PeachParts Mercedes-Benz Forum - View Single Post

duxthe1 · #73 06-10-2025, 01:18 AM

I've had a set of 298cc injectors to install for about 2 weeks now but its been a crazy rainy spring so I've put off installing them. My tuning ECU is open to the elements and I'm not keen to drive around with it when its raining. Well, the forecast looked good enough for the next few days so I installed the larger injectors.

The previous pink 260cc injectors ran quite well but were maxxing out sooner than expected. On cold start they took a slight bit longer to fire up, but not terrible. I didn't tune the cranking enrichment for them knowing they would come back out. Will have to see how the 298s do with the cold starts over the next several mornings. The 298s are a better fit in the rail. The clip grooves line up perfect and they even have an alignment tab like the stock injector. Its not quite as wide so there is a smidge of axial wiggle but overall a better fit than the pink 260s.

So far I've just roughed in the fuel tables. I can hit pretty rich (high .7s lambda) WOT AFRs with a bit of headroom now. Its kinda looking like the 298s are less linear than the 260's in that they seem to be leaner at lower pulsewidths. This could possibly be due to a significant difference in injector dead time compared to the stock 200cc injector. Somewhere in the binary file there is a value that describes the injector dead time. Finding and defining a single value is much, much, much harder than digging out the maps.

After I get the part throttle fuel maps sorted, I'll try to get an hr on the dyno to get the WOT dialed. In the meantime I've started working on a setup to run the HFM module on the bench. A fully simulated environment is going to be difficult to pull off, but I think it will pay dividends in what it may allow me to figure out beyond just emulating on a running engine.