How much detergent are you using? If you don't want to add extra rinses/washes, you will probably need to reduce the amount of detergent you're using. Washers are a bit different here but in our energy efficient front loaders, people tend to use less than the full dose of detergent. I use no more than a quarter dose with most detergents. Any more and I'd be rinsing all day.
You can also put a wet towel in with the nappies to increase the weight of the load, as modern machines often weigh the laundry to work out how much water to use. Also check your manual - sometimes a heavy soil cycle uses more water but some on some machines it uses less to increase the friction, and obviously you don't want that.
Do you have the option of a warm rinse (not hot, but not cold)? Warm water will help rinse the detergent out better than cold. I'd do a cold rinse before the wash, then your longest wash cycle (mine is 3.5 hours) then at least one more rinse in warm water if you can, probably 2 rinses, or a short-ish warm wash with no detergent. Use the least amount of detergent you can use and still get the nappies clean.
If you already have build up, you will need to strip wash first though. Changing your laundry routine won't make a difference until you do, unfortunately.
Alternatively, try a detergent formulated for cloth nappies e.g. Eco Sprout, Rockin Green etc and follow the directions for an HE front loader.
