Important to PUSH the Northstar once a week?

[BeelzeBob]

When I owned my '95 ETC, the dealer told me to hit it hard once a week. I was reluctant, but did so once every two weeks. They told me it was very important for the Northstar engine. Not only does it clear out carbon - but it does something else..

Does anyone know what this 'something else' is? I trusted my dealer so I did it and had no problem doing it. But, I can understand why one may believe that the dealer just wants you to beat on your car to break it..

Any thoughts?

[Katshot]

Yeah, it increases the possibility that you'll need their service department.
Blowing out the carbon is ok but there's no other benefits I've ever heard of. Maybe he was talking about drying out the exhaust?

[Devil_concours]

i don't know. hard acceleration is never good for transmission. Correct me on this if i'm wrong.

[Chuck C]

besides, dealers have a tendency to talk off the top of their heads

[Cbody]

Originally posted by Chuck C
besides, dealers have a tendency to talk of the top of their heads

Well that's the nice way to put it

Personally I believe it's a load of bull. I cannot fathom how "hitting it hard" could be of any benefit. Now "back in the day", when say your cad was carburated, and was only used for idling around town that has more of a basis in reality, but considering the tight nature of the PCM controlling all aspects of the engine I find it almost absurd that the engine would *need* any kind of driver influence to remedy any aspect of it's operation. As long as any EFI engine reaches operating temperature during operation then that's really all that it needs. If you need to run it *longer* in order to reach operating temp then that I could understand, but running it *harder* isn't exactly beneficial.

I'd love to know the reasoning behind the dealers statment.....I've been proven wrong more than once (a day), but I suspicion that the dealer is essentially full of it.
Jay

[jadcock]

Sure, idling the car around all day and pampering it is a sure way to keep your suspension and paint like new, but your engine hates idling. It'll do it forever, but after a while, the carbon deposits will build up on the pistons and eventually cause problems.

Benefits I can see from winding the car every once in a while:

1) Blow out all the carbon deposits.
2) Really heat up the converter and clean it out.
3) Clear the mufflers out of any interior rust/scale.

You'll notice, I'm sure, that if you only kick it every once and again, you'll get some smoke out the tailpipes. This is normal with every car and is indicative of the carbon and the rust blowing out. If you do this more often (like many times each day), you won't see this smoke anymore.

The transmission is strong (4T80-E) and can handle the power. If it couldn't, Caddy would have put it behind the Northstar. It's the strongest TFWD transmission GM Hydramatic makes. WOT upshifts won't hurt the tranny at all (unless something else is wrong, like you're low on fluid or something).

[Katshot]

The higher velocity of the airflow during full-throttle runs can help clear deposits that have accumulated in the combustion chambers, and exhaust system. That, combined with the sudden expansion of several items along the way due to the excess heat brought on by the full-throttle run helps loosen deposits too.
So bottom line, the heat loosens the deposits, and the increased airflow helps blow it out.
Hopefully this explains it a little better.

[Cbody]

I'll have to stick by my assertion from before, I'm just not seeing any carbon buildup, nor any other deposits accumulating on any EFI engines to the degree seen on older carburated engines. As long as the engine is operated for a long enough time for the engine to reach operating temp and actually driven at anything approaching a normal RPM range then you shouldn't have any problems with any foreign buildup, either in the combustion chamber or in the catalytic convertor (exhaust).

If there is actually a buildup of either carbon or other particulate in the engine, or exhaust then I'd suspect that it's not actually a problem with how it was driven, but more likely a problem with maintenence, ie. oil change intervals, leaking injectors, etc.

Of course, *if* the engine is literally only run for a few minutes at a time, or continually short tripped, then you will encounter problems, mainly due to the buildup of condensation internally which will destroy the oil in short order. But again, that's more of a temperature, or maintenence issue than it is a rpm issue, and no ammount of full throttle blasts will cure that.

I would have to wonder though, that if you're seeing smoke exiting the exhaust during full throttle blasts, that perhaps what you're seeing is actually excess fuel, or more likely burned oil, than carbon and rust deposits. Carbon and rust deposits really aren't smoke, nor to they resemble smoke upon exit.

