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Old 03-18-2009, 02:11 PM   #1
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Default GRP ENGINE HELP

can someone help me out,

i have a .21 tuned grp. it had prob around 2 gallons of fuel on it. i took the engine to the nitro challenge out here in az and since then ive had problems. its runnin rich but yet the temps are at 210-220.

it seems like im just chasing the tune. i was thinking an air leak but my idles not irratic and it doesnt seem run like an air leak. ive set it back to factory and tried retuning it but with no success
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Old 03-18-2009, 02:14 PM   #2
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I would still check for an air leak. If you already set it back to factory and started over it could definately be an air leak.
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Old 03-18-2009, 02:16 PM   #3
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how do u "TEST" for an air leak
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Old 03-18-2009, 02:38 PM   #4
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Originally Posted by losi_racer View Post
how do u "TEST" for an air leak
One way to do it to spray nitro spray around the engine in places that it could be leaking. You do this while the engine is running and if you notice a change in RPM at all you know you have found the leak. I'm not totally sure that an air leak is your problem, but it is worth a try.
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Old 03-18-2009, 02:44 PM   #5
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One way to do it to spray nitro spray around the engine in places that it could be leaking. You do this while the engine is running and if you notice a change in RPM at all you know you have found the leak. I'm not totally sure that an air leak is your problem, but it is worth a try.
i just reset it again at factory and retuned it, i got a nice tune but my temps are still high its at 225 when i pulled it off. this is high speeds runs at well with the temp outside about 90
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Old 03-18-2009, 03:22 PM   #6
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i just reset it again at factory and retuned it, i got a nice tune but my temps are still high its at 225 when i pulled it off. this is high speeds runs at well with the temp outside about 90
That really is NOT hot. 225 is a normal running temp for a .21 especially with it being 90 outside and after high speed runs. That is probably the perfect temp. If it is running good leave it and run the hell out of it!

Edit: Tuning strictly by temp will get you into trouble. You want to watch for smoke and listen to the engine as well. If you are getting a good trail of smoke, it sounds as it should, it is making power and is under 250f you got a perfect tune.
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Old 03-18-2009, 03:39 PM   #7
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That really is NOT hot. 225 is a normal running temp for a .21 especially with it being 90 outside and after high speed runs. That is probably the perfect temp. If it is running good leave it and run the hell out of it!

Edit: Tuning strictly by temp will get you into trouble. You want to watch for smoke and listen to the engine as well. If you are getting a good trail of smoke, it sounds as it should, it is making power and is under 250f you got a perfect tune.
but grps are supposed to run 160-200... i dont tune by temp i do it by how it sounds and smoke, i temp it AFTER i finish tuning it. i have a race tonight so hopefully it goes well
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Old 03-18-2009, 03:52 PM   #8
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If you are still having problems with it after tonight bring it with you to the pit and I will tune it for you.
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Old 03-18-2009, 04:19 PM   #9
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losi racer, does it seem to start running rich while the engine is transfering from bottom to midrange. I had a problem with my GRP.21 TUNED. Would sit and idle no problem bottom end was good and top end would scream. But at about 10 mph if I had it cracked wide open it would start to go rich. Like you I tune by sound and feel and then verify temp with a gun. Temps would be at 220-225. I found the problem with mine was the pinch bolt on the carb had come loose enough to cause an air leak.

HOPE THIS HELPS
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Old 03-18-2009, 04:52 PM   #10
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but grps are supposed to run 160-200... i dont tune by temp i do it by how it sounds and smoke, i temp it AFTER i finish tuning it. i have a race tonight so hopefully it goes well
Uh NO. Any .21 engine should run between 200-230. Running an engine cooler than that will kill it just as fast as running it too hot. Every engine needs to heat up to the point where the parts have correct tolerences. You have to get it to the temp where metal pinch is gone. If you run it cooler than that point you could damage the rod, piston or sleeve. GRP's arent any different than any other engine. 225 is a perfectly normal temprature for that engine especially at 90 outside temp.
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Old 03-18-2009, 04:52 PM   #11
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I had 3 grp tuned engines never got more than 1.75 gallons through any of them ...constantly chasing tune front seals leaking on all 3. Done w/ GRP.I have also had other racers attempt to tune with no success. i know that they are excellent engines ,they just are not for me, No offense to any GRP fans.I really had hoped to get one that would run also absolutely no help from HORIZON with any GRP. pretty much said I ran the engine lean and overheated it. Yeah I bet the leaky front seal had nothing to do with it.
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Old 03-18-2009, 05:08 PM   #12
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1- If the piston and sleeve are still pinching then your still not past the breakin in process so that heat build up is from the pinching.

2- What fuel are you using check the content and make sure your shimming is correct. Out of the box it's for 20% to 30% you can remove one shim if you one not more then 0.1

3- Check for fuel line leakages you might be lean cause of that.

4- Check the engine / manifold rubbers grommets and the pipe side as well a small leak there could make a world of difference.

5- Pressure test your fuel tank and check the fuel filter for any debris.

Other then that if you still facing issues an engine tear down would be precautionary step for your to see if there is any abnormal wear.
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Old 03-18-2009, 06:14 PM   #13
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What plug are you running. It may too hot of a plug.
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Old 03-18-2009, 06:16 PM   #14
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I have had 3 GRP .21's 1 stock tuned, 1 modded tuned and 1 modded non-tuned. They all run at about 225. My first GRP .21 tuned ran at 225 for 7 gal until I sold it. It still had plenty of power and ran great. If I lean them out they get up to 240 but this is too lean power suffers and no smoke. A friend of mine says his .21 tuned runs all day long at 165. The other variable is the temp gun. I have had an expensive temp gun read 30 degrees cold and cheap temp guns read within 5 degrees. Test the temp gun with 50% ice and 50% water and see what it reads. Bottom line the temp doesn't matter as long as you tune to performance and smoke you can never go wrong. I have been told by my engine moder to nod and smile to the guys that say 225 is too hot for a GRP. Good power with crisp acceleration and good smoke out of the pipe at all speeds is all you need. Besides every engine is different. All 3 of the GRP's that I have owned have needed different needle settings by as much as a full turn, theres just too many variables. Performance and pipe smoke
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Old 03-18-2009, 06:20 PM   #15
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Quote:
Originally Posted by Frank L View Post
I have had 3 GRP .21's 1 stock tuned, 1 modded tuned and 1 modded non-tuned. They all run at about 225. My first GRP .21 tuned ran at 225 for 7 gal until I sold it. It still had plenty of power and ran great. If I lean them out they get up to 240 but this is too lean power suffers and no smoke. A friend of mine says his .21 tuned runs all day long at 165. The other variable is the temp gun. I have had an expensive temp gun read 30 degrees cold and cheap temp guns read within 5 degrees. Test the temp gun with 50% ice and 50% water and see what it reads. Bottom line the temp doesn't matter as long as you tune to performance and smoke you can never go wrong. I have been told by my engine moder to nod and smile to the guys that say 225 is too hot for a GRP. Good power with crisp acceleration and good smoke out of the pipe at all speeds is all you need. Besides every engine is different. All 3 of the GRP's that I have owned have needed different needle settings by as much as a full turn, theres just too many variables. Performance and pipe smoke
+1. you can also test your gun with a boiling pot of water. Just right when it boils, not a heavy boil. It should read 212 deg F or 100 deg C.
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