high EGT on full throttle. 3300 with Rotec TBI

[kevin814]

Hi, I'm curious what EGT's others are experiencing when running wide open.

Climbing out at 100 mph my EGT's run from 1260 to 1305, and full throttle straight and level (with a cruise prop) I max out at 3150 rpm, and my EGT's pass 1350 and approach 1400 before I back off. The spray bar has had a couple holes at the wide open end slightly enlarged. Its not that I routinely like to fly flat-out, but I would like the ability. Now I just work around the problem by throttling back. Using the primer doesn't make any difference, unless the fuel pump is on and it stutters and is too rich. I fly with the fuel pump on during climb out and at full throttle to get the above numbers, without it they shoot over 1400 EGT. I have cleaned every hole in the spray bar, last chance filter and gascolator. Flow to the TBi seems good. The pressure regulator appears to be working, but not sure if they go bad.

What are your experiences with this setup? Are your numbers similar to mine, or have you found a solution? All opinions welcomed!

Thanks,

Kevin K.

[SvingenB]

Hmmm. I have been wondering about the Rotec TBI, but will install the AeroCarb first and see how it goes. The reason, according to Rotec Spec it needs min 0.5 PSI to be sure it works "all around". You won't get 0.5 psi from gravity alone, and would therefore need a pump running. Some pressure is lost in the lines and fittings also, the more power, the more fuel flow and more pressure is lost. If there is no difference when the primer is pushed, it means the pressure regulator is already full open and/or there simply is not enough pressure to push that amount of fuel.

That's my shot at it. How is your spray bar set up at full rich?

[kevin814]

My spray bar is set to approximately 90 degrees (to the side) at full rich. I have thought about adjusting it, which is fairly simple. The reason I haven't yet is that it would richen the mixture further at other throttle settings, unless I lean it out. I normally don't lean it out when I'm just messing around, but do when I'll be flying at one throttle setting for a while. Overall I'm happy with the Rotec, and gravity feed works fine vs fuel pump on except at full throttle. I think the next time I have the cowling off I'll try adjusting the spray bar and see what happens. I't too bad materials science hasn't advanced enough to allow us to run at 1400-1500 EGT's. When its running rich enough to keep the EGT's at 1300 I'm putting out less power and sucking more fuel. I can't run lean of peak, because the engine runs poorly by the time I get the EGT's back down.

[WaiexN143NM]

Hi all!
Got the rotec tbi set up and running on our waiex w jab3300. Love it! First is no sticking throttle slide assy!! Easy starts, precise mixture control. It took a couple days of work to install , there is a flow regulator and primer line to hook up . We are testing so far without a facet 12v pump, will see if gravity fuel is enough. will do full throttle runs later today. Anyone else running the rotec tbi w jab. 3300? Any suggestions , operational comments etc? I have read a few earlier postings. Thanks





Michael RADTKE
Waiex N143NM
Jab 3300
Rotec tbi
Dynon glass