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%Nitro/RPM Tests (Two and Four Stroke) - 3/8/2006 7:05:17 PM   
TimC



Posts: 2257
Joined: 1/7/2003
From: Lone Pine, CA, USA
Status: offline 		For the lack of something better to do, I decided to do a check on what real advantages are gained by more nitro in the fuel. I realize that this is not a valid scientific test, just some fooling around on the test stand. The engine is a .61FX. The prop is a 12x6 APC. I did go to an A5 plug for the 20%, #8 for the others.
Powermaster 20% YS peaked 12,090. Wildcat 15% peaked 12,000. Powermaster 10% peaked 11,790. Powermaster 5% peaked 11,720. ( The 5% is an old can I might have dumped some 15% into and contaminated it for the purpose of this test.) This is at 4000' elevation and about 50 deg. temp. Transition and ease of starting was the same for all fuels, good.
See post #26 for the test with a four stroke.

< Message edited by TimC -- 3/9/2006 6:27:21 PM >
       Post #: 1

RE: %Nitro/RPM Tests - 3/8/2006 7:15:50 PM   
britbrat


 

Posts: 3299
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From: Deep River, ON, CANADA
Status: offline 		Got any FAI fuel? That would be interesting as well. My bet is that the biggest jump is from 0 - 5%.

(in reply to TimC)
       Post #: 2

RE: %Nitro/RPM Tests - 3/8/2006 7:23:36 PM   
TimC



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Joined: 1/7/2003
From: Lone Pine, CA, USA
Status: offline 		Negative on the FAI fuel britbrat. I have always been a nitro junky and only had the 5 and 10% for a few of my engines that can't tolerate more. I may have to re-think this nitro fetish.

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       Post #: 3

RE: %Nitro/RPM Tests - 3/8/2006 7:43:29 PM   
daveopam



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From: ELK CITY, OK, USA
Status: offline 		I use the 30% in one of my four strokes for the spool up. The max RPM for the kind of flying I do is not important. The max RPM is a good indication of horsepower and thats what you were going for. (I assume anyway) I use a 15x4W on a .82 with 30%. On 15% with the nose pointed up the 15x4W bogs down. With a 14x4W either fuel has good spool up and flys the plane fine. The 15" prop just has a lot more pull.
I am not trying to discount your findings. I am just saying that when using the biggest prop possible sometimes the 30% is needed.

David

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RE: %Nitro/RPM Tests - 3/8/2006 7:49:06 PM   
Cyclic Hardover



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Joined: 5/7/2002
From: New Mexico, USA
Status: offline 		Thats a pretty basic test which I'll go along with. Those who are at sea level can probably add about 12% to those numbers. If you have time on your hands , how about this one.

Most of us already knew that anincrease innitro content will give an rpms boost but is nice to see what you did with the same engine and prop with different fuels. Looks like the biggest difference was going from 10 to 15%.

Now try this, using the same 61 fx, switch props from your 12/6ma to a 12/6 apc and lets see what the difference is.

THen if you have one or can borrow one, lets see the difference between a stock muffler and Perf Specs Ultra Thrust.

I know you will see an increase individually on all three but add up the difference and see if you get the overall increase with the 61fx , apc prop and whatever fuel.

< Message edited by Cyclic Hardover -- 3/8/2006 8:02:49 PM >

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RE: %Nitro/RPM Tests - 3/8/2006 8:02:41 PM   
TimC



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Joined: 1/7/2003
From: Lone Pine, CA, USA
Status: offline 		After further checking, the Powermaster 5% Synthetic/Castor Blend seems to be unadulterated. Cyclic H., the muffler is a Mac's one piece. It's said to be about the same as the stock muffler with the baffel removed. I don't have a stock muffler to try. Only a pitts.

< Message edited by TimC -- 3/8/2006 8:08:32 PM >

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RE: %Nitro/RPM Tests - 3/8/2006 8:31:56 PM   
britbrat


 

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Status: offline 		This is becomming very interesting. Do you know anyone near enough to borrow a muffler -- and some FAI fuel?

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       Post #: 7

RE: %Nitro/RPM Tests - 3/8/2006 8:40:48 PM   
Richard L.



