97 7.5L Timing
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05-29-2002, 05:15 PM
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05-30-2002, 08:01 AM
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97 7.5L Timing
>What are you guys running for timing on you 460s? If I
>advance it at all, it starts to ping badly. Thanks,
>Jerry
>
>BTW, its a F-350 4x4 w/E4OD
Full or part-throttle?
If it pings bad at part throttle it could be insufficient EGR gas flow, especially when the weather starts getting hot. Later model EFI stock 460s seem to ping easily without adequate EGR.
Not to say it's not something else, but full or part throttle is sometimes a clue. What year? Any engine modifications?
>advance it at all, it starts to ping badly. Thanks,
>Jerry
>
>BTW, its a F-350 4x4 w/E4OD
Full or part-throttle?
If it pings bad at part throttle it could be insufficient EGR gas flow, especially when the weather starts getting hot. Later model EFI stock 460s seem to ping easily without adequate EGR.
Not to say it's not something else, but full or part throttle is sometimes a clue. What year? Any engine modifications?
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05-30-2002, 09:33 AM
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97 7.5L Timing
It was part throttle under load. The only thing changed is the cat- back. It's pretty young to have egr problems, only 42,000 miles, but I guess anything is possible. I'm not really looking for diagnostics, I'm a Ford Master Tech with 8 years at the dealer and now 2 years on the Hotline,
I was just wondering if anybody was runing more than base timing.
Thanks,
Jerry
I was just wondering if anybody was runing more than base timing.
Thanks,
Jerry
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05-30-2002, 11:15 AM
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97 7.5L Timing
Hi, Jerry.
I own a '96 F-250 460 and I've got the initial advance set about 2 degrees more than factory spec. I'm also using that "fake the intake air temperature sensor" added resistor trick that a few of the Mustang guys use for a more agressive advance curve, on top of that. That probably adds another two to three degrees at higher RPMs.
When it's 75 or cooler outside, I have no ping at all on regular, if it's hotter or if I'm towing my 7,000 lb trailer, it does ping a little at both part and WOT throttle so I have to switch to mid-grade in the summer unless I retard the timing a bit.
I had some past difficulties with my EGR flow because of my headers, and that would *really* set it to pinging with part throttle under load...Actually, the pinging wasn't quite as bad at full throttle, but I had to use premium until I fixed it.
Once I restored adequate EGR gas flow, the pinging problem pretty much vanished, as I described. The truck also ran much better, overall. That's why EGR was the first thing that came to mind.
You can get a free reading of your OBD-2 at Auto Zone stores, insufficient EGR gas flow will set an error code that makes it pretty easy to diagnose.
I own a '96 F-250 460 and I've got the initial advance set about 2 degrees more than factory spec. I'm also using that "fake the intake air temperature sensor" added resistor trick that a few of the Mustang guys use for a more agressive advance curve, on top of that. That probably adds another two to three degrees at higher RPMs.
When it's 75 or cooler outside, I have no ping at all on regular, if it's hotter or if I'm towing my 7,000 lb trailer, it does ping a little at both part and WOT throttle so I have to switch to mid-grade in the summer unless I retard the timing a bit.
I had some past difficulties with my EGR flow because of my headers, and that would *really* set it to pinging with part throttle under load...Actually, the pinging wasn't quite as bad at full throttle, but I had to use premium until I fixed it.
Once I restored adequate EGR gas flow, the pinging problem pretty much vanished, as I described. The truck also ran much better, overall. That's why EGR was the first thing that came to mind.
You can get a free reading of your OBD-2 at Auto Zone stores, insufficient EGR gas flow will set an error code that makes it pretty easy to diagnose.
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05-31-2002, 06:10 AM
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97 7.5L Timing
>What is the "fake the intake air temperature sensor" trick
The idea is to fool your engine into thinking the outside air temperature is much colder than it really is. While feedback from the oxy sensors is used by the ECU to set the mixture, a reading of the outside air temperature is used by the ECU to set the overall timing and the mixture at wide open throttle and how much advance to use at the upper RPM power band. Like the old centrifigal advance. The colder it is, the more advance is dialed in and the mixture is fattened up more at full throttle- but NOT at part throttle or cruise, where the oxy sensors fine tune the mixture.
The intake air temperature is measured with a thermistor sensor in the air filter box (in the case of my truck). Its resistance goes UP as the temperature goes down. I made some measurements on my truck's sensor with a digital meter in the kitchen of our house, at 100 degrees, the resistance is about 20K ohms (20,000 ohms), at 50 degrees, I measured about 50K, at freezing, about 100K and after being pulled out of a freezer, about 150K.
I reinstalled the sensor in my truck, cut one of the wires a few inches from the sensor's wiring harness connector and spliced a 47K, 1/2 watt resistor into the line. Wow! Major improvement. The slight flat spot or hesitation in winding out or pulling through the gears was greatly improved. So I went to a 75K resistor, fantastic! VERY strong pull through the entire RPM range, a real seat-of-the pants increase in torque. No, I'm not exagerating, not a bit.
Only last week, I was hauling a 1800 pound (measured on a scale)
4'x 4' x 7' bale of hay in the bed and the truck accelerated and pulled at 75+ on the interstate like it was absolutely nothing. Brutal torque.
Under heavy load, only during hot weather, there was a slight amount engine ping on regular with the 75K resistor, a switch to mid-grade stopped any pinging, also retarding the static timing 2 degrees at the distributor did the job, but so far, I've put the timing back where it was and went with the mid-grade during the hot weather we've been having.
