987 2.7 vs 986 2.5 review

[986_inquiry]

Originally Posted by pothole

Take 2.5 v 2.7. it's only another 200c and 20-odd hp. Plus the 2.7 has a little more weight to drag around and taller ratios. I'm not saying the 2.7 isn't any faster. But I've driven one and it's not a dramatic difference. How could it be?

I've also compared a 2.5 with a late 2.9, side by side with a rolling start from about 2,00rpm in second through to about 90 or 100mph ish. Think you lot would be surprised at the modest difference in performance. The 2.9 is quicker, but the gap wasn't huge, maybe a car's length by the top of fourth.

The 2006 2.7 is 240hp, 20% more HP than the 201 hp in the 2.5. That's quite a jump and should be very noticeable to drivers.

but your experience is similar to what I have experienced, the 2.7 (or 2.9 in your case) is not much different than the 2.5 once you're past second gear.

As I said in my review, if you just want fast and you're comparing a 2.5 and 2.7, they're about the same, either is good

Now how do i get the gearing from my old 2.5 into the 2.7? :dance:

[986_inquiry]

seems I'm right, the 2.5 had the best gearing while the 2.7 has the worse

Originally Posted by insite

actually, they're not. you have to consider the final drive. the 6-speed FD is 3.44. the 2.5L is 3.889 and the 2.7L is 3.555. you need to multiply each geary by this number to get an EFFECTIVE gear ratio.

the truth is, the 2.5L has is geared lower than either of the others by a pretty substantial amount. the 2.7L, IMO, is the LEAST desirable. next is the 6-speed. the 2.5L 5-speed has the most useful ratios from a performance perspective.

[southernstar]

986 inquiry, lower gear ratios are not necessarily better even for 'peformance' driving. I assume we can agree that what is critical is matching the gear ratios to the engine. The 2.5 had less torque, expecially low in the RPM range and hence needed lower gearing. What is more, your analysis fails to take into consideration the fact that the 2.7 and 3.2 had higher redlines - an increase from 6800 rpms to 7200, or roughly 6%. I am quite confident that Porsche, in attempting to improve performance over the 2.5, came up with what they believed were the best ratios to achieve this with the upgraded engines.

Brad

[pothole]

Originally Posted by southernstar

986 inquiry, lower gear ratios are not necessarily better even for 'peformance' driving. I assume we can agree that what is critical is matching the gear ratios to the engine. The 2.5 had less torque, expecially low in the RPM range and hence needed lower gearing. What is more, your analysis fails to take into consideration the fact that the 2.7 and 3.2 had higher redlines - an increase from 6800 rpms to 7200, or roughly 6%. I am quite confident that Porsche, in attempting to improve performance over the 2.5, came up with what they believed were the best ratios to achieve this with the upgraded engines.

Brad

It wasn't just about performance. It was about fuel efficiency, too. Ditto features like stop-start and electric steering in the latest Porsches.

If you don't care about fuel efficiency, the 2.7's ratios will be suboptimal.

Also, you've misunderstood the higher redline of the 2.7. With a higher rev range, you can have shorter gearing. In fact, that was part of my point. With the higher redline of the 2.7, the 2.5's gearing will be seriously sexy. You don't want tall gearing with a high revving engine. You want tall gearing with a torquey, low revving engine.

Geddit?

[southernstar]

Pothole, I thought we were talking about comparisons as between 986 Boxsters, not with respect to the 981. I tend to agree about some features on the new 981(such as electric steering and stop/start technology), as being primarily for the purpose of improved fuel consumption rather than performance. As to fuel efficiency in the 986, I checked the brochures that I have at home for the 1999 2.5 and the 2000 2.7 and 3.2 and nowhere is improved fuel efficiency mentioned, whereas the improved performance is. I agree that high-reving 'peaky' engines should be geared so as to have their engines typically running at higher revs; however, the 2.7 was actually less peaky than the 2.5 - i.e., the torque curve was more flat in the sense that it had a greater percentage of peak torque available down low in the rev range than the 2.5. Of course, this is exactly what you would expect with the increase in stroke in the 2.7 over the 2.5. This is all part of matching the engine to the gear ratios and, while I have no doubt that the gear ratios in the 2.5 are ideal for that engine, I also believe that the same is true for the 2.7 and 3.2 engines.

