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  #111  
Old 08-28-2020, 07:10 AM
sailvi767 sailvi767 is offline
 
Join Date: Sep 2010
Location: Charlotte NC
Posts: 1,288
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I am looking at installing a surefly as a mag replacement on one side of a IO540 parallel valve with a RSA 10 and 9.5 to 1 pistons. I have looked through all the pubs and read the threads. If I keep the left mag timed at 23 degrees BTDC how would most run the surefly? It appears that if I ran it with variable timing and set the baseline at 23 I would not see more than 34.5 degrees of advance with a RPM max of 2700. Am I understanding this correctly? It also seems with my preferred cruise RPM of 2200 the surefly advance curve would be close to what most suggest is optimal for LOP operations.
G

Last edited by sailvi767 : 08-28-2020 at 07:15 AM.
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  #112  
Old 08-28-2020, 08:49 AM
pecanflyboy pecanflyboy is offline
 
Join Date: Nov 2011
Location: Granbury, Texas
Posts: 135
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Quote:
Originally Posted by DanH View Post
To be clear, we're talking about advance here, not product. There's much to like about the product.

Regarding advanced timing, for the average user the downside is higher temperatures for little return.

For the advanced user, no published advance schedules.

Is variable advance a bad thing? Of course not. It can be a useful tool.

You have a thread going right now:

https://vansairforce.net/community/s...0&postcount=17

Set your switches to fixed timing, and see what happens.
That's a fair opinion, and I appreciate your comments. What were your results when you tested this with the Surefly?

In my situation I've tested both:

Fixed timing: Same numbers as the magnetos but able to get farther LOP with a smooth running engine.

Variable timing: SIM is in fixed timing until below 25", so my only changes are at cruise. At cruise altitude (below 25" MP, WOT, 10,000', 8.0gph) at 100 ROP I've recorded a 10 increased CHT and 5 increase in oil temperature, and better speed (versus fixed timing cruise). Once LOP I can cool the engine much better than in fixed timing by smoothly going 50-100 LOP, 6.2-6.5gph, while maintaining better speed than with fixed timing.

So, in my experience, the variable timing is well worth the performance gains.

You referenced a thread I have going about oil temperature cooling. This airplane has always had issues with cooling, long before I installed the Surefly and has no bearing on this discussion. Before taking out the big hammer and simply installing a bigger cooler, I fixed many issues which helped dramtically. All this was done before the Surefly's. I would still like to get the oil temperatures down, even though they are within limits. When I installed the Surefly's, I tested in both fixed and variable timing. The only temperature changes I observed was ROP cruise and cooler LOP cruise temperatures, as mentioned above. Good point to bring up, as one might have the opinion that I'm struggling with temperatures because of the Surefly, but I'm not.

$

Last edited by pecanflyboy : 08-28-2020 at 08:58 AM.
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  #113  
Old 08-28-2020, 11:47 AM
jdmrv7a jdmrv7a is offline
 
Join Date: Jan 2018
Location: DFW
Posts: 72
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I too installed a Surefly in place of the impulse mag on my RV 14-A. Quicker starts hot or cold and I spent 2 hours installing it after getting a manifold hose T-connection. I like the vacuum advance at cruise and currently collecting performance at different altitudes. Great customer support in Granbury if you have questions.
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  #114  
Old 08-28-2020, 01:20 PM
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DanH DanH is offline
 
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Location: 08A
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Quote:
Originally Posted by pecanflyboy View Post
That's a fair opinion, and I appreciate your comments. What were your results when you tested this with the Surefly?
The system I've been flying since early 2016 is dual map. It also allows setting any advance schedule desired at 100 points.

With dual maps, I keep one set for 23 fixed (angle valve 390), and the other holds a schedule with advance based on MP and RPM. The current schedule is below. I can change back and forth in flight with the flick of a switch, which makes comparison easy.

For sure, the angle valve doesn't want as much advance as the parallel valve engines.

Quote:
Fixed timing: Same numbers as the magnetos but able to get farther LOP with a smooth running engine.
Yep. And it starts better hot or cold, etc.

Quote:
Variable timing: SIM is in fixed timing until below 25", so my only changes are at cruise.
In other words, choosing a fixed or advancing schedule would make no difference at all to a fellow who generally flies below, what, 6000 or so?

Quote:
At cruise altitude (below 25" MP, WOT, 10,000', 8.0gph) at 100 ROP I've recorded a 10 increased CHT and 5 increase in oil temperature, and better speed (versus fixed timing cruise).
Average when ROP was 2.5 F CHT increase per degree of advance for a very similar engine.

So what is timing advancing to at that point, and how much faster do you go in return?

