Frequent WOT runs are good for an engine?

[gtm245]

Here is something interesting I just read over on another forum by a well respected member and was wondering what you guys thought-

quote:

---

There are many advantages to occasional full throttle accelerations with a Northstar and any engine.

It keeps the carbon cleaned out of the combustion chamber. This is maybe a little more important with the Northstar than some other engines due to the tight squish volumes between the piston and the cylinder head. It's designed this way to promote good in-cylinder mixture motion (good combustion) but it has the down side of providing a ready place for carbon build-up to touch the piston - causing noise. Ever heard of the Northstar "cold carbon rap" problem?? Simply put you'll hear a rythmic, piston slap-like noise when the engine is cold. Very prominent and very annoying. Cause: excessive carbon build up causing the the piston to contact the carbon on the head - causing it to rock in the bore and "slap" Much more evident when the engine is cold and the pistons haven't expanded to full diameter yet. Simplest and easiest "fix" for this: A few good WOT (wide open throttle) accelerations to clear the carbon out. That is all it takes to eliminate the problem and prevent it from re-occurring.

Occasional WOT accelerations also help seat the rings to the ring lands and exercise the rings and keep them mobile and from becoming stuck in carbon in the ring lands. At high RPM and WOT the rings move around on the piston - they actually rotate on the piston and will polish away any carbon and seat themselves to the sides of the ring grooves. This is especially important on the 2000 and later Northstars which had hard anodized top ring lands on the pistons. Very hard and wear resistant - also harder to break-in and seat the rings to the sides of the ring-lands to promote the best possible seal. Many oil consumption complaints on the 2000 and later engines are related, to some extent, with the rings never seating to the sides of the ring-grooves due to lack of load as the engine was babied around forever. Even engines with rings stuck in the ring-grooves due to carbon build up can eventually be freed up with enough high RPM operation.

WOTs warm up the engine thoroughly and clean out the exhaust due to temperature in the exhaust and high flow rates blasting particles, rust and such out of the system.

Frequent WOT operation will not hurt the engine or the transmission. They're designed for that. The healthiest engines that I have seen at high miles are always the ones that are run the hardest. Rings are free on the pistons and sealing; no carbon buildup.

The exercise that I think works best for many things is to select manual 2nd gear on an isolated stretch of expressway. This takes the transmission shifting out of the question if you are worried about hurting it. Start at 55 MPH or so and go to WOT in 2nd gear and hold it until the RPM reaches near the normal shift point - i.e. 6500 for an L37 and 6000 for an LD8. Hold the throttle wide open until the engine reaches, say, 6200 for an STS and then just let completely off the throttle. Leave the transmission in 2nd so that the engine brakes the car and creates some pretty heavy over-run conditions at high vacuum levels. Let it slow until it is about 55 or so and then go to WOT again and repeat. This exercise really loads the rings, allows variable RPM operation at WOT for several seconds continuously, creates heavy over-run which tends to unload the rings and make them move and thus exercise them in the ring grooves and it will blow-out carbon and the exhaust - all without creating a spectical of yourself and attracting the attention of cops. You can do it on most any freeway and stay within the 70-75 MPH range allowable. Once a week like this will keep the engine cleaned out and healthy and is DEFINITELY recommended for the Northstar in particular.

The Northstar engine was designed/developed/validated to be run hard. It was expected that people would use the performance of the engine - which few people seem to do. The biggest single problem that many issues stem from is lack of use at full throttle by the owners. It just doesn't like to be babied around. The rings are low-tension by design for good high RPM operating characteristics and low friction/good power. They work best if "used" and kept free.

In every conversation with owners I have had, once the owner started doing the WOTs and using the power of the engine they report no more carbon rap, better oil economy, no "smoke" when they do light it up (keep the exhaust cleaned out. If you notice a "cloud" at WOT then you are not doing enough WOTs...) etc... A bit of judicious use of the other end of the throttle travel is a GOOD thing...

---

Is this a good idea, will it help maintain a cleaner engine, promote less oil consumption, ect...?

So is it good to do WOT blasts down the highway and what could it harm?

[ December 14, 2004, 10:42 PM: Message edited by: gtm245 ]

 

[XS650]

Looks like it takes a long set of instructions for a Cadillac driver to be able to use full throttle for few seconds.

 

[55Test]

Would this procedure be advisable on higher mileage engines? Perhaps I should give the Altima a few runs at WOT in 3rd gear up to something like 78 mph, which is about 5000 rpm's then slow to 50, a hair under 3000, and repeat. Think it'll do any good?