The higher rev limit does contribute to higher speeds in each gear - increases that are greater than one would expect from gear ratios alone. As I have already said, that is a real boon in the cut and thrust of driving around town as well as for autocross, where one need not shift out of second gear (unless the maximum speed on the course exceeds 65 MPH, which is pretty rare in my experience).

Brad

[Meat Head]

The 2.5 is the BEST engine Porsche has ever produced! It is the very BEST in everything that matters! Anything else is just not as AWESOME! Why even discuss any other motor that Porsche has ever produced??? All the best drivers know that if you don't have a 2.5.....you ain't got nothing. Also the best year Porsche Boxsters were ever produced, hands down, 1998. Porsche should have just stopped there when they achieved perfection.





Of course, I could be a little biased because that is the motor in my 1998 Boxster.

[recycledsixtie]

Do I sense a subjective bias here by the owners of the 2.5 motors?
If they sold them and owned 3.2 motors then they would be the best in the world!

[runjmc2]

My understanding is the 2.7 is not a bored 2.5, rather it has a longer stroke (3.07in vs. 2.83in). All things being equal the shorter stroke 2.5 would have a lower piston speed (FPS) and allow for a higher red line than the 2.7.

Are all things "not equal" in this comparison, e.g. the design/materials on the crank/etc of the 2.7 better and allow great piston speed than the 2.5.....or is the 2.7 just rated at a higher redline "less conservatively" than the 2.5? Sure this has been covered, just have not come across it.

Question being does the 2.7 really have greater RPM capability over the 2.5 or is it a spec illusion?

[pothole]

Originally Posted by southernstar

Pothole, I thought we were talking about comparisons as between 986 Boxsters, not with respect to the 981. I tend to agree about some features on the new 981(such as electric steering and stop/start technology), as being primarily for the purpose of improved fuel consumption rather than performance. As to fuel efficiency in the 986, I checked the brochures that I have at home for the 1999 2.5 and the 2000 2.7 and 3.2 and nowhere is improved fuel efficiency mentioned, whereas the improved performance is. I agree that high-reving 'peaky' engines should be geared so as to have their engines typically running at higher revs; however, the 2.7 was actually less peaky than the 2.5 - i.e., the torque curve was more flat in the sense that it had a greater percentage of peak torque available down low in the rev range than the 2.5. Of course, this is exactly what you would expect with the increase in stroke in the 2.7 over the 2.5. This is all part of matching the engine to the gear ratios and, while I have no doubt that the gear ratios in the 2.5 are ideal for that engine, I also believe that the same is true for the 2.7 and 3.2 engines.

The higher rev limit does contribute to higher speeds in each gear - increases that are greater than one would expect from gear ratios alone. As I have already said, that is a real boon in the cut and thrust of driving around town as well as for autocross, where one need not shift out of second gear (unless the maximum speed on the course exceeds 65 MPH, which is pretty rare in my experience).

Brad

Dude, what on earth are you talking about? Where did I mention the 981 in my last post? I was talking about swapping gearboxes over, you can't possibly think I meant putting an early 986 box in a 981, can you?!

Forget the marketing bumpf. The taller gearing in the 2.7 was for refinement and efficiency, not to make the car better for enthusiast drivers. The end.

Companies put all kinds of "sporty" bull**************** in material for all kinds of cars, most of which aren't even 1/100th as sporty as a Boxster. But they still make efficiency a priority. Blame human psychology. When people are reading the marketing bull****************, they want to read about sportiness. Then they look at the MPG numbers and gag on them if they're too high. So they have to engineer in better MPG within reason. That's life.

