Carbs to CIS/with pics conversion

[spiffy]

http://rivieraregistry.com/phpBB2/viewtopic.php?t=43

From the wonderful folks at the riviera registry site.....kudos Heather and Brandon (pretty good for a diesel mechanic)

[vwlover77]

Any info on how it performs??? I didn't see any in my quick perusal of the photos....

[spiffy]

When we saw Brandon at the last Wet Westies event his bus seemed to be happy happy.....not sure on the particulars though....hopefully vwdreamer will chime in and fill us in on the details.

[VWDreamer]

Ok totally missed this thread!

Brandon has only had one issue and that was his fuel pump relay going out. Other than that he has been getting great mileage...i believe in the low 20's around town/hwy (mixed)... we towed an 1800lb trailer to burning man last year and were getting about 17-18mpg and crusing at speed (45-50 on those roads) and up hills and everything, had no problems.

I think this is a great upgrade, mainly because its mechanical also because parts are readily available, I recommend going to a junk yard and collecting most of the parts, but replacement parts are pretty much everwhere.

He is still trying to convince me that i should install CIS on BusZilla.... but he will have some more work to do, the mileage has me sold, I am just worried about performance, and getting runners for the T1... but i think with tweaking it *might* be a good upgrade :)

[IFBwax]

I think Tristessa did this with his bus. He had to tweak it a bit, but I think he got it to run just fine. Hal?

[Amskeptic]

Jake Raby put CIS on his bus, the one that tows the Bluebonic Plague up hills at 80 mph while getting 30 mpg at a CHT of 350*, yeah that one.

My experience with CIS vs L-Jet is that the installation of CIS is a pretty involved project with enough modification required that you ought to think about what is it about CIS that you like so much more?

In the write up on the Riviera registry, the L-Jet was dissed for having an airflow meter where allegedly the "air door" fails and the ECU is considered a weak link. Any others have those problems?

I love the L-Jet on the Type 4 engine. It is unobtrusive and rugged with great flexibility in fuel adjustments over the entire range of operation. The CIS mixture is determined by changing the fulcrum depth of the airflow plate. The shape of the cone in which it moves determines the mixture at various RPMS. It is not adjustable. You only get the mixture dialed in at idle with the 3mm allen wrench. That's it. I cannot say if the sensor plate and cone that you have rustled up are perfectly suitable for the bus. Also, the write-up in the above link has an error. The primary throttle plate is the smaller one. The larger plate is the secondary.

My CIS cars, old Rabbits and my current Mercedes, have been reliable as well, but with the classic CIS quirks, hot start issues and extremely cold start issues.

If you have a performance Type 4 engine, the CIS has good reasons. If you have a stock L-Jet Type 4 engine and the experience of accelerating BobD's magnificent bus onto the freeway with a crisp shift into 4th at 55 mph, you ask yourself. . . is there any improvement possible to this? Of course not.
Colin

[Brandon314159]

Hello all,

Some may recognize the name...others perhaps not. I figured I would chime in real quickly. :)

The debate between CIS and L-Jet is a long one and honestly isn't one I am about to delve deeply in to. Anyone who wants to read the holy grail of information/pros/cons/etc. of the Bosch systems can pick up the blue book "Bosch Fuel Injection & Engine Management" by Bently. It goes into quite a bit of details not only regarding stock arrangement, but also the performance after-market scenarios. An interesting book if you have the time.

My personal experience/thoughts/2-cents? I've built L-jet, I've built CIS, CIS-E, CIS Lamba, Motronic, etc. etc. and honestly each has its gains and let downs.

I chose CIS Mechanical because I wanted the following:
-Easy roadside repairs w/ readily available parts
-Cheap
-Decent Economy
-Better Airflow
-Better Fuel Atomization
-Dirt Simple
-Low Engine Fire Risk

There is a whole batch of other reasons but those were my main ones. The intake runners (for building the second CIS bus) were actually even more simple than the first. Using brass compression fittings, a drill, and a tap; no welding was required. This setup worked very well and helped with diagnosing initial vacuum leak sources.

Bus number one regularly clicks off 18-20mpg on the freeway doing 65-75MPH with medium load of camping gear and two people. Part of this is the fuel system, the other is the very tall 4th gear (custom installed). When taking a 600mile trip to Nevada last year it clicked off 17-19 with a trailer (1100lbs load), three occupants, and enough materials to live for 2 weeks (save water). Increasing the trailer load to 1600lbs and throwing some hills in the way dropped the mpg to about 15-17. Keep in mind most of this was 80-95F+ degree weather and thus the whole vehicle was working hard. Overall average for the whole trip was 16-17mpg. Anyone owning a 2.0L Riviera knows this is not doing too bad. (BTW all mileages are speedo corrected with GPS).

Daily driving with the vehicle results in 15-16mpg city driving simply due to a lead foot and the joy associated with snappy throttle response. I built a 1.8L aircooled and used all factory L-Jet and the owner claims to be clicking off 18-20mpg (Westy baywindow) however they are very easy drivers and after all, the engine was brand new. :)

A couple comments. Regarding the throttle body. If you continue reading down further past the picture you will see that I describe the "smaller" secondary throttle plate not in comparison to the OTHER plate in the throttle body, but actually the other TYPE of throttle body commonly available for CIS setups. Keep this distinction in mind. Generally speaking, big plate = high(er) top end power, small plate = low end torque/good throttle control.