BTW, 8 gph is remarkable for 100 ROP at that altitude. Pulled to some very low RPM?
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Last edited by DanH : 08-28-2020 at 01:24 PM.
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  #115  
Old 08-28-2020, 02:19 PM
pecanflyboy pecanflyboy is offline
 
Join Date: Nov 2011
Location: Granbury, Texas
Posts: 135
Default Apples to Oranges

If you are using a different ignition to form opinions about the Surefly in variable timing mode, it seems you are comparing apples to oranges, especially if your system is advancing differently than the Surefly. Is your advance the same as the Surefly's proprietary advance? Based on your question about the advance below 6000', it sounds like we are both unaware of the Surefly advance details.

Why is it proprietary? If it was public knowledge, Shanghai Ignitions could copy it and streamline the certification process with the FAA, using Surefly's realiability history in the field. (McDonald's Special Sauce).

If your opinions are based on experience with a different ignition system, then it's a shame that I read of users changing their base timing, avoiding varible timing, or not buying the SF based on these opinions.

It's up to all of us to make informed decisions. These forums are an excellent source of information. But, be sure to give the manufacturer a call, if you have questions.

$$
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  #116  
Old 08-28-2020, 04:37 PM
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rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
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All that matters is total advance at any given MAP, RPM and AFR for MBT.

Ignitions which don't allow timing adjustment with regard for AFR cannot be fully optimized for LOP cruise since flame speeds varies considerably with AFR. I've published plenty of graphs here to illustrate this fact.

There are already too many ignition systems on the market with secret or proprietary ignition curves promising amazing things and we know of some that are worse than fixed timing mags.

A few hours of test flying with an ignition system having variable timing capability will get you 95% of the way there. No big secret sauce.

As with engines, airframes or most other things that fly, no ignition system is proven in my books until hundreds of examples have accumulated tens of thousands of hours in the real world and that feedback is in.

Other companies have been in this market for years or even decades and sold many thousands of EIs collectively. Surefly is the new kid on the block. Maybe they have it all right the first time around, maybe not. Only time will tell.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.9 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ



Last edited by rv6ejguy : 08-28-2020 at 05:35 PM.
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  #117  
Old 08-28-2020, 10:50 PM
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DanH DanH is offline
 
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Location: 08A
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Jimmy, let's skip the straw man stuff and get back to the question at hand.

Regarding variable timing, you wrote..

.At cruise altitude (below 25" MP, WOT, 10,000', 8.0gph) at 100 ROP I've recorded a 10 increased CHT and 5 increase in oil temperature, and better speed (versus fixed timing cruise).

...but forgot to tell us how much better. So help the readers make an informed decision. What is the timing BTDC at that point, and how much faster do you go?
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Barrett IO-390
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  #118  
Old 08-29-2020, 10:33 AM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by DanH View Post

Regarding variable timing, you wrote..

.At cruise altitude (below 25" MP, WOT, 10,000', 8.0gph) at 100 ROP I've recorded a 10 increased CHT and 5 increase in oil temperature, and better speed (versus fixed timing cruise).
I'd be surprised if there is much to be gained with advanced timing running at 100 ROP and 25". Never seen that in any of my RV-10 flight testing on a PV engine.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.9 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


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  #119  
Old 08-29-2020, 01:21 PM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
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Quote:
Originally Posted by sailvi767 View Post
I am looking at installing a surefly as a mag replacement on one side of a IO540 parallel valve with a RSA 10 and 9.5 to 1 pistons. I have looked through all the pubs and read the threads. If I keep the left mag timed at 23 degrees BTDC how would most run the surefly? It appears that if I ran it with variable timing and set the baseline at 23 I would not see more than 34.5 degrees of advance with a RPM max of 2700. Am I understanding this correctly? It also seems with my preferred cruise RPM of 2200 the surefly advance curve would be close to what most suggest is optimal for LOP operations.
G
Too many variables here to suggest that you are going to end up with an "optimal" advance with the canned SF curve. Maybe, maybe not. One thing for sure, the single fixed magneto is going to drag the total effective timing down to something less than the SF max advance is going to give you. Is that composite timing right for you? Only flight test -with the ability to change timing on the fly - will tell you for sure. Also beware of the 4 banger curves - few of them cruise at 2200 RPM like we do with the 6 bangers. The difference in piston speed is a significant factor in timing requirements.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
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  #120  
Old 08-30-2020, 07:32 AM
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DanH DanH is offline
 
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Just to be clear, allow me to again state specifics.

(1) Regarding advanced timing, for the average user the downside is higher temperatures for little return. A high percentage of owners fight cooling issues. Adding to the problem is pointless.

(2) For the skilled user, no published advance schedules.

(3) Advance settings optimum for LOP are too advanced for ROP.

(4) Advance schedules optimized for parallel valve engines are generally too advanced for angle valve engines.

Again, this is NOT a brand criticism. These issues apply to other popular ignition system brands too.

Surefly installs faster than any system I've seen, and allows the user to select fixed timing. Those physical facts make it an easy EI replacement when Slick mags time out...again, in particular for the average fun flyer. "Easy replacement of Slick mags" was Surefly's #1 design goal, and they hit that nail square on the head.
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