As for the gearing helping in "cut and thrust driving in town," sorry but gimme a break. And finally autocross? Sorry again, but **************** that. OK, if you care about autocross it may be a benefit. So that's great. For everyone else, it's utterly irrelevant.

The gearing in ALL of these cars is a compromise balancing off several factors, some of which you will care about others you won't. I'm not that bothered about MPG, so up to a point I'd want lowering gearing. However, I wouldn't want it crazy low as that makes the car tiresome for long journeys.

Thus for a 2.7, I'd want the 2.5 gearing. To recap, there's no such thing as perfect gearing. It's always a compromise. And for my needs the 2.7 gearing is too compromised in favour of MPG and cruising refinement.

[pothole]

Originally Posted by recycledsixtie

Do I sense a subjective bias here by the owners of the 2.5 motors?
If they sold them and owned 3.2 motors then they would be the best in the world!

Of late there hasn't been much bias towards the 2.5, we've been talking about gearing.

I own a 2.5, but I suspect my perfect 986 would be a 2.7 with gearing from the 2.5. hardly biased in favour of the 2.5 engine.

[pothole]

Originally Posted by runjmc2

My understanding is the 2.7 is not a bored 2.5, rather it has a longer stroke (3.07in vs. 2.83in). All things being equal the shorter stroke 2.5 would have a lower piston speed (FPS) and allow for a higher red line than the 2.7.

Are all things "not equal" in this comparison, e.g. the design/materials on the crank/etc of the 2.7 better and allow great piston speed than the 2.5.....or is the 2.7 just rated at a higher redline "less conservatively" than the 2.5? Sure this has been covered, just have not come across it.

Question being does the 2.7 really have greater RPM capability over the 2.5 or is it a spec illusion?

Good questions. Yes, the 2.5 is shorter stroke. But it's a fact that the 2.7 has a higher rev limiter and produces peak power higher. You could, of course, fairly easily tweak the 2.7 with a lower rev limiter and to produce peak power lower down.

God knows if the 2.7 has a better crank, I doubt there are dramatic engineering differences. The difference in peak revs isn't huge anyway.

Neither engine is terribly stressed, if you ask me.

[southernstar]

Pothole, you are suggesting (without any evidence) that Porsche changed the gearing on the 2.7 to improve fuel economy at the expense of performance. My point about the 981 was that, yes I agree that Porsche has made some changes in the Boxster for the purpose of improved fuel economy - e.g., electric steering and start/stop technology in its most recent model, and they have acknowledged that this was the principle reason for those changes. But I thought we were talking about changes made to the 986 Boxster series, where they made no such claim about the changed gearing that came with the introduction of the 2.7.

What is interesting about the gear ratios on the 2.5 as opposed to the 2.7 is that, while the ratios for the the first three gears are identical, the ratios for fourth and fifth gear are actually closer in the 2.7 than the 2.5. I assume you will agree that for the purpose of performance driving, a close-ratio gearbox is generally considered better (after a shift, it enables one to keep the engine RPM's in the sweet spot in the middle of the power band). Put in practice, a shift into fourth from third, or fifth from fourth in the 2.7 will drop the rpm's less than in the 2.5.

It is obvious that we will never agree on this point and that's fine. You say that Porsche changed the gearing solely for the purpose of improving fuel economy. You say that in spite of the fact that Porsche never made such claims and indeed, you offer no fuel consumption figures to prove that there was any such improvement. I say that Porsche introduced that 2.7 and 3.2 in order to improve performance and thereby address the biggest criticism of the 2.5 - that it was lacking in power, torque and flexibility. I am saying that Porsche altered the gearing in order to match and optimize it with the improved peak torque and horsepower as well as the flatter torque and horsepower curves that came with the increased displacement and improved fuel injection in the new engine.

While it is unclear whether Porsche improved fuel efficiency with the 2.7 (and I suspect they did not), it is clear from Porsche's own figures and from comtemporary tests that it did improve performance over the 2.5.

