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Discussion Starter #1 (Edited)
Hi all,

I wanted to get some expert opinions regarding this topic. I own a 67 Camaro and a 97 Acura NSX. One the NSX forums, a member asked this question http://www.nsxprime.com/forums/showthread.php?t=39469 regarding shifting early and babying the motor being bad for the NSX's engine and causing premature wear.

My opinion was that as long as the engine is not "bogging", cruising at a RPM around 2000 is fine. Most opinions went the other way saying that it causes premature wear. I realize that the engine in the NSX is designed to redline much higher than most, but there are 2 different cam profiles because of the VTEC. The engine has plenty of torque around 2000 RPM.

I know how many professional mechanics/good shadetree mechanics are members here and wanted some opinions.

Thx in advance.

Here's a few pics of my "babies"



 

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I try to keep my four cylinder engine running closer to its peak torque output. It has almost no torque whatsoever (wraps up to 8400) so, I run about 3800 - 4400 when cruising. It also has dual cam profiles (VVTLi from Toyota) and my best guess is that the peak torque for the low speed cam is around 4k. Peak torque for the engine is at 6800, but that is on the high lift cam lobes. I get roughly 28mpg around town and the gas pedal works well enough at 4k that the Spyder can get out of the way when it needs to. My thoughts are that if I can get 31mpg on the interstate and I'm crusing at a constant 4k, I should be doing much better without the extra drag by keeping the revs the same.


I treat my V8's differently. They use regulated gas leaks to determine the amount of fuel that goes into the engine so I run them as low as I can. With my 4.88's, that translates to about 2400rpm at 35mph. Still not much of an econo car.
 

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IMO. It alway's better to spool up a engine than to bog or lug it down. Low RPM and making it work hard can squeeze the oil wedge away from the bearing and metal to metal contact can occur. Twisting of the crank is also more prominent while loading the crank as unnecessary raise in oil temps.
 

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Discussion Starter #4
johnsongrass, when you say low RPM, what range are we talking about here? 1000, 1500, 2000?

I guess it just makes sense to me that if my engine is spinning at 2000 rpm then it is wearing less than it would be while spinning at 4000 rpm. Is this not so?

Follow up question: My minivan is an automatic and will cruise from 1500 - 2000 rpm without downshifting. Why does the manufacturer allow this to happen when they could easily design the tranny to downshift at a certain point to keep the engine in the upper rpm band?
 

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With the NSX I wouldn't run it below 3000-3500 rpm. These engines are designed to run at high rpm. It wont effect engine wear. With the Camaro, depending on how its built 2000-2500 cruising rpm, regardless of vehicle speed should be ok. I always shift my 406 at 3000 rpm min, mostly 4000 rpm and cruise at 2500-3000 rpm. Anyone who want to race me I'm always ready, always in the right gear. Yes, I don't street race!
 

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I don't know if we got a definitive answer...or maybe I missed it.

I've got a 406 in my El Camino, 200R4, and 3.42 gears. It's not uncommon for me to be in fourth gear and doing 1500 rpms on the street. The engine doesn't seem to be lugging and moderate pick up is good. Also, I've been happy with the mileage benefit.

Before, I had the stock 2.41 gears and that DID lug.
 

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I don't like running any engine under ~2000RPM, but I occasionally let my V8 Ford cruise at down around 1500 or so, but only because it won't stay in 2nd gear at 20-25mph, & only if it's only very lightly loaded. Lugging is a good way to beat your bearings to death.
 

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Discussion Starter #8
Question: when "lugging" is referred to, what is meant by that?

I always was taught not to let the engine "bog", meaning too much strain at a low rpm. You hear the engine moan and even can get some detonation. Is lug and bog the same?

Thx
 

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In that context I would say yes it is the same. It is said that it's always better to let the engine spin freely while cruising. It shouldn't have to give more gas to keep the same speed and when hitting inclines you'll only have to give a little more gas and won't loose speed as easily. Also, you'll start lugging much quicker when you hit an incline and want to stay in the same gear.
 

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Another potential problem with low RPM operation is premature failure of roller lifters. Not enough splash lubrication on the roller bearing.
 

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I've tryed to explain lugging to my spouse (whoops shoucn't mention spouse) So i said it was keeping the motor happy,iff at low revs and ya need to open throttle lots to get it movin (Manual box) change to lower gear and lift Heavy foot, she's got an auto now.. I call it No Ping,,..
 
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