924Board.org

[dvarholy]

I think i have a set of 931 pistons with rings around here somewhere. They were for my '80 931 (7.5/1 compression). I can't remember what bore size they were. I thought that all 931 engines are interferance. There are several companies that custom make forged pistons at decent prices.

[Rick MacLaren]

Gohim: Nope. Not 150 HP.

As I said earlier:

ENGINE

Number of cylinders: 4
Bore: 3.94 in. (100mm)
Stroke: 3.11 in. (78.9mm)
Displacement: 151 cu. in. (2479cc)
Compression ratio: 9.5:1
H.P. SAE net (kW): 143(105)
at rpm: 5500
Max torque SAE net ft. lbs (Nm): 137.1(185.9)
at rpm: 3000
Maximum rpm: 6500
Fuel Requirement: Lead-free only (92RON)
Engine design: Watercooled, 4-cylinder in-line, front mounted
Crankcase, cylinders: Light alloy, two part
Cylinder head: Light alloy
Valve placement: Overhead valves
Valve train: Overhead camshaft, hydraulic lifters
Camshaft drive: Spur belt drive
Crankshaft: Forged, 5 main bearings
Engine lubrication: Pressure lubrication, full flow oil filter
Fuel supply: 1 electric fuel pump
Fuel/Air mixture: Electronic Fuel Injection (AFC), Digital Motor Electronic (DME)

A 931 is still faster. And 600 lbs lighter.

Cheers



Rick

[Cbass]

And a lot cheaper to run. It has few drawbacks, many of them easily fixed. Have to rebuild the turbo? Fine, get a water cooled electronically controlled turbo, and tie the wastegate control to an adjustable pressure switch.

Save your pennies for an ECU, get a dozen people to save up with you, buy in quantity. You'll also save on the software that way. Throw in a 944 fuel rail, and you've got an EFI 931 with electronic boost control. Get a DIS and you have a motor capable of 300hp. Of course, you should do a complete rebuild and PROPER turbo build at this point.

[gohim]

Your wrong Rick. I don't know where you get your numbers from, but they definitely are not from any Porsche Published Specifications.

According to my Porsche Technical Specification Books, and the Owners Manuals from my 81 924, and 87 924S, the numbers that you spouted are wrong.

This is what I get from the Official Published Porsche Numbers:

You have to make sure that you are comparing apples to apples. These are the DIN hp numbers for all of the models listed.

US Models

80-82 924 115hp 2612lbs
80 924T 150hp 2779lbs
81-82 924T 156hp 2779lbs
83-87 944 150hp 2778lbs (1987)
87 924S 150hp 2734lbs
88 924S 160hp 2734lbs
88 944 160hp 2844lbs

So a 87 924S has 6 less hp, and weighs 45lbs less than a 81-82 924T, with a flatter torque curve.

Or, a 88 924S has 4 hp more, and weighs 45lbs less than a 81-81 924T, with a flatter torque curve.

According to Porsche, a 87 924S takes 8.3 seconds to go 0-60 mph, a 88 924S takes 8.0 seconds, and a 81-82 924T takes 9.3 seconds.

Running 1 km takes 30.1 seconds in a 87 924S, 29.5 seconds in a 88 924S, and 29.8 seconds in a 81-82 924T.

So, according to Porsche, any model year 924S is faster off the line than the best 924T model years. But the 924T will beat the 87 924S to 1 km, and lose to the 88 924S.

And the 924T IS NOT 600lbs lighter than the 924S. It weighs 45lbs more.

I have owned, and driven 924s since 1981. My first was an early US 77 model (production date 02-76). It had a european head (as did many of the early US models, and more hp than my 81 924 has. It was faster, in a straight line and around corners than my 81 is, even with the 77's four speed transmission.

It took me a long time to decide to try a 944 series engine, because of the extra maintenance requirements. But I am collectiong the parts to build a 160hp engine for my 924S (has been waiting for an engine since I bought it over 2 years ago).

I am looking forward to driving a car with enough hp to cruise up hills without downshifting like crazy.

