2.2E vs. 2.4E Performance

[Halm]

We got lucky yesterday with the weather and our Carolina Mountain Drive. The attendance was good and everyone had a great time. As we started a short leg of the route, Tom Morgan and I swapped cars to see the difference between his ’73 E coupe and my ’70 E targa. Both cars are basically stock, including MFI.

I was stunned at the “seat of the pants” difference between the 2 engines. His 2.4 motor was clearly stronger and more responsive through the entire rev range. It also simply felt tighter and more composed. Looking at the specs, he has 10 more HP and 15 more foot-pounds of torque. Also my car is about 45 pounds heavier. (As per 911 E Registry). Also FWIW, my engine was rebuilt (by PO) approximately 12,000 miles ago by one of the more infamous west coast shops.

Should this difference be so noticeable in back to back drives? It is so dramatic that I am thinking about a full rebuild later this spring. Anyone else had a chance to do a back to back comparison between similar models? Or is this simply a normal experience with a smaller motor in a heavier car?

[Tim Walsh]

there was a definite difference in the two but I thought it was just drivers. Tom does have more meat on his tires though so that might be it. Any other mods between the two?

[tryan]

thanks again for the fun hal. my opinion but the longer stroke gives a broader torque curve which seems faster on the roads we took. was toms the fresh silver car with dual outs? if so, the exhaust might kick the hp up.

as you said, your piston might not be giving you optimum compression. the price of the 2.4e pistons will make you jump right on up to s real quick. you might win the 10 bucks. i'm thinking about the white beast.

[Bobboloo]

There's no replacement for displacement. The horsepower is no big deal but the torque is the difference in the motors. So the 2.4E makes a nicer street motor in my opinion. On the track at high RPM's you wouldn't expect for there to be that much difference.

I would also think that the condition of the rebuild also has to do with the responsiveness of the motor you mention. If you decide to rebuild down the road you might look at stroking your motor.

I've compared the differences between a 2.4E MFI and a 2.7S CIS. HP was not much different but the torque was. The 2.7 had power on tap. The 2.4 was like awakening the giant, when you hit 5000 RPMS it felt as strong as the 2.7 and sounded way cooler. Now you see why the 2.7RS is so popular. It's the best of both worlds.

[RallyJon]

Looking at the specs, he has 10 more HP and 15 more foot-pounds of torque.

Is that right? Is it a Euro 2.4E? Based on Bruce Anderson's numbers (which may be wrong--I don't know) the U.S. got the anemic 911/51 in '72-73 while the rest of the world got the "good" 2.4E. Here are the specs:

USA '70-71E 911/01 9.1:1 155HP@6200/141lb-ft@4500
USA '72-73E 911/51 7.5:1 140HP@5600/148lb-ft@4000
ROW '72-73E 911/52 8.0:1 165HP@6200/151lb-ft@4500

All are MFI. Sounds to me like the 2.2 would be a lot more fun than the USA spec 2.4. I have a 911/51 with Webers and headers in my car, and it's not what I would call fast.

[Tim Walsh]

I'm pretty sure the US got the 911/52 engine in the E that would make 165HP@6200 and the T got the 911/51 which makes 140@ 5600. The Euro version of the T got zenith carbs which was even worse, 130HP@5600.

[Halm]

Actually, the RED BOOk says 141 foot-pounds for the '70 and 151 foot-pounds for the '73. That is why I quoted the 911 E Registry numbers. They were obviously higher.

[Tim Walsh]

that's exactly what's in BA's book

[RallyJon]

OK, here's my reference point: I have an engine in my '71E that came out of a '73E. It has a green shroud and says 911/51.

So, if someone has an original, known-to-be U.S. spec engine that says 911/52 on it, that would clear things up...

I guess it wouldn't be the first time that BA was wrong.

[Tim Walsh]

hmm.. where's racemor when you need him..

RallyJon whats the serial # on your engine?

[racemor]

Sorry, I've been watching my tape of the Sebring 12 Hour race from yesterday.

The serial number on my motor is 6230038, green shroud, still the original motor according to the Certificate of Authenticity. Where do I find the 911/51 or 911/52 number? There is about 25,000 miles and 20+ years since the rebuild, which my records show was a "basic 911E overhaul" with Mahle p&c by Frontier Automotive in Flora, Illinois. It runs very rich, could be a little power there (?).

From Bruce Anderson's Early 911 Market Update, Excellence, May 2002:

"For 1970 the 911 engines were increased to 2.2 liters (2195 cc)...The 2.2-liter 911T produced 125 hp, the 911E made 155 hp and the 911S offered 180 hp."

"The biggest news for 1972 was that the 911 had yet another displacement increase - to 2.4-liters (2341 cc). The 911T now had 140 hp, the 911E boasted 160 hp and the 911S was up to 190 hp."

