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AFR issues on stock LH2.4

MrKrabs

New member
Joined
Aug 26, 2016
Location
France
Hi there,

First of all, my car:
1997 940 Turbo B230FK

Only modifications:
-TD04 15g @ 8 psi
-3 inch turbo back exhaust
-KL Racing 60mm intercooler

Stock 016 MAF, 6 months old Mustang 5.0 Bosch lambda sensor (same sensors) and injectors. No chips in fuel or EZK.
Brand new fuel filter and gapped BPR7ES plugs.


Now, my issue.
My AEM wideband gauge is showing me problematic AFR's at certain points of the rev range. When cruising and light load it's always at 14.7 as it should, but under boost it will first be running too lean, as low as 13.7 when really low in the rev range (around 2000 rpm). It will then start to progressively richen up as the revs climb, spending most of it's time in the 12.5/11.5 sweet spot. But when approaching red line, it will once again progressively richen up untill hitting low 10's, sometimes even in the 9's at 6000 rpm.

Here is a video to illustrate the issue; you can see the tach and AFR gauge simultaneously. This is a 3rd gear pull, cruising at 2500 rpm then floored to redline.

https://youtu.be/b66JVedyiEY


I don't know how a stock LH2.4 car is supposed to run AFR wise, but I don't think this is normal as it's not safe for my car.
What do you guys think? Boost leak somewhere? Crappy MAF or lambda sensor? What could be causing this?
 
I'd try another AMM or MAF as you call it. Got an extra? Where did you put the wideband sensor? Did you have another sensor bung welded into the downpipe or ?
 
Hi there

Sounds like pretty stock fuel map that one, nothing wrong with it other than the fact that Volvo had some absurd ideas while programming them.
Best approach get an Ostrich and make your own map or ditch LH all together and get the new Maxxecu mini.

YS
Jaybee
 
What Jaybee says. Mine was just as you describe on stock LH.
You have to add fuel in the 3 highest load fields from 2-3.5k rpm and take a lot of fuel out on top.
Stock map is absurdly rich there.
Took me some tries to get a decent fuel map.

Do you have a chip burner?
 
9:1 afr...how does the engine run? Most engines will barely run at that AFR.

It's rough, really doesn't like revving up there.

I'd try another AMM or MAF as you call it. Got an extra? Where did you put the wideband sensor? Did you have another sensor bung welded into the downpipe or ?

Oops so it's an AMM, wasn't sure on that one. I have a working spare I'll try real quick, just to make sure.
The wideband sensor is just above the second bend of the downpipe, the one making the exhaust horizontal once more. Welded a bung there, no leaks.

Hi there

Sounds like pretty stock fuel map that one, nothing wrong with it other than the fact that Volvo had some absurd ideas while programming them.
Best approach get an Ostrich and make your own map or ditch LH all together and get the new Maxxecu mini.

YS
Jaybee
What Jaybee says. Mine was just as you describe on stock LH.
You have to add fuel in the 3 highest load fields from 2-3.5k rpm and take a lot of fuel out on top.
Stock map is absurdly rich there.
Took me some tries to get a decent fuel map.

Do you have a chip burner?

Damn so it's known to be this bad from the factory? I almost can't believe it and still thinking about what could be wrong with my car haha. But hey, if knowledgeable people say this is how a "healthy" stock LH2.4 car runs, then it's probably true... Crazy.
I'll be getting a custom chip made for it for bigger injectors, just wanted to make sure I had a solid foundation before building upon it.

Out of curiosity more then anything, what triggers LH to switch between open loop and closed loop fuel trimming? Which one uses mainly the AMM or the lambda sensor?

In any case thanks for your help! Wouldn't say no to others confirming that this is just a stock LH map, just for that extra bit of reassurance...!

Cheers
 
Out of curiosity more then anything, what triggers LH to switch between open loop and closed loop fuel trimming? Which one uses mainly the AMM or the lambda sensor?

Hi,

LH has a table with a switchover load point for a given rpm. Below that load it is in closed loop(using the o2 sensor to stabilize AFR to 14.7), and if load is higher than the table value it switches to open loop and it uses just the maps (load signal vs rpm).

The load signal is calculated from engine speed, injector constants and AMM signal if I recall correctly.
 
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What are you using for an air filter? I found that a cone filter directly on the AMM/MAF made the car run rich. A 90deg bend with a 3in straight section and then the filter. That raised AFRs in boost to 11-11.5:1. Food for thought.
 
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What are you using for an air filter? I found that a cone filter directly on the AMM/MAF made the car run rich. A 90deg bend with a 3in straight section and then the filter. That raised AFRs in boost to 11-11.5:1. Food for thought.

Um oops?
That's exactly what I have atm haha, a cone filter straight after the AMM.
I'll work on adapting a 90? before it then.
Thanks alot for the info!
 
I managed to get hold of a gold box & fitted it with a TLAO chip. Using the Deka 60lb injectors with an 012 AMM it idled fine, but like yours, it was rich to the point of bogging at about 4500 rpm. I put the old 016 AMM in a 3.5" tube and it worked beautifully - I was really happy.
I had a 3" exhaust system on and added a CAT to make the car more legal. When I started it after adding the CAT, at idle it would rev up to 2000 rpm, stay there for a couple of seconds & drop again -it was still fine at high revs. You could feel this when driving slowly as well. Don't know why adding the CAT would do this. Tried another 016 innards but same result. Went back to the 012 AMM & it idled perfectly - still bogged at 4500rpm though.
Still using the 012 AMM but I've now put a 10K pot between the AMM & ECU. When I turn the pot to reduce the signal so that AFR's are about 12.5 at full boost I get the hunting idle again! Beginning to think this is just the way this ECU is.
I think LH2.4 can learn great for some things - less so for others. I did not want to get an osterich/chip burner, but it may have been easier and cheaper to have done so at the stage you're at.
 
it's a stock system, it's not making power at 6k anyway. But all of this is consistent with stock programming. It's not particularly odd, it's an early catalyst protection scheme. if yall think that's crazy you should see some of the stuff the gm engineers have been doing with their oem tunes.
 
I've since then fitted a 90? before the AMM, didn't really change much. Now have a fuel chip fitted matched to my 383cc Sierra Cosworth injectors, and still running deep in the 10's AFR wise after ~4500 rpm. What could be causing this?
My idle when warm also dropped to about 400 RPM. What's to blame, injectors or fuel map?
This is making me want to invest in a standalone.
 
What exactly has been changed in the map?

If it is just the injector constants, then the top part of the map will still be very rich (like stock).

Idle is strange... AFR at idle?
 
Quoting from the tuner: "boost fuel cut limit disabled, much better fuel trim curves, slightly changed Lambda tip in tip out points and slightly less overfuelling on start up"

Otherwise my idle is 14.7, no issues there or at cruise.

Is it possible if the throttle position sensor isn't "clicked" into place after letting go of the throttle the idle control valve won't open and cause super low idle? I'm not familiar how the idle circuit works, but I tried re-adjusting the idle screw to where the throttle switch barely actuates. If the cable is a little sticky I feel like it wouldn't click the sensor.
 
Idle/cruise being 14.7 has nothing to do with the map. I'm going to say go back to your tuner with feedback. I was fed up with results I was getting with chips from other people, too much variation in setups, so I bought and Ostrich and haven't looked back. One day might still go MS, but the Ostrich provides a lot more flexibility than you'd expect.
 
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