlap, if your open to much you start bleeding boost which is one of those one step forward two steps back kinda thing. an excellent all around FI cam is the Z06 cam. if i remember right, a wider LSA cam has less overlap but ill let an expert correct me on that
BTW, what kind of racing you doing with it? that might make a difference...
big thing to watch is vavle overlap, if your open to much you start bleeding boost which is one of those one step forward two steps back kinda thing. an excellent all around FI cam is the Z06 cam. if i remember right, a wider LSA cam has less overlap but ill let an expert correct me on that
BTW, what kind of racing you doing with it? that might make a difference...
07-28-2009, 06:25 PM
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turbo and centri have no similarities with respect to this IMO.
Im asking a general question, not necessarily specific to myself just yet.
I drive on the road, do quarters, and the odd mile or so run.
My problem is, that over the last year or two while "upgrading" many aspects in terms of engine, my trap speeds and performance in some areas have decreased. And its annoying me now.
I just need something that will idle nicely at 8-900rpm, and pull very strongly to 7000rpm.
I ask a lot, but the 224/230 on 115LSA I had in my 382 some 2.5 years ago, did it, and had me almost hitting 150mph.
Despite new cylinder heads, a cam swap, larger headers, and also a larger engine....trap speeds seem to be falling, for no obvious reason I can see.
I dont see the headers or cylinder heads as a massive change...although nor is the camshaft. All items just one step up really.
And worse than that. Virtually same blower pulley sizes in use, and the 402 is making the same boost as my 382 was way back then.
And my belt is not slipping.
That just isnt right.
Im asking a general question, not necessarily specific to myself just yet.
I drive on the road, do quarters, and the odd mile or so run.
My problem is, that over the last year or two while "upgrading" many aspects in terms of engine, my trap speeds and performance in some areas have decreased. And its annoying me now.
I just need something that will idle nicely at 8-900rpm, and pull very strongly to 7000rpm.
I ask a lot, but the 224/230 on 115LSA I had in my 382 some 2.5 years ago, did it, and had me almost hitting 150mph.
Despite new cylinder heads, a cam swap, larger headers, and also a larger engine....trap speeds seem to be falling, for no obvious reason I can see.
I dont see the headers or cylinder heads as a massive change...although nor is the camshaft. All items just one step up really.
And worse than that. Virtually same blower pulley sizes in use, and the 402 is making the same boost as my 382 was way back then.
And my belt is not slipping.
That just isnt right.
07-28-2009, 06:45 PM
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how much boost you making with the 402? could it be possible that you have exceeded the limits of the blower and your just not getting any thing more out of it?
what kind of drops did you see in trap speed and times?
i just wanted to know more about your setup since it might get you a better answer knowing all the facts. a large turbo would be kinda similiar to a centri in that the boost builds towards the end of power band but id agree that in this case your better off getting a better answer specifically about centri blower cams
what kind of drops did you see in trap speed and times?
i just wanted to know more about your setup since it might get you a better answer knowing all the facts. a large turbo would be kinda similiar to a centri in that the boost builds towards the end of power band but id agree that in this case your better off getting a better answer specifically about centri blower cams
07-29-2009, 12:14 AM
#7
Stevie,
Try asking this same question over at speedtalk.com, there are some really bright engine folks over there that will give their inputs.
I decided to solid roller on the 383 and now a bigger one on the 434. Maybe worth considering as well. On the 383 did 230/236 on 112, the 434 has 242/248 on 115 after a lot of research and Q's. For lif I am trying to get the max out of the heads I have but still have the springs last on the street. Net lift on the 383 was .574/.583 with E-tec 200's. The 434 with new AFR235cc Eliminators and T&D shaft rockers wil have net .630"I/.674"E. No results on the 434 yet - just got the YSi yesterday.
On Comp Cam's page, IIRC the 2008 catalog, they have some new HR LSx cams for centri blowers and they are all running 16 degrees extra on the exhaust, increasing LSA's from ~114 to ~116 as duration goes up. You might want to talk to them and work to translate that into a solid roller with similar specs, if they can tell you why they work.
Jim
Try asking this same question over at speedtalk.com, there are some really bright engine folks over there that will give their inputs.
I decided to solid roller on the 383 and now a bigger one on the 434. Maybe worth considering as well. On the 383 did 230/236 on 112, the 434 has 242/248 on 115 after a lot of research and Q's. For lif I am trying to get the max out of the heads I have but still have the springs last on the street. Net lift on the 383 was .574/.583 with E-tec 200's. The 434 with new AFR235cc Eliminators and T&D shaft rockers wil have net .630"I/.674"E. No results on the 434 yet - just got the YSi yesterday.
On Comp Cam's page, IIRC the 2008 catalog, they have some new HR LSx cams for centri blowers and they are all running 16 degrees extra on the exhaust, increasing LSA's from ~114 to ~116 as duration goes up. You might want to talk to them and work to translate that into a solid roller with similar specs, if they can tell you why they work.
Jim
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07-29-2009, 01:10 PM
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Many cams work great, that isnt what I am asking though.
I'm asking what difference say would that cam be on a 110LSA, and your 116LSA for example ?
Or a cam with less lift, but much longer duration. Would a less aggressive profile in terms of lift offer more reliable valvetrain, and easier high rpm ability for example ?
Or doesnt it matter too much ?
I'm asking what difference say would that cam be on a 110LSA, and your 116LSA for example ?
Or a cam with less lift, but much longer duration. Would a less aggressive profile in terms of lift offer more reliable valvetrain, and easier high rpm ability for example ?
Or doesnt it matter too much ?
