tazzieman Posted 7October, 2014 Report Share Posted 7October, 2014 The post August '77 had the intercooler and the extra 300cc capacity. From Paul Frere's book "Porsche 911 Story" re the intercooler - (italics are mine) ..this explains why the increase in power , and especially in torque , is greater than the increase in engine capacity , in spite of the addition of an air pump blowing into the exhaust ports made necessary by the stricter European emission laws implemented in 1978" This implies the air pump is a robber! More Link to comment Share on other sites More sharing options...
Tit Posted 7October, 2014 Report Share Posted 7October, 2014 If it ain't contributing to power output, or it doesn't pass the bling test, then it's got to go! Link to comment Share on other sites More sharing options...
GregAx Posted 7October, 2014 Author Report Share Posted 7October, 2014 gax , what year is your 930? Potentially (on the later turbos) the air pump only works for ~60 seconds after startup from cold , the a valve reroutes the air into the cat. Thereafter the pump is a dead weight and even steals a few hp, not that you'd notice in a 930. A parts diagram for your 930 would help. Mine's an early 1979, and still retains the original exhaust. I claim to be no expert on this but I enjoy the research and learning process on these P cars. As I mentioned before I was more after the originality aspect of retaining the air pump due to the spider tubing and injectors still being present. So my options were to either remove the tubing and injectors and plug the holes or source a pump and return it back as intended. I can't comment if it's going improve a 35 year old turbo though if I was chasing performance it's not a mod worth discussing as I am sure either way it's minimal. Link to comment Share on other sites More sharing options...
tazzieman Posted 8October, 2014 Report Share Posted 8October, 2014 If you ever pull the exhaust , please get a pic of the injector nozzles! It would be fascinating to see what shape they are in after all these years ; it's a brutal environment in there , I wonder if they ever break off? Mine's an early 1979, and still retains the original exhaust. Link to comment Share on other sites More sharing options...
Peter M Posted 8October, 2014 Report Share Posted 8October, 2014 Taz, I was hoping you had shelled out and bought the SAE paper and was going to enlighten us! Link to comment Share on other sites More sharing options...
tazzieman Posted 8October, 2014 Report Share Posted 8October, 2014 Taz, I was hoping you had shelled out and bought the SAE paper and was going to enlighten us! I don't need to , as the graph summarises Dr M's results! But you are right , I am inclined to pursue these things if for no other reason than to keep the brain in tune. I go round to my nearly 88yo father's place and he has thick calculus books open on the kitchen table (and is actually solving problems , not just using them to make cheeses). And he was never a practising mathematician! You're never too old to learn! Link to comment Share on other sites More sharing options...
Peter M Posted 8October, 2014 Report Share Posted 8October, 2014 I'm just keen to know if the secondary air injection is the standard Porsche system and not some special set up! Initially I was sceptical but after verifying the peak figures in the graph matched the published factory figures for a '76 turbo I started to think more openly. Then I recalled reading about Smokey Yunick's experiments with drilling holes in the headers of his race cars to support post combustion oxidation to increase/maintain heat and therefore gas velocity. I would think that at low engine speeds and WOT like on the turbo test when the SAI is shown to have greatest effect there would likely be a lot of unburnt HC passing out the exhaust valve and then, well, you know, it's all seems more feasible...... Link to comment Share on other sites More sharing options...
Russ Posted 8October, 2014 Report Share Posted 8October, 2014 so at the end of the day has anyone found gax a turbo air pump? lets remember that's what this thread is lol Link to comment Share on other sites More sharing options...
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