[Rick MacLaren]

Gohim: Wanna race me and find out?

Gohim, first of all, you said in your previous post that the 924T horsepower was LESS than the 944, but NOW you're showing it's the SAME horsepower. Which post should we read? The lack of consistency from one post to another is confusing.

Here's a QUOTE from the PORSCHE site showing the STOCK EURO 931 with MORE HP than the STOCK EURO 944. APPLES COMPARED TO APPLES. Would that be compelling evidence for you, or is the source not credible enough? Check it yourself:

http://www.us.porsche.com/english/events/clubs/news/cw0400/porsche924.htm

In November 1978, Porsche developed this concept further to create the 924 Turbo, the engine power and driving performance of which caused a great stir. The turbocharged engine achieved 170 bhp (125 kW) even with the displacement unchanged at two litres. This time, acceleration from 0 to 100 km/h was reached in just 7.8 seconds, and the top speed certainly exceeded the stated figure of 225 km/h (approx. 141 mph). Of course, the tyres, running gear and brakes had been adapted to suit this car's capabilities. From the outside, the 924 Turbo could be distinguished from the standard model by additional air inlet slots above the bumper, the roughly T-shaped opening in the engine compartment lid for removing heat and a modest spoiler below the rear window, added to the 924 at a later stage as part of a model update. From Model Year 1981, bypass-valve boost pressure control provided the turbo engine with a fully electronic, boost-pressure-dependent ignition, which increased the output to 177 bhp (130 kW) whilst simultaneously reducing fuel consumption.
Pure sports cars derived from this model were the 924 Carrera GT with intercooling and 210 bhp in 1980, clearly distinguishable through its wider wings and additional cooling-air scoop on the engine compartment lid, and the 924 Carrera GTS with 245 bhp in 1981.

The new class: the Porsche 944

The engineers at the Porsche Development Centre in Weissach had an ulterior motive in designing the V8 alloy engine for the large 928. They had allowed for the V8 to be halved to a straight V4, and so drive future developments on the 924. And hence the beefy 2.5l, 163 bhp (120 kW) engine of the 944 was born.

Compelling?

Check the link, I think you'll find it credible:

http://www.us.porsche.com/english/events/clubs/news/cw0400/porsche924.htm

Besides, if the stock 944 or 924S is faster than the stock 931, why do they all suck my exhaust?

And please, Gohim, use the derogatory 'spout' sparingly - it's an especially ugly term to use, and particularly ironic when you're facts are so easily contradicted by a visit to the Porsche AG website.

LOL




[ This Message was edited by: Rick MacLaren on 2002-05-04 04:06 ]

[gohim]

Are you in Europe with a European Spec 931?
I know you aren't quoting from the owner's manuals of your cars, so you really have no first hand experience with what you are talking about.

If not, and you have a US spec model, the numbers that I wrote are correct.

A friend of mine has a 81 924T which he bought new in 81. The car only has 12K miles on it now. I can tell you that both of my 924s are faster off the line then his turbo, and his turbo will pass both of my 924s in a straight line race after the turbo spools up, and he makes up my off-the-line lead. Up driving in the hills, downhill, he can't not pass me, the turbo doesn't have the traction to use all of it's power, or spool up in time for the straights.

Like I said, apples to apples.

You're quoting numbers from an early Porsche Press release with European Spec engines which tradionally have more hp than US versions because of smog controls. Example: European 924s were spec at 125hp, and early 924s 95hp. US 80 924T were spec at 143, in 81 the spec was 154hp. These were not the DIN numbers. If you had the owners manual for your 931, you would see that you are wrong are about your engine's power output. US spec 924T are not 177hp.

You wanna race? How mature is that? But if you want to race, and you are 18 years of age, with car insurance and a driver's license, come one down. I don't hill race on a regular basis anymore because I consider it to be too dangerous, and becoming mature means learning that you aren't indestructable. But if you want to prove that you can't drive as well as I do, and your car doesn't run as well as mine does, I will drive my 81 924, or my 73 914 2.0. Both cars have less hp than your 931 (if you really have one at all), and I will beat you.

