marlinspike

So, I don't have a 928. However, I'm told you 928 people have CIS K-jetronic, just like me. I have a Mercedes (5.6 liters, 10:1 pistons, lumpy cams). Thanks to the UTCIS-PT that was installed and tuned I no longer have mixture issues; however, power was less than I wanted (albeit it very very flat).

It was noted that my manifold pressure never exceeded 0.9 bar. We're thinking the air restriction is the metering plate. Any way to solve this? I feel like I'm leaving power on the table simply by not having enough air get into the engine, but the dyno guy said my air filter housing and the related intakes seem like that wouldn't be the choke point.

RicerSchnitzzle

Not the metering plate,if you have the UTCIS-PT as you can drop control pressure to get more fuel. If you are tuned for A/F across all rpms and vacuums you can do a couple things. It's doubtful the metering plate is bottoming out or you would be lean on top. The metering place can flow more than the throttle body, so it shouldn't be the restriction. At least in a 928. Same metering plate assembly, different throttle bodies.

1. Make sure the metering plate is adjusted correctly. A little lithium or graphite grease at the pivot points will help.
2. Larger Throttle Body.
3. If you're lean up top you can raise system pressure and adjust for idle and cruise with the UTCIS-PT. Take the pressure regulating spring out of the CIS distributor and run an inline fuel regulator after the distributor on the return line. You can then run as much pressure as your pump or pumps will support.

You should be able to map your fuel on the UTCIS-PT and see if your maxed out up top. What is your A/F mix at WOT and 0.9bar?

BTW I never get to 1bar at WOT.
I am modifying a 90mm throttle body from a Q45 to fit my Shark.

Oh and I think there's only one guy here with the UTCIS installed so far. Mine sits on the shelf waiting...

marlinspike

Hmmm, so maybe it's the throttle body that's the restriction. We achieved the A/F ratio for max power with control pressure to spare.

I would recommend installing the UTCIS-PT you have. Mine went in today. With my cams, being able to tune made quite a bit more power, plus idle now has an appropriate mixture as does full throttle (as opposed to before when I was shoving liquid gas out my exhaust pipe just to get it to run okay at top end).

Here's the dyno graph and A/F. Blue line was the last run. Now that I look at it a second time, I wonder why he didn't richen up the 1600 to 2200rpm range? I guess I can just do it with my laptop, but it would have been nice to do it with the benefit of the dyno.



I've got the later UTCIS-PT, the one that taps into the rpm signal for the tach rather than uses a magnet for getting the rpms. It's so that later I can go to an MSD. One thing I'll note is they need to put more adjustment in it, at the max adjustment (I guess it's a resistor in there) mine is still like 100rpm off, but I guess that doesn't matter as long as you know that.

Also, FWIW, I'm 13:1 at idle and 13.7:1 cruising in 4th gear at 60mph.

marlinspike

Oh, and ignore the torque hump at the start, it's an auto transmission.

RicerSchnitzzle

Can't wait to put mine in. My engine is in the process of going in the car, see pic in sig. It;s been 3/4 done for a couple weeks. One man doing a two man job. I plan on getting it running with the new cams and MSD billet distibutor before switching to the UTCIS-PT. Figure if I change too much at once and things go south, I won't know what the cuplret is. I have been running the MSD 6AL for about 2 years now. It's great.

If you get a LC-1 or LM-1 you can log A/F during real world runs for even better tuning.

UTCIS-PT seems great, gives just about the same control over A/F as later systems, with out need for a computer degree. Only thing it won't change is timing.

marlinspike

I was thinking about getting the 6-AL2 Digital Programmable, then welding my star wheel in place and plugging up the vacuum advance to handle the timing side of things, but I somehow doubt that's where I'm leaving power on the table. With 5.6 liters and 10:1 compression, there's got to be power that I'm leaving behind.

I wish those wide-bands weren't so darn expensive. You would think it would be simple to make something that tells you the mixture and logs the data to a laptop you supply. My setup is pure CIS, no E (no O2s, nothing, though I do have O2 bungs for the sake of tuning).

Ben

I fitted a 5.6 euro 'ECE' engine into my 500SEL on old fasioned CIS too. I'm using the CIS from the old 5.0 engine, and with only the adjustment to the baseline CO, i'm not down on power at all! Are you using the original CIS that came from the 380se?
There are a few parts from the 5.6's CIS-E that you should have retained. The main thing I remember was that the throttle body is larger, even larger than the US 5.6, and also the special exhaust headers and downpipes. The exhaust system for the 5.6 is also a larger diameter than on the 380's and 500's by about 1/4".

marlinspike

Hmmm, I'll have to look into the throttle body. I think I have a US 560 throttle body. Do you know what the diameter is of the ece throttle body? EDIT: I just checked the Mercedes ECE. The US 560 lists the same part number for the throttle body as the ECE 560.

I've got the tri-y headers going to a custom exhaust made by a shop that makes exhausts for NASCAR and NHRA cars. My downpipes are standard euro 560 downpipes with the compression bends, but the guys at the dyno shop said since it's not like I'm making 500hp, they're not likely to be an issue.

