Why's the 3.1 weak?

[peeeot]

I'm always reading on here about how the 3.1/2.8 is so weak and disappointing from a performance perspective. What is it about the design of this engine that makes it such a poor performer?

 

The only thing about it that is obviously bad to me is the exhaust. The log-shaped manifolds with their 90* turn and the way they join together and how the pipe splits off at the middle of the firewall side manifold cannot be very efficient. What else is wrong? Ill-breathing heads? Tiny valves? Poor programming? What?

[97loudcut]

well the exhuast size is like 2 inches all the way through..the intakes flow like shitpies..

 

 

[19Cutlass94]

They were built for reliability and not performance. You have to remember, these cars arnt exactly sports cars, there economy cars. Its been proven that you can make power with these engines. They can take abuse and were designed for reliability, not performance.

[Crazy K]

pushrod engines are lower powered then OHC engines as well. proven durability traded off for power. at the time they came out, they were relatively powerful compared to the average car, but since then, development has made newer engines more powerful. anyhow... if there were no 3.4 or 3800, and we compared the 3.1 engines to the iron duke.... they wouldn't be called weak.

[THe_DeTAiL3R]

Just compare 2.8/3.1MPFI to any other small pushrod engine of the same era. We had a 1985 T-bird 3.8 and it was slow as a turd.

 

Since then the 3.1 evolved into the 3100 (decent for a daily driver), and has kept improving the basic design to the 3400, 3500, and 240hp 3900 60* pushrod V6.

[Brian P]

they can feel "strong" when they're healthy and well cared for. When I had a '90 Cutlass Coupe, I raced my friend who was driving my sister's old '93 Cutlass with the same 3.1. With no mods between them, and my car having 70k more miles, I had almost a car-length lead by 60. Just goes to show how much they can vary.

[Supreme Cutlass]

they can feel "strong" when they're healthy and well cared for. When I had a '90 Cutlass Coupe, I raced my friend who was driving my sister's old '93 Cutlass with the same 3.1. With no mods between them, and my car having 70k more miles, I had almost a car-length lead by 60. Just goes to show how much they can vary.

werd, Maintenance will do wonders. But c'mon, it's over 18 years old.

 

Besides, throw a Turbo on it and it screams ..got to give it credit for that.

[THe_DeTAiL3R]

Also, mine can feel much stronger depending on the weather.

[GutlessSupreme]

low compression and the heads don't flow for shit.

 

 

Also, mine can feel much stronger depending on the weather.

 

my cutlass seems much stronger some days in the cold, then others it might as well be 90 w/ 100% humidity.

[peeeot]

the 3800 is a pushrod motor too. I suspect it has more going for it in the way of design than just displacement though. As far as I can tell, the advantages of the overhead cam are 1. can have more valves per cylinder, though that isn't always done (Ford 4.6L for example) and 2. better spark plug placement/combustion chamber shape (also doesn't especially apply to the Ford 4.6L). In the case of SOHC engines like the Ford 4.6, I don't see the advantage over a pushrod engine. I see enormous heads that take up a lot of space. What advantage does it bring?

 

What did they do to the 3100 to make it better than the 3.1?

[THe_DeTAiL3R]

 

What did they do to the 3100 to make it better than the 3.1?

 

Improved flowing intake, better shaped heads, etc.

 

Read this, I think you'll find alot of answers.

 

http://60degreev6.com/view.php?pg=familytree

[slick]

As stated above, technically, the 60* V6's are pretty strong engines. But, when talking power wise, they aren't exactly the most powerful. Without some sort of air pump(SC or Turbo), getting a decent amount of power out of them just isn't feasible(unless you have a deep wallet to play with). If you had a crazy amount of money to spend, you could get a ton of power out of it N/A. But, it would require a complete re-design of the intake and exhaust ports in the heads, higher compression, as large of valves that could possibly fit, custom designed intakes(which would require some crazy math, and an even more insane designer!), and a TON of tuning.

[kuntzie]

me aswell as every other turo 3.1 owner

 

135xxx miles of most likely pure abuse.... fast and definitly not weak as mine is handleing lke 380 hp at the crank

[rudefyet]

IMO 2.8/3.1 = made to compete with Jap 4 cylinders power and gas mileage wise, yet have more torque

 

keep in mind 16 years ago 140hp wasn't that bad

[jdcutty]

Also, it doesnt feel weak when you put em in a beretta or sunbird. Or mate em to a 5 speed. Or, both, for added fun.

