Wedge TR7 EGR

[steve99]

I've been pondering disconnecting the EGR on my 79 TR7 as Wisconsin has no smog laws. Is there any relevent benefits to doing this, and if I were to do this, would I need to re-jet the carbs?

 

[Mark Beiser]

As long as the valve itself isn't leaking, you can just disconnect and cap the vaccume line to it.
You will get a slight increase in power, nothing big though.
You shouldn't have to touch the carbs at all.

 

[mailbox]

On many car built in the late 70's and early 80's if you disconnected the EGR valve, you would have a problem with pre-ignition or spark knock. Try disconnecting the vaccum line as Mark has suggested. If it starts to rattle under load, you might be better off leaving it hooked up. Just a thought.

 

[Paul Johnson]

Ah, the EGR. When the catalytic converters were added in 1975, engine operating temperature had to be increased. The cat begins to work at about 600F. You may remember that engines normally used to run about 160 or so, and then jumped up another 30 degrees. The job of the EGR is to carefully meter back into the combustion chamber, just enough burned exhaust gas to keep the operating temperature a little cooler than would be the case normally. If the temperature rises, oxides of nitrogen (NOX) will form, but if it gets too cool, carbon monoxide (CO) and hydrocarbons (HC) will increase. CO is partially burned fuel, while HC is unburned fuel. The metering of the valve is calculated by engineering in the development stage. If you plug it off, there will be no exhaust gases (typically about 20% is what everyone uses) in the combustion chamber, and that space will be filled with combustible gas/air. This means that the flame front will be hotter, engine temperature will rise, as will NOX, and you'll very likely begin to hear pinging, which is very ungood. Increase in octane might help, but might not. Lowering the timing might help, but then you've lost what you gained. If you just gotta, gotta do it, then put a bb into the vacuum source to the valve, and make sure the valve is closed and fully seated. Then listen for pinging and make your choices as things develop.

 

[Mark Beiser]

Duno about the pinging with the TR7 engine. The US spec engine with EGR is lower compression than the UK spec with no EGR. *shrug*

 

[steve99]

Thanks for the input guys. I've got till about the middle of next month (if I'm lucky) until I can get the vehicle out of cold storage. When that event occurs, I'll disconnect and post my findings.