ping

[88grandmarq]

eliminating the EGR all together is a bad idea, unless you have a chip made to turn EGR off in the ECM.
found this posted on corral.net

Quote:
"you shouldn't run the block-off unless you're either not running EGR or there's an alternate supply for it, because...

...the fuel management strategy assumes the presence of a functioning EGR system and you'll get an overly lean part-throttle cruise if you block it off and don't have a chip tune to tell the computer not to...and when you have a lean part-throttle cruise, the EEC picks that information up from the O2 sensors and adds fuel. But it doesn't just add fuel to part-throttle cruise operation, it adds compensating fuel even during open-loop (non-O2-feedback) conditions such as startup, idle, and WOT.

Short story is since the EEC assumes a functioning EGR, and if you haven't instructed it otherwise, you're setting yourself up for rich running and resulting performance/driveability issues by blocking off its flow."

[Blaze86Vic]

What does it mean the block off? Like blocking off the EGR? And how can the EEC assume it's working when it has a sensor that tells the ECU at all times weather it's working or not?

[OVERKILL]

That's not entirely clear there. Though the higher ratio rockers make their largest impact ac full lift, that not only is irrelevant o clearance issues, it also is irrelevant to the max flow rate in some applications, as their is a max valve lift that results in higher flow. At some point in the lift you don't get anymore flow no matter how much more you open it, because something else is the bottle neck. THE BIGGEST advantage of higher ratio rockers is that the valve opens faster. This means as the valve is chasing the piston down or up, it's now moving faster than it was with the 1.6 ratios, so using 1.7 ratio rockers can in some situations cause interference where a 1.6 may not, even with the same heads, pistons, cam.

Yes, the increased ratio makes the valve open and shut "faster", but it doesn't have very much effect on low-lift numbers, which is where interference occurs. If you are going by the standard spec of .085 for clearance, 1.7 or 1.6 ratio isn't going to make a difference at the low lift points, like a maximum of .010 or so, and that still means you won't have interference. If you DO have interference then you do NOT have adequate clearance PERIOD!

Plot it, that's the best way to understand it. Take a cam and plot it's pattern with 1.6's and 1.7's and then look at the values within 30 degrees from TDC either way. There is almost no difference between the two ratios at that point
and that is the range that piston to valve clearance issues typically occur.

If it's not clearing with 1.7's, it's not safe to run it with 1.6's, because if .010 is all you have for clearance........ That's just not safe.

[1987LTDmasta]

eliminating the EGR all together is a bad idea, unless you have a chip made to turn EGR off in the ECM.
found this posted on corral.net

Quote:
"you shouldn't run the block-off unless you're either not running EGR or there's an alternate supply for it, because...

...the fuel management strategy assumes the presence of a functioning EGR system and you'll get an overly lean part-throttle cruise if you block it off and don't have a chip tune to tell the computer not to...and when you have a lean part-throttle cruise, the EEC picks that information up from the O2 sensors and adds fuel. But it doesn't just add fuel to part-throttle cruise operation, it adds compensating fuel even during open-loop (non-O2-feedback) conditions such as startup, idle, and WOT.

Short story is since the EEC assumes a functioning EGR, and if you haven't instructed it otherwise, you're setting yourself up for rich running and resulting performance/driveability issues by blocking off its flow."

someone is going to be tuning my ECM in the near future. If i somehow get some extra cash tho i'll be tuning it myself with the tweecer

this will take care of the EGR.

[OVERKILL]

The EEC doesn't assume that the system is functioning absolutely though, it will if you leave everything hooked up and the valve is buggered and not actually letting any EGR gases though, but if you physically unhook the EGR valve position sensor, the ECM assumes it is NOT working and will not throw additional timing at it. Unfortunately, on cars with a CEL, this will trip it.

A lot of people in the Mustang world will unhook the EGR and use a resistor in-line with the wiring for the EGR position sensor to tell the ECM the valve is closed. This prevents a CEL and since the ECM thinks the valve is closed, no additional timing is thrown at the engine.

This topic has been covered in GREAT detail on the Corral, and one of the guys who has provided his input is an Electrical Engineer for Ford.

[1987LTDmasta]

The EEC doesn't assume that the system is functioning absolutely though, it will if you leave everything hooked up and the valve is buggered and not actually letting any EGR gases though, but if you physically unhook the EGR valve position sensor, the ECM assumes it is NOT working and will not throw additional timing at it. Unfortunately, on cars with a CEL, this will trip it.

A lot of people in the Mustang world will unhook the EGR and use a resistor in-line with the wiring for the EGR position sensor to tell the ECM the valve is closed. This prevents a CEL and since the ECM thinks the valve is closed, no additional timing is thrown at the engine.

This topic has been covered in GREAT detail on the Corral, and one of the guys who has provided his input is an Electrical Engineer for Ford.

i think i may just plug up the EGR for now then. its on there, but no vacuum lines. thats how it was before the HO conversion.

i dont have a CEL to worry about tho.

BTW the CEL will come on during cruise even wtih the resistor. the ECM will command the EGR vacuum solenoid and if it doesnt see any change in resistance, then it will command the CEL.

[OVERKILL]

i think i may just plug up the EGR for now then. its on there, but no vacuum lines. thats how it was before the HO conversion.

i dont have a CEL to worry about tho.

BTW the CEL will come on during cruise even wtih the resistor. the ECM will command the EGR vacuum solenoid and if it doesnt see any change in resistance, then it will command the CEL.

I haven't done the mod myself, so if that is indeed the case well, then I guess it coming on periodically during cruise is better than it being on all the time

[gadget73]

Thats how I was running, EGR valve in place, but no vacuum line connected. Something was freaky with my setup and the EGR valve insisted on being 100% open at any speed above idle, which made the car almost completely undrivable below about 60 mph. I tested and fiddled and eventually said F this and capped the line off. I'll re-visit the problem when the engine is back together and making proper vacuum. Might be a crapped out position sensor, its the only thing left to check on the system. Honestly if the EGR system is functional, you will lose nothing by leaving it in place. I'd run it with the HO setup unless it causes problems.

[1987LTDmasta]

Thats how I was running, EGR valve in place, but no vacuum line connected. Something was freaky with my setup and the EGR valve insisted on being 100% open at any speed above idle, which made the car almost completely undrivable below about 60 mph. I tested and fiddled and eventually said F this and capped the line off. I'll re-visit the problem when the engine is back together and making proper vacuum. Might be a crapped out position sensor, its the only thing left to check on the system. Honestly if the EGR system is functional, you will lose nothing by leaving it in place. I'd run it with the HO setup unless it causes problems.

mine has never worked since 1999. i dont plan on making it work. all my problems are solved.