Cylinder Head Temp Variation

[Craig Hoskins]

Chris,
My Rotec TBI is installed the spray bar to the left. This could be the root cause of the left more rich and cooler, and the right more lean and hotter. When I run cowl air or carb heat, I also get the EGT's hotter on the right side along with higher CHT's. One test variation in my new distribution manifold setup will be to block the right supply side and record the performance, then block the left side and compare.

I'm also running a air flow straightener between the air filter and the Rotec TBI. It is made from 3/16-in hex cell by 3/4-in thick and made from aluminum. Rotec makes a big deal about straight flow air into the TBI to make sure the sensor works properly. I have seen several others have done the same thing.

Happy flying,
Craig Hoskins
Sonex 1537, Tri Gear, 85 hrs
GPAS 2276cc VW, Rotec 34-2 TBI, Prince P-tip

[WaiexN143NM]

Hi All,
Don't know if it will help , but on our jab 3300 waiex we are using a stainless flow straightener from aircraft spruce ($100) , was designed for Ellison Tbi , but we are using on our rotec tbi , works great, very even cht/egt's.

WaiexN143NM
Michael Radtke

[Johns]

Hi Guys, I purchased my plane from someone who was a auto mechanic and he had the same problem of the two front cylinders being cooler than the rear two. He also thought it was a fuel mixing problem. To quote the log book "I suspect due to the air pipes going 2 into one that the momentum of pulsing fuel in the intake rams against the end of the manifold and a lot of extra fuel bounces from that end into the front cylinder."

So what he did was to use the stock VW metal intake gasket and cut out the center between the ports and that equalized the fuel problem.

Hope this helps, it is inexpensive if you want to try it.

John

[tom0nex74]

Been flying 0nex0074 for 130 hrs with usual cylinder temp problems,went to 2.5 needle in Aeroinjector, richened mixture, opened lower cowl,etc. I have found that, in my particular aircraft that minimizing prop loading keeps temps at an acceptable level.I let the speed and rpms build on climb out 3200 rpms 95 mph 400fpm keeps my cylinder temps below 350 and egt in the low 1200's. I cruise climb at 110 mph from there letting the rpms build slowly. It seems to be a low torque system, steep turns load the prop quickly, decreasing rpms and added back pressure deceases airspeed quickly. Any increase in temps disappear on return to level flight. Should have built it lighter and cleaner, I reckon. At 5000 ft 3350 rpms I get the advertised 150mph true. The engine and prop seem smooth and temps are at an acceptable range.
nwyooper........How do you like the TB MarkII? Improved performance? The mixture system seem more precise than the Aeroinjector system.
Happy and safe flying boys..............Tom Ryan 0nex 0074

[nwyooper]

Hi Tom,
The Mark II is great-I had issues with the Mark I and Rotec replaced it which I thought was great. I am at sea level and never run full rich except on startup and then I go to full lean while warming up and taxiing(Check list item on run up to richen mixture and fuel pump on). It idles better than the AeroInjector my hangar mate has on his Onex. No airflow straighteners and I am running 92 octane non-ethanol mogas. BTW we have 3 planes(two Onex's and a RV4) in one hangar-advantage Onex's and they fly great!! Also I have gotten 150 mph TAS at about the same rpm and altitude as you state.
Loren
Onex33