Menu toggle

how many ponies

Jon Darlington

Jon Darlington

New member
How many of you know the BHP output of your 912, jut a quick question as I am still looking to increase the output of my 912, so any specs/cool bits would be interesting. [8|]

Currently I am at 115 BHP at 5800 rpm, with the following spec.

912 crank (re-ground)
337s Norris cam
Shasta pistons (1720 cc)
Cast iron cylinders
Stock valves (head/valve matching)
Stock pushrods
Balance connecting rods (912)
Flywheel lighten and balanced
Solex cards
60mm velocity stacks
K& N filter
Standard exhaust (stainless F pipe + tailpipe)
Full flow oil system with exterior oil cooler (rear wheel arch)


Not sure how accurate the graph is I only had about 5 points to work with, shouldn't be to far out[&:]

Wu617982465.jpg
 
I've just dug out an old edition of Motor from July 1967 that has a road test of the 90 hp 912 under the title "Quick not fast". But does this mean we NEED more power?

In his book 'a Passion for Porsches', Denis Jenkinson notes: "It is often said that 'power corrupts, and absolute power corrupts absolutely' and that is certainly true as far as engines are concerned"...

...Too true. A quest for more power can however bring diminishing returns. It's a bit like going to a swish HiFi shop: you listen to the 500 pound amplifier upgrade, the 1000 pound and the 5000 pound and you discover that the price of desire seems to increase disprortionately to the net result.

To tell you the truth, I'm not fully qualified to answer your questions (and i would defer to to an engine guru in these matters), but I can at least offer a small observation. In my orange race car i'm pushing any number of horses above standard - the car and engine was built specifically for this purpose, namely, zipping around the track. But the downside is that driving on any road with traffic, stop-starts etc can be tedious as this power is really not tapped until >5K revs.

Maybe the best results would come from trying to increase torque - the grunt from the low and mid rev range, perhaps at the expense power.

...and here ends the limit of my engineering knowledge.

Essay: "What IS torque, discuss"...

SRD
 
Good points, torque[8|], how do we go about getting that. I agree that a peaky engine would be a pain. At the mo the car pulls from around 1800 rpm and is a nice drive, just a little more top end would be nice.

I think a chat with andy ref what is the best way forward is in order. I currently have standard heads and non-match manifolds, maybe doing something there would be just enough.[8D]

Any chance of a passenger ride when we are in France?[:)]
 
OK - I think I follow this (metric anybody?). So maybe the question I should be asking Jon D is: Is your car 4 or 5 gears? If four, you might get the performance advantage you're after by substituting a 5 speed box instead. If 5 then you could 'optimise' the ratios to the kind of driving / performance you want - but this is not a cheap option and perhaps you need to balance these costs against engine upgrades (against brakes, suspension etc etc).

Here-in lies the other challenge: Power vs longevity. I was reading an article in Octane last night about how they were managing to squeeze 200 bhp (claimed!) out of an 1600 Alfa GTA engine. Sounds great, but I wonder if the engine needs re-building every time you go for a spin?! Personally I have avoided the desire to push the HP further with my engine - I figured that the bills for a detonating engine were unsustainable! I guess it's a balance that depends on the kind of motoring you're after. Certainly if I was to go in for regularity rallying with the 912 I'd much rather be in a car like Gavins (+ it has a heater!!)

SRD
 
Currently running a 4 speed box, did consider a gearbox upgrade, but as you say big bucks.

Still on the quest for more go, might have to think about what aspect of more go I am after.[&:]

Good document on "whats king" BTW.
 
I'm not so sure the gearbox cost would be too prohibitive, especially if you can trade your 4 speed in. You might spend the same on the engine for a mild performance advantage. Maybe phone around and get a few quotes... I'd be interested to know the kind of costs involved for a reconditioned 5 speed (I'm guessing 1.5K).

SRD
 
Anyone any ideas on the best places to look for a 5 speed box, idealy with some type of warrenty on the rebuild.

I just broken 100 post[:D], stil not catching up most others
 
5 speed boxes do turn up now and again... I picked one up last year for £450 and its a great. You see a lot in the states at the moment - find out whos shipping a car - just an idea.
 
I know of lots of people who run these on drag racing beetles and hot street bugs.

The cost is low. Advantage is (i believe) slightly more responsive engine due to less weight on the crankshaft. Disadvantage is that the gearing ratio between bottom pulley and top cooling fan pulley is changed for the worse. Less revolutions of fan pulley per turn of crankshaft pulley equals reduce speed of fan equals hotter engine.

I would only use on a car that does short distance work only as the small benefit is off set by shorter engine life due to over heating.

ORIGINAL: Jon Darlington

Power pullys (5"), is anyone running one + any idea on the cost and the benfit?
Click to expand...
 
In simplistic terms: turning the cooling fan robs power from the engine, this is the reason you will see drag beetles running without a belt, it frees up more power.

A power pulley reduces the speed of the cooling fan & because the fan is turning slower, the engine is using less power to turn the cooling fan so it releases a bit of power for the motor [:D]
 
I might investigate further, as I have a full flow oil system and an extra coller in the rear wheel arch. Currently (even when being driven hard[8D]) the temp gauge does not move out of the the 1st 1/8th of the temp gauge. [:)]
 
My engine is the same. I can't get it hot no matter how hard I drive it!! I thought the sensor must be faulty but then I remembered that it was the same one as before Mr Prill waved his magic wand! Before the rebuild it often went to the top third of the guage, especially up long hills etc. My engine is same spec as yours, but without the remote cooler and with webers. A well built 912 engine should stay cool enough on the stock cooler. It is only when they get old and tired that the tendancy to overheat starts to occur (unless tin ware is missing etc.)
ORIGINAL: Jon Darlington

I might investigate further, as I have a full flow oil system and an extra coller in the rear wheel arch. Currently (even when being driven hard[8D]) the temp gauge does not move out of the the 1st 1/8th of the temp gauge. [:)]
Click to expand...
 
You must log in or register to reply here.

Posts made and opinions expressed are those of the individual forum members

Use of the Forum is subject to the Terms and Conditions

Disclaimer

The opinions expressed on this site are not necessarily those of the Club, who shall have no liability in respect of them or the accuracy of the content. The Club assumes no responsibility for any effects arising from errors or omissions.

Porsche Club Great Britain gives no warranties, guarantees or assurances and makes no representations or recommendations regarding any goods or services advertised on this site. It is the responsibility of visitors to satisfy themselves that goods and/or services supplied by any advertiser are bona fide and in no instance can the Porsche Club Great Britain be held responsible.

When responding to advertisements please ensure that you satisfy yourself of any applicable call charges on numbers not prefixed by usual "landline" STD Codes. Information can be obtained from the operator or the white pages. Before giving out ANY information regarding cars, or any other items for sale, please satisfy yourself that any potential purchaser is bona fide.

Directors of the Board of Porsche Club GB, Club Office Staff, Register Secretaries and Regional Organisers are often requested by Club members to provide information on matters connected with their cars and other matters referred to in the Club Rules. Such information, advice and assistance provided by such persons is given in good faith and is based on the personal experience and knowledge of the individual concerned.

Neither Porsche Club GB, nor any of the aforementioned, shall be under any liability in respect of any such information, advice or assistance given to members. Members are advised to consult qualified specialists for information, advice and assistance on matters connected with their cars at all times.

Porsche
Lockton
Pirelli
Officially approved
Oracle Finance
WEX Esso
Collecting Cars
Archant Dialogue
Back
Top