RE: REX P5 vs. OS .21 v-spec

RE: REX P5 vs. OS .21 v-spec
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RE: REX P5 vs. OS .21 v-spec - 6/22/2005 2:02:10 PM

zzman

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#6 is what i use w/20% and your manual will tell you what the carb settings are. leave the bottom alone until 8 to 10 tanks. just lean the top out to get it to run and make sure you have smoke at all times. your motor will differ from others even if its the same motor.

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RE: REX P5 vs. OS .21 v-spec - 6/22/2005 2:07:29 PM

auto2

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the deal with fuel and glow plugs is this.
a glow plug controls engine timing.( like turning the distributor and a car engine)
nitro also has an effect on timing. more nitro will cause an advance in timing. ( will ignite mixture sooner)
so if you go up in nitro you must compansate ( colder plug) or you may get detonation.( meaning the mixture ignites before the piston reaches TDC)

same with cylinder pressure. more nitro =more pressure so you need to compansate by adding more head shims to bring cyl pressure back down to prevent detonation.

note- I hope this is right as I got 60 stiches at work yesterday and am not in very good shape.....

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RE: REX P5 vs. OS .21 v-spec - 6/22/2005 2:20:49 PM

Foxy

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What are you, a stuntman?

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Post #: 78

RE: REX P5 vs. OS .21 v-spec - 6/22/2005 2:22:59 PM

vti-chris

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You are correct,BUT for someone who doesn't know much it won't help much!

When i first started in nitro buggies i had that idea in mind,but it's not much of a help.

Yes higher nitro means higher pressures and temps insite the engine(not nesessarily higher temps engine).It can keep the plug glowing easier that's why you need a colder plug,so that it won't get THAT hot(advance timing-detonation).BUT you don't want to go the other way either.A TOO cold plug will need TOO lean settings to keep it glowing cause a richer mixture cools it down.As you lean it, temps go high(engine) and engine damage will occur.

So start from a medium plug and go up by trying and see what keeps the temps low and idles well and lasts at least 1-2gallons.

I used to use the OS A5 on my hyper and temps were at 270F in order for it to work right without bogging.I changed to a medium plug and it lowered the temps to 230F and it was easier to tune!

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Post #: 79

RE: REX P5 vs. OS .21 v-spec - 6/23/2005 3:06:50 AM

breakin2

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Not to hijack the thread, but how difficult should a P5 be to turn over when it has no glow plug in it? I bought a used one and it turns over VERY easily with my fingers. I haven't ran it yet because my buggy isn't done, but I'm suspicious. He claimed there was only one gallon on it.

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Post #: 80

RE: REX P5 vs. OS .21 v-spec - 6/23/2005 3:17:19 AM

auto2

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put a few drops of oil ,spin it over a few times, reinstall the glow plug and with a flywheel on it hold the flywheel so the engine is parallel to the ground and count how long it takes to turn itself( from gravity) 90 degrees.

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RE: REX P5 vs. OS .21 v-spec - 6/23/2005 7:04:40 AM

JustinWZP

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I've never heard of that one............seems quite rediculous.

The flywheel will turn over easily with the glowplug removed on a P5. Put the glowplug on and with the engine mounted to the chassis it should be very difficult to turn over with your finger through the chassis. If you are still curious, ask your LHS if they can compression test it for you.

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RE: REX P5 vs. OS .21 v-spec - 6/23/2005 8:11:20 AM

SKYLINE350GT

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quote:

ORIGINAL: JustinWZP

I've never heard of that one............seems quite rediculous.

The flywheel will turn over easily with the glowplug removed on a P5. Put the glowplug on and with the engine mounted to the chassis it should be very difficult to turn over with your finger through the chassis. If you are still curious, ask your LHS if they can compression test it for you.

Then you are obviously a newbie or havent been in the hobby long! That is the old Paris Racing test for checking compression. Learn something before you go ahead and try to slam it.

< Message edited by SKYLINE350GT -- 6/23/2005 8:17:37 AM >

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Post #: 83

RE: REX P5 vs. OS .21 v-spec - 6/23/2005 8:24:39 AM

JustinWZP

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Didn't mean to sound negative about it. Just sounds like a rediculous way to test compression.

Not a newbie, have been in the hobby long. I guess I missed this technique over the years. Still sounds bizzare though. I'll try it out and see what I think.

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Post #: 84

RE: REX P5 vs. OS .21 v-spec - 6/23/2005 8:27:08 AM

JustinWZP

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I almost forgot...........

What did Paris Racing find to be a good amount of time for the rotation? good/bad

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RE: REX P5 vs. OS .21 v-spec - 6/23/2005 10:51:34 AM

auto2

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justin it makes perfect sence if you think about it.

how do you judge compression by twisting the flywheel? how hard are you twisting?hummm, I've been a car mechanic for 35 years . I bet I just might twist with a little more force than a 10 year kid will. so does that make my motor have less compression than his cause I'm stronger?

by using the weight of the engine and gravity you can get a more consistant "feel" for what your doing. and a more accurate way to compare to others.

my P5 with 2 gallons will sit there for a good 20 seconds before turning around.
my old Vzb will take 3 seconds and will only run for 4 minutes before shuting off from no pinch left.
my RZ that was just pinched will never turn cause of too nuch pinch and therefore is not ready to race with yet.

what you are testing is "leak down" which is a more accurate test of engine condition then compression. my leak down tester for full size cars pumps air into the cyl and measures the percentage of air excaping past the rings.

does this explaination help?

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RE: REX P5 vs. OS .21 v-spec - 6/23/2005 11:13:20 AM

Engrose

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Where should the piston be positioned when you start this test?

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RE: REX P5 vs. OS .21 v-spec - 6/23/2005 11:14:34 AM

auto2

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good question! just before the comopression stroke.

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RE: REX P5 vs. OS .21 v-spec - 6/23/2005 11:44:06 AM

Foxy

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So, auto, how did you end up getting the stitches, if you don't mind me asking?

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RE: REX P5 vs. OS .21 v-spec - 6/23/2005 11:58:46 AM

auto2

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was using excavator with grapple on it and picked up a log. log broke in the teath and sent a chunk into the windshield and my face.

hell of a way to get a few days off to work on my emaxx.LOL!

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RE: REX P5 vs. OS .21 v-spec - 6/23/2005 1:08:54 PM

Foxy

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Ouch, well, I'm glad you're ok, and enjoying your time off...

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