52mm throttle body
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
Someone with more experience than I would have to comment on the MAF "freaking out" b/c the air flow values were high. I don't think that happens though, as the MAF has nothing to "compare" the air flow to. Later cars have MAP AND MAF, so there could be a comparison there, but OBD I cars only have one or the other. The only "comparison" the ECM can make is throttle position & RPM (calc'ed air flow, AKA Alpha-N) vs. MAF (actual) and I don't think they're that sophisticated. IOW, I think 80's MAF cars take an increase in MAF w/o major issues or CEL's.
The SD I know from my experience playing w/the thing, that it can "take" a LOT, before throwing a CEL or "freaking out". That doesn't mean that what it "takes" (and works off of) results in a proper tune or running engine...but again, the ECM has nothing to "compare" the MAP values to, other than basic Alpha-N....and that MAP reading can vary quite a bit. Just boring TB's "could" cause it to throw a CEL: at a given TPS voltage, your MAP would be higher than stock, b/c of the bored TB's greater area...yet that throws no CEL nor does it cause a running problem. Why? My guess is that it's not sophisticated enough to "know" and that is b/c it doesn't need to be, to meet the criteria of the era. What can it "cope with"? Well, I added ~130hp to my SD car w/no ECM tuning. Another recent example (although Ford) is that I recently helped a friend with his '88 5.0. We installed LT headers and full exhaust, GT-40P heads, Rockers, GT-40 intake, and a TB. Thing runs great. Would tuning help it? I'm sure it would, but it's "coping" fine w/the changes and he picked up about 40 RWHP. Again, in this case, cam remained stock and so did displacement. So no radical change to the SHAPE of the tq curve.
IDK what is left on the table for a stock MAF TPI...someone who has tuned and dynoed stock ones would have to chime in here.
The SD I know from my experience playing w/the thing, that it can "take" a LOT, before throwing a CEL or "freaking out". That doesn't mean that what it "takes" (and works off of) results in a proper tune or running engine...but again, the ECM has nothing to "compare" the MAP values to, other than basic Alpha-N....and that MAP reading can vary quite a bit. Just boring TB's "could" cause it to throw a CEL: at a given TPS voltage, your MAP would be higher than stock, b/c of the bored TB's greater area...yet that throws no CEL nor does it cause a running problem. Why? My guess is that it's not sophisticated enough to "know" and that is b/c it doesn't need to be, to meet the criteria of the era. What can it "cope with"? Well, I added ~130hp to my SD car w/no ECM tuning. Another recent example (although Ford) is that I recently helped a friend with his '88 5.0. We installed LT headers and full exhaust, GT-40P heads, Rockers, GT-40 intake, and a TB. Thing runs great. Would tuning help it? I'm sure it would, but it's "coping" fine w/the changes and he picked up about 40 RWHP. Again, in this case, cam remained stock and so did displacement. So no radical change to the SHAPE of the tq curve.
IDK what is left on the table for a stock MAF TPI...someone who has tuned and dynoed stock ones would have to chime in here.
Last edited by Tom400CFI; Dec 4, 2015 at 05:07 PM.
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
Someone with more experience than I would have to comment on the MAF "freaking out" b/c the air flow values were high. I don't think that happens though, as the MAF has nothing to "compare" the air flow to. Later cars have MAP AND MAF, so there could be a comparison there, but OBD I cars only have one or the other. The only "comparison" the ECM can make is throttle position & RPM (calc'ed air flow, AKA Alpha-N) vs. MAF (actual) and I don't think they're that sophisticated. IOW, I think 80's MAF cars take an increase in MAF w/o major issues or CEL's.
The SD I know from my experience playing w/the thing, that it can "take" a LOT, before throwing a CEL or "freaking out". That doesn't mean that what it "takes" (and works off of) results in a proper tune or running engine...but again, the ECM has nothing to "compare" the MAP values to, other than basic Alpha-N....and that MAP reading can vary quite a bit. Just boring TB's "could" cause it to throw a CEL: at a given TPS voltage, your MAP would be higher than stock, b/c of the bored TB's greater area...yet that throws no CEL nor does it cause a running problem. Why? My guess is that it's not sophisticated enough to "know" and that is b/c it doesn't need to be, to meet the criteria of the era. What can it "cope with"? Well, I added ~130hp to my SD car w/no ECM tuning. Another recent example (although Ford) is that I recently helped a friend with his '88 5.0. We installed LT headers and full exhaust, GT-40P heads, Rockers, GT-40 intake, and a TB. Thing runs great. Would tuning help it? I'm sure it would, but it's "coping" fine w/the changes and he picked up about 40 RWHP. Again, in this case, cam remained stock and so did displacement. So no radical change to the SHAPE of the tq curve.
IDK what is left on the table for a stock MAF TPI...someone who has tuned and dynoed stock ones would have to chime in here.
The SD I know from my experience playing w/the thing, that it can "take" a LOT, before throwing a CEL or "freaking out". That doesn't mean that what it "takes" (and works off of) results in a proper tune or running engine...but again, the ECM has nothing to "compare" the MAP values to, other than basic Alpha-N....and that MAP reading can vary quite a bit. Just boring TB's "could" cause it to throw a CEL: at a given TPS voltage, your MAP would be higher than stock, b/c of the bored TB's greater area...yet that throws no CEL nor does it cause a running problem. Why? My guess is that it's not sophisticated enough to "know" and that is b/c it doesn't need to be, to meet the criteria of the era. What can it "cope with"? Well, I added ~130hp to my SD car w/no ECM tuning. Another recent example (although Ford) is that I recently helped a friend with his '88 5.0. We installed LT headers and full exhaust, GT-40P heads, Rockers, GT-40 intake, and a TB. Thing runs great. Would tuning help it? I'm sure it would, but it's "coping" fine w/the changes and he picked up about 40 RWHP. Again, in this case, cam remained stock and so did displacement. So no radical change to the SHAPE of the tq curve.
IDK what is left on the table for a stock MAF TPI...someone who has tuned and dynoed stock ones would have to chime in here.
In my case, EGR was fully functional but sometimes it would dislike what was going on and throw a Code 32 and sometimes not. Hit the gas and there is some slight bog till it wakes up. IIRC, we were using DIACOM and it did graph some sort of bog when we hit the throttle most times. So sometimes it seems fine but more often than not, you feel the bog. Got fed up and hauled it several hours away to Decatur, IN to fix the program once and for all. After tuning, we drove it home with no Code 32 and DIACOM didn't show anything on the graphs out of normal. BLM was normal. Previously, TPS graph vs RPM showed that when the TPS was spiking up (WOT), the RPM didn't always run up with it.