End result, as long as the engine is kept in top shape, and driven normally, there shouldn't be any buildup of either carbon or rust to a degree that would hinder engine performance/mileage.
Jay

[jadcock]

It's true that newer MPFI engines will get "less" dirty inside, but the fact is, a byproduct of combustion is carbon and the engine WILL get dirty inside. In fact, a de-carboning procedure is a VERY common procedure for a dealership to perform on a Northstar. In fact, there's even a TSB out about carbon deposits doing so much as to unseat the rings during "normal driving":

http://www.nhtsa.gov/TSBScans/sb631313.pdf

You are correct -- much of the smoke at WOT is excess fuel, since the engine runs rich at WOT to protect the pistons and engine from detonation. But this will appear as a brown "smoke". Oil burning is usually a bluish smoke, pretty distinguishable from excess fuel in the exhaust. And when I say "smoke", I don't mean a plume...I mean a light dusting. Pretty much every car I've seen on the road will "dust" a little bit at WOT.

In summary, the amount of deposits in your engine is certainly related to the state of tune your engine is in. Having said that, it's never a bad idea to go ahead a wind out your engine every now and again. The Northstar engine has a very aggressive hatch pattern on the cylinder walls to retain oil for good lubrication during high-RPM operation. This is there as a design feature and has the unfortunate downside of increased oil consumption and combustion chamber depositing. The upside is the rings and cylinder walls are lubricated VERY well and engine wear is brought to an absolute minumum. The Northstar isn't your average small block Chevy.

[jadcock]

As an aside, someone could convince me that WOT blasts can help dry out the exhaust. Normal exhaust temperatures are in the 600-800 degree range. Way back at the muffler, this may or may not be enough to keep away the condensation. At WOT, exhaust temperatures can sky-rocket -- to upwards of 1500 degrees. This will certainly burn away/blast away any stray molecule of H2O in the exhaust system somewhere.

[elwesso]

I will have to semi- agree on both points. There are tons of old people that never push their cadillacs, and they run just fine. Also, there are people that drive their cadillacs really hard, and still run fine. I suppose pushing it once in a while cant really hurt it, i dont really see the need to do it a lot. I can see the benefit of that extra pressure to blow all the crap out of the exaust. Personally, i dont think that doing this will make your car run longer and make it more reliable, although i do think it helps more than it hurts.

[kcnewell]

This is a little off topic, But, I've got this engine in my shop today, the guy didn't want to ruin YES I said RUIN it with unleaded gas so he pulled it in the garage and parked it in 1988! NOW, He wants to drive it. Needless to say He did more damage to the engine by leaving it idle than he EVER would have driving it! The engine is totally shot,seals,rings everything. He left the gas in it for 14 years! ( You shoulda smelled THAT! ) OK, Back on topic....I like to run my engine kinda hard because I like the feel of the thing working hard. On the newer engines with all the computer controls you don't need to "BLOW THEM OUT" Bear in mind that no matter how good an engine is....Pushing it to its limit is ALWAYS a risk. It's a machine and when you use it hard it can and eventually will break! Your dealer knows that and is in fact talking out of his head as you say. The problem is...His head is firmly stuck in his ass! That's my opinion and is not intended to be construed as the opinion of Cadillac Forums.

[Dead Sled]

in a way its a warranty litigation in the making

[BeelzeBob]

Thanks for all the info here. Lots of good points made.. I learned a thing or two.

[jadcock]

Originally posted by kcnewell
On the newer engines with all the computer controls you don't need to "BLOW THEM OUT" Bear in mind that no matter how good an engine is....Pushing it to its limit is ALWAYS a risk.

This is true. The "limit" is not necessarily the "redline" of the engine, though. The engine can and will run at redline all day long. You'd be surprised at the testing and validation procedures that the Northstar engine went through. Here's one, for example, to validate the head gaskets' strength and durability:

A cooler chills a batch of engine coolant to very cold temperatures (I forgot the exact temperature, well below zero) and this coolant is pumped into the engine. The physical engine gets so cold, frost forms on the outside of the block. The engine is then started and immediately brought to WOT and run at 6000 rpm ("redline") until the coolant is near boiling (about 250 degrees). It's then immediately shut off and that coolant is cycled out and a new batch of subzero coolant is pumped in and the engine is shocked with this vast change in temperature. This is one cycle, and THREE HUNDRED CYCLES were performed consecutively and the engine was then disassembled for analysis. No head gasket failures. No mechanical failures. The thing performed exactly as designed.

When I heard of the many rigorous tests the Northstar went through to validate its design, I was utterly amazed. The worst thing you can do to a high-speed high-performance engine like the Northstar is to granny it around, never opening it up. Back in the days of pushrod V8s with 5000 rpm redlines, constant high speed was riskier because of the design and construction of components (cast iron cranks for instance). The Northstar is designed and built as a world-class engine, with an array of forged and cast alloys in use where appropriate. It is built to run and run hard!