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940 B230 NA with lambda 1,4

B

Berrie

New member
Joined
Apr 6, 2018
Hello folks,

I'm new to this forum, but have a question for you. A friend of mine has a 940 with B230 (F) with 531 head. He doesn't speak english, which is why I pop in. I have some knowlegde of the LH2.4 but hope you guys have a lot more :-)

His B230F ran okay, but was worn. He put in a rebuild engine and while he was at it, put in a H-cam (which is the cam from the '79-'80 B23E engine - about 270 degree duration) and a mildly ported head (also 531) and raised the compression ratio a bit.

The cars makes good power, but ever since the conversion/upgrade the engine runs lean below 2000 rpm. Lambda about 1,3-1,4. Idle fluctuates, and while cruising the cars has some lean hick-ups. Above 2000 rpm it seems to run fine at lambda 1,0 (lambda values measured stationairy at a workshop though - so not under load).

My first thought: air / vacume leaks. He's checked and says there aren't any. What would be the next steps to check? Lambda sensor was replaced a few month back, so unlikely the problem. Could the H-cam be too much for the LH2.4 to cope with?

Thanks. Your help is much appreciated.

Berrie
 
Yes, I would think if there isn't any other issues like a vacuum leak or low fuel supply. Then the tune is far off. You could try chipping the LH fuel and ezk spark boxes to better match a performance cam. Check in with our member sbabbs or thelostartof for chip info. I got mine from sbabbs and it made a great improvement on my 93 wagon.
 
Lambda = AFR/Stoich, or AFR = Lambda * Stoich, so AFR = 1.4 * 14.7 or

AFR = 20.6 :omg:

If there's a misfire, lots of O2 is leftover and the wideband O2 gauge thinks the engine is running really lean.

Any diagnostic codes posted for either ECU or EZK after it's been running a while?
 
dl242gt:
Yes, the tune seems to be far off. But I wonder if it's the ECU just not able to cope with a mild street performance , or it's a fault somewhere else in the system. The H-cam is still relatively mild, so I would think it wouldn't be any problem for the LH2.4 I will try contacting the two chip members, to see if they have any experience on this.

bobxyz:
Yes, that is AFR 20.6 So indeed the O2 sensor will sense the engine is running lean, but the problem is why the ECU isn't simply injecting some more fuel to get a better AFR. No fault codes in ECU/EZK.
 
Here's 2 shots of the exhaust analysis. Note the high Lambda at low rpm. And correct lambda at higher rpm. It's only occuring below approx. 2000 rpm.

Edit: I just noticed the HC (unburned fuel) is very high too at low rpm. So maybe the ECU actualy is injecting more fuel already, but something else is causing an uncomplete burn?

<img src="https://image.ibb.co/cHjFuH/890.png" alt="890" border="0">

<img src="https://image.ibb.co/bzjgZH/2500.png" alt="2500" border="0">
 
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I got similar emission issues with my 940 with B230FK. My O2 is over 16% and HC between 100-200 depending RPM. I got a leak between cat and downpipe. That is maybe because AFR from the engine is right, but air leak leans it too much, and cat doesn't burn HCs.

Ordered new downpipe and three piece clamp for cat.

Nice AVL analyzer, BTW, I got similar at work.
 
Stock LH 2.4 won't behave with the H cam at idle/really low rpm
You need more ign advance at idle , and a bit less up top
 
viking20 said:
Stock LH 2.4 won't behave with the H cam at idle/really low rpm
You need more ign advance at idle , and a bit less up top
Click to expand...
That would actualy amaze me, but I'm beginning to think that too. Although I also hear people saying H-cam + LH2.4 will work. Is it your personal experience? Where the symptomes the same as in this case?
 
Where was the O2 sensor placed in the exhaust system when these tests were run? If it's near the tailpipe, these readings may be normal. Our race car, which runs a full exhaust less cat converter and has a wideband at the end of the downpipe, will show 17:1 or less at idle with a K cam., but as the rpm comes up the ratios return to what you would expect.

First thing I would do is go back and cover all the mechanical bases. Factory cam gear? Budget adjustable ones are sketchy. Check for vacuum leaks. That type of stuff.

More ignition advance will help, but I would want you make sure you aren't covering up some problems first.

If it's undriveable, then I'd agree there's something wrong. The lean "hiccups" would be concerning.

A few more questions. Does this engine have increased compression ratio? Were the injectors cleaned and flowed?

There may be a slight exhaust leak, pulling air into the exhaust stream, causing the O2 to demand more fuel, and what you think is a lean condition may be overly rich?

