R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Nitro Off-Road

Reply
 
Thread Tools Search this Thread
Old 02-07-2010, 05:45 PM   #181
Tech Master
 
j_blaze14's Avatar
 
Join Date: Feb 2008
Location: Tampa, Fl
Posts: 1,693
Trader Rating: 34 (100%+)
Default

so if you don't shim the head what exactly happens that they don't last 2 gallons? the jammin's are some of the most underated motors available today. i took the head off just to locktite the screws. i sealed around the carb and backplate and locktited those screws. i did the drake/cyrul break-in and ran the motor for 2.5 gallons with 20%, sold it and now it has been running strong on 30% another gallon. the guy that bought it from me took off the backplate to check it, absolutely no play in the rod, no leaky bearings and no carb issues. which is more important, proper tuning or shimming the head? any motor not properly tuned will die early, a blanket statement that you "have to" add a shim or a motor wont last 2 gallons does not help anybody when there are so many other variables that determine engine life.
__________________
aGama A8 EVO - Werks B2 - Sidewinder
aGama A8E - TrackStar 150a, 2560kv, 3 and 4 cell
FlySky GT3B, Turnigy HV servos, SKY Lipos
AKA, Proline, Hotbodies Rubber
Elite Performance - HORRC.com
j_blaze14 is offline   Reply With Quote
Old 02-08-2010, 06:01 AM   #182
Tech Fanatic
 
Join Date: Feb 2002
Location: Greenwood, IN
Posts: 780
Trader Rating: 4 (100%+)
Send a message via Yahoo to windellmc
Default

I ran my first JPX with stock head shimming and 30% fuel until I found evidence of detonation. After that I added a shim and also added one to my second engine before break in. I am starting to think the stock plug is pretty cold. It is too bad there is no good way to measure the heat range between different brands of plugs.
__________________
MP9 tki4
Truggy?
windellmc is offline   Reply With Quote
Old 02-08-2010, 08:29 AM   #183
Tech Lord
 
Integra's Avatar
 
Join Date: Dec 2006
Posts: 12,482
Trader Rating: 8 (100%+)
Send a message via MSN to Integra
Default

Quote:
Originally Posted by windellmc View Post
I ran my first JPX with stock head shimming and 30% fuel until I found evidence of detonation. After that I added a shim and also added one to my second engine before break in. I am starting to think the stock plug is pretty cold. It is too bad there is no good way to measure the heat range between different brands of plugs.


actually there is a way to check the plugs....the diam of the hole and the thickness of the wire....its hard to tell and you need every plug in front of you to make the decipher but it Is possible to tell which plug is what if you take the time and look CLOSELY.
__________________
TNS Driver - Radio Post - Blue Groove Apparel - Team Panther - Hitec - Losi - W.E.D. Paint - Clockwork Fuel - Competition Heat - SUMO Racing - Tekin - Team Terribles - M2C Racing - Matrix Concepts - Kal Gard - BuKu Power - DE Racing -
Integra is offline   Reply With Quote
Old 02-08-2010, 08:58 AM   #184
Tech Champion
 
Maximo's Avatar
R/C Tech Elite Subscriber
 
Join Date: Jan 2005
Posts: 7,900
Trader Rating: 11 (100%+)
Default

Quote:
Originally Posted by windellmc View Post
I ran my first JPX with stock head shimming and 30% fuel until I found evidence of detonation. After that I added a shim and also added one to my second engine before break in. I am starting to think the stock plug is pretty cold. It is too bad there is no good way to measure the heat range between different brands of plugs.
you were too lean then.... even the hottest plug wont detonate on stock shimming with the proper tune.....
Maximo is offline   Reply With Quote
Old 02-08-2010, 09:51 AM   #185
Tech Master
 
RC-ZOMBIE's Avatar
 
Join Date: Mar 2009
Location: Insane Asylum, Pa
Posts: 1,353
Trader Rating: 4 (100%+)
Default

