R/C Tech Forums - Arrow Racing GTR .21 Engine Thread

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ok just a question... When i take the glow plug out i can turn the motor over with my finger i have the extra break in shim in still so would this be time to take it out???

When it's cold and the plug is out, if you can turn the engine over and do not feel any mechanical pinch, then it's time to remove the break in shim.

Cheers
Brian

Quote:

Originally Posted by Crash Test Dumy (Post 10850041)

When it's cold and the plug is out, if you can turn the engine over and do not feel any mechanical pinch, then it's time to remove the break in shim.

Cheers
Brian

I thought so but was just making sure thanks for that

Quote:

When it's cold and the plug is out, if you can turn the engine over and do not feel any mechanical pinch, then it's time to remove the break in shim.

Cheers
Brian

:nod::nod::nod:

Unfortunately I have heard several answers to the following questions. They are not consistent. Could someone please help us find the correct answers.

1.What shims should be in the motor during break in?
2.What shims should be in the motor after break in is complete?

It would be nice if this info was included with the motor.

Quote:

Originally Posted by alvinsmith75 (Post 10854266)

The shim that comes in box with motor can be used for break in
I did not use it for breaking in mine just make sure you get motor up to temp before attempting to start for first time or first gallon or so u will also notice that motor stays really tight for around 2 gallons once loosens up all the way run times get better
good luck with it.

Quote:

Originally Posted by Rsickles (Post 10687083)

The original VZ was designed to run a 8mm and 9mm venturi. The real question you have to ask yourself, does running a smaller venturi mean you're on the gas more? Driving WOT on a smaller venturi burns more gas than learning throttle control on a larger venturi. The tuning window also closes on smaller venturis... So if you tune in the cold dewy morning, by hot and dry afternoon, you'll have to retune.

Did you install the extra .1 brass shim the engine came with? You must run one .1 brass and one .2 aluminum shim no matter what.

Here's your problem. These pipes are fuel hogs.

Quote:

Originally Posted by Crash Test Dumy (Post 10850041)

When it's cold and the plug is out, if you can turn the engine over and do not feel any mechanical pinch, then it's time to remove the break in shim.

Cheers
Brian

Quote:

Originally Posted by Mark Erce (Post 9049102)

good info...thanks!!! :nod: so when is it a good time to remove the break-in shim? and what carb restrictor were you using?

Quote:

Originally Posted by JamminSP (Post 9049125)

Once the mechanical pinch is gone is a safe time to remove the shim. Mine was never installed to begin with but at approx 1 gallon I removed the thickest of the 2 installed shim. This incresed the compression thus increasing run time and performance. I didn't see the need to install the extra shim because there isn't enough pinch to warrant it IMO. I'm also down to a 7mm restrictor but thinking of going down to a 6.5mm.

Quote:

Originally Posted by Mark Erce (Post 9056425)

ok thanks guys. I just ordered mine today. I thnk I will install the shim and then remove it after break-in. just to be on the safe side. I might have to try removing the thicker of the 2 shims as well....is alot of ppl doing this? the engine should be ok with leaving it in right?

Quote:

Originally Posted by mikenix (Post 9056858)

Adding the extra shim for break in the way to go. I got my latest one to come around much quicker so there is less fuel wasted with a motor that isn't performing as good as it should. I removed it after 1/2 gallon. I probably could have stayed as there is still massive pinch. Please start with it and you'll have a better experience. I highly recommend using heat indefinately.

