TheSamba.com :: View topic - Easy, Inexpensive Fuel Injection Conversion

Tue Jul 22, 2008 2:27 pm

Our company has been building products for CIS fuel injection, primarily for Porsche and Mercedes. We were trolling around for another test platform when we had the bright idea to convert a Type 1 to CIS fuel injection. Sure this has been done before, but since we needed a ready supply of fresh meat we decided to make the conversion easy and inexpensive. Yes, it can be done! Basically we came up with a few important pieces to graft a CIS fuel injection system from any 1st generation Rabbit/Jetta/Scirocco/Cabrio onto any air-cooled Type 1 or Type 2.

Dimensioned drawings and material lists will be posted on our website in the next few weeks. This info is being made available to the VW community at no charge. We were amazed at how much better our '69 VW ran with fuel injection. We'll post test results soon but the power and economy are significantly improved.

Why is CIS a good choice? To put it simply, it's easy and inexpensive. The complete injection system cost about $200 at the local pick-your-part junkyard. We could have paid 1/2 price on Tuesday, but I was busy that Tuesday! CIS parts are widely available used, new parts are very cheap (injectors <$40), there's no wiring harness, tuning is easy, and the stock system is capable of big power (200hp or more). The rest of the conversion parts were about another $200. The cost is far less than a good set of carbs and it's much easier to tune for either power or economy. If you want your Type 2 to get 25mpg or you're building a sand-rail motor then fuel injection is the way to go.

The engine below is in a '69 type 1. These photos were taken just after we got it running so it still looks a bit sloppy. This is a Dual Port engine with heads from DRD Racing. The displacement is 1915cc and the compression is set to 8.5:1 with a mild street cam. Since we had the engine apart to check everything we also threw in a set of gapless rings because we're planning to add a turbo later. Here's the complete install:

In case you're wondering, the hood closes just fine over the fuel distributor. The air filter isn't in place in the photo but it sits below the fuel distributor. The center tube and the two manifold plenums on the sides are the only major custom pieces in the conversion. The center piece is here:

The side manifold plenums sit on low-profile Type 3 Weber carb manifolds, CB performance PN 3170. Here's a photo of the passenger side showing the unit in place:

We used Mercedes injectors for better flow and lower cost. This drawing shows how the injectors are mounted in the plenums is here:

There's a ton more info on the way, including a low-buck tuning method using a $20 narrow-band O2 sensor. Economy and performance tuning numbers should be available next week.

Tue Jul 22, 2008 2:46 pm

Belongs in the vendor section.

Tue Jul 22, 2008 2:53 pm

You must be joking. I'm not selling anything. UT doesn't sell any VW products. The project was done as a test platform for other products which are not VW related. I'm a VW owner. The car in the photo is mine. The only way this kind of info would come into the public domain is through a sponsor. That's good, right?

Tue Jul 22, 2008 2:54 pm

Ahhhh Bosch CIS.

Best day in the world was when I pitched it from the Audi for something better!

-Dave

Tue Jul 22, 2008 2:55 pm

looks kinda scary...

Tue Jul 22, 2008 3:11 pm

This car started with a Weber IDF, then a Weber Progressive. Tuning those carbs was scary. I sure missed having a choke in winter. Tuning with an O2 sensor never got the car out of the teens in MPG. I'll take the plumbing, if it works.

Tue Jul 22, 2008 3:11 pm

its pretty messy, but not too bad.

why not cast DP manifolds with injector holes, and run a single TB like a stock center mount carb?

simple, clean, looks stock.

Tue Jul 22, 2008 3:16 pm

That would be the way to go. That would make this a very easy and clean bolt-in. If any reputable fabricators are out there we would be happy to contribute the mechanical design. We're not in that business.

Tue Jul 22, 2008 3:28 pm

cb performance makes them, and the are drilled for GM injectors.

use those, coupled with a TB from a modern vehicle.
T-pipe to the endcastings

Tue Jul 22, 2008 3:40 pm

And then add an ECU, Air-mass and other sensors, wiring harness, some way of mounting everything, and don't forget some kind of programming setup. Hex files anyone? CIS is a simple mechanical package and it's as easy to program as EFI, just simpler and less expensive.