Secondly, although the CIS system has only one adjustment (actually it has 5 but we won't get that deep into the fuel distributor) it actually only needs 1. No vacuum leaks assumed, if you connect your favorite wide band Air/Fuel meter to the bus, you will see something remarkable. It works...without a computer, without major adjustments, without even any electronic engine temperature sensor. The beauty of the system lies in the WUR (Warm Up Regulator) and its ability to do not only (if properly connected) warm up fuel regulation but also fuel adjustment for altitude and even intake vacuum/PRESSURE across the entire RPM/Fuel range. Not bad for two wires and two hoses. :)

Regarding L-Jet failures, there are a few big ones (atleast here in the PNW). The air door in the early models will physically break if the vehicle ever backfires. The air door has a finite life determined by the amount of time it spends at cruising or off idle intake air amount. Eventually it will wear through the resistive strip. Secondly, they are not easy to find and are rather expensive. I'll not state the obvious fuel injection rubber line failure resulting in an engine bay/heads/cylinders covered in raw fuel. IE, fire.

The CIS has its problems too. Bad injectors (due to bad fuel or sitting too long), sticky fuel distributors, bad fuel pumps, or intake boot failure will bring this system down pretty quickly. The injector problem is similar for all fuel systems (an extreme plug/dirty injector causing a lean cylinder and a melted piston). The sticking fuel distributor I have mostly only seen with a) poor fuel or b) varnish due to spending a life in the wrecking yard. The fuel pumps are expensive although when you compare this to the L-Jet's interestingly designed double relay/fuel pump/etc. it doesn't seem so terrible. Either system will die if the intake boot rips open due to a load of false air. The Aux Air Controller (or IAC) is the same unit on both systems (go figure...Germans).

What am I trying to say? I guess that if you have L-Jet and it works, stick with it. If you have CIS and it works, stick with it. Anyone who does some background research into CIS will see that even in its early stages it was FAR beyond it's time from an engineering standpoint. The fact that I can bolt this stuff on my 2.0L air-cooled engine (which CIS mechanical for VW/Audi was never designed for an engine of such size to my knowledge...maybe an odd GTI or something), and have it work with one simple adjustment of the CO. Blows me away. Honestly, the job is not for the average do-it-yourselfer. Although chances are if you can't do a CIS fuel injection build, you couldn't tear apart the L-Jet system comfortably (although you can just drop it on a Type IV if you are really lacking the skills/understanding). The CIS you can obviously not.

Plus when I need spare parts or something fails, I know the local wrecking yard or tiny parts house is likely to have something that works. It is almost as fail-safe as a carburettor.

For performance considerations, stay away from both systems unless you aren't running an aggressive camshaft. The CIS works very well with light (8psi or less without modification) turbocharging because of its WUR helping with on-boost fuel ramp-up. Agressive camshafts will kill both L-Jet and CIS AFM (Air Fuel Meters) because the pulsations cause erratic fuel distribution off idle and make tuning for daily driving almost impossible. The air door for L-Jet looses accurate airflow measurement at higher RPM/airflow due to the door being almost full open. Check the afore mentioned Bosch book for more details.

The CIS will wind my stock 2.0L until the valves float (about 5800-6K RPM) and 4th gear can be grabbed anywhere up to about 75MPH. It is a fun vehicle for sure. I am waiting for the 2nd bus I built with a CIS 2.0L and large throttle body to break in so I can see what it is capable of. Both are meant to be daily drivers and last a long time. The last time this my engine was apart was when my dad was 22 (40's now) and it hasn't missed a beat.

Maybe someday a little turbo-charger will be in order. My K24 is waiting.

Cherrio and motor on!

P.S. If I have my way the Unimog will end up with CIS too. Who says they don't run upside down. :D

[Jake Raby]

Yep and the only thing I have done to my CIS in 7 years is swap a warm up regulator....

CIS makes torque like no other arrangement I have experienced. On my dyno the engine would pull to 350RPM @ WOT without stalling and thats why it tows so well for me.

[karl]

Yep and the only thing I have done to my CIS in 7 years is swap a warm up regulator....

CIS makes torque like no other arrangement I have experienced. On my dyno the engine would pull to 350RPM @ WOT without stalling and thats why it tows so well for me.

Huh? Explain: "the engine would pull to 350RPM @ WOT"

[Jake Raby]

Meaning I could load the engine all the way down to 350 RPM without it stalling or bucking and stil achieve a power reading... Heck the torque plateu of the engine in my company Bus that I am referring to begins at 1,000 RPM.

I generally do not need first gear to take off at traffic lights and etc unless I am towing...

[Brandon314159]

Meaning I could load the engine all the way down to 350 RPM without it stalling or bucking and stil achieve a power reading... Heck the torque plateu of the engine in my company Bus that I am referring to begins at 1,000 RPM.

I generally do not need first gear to take off at traffic lights and etc unless I am towing...

I can confirm this...amazing what it can do down that low. I try to keep the engine spinning where oil pressure is decent (1 bar +) and after working at a clutch shop, I still start in 1st gear. :)