air fuel no or erratic reading

wayfstyt · #1 (**permalink**) 08-15-2010, 11:51 AM

Hi,just purchased an air fuel 170402. I installed it on my small block chevy drag car yesterday,turned it on. Went through the set up. Both sensors were reading 0.00. Ran the car about 5 minutes no readings. Shut the car off,restarted it and the readings were so fast it couldnt comprehend them. Its powering up ok,and will record and play,but cant read the numbers. Its a simple set up,carburated race gas small block chevy. Open headers w/slip on collectors,the sensors are at 12 oclcock position 5.5 inches inside the collector. any ideas? thx tim

TurboNova · #2 (**permalink**) 08-15-2010, 01:15 PM

#1 slip-on collectors are a huge problem with a wideband. The gaps in the slip part will allow fresh air to enter the collector and give false readings. The collector needs to be completely sealed and free of leaks.

#2 5" of pipe to the end from the sensor isn't near enough. The exhaust pulses entering back and forth because of the overlap and tight lobe center of the cam with show lean on the sensor. From what I have found on a combo like this you need at least 2' of exhaust past the collector to get a good reading.

wayfstyt · #3 (**permalink**) 08-15-2010, 01:59 PM

Thx brian, i just went out and fired the engine,no reading at idle,when i bring the rpms up to 2000-2500 its starts reading and is so fast and erratic i cant tell what the numbers are. I spoke to a guy named john before i bought this and he said he has one on his race car and the only problem i may run into is the life of the sensor because of the race fuel. Is there any way around this,from what i read i figured with 5.5 inches of pipe after the sensor it would be ok. I cant really add anymore pipe to the collector. Basically i just want a wot reading so i can jet my car for consistency. I know that alot of drag cars with tight lobe cams and open headers have to be running these things? Also my collectors are a very tight fit onto the header pipes,you have to tap them in place when instaling them.

TurboNova · #4 (**permalink**) 08-15-2010, 04:11 PM

There is no slip on collector that will seal without some type of sealant. We have used muffler sealant or silicone before. Believe me, having to pound them on has nothing to do with the actual pipe sealing air tight around each tube, just not going to happen.

5" is way too close to the end, you may get a reading at WOT but I would not trust it. You really have to have some space..... Like a couple of feet past the collector for it to work right.

wayfstyt · #5 (**permalink**) 08-15-2010, 05:01 PM

ok brian, i removed the collector put some high temp sensor safe rtv around the 4 collector tubes and sealed them up becasue i took a light and looked inside the collector and you were right i could see daylight around the tubes. Went to the parts store and bought a 4 inch long piece of exhaust pipe and stuck it on the end on the collector. I only did one side because i wanted to see if there was a difference. Sure enough the side i sealed up and put the extension pipe on starts to read sooner than the other side.. still no reading at idle on either.. the damn directions say to put the sensor in the colllector? the problem i will have with the extension of the collector is it exits out behind the front tire.. so i cant make it but so long.

wayfstyt · #6 (**permalink**) 08-15-2010, 06:59 PM

hey brian,your the man! I stuck a piece of 13inch long straight pipe on the end of the collector and it started reading at idle. So i will try to configure a 45 on it with a piece of straight pipe to run it down the side of the car and it should work. the instant i stuck that pipe on it it started reading,take it off it stops. So i guess where i have the sensor mounted is ok?? Its about middle way of the collector,