I'm lean at 3.5% CO ??

[1980SC]

Hey folks,

I just got back from the dyno so I could see how my mixture is doing. Glad I did. I set the mixture at idle to what I've read was on the rich side, 3.5% CO. Nope, I'm "piston burning lean" as the guy running the dyno said. I wish I could post the graph here, but I don't have a scanner. I got a whopping 155hp with my '80 euro 3.0L.

This is at W.O.T. :

At 3,000 rpm I'm to 16:1.
By 6,000 rpm, it's slowly richened up to 13.5:1.
Most of the graph, I'm leaner than 14:1.

The car is a stock 1980 Euro SC. None of that O2/frequency valve stuff and no cat.

I'm thinking it's my warm-up regulator. Although I'll be calling it a control pressure regulator from now on. I've done some reading, and it does more than just help when the car is cold. According to Bently, it also enriches the mixture during acceleration via a vaccum line. Perhaps it's dead?

Since when my car is cold, it takes several starts before it will actually run, I figured it was the W.U.R., but just haven't gotten around to fixing it yet. I didn't think it was all that important.

Am on the right path? Any other suggestions? I checked that the sensor plate moves freely, and it does. Richening the mixture screw even more only made the car not want to idle anymore. That didn't help the mixture while accelerating on the dyno. Should I be losing sleep while worrying about what my pistons look like now $$$ ?

Thanks for any input,
Rob
1980SC (Euro with 8.6:1 compression)

[makaio]

Take it from me, you need to test the fuel pressure with a gauge. I learned this the hard way, after I shelled out the money for a new WUR.

I would recommend reading "How to tune & modify Bosch fuel injection by Ben watson". It gives all the proper pressures for the model years and systems.

[wckrause]

Yes, the WUR should enrichen the mixture when WOT. I've never seen any numbers or method for testing that function of the WUR though. Also, in line with one of the vacuum lines is a device called a thermovalve. It is used to aid cold starting by tricking the WUR into acting like WOT when cold. Perhaps that thing is stuck closed, and it is always in that cold start mode. Just something to check.

[stlrj]

Wait a minute, aren't these engines supposed to run stoichiometric mixtures 14.7 to one or leaner?

That's what all my Bosch books are telling me, so what's the problem?

Joe

[1980SC]

Um, no. With the O2 sensor unplugged (I don't even have one) they should be running about 14:1 to 13.2:1. Or so I've read. If it were at stoich, it would be too lean, and mine at 16:1 is way too lean !

I've done some searches here on W.U.R.'s and I may be able to just "adjust" mine once I get a CIS pressure guage.

Thanks for the responses guys.

- Rob
1980SC

[amatow]

I have reasonable experience with this fuel injection system on VW's. I suspect a vacuum leak. The engine cannot adapt to even relatively small leaks. Several small leaks can add to enough to lean the engine. Look at every vacuum line for small cracks at the ends. If there is enough slack, a ¼ inch may be cut off and then repositioned. Even the oil filler cap can cause a vacuum leak.

[1980SC]

Yes, good point. I should have at it with a can of carb cleaner to help find any leaks. I'm planning on buying this CIS fuel pressure tester from JCWhitney.

http://jcwhitney.com/item.jhtml?ITEMID=1939&BQ=jcw2

That should help let me know if it's an air leak, or a fuel pressure problem. Hopefully.

[emcon5]

Originally posted by 1980SC
I got a whopping 155hp with my '80 euro 3.0L.

Is that 155 at the wheels? Weren't ROW SC's in 1980 rated the same HP as US cars, 180DIN, or 175ish in US numbers? Figuring 15-20 percent drivetrain power loss, 155 at the wheels sounds about right.

Tom

[1980SC]

My '80 Euro should have slightly more HP than the US version, supposedly 188 HP. I've read of stock SC's getting around 170-175 at the rear wheels, so I was expecting a little more than 155. Actually at the higher rpms, the engine is just starting to get into a normal fuel ratio. It's the mid range that is really suffering. It's not getting enough fuel, hence it's not making any power. I had been wondering why the motor felt so guttless in the lower rpms. I thought these engines were supposed to be somewhat torquey.

I'm not really concerned with what the peak HP rating winds up being, I'm much more interested in keeping the cylinder head temperatures down by running the correct mixture.

Those long pulls at full throttle uphill through 3rd gear entering the freeway that I'd been enjoying everyday on the way to work were probably not to good for the engine.

[stlrj]

So how many years has it been running that lean?

If it came that way from the factory, then 20 years should have been time enough to have burned several holes in all your pistons by now and the fact that it still runs is a mystery to us all.

Personally, though, I wouldn't loose too much sleep over this or whatever your dyno man has to say.

Joe

[rfng]

I wouldn't worry too much about the dyno hp numbers. A lot of dyno show inflated/uncorrected numbers. It depends on how it is set up. I've seen engines dyno at over 600 hp on one dyno and then two hours later on a different dyno show 425.

The really test is how the car performs. You'll see guys claim big horsepower with slight modifications, and if you have played with enough engines you know it not that easy. Even manufactures have trouble increasing horsepower from year to year. If they could gain 30-40 horsepower by just adding a new exhaust system, they would save a lot of time and effort, but they change the cam specs, the intake runners, redesign the exhuast, increase the displacement and raise the compression to gain less than what some of the performance manufactures claim.

