CIS - A New Look for an Old Technology
03-03-2006, 11:33 AM
#1
Developer
Thread Starter
CIS - A New Look for an Old Technology
The latest technology advance for injector lines has been the teflon-lined stainless-steel braided hose outfitted with stainless steel fittings. The Big Boy dragsters have to use these to support the 1000+ HP engines and resist the corrosive properties of methanol and nitrous.
They are also very suitable for gasoline as a fuel - and where our CIS systems are concerned - we run at pressures of 6 to 7 BAR - so the strength of these fuel injector lines is welcomed. It's either this, or hard lines.
A CIS injector at WOT at 6 BAR will spray 230cc per minute! (I know, we tested to find out). Feeding that beast has been the limiter on how much HP we can get from CIS. Do the math - light up 8 CIS injectors like that at one time and you will need to be apply to supply just about 2 Liters of fuel each minute at WOT. The injectors have always been big enough in CIS, IF you can supply them.
Last year, I made my own injector fuel lines from modified brake lines, and they worked OK but I had trouble getting the fittings to not leak. This year, I have fitted the engine with the complete package: a modified Mercedes Benz aluminum fuel distributer with individually-adjustable pots, -3 AN teflon fuel injector lines, and new fittings.
Here are some photos of the lines installed, the modified aluminum CIS fuel distributor, and the difference in size between the stock CIS fuel line and the -3 AN fuel injector line.
They are also very suitable for gasoline as a fuel - and where our CIS systems are concerned - we run at pressures of 6 to 7 BAR - so the strength of these fuel injector lines is welcomed. It's either this, or hard lines.
A CIS injector at WOT at 6 BAR will spray 230cc per minute! (I know, we tested to find out). Feeding that beast has been the limiter on how much HP we can get from CIS. Do the math - light up 8 CIS injectors like that at one time and you will need to be apply to supply just about 2 Liters of fuel each minute at WOT. The injectors have always been big enough in CIS, IF you can supply them.
Last year, I made my own injector fuel lines from modified brake lines, and they worked OK but I had trouble getting the fittings to not leak. This year, I have fitted the engine with the complete package: a modified Mercedes Benz aluminum fuel distributer with individually-adjustable pots, -3 AN teflon fuel injector lines, and new fittings.
Here are some photos of the lines installed, the modified aluminum CIS fuel distributor, and the difference in size between the stock CIS fuel line and the -3 AN fuel injector line.
Last edited by Carl Fausett; 03-03-2006 at 03:45 PM.
03-03-2006, 12:09 PM
#4
Three Wheelin'
A very very tidy install. Nice work. Are those aluminum mercedes fuel distributors readily available? Hate to burst your bubble Carl, but the system on the 917 is not CIS its the earlier MFI that they ran with individual throttle bodies. Had a system like that on my 1970 911S. That system makes big HP.
03-03-2006, 01:07 PM
#6
Rennlist Member
Very nice setup! More details please! My understanding is that a stock 928 is more limited by it's breathing aboility, than it's fuelling ability -- Are there any gains to be had with this with a non-SC car?
03-03-2006, 01:26 PM
#7
Addict
Rennlist Member
Rennlist
Site Sponsor
Rennlist Member
Rennlist
Site Sponsor
Yes Carl FBIII is correct the 917 was direct mechanical injection there is a drive belt an the back of the pump which is a positive displacement with small pistons in each "cylinder" timed injection. Used on many Porsche race cars and 911 S and E cars 1968-early 1973 or so ultimately replaced by CIS on the 911 to meet the emission standards Euro 911s used it until 1975 as I recall. And yes my early 2.8 liter 911 has this system individual throttle bodies modified to RSR specs and 6 stacks with K + N filters. The 911 race car which used CIS was the 934 those fitted with mechanical injection were 935 variants. But back to your CIS that really looks great ,very nice. Clearly a labor of love.
Trending Topics
03-03-2006, 03:38 PM
#10
Developer
Thread Starter
Thanks for straightening me out on the 917. I'll be a lot older before I know everything about this marque.
I had no intention of making and selling these lines at all.... did not figure anybody would be as nuts as me and want them.... and no, unless you have an
"out there" supercharged CIS system, there is no gain to be had enlarging the injector lines.
The stock fuel lines supply all that is needed for naturally-aspirated CIS and up to about 6 psi of boost. I am going to try to run 14 psi of boost this summer, so that is what makes me run around and modify things like this.
...and it is not just the injector lines. We had fuel distributer re-machined by a specialist in the UK to supply the same fuel at idle, yet ultimately 30% more fuel at WOT, and a linear fuel enrichment between the two.
Then you need to replace the single 7.5 mm fuel line from the gas tanks with two 7.5 mm fuel lines, dual CIS fuel pumps in parrallel, and 2 fuel inlets to the fuel distributor. It is never as easy as just changing 1 thing and getting more HP.
Analogy: just like dropping Euro cams on a US 16v motor and wondering why nothing happened. Well, you need Euro heads, euro throttle body, intake runners, plenum, and (argueably) euro injector lines and fuel distributor.
This injector line mod is like that.... by itself, it will not do anything. You have to do all the other stuff too.
So Carl, when are you going to start marketing the injector, cold start injector and WUR lines?
"out there" supercharged CIS system, there is no gain to be had enlarging the injector lines.
The stock fuel lines supply all that is needed for naturally-aspirated CIS and up to about 6 psi of boost. I am going to try to run 14 psi of boost this summer, so that is what makes me run around and modify things like this.
...and it is not just the injector lines. We had fuel distributer re-machined by a specialist in the UK to supply the same fuel at idle, yet ultimately 30% more fuel at WOT, and a linear fuel enrichment between the two.
Then you need to replace the single 7.5 mm fuel line from the gas tanks with two 7.5 mm fuel lines, dual CIS fuel pumps in parrallel, and 2 fuel inlets to the fuel distributor. It is never as easy as just changing 1 thing and getting more HP.
Analogy: just like dropping Euro cams on a US 16v motor and wondering why nothing happened. Well, you need Euro heads, euro throttle body, intake runners, plenum, and (argueably) euro injector lines and fuel distributor.
This injector line mod is like that.... by itself, it will not do anything. You have to do all the other stuff too.