He does not list any changes in the '73 model (other than the CIS change to the T model of course). He also does not list torque specs here.

Peter Morgan's Original Porsche 911 book says:
1970 911E, 155 DIN bhp@6200, 191 nm@4500 (not ft. lbs.!!)
1973 911E, 165 DIN bhp@6300, 206 nm@4500

Now, the brochure for 1973 says:
911E, 165 DIN HP (157 SAE net HP) at 6200 rpm - 21 mkg (147 ft. lbs) at 4500 rpm.
The original owners manual says the same thing. The difference in DIN versus SAE may cause some of the confusion.

I guess only some dyno runs can say for sure. The only mod to my motor is that the exhaust recirculation tubes are gone, just uses the short elbow into the airbox. There was a 3 month gap in driving from the 1-out exhaust to the 2-out so I can't compare back-to-back but I don't think it would have made that much difference. But there was deinitely a noticable difference in our cars Hal, just can't tell you why. I can say that I wish my clutch was a smooth as yours though. After driving them both, as I was telling Tim, it is amazing how different such similar cars can be. Thanks for letting me try it out!!

[Plays with cars]

I think Tryan's onto it. The broader torque curve will be noticable by the seat of the pants and will make the car faster in public driving situations where you can't always be up in the power curve of the 2.2. In Tom's last post he noted that the 2.4 has a dual out sport muffler, I wonder how much this is contributing to the difference between the two. In the "Porsche 911 Performance Handbook" on page 141 there is a chart with horsepower curves for a 2.4S motor with and without a sport muffler. Presumably no other changes and the S motor picked up about 20hp. If the E motor responds similary the sport muffler then that could also be what you're feeling.

[Scott Clarke]

The E motor will not respond to a dual outlet muffler like an S does. I have seen posts that talk about a flat spot that occurs in Es with MFI when a 2 out is used. I had an Abarth muffler on mine (four outlets), and found that the car's performance was improved significantly when I installed a stock, one-outlet item. It is my understanding that the S MFI space cam likes two outlets, and the E one.

[masraum]

I think they've probably hit the nail on the head with the 2.4 having the fatter torque curve. It's like the comparison between the Z4 and Boxster in the latest Excellence. They say the Z4 feels faster because it has a really fat torque curve, but the acceleration numbers still work out to be very close.

[RichMason]

My car was positively anemic in comparison with Tom's in the few 10-60+ sprints that we did. My car did improve, in my novice view, in the curvier sections of the ride where I was able to leave the car in second and third and keep the engine above 4-5k rpm. I was beating the rev limiter to death in the final run to the reservoir but i felt like it was the only way to make power. Any advantage from Tom's lower profile tires in acceleration? Tom, how does the 911 compare to your Miata in performance ?

[Tim Walsh]

I'm going to try and give the porsche another try at starting it today. If it goes well You're welcome to drive my 2.4T and see the difference. It will be interesting to see the fatter torque curve of the T with less overall HP compared to the 2.0, 2.2 and 2.4 Es

[Halm]

Tim, Might be up your way next week. Paul has found a 2.5 short stoke hot rod motor we are going to go look at.

[tryan]

those 40 to 100 sprints where the ones that tickled my jollies . we always want more POWER. enough is never enough unless you just borrow someone elses car.

the best performance on any car is between peak torque and peak horsepower. below peak torque, you are 'lugging' the motor and above peak hp is just that. 4-5 k sound about right for an e motor.

you are in violation of the three vowel rule when you mention m**ta. twitchy little buggers.


just another tom

[racemor]

Rich, the tires may make a difference if you were really comparing times. But the difference we felt was more in the feel of the motor. Mine just responds quicker to the throttle and you can feel the pull of the motor much more through the midrange and down low. The Sherrif's car behind us kept me from trying any high rpm stuff.

And yes, my car is much stronger than the Miata, although I think the Miata may feel as strong or maybe a little better than the 2.2 did that day. The Miata's handling is very different and a lot quicker to respond on tight stuff, like autocrosses I can turn quicker autocross time with the Miata than I can with the 911.

Before anyone argues with this, I am comparing stock trim to stock trim. When I get the 911 set up with good shocks, torsion bars and sticky rubber it will be the quicker car.

[MFAFF]

Its all torque....
The 2.4E's curve allows for higher torque lower down with associated 'grunt'.

When the 2.4 range was launched it the comparison was made between the 2.4E and the 2.2S..not E.
Certainly over here the 2.4E is a more driveable car than the 2.2E or S becauase it has more accessible torque.

Above 4500 they should not be separated by much but the feel of getting there will be different.

I'll have to look at the torque charts in the handbook to see the fatter spread, anybody got the 2.2E chart handy.....?

But either is a blast. Good luck on the mountains..