 

[JHZR2]

seems to me that young kids that like to drive their cars hard tend to ruin them. Maybe its because theyre notknowledgable enoughto maintain their stuff properly, I dont know. But typical logic would say that if it could take it OK, they wouldnt run so poorly, smoke, etc.

I think doing it, once in a while, to a certain extent, not too severe in the RPM range, etc. may do some good in burning junk off. But I wouldnt redline it and I wouldnt do it too often.

JMH

 

[jthorner]

Occassional WOT runs are sometimes factory suggested "service procedures" for certain problems. Volvo has a TSB somewhere on my 850 which suggest a sequence of WOT runs to clear carbon build up from the valves.

Constant hard driving, on the other hand, is not something which is going to IMO extend the life of an engine ... or more importantly the transmission.

It is kind of funny how much focus is on engine maintenance and life when so many vehicles now have automatic transmissions which cost many thousands of dollars to replace. I would even venture to guess that in modern vehicles transmission failure is a more common high $$$ repair than is the need for an engine replacement.

John

 

[Terry]

Periodic WOT romps are normal procedure for our family cars and all drivers here are well versed in the procedure !

Why own a wonderful, well maintained car whether a 3 cylinder GEO or C6 Vette ,and never givEr all shes got ?

 

[MONKEYMAN]

I have known two people who had a Cadillac. One was my 85 year old neighbor, and another was an 85 year old retired doctor I worked for. I doubt there cars were ever opened up throttle wise.

The last year I have been driving my Sentra WOT several times when going to my parents 75 miles away. It is an auto, but revs pretty good when you floor it. I could tell it was running better doing the WOT thing. Now that I am using Fuel Power and Auto-RX the car will have a nice discharge when I floor it. It is running better at 170,000 miles than it did when I bought it 100,000 miles ago. I think there is some truth to what this person says.

 

[55Test]

quote:

---

Originally posted by jthorner:

Constant hard driving, on the other hand, is not something which is going to IMO extend the life of an engine ... or more importantly the transmission.

---

Depends on how you define hard driving. 80-90 mph on a highway when traffic permits in my mind is not abusive, but stoplight dragracing around town to me is.

 

[XS650]

quote:

---

Originally posted by 55:
Would this procedure be advisable on higher mileage engines? Perhaps I should give the Altima a few runs at WOT in 3rd gear up to something like 78 mph, which is about 5000 rpm's then slow to 50, a hair under 3000, and repeat. Think it'll do any good?

---

You don't need to do anything special, just stick you foot to the floor and wind out close to redline a couple times week.

 

[XS650]

quote:

---

Originally posted by Terry:

Why own a wonderful, well maintained car whether a 3 cylinder GEO or C6 Vette ,and never givEr all shes got ?

---

Driving a low powered car hard is like wearing a dark suit and wetting your pants. It gives you a nice warm feeling and no one notices

You can have more fun with a low powered good handling car on a twisty road than with a high powered car.

 

[gtm245]

In my opinion I don't think it will do any harm at all. Please read the entire discussion from where I got this quote. It's 3 pages long. (I know I'm sorry

)Here is the link-

http://www.cadillacforums.com/forums/showthread.php?t=226

I think the guy I quoted is pretty reputable over on that site and at least it makes a very good read.

 

[sub_zero]

I couldn't agree more!! WOT was part of the design when the thing was built. Like all machines they were designed to RUN.

 

[gtm245]

I wonder how well doing WOT runs would stop oil consumption problems, clean out some carbon, ect...

 

[JohnnyO]

Funny, I was thinking of the Caddy N* before I even opened the thread. On the Caddy boards they will tell you that the rings carbon up and stick, thus giving you mucho oil consumption like my mother's car. WOT helps but you should put it in 2nd gear, floor it from 55 to 80 mph, then abruptly let off the gas and coast back to 55 mph. Repeat about 5 more times. The vacuum created by the compression braking will loosen up the rings. Problem is that most Caddys are like my mother's, spending most of their time creeping to Wal-Mart at a speed barely above idle.

 

[drm7]

Back in 85 my mom drove a 76 Ford LTD with a 351 2bbl. She putted around town in it mostly. Probably 5-10 miles in a day. On weekends back from college my brother and I would run the crap out of it. By Sunday afternoon it idled smoother and seemed like it had more power. Same went for my dad's 80 Chevette.

 

[buster]

Is their any science behind the idea that WOT is healthy for the engine? I hear this all the time, and believe it, but I'm not sure why exactly it helps. I always thought of it as person that excercises vs someone who just sits around.