With the increased cam overlap in even the larger factory cams, the MAF sees a lot of "pulsing" in the intake tract, causing some kinda crappy fueling issues at low speeds. It's exaggerated as the cam durations get longer with aftermarket cams. We've observed this on the dyno, and I can tell you from experience that the power curve on our engine is better with a K cam than an H, both tuned. It's VERY close, but the K is better.
 
shoestring said:
Where was the O2 sensor placed in the exhaust system when these tests were run? If it's near the tailpipe, these readings may be normal. Our race car, which runs a full exhaust less cat converter and has a wideband at the end of the downpipe, will show 17:1 or less at idle with a K cam., but as the rpm comes up the ratios return to what you would expect.
Click to expand...
Yup, I know what you mean. O2 from the outside air mixes with the exhaust fumes and disturbes the reading at idle. The garage analyser however has a very long probe to eliminate this. The exhaust itself hasn't got any leaks.

shoestring said:
More ignition advance will help, but I would want you make sure you aren't covering up some problems first.
Click to expand...
Me too, and this doesn't seem like ignition alone.

shoestring said:
A few more questions. Does this engine have increased compression ratio?
Click to expand...
Yes, 10,4:1

shoestring said:
Were the injectors cleaned and flowed?
Click to expand...
Cleaned yes, flowed no. It would be quite coincidental if the clogged injectors would occur at the same time the engine+cam was swapped though. Still worth a look however.

shoestring said:
There may be a slight exhaust leak, pulling air into the exhaust stream, causing the O2 to demand more fuel, and what you think is a lean condition may be overly rich?
Click to expand...
It could indeed be overly rich. Have a look at the 2 pics of the analyses. The HC is way up too. So lots of air in the exhaust fumes but also lots of unburned fuel.

shoestring said:
With the increased cam overlap in even the larger factory cams, the MAF sees a lot of "pulsing" in the intake tract, causing some kinda crappy fueling issues at low speeds.
Click to expand...
The overlap will indeed increase reversion in the intake. Is there a way to make the MAF less sensible to this?

Thanks for your input!
 
The overlap will indeed increase reversion in the intake. Is there a way to make the MAF less sensible to this?
Click to expand...

Funny, I've never thought about this. I have to wonder if you could put a resonator between the throttle body and MAF and have it affect reversion. I know manufacturers use them for sound (noise), but perhaps they run a double duty. This is interesting and deserves research. Like I said, my experience is with our race car, so we have a lot of advantages over a street car that help mask those issues: lower weight, more aggressive gearing, higher compression, high (3500+) rpm operation, etc. I know my street car, a '91 245 with an A cam, exhibits some poor idle characteristics. They are easy to ignore, but that doesn't mean they aren't there. If you look at the cam specs for the cams that were installed in LH2.4 cars (M, T, VX), they all have pretty low overlap numbers, undoubtably to maintain a factory idle quality.

It sounds like the combination is reasonably thought out. Did you measure the compression ratio yourself, or are you relying on what "should be"? If you milled the head to up compression, I'm sure you're aware that cam timing is retarded 1 degree per 0.010" you mill it. A good adjustable gear to bring it back to straight up may help, but it's not going to be a silver bullet by any stretch of the imagination. Check for errors, chip it (do you know the EZ116K advance/retard pinout cheat?).

Without being there, that's about all I can think of. Good luck, I'll be watching this thread.
 
shoestring said:
It sounds like the combination is reasonably thought out. Did you measure the compression ratio yourself, or are you relying on what "should be"? If you milled the head to up compression, I'm sure you're aware that cam timing is retarded 1 degree per 0.010" you mill it. A good adjustable gear to bring it back to straight up may help, but it's not going to be a silver bullet by any stretch of the imagination.
Click to expand...
The engine is basically blueprinted, so compression ratio etc are all measured. A shorter 122 teeth timing belt is used and an adjustable cam gear is fitted to compensate for the offset. My friend (who lives far away, form me, so I cannot check thing personally now) will play with the cam timing a bit next week to see if that makes any changes to how the engine idles. Imho some cam advance would decrease the reversed intake pulses, so that might help (still assuming everything else is okay). Ofcourse I'll post the outcome here.

shoestring said:
do you know the EZ116K advance/retard pinout cheat?
Click to expand...
No I don't, how does it work?
 
There are 2 empty sockets in the connector, #18 and #19. You can put terminated leads in them and ground them in different combinations to retard or advance the entire ignition map a little. You may be able to scrounge a couple leads off of a spare harness if you have one, I use premade ones from BMW, though I cannot recall the part number. I'll try to find it.

Found it: 61 13 0 007 437. I'm sure there's a Volvo number for this, but I worked at a MINI store for a long time, and these are absolutely correct.

Anyway, if you ground:

#18, it retards the map 3 degrees.
#19, it retards the map 6 degrees.
Both #s 18 and 19, it advances the map 3 degrees.

It does not change the idle speed timing, that remains at 12 adv.

I put ring terminals on both wires and ground them to one of the 8mm bolts that hold the firewall block-out plate in place.

3 degrees isn't much, but it's something you can do in about a half hour and it does do SOMETHING.
 
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