What point cam too large to run in closed loop?
What point cam too large to run in closed loop? Is there a general duration limit on a cam where it has too much overlap to run in closed loop or does the factory computers have enough adjustment they can compensate for large durations and overlap?
I would say its not a matter of cam size really. The O2's are going to adjust fueling based off of AFR. Overlap at idle is going to make you run false rich because of fuel short circuiting. This can be adjusted to an extent with messing with Injector Timing.
Is there a general duration limit on a cam where it has too much overlap to run in closed loop or does the factory computers have enough adjustment they can compensate for large durations and overlap?
So as far as the o2 sensors themselves are concerned you're going to be ok regardless of the cam. Now tuning wise and driveability is where cam size comes in and there is a very sharp downturn in those after going past like 14-16* of overlap.
On The Tree
Joined: Jan 2013
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From: Newcastle
I ususlly find any camshaft over negative 5 overlap at 50 thou starts to become questionable to run in closed loop at low engine speed under 2000 RPM and particuly idle depending on cam size, cubes, compression etc..... Every engine responds differently to mods and tuning requirements
ususlly find any camshaft over negative 5 overlap at 50 thou starts to become questionable to run in closed loop at low engine speed under 2000 RPM and particuly idle depending on cam size, cubes, compression etc..... Every engine responds differently to mods and tuning requirements
On The Tree
Joined: Jan 2013
Posts: 191
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From: Newcastle
Stock cams have very little overlap at all so fuel going out the exhaust is minimal and the gas going out is very smooth so o'2 data is very accurate, the bigger the cam the more overlap the less accurate the o'2's are until they reach a point of being pointless
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That was my theory, which is why I asked. I called a cam manufacturer the other day and they couldn't answer the question either.
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The more overlap the less vacuum at idle and the more fresh air going into the exhaust the o2s will see this and think it is lean and start adding fuel. To get around this turn off adaptives at idle and up till the point where you have decent vaccum before allowing them to trim again. For instance I tuned a car that had 8hgs of vacuum at idle but at 2000 had 18hgs. Idle fueling was hard to do because of all the fresh air going out the exhaust due to lArgentina overlap. Afrs at idle ended up being around 15.5-16 at idle to get the raw fuel smell to go away and to keep it from loading up.