Let's talk about Air Fuel Ratio, AFR, rich mixture on B230FTs


Why does this site exist? Sometimes I am confronted with claims that my chips are running way too rich in the upper load range. Fortunately, these complaints are in the low single-digit percentage range.

When we talk about AFR values ​​in connection with the LH2.4, the first thing to realize is that the LH2.4 only takes AFR values ​​into account at idle and at partial load. When it comes to chips and tuning, we're talking about the high-load range. There, the mixture composition is determined solely by the parameters of the air mass meter, injectorsize and map. This is only influenced to a small extent by the adaptation in the partial load range.

I have programmed the map in my chips so that the mixture is not so rich in the low and medium load range. In the upper load range up to full load, the map is designed so that the mixture should be in the range 12.0:1 - 12.5:1. In most cases this is the case. Now there are people who say that a turbo must have a richer mixture than 12.0:1 at full load. I can only disagree with that, everything below 12.0:1 only serves to cool the engine internally and does not lead to more power, on the contrary, everything below 12.0:1 actually leads to a loss of performance because there is no longer enough oxygen for an efficient engine Combustion is present. So why all the talk about it having to be richer? It's very simple: If you don't manage to tune an engine correctly, i.e. to prevent it from "burning out" at full speed, then you compensate for this with a richer mixture to be on the safe side. But you can't complain about performance losses at the same time, because there is a direct connection between performance and AFR values!

If you are already in the vicious cycle of the engine running extremely rich due to poor tuning or incorrect chips, it is difficult to break that cycle unless you are very analytical.

If the engine runs too rich, you can do whatever you want. The engine usually responds to attempts to get more power with an even richer mixture and constant or falling power.

Why this? You first have to realize the fact that a mixture that is too rich costs performance! For turbo engines there is a range which is slightly less than 12.5:1. A turbo engine should not run leaner under full load, but neither should it run richer than 12.0:1. You should also keep an eye on the indirect consequences for the engine if the mixture is permanently too rich. In the medium term, a mixture that is much too rich will of course affect the engine, the mixture that is constantly too rich can, for example, wash the oil film from the cylinder wall, and I don't have to explain what metal does to metal, but it can also affect other components, for example the catalyst.

Many people make mistakes when tuning a turbo engine. It is assumed that the power will come naturally if the compressor and injectors are large enough. Wrong thought! This is exactly how you lay the foundation for the failure of the project!

Let's take a production engine and not change anything to the cylinder head, cam or intake, as many do. Instead, you invest your money in a blow off valve (important for the noise level), colorful intake hoses, huge intercoolers, monstrous turbochargers, thick injectors and of course not forgetting the obligatory noise-causing sports air filter and sports exhaust, preferably in 4" and without a silencer, catalytic converter anyway overrated. Then you buy a cheap chip from someone who has heard from someone that these things are supposed to be pretty good. It goes without saying that these chips are not programmed for the existing hardware (but they are supposed to be good, I heard from someone).

What experiences do you have with such an engine? It usually starts with a very small problem, e.g. the idle doesn't work properly and the lower load range required in everyday life doesn't work so well, usually even worse than standard. The consumption is terribly high, but that doesn't matter, it's a racing engine. Performance is good, but could be better (as always). The AFR is modest, the LH-Jetronic will hopefully adapt everything well (wishful thinking), but it doesn't really do it. With a bit of luck, the idle and partial load problems will resolve to an acceptable level. Unfortunately, the reality is somewhat different. If you have the opportunity to measure the AFR, it is either too lean (which rarely happens) or too rich (standard problem). Why? Because you mean too well! If you replace the injectors or the fuel pressure regulator, especially on a model without positive pressure adjustment in boost mode, and do not have a chip that is precisely tuned to the fuel pressure and injectorsize used, stress is inevitable. There is no way to get such a setup to work properly. Such engines can usually only be used under full load and are usually not drivable as an everyday car.

The FT engine has a fuel pressure regulator that, in boost mode, adds the boost pressure to the standard 3bar pressure to balance the boost pressure in the intake manifold (which is against the fuel pressure) so that there is still a real 3bar. If you have chosen a different regulator that does not adjust the pressure, you will have the problem of the mixture being too lean. What do you do? The fuel pressure is increased to compensate for the pressure difference to the boost pressure. So far so good, but what happens if there is no boost pressure? Then the mixture is too rich due to the high pressure and there is no way to combine both worlds. So much for the incredibly expensive fuel pressure regulator! Install the original one, it does it!

The same applies to the injectors. Larger injectors, unadapted chip, under certain circumstances the adaptation can still be achieved at partial load, but at high load the ECU only runs according to the map. The control unit calculates the required injection time based on the measured air mass and the size of the injectors, it's just too bad that someone has enlarged the injectors by 50% and the ECU doesn't know anything about it.