[Nick1234]

i hate when i have to drive people around. Car feels so weighed down, and take a while to get up to speed, and you can tell its working. I also think that at times it being less powerful affects my mpg cause it works harder to attain a speed. My cousin has a 3.8 in his ltz and kicks my ass in mpg. I have only been averaging 22. Im not sure whats up.

[peeeot]

That's how my car drives, like it's carrying passengers all the time. It weems to work pretty hard just to keep up with traffic. Power to weight ratio is an important factor in MPG, but small displacement is good for traffic because that means less air and fuel pumping through at idle. I always average between 19 and 22, which I can't really complain about because it's better than EPA but I have to drive grandmotherly most of the time to get that. Pretty sure in my case the extra convertible weight is at fault.

 

So we say that 140 hp was good for the day, etc, but it isn't anymore. Part of that I'm sure is due to how common DOHC designs with variable valve timing have become. Also, I assume, improvements in software/engine management controls have helped. What other developments have lead to the higher HP levels across the board? Engines haven't necessarily been getting bigger, just more powerful.

[19Cutlass94]

roller rockers, more efficient burning engines etc etc. Just about everything is better with todays engines then they were 15yrs ago. OK, well maybe everything execpt electronics.

[THe_DeTAiL3R]

I'd like to argue the fact that smaller displacement engines use less fuel in the city, in some circumstances.

 

1. I agree w/ it using less fuel at idle.

 

2. What about actual accereration? Stop and go (say lots of stop signs for example).. my 3.1 eat gas like crazy. I think I get like 16mpg with the city driving that I do. A 3.8L w-body just feels like it doesn't have to work as hard to get back up to speed. I'm not extremely hard on the gas, but not easy either. Highway cruising I can get like 30-35+ MPG I don't think there is anything wrong with my engine.

 

I think that there has to be a balance of car weight/engine size to get the best fuel economy.

[rudefyet]

my 3.1 got 32mpg highway

 

if you're getting less then 30, you have issues

[Crazy K]

my 3.1 got 32mpg highway

 

if you're getting less then 30, you have issues

I'm having issues, my mileage got to a high of 27mph, and dropped to 20! think I need a new icm or coil, it seems to have a heat issue.

[peeeot]

I'd like to argue the fact that smaller displacement engines use less fuel in the city, in some circumstances.

 

1. I agree w/ it using less fuel at idle.

 

2. What about actual accereration? Stop and go (say lots of stop signs for example).. my 3.1 eat gas like crazy. I think I get like 16mpg with the city driving that I do. A 3.8L w-body just feels like it doesn't have to work as hard to get back up to speed. I'm not extremely hard on the gas, but not easy either. Highway cruising I can get like 30-35+ MPG I don't think there is anything wrong with my engine.

 

I think that there has to be a balance of car weight/engine size to get the best fuel economy.

 

I agree with you completely. Note that I also said that power to weight ratio is an important factor. It's all about balance. In periods of extended idling, smaller displacement is always best. In fact, smaller displacement is always preferable to larger for economy IF power is held equal. Which is why most cars today have 4s and 6s instead of 8s; these days we don't need the extra displacement to make the amount of power we want. As often.

 

I agree that an inadequately small/powerful engine will use more gas than a larger, more appropriately matched engine in cases of repeated acceleration. It will have to rev higher to produce enough power and will ultimately pump more air and gas through than the larger engine turning slower. Efficiency varies with rpms/load too, but I think I've heard that engines are usually running more efficiently when they're working harder. That doesn't mean less gas overall is being burned though.

 

Here's the one case that REALLY baffles me: the new Corvette. The base 6L model gets 18 city 28 highway. The z06 with its 7L(!) engine gets 16(!) city and 26 highway. Both with manual transmissions. These are pushrod engines and all 8 cylinders are always firing--no variable displacement technology employed. How does an engine with double the displacement manage only 1 mpg worse in the city than my 3.1? Based on those numbers, I would expect to consistently return better fuel economy in a new Corvette than I get in my Cutlass. I just don't know how they do it.

[AWeb80]

Pure city, i'd get about 20-22 mpg....highway, i've got as much as 29-30 @ 80 mph.....

 

my car must be a freak.

[19Cutlass94]

Lately, driving with the heat on, and stepping into it a decent amount, Ive been getting ~25mpg around town......

[GutlessSupreme]

Highest MPG ever obtained: 23 mpg.