Hey Maximo, Question for ya. I have the old version JPX .21 , mine has 3 shims in it from stock and 1 extra in the box. Is it correct to have 4 shims in it to run 30%?
__________________
Associated~Tekno~Mugen
RC-ZOMBIE is offline   Reply With Quote
Old 02-08-2010, 10:45 AM   #186
Tech Champion
 
Maximo's Avatar
R/C Tech Elite Subscriber
 
Join Date: Jan 2005
Posts: 7,900
Trader Rating: 11 (100%+)
Default

Quote:
Originally Posted by RC-ZOMBIE View Post
Hey Maximo, Question for ya. I have the old version JPX .21 , mine has 3 shims in it from stock and 1 extra in the box. Is it correct to have 4 shims in it to run 30%?

no, i run these engines on 30% with only 2 shims ( 0.4mm of shims total) ...the key is when you remove the shim to make sure you richen the needles and then retune once warmed up.....As a rule removing shims will cause the tune to go slightly leaner......

However unless your running Picco plugs do not remove the thrid shim...OD and OS plugs wont like the higher compression and will not give you the same performance as the Picco plugs.....To really see what these engines can do you really need to be running genuine Picco turbo plugs...the Picco plugs are very robust and durable and will operate perfectly with the higher compression, OS and OD plugs will just cause you issues.......From my own testing OS plugs are the worst and will fail the quickest, OD are a little better but still not as good as the Picco's..... FYI I run OS and OD in many other engines with great results, however the Picco engines are unique and truly run best with Picco plugs...
Maximo is offline   Reply With Quote
Old 02-08-2010, 10:56 AM   #187
Tech Master
 
RC-ZOMBIE's Avatar
 
Join Date: Mar 2009
Location: Insane Asylum, Pa
Posts: 1,353
Trader Rating: 4 (100%+)
Default

Quote:
Originally Posted by Maximo View Post
no, i run these engines on 30% with only 2 shims ( 0.4mm of shims total) ...the key is when you remove the shim to make sure you richen the needles and then retune once warmed up.....As a rule removing shims will cause the tune to go slightly leaner......

However unless your running Picco plugs do not remove the thrid shim...OD and OS plugs wont like the higher compression and will not give you the same performance as the Picco plugs.....To really see what these engines can do you really need to be running genuine Picco turbo plugs...the Picco plugs are very robust and durable and will operate perfectly with the higher compression, OS and OD plugs will just cause you issues.......From my own testing OS plugs are the worst and will fail the quickest, OD are a little better but still not as good as the Picco's..... FYI I run OS and OD in many other engines with great results, however the Picco engines are unique and truly run best with Picco plugs...
So what is the fourth shim used for? and what Picco plug works best with 25%-30%. I am running OS P4-P3 and od 97T plugs now with 3 shims with byrons 25%
__________________
Associated~Tekno~Mugen

Last edited by RC-ZOMBIE; 02-08-2010 at 11:46 AM.
RC-ZOMBIE is offline   Reply With Quote
Old 02-09-2010, 07:49 AM   #188
Tech Fanatic
 
Join Date: Feb 2002
Location: Greenwood, IN
Posts: 780
Trader Rating: 4 (100%+)
Send a message via Yahoo to windellmc
Default

Quote:
Originally Posted by Maximo View Post
no, i run these engines on 30% with only 2 shims ( 0.4mm of shims total) ...the key is when you remove the shim to make sure you richen the needles and then retune once warmed up.....As a rule removing shims will cause the tune to go slightly leaner......

However unless your running Picco plugs do not remove the thrid shim...OD and OS plugs wont like the higher compression and will not give you the same performance as the Picco plugs.....To really see what these engines can do you really need to be running genuine Picco turbo plugs...the Picco plugs are very robust and durable and will operate perfectly with the higher compression, OS and OD plugs will just cause you issues.......From my own testing OS plugs are the worst and will fail the quickest, OD are a little better but still not as good as the Picco's..... FYI I run OS and OD in many other engines with great results, however the Picco engines are unique and truly run best with Picco plugs...
For some reason the two Picco plugs that came with my engines never made it out of break in while I am not sure I have ever killed an OD plug in the engine to the point that it would not run.