But bring it anyway. My choice of course, since it's your challenge, and you should have your life insurance paid up, incase you do something stupid, and end up paying the price.

There is more to an exhibition of speed and the results of a race, than the equipment used. The power output of the 931 and 924S is very close. But the fact is Turbo cars are harder to drive, because of the turbo lag, and the lower hp and torque at low rpm. On a curvy road course, with short straightaways, a NA car will have an advantage, because the turbo car will be in and out of the boost, and traction would be an issue.

You will lose.

[gohim]

Rick, I forgot to ask...

What about the 600lb weight advantage that you quoted for the 931 over the 924S?

Ready to addmit that you car doesn't weight 2100lbs?

[teo]

I have read this somewhere:

"In every man there's a younger person wondering what the heck happened."

Looks like you guys let them out for a little.

[Rick MacLaren]

Ok, well let me be clear: Gohim, I was pissed at your delivery of the term "spouting" - I think it's deliberately inflammatory, rude and personal. The fact that you possess a spec book, and feel insulted that I could challenge the 944's speed and dollar cost efficiency, is a testament only to your sensitivities - I wasn't slamming the 944, or you, just dispelling what I saw as myth. You can do the same, just please don't throw out disrespectful personal disses like 'spouting' into print if you expect friendliness and mutual respect.

Probably somewhere along this conversational path you've thought I've slammed the 924S. That isn't quite the case. I was answering the question about 944 versus 931: Which is cheaper (and I assume inherent in that question is Which gives the best bang for the buck?). I don't know what question you were answering, but maybe you can inform me. You seem more focused on the 924S...

[BTW: I apologise to everyone for being immature in challenging Gohim to a race. Still, I think there's some venue where our own cars should be compared. I've put up the money on mine to make it nice, so I'm willing to go for a "drive" with Gohim anytime - in fact, this summer I should be in the USA a lot].

Anyway, I cited facts that are pretty well known and accepted and I didn't think I'd gone so wildly off the map with my assessment. I have played around with 944's and they're not a faster car.

The best I can do is cite the Porsche website: it's a public space, made by the makers of our cars, devoted to presenting historical facts to people. And the 931, according to their site, is quicker. Smog pumps or no smog pumps.

Admittedly, I could be wrong about the '600 lbs' weight issue - I ballparked that figure based on my experience seeing light 924's I've seen weighed at racetracks, and I suppose heavy 944's. Evidence here, on these websites, between these two particular cars is less than 600, yet I've seen comparisons showing 240 (I believe) kg, and I think these depend on the options chosen. Admittedly, there's too much inherent variance in the weights of these cars to make weight terribly meaningful. Yet EVEN this US site that compares the 924 Turbo and the 944 show FEWER pounds per horsepower in the 924 Turbo.

Still, it's the same chassis as the 924 Turbo, with wider body panels, same doors, same (or heavier) hatch. How it did this without gaining weight is beyond my comprehension. Smog pumps or not.

So, based on facts like that, and my own experience with 944's, I'm pretty confident the horsepower in the 924 turbo exceeds in speed and efficiency the 944. So bring your 944 along. Let's see your monster 944 pass me as I 'spool up'... I'll pick a road somewhere between us and go for a nice drive.

[Gohim: I would prefer we correspond with real names - can you send me an email with your real name and we can begin corresponding about a drive?].

Rick

*Check out PCA weights. These links show the 944 with less pounds per horsepower.
http://vista.pca.org/stl/944.htm
http://vista.pca.org/stl/924turbo.htm
*Check out Autozine:
http://autozine.kyul.net/classic/924.htm

[ This Message was edited by: Rick MacLaren on 2002-05-04 11:26 ]

[friskynibbles]

i'm not going to take sides in this dispute - BUT i don't give a damn how much power a 924s has because i'm not interested in popping an engine from one in my 931. i was only interested in 944 engines. can somebody tell me how the 924s got into this discussion?

