Air pump + EMS

[Chris Goodman]

Hello fellow owners of " the best air-cooled Porsche you' ll ever buy" (911&Porsche World)! []

Having just bought a low mileage, all original, 204bhp SC Coupe I' ve been avidly reading everything I can find in the mags and bought some back copies at Castle Howard. Found a number of references to ' removing the air pump' for better power / economy etc. and an article on getting an engine management system fitted to allow use of 95 octane. What do you think? Are these worthwhile mods or are you from the ' if it ain' t broke don' t fix it' school of motoring?? Is the air pump just another nasty concession to the US emissions lobby or does it serve a useful purpose?

Chris

 

[Guest]

Hi Chris
I removed the pump and the bracket from mine which makes the engine bay look less cluttered and access to the left hand side of the engine easier. Clearly driving the pump must have used some power, but I would say its negligable. Will have to see what the emmisions are like when it' s mot' d next month.
The petrol debate seems to produce conflicting opinions. According to the handbook, our 204bhp models are meant to be run on 98 ron. Thee AA say use one tank of LRP for every three of un-leaded. The chap at the Porsche specialists here in Glasgow reckons all cars built after 75 can run on un-leaded with no adverse problems. I myself have used LRP, un-leaded and Shell' s wonder fuel. I wonder if you just need high octane petrol to achieve the claimed 204 bhp and if you don' t use it, the power might be down a bit but valve seats will be un-harmed?Anybody got the definitive answer?
Cheers

 

[Peter_Bull]

Clearly driving the pump must have used some power, but I would say it's negligible. Will have to see what the emissions are like when its mot' d next month.

Hi Jeff / Chris
It has been said by my wife that I am a bit of a ' spotter' when it comes to Porsche' s and I have to say she probably is spot on - but don' t tell her I admit it if you see her - PLEASE!
Anyhow regarding the air pump.
In the interests of being a spotter (above) I have left my air pump on, and just removed the belt. It all looks standard when the engine lid is lifted - just no belt. I have been informed that there is a potential gain of 5 BHP when the belt is removed. I have never had a problem with the emissions on my MOT - so hopefully yours will pass OK - providing the rest of the engine is spot on.
As an aside "" I have been informed that those SC owners that have removed the air pump and ditched it have subsequently found it sometimes difficult to find a replacement. So at least if you leave it on the engine there will be less chance that you will lose it or "" dare I say it "" that the wife will put in the bin!
Have fun,
Peter

 

[Chris Goodman]

Thanks for the info - I' ll wait a little longer to see if anyone comes up with a reason to keep the pump and then follow your lead!

On the fuel I' m a little less clear. Aren' t there perhaps two seperate issues - lead and octane rating? I' ve read that the SC' s had hardened valve seats because the US market was using unleaded much earlier than the UK so hopefully Unleaded, Super Unleaded, and Shell Optimax should all be OK from the valve seat point of view. However 95 octane Unleaded could presumably cause ' pinking' and piston damage even if it doesn' t damage the valve seats. Anyone know any different? Even without an Engine Management System can you just adjust the timing for the lower octane fuel? I' m currently using LRP as the safest option but I hear that' s being phased out this year.

Chris

 

[Guest]

The manual for my 1980 SC (180bhp) said to run on 2 star (yes, I am that old), which really used to bug people in petrol stations, as they thoght that I couldn' t read the pump - ' cheap fuel in a Porsche ?' And it ran fine.

 

[RSGulp]

I don' t touch LRP fuel after reading too many features in ' non-Porsche' classic car magazines questioning it' s quality. Lead basically acted as a lubricant and LRP uses various chemicals to replace the ' lead' content but too many very ' well-read' car-types have questioned it.

I use 98 Ron ' Super Unleaded' where available, or Shell Optimax. If not available I use 95 Unleaded - and an additive which you can buy in a bottle from Castrol (or other reputable brand) every time I fill up (I wouldn' t trust other ' cheaper brands' ).

Air Pump? Simply take off belt (and keep it!) and tighten the nut to hold the pump as far to the left as it will go. Car passes emission test every year and runs perfectly. Didn' t notice a rise in bhp but have been told it' s between 2 - 5 bhp more, but as all our cars are getting on a bit I don' t suppose they' re actually obtaining the claimed 204bhp anyway.