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914World.com _ 914World Garage _ A/F bung
Posted by: North Coast Jim Jun 15 2019, 11:21 AM
Looking to add an Air Fuel guage to help finalize my new carb install. Adding a bung for the O2 sensor it seems like I should remove the heat exchangers to help the fabricator add the bung. Is this needed or can it be done while in the car ?? Where to actually add the bung, any suggestions or pics.
Posted by: rjames Jun 15 2019, 12:08 PM
Assuming stocking setup, You don’t need to remove the exchangers but you will likely need to remove the muffler. At the very least it will make the job easier.
Some good info here:
http://www.914world.com/bbs2/index.php?showtopic=336006&hl=
Posted by: Mark Henry Jun 15 2019, 02:29 PM
I've been doing some testing, but it was on a 914 2.0 DTM T4 into a bug conversion with a CSP 4/1 SS header into a SS corvette muffler, in/out same side.
A huge area of concern is on each side of the header and muffler flange, the muffler side I see a 150+F drop in temperature. Enough of temp drop that the sensor doesn't have enough heat to be optimal. I was very surprised to see how big of a temp drop it was each side of the exhaust flange. Temps were taken at the end of a 30 minute test run at 3000rpm with a laser gun.
Wish I had a stock or SSI /4 to see what the temp in a stock muffler or triad is...
For a six I'd put the bung on the header after the collector, but then this becomes a two meter system.
Posted by: SirAndy Jun 15 2019, 02:51 PM
I only put one sensor in the header on the passenger side. Probably not ideal but it seems to be working just fine.
Posted by: Maltese Falcon Jun 15 2019, 03:41 PM
I only put one sensor in the header on the passenger side. Probably not ideal but it seems to be working just fine.
That's a perfect spot, with the bung facing upwards at 12'oclock. On the 9146 header collector...you are sampling 3 ports at once= good.
At the rear of a T4 heat exchanger, it will be good to capture 2 ports...so have your fabricator/ welder look for that spot Maybe just at where the 2 tubes join up into the muffler. Otherwise you will only be sampling 1 exhaust port = not optimal, but will work
Posted by: Mark Henry Jun 16 2019, 06:06 AM
I only put one sensor in the header on the passenger side. Probably not ideal but it seems to be working just fine.
That's a perfect spot, with the bung facing upwards at 12'oclock. On the 9146 header collector...you are sampling 3 ports at once= good.
At the rear of a T4 heat exchanger, it will be good to capture 2 ports...so have your fabricator/ welder look for that spot Maybe just at where the 2 tubes join up into the muffler. Otherwise you will only be sampling 1 exhaust port = not optimal, but will work
So on the stock or SSI /4 exchanger make a cross tube to form an H before the muffler flange?
To me that would be a better solution for keeping heat to the lambda.
Posted by: Maltese Falcon Jun 16 2019, 03:44 PM
I only put one sensor in the header on the passenger side. Probably not ideal but it seems to be working just fine.
That's a perfect spot, with the bung facing upwards at 12'oclock. On the 9146 header collector...you are sampling 3 ports at once= good.
At the rear of a T4 heat exchanger, it will be good to capture 2 ports...so have your fabricator/ welder look for that spot Maybe just at where the 2 tubes join up into the muffler. Otherwise you will only be sampling 1 exhaust port = not optimal, but will work
So on the stock or SSI /4 exchanger make a cross tube to form an H before the muffler flange?
To me that would be a better solution for keeping heat to the lambda.
That will be on point...just use tubing dia. that will allow the sensor portion of the o2 into the exhaust flow enough to sample...but not to block the flow
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