Fun with troubleshooting leanness (and 5th gear cruising temps) |
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Fun with troubleshooting leanness (and 5th gear cruising temps) |
emerygt350 |
Mar 15 2024, 03:37 PM
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#1
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Advanced Member Group: Members Posts: 2,139 Joined: 20-July 21 From: Upstate, NY Member No.: 25,740 Region Association: North East States |
So I have been playing with adding resistance to the cht to bump my mixture. Messing with the mps was not getting me to where I wanted to be I wanted something a little more global. Anyway, bought a 10 dollar Bluetooth relay. Set it up so one channel was clean the other had 50ohms resistance in it. As I am driving I can switch back and forth and watch the results on the cht and AFR. 50 is really working well (this is all in addition to my 250ohm found on 73s). Now I have added another 20 ohms to the alternate so the relay will switch between 50 and 70. It ain't pretty but it's only for troubleshooting.
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emerygt350 |
Mar 17 2024, 06:53 PM
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#2
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Advanced Member Group: Members Posts: 2,139 Joined: 20-July 21 From: Upstate, NY Member No.: 25,740 Region Association: North East States |
Yeah, the only place where I have an issue is 5th gear interstate travel. Racing it stays nice and cool. I may just have to make some kind of fudge for that and stop worrying about it.
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era vulgaris |
Apr 3 2024, 09:19 AM
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#3
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J is for Genius Group: Members Posts: 982 Joined: 10-November 13 From: Raleigh, NC Member No.: 16,629 Region Association: South East States |
Yeah, the only place where I have an issue is 5th gear interstate travel. Racing it stays nice and cool. I may just have to make some kind of fudge for that and stop worrying about it. 5th gear interstate travel is always going to run hotter than lower gears below ~65mph. Around roughly 65mph is where air resistance begins to become a factor on the load the engine sees, and the faster you go above 65mph, the more load the air resistance and drag will be putting on the engine. I used to run a 4 channel digital CHT gauge designed for light aircraft on a 2270 type 4 running dual DRLA40's, tuned to keep AFR in the mid-to-high 12's at cruise (this is where I got the lowest head temps). #3 CHT in gears 1-4 running around town, cruising in the 3k-3.5k rpm range, was low 300's, like 315-320 area. Cruising above 70mph in 5th (same rpm range) with the top on and windows closed was like 350. Windows open it was a little higher due to increased drag. But with the windows down and top off on the interstate it was even higher, like 365-ish area, because with the top off at those speeds the car's aerodynamics basically turn into a parachute that the engine has to fight against. Notably, below 65mph having the top on or off made no difference in head temps because the drag it creates at those lower speeds isn't enough to impact the load on the engine. As long as head temps keep steady and don't creep upwards continually, then I don't think there's much to be done about this. I took multiple 3+ hour trips on the interstate, and head temps always stayed rock solid steady at the above numbers, and would come back down to the off-highway numbers once off the interstate. |
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