Q-500 Racing Discuss AMA 428, AMA 424, and any other variants of Quickie 500 racing

Engine tuning

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Old 06-17-2008, 09:04 PM
  #1
wkevinm
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Default Engine tuning

I have been looking for arcticles on tuning engines to understand the best way to get the most power from a Nelson Q500 engine. In Canada we race Q500 with a Nelson short stroke engine with an exhaut that has the inner pipe removed. This tames the engine down a bit I am told taking a few thousand RPM off of the peak. I beleive that since the engine was designed to run a pipe the timing of the engine is less than optimal when not using the pipe, so given that assumption what can be done to get the best performance from the engine under this new operation. It seems to me that some of the faster engines have a different sound, perhaps my imagination but then again maybe no, perhaps others have found the right set up tht may include more than propellor selection.

Is there an arcticle that describes engine design and how to best tune the engine for peak racing performance?


Kevin M
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Old 06-17-2008, 09:32 PM
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daven
 
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Default RE: Engine tuning

Kevin,

Your group is the only one that I am aware of that has dis-allowed the use of the inner pipe. Because of that, most of the US racers won't be much help since we have never run the motors that way. I will say, you can always hear the growl of a motor running a little bit better than the rest. Your hope is that it is on your plane

Hope you hear something from the rest of the Canucks, but I'm not sure they will want to share their secrets...

Your best bet is to do some objective testing with props and head/liner settings. Telemetry devices work well, and so do consistently measured radar readings. Keep messing up the variables till you find something that works for you. Its not rocket science, just takes a considerable amount of time and determination. Many racers would be hesitant to share what they have worked hard to learn.
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Old 06-17-2008, 09:47 PM
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Bill Vargas
 
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Default RE: Engine tuning

Kevin, about the only way to figure out the best way to tune your engine is to get out and practice with it,,, try different props,,, needle settings like a 1K rpm pinch, a 500 rpm pinch,,, etc. Never launch your nelson at peaked out RPM, it will melt away,,, and try to use the same fuel that your local Races are providing(makes no sense to practice with 5% no name brand when 15% name brand stuff is provided). Keep notes on what works and what doesn t,,, notes about weather in the morning and afternoon.

There really isn t nothing about tuning your engine,,, its all about you getting to know and understanding it with practice


BV
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Old 06-18-2008, 05:25 AM
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Default RE: Engine tuning

Have you tried calling Dave Shadel? He builds them right? He must have some baseline starting point on timing and props, even RPM ideas.
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Old 06-18-2008, 11:19 AM
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Default RE: Engine tuning

I agree with Randy. Also check with some of the guys that seem to have the fastest stuff in your area. Believe it or not, the more than likely will be willing to tell you exactly how theirs are setup. There are fewer secrets in racing that many would like to think.
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Old 06-18-2008, 05:04 PM
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Default RE: Engine tuning

In theory you should be able to run less head clearance or volume since you're not getting the supercharging effect of the tuned pipe. Maybe the fast guys are running a FAI type head (no nitro - higher compression).
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Old 06-19-2008, 11:20 AM
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Probably not. We run on the same fuel as you guys, 15% Powermaster. Kev, I found the best readings with the 8.75X7.5 APC with a 800-1000rpm pinch up from the exhaust line. I don't know if this translates into the best air speed yet with a W or NN prop. Are you coming to P.A. this weekend? Weather looks good. I like what Bill says: experiment, experiment.
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Old 06-19-2008, 01:55 PM
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Thanks to all for the opinions, I guess I was hoping for the easiest path, as in all things it appears there is no substitute for hard work.

Frequentcrasher, I will be in PA along with the other Edmonton folks, we are hoping for a 1,2,3, fast time finish, see you there.

KM
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Old 06-19-2008, 03:07 PM
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Default RE: Engine tuning

Kevin,

Not all setups work the same on all engine/plane combinations. They are all a little different.

EagleTree has some neat little data loggers that are relatively inexpensive if you don't go with the real time data. I haven't tried them, but they look like they could be a very usefull tool for gather real data.
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Old 06-20-2008, 07:45 AM
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Default RE: Engine tuning

Out of curiosity... how much speed/rpms is lost by removing the inner pipe?


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Old 06-20-2008, 11:33 AM
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Default RE: Engine tuning

On the 8.75X7.5NN I'm getting around 19200 on the ground. I really can't tell you the speed, but a guess is topped out around 225 Kph? I think that's around 140mph for you stars and stripers. We race the short course for quickee.
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Old 06-20-2008, 11:37 AM
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1-2-3? Only if Kev U. stays away from my plane around #1! Start chanting together as you pass North Battleford "No more mid-airs, no more mid-airs" and don't stop till you get to the field. See you there...
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Old 06-23-2008, 09:56 PM
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wkevinm
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Default RE: Engine tuning


I cannot say how much is lost, although I have been told 2-3,000 RPM. I purchased a couple of engines from e-bay when the change was made 2 years ago and get about 18,500 on an 8.75 X 7.75NN prop. Others with newer engines seem to do better. It appears, in my opinion, that the engine out performs initial expectations and there is a speed creep occurring as people experiment with various propeller combinations and I am sure different head shimming and timing.

The initial idea for the engine was to have a setup that would replace the previously preferred Webra Speed 40 with an ultrathrust muffler, Roy Andrassy experimented with the Nelson SS engine to see how it could be detuned so it could compete but not dominate the series. Since the Webra was long in the tooth and there were some incentives put n place for people to switch most in the district quickly moved over to the Nelson / detuned pipe combination. Some of the selling points were;

-The Nelson is a design for purpose racing engine and was robust enough to be a reliable performer, the detuning even made a better case for this.
-The Webra was no longer in production and new engines were not available to new entrants.
-The Nelson could easily be converted with a tuned pipe to compete in the NMPRA 428 event.

Since the engine has been in use for 2 years most appear to like the trouble free operation and the new LS has made them more plentiful for people starting out. The intro of the LS version however may take away from the argument of using this engine in the 428 class competitively but this is only of interest for a small group anyways.

Airplanes used range quite a bit from Vipers to Seekers, Neme-Q, Vortex, Slingshots, Kase and the like and some of the better built woodies are doing well. I cannot say I have seen any Q500 airplane fail under flying stresses. In the end I think the engine is a good fit for this district, since the flyer numbers are not large enough to hold a 424 and 428 event regularly but the Nelson configuration seems reliable and affordable and at the same time people can start out with an engine other than the Nelson if they wish (although not many do).

KM


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