What about mileage? When not towing, I had always gotten around 10 to 11 MPG (max) with the truck, in the hills, on the flats, a 50-50 mix of hi speed rural and congested city driving. On my last two fillups with the 75K resistor in place, I've gotten 12 to 13 (!) MPG. (200 miles, 15.6 gallons).
What about the ECU? It's perfectly happy. I have a reader and after several weeks no error codes are being reported.
So, what's going on here? I've done a lot of the usual bolt-on engine mods, what I suspect is going on is the addition of the headers and free-flow intake made the truck run a bit too lean and not have enough ignition advance through the power band. I believe the oxygen sensors have only a limited amount of influence over the mixture and have no effect at all over the ignition advance or mixture under heavy load or wide open throttle. Fooling the ECU into thinking the incoming air is much denser than it really is makes it use a timing and fuel curve that compliments the other engine mods I've made. It really turns the truck on.
I'm going to add a disclaimer. What I did worked very well on my own truck, which is a '96 with California emissions and a MAF system. Because I haven't tried this trick on any other vehicles, I have no idea if it will work as well on a speed-density system, for example. I also don't know about the new modular engines. I suspect that the benefits will be very limited on a stock engine, better breathing than stock with a good exhaust and intake, maybe an RV cam are probably necessary. You have to open the engine breathing up first. And going too far with the added resistance will cause pinging, depending on the REAL outside air temperature, and you have the risk of getting an ECU error code or the dreaded check engine light for too much resistance or an open in the temp sensor line. -40F degrees, is, I believe, the limit.
I am also using a home brew free-flow COOL air intake, which is an oversize K&N element in a sealed box using ducted outside air only. No hot engine compartment air. I've also insulated the air ducts and piping tp the throttle body with aluminum-backed pipe insulation. Looks kinda neat, like a NASA project.
So, there you have it. More mileage, torque and power for a 25 cent part on a modified engine.
The idea is to fool your engine into thinking the outside air temperature is much colder than it really is. While feedback from the oxy sensors is used by the ECU to set the mixture, a reading of the outside air temperature is used by the ECU to set the overall timing and the mixture at wide open throttle and how much advance to use at the upper RPM power band. Like the old centrifigal advance. The colder it is, the more advance is dialed in and the mixture is fattened up more at full throttle- but NOT at part throttle or cruise, where the oxy sensors fine tune the mixture.
The intake air temperature is measured with a thermistor sensor in the air filter box (in the case of my truck). Its resistance goes UP as the temperature goes down. I made some measurements on my truck's sensor with a digital meter in the kitchen of our house, at 100 degrees, the resistance is about 20K ohms (20,000 ohms), at 50 degrees, I measured about 50K, at freezing, about 100K and after being pulled out of a freezer, about 150K.
I reinstalled the sensor in my truck, cut one of the wires a few inches from the sensor's wiring harness connector and spliced a 47K, 1/2 watt resistor into the line. Wow! Major improvement. The slight flat spot or hesitation in winding out or pulling through the gears was greatly improved. So I went to a 75K resistor, fantastic! VERY strong pull through the entire RPM range, a real seat-of-the pants increase in torque. No, I'm not exagerating, not a bit.
Only last week, I was hauling a 1800 pound (measured on a scale)
4'x 4' x 7' bale of hay in the bed and the truck accelerated and pulled at 75+ on the interstate like it was absolutely nothing. Brutal torque.
Under heavy load, only during hot weather, there was a slight amount engine ping on regular with the 75K resistor, a switch to mid-grade stopped any pinging, also retarding the static timing 2 degrees at the distributor did the job, but so far, I've put the timing back where it was and went with the mid-grade during the hot weather we've been having.
What about mileage? When not towing, I had always gotten around 10 to 11 MPG (max) with the truck, in the hills, on the flats, a 50-50 mix of hi speed rural and congested city driving. On my last two fillups with the 75K resistor in place, I've gotten 12 to 13 (!) MPG. (200 miles, 15.6 gallons).
What about the ECU? It's perfectly happy. I have a reader and after several weeks no error codes are being reported.
So, what's going on here? I've done a lot of the usual bolt-on engine mods, what I suspect is going on is the addition of the headers and free-flow intake made the truck run a bit too lean and not have enough ignition advance through the power band. I believe the oxygen sensors have only a limited amount of influence over the mixture and have no effect at all over the ignition advance or mixture under heavy load or wide open throttle. Fooling the ECU into thinking the incoming air is much denser than it really is makes it use a timing and fuel curve that compliments the other engine mods I've made. It really turns the truck on.
I'm going to add a disclaimer. What I did worked very well on my own truck, which is a '96 with California emissions and a MAF system. Because I haven't tried this trick on any other vehicles, I have no idea if it will work as well on a speed-density system, for example. I also don't know about the new modular engines. I suspect that the benefits will be very limited on a stock engine, better breathing than stock with a good exhaust and intake, maybe an RV cam are probably necessary. You have to open the engine breathing up first. And going too far with the added resistance will cause pinging, depending on the REAL outside air temperature, and you have the risk of getting an ECU error code or the dreaded check engine light for too much resistance or an open in the temp sensor line. -40F degrees, is, I believe, the limit.
I am also using a home brew free-flow COOL air intake, which is an oversize K&N element in a sealed box using ducted outside air only. No hot engine compartment air. I've also insulated the air ducts and piping tp the throttle body with aluminum-backed pipe insulation. Looks kinda neat, like a NASA project.
So, there you have it. More mileage, torque and power for a 25 cent part on a modified engine.
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