 

[gtm245]

Well read the discussion in this link - http://www.cadillacforums.com/forums/showthread.php?t=226

They shoot the topic back and forth. Some agree it does benefit the engine to do this some don't. I think it does have a positive effect on removing carbon deposits though. Plus I bet you could do this kinda thing all you wanted to and not hurt the engine one bit. I mean look at the testing the Northstar has gone through-

quote:

---

All the engine durability testing takes place on an engine dyno. As an example, the Northstar engine is validated on a test on an engine dyno where the engine is run at full throttle, 6000 RPM, making 300 HP for 300 hours continously. The engine is shut down occasionally for checks and oil changes and such but when it is running it it full throttle at 6000 flat out. And it lasts 300 hours. In 300 hours at 6000 RPM in a car that would be about 150 miles an hour and the car could go 50,000 miles....twice around the world.

---

quote:

---

There are a LOT of engines designed to run continously at WOT... Every engine is designed with a certain duty cycle in mind. Engines that power heavy trucks run wide open at peak power all the time. They are designed to do that and can do it for thousands of hours. Dedicated marine engines are designed for a "rated" power and can run that way for thousands of hours. Even simple engines like a 5 HP Briggs and Stratton on a portable generator runs wide open all the time as long as the generator is loaded. It is designed to run that way.

A diesel engine in a commercial 18 wheeler can run at WOT maximum power for millions of miles. It was designed for that kind of constant power output. It runs at a relatively low RPM (below 1800 RPM all the time) to keep the inertia loads low and makes the power/torque with compression , displacement and a lot of turbo boost...and very very robust internal parts...allowed due to the low RPM it operates at.

A passenger car engine is at the other end of the spectrum. It will idle thru life almost never running at full throttle. It will last hundreds of thousands of miles running at part load. It is designed to make a lot more power to accelerate and pull loads on an intermittant basis. Generally , an automotive engine will live at full load, full throttle for several hundred hours...not the thousands and thousands of hours that a marine or truck or aircraft engine might see under these conditions. It all depends on the duty cycle of the engine and what it was designed for.

You run your weed eater engine or leaf blower engine at WOT for extended periods....those were made for that. They are relatively low specific output engines for that very purpose...to live at a continous WOT duty cycle.

Many engines are rated at different power levels based on the duty cycle that they must endure. Gas truck engines are commonly rated at a number like 350 HP in a light duty truck (an 8.1 GM gas engine in a suburban or pickup) or that same exact engine (same internal parts) would be rated at 280 HP in a heavy duty truck that would tow 16000 pounds all the time ... or haul rocks out of the quarry in low gear and full throttle all the time. That same engine might be rated at 220 in a Kodiack truck that tows semi trailers short distances...but at full throttle all the time to keep them rolling. The engine is derated to be able to perform at it's rated power (WOT for that application) for thousands of hours that would be required...instead of the hundreds of hours that it might see at WOT in the light duty pickup truck. The key to understanding is that there are many different duty cycles and each engine is designed, optimized and rated for that application. Many of the heavy duty engines spend all their lives at full throttle both gas and diesel varieties.

---

He says that an automobile engine will live at full load, full throttle for several hundred hours. If thats true there is no amount of abuse the average motorist could do on a public highway to blow up their engine. Especially only 10-15 WOT runs to clean it out.

 

[k1xv]

For years this kind of remedial driving was known as "an Italian tune up". We also called it "blowing out the carbon".

In the old days, it was easier to blow up an engine because of improper carb jetting and the potential to over rev the engine. Today, with EFI, greater use of automatic transmissions and rev limiters, it should be safer.

I still get the old Infiniti Q45 up over 6000 rpm now and then (the tach red line is 6900 rpm) and at 150K miles, its still going strong.

However, if you are going to do this, I would recommend that you know your cam drive belts and other such things are in good shape. Busting or throwing a cam belt on an interference fit engine can spoil your whole day.

 

[Bryanccfshr]

My grandfather tought me to do this from an early age as a Porsche/VW mechanic he would service alott of his long time sutomers vehicles on the side(more for him less for the customer).

He would often run these vehicles hard right after a tune up or servicing and the customer would always comment how much better the vehicle ran. This was in the time before the ECU and Fuel injection so I believe in the carbon blowing ring freeing effect of running an engine hard occassionally and do it myself from time to time.

It is hard to hurt an engine with the rev limiters of today, besides if done with a little common sense and with safety in mind it is fun to open a vehicle up.