Did you try all of the OD plugs or just the 97t?
__________________
MP9 tki4
Truggy?
windellmc is offline   Reply With Quote
Old 02-09-2010, 08:08 AM   #189
Tech Champion
 
Maximo's Avatar
R/C Tech Elite Subscriber
 
Join Date: Jan 2005
Posts: 7,900
Trader Rating: 11 (100%+)
Default

Quote:
Originally Posted by windellmc View Post
For some reason the two Picco plugs that came with my engines never made it out of break in while I am not sure I have ever killed an OD plug in the engine to the point that it would not run.

Did you try all of the OD plugs or just the 97t?
You killed 2 Picco plugs and had detonation on stock shimming....I hate to say this, but honestly you must have had the engine too lean for it to do that...Not intending to pick at you or anything like that........Back when i got my first EVO 2 I did something similar as well.......... With stock shimming the compression is nowhere near high enough to cause detonation on 30% unless the mixture is too lean, killing plugs is also from being too lean as well....... With a proper tune nothing runs as nice in these engines as a genuine Picco plug, I kid you not either...I wish it wasn't true as OD plugs are cheaper and easier to find...but unfortunately they are nowhere near as good as the Picco's.... And yes I have run more then the OD 97 in them, I have modded and run many dozens of these engines over the years...
Maximo is offline   Reply With Quote
Old 02-09-2010, 08:17 AM   #190
Tech Fanatic
 
b-man777's Avatar
 
Join Date: Sep 2005
Location: MA.
Posts: 932
Default

Hey all: the new jammin jpx .21 plus engine looks realy good what i want to know is are the new plus engines still picco based as the old ones were? Thanks for the info and good luck to the jammin team in 2010
b-man777 is offline   Reply With Quote
Old 02-09-2010, 08:18 AM   #191
Tech Champion
 
Maximo's Avatar
R/C Tech Elite Subscriber
 
Join Date: Jan 2005
Posts: 7,900
Trader Rating: 11 (100%+)
Default

Quote:
Originally Posted by RC-ZOMBIE View Post
So what is the fourth shim used for? and what Picco plug works best with 25%-30%. I am running OS P4-P3 and od 97T plugs now with 3 shims with byrons 25%
The odd thing with Picco is that the shim means nothing, Picco is notorious for inconsistant shimming on their engines , sometimes they send extra shims, sometimes they don't , and they don't always send the same amount of extra shims with every engine......sometimes they have no extra shim, sometimes they have 1, sometimes they have 2 and the odd time they even have 3 extra shims......However the ideal operating compression of the engine doesn't change, and stock shimming of 0.5 mm is more then plenty enough to run 30%, i run a total of 0.4 mm total shims and I always run 30% and my engines run like a top.....If you notice any detonation or you are losing plugs you need to richen your mixture, not add more shims...


All the Picco turbo's work well...we generally run the OFNA Picco Med turbo ( P6TH)
Maximo is offline   Reply With Quote
Old 02-09-2010, 08:19 AM   #192
Tech Champion
 
Maximo's Avatar
R/C Tech Elite Subscriber
 
Join Date: Jan 2005
Posts: 7,900
Trader Rating: 11 (100%+)
Default

Quote:
Originally Posted by b-man777 View Post
Hey all: the new jammin jpx .21 plus engine looks realy good what i want to know is are the new plus engines still picco based as the old ones were? Thanks for the info and good luck to the jammin team in 2010

Yes they are Picco based, and I will have modified JPX engines ready to go for next week if anyone is interested.... they will sell for $300.00 modified with hand fitted piston...can also put together a combo with a JP4 tuned pipe, glowplugs and M2C variable weight 4 shoe clutch combo...
Maximo is offline   Reply With Quote
Old 02-09-2010, 09:02 AM   #193
Tech Master
 