Tue Jul 22, 2008 3:40 pm

dog_jr911 wrote: use those, coupled with a TB from a modern vehicle.
T-pipe to the endcastings

Like mine?

Tue Jul 22, 2008 4:03 pm

like MINEEEEE!!!!!!!

except i still have two more pieces to fab

and the injectors/rails arent mounted, its just mocked up right now.

between turbo- TB
TB to cross section

lots of work to do still, i know....

Tue Jul 22, 2008 8:03 pm

Here's a view of the intake plenum mounted to the manifold, very clean:

This shows the big advantage of CIS over EFI. All you have to do is work out the plumbing. There's no mess of harness/connectors/sensor/ecu/tuning/programming and the cost is a lot less.

Tue Jul 22, 2008 8:23 pm

never heard of cis, ill do a lil research

Tue Jul 22, 2008 8:34 pm

Here's a closeup view of a CIS injector:

Note that it's tiny compared to an EFI injector. The business end is only about 0.25" in diameter. There's a handy fitting on the top and there's no electrical connector. 8 of these will flow enough fuel for a 600hp V-8 and they cost about $30.

Tue Jul 22, 2008 8:45 pm

what does CIS stand for?

Tue Jul 22, 2008 9:20 pm

did some research....

CIS is made by Bosch and has been in use since the mid 70's on VWs and many other european cars. It stands for Continuous Injection System, which means that fuel is continually atomized into the intake manifold just upstream of the intake valve. Fuel flow is directly controlled by airflow through a mechanical connection to an air vane which in turn moves a plunger which regulates fuel flow. Pure CIS is altitude compensating to some extent, since when less air flows, less fuel flows. You could also dispense with carb heat since there is no venturi, and the primer since the cold start valve is built in. Decreased workload is always a good thing.

Here's a schematic of an early VW Rabbit's mechanical CIS system.

The control pressure regulator (fuel enrichment for cold starting and altitude compensation) is also mechanical, but can be electrically heated for "choke turnoff". The fuel pump delivers about 75 psi, which has never been a problem on cars since the injector lines are braided stainless steel from the factory, and "never" fail. The pumps are extremely reliable and give fair warning by insufficient delivery at high speeds.

A later version of CIS named CIS-E (E is for Electronically fine tuned) has a lighter aluminum fuel distributor body, rather than CIS's steel version. It also has a differential pressure regulator built in that adjusts the mixture electronically based on input from the oxygen sensor. This would be even better for altitude compensation, but when that sucker quits (or the connector falls off), you better be over a good landing spot. I once went around a curve at the limit in my 16V Scirocco and the centrifugal force let the connector come loose (which I hadn't connected properly earlier) and I thought I was going to have to push it home. That's the downfall with CIS-E. It CAN leave you walking if one wire falls off. That can't happen with "pure" CIS, unless you run out of electricity to power the pump.

Having said all of this, CIS is extremely reliable as it came from the factory. Most cars go their entire lives with no more maintenance than changing the fuel filter every 30,000 miles, and most probably never even get THAT! If I were planning on using CIS for the for Corvair, I'd look for BMW, Mercedes, or some other 6 cylinder systems since their fuel distributors already have 6 lines running out of them, although given the goofy Corvair intake manifold, a four banger version would probably work just fine plumbed directly into the manifold. If you want to know more about Bosch fuel injection (in excruciating detail), go to www.rb.com and buy "Bosch Fuel Injection & Engine Management".

The downside to CIS is that it weighs at least 15 pounds more than a carburetor when you count the pump, accumulator, etc, even when you consider the weight savings of ditching the carb heat box and primer.. And the CIS equipment is fairly large, so you better have a lot of room for it under the cowling. I suspect that the benefits don't "outweigh" the extra weight, and I'm surely not going to go that far out on a limb during first flights with a highly modified airframe and engine too. There is some concern about g-loads affecting the vane (and thus fuel distribution) during abrupt turns or manuevers, but the thing is counterweighted so that shouldn't be an issue.

