cegerer 2.5T

[724doorE]

Look in Bruce Andersons P-car handbook at the table of engine designations. P raced the 2.5 with a66 or 70.4mm crank. With the 66 they used 89mm bore pistons to keep under 2.5--yours is just over 2.5 with the rS pistons. They used 906 cams, 41mm ports, 10.3:1 comp and weber 46 IDA carbs --The factory claimed 275 hp at 8000rpm. Thats what I wnat! not 250. I would suspect that your 2.5 is very driveable and not peaky at all like the racing engine. I was wondering how you liked the combo. Bruce A. said in his book that the resulting comp was to low to give good results. That idea evidently is open to opinion. Youve got one how do you like it? Do you know if they did anything to up the comp ratio a little bit?

Dennis H.

72 911E
NW Indiana

[jluetjen]

Here's an interesting tidbit about the 2.5's that I found while reading "Porsche 911, R-RS-RSR" by John Starkey.

" ... To take complete advantage of the 2.5 litre class limit, Porsche supplied several sets of components for customers who wanted engiens of this size. In fact, Porsche built two prototype 2.5 liter engines of differing stroke/bore combinations due to a problem they encountered with the first design.

The first design took advantage of the "E" production variant (AKA: 2.4 liter motors) having piston stroke increased to 70.4 mm (previously 66 mm) in conjunction with a bore increased to 86.7 mm: the result was a cubic capacity (2494 cc) at the class limit. Otherwise the 2.5's specifications were as the 2.4 liter unit. In its new size, the engine developed 275 bhap at 7900 rpm and 196 lbs/ft of torque at 6200 RPM.

The problem with the first 2.5 liter engine was that it tended to loosen its flywheel bolts, or in extreme cases break its crankshaft. There was little doubt at the factory that this was due to the longer stroke now being used and so some engines were built using the previous stroke of 66 mm whilst employing "Nikasil" cylinders with a bore of 89 mm. This resulted in the same power and torque figures as the long-stroke engine without its fagility"

I'm suspect that Roland may have even more behind-the-scene history on this. It's an interesting proof that (all other things being equal and reasonably optomised) that changing the bore-stroke ratio doesn't change the HP or torque figures. Both are a function of the amount of air pumped, which is 1.25 liters per rev. Anyhow, I'm sure that Porsche figured the problem out.

PS: Speedvision was rebroadcasting the Goodwood Speed event (Hill-climb) yesterday and they showed one of these 911ST's running the hill. The car seemed to be an absolute Rocket (and rev'd like it too!), but then the driver stuffed it. He said afterwards that "The car just started turning faster then I could"

[cegerer]

Well, there are the rare racing 2.5's with dual plugs, etc. and there are those - like mine - that are normal 2.2L T-motors converted to 2.5L. In the MM Piston Thread Otto referred to a 251HP 2.5L. He seemed to be talking about the normal single-plug low-compression T-motor, like mine. Except he squeezed an extra 50-60 HP out of it!!!!!!!! I'm not doubting it, but I'd like to know how. Otto?

As far as my existing motor, it is nearly identical to what BA recommends in the Perf. Handbook. It drives very much like an early S motor. Comes on like gangbusters at 5500 RPM's or so and pulls strongly to 7300 RPM. It may lack low-end torque, but I absolutely love high-revving peaky motors like this. It 'feels' very much like a race car. The only car I've ever 'raced' against was a friend's 928S Euro. I easily pulled away from him from around 40MPH all the way to 120MPH or so, then we ran out of road. I was still in 4th gear. 250HP would be absolutely incredible. -- Curt

[Early_S_Man]

The 70.4 mm crank breakage problem was solved within a year or so of the debut of the long-stroke 2.5's ... a specially-radiused version that required special bearings was used on all 2.8 and 3.0 RSR's!

That problem discovered in the long-stroke2.5 race engine is why BA recommends that stock 70.4 mm cranks be limited to the 7500-7800 rpm range for best durability!

[curtisaa]

Does your E air..if so do you have 2 condensers. 1 on the deck lid grill and another under the left rear 1/4 panel.

[724doorE]

Curt yes my E does, did, have air--factory air. Yes I think it had two coils, one under the engine lid and the other under the front spoiler. Don't know/remember if it was two condensers or the condenser and the evaporator. Why?

Dennis H.

72 911E

[curtisaa]

I bought this 73 E and we put it on a lift this morning, to check thoroughly( for rust) and I noticed a cooler under the rear fender. My 73 S ( no longer own) had Behr Air, which I believe this E has also. I just don't remember seeing this 2nd condenser on my other Pcar.

[Fritz]

Hey Curtis & Dennis

I have a 73E and just pulled off the dealer installed AC. There were the large one under the engine grill, one in the left 1/4 panel (totally full of mud and with a busted up fan on top, and one in the front passenger fender.

What part of Pasadena are you in Curtis? I used to live up along the Altadena border east of Lake.

[curtisaa]

OK...the one under the driver front fender was an oil cooler right??

I live off Linda Vista...next to the Rose Bowl and very close to Pasadena Art College.

I just sent for the birth certificate from Porsche. The car has S options, front valance, brakes, sport seats, and is in very owiginal condition. The only quirk is that it was repainted Peru red from the original silver. NO RUST and 104K miles. Not bad....

For now, a nice driver...we'll see

[Fritz]

Hi Curtis,

No, the item in the passenger front fender is for the ac system. I have no regerets about removing the ac, I want to run lines in the same place for an oil cooler.

Lucky you, no rust. My 73E has it pretty bad, I posted some pics about a month ago, but it is getting rustoration.

Enjoy your drives up Angeles Crest. My in-laws are in La Canada up off Angeles Crest....so I hope to see your E go by sometime.