So the mixture in the high-load range, when the ECU goes to the map, is of course much too rich. Any increase in boost pressure results in an even richer mixture. So right from the start, the engine doesn't produce the power it could, and the further the boost pressure increases because more power is needed, the worse the problem becomes.

Another problem is that the new external components for the standard cylinder head generate too much boost pressure, but the engine cannot convert the amount of gas supplied. What happens if the engine cannot push through the pressure/volume created by the turbocharger? The turbocharger creates much more pressure than would be necessary to achieve the same power in a good engine. Because the pressure is too high, the charge air becomes hotter than desired. Hot charge air leads to a deterioration in performance due to 1. too little oxygen (air too hot) and 2. due to a reduced ignition angle due to the risk of knocking. The result is that the engine has too little power and the mixture is too rich (enrichment for internal cooling). The usual countermeasure is to increase the boost pressure, which only makes things worse.

So we turn everything back again and try to do it right this time. The nastiest engines are usually the ones that look damn near stock engines, maybe a slightly larger turbocharger that can be seen.

First you think about where you want to go in terms of performance. Then it is decided whether this performance can be achieved with the stock engine, or whether a better camshaft, or even head machining with larger valves or a conversion to 16V is necessary. The cylinder head and exhaust system must be able to convert the required amount of gas for the targeted performance. Tuning companies can usually assess this well and the engine repairer around the corner will do the necessary work. Rule No. 1 Prepare the engine for more gas throughput.

Good. Next, a turbocharger is selected that can provide the required power in continuous operation. So not an oversized monster turbo, but a suitable turbo which is installed with a suitable boost pressure control. All the hustle and bustle around it, all the colorful hoses etc., blow off valves, forget it, the engine compartment remains standard!

The next step is to get injectors and a mass air flow sensor that match the desired performance. In the case of the B230FT this usually means 3" LMM and injectors between 400-500cc/min. Then find someone who can provide the chip with the LMM map and program the injector size accordingly. This means you have an ECU that works with the standard fuel pressure regulator, will run properly from idle to full throttle from the first minute without having to tinker with the mixture. With an engine prepared in this way you will see that 1 bar of boost pressure with a medium-sized charger is enough to get 250 stable horsepower from a B230FT. And, a look into the engine compartment reveals nothing. Stock engine with sport exhaust.

When you have reached this point and everything is working well, i.e. you have the feeling that the engine is reliably suitable for everyday use, then you can start with all the colorful stuff...

Now a few comments on possible sources of error, which also lead to a mixture that is too rich.
There are errors that lead to both a mixture that is too lean and a mixture that is too rich!

Just imagine a loose charge air hose or another leak behind the turbocharger. What happens? In the lower load range without boost pressure, the engine sucks in air at the leak point that was not detected by the air mass meter. The result is a mixture that is too lean, the engine jerks and stalls when idling. Under certain circumstances, you may even be put on the wrong track and look for a non-existent error in the ignition system. When the engine is in the boost pressure range, you suddenly have a mixture that is much too rich. What happens there? Intake air measured by the air mass sensor is blown out at the leak point, which of course never reaches the engine. However, the mixture was calculated for the entire measured air mass. Result: the mixture is far too rich. There is also a risk of being taken on the wrong track, as you might think that you have to adjust the amount of fuel based on the fuel pressure or other chips, etc. So there are many reasons for a mixture that is too rich.

1. Stock engine with excessive or incorrectly adjusted external hardware
2. Mismatched LMM, injector and ECU combination, Error in the ECU
3. Fault in the ignition system, cable, distributor, old low-performance ignition coil
4. Boost pressure too high, intake temperature too high. See point 1
5. Incorrect fuel pressure regulator/petrol pressure
6. Gasoline quality (knocking=enrichment)
7. Defective LMMs
8. Defective, cheap injectors that may even leak
9. Leaking intake system
10. and all the other errors that I can't think of right now...

To go back to the beginning, it is easy to blame the error on the chip, but relatively difficult to find the real error.

With that in mind, good screwing.

{LH- Chips for FT-ECUs}


0 280 000 984  (*)
0 280 000 981  (*)
0 280 000 980  (*)
0 280 000 979  (*)
0 280 000 977  (*)
0 280 000 976  (*)
0 280 000 975  (*)
0 280 000 967  (*)
0 280 000 962  
0 280 000 954  
0 280 000 937  
0 280 000 932  
0 280 000 563  not supported
* preferred ECU
----------------------
All ECUs above are Turbo-ECUs and can be used chipped with B200FT+B230FT engines, all chips come without immobilizer.

{EZK- Chips}

0 227 400 219
0 227 400 208
0 227 400 207
0 227 400 148  *
0 227 400 146  *
* requires daughterboard
----------------------
EZK-Daughterboard
and Wasted spark

{Availability & Prices}

LH-Jetronic:  150 Euro
EZ-116K:        50 Euro
Bundle:          175 Euro

Stock: available