Latest and greatest timing and deck height?

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Kurt Bozarth
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Latest and greatest timing and deck height?

Post by Kurt Bozarth »

Anyone care to share their NQ40 LS setups?

Kurt
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rocket
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Re: Latest and greatest timing and deck height?

Post by rocket »

The higher timed guys, 7 under 11, 12, 13 over. The factory setup is 3 to 5 under 13 over. The lower timed guys nothing under 15, 16 over. The higher timed guys favor the 5 prop. Lower timed guys 6 and 7 prop. You wanna play with hotter plugs... 10 under 15 to 17 over. 5 prop. The difference in the no shim under setup and 6 thou under is 2 degrees in exhaust timing. You should measure the stroke. The norm is 188-9 tdc but some cranks have been measured with more.
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moe4sho
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Re: Latest and greatest timing and deck height?

Post by moe4sho »

Kurt, in Phoenix this year I ran two different engine setups: 190/.019 and 194/.024 not sure if this is a significant difference. Rocket would know. I used a 7.6 prop on both and the same tuning. I ran the same time with both. I only commented on this because I'm interested in how much engine setup matters. The fast guys always go fast. Is that engine setup or pilot?
Kurt Bozarth
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Re: Latest and greatest timing and deck height?

Post by Kurt Bozarth »

I'm not looking for that last little bit of speed out of a motor (we all know I need more than that!) but rather some starting points for two motors that I bought used that don't seem to run that well. Thanks.

Kurt

P.S. Thanks Rocket for all the numbers...I'm waiting for my wife to decipher them for me and then I might understand.
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rocket
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Re: Latest and greatest timing and deck height?

Post by rocket »

What prop and ground rpm.
Does it surge, struggle on the ground.
No unload in the air.

The most common problem is bad fit. Poor breakin. The second is the liner. Not all liners are created equal. I would start by cleaning the piston up with some mothers polish. Then some 1500 in the liner. Roll the liner back and forth on the edge of the bench while moving the oiled up 1500 back and forth inside the liner. You want to see a fine cross hatch. You won't damage the liner as 1500 for a few seconds will only remove a micron or less. Some folks don't touch the liner. If you had a GOOD running motor before and it started going south then just change the piston and rod. That's not the case here, so just start over... Put it back to stock with the shims. A 3 thou under the liner a 8 and 5 thou under the head. This will give you 191 and 19. Go through the breakin again. 5 prop running just before 2 stroke for a couple runs on the ground. Too rich, no heat, not good. Also if you can add some castor to the breakin fuel. 5oz per gallon is a good mix. I'm on the fence with test stands. do the breakin in the plane, do a couple runs on the ground first. When you fly make sure it stays rich for a dozen runs. This includes the ground runs. I just fuel and go, fuel and go, fuel and go. Do the verano in the air. Load and unload. Cuban 8s, big ones. Don't look for peak until the breakin is done. If all is good you should see high 25s low 26s on the ground.
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rs-ssfan
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Re: Latest and greatest timing and deck height?

Post by rs-ssfan »

Rocket you indicate that .003 under the sleeve and .013 under the head will put you at .191/.019. Do you find that to be the case on every engine you set up? I don't, so I'm trying to figure out if I'm doing something wrong when I'm measuring my engines. I have 3 engines, #1 has no sleeve shim and I measure it at .190, #2 has no shim and I measure it at .189 and #3 has a .003 with a measurement of .190. I've measured them both at TDC and BDC and subtracting the stroke and come up with the same measurement.

Thanks,
LF
rs-ssfan
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Re: Latest and greatest timing and deck height?

Post by rs-ssfan »

One more question Rocket, do you look for a prop that gives you the 25s/26s or that should be the judge as to whether or not it's a good engine. In other words on "this" prop I should get low 25s and if I don't there is a problem with the engine and I should get another one.

LF
killerd
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Re: Latest and greatest timing and deck height?

