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jpnovak jpnovak is offline
I would rather be driving
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Join Date: Apr 2000
Location: Austin, TX
Posts: 8,108
Cory. You are really stirring up the pot. Here's my $0.02 worth of a diatribe.

I have installed quite a few EFI systems on NA and turbo cars (including 930s). I often get asked the same questions by potential customers that, I am sure Chris and Brian get asked. Chris gets asked the questions as a proponent of EFI (and some incredible builds). Brian gets asked the questions as a fine re-builder of CIS components - and valid argument that CIS is a good system to rebuild.

The primary question is something like this. "My CIS system seems to be working properly. Should I go EFI?" My answer is that there is no need to change over for a stock system. If the time comes and a component fails this may be a time to convert depending on what failed. I have rebuilt CIS systems and you would be surprised what happens when you simply clean out the fuel head and reset the mixture. Ailing fuel pumps and out of spec WURs are another story.

The next question is something on the order of... "I want to modify my engine. Will EFI help me meet my power goals?" In this case, the answer is, "it depends, on what those goals are." Understanding the limitations of CIS, how it functions, and more importantly when will it fail to meet the fuel delivery demands ALL over the power curve is important. Sure you can play with system pressure to make it dump a lot of fuel on the top end if you crank up the boost. Often this means the low-end is running too rich and performance suffers. Brian seems to know these tricks. I do not, but can easily setup an EFI system that operates perfectly in both scenarios. What happens to CIS when you swap cams? CIS does not tolerate reversion pulses well. This is not a problem with EFI. See how there is no right answer to this one?

Other questions are related to system setups. Some guys want it turn key. Some like a base system setup that they can tweak themselves. Some guys want the components to completely DIY a system. The entire spectrum of market segment is out there. It is important to listen to a potential customer to understand what they want, their expectations and then weigh all the options.

I have heard this before that the best EFI system is one that the tuner understands. If your shop is familiar with Motec - use it. Maybe its Megasquirt, or Haltech, or SDS, or Emerald, or AEM, or... Name it. It does not matter because they are all computer chip based systems connected to wires to drive electromechanical devices. The differences are in the interface software and the human interface that understands how to properly make them work as a complete system. Only then, will the end result of a modern injection and timing system be apparent.

But isn't this what we would all expect? The CIS (jetronic) variations have been around since the late 60s. It debuted by Porsche in a 73MY (1973.5 911T). It was ahead of its time for drivability, fuel consumption and emissions. But a lot has happened since then. We know more about the combustion process and have more accurate methods to control them.

EFI can be installed on a budget. You do not have to spend mega dollars on these cars. Several responses to these threads outline very cost effective conversions. Is this more than rebuilding a WUR? In most cases, yes. Does CIS stir the soul? Not mine.

To me, its a no brainer to convert to EFI. Adding modern control systems to classic designs is what I am passionate about doing. The control systems can be engine, or suspension, or brakes or... Well you get the picture.

In the end the question to upgrade is about passion. Passion for keeping a car completely stock, Passion for mods as long as they are reversible, and even passion for no-holds barred turn this thing up to 11 type of mods.

What is your passion?

This last question is rhetorical to Cory. I know his answer and its not about keeping things stock.

And yes, it is possible to add EFI on the stock injection blocks. There are limitations to this, just like there is on everything else. Design a "system" and you will have good results with EFI. Part of that system is the human factor involvement.
Jamie - I can explain it to you. But I can not understand it for you.
71 911T SWT - Sun and Fun Mobile
72 911T project car. "Minne" - A tangy version of tangerine - EFI conversion parts
Old 10-14-2014, 07:25 PM
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