stunthanger.com
Engine basics => Engine set up tips => Topic started by: Steve Helmick on August 23, 2011, 05:43:37 PM
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I'm not sure how many different makers of CF stunt pipes are currently being made, but I know of Smith/PA, Brian Eather, and "ES" pipes (from Utah) are. I know Richard Oliver, Windy U., and Bill Werwage used to, or perhaps still do make 'em. I'm sure there are some others, somewhere.
My question is this: If you find the location of the first baffle and mark that, will the initial "bench trim" length be the same, given the exhaust timing? Will a minor engine size revision change it, such as going from a .46 to a .51, if the exhaust timing is the same? In other words, will Randy's chart work for other brands? Still talking about initial bench trim length, remember. ??? Steve
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Short answer,, No. Too many other variables other than exhaust timing that determine how any given engine will respond to the pipe.
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Yea, I ran into this when I went from an Eather pipe to a Randy pipe. I finally got it worked out, but it took a bit. Quite a lot of pipe length variation.
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So, do other pipe makers give you any kind of chart (like Randy Aero's) or any length info to help get a leg up on it and not destroy your engine by having the pipe too short to start? ??? Steve
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So, do other pipe makers give you any kind of chart (like Randy Aero's) or any length info to help get a leg up on it and not destroy your engine by having the pipe too short to start? ??? Steve
You aren't likely to destroy the engine no matter what you do to the pipe, unless you do something else bad, too, at the same time.
Brett
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So, do other pipe makers give you any kind of chart (like Randy Aero's) or any length info to help get a leg up on it and not destroy your engine by having the pipe too short to start? ??? Steve
I know that Brian Eather will supply information upon request, so just ask him mate!
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I'm not sure how many different makers of CF stunt pipes are currently being made, but I know of Smith/PA, Brian Eather, and "ES" pipes (from Utah) are. I know Richard Oliver, Windy U., and Bill Werwage used to, or perhaps still do make 'em. I'm sure there are some others, somewhere.
My question is this: If you find the location of the first baffle and mark that, will the initial "bench trim" length be the same, given the exhaust timing? Will a minor engine size revision change it, such as going from a .46 to a .51, if the exhaust timing is the same? In other words, will Randy's chart work for other brands? Still talking about initial bench trim length, remember. ??? Steve
The critical factors that you have some control over are the exhaust duration and the position of the reflecting surface (length). If tuning to the first baffle is the right surface, then you can measure to the first baffle, and then figure it out. If you are tuning to the conical tail cone, measure to the centroid of the cone (2/3 of the way from the "peak" to the base of the cone). Adjust from there.
Brett
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This is a "Utah Pipe" that I bought from Norm W. There's a red line where the 1st baffle is, but any reference point is going to be a help when tuning, even one that isn't at the critical feature...tough to mark or measure to the centroid of the cone.
How would one know if the pipe length needed to be setup off the 1st baffle or the end of the pipe, and why? I always heard guys talking about measuring off the first baffle, but I'm not always sure what brand of pipe they're using, either. H^^ Steve
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Hey Steve:
I also got one of those Utah pipes from Norm W. Will be trying it out in about a month on an Enya61RE / SV-11 ARC. What engine are you trying yours on ?
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Allen...Well, initial idea was to put it on a .46LA on a Pathfinder. Piped Profile models seem to be the rage in the NW. You might recall that Igor ran a .46LA on a pipe in a WC, before he went electric. It appears that the timing is about the same as a PA, so I'm hopeful. I'm not going to cant the engine, just strap it on like Dirt's "Wimpact". There is also the possibility of using a G.51 or Magnum .53 in the Pathfinder, with the pipe.
How would one know whether a particular pipe needs to be tuned off the first baffle or something else? Is this something like gurls, where a guy just has to figure it out for himself? Somebody oughta write a book on both subjects. LL~ Steve
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Steve, check put Macs web site advice -
http://www.macspro.com/tuning.asp
It basically states that you compare the open faced exhaust's performance to that of a full pipe length's performance by using the prop, rpm, fuel etc that you intend to use in flight and look for any increase in rpm. Seems fair enough to me.
The 'measuring from the first baffle' idea simply seems more like a convenient method to show where the testing proves the overall pipe should be positioned - it gives you a marker for reference.
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You generally tune typical stunt baffled pipes to the first "reflective surface", This is normally the first baffle encountered. However I have seen several people that wanted to tune off of the second baffle. I have even seen people break out the first baffle and try to tune off of the rear convergence cone, or the only baffle left.
Others just run them where ever... I you do that it is better to run the pipe long, I have seen many problems with running pipes slightly short.
Randy