Author Topic: Rev Boost  (Read 880 times)

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Offline Al Smith

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Re: Rev Boost
« Reply #10 on: January 12, 2014, 10:55:45 am »

I've never seen the need for that in any of my limbing saws.
I took a Mastermind ported S25CVA to the woods last Saturday and it was all the limbing saw I could ever need!!!! ;D
 Mike
Those little saws were the icons of limber/climbers before the Stihl 020T came on the scene .

Offline 660magnum

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Re: Rev Boost
« Reply #11 on: January 12, 2014, 10:42:46 pm »
The conclusion I've come to with the Rev Boost is that there is a lot of confusion.

My 545 and 550 were new this time last year.

My Saws appear to not have Rev Boost for the 550 just goes up to around 13,900 and stays there.

My 545 goes up to around 13,400 and stays there.

Now I have a near by friend with a older 550 and his seems to maybe go beyond 14,000 for not as much as a second and then the coil goes into limitation. His muffler is ported. This happens so fast is all you see is the tach go nuts above the high 13,000's. If it has Rev Boost, it is for less than the resolution of my Fast Tach.
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Offline Magnus

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Re: Rev Boost
« Reply #12 on: January 13, 2014, 04:28:42 pm »
Lets see if I can get the thoughts in to words...

There is no fixed limiter as on the older saws in Autotune systems. It has its curve to follow, but will adapt as best it can after current conditions.
These current conditions are remembered and will change the curve if it works as intended.
So you can by your handling and work get different performance out of it depending on how settings are at the time.
Fuel systems inlet valve opens and closes a lot of times/second and follow a curve along with the timing.
They interact in a way...
There is rev control, fuel control that is to follow a certain set of parameters in different rpm ranges.

When I was told this (by the engineer in charge of 550 project) I found it hard to believe. An hour later we were ten guy's running spanking new saws in same wood cutting cookies to get a feel for the saw and prepare it for next day's felling.
I ran out of fuel first of all, had perhaps some more cookies cut, but ran out of fuel when the others was about 3/5 thru first tank.
I waited a bit and switched saw with another guy, fueled up and it ran very different. He said there was more power in mine and I agree.
5 min after "his" saw ran the same and we both ran out of fuel almost at the same time.
Our two saws ran out of fuel first, others some time after and a few quit before as it got dark.
I wish we could have hooked them up and looked at the settings...

Chainsaw nut!

Offline 660magnum

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Re: Rev Boost
« Reply #13 on: January 13, 2014, 04:41:15 pm »
I listened to maybe a couple dozen 550XP limbing videos last night and I didn't hear any ""Rev Boost" in any of them.
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Offline Magnus

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Re: Rev Boost
« Reply #14 on: January 13, 2014, 04:52:58 pm »
It is a bit harder to hear 1000rpm differance when it is on 12000+ than 7-8000.
I can't do it but I can see differance and hear it in wood, but then it is not 14000..
To me it is not so important how much rpm there is cutting air, I am more interested in what happens when it hits wood and in cut.
RPM under load is not the same as in air revving. Other factors get involved.
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Offline SawTroll

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Re: Rev Boost
« Reply #15 on: January 14, 2014, 10:03:57 am »
I have a hunch what this could be about, but am not sure enough to post it before Spike has joined here.....



 ???  Please tell us what your hunch is?   ??? This ought to be a good made up one.  ::) ::)

I'll tell you why I posted it. So folks can learn from spikes post.

I have forgot what I thought about - but a fast trigger response always is nice, and specially when limbing!

That is of course obvious, so it wasn't what I was thinking about - sorry!  :D