Engine Quiz!

[Adrian]

OK guys, I have been reading the posts on this site for a long time and have got the impression that most people don't know that much about Porsche Performance upgrades. Therefore, I have devised this quick quiz. Given the following engine, what would the resulting power output be?

3.0L SC case
9.8:1 Pistons
911S cams
Weber 40IDA-3c carbs w/ 36mm Venturi
SSI exhaust w/ dual pipe sport muffler
Stock everything else

This is your chance to show that you know your stuff. Answer will be posted soon. This should be fun .

[Saffs]

OK guys, I have been reading the posts on this site for a long time and have got the impression that most people don't know that much about Porsche Performance upgrades.

That's not devastatingly surprising. I certainly don't know, but it's a general 911 Forum not Porsche Performance Upgrades Forum, so I don't think we're all going to be experts, are we?
But I bet there's one or two.....
Anthony

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'75 911S Targa
'81 BMW Alpina C1 2.3

[orbmedia]

I hardly think you'll get a definitive answer on this. It's not like there's a formula or anything.

[Adrian]

I just want to have some fun. Also, a friend which is a mechanic at a very reputable Porsche repair shop in Miami is building this engine. He is claiming an outrageous number for the HP. I want to see if others see this as the ultimate engine combo as he does.

[orbmedia]

I'll guess 230.

[Adrian]

<>

Actually, there are a couple formulas that can be used. I'll give credit to anyone within 5hp.

[3liter914-6]

Ok, I'll venture a guess.

Let's say 225HP. You're not providing a huge CR increase going to 9.8:1, and the SSI's and Webers dyno @ ~210hp in the 911 Handbook, so the only thing that's really a ? is how much power will the "S" cams get you. 225hp seems reasonable to me. A lot more power could be found if you futzed with the heads, but you don't mention those. It's difficult to make good conjectures unless you've been in the actual motor end of the industry building hi-po motors for a while, there seems to be a definite lack of performance proof in the Porsche world. I love pouring over dyno charts and seeing 1/4 mile times, but not too many people have the hard data for their setup. I'm kinda sick of all the local 3.2 carrera owners making up numbers, one guy thinks he's got 250hp from just his K&N intake. He's thinking about getting a muffler, should be good for almost 275 . So do you know the magic # yet, or this is just the setup your mechanic recommends for getting XXXhp?

EDIT: Orb guessed 230 while I was composing this, so I scaled it back to 225

Originally posted by Adrian:
OK guys, I have been reading the posts on this site for a long time and have got the impression that most people don't know that much about Porsche Performance upgrades. Therefore, I have devised this quick quiz. Given the following engine, what would the resulting power output be?

3.0L SC case
9.8:1 Pistons
911S cams
Weber 40IDA-3c carbs w/ 36mm Venturi
SSI exhaust w/ dual pipe sport muffler
Stock everything else

This is your chance to show that you know your stuff. Answer will be posted soon. This should be fun .

[This message has been edited by 3liter914-6 (edited 06-03-2001).]

[Early_S_Man]

You didn't say what crank, pistons, or displacement the engine will have, but assuming a 3.0 ...

Formulas don't work too well with 3 liter 911 engines, as the factory engineers found out in 1974! Based on the experience they had building the RS 3.0 engine, the answer is 220 hp, which is what the MFI production 3.0 had with identical spec (230 hp DIN) to what you cited ... less 10 hp for going with Webers!

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Warren Hall
1973 911S Targa

[3liter914-6]

How 'bout whichever guess is closest without going over. "I'll bid 1hp, Bob..."

Originally posted by Adrian:
<>

Actually, there are a couple formulas that can be used. I'll give credit to anyone within 5hp.

[3liter914-6]

Oh, and "Please control the pet population, have your pet spayed or neutered..."

[This message has been edited by 3liter914-6 (edited 06-03-2001).]

[Adrian]

No way, I'll never neuter my Weimaraners.

[Adrian]

The answer is 235hp. I have built 3 such engines and all three were dyno'd at 235 give or take 1hp. I think the reason the factory 3.0RS is at 230 is that the intake ports are smaller than those of the SC's (39mm intake). My friend the Mechanic claims he got 300hp from this combo. Claiming that 15hp alone came from adjusting the valves and intalling double springs. He must be one of those people that believe that a chip gives you 25hp. (This is only true on 928S4s).

[Superman]

I'n no expert, but I'm getting the feeling that SC-based performance engines can be pretty exciting. Some folks seem to prefer this over performance engines based on the Carrera 3.2. Randy built a 281-horse engine that, unless I miss my guess, is pretty exciting power. Of course, he used fatter pistons (3.2), 3.2 heads, etc., but apparently 325 horses is possible using SC cases.

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'83 SC

[orbmedia]

Adrian,

Thanks for the prize but I cannot accept one of those engines at this time, I have too many projects. Please give my prize to some other guy looking for one of these nice powerplants.

[Adrian]

In that case I guess I'll have to install it. Into yet another of my RS replica project cars. Cheers!

[paulhagedorn]

Ooh, I'll take, I'll take!!! Haha. Pretty please. I didn't see the post and didn't get to guess.

[cegerer]

OK, so what is the magic formula for calculating HP?

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1971 911T - 2.5L Big Bore

[kumma]

cegerer - don't you know that you just add 10hp to whatever a friend claims to have.

Craig

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Craig 73T in many pieces

[Adrian]

The formulas are not that simple, but here is a summary. The lobe profile gives you possible engine peak power range (6200-6600rpm for S cams) Then you determine where the bottle neck is in the system by using some fluid dynamics equations, once you find the lowest flowing region you use that flow rate to calculate the horsepower. The same combination above with ported heads and a race header would have a maximun power potential of 255hp , but the stoch heads and SSI exhaust don't flow that high .