Loewenherz Racing

#5 - Injectors, part three :(

Having upgraded from the stock squirters to 550cc FiveO racing injectors allowed me to get to 251whp while keeping duty cycle below 90%, however, they’re quite taxed working in the high 80% range.

I developed a hiccup coming from a closed throttle to cracked open at 1-2% throttle, while doing so the bike will swing super lean, like 18:1 AFR lean and not run right.  If the throttle is opened quicker, say from closed to 5% or more it runs properly.

We also found, that on the dyno, they are very difficult to dial in properly, as though they're not responding in a linear manner.  While tuning, the values you need to adjust them by do not relate to % changes in fueling, for example, a 3% increase in fueling demand using the table may give 10% more fuel or 1%, requiring additional tuning time and effort.  The FiveO injectors have been sent back for servicing, but, I am acutely aware that I am at their upper limit.  I'll be holding on to them for a future use, potentially as the second set in a dual squirter setup down the road.

Enter Siemens Deka IV 107-962 61lb/hr injectors. They’re both cheap, and they’re properly sized to keep up with the MUL/C fueling requirements.  Running oxygenated fuel is going to increase fueling needs by around 5% alone, then add the extra air from running filter-less and I’m positive my 550s will be static or fractionally below it.


Ballenger Motorsports to the rescue!  They offer both the injectors and push on pig tails I can solder to the bike easily for $185, a steal.   The Deka IVs should give me enough headroom for 280whp while maintaining phenomenal idle characteristics.

https://www.bmotorsports.com/shop/product_info.php/products_id/449