[dwak]

Because the 924S has a 'detuned' 944 2.5 litre engine in it and therefore forms a good comparison specimen.
dwak

[Cbass]

Ah, but it has the reinforced 944 frame, with it's 225 lbs of extra weight. The 944 motor is actually lighter than the 924 motor, I believe, being made of aluminum silica alloy.

The fact of the matter is, stock figures are about equal for these cars. However, you can add more boost to the 931, and make more power. You'll need to install an intercooler to add more boost, but that will only cost $200. A good mechanical boost controller, $150. $350 and you have 200hp.

[gohim]

Answers to Questions:

How did the 924S get into this discussion?

The discussion started with the question of what was cheaper to maintain the 931 or the 944?

The question really was which engine was cheaper to maintain? The 931 or 944. From there it degenerated into which engine was produces more power, and which car is faster, the 931 or 944. I suggested that a 924S is closer to the 931 than the 944 was, and that the 931 does not produce more power than the 944.

Porsche Marketing described the 924S engine as a detuned version of the 944 engine. Actually, 924S engine was the previous model year 150hp DIN 944 engine. The year the 924S was introduced, the 944 got a hp boost to 160hp DIN during the production run by raising the CR to 10.2 (vs 9.7 on the 924S) and a recalibrated DME box. The next model year (1988) the 924S was given the same pistons, and DME as the 97 944, fuel octane requirement was changed to 98 RON, same as the 944 from 91 RON for the 150hp engines, and the advertised hp was 160hp DIN for both models.

The 944 engine is actually heavier than the 924T engine according to Porsche the 944 engine weighs 166kg (365lbs) while the 924T engine weighs 165kg (363lbs), and the 924 engine weighs 142kg (312lbs).

I have no idea of why the 88 944 gained 65lbs over the previous year's car. I can say that the reason that the 944 did not gain much weight on the 931, is because of the introduction of more alloy parts on the 944. The alloy front crossmember, rear trailing arms, and brake parts made a tremendous weight difference, even though the wider tires and fenders were adding weight at the same time.

There can be no doubt that the least expensive of the three models to maintain is the 924NA. Without the 924T's turbo replacement, and the 944's cam, balance shaft belts, and water pump to replace every few years, the 924 is definitely the cheapest to run.

Whether the 924T, or the 944 engine is cheaper to keep would depend on how the 924T is driven, and whether new turbos, or rebuilt turbos are used, and how the 924T driver treats his/her engine. The 944 engine's expensive maintenance comes every 3 years or 30K miles. The 924T's turbo replacement comes between 15K and 50K miles. The labor is about the same, but the parts for the 924T will cost more.

[numbers]

Anybody who thinks a 931 is cheap to maintain hasn't owned one for very long.

[Rick MacLaren]

You're absolutely right, and it's true of all the Porsche. If we're not talking 'bang for the buck', and we're just talking straight out expenditures, then Frisky should just get a 924. Or a Honda.

Next up in cost, in my humble opinion, would be a 931* based only on the cost for a list of say 'regular maintenance' and 'restoration'* parts and based (again) only on my perusal of the Automotion and Performance Products catalog(s):

brakes
alternator
starter
steering assy's
wheel bearings
seals
tranny synchros
shocks/struts
etc.

* It all depends on what kind of shape the car is in when you get it.

Cheapest isn't the best question though, cause the user also wants performance, and that's why I translated his question into a "bang for the buck" question (rightly or wrongly). On that count too, though, I think the 931 has the best bang for the buck, and that's being said after I had a complete engine and tranny job done on my 931. I don't think you can replicate that kind of engine and tranny work on a 944 or 944 turbo for the same cash, as the parts for the "exact same work" will probably be more expensive.

We're estimating here the cost for parts, and making estimates of 'reliability' based on our own experience. Unfortunately, the driving manners of drivers varies a lot, and the degree to which your car needs maintenance is largely a function of how you drive it and how you treat it. That said, I'm skeptical of claims that a 944 is cheaper, or more reliable, and I'd put it back on your friend to support his case, because I think the evidence here is that there's reason to think his claim is suspect.