My car is a 85gt 2.8 an run's strong with a 4 speed man. I run down the freeway at 60 to 70mph at 60 my rpm is 2500 an at 70mph it's 3k give or take 100rpm. What id like to know is what is a safe cruzing rpm an what is starting to be to much for the motor when freeway driveing. I understand not to red line but is 3 to 3500 to much?
Great. It run's an sound's ok at 3k+ rpm, an dosent make like it's over reved an still has plenty of trottel left. Im going on a 3k mile trip from Cal to fla an don't want to blow, or over work my motor!
3k is fine... the only thing is, your fuel economy will stink. You really want to keep it around 2,500 to get decent fuel economy. But... this engine really is safe to 6,000 rpms (and somewhat beyond as well).
My V6, 4 spd also ran that fast on the freeway. In fact my Mercedes SLs do the same thing. Id say its just typical. My old 60s cars lumbered down the freeway at 1500-2000 rpms.
I have an 87 GT v-6 70=2,500 100=3,500. I have not went any faster
You have a different transmission than the OP.
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Originally posted by 82-T/A[At Work]: ...this engine really is safe to 6,000 rpms (and somewhat beyond as well).
I disagree. The '85 - '86 V6's didn't have the same improved-design oil galleries that the later blocks did. Sustained high revs will shorten the life of the crank, cam, and bearings due to poor lubrication. You won't run into problems at the 3000 - 3500 range in my opinion though.
The last ~500rpm of many 1980s GM tachs are shaded in yellow. I've often wondered - does that actually mean anything, or is it just for looks? Is the "yellow zone" only rated for split-second excursions, versus running continuously? I don't know what GM's standards were/are for deciding where an engine's rev limit is.
I disagree. The '85 - '86 V6's didn't have the same improved-design oil galleries that the later blocks did. Sustained high revs will shorten the life of the crank, cam, and bearings due to poor lubrication. You won't run into problems at the 3000 - 3500 range in my opinion though.
Even with the 87-88, I'd not recommend running them over ~4500 without serious work done to them. The engine isn't making any power that high, and you greatly increase the chances of critical failure. The valvetrain isn't built for it, and the engine is choked for power.
Stock 2.8L dyno chart... you can see calling the power usable up to the 5500 yellow line is being a bit optimistic.
There is nothing to gain by keeping a stock 2.8 above 4500RPM...
My 2.8 GT pulled well past the 4500 rpms you speak of. Easily up to 5200-5300. And 6000 never hurt it any. It was running good when I pulled it for my swap.
Originally posted by weaselbeak: My 2.8 GT pulled well past the 4500 rpms you speak of. Easily up to 5200-5300. And 6000 never hurt it any. It was running good when I pulled it for my swap.
It will rev that far, yes. It does not make power up there though, so it's just a waste of gas to make some noise.
Thank's every one, I'm not hard on my motor an most likly never run at rpm's over 3500 to 4k inless I'm steping on it to pass somone. I just want to know if runing at highway speed's for exstended time with the rpm's at 3k to 3500 ok for my motor. I run dino/syn blend oil, an my motor is in good shape.
[This message has been edited by georgie (edited 02-10-2014).]
My 2.8 GT pulled well past the 4500 rpms you speak of. Easily up to 5200-5300. And 6000 never hurt it any. It was running good when I pulled it for my swap.
If you read my post, I was talking about power output not maximum engine speed. I have an 88GT with a 3 speed, I know all about high RPMs on the freeway.
I have a 86 SE auto. I run 75-80 mph 5-6 days a week 25 miles each way to work. Been doing it for past few years on and off for about 20,000 miles. I was a travel nurse for many years so I also would drive between 250 and 500 miles at a time, A few times a year. Owned car from 74000 miles and drove it from Reading PA to Macon Ga when I got it. Never has this car had a drivetrain issue.
I now have a better feel for how I will run my motor on the 3k mile's to my home in key west fla, for cal. Ill be runing 16 or so hr's aday for three or so day's, that's why I'm conserned. Its a lot of long drive time. Once again thank's to all for the helpfull info!!
If you can make a 2 hour trip with the car, you'll probably be able to make a 16 hour trip as well.
An engine's happiest days are when its warmed up, has clean oil and is running at a constant speed within it's designed RPM range. 3000-3500 RPM is pretty much right in the middle of the RPM range. As long as it is in good condition it will be fine.
As far as the power curve discussion, GM rated the peak output at 5200rpm. That seems roughly inline with seat of the pants on my car, although I could be peaking a little below that. Whether it makes sense to ever go above 5500 depends on gearing of course. It would be silly to stay there long term, but I wonder if the yellow marking was supposed to indicate that it would hurt anything. In any case, cruising at that RPM is not something anybody would be likely to do. Downhill extreme engine braking, maybe.
Whoever has been flooding the Fiero wiki page can write what ever they want, it's Wikipedia after all, but peak HP at 5200 with the stock cam? I have seen too many real dyno sheets of stock 2.8s with the torque nosediving so fast after about 3600-3700 RPM that peak power hits around 4500-4700 RPM... and 115 HP at the wheels is pretty good for a 2.8.
Not a single one of these cars peaked past 4700RPM...
[This message has been edited by carbon (edited 02-11-2014).]
The 5200rpm number is from the "DIY" Pontiac manuals, not wikipedia. I'd link it but the site that had them isn't up anymore. Maybe the age of the vehicles is skewing things. Or just as likely GM's numbers are wrong. Regardless, those graphs are probably more realistic for all of us who don't have a time machine. 2 or 3 of those held their plateau up to 4900.
[This message has been edited by armos (edited 02-12-2014).]
My 86GT dropped a valve and died at 65K miles while running at 55-60 on the interstate. I replaced it with an 87 2.8 with over twice as many miles and it runs great now. Mine is also an automatic so I see similar RPMs.
Thanks for the Dyno graphs. Most folks never get to see what to really expect from their cars.
It is interesting that his 85 seems to have the same final gear ratio as the 88 automatic. My 88 GT turns about 3000- 3500 at highway speeds. As mentioned, as long as the engine is in good shape and has good oil and coolant, it should do just fine for hours on end. Such driving is the best way to put a lot of miles on an engine.
My 86 SE V6 had 145000 miles on it when my wife made me sell it. It had about 250 miles per day commuting for about 3 years and did great. The body/paint was in sad shape from the Texas weather, but the engine was in great shape.
Whoever has been flooding the Fiero wiki page can write what ever they want, it's Wikipedia after all, but peak HP at 5200 with the stock cam? I have seen too many real dyno sheets of stock 2.8s with the torque nosediving so fast after about 3600-3700 RPM that peak power hits around 4500-4700 RPM... and 115 HP at the wheels is pretty good for a 2.8.
Not a single one of these cars peaked past 4700RPM...
This is with a stock short block, CNC ported not polished heads (All ports have exactly the same diameter), custom cam and the straw-like upper and mid plenum deleted and replaced with a unit that allowed me to use atmospheric pressure over 100%.
So I made 42WHP at 5800RPM and 28lbs/ft peak over your results. At 6000RPM my 2.8L is 54WHP up and 74lbs/ft over your engine all on 93 octane pump gas. But if you look at the time stamp that's 10 years later. Moral of the story; never say that's it because technology will catch up to you!