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CIS was developed by Bosch to replace mechanical fuel injection. While mechanical fuel injection is very efficient in supplying the engine with fuel, it takes horsepower to drive the pump. In some cases there is up to a 15 HP parasitic power loss. CIS does not have this downside, and is rugged and easy to maintain. It does, however, have some inherent drawbacks which must be taken into consideration. Air flow to the engine is restricted by the sensor plate. Excessive lift and duration camshafts and the inertia of the incoming air itself can cause poor throttle response due to the air sensor plate being bounced around. In addition, a phenomena called "charge robbing" can occur. This is caused by excessive exhaust overlap (i.e. the time span that both the exhaust and intake valves are open right before the intake cycle). This allows the exhaust gasses to flow backwards into the combustion chamber diluting the intake charge. For these reasons, camshaft selection should be carefully considered. Aggressive camshafts suitable for earlier model engines may not work well, if at all.

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Tue Jul 22, 2008 9:59 pm

The fuel pump/accumulator package weighs about 5lb. The CIS fuel pump is bigger than an EFI fuel pump because CIS re-circulates the fuel back to the tank to cool the system. This is a huge advantage on air-cooled engines where the heat soak is brutal. EFI systems don't have any cooling mechanism. Please note we're biased toward a system on a "stock" body running with the hood closed. The pieces we're showing here were designed as an easy as possible bolt-on, perhaps without removing the engine. A sandrail would be something else entirely.....

On a Type 1 there's a very handy shelf to mount the fuel pump/accumulator just behind the front beam on the passenger side. I'll post photos tomorrow. The fuel distributor/air metering assembly/throttle body mounts to the doghouse. Simple.

The VW Rabbit/Jetta parts suitable for transplant onto air-cooled engines are all aluminum.

CIS is extremely reliable, rugged, and easy to fix. There are a lot of myths about CIS. CIS was used on stock engines up to 6.9 liters. No kidding. There's a ton of excess capacity in these systems. CIS also handles agressive cams quite well. High cam overlap is a challenge for any fuel delivery system. CIS is no different in this respect, except that it's vastly easier to tune than either carbs or EFI.

Tue Jul 22, 2008 10:44 pm

that was copy-n-pasted, BTW.

sounds cool!

question, can you supply a price, or qoute?

price and time required, minus fabrication?

Tue Jul 22, 2008 10:51 pm

UT_Tech wrote: The CIS fuel pump is bigger than an EFI fuel pump because CIS re-circulates the fuel back to the tank to cool the system. This is a huge advantage on air-cooled engines where the heat soak is brutal. EFI systems don't have any cooling mechanism.

Gonna call BS on you there, turbo. While it is true that some EFI systems these days are returnless, most (my system included) still have the return style regulator. If you need proof, just look at any T1 FI Beetle, or T3 FI Squareback. If I had to guess, I'd say the CIS pump is larger due to needing more total flow at any given time besides WOT than an electronic system (CIS injects all the time, EFI only some of the time). Besides which, if the components of a returnless FI system were not up to the task tempurature-wise, you'd see a lot of failures with those cars. If you don't think a watercooled car's intake tract/cylinder head gets hot, you've got another thing coming. My EFI 1915 turbo's intake doesn't get any hotter than any other car's intake system.

UT_Tech wrote: CIS is extremely reliable, rugged, and easy to fix.

Rugged and reliable- damn right, they do seem bullet proof.

But if you don't know what you're doing, it's no easier to repair than a carb or other injection system. Any system requires requisite knowledge to be able to repair it, I think you're letting your experience get in the way of giving advice here. For example- I'm lost as hell when it comes to CIS, but I can tune the crap out of any car with Megasquirt. That leads me to recommend it to everyone, because I think it's easy and worked for me- that doesn't mean it'll be easy, or work at all for some other guy. :wink:

UT_Tech wrote: CIS also handles agressive cams quite well. High cam overlap is a challenge for any fuel delivery system. CIS is no different in this respect, except that it's vastly easier to tune than either carbs or EFI.

Megasquirt has a hybrid TPS/MAP mode that easily handles long duration cams/ITB setups as well, so CIS is far from the only option out there. I suggest you do some research on this issue, you'll find that CIS is a far outdated system. Not that it doesn't work, because I know people who have it. It's just that to me, CIS is more of a step up from a carburator, but a huge step back from programmable electronic fuel injection. You still won't get the closed loop accuracy or adjustability with CIS that you do with electronic; CIS-E comes close, but still no cigar. It's had it's time, the world has moved on to better things.