JohnP2

Hi all,

I've heard that it can be damaging to a nitro engine to keep it at WOT too long? While this makes sense, I'm curious as to what that is?

30 seconds? 10 seconds? Two minutes?

Just curious as to what the threshold might be (assuming there even is one) to where you can begin hurting your engine. I'm sure every make is different, but would like to know your thoughts.

Thanks!

nitroexpress

Depends on the brand and size of the engine, whether the engine was designed for onroad or offroad, type of fuel, and tune. There is no set time except that set by common sense.

proanti1

My Feedback: (2)

Really depends on how lean the engine is, and like previously said, it's size and application. I don't like going WOT, I cringe every time I hear someone run their car full throttle back and forth across a parking lot. I like to keep my speed runs below 5 seconds. These little engines are fragile.

controlliner

Like proanti1 says, it depends on how lean the HSN is set at WOT. I've run my T-Maxx down a football field and back at WOT and the engine was only mildly hot. This engine has no pinch left and I run airplane fuel in it with xtra castor oil 5-10% nitromethane. I've never broken a rod on my Traxxas 2.5, it's the original rod and no large play in the top or bottom end.

JohnP2

Thanks, guys. This helped. Unfortunately, I do have a "led finger" and like to open it up, and as you all mentioned - common sense (meaning knowing what to look for, listen to, and see) seems to be the best method.

hunternaf

I have a duratrax RT-X27 with a HPI 4.6 in it running Odonnel 20% speed blend, When the new outdoor oval (Joe Dirts) opened last year they let everything run the first day, I had to blip off the throttle and immediately go back to full throttle as fast as I could in the center of the corner once at each end of the track, that day I ran 3 4min heats and a main with no noticeable damage to the engine, still running fine after a couple of gallons but that is the only wide open throttle I have done for long periods of time mostly typicle bashing stuff

nitroexpress

Maybe I'm stating the obvious, but there is a difference between WOT and running flat out at max RPM's

It's the max RPM's for extended periods that hasthe most potential for damage. A well broken in engine will not be damaged by WOT, say from a stop or out of a corner.

downunder

While there's no direct comparison, in some types of control line model planes they use engines designed to run in the 30-35,000 rev mark continuously with no throttle. Depending on the type of contest this means running for 4 minutes or more then landing, refuelling and back into the air again. All at flat out peak revs. This doesn't do any harm to the engines. However, their peak revs are limited by the continuous load from the propellor keeping them at peak HP but below what would be a self destruct rev. The limiting load on a car engine though is usually much less which allows for overspeeding into the self destruct area. Higher gearing is one way to keep the overspeed revs down into a safe area.

I might add that the plane engines use more oil (about 20%) in the fuel than car engines so if you were to try running a car engine flat out all the time I'd suggest adding oil to the usual car fuel.

1QwkSport2.5r

+1.

Running the engine at a completely peaked needle setting is not good to run at for long periods of time. Its usually best to find the "perfect tune" and back it off a little richer. I always give it 1/8th turn richer from the peak setting. It doesnt hurt to run the low speed just a touch richer too. If your temping out over 300°F, richen the main needle another 1/8th turn or so.

purenitro33

They do it with boat engines all the time, WOT at red line, as long as the tune is good they should be able to handle it no problem.

proanti1

My Feedback: (2)

Boat engines are a completely different breed. There is a constant load on the engine, they're water cooled, and the oil content is very high (like with plane engines). They're ported in a way that keeps them from self destructing, car engines are pretty much left with enough top end to allow them WAY past an acceptable redline.

purenitro33

They are the same as most car engines... I just worked on a nova rossi Flash (car engine) that simply had a marine head, the timing was almost exactly the same as other land based engines. Other "marine engines" are nothing more then a car engine with a water cooled head. They are much closer to the same then one might think without seeing first hand.

1QwkSport2.5r

I agree with this, and I'll partly agree with Proanti1. The oil content of the fuel is lower in cars than planes or boats because of the loads on the engine, and performance. Car engines, even with heavy flywheels, aren't loaded enough to need the extra oil, and the way they're built (double bushed conrods for example) plus it knocks top rpm down a little. Boats and Planes can run WOT all day long at peak or near peak rpm because of the 20%+ oil content. Nitro Helis are the same way, except most guys use full synthetic oil in those.

Boat engines are water cooled because they run ridiculous amounts of nitro, and probably turn faster rpm than the car counterparts because of the extra nitro.

From what I know, some marine engines can have some pretty gnarly exhaust timing.. Getting up to 180° ex. timing almost requires a full wave pipe to run right..

proanti1

My Feedback: (2)

Are you talking about the TOP Plus 21 Flash? The only thing it shares with the Nova Flash car engines is the crank case. The crank, sleeve, carburetor, and head button is marine specific. Someone may have put a marine head on a Nova Flash, but that does not make it a marine engines...

Off the top of my head, the only marine engines that are truly just car engines with marine heads are either RTR, or the OS 15CV-RM, or some older K&B engines. Take a look and OPS, those are very specific to marine, and timed to run with marine tuned pipes.