Cheers!

Brad

[paintboy]

Experts like Pete Townshend, Tim Curry and Paul Williams all agree that the 2.5 is the engine to own. Many 911's have had their new motors replaced with 2.5s that have upwards of 100k miles on the clock. A spokesman for NASA, B. J. Smegma, stated that if the 2.5 was available in the 1960s, it would have powered the Apollo rockets into space, instead of those silly American made Saturn 5 things. And had 2.5 been available to the German war machine in WWII, who knows how things would have turned out....a Tiger tank doing 0-60 in six seconds would have been unstoppable.....

[southernstar]

Thanks Paintboy - you have brought us back to earth! While much less interesting and fun than contemplating the world order if the Germans had the 2.5 in WWII, I just checked the EPA site re: the fuel economy numbers for the 1999 2.5 versus the 2000 2.7:

1999 Boxster 2.5 manual: 17 MPG city, 24 MPG HIghway, 20 MPG combined
2000 Boxster 2.7 manual: 17 MPG city, 25 MPG Highway, 20 MPG combined

Wow, if Porsche changed the gearing on the 2.7 for the purpose of improved fuel economy, they failed dismally! The combined number is identical and the 1 MPG improvement on the highway cycle could probably be explained by anything from varainces in individual cars to the improved fuel injectioin system. Even worse, while trying to improve fuel economy at the expense of performance, they actually by their own admission in the brochures (and as confirmed by contemporary tests) IMPROVED performance. Porsche got it all wrong!

Brad

[recycledsixtie]

I have not read all the responses in this forum but I understand that the 2.7 Boxster base(2001) does 0-60mph(0-100kph) in 6.5 seconds. So what is reported time for the 2.5 litre engine?

[southernstar]

Porsche 0-60 Times & Porsche Quarter Mile Times | Porsche 911 Carrera 0-60, 944 Turbo, GT2, Boxster S, Cayman R, GT3 and Porsche Cayenne 0 to 60 stats!

The above site posts 0-60 and 1/4 mile times for various cars, apparently based upon averages from contemporary magazine tests. They show the following:

1999 Boxster 2.5: 0-60 6.3 seconds, 1/4 mile 14.8 seconds
2000 Boxster 2.7: 0-60 6.0 seconds, 1/4 mile 14.5 seconds

http://www.howstuffworks.com/porsche-boxster-history4.htm

The following is a quote from the above web page in connection with 0-60 times:

"Porsche pegged the 2000 base Boxster at 6.4 seconds in the benchmark 0-60 dash, a modest .3 seconds up on the 2.5 litre original. The real-world time was probably more like 5.9...."

The actual times vary, although it would seem clear that the difference in 0-60 times is at least .3 seconds as between the 2000 2.7 and the 1999 2.5. I don't have my brochures here with me (and I don't have one for a 2001 Base which was a bit heavier than the 2000 due to the lined top and cupholders), but the 6.5 second figure you refer to may reflect 0-100 kph (which is actually a little over 62 MPH), or it may have increased slightly due to the additional weight.


Brad

[recycledsixtie]

Cf you are always welcome here. Anything to do with Boxster is good and who knows I might be interested in a Cayman/ newer Boxster in a few years.

[southernstar]

Recycledsixtie, does that refer to your age or the 'sixties' (where as has been said, if you can remember them you weren't there)? Just asking cuz you posted this on the wrong thread - lol!

Cheers!

Brad

[paintboy]

I did not realize the Boxster was a muscle car....better to be able to keep right foot buried in the corners. Straight line speed is not what these cars are about. If you don't do twisties, you are waisting a great car.

[recycledsixtie]

Originally Posted by southernstar

Recycledsixtie, does that refer to your age or the 'sixties' (where as has been said, if you can remember them you weren't there)? Just asking cuz you posted this on the wrong thread - lol!

Cheers!

Brad

Thanx Brad!