WOT: Is it really effective?

detroit99sts · #1 (**permalink**) 02-03-07, 02:20 AM

Hi,
I am one of the unfortunate Caddy owners (99 STS) who had to replace a Northstar engine at low mileage (60,000) due to head gaskets blowing. Ever since I have been a member to this forum, I constantly read about the benefits of regular WOT'S. I hear WOT'S clean out carbon, which helps prevent head gasket failure.I am still a little eery about doing these "WOT'S".

Someone please reassure me that it is either healthy, or harmful:

Is it really worth doing?
Can it be harmful in any way to other engine parts?
How come other engines do not require WOTS, and dont have head gasket issues? Is it just the Northstar that requires WOTS?

THANKS,

-Mike

***Lord Cadillac*** · #2 (**permalink**) 02-03-07, 08:29 AM

This has already been discussed many times.. Try doing a search next time. Otherwise, I'm going to move this to the Northstar section since it's not directly related to the Eldorado or Seville..

To answer your question, wide open throttle (WOT) is good for the Northstar engine. Maybe not all the time, but at least once or twice a week. The engine was designed to be pushed. Most people never push their Northstar and this builds up lots of carbon. Go ahead. Don't worry about it. The engine was meant to be raced..

Other performance engines are also designed for WOT - at least once in awhile.

JimHare · #3 (**permalink**) 02-03-07, 09:36 AM

Quote:

Originally Posted by detroit99sts

<SNIP>... I hear WOT'S clean out carbon, which helps prevent head gasket failure.

The regular application of WOT exercise has little or nothing to do with (premature) head gasket failure. HG failure, on the rare occasion when it does occur, is usually caused by the ageing of the coolant, which loses it's anti-corrosion properties, causing chemical reactions which eat through the HG material, which causes coolant to enter the block passages which lead to the head bolts which then corrode and become dislodged from their threads. The combination of aluminum and corrosive coolant is not good.

Quote:

Originally Posted by detroit99sts

Someone please reassure me that it is either healthy, or harmful:

Is it really worth doing?
Can it be harmful in any way to other engine parts?

The design of the Northstar is such that it is good mechanical practice to stress the engine on a semi-regular basis to keep it healthy. WOTs become more "beneficial" the lighter the normal load on the engine. If you putter around town at < 30MPH for most of your use, the WOT becomes more beneficial than if you regularly drive at freeway/highway speeds. Both of my Caddy's see frequent, fairly high speed highway driving, so the WOTs that I do probably don't benefit the engine so much as provide psychic satisfaction.

Here's a way to test and see if you are a "putter-er" - Reset your average MPH number, and then after two or three weeks of REGULAR driving - see what your AVERAGE MPH works out to - if it is LOWER than about 30 MPH, you need to do some WOTS occasionally. My average for the last four weeks is 48MPH - because about 80% of my driving has been at freeway speeds of 65+.

Quote:

Originally Posted by detroit99sts

How come other engines do not require WOTS, and dont have head gasket issues?

Ahh, but perhaps they DO, and perhaps they DO. Unless you spend your entire day browsing OTHER automotive forums, you won't come in contact with other owners of other cars with perhaps the same kinds of problems. The Northstar is by no means the only engine to suffer the consequences of (usually) improper or poor maintenance habits. Nor should you in any way construe the overall lifetime engineering history of the Northstar by the comments in this (or any other) forum. The people who frequent these forums are a tiny part of a miniscule fraction of a small minority of a very low percentage of Northstar owners. Deriving an opinion about the Northstar from a population such as ours is statistically inaccurate, to say the least. Considering that there are upwards of 750,000 or MORE Caddy Northstar engines powering cars all over the planet, one would have to sample a much larger percentage of owners to get an accurate representation.

Quote:

Originally Posted by detroit99sts

Is it just the Northstar that requires WOTS?

No. Pretty much any engine that produces the HP and Torque of the Northstar with the relatively small displacement it has is of a design that optimizes output at higher RPM - and actually, ANY automotive engine will benefit from occasional use at it's highest output RPM range - it's just the nature of the beast.

With regular maintenance, and barring catastrophic failure that can not be predicted, the Northstar will easily last 150,000 miles without a rebuild - it is just BECAUSE of things like an aggressive cylinder wall honing pattern (sacrificing oil for wear and tear) that the wear on internal parts is much lower on average than with a cast iron, OHV engine that produces 150 HP out of 1/3rd more displacement.

I'm not a mechanical engineer or anything of the sort, but I've always head, and read, that most mechanical devices are designed such that they produce their most efficient output within a specific operating range that matches the proposed application.