My cats are shot from an engine that burned oil and ran rich, but they've had about 6500-7000 miles on this good engine to clean out (though, there was a lot of rich running at idle until installing the UTCIS-PT) so I'm not sure how much of an issue that was. It feels like a hurricane out the back of my car, so they can't be too clogged up.

I'm using CIS (minus O2s and all the other electronic adjustments, that's what the UTCIS-PT is for) that came on the gen-1 cars, with the addition of a euro 500/560 fuel distributor.

Do you have dyno charts for your engine? My problem is these numbers are what an ece 560 should put out. I have basically an ece 560 + cams, so I was expecting more. Then again, maybe this 10% ethanol gas is the problem.

I am using the 380 ignition, set for 10 degrees advance at idle. You think that could be a problem? I know I have to gap the plugs to .032" (.8mm). Any bigger and I'll get some missing. That's why I wonder if the MSD will be worth it to me since I'll be able to widen the gap to .055".

I will say this. It doesn't feel down on power, it was just getting on the dyno that maybe say "dang it." I know I'm faster than my friend's 2000 MB S500, even with only 4 speeds and a 2.47 rear end.

marlinspike

Also, Ben, while I have your attention, if I'm making a turn at speed (say on the highway turning to match the slight curve in the road) and I hit a gap in the concrete, the rear end wants to go sideways (mimicking oversteer). Is that my subframe bushings?

Ben

If the US and Euro throttle body are the same, then that obviously can't be your problem them. Exhaust wise, mine is a stock Euro 560 system (think the pipes are 2.25").
My installation differs to yours because I dont have any emissions equipment, and the car never came with any. That includes any O2 sensor, cats etc. The car is a first gen euro 500 SEL, and I didn't want to complicate things with using the CIS-E from the 560's engine. I even removed the EGR stuff, because it wasn't working and was causing a lumpy idle.
I'm also using the first generation ignition system, with the exception of the coil... which i'm using the second generation 560 version. The spark was weak with the old coil, the engine struggled to rev, and the exhaust hydrocarbon levels were sky high. Now it pulls strongly to the redline. The workshop manual says only to use the coil designed for that ignition module, but i've been running it this way for about 2/3 years with no problems.
I can't remember the exact figure that the plugs are gapped to, but its whatever the book says is correct for a 560, and ignition timing it set to what the book states for a euro 500.
Like I said in the previous post, the only adjustment I needed to make was to tweak the fuel distributor idle CO setting to 1.5%. We are allowed upto 4% here for emissions testing, but there is no point in going that high, the car would be pumping raw fuel out of the tailpipe!
I haven't actually had it on a dyno yet - although using the butt dyno, it feels strong and runs great!

If your car is a US 380, I think you'll probably have a slightly different suspension setup at the rear compared to mine... I have the aluminium rear trailing arms with different geometry. It does sound like its the subframe bushes at fault though, my car does it. I installed K-Mac adjustable rear trailing arm bushes to correct my negative camber issues, and I wish that I changed the subframe bushes too.

marlinspike

Yeah, I have the aluminum rear trailing arms too (the car is a June 1985 build, so it has some upgrade stuff lol), with the non-hydraulic suspension.

I don't have O2s but I do have high-flow cats. The dyno guy did think they were shot from rich running (with the lumpy cams before the UTCIS-PT it had to be rich round town to be ok under full throttle). Maybe I'll try replacing them with straight pipe and if that makes a big difference I know I need new ones (when the exhaust was built I had the cats flanged for quick removal for track days).

I do still have the EGR stuff but it's working.

You might be onto something with the coil. Could that be why even when the A/F ratio is correct according to an LM-2 plugged into a downpipe my exhaust still smells dirty? You think I can just use an MSD Blaster 2 to get a jump-start on my MSD conversion that I'm still saving up for, rather than wasting money ona 560 coil as a stop-gap?

Lizard928

if you are using a stock cap/rotor design I would not recommend running greater than a .028 plug gap. Anything more and you spark will be weakend, and it will destroy the cap and rotor in a quick order.

Also if you are wanting more power consider a swap to a standalone EFI system like Megasquirt or VEMS.

marlinspike

Hmmm, why .028? The factory spec is .032". I did accidentally have it at .044" (unbeknownst to me the gapper I was using was way off) and gapping them down to .032" (on a new gapper that I checked with my calipers) did make it a lot better.

Lizard928

that is the largest I have ever heard of for being a factory setting on a cap and rotor car.

RicerSchnitzzle

He was talking about larger gap with the MSD ignition system. All you have to do is solder over the resister in the rotor to get full power. I've run my shark this way for two years with large gap. No misses, no issues and cap & rotor still look like new.

With the UTCIS_PT no need for a megasquirt. He can already program A/F across any rpm and vacuum level. Good enough for most. CIS is a far better system than most folks give it credit for. HP limits are only set by system pressure and control pressure. If you can get the air in, you can set your CIS to deliver the fuel. With $150 LC-1 and a laptop, you can get real specific.