Quote:

Originally Posted by Jaz240 (Post 9080341)

I've been really pleased with all the positive feedback so far. It's great to here all you guys having good outings with this motor. Special thanks to Mike Cleary for all you do for me and for Team Terribles. You made a great call bringing in these engines. I am going to be sending a couple out to Lance at RC Renew. He is going to run half a gallon of fuel through them on a break in bench with computer controlled variables and monitoring. I will then have them available for sale as ready to rip! Just remove break in shim if you want and race tune! Drop on the track ready without the added cost or time of the break in process. Prices will still be less than the original V spec or the new blue XZ ;)

Quote:

Originally Posted by akiyama77 (Post 9146722)

here's my setup

6.5mm restrictor
nova 9901 pipe w/ 41021 headder
sidewinder strike 30%
steel flywheel 2 comp w/green springs, 2 alu w/ gold springs (std losi setup)
os p3 plug
13/48 gear ratio
motor has about 1 gallon on it, and i took out the break in shim before the race
we ran a 20 min main, came in at 10 min, and took only 100cc, I used a Losi fuel gun.
Hope this helps

Quote:

Originally Posted by Mark Erce (Post 9163011)

there's a 2mm(silver) shim and 2(copper) 1mm shims. always keep the silver one and one of the copper ones in at all times. the extra copper one is for break-in. you can remove it after about a gallon.

Quote:

Originally Posted by jewn_beef (Post 10854593)

OK here is what I found. After reading all this it seems to me the best answer is to install all shims for break-in and once broken in, remove one of the small shims. I called Hobby Pro tonight but they were already closed. I will give them a shout tomorrow to hear it from the horses mouth.

install the break in shim and then take it out once the mechanical pinch is gone. usually about 1.5gal, some still had mech pinch after 2gal.

Quote:

Originally Posted by Mark Erce (Post 10858649)

install the break in shim and then take it out once the mechanical pinch is gone. usually about 1.5gal, some still had mech pinch after 2gal.

My version 2 only has one silver shim and then then the one copper shim that came in the box for break in, did they change this???

I just bought a new one and it was the same way. I have been told by two different people, (both of whom are the yodas of nitro) to install the one that came in the box in addition to the one that is already on the motor...

Tune my Arrow today,with car drive ratio of 12.20.Temp 118 c,Byron 30/11.

http://i1132.photobucket.com/albums/...1340542009.jpg

I got very very good runtime on a small track.

http://i1132.photobucket.com/albums/...1340542192.jpg

I had try drive ratio of 11.97,but the runtime are 11.30min the best.
This engine love light gear ratio!!!

How do you guys like the VP RS-4 pipe on this engine? or what other pipes would you use for buggy + truggy.. thanks for the input..

Quote:

Originally Posted by James khoo (Post 10896925)

What pipe is that?

Quote:

Originally Posted by rfleck (Post 10909958)

What pipe is that?

Orion 2058,and it got kick ass power!

Arrow-Racing GTR-21 Version 3 now available!

A-GTR-21-V3

The new Arrow-Racing GTR-21 Ver III .21 engine is now in stock at Hobby Pro USA.

The engine has been redesigned to have less mechanical pinch to make engine break in easier and allows the engine to be started the first time with less effort. This also puts less stress on the con rod and allows a race tune to be put on sooner.

He is the explaination from the manufacture:
We have done a number of minor adjustments to help with the initial start-up process for end-users. But ultimately this was done without affecting the engine's overall lifespan. The idea was brought up long ago but it was only until the beginning of the last production schedule, we were able to bring this element in. From our drawings and the actual sample, we were able to locate a slight increase of 20 microns in tolerance at 2 points of the surface between the sleeve and piston. The tightness has since been eased off by 0.1 mm with standardized insertion pressure. In the end result, the engine is easier to start and this slight increase also promote a more sufficient clearance during operational heat expansion. Thus, in general the new engine requires less time, effort and money to complete the breaking-in process.

I have not had time to break in my new one yet, but I took it apart and the piston can now be pushed up into the sleeve much farther. I compared it to a new OS XZ-B piston and sleeve and I was able to push the piston up the same distance on both engine (both new never started). So it should break in much easier now, probably half the time (.75 gallons vs 1.5 gallons).

Hobby Pro USA has sold out of Ver II engines, so all engines ordered as on today will be the new Ver III engine. :)