From my experience there is up to a 30% error rate from dyno to dyno. You should always use the same dyno, so the error/correction rate remains the same and you can see proportional numbers.

Just look at some the performance books and catalogs claims. They show a set of SSI producing between 9-22 hp notating depending on your modification, but they dont tell you that the 22 came as a result of a new muffler, higher compression pistons, and probably new camshafts.

Horsepower is a lot harder to make, than a lot of manufactures would want you to believe. If they only claimed a 9 horsepower gain and you had to spend a couple of thousand dollars to get it, you probably wouldn't buy their product.

This is also true for a lot of dynos, if your car performs badly at the dyno, you will probably not go back. But if it performs well, then they just gained a valued customer.

As for the 16 to 1 fuel mixture, I would guess that this was the reading done in 1st gear. CIS is slow to react to quick changes in the air flow. Especially in 1st gear where the rpm rise much quicker than in other gear. I would guess that your fuel numbers which were better than the 14.7 to 1, were measured in 3rd gear, where the air flow plate as time to react and richen the mixture.

[1980SC]

Joe,
I honestly hope you're right about it being nothing to worry about, but I'm still going to get the mixture correct. I seriously doubt this engine has been this lean for 20 years. It would have already been rebuilt by now. This car sat for a while before I bought it about two months ago, so that is when I'd suspect things like the W.U.R. would have gotten stuck or clogged up.

rfing,
I know exactly what you are talking about with dynos and HP claims. I have no intention of modifying the engine for more hp, I just tested it so I could see what the mixture was throughout the rev range. I figured it wasn't running correct. The numbers I quoted were all in 3rd gear. 16:1 full throttle in 3rd gear is bad. I will not ignore that. My fuel ratios only got to 14.7:1 or richer shortly before redline.

I will be doing fuel pressure tests, playing with the W.U.R., and checking for vaccum leaks for a while until I get the mixture richened up. I'll post the results.

Thanks for the input,
Rob
1980SC

[john walker's workshop]

the warmup regulator adjustment only affects the warmup period. about two minutes worth.

[1980SC]

Ahh, thanks John. I thought the adjustment may have been able to help with the vaccum controlled full throttle enrichment function. I may need to replace it then. Or it could be something entirely differnent. We'll see.

You answered a question I had about the gearing in my 915 a few days ago, and I had made the comment that it felt like 2nd was too tall. Now I know why it feels like that. My engine just isn't getting enough fuel until higher rpms. Makes the car feel very guttless.

-Rob

[john walker's workshop]

just a thought, but you CAN richen the midrange a bit by adjusting the shim pack in the fuel distributor check valve. i do this all the time to get cars thru emissions. it works backwards than what you might think. adding shims leans it out. and VV. the control pressure regulator (WUR) is ultimately responsible for the fuel mixture. it controls the sensor plate lift, and it's pressure is a byproduct of the higher system pressure. so the higher the control pressure, the more resistance against the movement of the sensor plate, so the plate doesn't lift as much, which is directly related to how much fuel the fuel distributor puts out. so basically, dropping the system pressure will give you more fuel midrange. if you have a CO sniffer in the tailpipe you will see the difference.

[1980SC]

Thanks for the tip John. I had read about removing a shim or two in my Bently book, but figured I shouldn't mess with with it. Well, I just removed the two spacers that were in there, and it certainly made a difference when the car is cold. It no longer bucks and kicks as hard while accelerating. Once warmed up, I'm not sure if it made much of a difference. I'll be able to tell more when I can get a pressure guage on it.

These Euro cars can be a bit of a pain. Bently lists four different fuel distributors for U.S. model SC's, all with different control pressures. My car, of course, has a different fuel distributor. Bosch part # 0 438 100 077. Any idea of what control pressure I should shoot for?

Thanks,
Rob
1980SC R.O.W.

[john walker's workshop]

CIS control pressures should be between 3.4 and 3.8 bar when warm. so shoot for the lower pressure to richen cruise and mid range. moving the pin in the regulator body in or out, richens and leans (respectively) the warmup mixture, but has no effect on the warm mixture.

[1980SC]

I finally got a fuel pressure guage to test my pressures. The system pressure is 76 psi, and the control pressure is, well 76 psi. No difference if the valve on the guage is open or closed. Why is this so? Testing was on a cold engine which wasn't running. Started the car, and got 76 psi once again. Hmmm.?

I'm assuming this means my WUR is doing nothing.

The resistance of the WUR heating element is 9.5 ohms.

John :
I'm confused as to why I removed the shims from the pressure relief valve. With the 2 shims I get 76 psi system pressure, with them removed I get 70 psi. Isn't less system pressure leaner?

Thanks,
Rob
1980SC euro

[1980SC]

Okay, I just took my frustration out on the WUR pin, and beat the crap out of it. Now my control pressure is around 50psi !! That makes me feel a little better.

[john walker's workshop]

read my second to last post again. (and your gauge must be tits up). or it's hooked up backwards.