RC-ZOMBIE's Avatar
 
Join Date: Mar 2009
Location: Insane Asylum, Pa
Posts: 1,353
Trader Rating: 4 (100%+)
Default

Quote:
Originally Posted by Maximo View Post
The odd thing with Picco is that the shim means nothing, Picco is notorious for inconsistant shimming on their engines , sometimes they send extra shims, sometimes they don't , and they don't always send the same amount of extra shims with every engine......sometimes they have no extra shim, sometimes they have 1, sometimes they have 2 and the odd time they even have 3 extra shims......However the ideal operating compression of the engine doesn't change, and stock shimming of 0.5 mm is more then plenty enough to run 30%, i run a total of 0.4 mm total shims and I always run 30% and my engines run like a top.....If you notice any detonation or you are losing plugs you need to richen your mixture, not add more shims...


All the Picco turbo's work well...we generally run the OFNA Picco Med turbo ( P6TH)
Can you please explain detonation and signs of it?
__________________
Associated~Tekno~Mugen
RC-ZOMBIE is offline   Reply With Quote
Old 02-09-2010, 09:11 AM   #194
Tech Master
 
Join Date: Jan 2006
Location: Virginia
Posts: 1,807
Trader Rating: 47 (100%+)
Default

I run one of Neal's(Maximos) Clocked JPX .21 engines
with .4mm of shims. This sets the pistion to headbutton
clearance at .6mm. It has had almost three gallons of
30% ran through it now and still has the original glow
plug. I just pulled the head button off to confirm how
many shims I was running and to get a squish measurement.
The top of the piston and head button show no carbon
buildup and the glowplug reading looks great. This engine
was broke-in properly and the rod was replaced. The rod
really didn't need replacement but I did it anyways to be
safe.
Anyone thats only getting two gallons out of these engines
had better learn how to break an engine in properly or pay
someone that offers engine service to do it for them.
As far as anyone blowing the Picco glowplugs one after
the other, LEARN TO TUNE, your running your engines
way to lean. My JPX likes to run a little fat on the top
end.
Neal knows that I run the hell out of my engines and
he sure made my JPX one screamin engine.
rageworks is offline   Reply With Quote
Old 02-09-2010, 11:39 AM   #195
Tech Fanatic
 
Join Date: Feb 2002
Location: Greenwood, IN
Posts: 780
Trader Rating: 4 (100%+)
Send a message via Yahoo to windellmc
Default

I do not think you understand. I had detonation with a non Picco (either OS or OD) plug. The stock Picco plug lasted through a heat cycle break in and never made it to a track before it died. On my 2nd engine the stock plug lasted until my first tank on the track (which means it never even went full speed on the straight). Forgive me if I do not want to spend $15 per plug to see if my luck changes. Did you try the OD 99T? I have ran the 97T and 77T and the 97T works great for me in cold weather. It does not seem as good in warm weather which makes me suspect the plug is too hot.

The time I had detonation the engine ran the best it ever did so it may have been lean but it seemed to be tuned about perfect. I saw no change in power or fuel mileage with the extra head shim.
__________________
MP9 tki4
Truggy?
windellmc is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
What a Good 21 to get? Kausekaos Nitro Off-Road 22 08-28-2009 02:04 AM
Jammin JPX .21 heeltoedrver Nitro Off-Road 165 08-25-2009 01:02 PM
v-spec vs jpx.21 engine comparison Bulldawg RC Nitro Off-Road 36 04-23-2009 09:16 AM
*Beautiful Xray XB8* Karter01 R/C Items: For Sale/Trade 70 12-14-2008 03:55 PM
What is the best .21 buggy engine chris1381 Nitro Off-Road 30 10-28-2008 05:38 AM
Looking for a new .21 engine for offroad buggy. supralative Nitro Off-Road 54 07-31-2008 02:06 AM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 10:53 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net