1QwkSport2.5r

OPS makes high end Airplane engines also. Not quite as powerful as a Nelson or Jett, but they're strong runners. I have no idea how the Aero is timed vs. the Marine though. I would imagine a marine sleeve would be different than a car sleeve, only because of the port size and timing being different. The timing at the very least would have to be different because the load on the engine will be very different. The crank would be different too because of its induction port timing, but the overall size of the crank may be the same.

purenitro33

Are you sure about that? all the #'s match except for the head and carb.

http://www.novarossi.it/files/explod...ASH%2021-M.pdf

http://www.novarossi.it/files/explod...%20SPECIAL.pdf

proanti1

My Feedback: (2)

Ok, didn't realize that about the Nova. Guess I was thinking about something else.

8MILLSNIPER007

Actually the car/buggy engines are very simular to marine engines and as long as your car/buggy/truck is leaving a nice trail of smoke out the pipe while you are running wide open it is getting lubricated and will be just fine but you should know that as long as the throttle is "WOT" the engine temp will increase- how much depends on way too many different factors to list here. A marine engine does have the advantage of fresh cool water to help control the heat soak where a land driven engine does not.  The best thing to do if you like to run WOT is start of with a at temp engine and make a pass no more than 3-5 secs. long and check your engine temp.  Now make another pass only a little bit longer and check your temp. Keep doing this and you will learn what you can and cant do with your engine.  By the way for most nitro engines 300 degrees is kinda hot, I do know the traxxas engines love to run hot, but most other engines will be much happier below 270-280.  Most ABC (pinch) engines dont even get a good piston sleeve seal until 200-225 degrees and running them below operating temp will wear out a piston and sleeve really fast... Best of luck to ya!

asmund

I run a Sirio .27 Race byggy engine in my Boat (Thunder Cat 31) I`m also running 60% nitro and most of the running is at WOT all the time. I have not been able to blow my engine yet[:-]¨
It is copletely stock, aircooled and everything

8MILLSNIPER007

Alot of nitro powered boats that are watercooled are actually running too cold, look at the K&B outboards the hi performance models are air cooled and only have two or three cooling fins. The aluminum lower unit is a big heat sink. Alot of guys are going to air cooled buggy/ car engines in their boats for many reasons, some are pretty obvious but as long as you can get airflow to it they work well. Another benefit is the air right above the water surface is usally nice and cool. How does that Siro run in your boat?

The_Shark

7 seconds is about all I will do to my engines, its not good for them so I avoid it, I also avoid constant "blipping" that just wears clutches too fast.

8MILLSNIPER007

Shark, If your tune is right the engine will handle WOT... Long before our car engines came to what they are today they use to run (ans some guys still do) boats, planes and even cars on thethers in a big circle. These engines had no carb, just a venturi. As soon as you got them fired up they would set the needle for max rpm's and let them go. These engines would run anywhere from 4-10 mins at a time at max rpms and the engines lasted for years without rebuilding. Nowdays our alloys are lighter, stronger and better designed so as long as your hsn is set to where you are getting smoke out the exhaust at wot and you keep an eye on your temps your mill will handle it. I use to race on road oval and if the track and your car were setup right you could run the whole race wide open throttle. We had many enduro races that were 45-60 mins long non stop, only reason to back off the throttle was if someone got in your way or you had to pit for fuel. These engines survived many of these enduro races and went on to consume several more galons of fuel. I think I would change the bearings after a couple of enduro races, and a piston/sleeve when needed (not very often- 4-5 gallons of fuel, sometimes more)

The_Shark

eh, I still feel better running WOT for short bursts, I know the engine in my MGT 8.0 is just a helicopter engine, and these run WOT the whole time, but with almost twice the oil car and truck fuel has, its happy running WOT for long periods of time, and I allow that since the engine is so robust and spins relatively slow compared to a normal car engine, as do most aircraft engines.

to get peak performance, you have to run a bit lean, pushing the engine's limits at WOT, running rich allows WOT, but reduces throttle feel and response, something you want for offroad buggies and trucks.

all I know is the noobies that can't properly tune, blow their engines from WOT runs.

8MILLSNIPER007

Shark,
If that is what you feel comfortable doing then great! I do have to disagree with you about having to run "a bit lean to get good throttle response". Just about every engine I've had was able to maintain a wot and still have great low and mid response with a race blend fuel which usally has less oil then normal fuel.

The_Shark

oh, I can make a engine sing and still stay cool and get great fuel economy, BUT a race quality tune is leaner than a "bashing" tune and for most people, they want to go fast as possible and tune the engine to or beyond a race quality tune and blow it up. I always tune in the middle of the road, peak performance without pushing it, and a good flow of smoke and oil (and good powerband)

I have never worn out a engine in the 13 years ive run nitro, I always tune a tiny bit rich and avoid extended periods of WOT runs

but your right, if the engine is healthy and the tune is good, WOT shouldn't hurt an engine, but I have seen people blow out engines running in a field for a few seconds, so, I don't recommend OTHER people doing it.