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WOT's


Bob_Caddy

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I have heard that doing WOT's is actully not bad for your car? Is this true, because from the second I step on it, it sound awsome, but it also seems like it is hard on the vehicle? I like doing WOT's but I dont want to be hard on my car doing them! What do you guys think? Thanks.

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Here is a quote from out resident expert. If you are unfamiliar with him, he is a GM powertrain engineer and if I am not mistaken was involved with the design and development of the Northstar.

Occasional Full-Throttle Acceleration Is Good For Your Engine

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...

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bbobynski wrote this, imagine a northstar engine running a WOT for 300 hours! I hardly think that an occasional WOT would do any damage. That is not saying that something could not spontaneously break, but I think the chances of that are minimal...

bbobynski >>>> The endurance tests are run on an engine dyno. The throttle is held wide open and the engine speed is controlled by the dyno by varying the load or absorbsion of the dyno. The engine speed varies according to the engine, the peak power and torque points, what the engine is rated for in terms of duty cycle, etc... In the case of a 4.9 the engines were typically tested at full throttle at 4250 RPM which would be around the peak power point. The 300 hours is accumulated over the test period which consists of run events and checks during the test where the engine is stopped, various performance parameters checked, power is checked, etc... Oil is changed about every 100 hours usually... The engine is checked every 8 hours with oil adds and other maintenance done. There are other, similar tests run where the engine is at full throttle and the RPM is varied from peak power to peak torque constantly. On a Northstar engine, that test will run for 300 hours with the engine at WOT, the RPM varying from 6200 to 4400 back and forth constantly. <<<<

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Would once or twice a day be fine, or is that excessive? I like to do them when I see an open stretch! Right now I do maybe a few a week!

My wife tells me that "WOT at every freaking stop light is excessive..." :rolleyes: But I do it anyway...

Great Cars... Awesome engines! :D

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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Personally i think it depends on the health of your engine, listen to it carefully when you do it. I get a rattling noise that makes me nervous, but I think its related to something in the water pump area, maybe a loose braket. Don't do it when you oil is low, and keep your engine in tune. Missing in my opinion puts undue stress on the engine. Missing, pre-ignition and detonation can be caused by ignition problems, ignition timing, controls and mechanic problems (valves, etc). I believe these aberrations / instabilities at high RPM can cause damage.

Clean the EGR, throttle body, check the routing of your ignition wires once in a while moving them away from areas that they are arching against, change the fuel filter and air filter regularly.

I just did a bunch of work to my engine, new fuel rail (under warranty), clean EGR, clean throttle body, wipe down all ignition wires and install wire loom over their entire length and meticulously routed them, wiped down the coils, and changed the air filter and it made a huge difference at WOT, it feels much smoother whereas before, it was as if I could feel a high frequency miss that you could feel in your gut, NOW it feels like a rocket engine.

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Hey Guys, do not do WOT with the engine cold, that's definitelly bad. Let the engine go to the normal operational temperature, say 200 F, and then do WOT.

1960 Sedan De Ville (sold)

1970 Coupe De Ville (sold)

1987 Mazda RX-7 (sold)

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WOT in a cold car and the transmision shifts early, around 5700, very smart car...

My shortstar Intrigue does this too!

But I agree... Cold Car + WOT = bad idea....

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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The previous owner of my car, was a real estate broker, who only drove the car from house to house. Becasue of this, I have a very slight knock, which I think is do in part to the 45k miles she put on it, without really driving it too hard. When I first got the car, I slowly started to, in a sense, re-brake it in. Over a few thousand miles, I would increase the amounts of throttle I gave it, until I started doing WOT's. Even though I do it all the time, and have had the top engine eclean done, I still have a slight knock.

I have to say though, that this engine sounds very, very good at WOT. The sound is nice a smooth, with no oscillation I guess you could say. The knock gets a little louder, if I drive it slowly for too long. Once I gove it a few WOT's, it gets much quiter. I drive my car pretty hard, but always let it warm up fully before I do. I guess I WOT my car about 2-3 times a day, but never for more than a few seconds. I try to do it enough, so that I don't get a cloud when I do it.

It's always funny when people at my school tell me I drive really fast, and give it WOT alot more than other people do, and then I tell them that it's recommended. They always have this strange look on their face, and then they say, "Well, my friend did that with his 350, and spun a bearing or something like that". I then go on to explain the Northstar's tendency to build up carbon. After that, they get jealous that they don;t have a car, that requires occasional WOT, to keep running like a champ. I get a real kick out of that. It's mostly from people riving Honda's and stuff.

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I never thought I'd miss doing the WOT thing as much as I do this time of year. The roads have been clear and the outside temps high for the past couple of days. Normally the conditions would be a cause for mild celebration but not with these squishy snow tires. Winter rims and tires. Of course, once in awhile, I just can't help myself and have to give it another go. So I stomp on the gas......Yup, the samething. Feels like the jelly donuts tires and the rest of the car are going in two different directions :blink: .....yeehaw! So I'm reduced to driving around in second gear....I know you can sense the level of excitement here B)

WOTs are Northstar friendly.

"Burns" rubber

" I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. "

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I do WOTs around almost every turn at about 60% of the stop lights and out on the highway is this to much? I am very hard on my gas pedal! :lol: I never felt guilty about doing it cause it seems like lots of people do it to there N*!!!!!

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Defending Northstar perf a qtr mile at a time!!!!

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QUOTE (Ranger @ Feb 8 2005, 11:02 PM)

Here is a quote from out resident expert. If you are unfamiliar with him, he is a GM powertrain engineer and if I am not mistaken was involved with the design and development of the Northstar.

************************************************

I had to reread your post to understand if you'd taken touch-typing lessons or you'd simply copied a Guru post. :D

A WOT or three, once a week or two, is good fer me. My "Baby" sucked up a quart in 800 miles when I first insured her. I immediately took advantage of the advice on this forum and extended that to 1600 miles per quart. Besides, it's fun!

I NEVER beat on Baby when she's cold. Careful with comments now . . . .

Regards,

Warren

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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QUOTE (Ranger @ Feb 8 2005, 11:02 PM)

Here is a quote from out resident expert. If you are unfamiliar with him, he is a GM powertrain engineer and if I am not mistaken was involved with the design and development of the Northstar.

************************************************

I had to reread your post to understand if you'd taken touch-typing lessons or you'd simply copied a Guru post. :D

A WOT or three, once a week or two, is good fer me. My "Baby" sucked up a quart in 800 miles when I first insured her. I immediately took advantage of the advice on this forum and extended that to 1600 miles per quart. Besides, it's fun!

I NEVER beat on Baby when she's cold. Careful with comments now . . . .

Regards,

Warren

:lol::lol::lol: No touch typing here. I'm a "hunt'n pecker" (so to speak :P ) It was cut and pasted. I couldn't agree more on with making sure she is at normal operating tempurature before whooping her.

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