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Joined: 7/28/2002
From: Redmond, WA, USA
Status: offline 		You will get much bigger differences when running the same test using either a Saito or a YS.

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(in reply to TimC)
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RE: %Nitro/RPM Tests - 3/8/2006 9:05:39 PM   
TimC



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From: Lone Pine, CA, USA
Status: offline 		Britbrat, I live pretty much in the middle of nowhere, so it's a no-go on FAI or the stock muffler. I do have a Saito 30 that I could easily run the same test with. I was doing this to compare different nitro %'s rather than tuning mods. Richard, I assume this is due to the lower compression ratio of Saitos and YS's?

< Message edited by TimC -- 3/8/2006 9:07:53 PM >

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RE: %Nitro/RPM Tests - 3/8/2006 9:20:28 PM   
Richard L.



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From: Redmond, WA, USA
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quote:

ORIGINAL: TimC

Richard, I assume this is due to the lower compression ratio of Saitos and YS's?

I'm not sure, but both brands yield much more rpm increase the higher you go up on nitro percentage.


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RE: %Nitro/RPM Tests - 3/8/2006 9:58:29 PM   
Harry Lagman


 

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From: Auckland, NEW ZEALAND
Status: offline 		Good testing work, Tim. Thanks for sharing. Also, it's great that you used a pretty much industry-standard prop - it's always frustrating when someone quotes figures for an engine running some weirdo prop no-one has ever heard of that went out of production in 1968.

Looks like the performance sweet spot is 15% on your engine. 12k for a .61 with that prop at that altitude is pretty healthy It's about 700 rpm stronger than an Evolution .61 we tached at sea level the other day.



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RE: %Nitro/RPM Tests - 3/9/2006 12:17:20 AM   
britbrat


 

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quote:

ORIGINAL: Harry Lagman

Good testing work, Tim. Thanks for sharing. Also, it's great that you used a pretty much industry-standard prop - it's always frustrating when someone quotes figures for an engine running some weirdo prop no-one has ever heard of that went out of production in 1968.

Looks like the performance sweet spot is 15% on your engine. 12k for a .61 with that prop at that altitude is pretty healthy It's about 700 rpm stronger than an Evolution .61 we tached at sea level the other day.




I think that he needs a new tach

(in reply to Harry Lagman)
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RE: %Nitro/RPM Tests - 3/9/2006 12:21:58 AM   
Harry Lagman


 

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How's your one going?

< Message edited by Harry Lagman -- 3/9/2006 12:22:42 AM >

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RE: %Nitro/RPM Tests - 3/9/2006 12:25:32 AM   
STG



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Joined: 7/3/2003
From: New Richmond, WI, USA
Status: offline 		Keep in mind when testing nitro and performance that if the motor timing(or compression) is optimized for low nito adding nitro wont help and if it is optimized for high nitro adding nitro will help a lot.



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RE: %Nitro/RPM Tests - 3/9/2006 12:49:43 AM   
britbrat


 

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quote:

ORIGINAL: STG

Keep in mind when testing nitro and performance that if the motor timing(or compression) is optimized for low nito adding nitro wont help and if it is optimized for high nitro adding nitro will help a lot.




Details -- details --

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RE: %Nitro/RPM Tests - 3/9/2006 2:33:41 AM   
downunder



Posts: 3198
Joined: 10/10/2002
From: Adelaide, AUSTRALIA
Status: offline 		It's good to see someone doing some actual tests where the only variable is the fuel and it's done with a prop that's in line with what most would use too. I'd take a bet that if Tim can get some FAI fuel then the revs will be somewhere around 11,650. What would also be interesting is checking the run time to get some idea of fuel consumption. Most sport 2 strokes (at least, from those that I've checked) have got very similar compressions so the results Tim's getting should be much the same for others.

Four strokes are a bit strange though because some seem to have very low compressions. I can only guess this is done to force the use of high nitro fuels to get reasonable HP for their size. Early Saitos had very high compressions and I'd bet the Lasers do too.

I hope a few more chime in here with their own tests. I can't, I'm stuck with only FAI fuel

(in reply to britbrat)