OFNA GTP LRP.32 ENGINE SHUTS SHIFTING GEARS

[Manolo762]

Hello , I have posted before on other topics, Inreacentlly purchased a OFNA GTP2 nitro and upgraded it with a 4 shue clutch, hitec hi torque titanium gear coreless servos from a 700 heli swash plate, an LRP.32 engine and changed the spur gear and clutch bell pinions. Since the Lrp engine generates a tremendous torque and has a not so hi max rpm (around 33,500 max accirding to lrp) the top speed was around 60mph, I was having problems with the car on departure since the tires would slip because of the engine torque . I decided to change the spur and cluthc bell gears to increase top speed, the original gear setup was
Clutch/spur
14/49 1st gear
18/45 2nd gear

I changed it to
Clutch/spur
16/49 1st
21/44 2nd

It has done some effect while departing and kills some torque out of the hole, but now, when shifting to 2nd gear the engine dies, I have tried getting to speed little by little to the shifting point so that the engine is reving hi rpm but still shuts off. It makes a particular sound like a slow motion cassette playing on a walkman, the engine was was broken in and has runed about a bit more than half a gallon. The local hobby shop told me that could be the engine running too lean at top speed but I dont really know, I asked him if the gear teeth reduction was too agressive and the engine couldnt handle it, but he said if that was the case the car would just run slower until the engine could acelerate and keep up. Any help would be greatlly apreciated since I am kind of new to thes! Thank you!

 

[olds97_lss]

It's probably lean on the high side. Your working with speeds that cool things off pretty fast, and now it's faster. I'd richen it up a decent amount, then lean it as you see fit. It's usually easier to sort things out when going from rich -> lean vs lean -> correct. If it's too lean, you get a lot of false responses because it could be just starving for fuel, or too hot and flash burning on you. But since your running at such a high vehicle speed, it cools too much for you to tell what's really going on.

It's surprising how quickly these engines drop temp 20-40 degrees.

 

[Manolo762]

It's probably lean on the high side. Your working with speeds that cool things off pretty fast, and now it's faster. I'd richen it up a decent amount, then lean it as you see fit. It's usually easier to sort things out when going from rich -> lean vs lean -> correct. If it's too lean, you get a lot of false responses because it could be just starving for fuel, or too hot and flash burning on you. But since your running at such a high vehicle speed, it cools too much for you to tell what's really going on.

It's surprising how quickly these engines drop temp 20-40 degrees.[/QUOTE


I will try to work it out, what I am really worried is that the gears relation might be too agressive and simply wont work, man that engine is overkill for almost any vehicle, and I am running 20% nitro havent tried 30, but has slow rpms compared to other engines, I just recived a ofna hyper mach .28 engine with 6 ports that says it revs up to 38,500 that is 5,000 rpm more, I order it for a ofna hyper 7 bugy but I think that I would experiment on the gtp if I can't solve that issue

 

[olds97_lss]

If the engine pulls up through first and shifts without laboring really bad, then it's probably fine, just needs more fuel to do it's job. A 2 tooth jump doesn't seem that much. Unless it was already really tall gearing.

I have an LRP28 in my savage and for the longest time, I couldn't gear tall because the slipper would melt down. So, I ran with 15/49 gearing as even just 15/47 would cause the slipper to melt when it shifted into second gear. The engine had the power to pull it, but the slipper would slip, then glaze, then melt. All within about a tank of fuel.

Then I got a steel spur and went from 15/49 to 17/47 and it still wheelied hard in first. I changed to 18/47 and haven't run it since. Guessing it will do fine.

I know your rig is totally different, but +2 just doesn't sound like your issue would be the engine not having the power to deal with it. If it was taking off the line sluggishly or then shifting and bogging on you, then it would make sense. But stalling when it's pretty high in the RPM range just sounds to me more like it's starving for fuel.

 

[ninnon]

As olds said, changing things like this means a change of tune. Nitro Engines can be very sensitive.