In other words, tractor engines are designed to run at 1500 rpm, all day long. Take your average John Deere up to 6500 RPM and it will probably be detrimental to it. F1 engines are designed to idle at 10,000 rpm and produce their highest output at 15,000 RPM. Mechanical devices are not like the human body, where the "harder you push them, the more likely they are to fail". Engines designed for prop- and jet-powered planes run flat out full throttle 90% of the time.

detroit99sts · #4 (**permalink**) 02-03-07, 10:21 AM

Fellas, thank you for the reassurance. I feel alot more confident in applying these weekly WOTS.

JIM HARE: Special thanks to you buddy, in taking time to write me a 4 page summary (lol). I feel you know what you are talking about. I really appreciate it man !!! Have a nice day brotha.

-Mike

**Ranger** · #5 (**permalink**) 02-03-07, 11:49 AM

I recall our old Guru saying that the Northstar when it was being tested would be run on the dyno for 300 hrs (12.5 days) straight at WOT. That should alleviate any fears you have.

misfit6794 · #6 (**permalink**) 02-03-07, 12:40 PM

I have a habbit of giving my N* WOT once a day

if not more.

***Lord Cadillac*** · #7 (**permalink**) 02-03-07, 12:53 PM

Quote:

Originally Posted by Ranger

I recall our old Guru saying that the Northstar when it was being tested would be run on the dyno for 300 hrs (12.5 days) straight at WOT. That should alleviate any fears you have.

Yeah, I remember him saying this.. That's just amazing (to me, anyway)...

chazglenn3 · #8 (**permalink**) 02-03-07, 01:10 PM

If I don't take the wife's 2002 Explorer out and WOT it once a month or so, it comes down with a bad case of carbon rap. Almost sounds like a timing chain rattling. Quiets right down after a good flogging

JimHare · #9 (**permalink**) 02-03-07, 05:09 PM

Quote:

Originally Posted by detroit99sts

JIM HARE: Special thanks to you buddy, in taking time to write me a 4 page summary (lol). I feel you know what you are talking about. I really appreciate it man !!! Have a nice day brotha.

-Mike

No problem. I was always the kind of guy who turned in 1000 words when the prof only wanted 500....

And I too, as Ranger, remember our Guru Bob telling us that one of the tests the Northstar went through was a 36 hour (or perhaps it was 300 hours, even more astounding) flat-out redline ordeal. If the design survives that with little or no ill-effect, I can't see how a 10 second WOT every week or so could be that dangerous.

thu · #10 (**permalink**) 02-03-07, 05:20 PM

I seem to recall that this was referred to as an "Italian Tuneup".

97STS4ME · #11 (**permalink**) 02-03-07, 07:23 PM

I put mine at WOT at least once every time I drive it. (i dont drive it every day) Ive been doing that for over 18k miles now on an engine that had 73k to begin with. No engine related problems yet. Except my catalytic converter is starting to make the exhuast smell a little funky.

detroit99sts · #12 (**permalink**) 02-05-07, 01:35 PM

I read that a proper WOT requires 2nd gear all the way to redline, then let off the gas until 40 mph (10 times). Is it really necessary to do this 10 times, or is it fine to do it maybe 3-5 times? Also, is it necessary to go to redline? Or can you go to approx. 5,000 rpm?

-Thank You

**Ranger** · #13 (**permalink**) 02-05-07, 05:20 PM

The 10 time is if you have a bad case of cold carbon rap. For general "maintenance" I just do it once a month or so, but you do want a WOT redline shift. Don't worry, you're not going to hurt it.

detroit99sts · #14 (**permalink**) 02-06-07, 12:50 AM

So do I want to put in in 'D' and let it actually shift at redline? Or, should I do as the article said?:"Leave it in 2nd gear , redline it, then let it slow itself down to 40, and repeat (all while still in 2nd gear)"

-Mike

mtflight · #15 (**permalink**) 02-06-07, 04:22 PM

Quote:

Originally Posted by detroit99sts

So do I want to put in in 'D' and let it actually shift at redline? Or, should I do as the article said?:"Leave it in 2nd gear , redline it, then let it slow itself down to 40, and repeat (all while still in 2nd gear)"

-Mike

While doing it in one gear, would in theory stress the tranny less... it also is beneficial to do the "engine overrun" condition where you let the engine slow the car down to 30 or so (make sure there's no traffic unless you want whiplash from the car behind you slamming against you for braking without brake lights lol).

The overrun condition really frees up the rings.