Post by killerd »

I would agree that while most of the motors might average 187 with no shims, there are exceptions to the norm. I have one is measures 184, 180, and 189 with no shims which RR did reference in the first answer. I totally agree the break in of the motor is extremely important and would admit sometimes there is 1 motor that is just a cut above all others. Thankfully we have a good attrition rate so that pilot has a small window of time to kick but before that combination is in the dirt.

SoCal DK
rocket
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Re: Latest and greatest timing and deck height?

Post by rocket »

There's different ways to find tdc. Darrol sells a 20thou shim. Others do their best to get the piston to the top by smashing the motor on wood to drive the piston up higher. You can heat the cylinder with a torch, with the piston at BDC, cylinder is hot and expanded piston still cold you can find tdc before the piston heats up and binds. The easiest way, You can castor oil up the piston and turn it to tdc. Pull the head, rock the prop back and forth you will see the cylinder move up and down. I use head shims or you can use feeler gauges measure the space between the cylinder and case. Now measure tdc from the piston to the cylinder. Subtract the feeler gauge numbers. This is your unloaded TDC. All the heads are 185 thou. Now subtract the 185 from your final no shim clearance number. If you don't have castor "I use it for all assembly of motors" you can get it at CVS, Walgreens or other drug stores. In the laxitive section for old people or the baby health section, laxative section. Some baby's need help pooping.
Props, another gray area. 28.500 in the air. Rumor has it that's the max rpm the motor will turn. 3000 rpm is what it unloads after you take off. So, 25.5 on the ground is what you should leave at. Again, not confirmed by me just stuff I've heard but sounds right.
Plugs, the N plug works well, but, might not be the best choice for certain setups. Lower timed setups like this plug. Higher timed setups might favor a different heat range plug like the ones available from merlin.
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rocket
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Re: Latest and greatest timing and deck height?

Post by rocket »

Looking for heat.

Your turning 25 plus otg, planes fast but not unloading hard. You land, check the plug only to find its brown and the element looks like terry fraiser on a 6 pack of cheap beer. Your over compressed. Raise the head 1 thou at a time until the plug is light brown at worst, or still new looking at best. This was the most asked question at the nats. Craig Corsen saw the best results after asking why as did others.
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rocket
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Re: Latest and greatest timing and deck height?

Post by rocket »

Lonnie, all props are not the same. If your motor is turning lower rpm than what you're looking for By all means try a different prop. If no change try a different plug. Keep a needle or t pin to put the plug element in the middle of the body. An element pushed up against the side or an element that's been squished together by an over compressed motor will yield lower rpm.
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Terry Frazer
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Re: Latest and greatest timing and deck height?

Post by Terry Frazer »

:lol: :lol: :lol: spell my name right dude.
rs-ssfan
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Re: Latest and greatest timing and deck height?

Post by rs-ssfan »

Rocket, thanks for the information.

Your peak RPM comments intrigues me. Let's assume your 28.5 is accurate, it's what I've heard as well so I don't know why it wouldn't be, and you say it unloads 3k in the air so you want to take off at 25.5. Is 3k as much as it will unload or that's the "optimal" unload amount? In other words if I launch at 24.5 will it only make it to 27.5 in the air or will it make it to 28.5 it will just take a little longer for the extra 1k rpms? This is just my curious side coming out.
delateurj
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Re: Latest and greatest timing and deck height?

Post by delateurj »

I just started to want to take the next step in understanding Q40 engine set up so loving this thread.

Only thing I can add is some data regarding last question. Definitely possible to unload more than 3k. I have telemetry on mine and have had runs with 23.3 at launch and 28.3 peak unload in the race. Now whether that is a desirable thing or not...I am still the learning new guy.

- Joe DeLateur
telemetry.jpg
rs-ssfan
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Re: Latest and greatest timing and deck height?

Post by rs-ssfan »

Well that certainly is an interesting graph and brings up a ton more questions. It would be interesting to see something like this from all the popular set ups and prop combinations. The only problem is the human on the sticks, you'd have to get someone who's pretty darn consistent in their flying.
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