egr mod
 

Where can i find the instructions for the egr mod for my 1995 audi 90 fwd 211,000 miles. I already gutted the cats. I have access to a 66,000 mile exhaust and egr valve. What would you recommend at this point, the egr mod or the new stuff? Thanks, Jay

search the forum archives "EGR mod"

Re: Cat gut, new stuff or EGR Mod & instructions...
 

You gutted the cats because they had failed already? Your '95 has a set of two; second (aft) O2 sensors which review the work of the first (forward) set of O2 sensors and the cats. I would think you would want to restore that functionality for performance, emmisions and economy.

As for new exhaust versus EGR Mod. They are not contradictory, so perhaps do them both. The new exhaust will allow you to more easily pass e-tests; and you do the better thing to the air we breathe.

The EGR Mod is just plain good preventative-maintenance for the EGR System, nothing more. New exhaust components in your case are a basic hardware requirement. A proper functioning EGR system will save you fuel as well. The mod itself takes mere minutes to do.

Are you sure your current EGR Valve is bad? You can find plenty of searchable EGR and EGR Mod info on the sister 12V forum here at AW.

The '95 is OBDI And while it has 2 cats it only has pre-cat sensors and not aft-cat sensors. OBD II started with the '96 12V. Post-cat sensors began with OBDII.

The "EGR Mod" was shot down in flames as doing nothing about 4 years after the old wives tale surfaced. The original designer "thought" the EGR solenoid sucked in hot exhaust gases from the EGRV and deposited it into the intake tract when the valve vented. Well, as we all know it only draws in vacuum from the EGRV vacuum diaphram which is a completely different/sealed compartment from the EGRV exhaust gas chamber... Its a "goes-nowhere/does-nothing" modification.

I gutted cats because they were clogged, cause bad performance. But now i have nasty hasitation off the line when cold, after warm-up it is fine. Yes, the 95 is OBDI and has pre-cat sensors and not aft-cat sensors. Is the o2 sensors being adversely affected by the lose off the cats? Current egr might be bad because I'm only getting 18mpg combined driving.

Post-cat O2s & the does something EGR Mod...
 

Thanks for that correction Mance, my mistake, I thought the later cars (immediately after my '93 for instance), had a 2nd set of O2s. Darn, I was hoping to gain those features with a later '90!

With regards to the EGR Mod however, I still do recommend that it be incorporated into every equipped 12v because of three simple reasons:

a.) It costs nearly nothing;
b.) It takes very little time; &
c.) The EGR Mod then allows the EGR Frequency Solenoid Valve (N18) to inhale relatively clean air from the engine compartment, rather than oil-misted air from the Noise-damper as per it's OEM connection. This vacuum-relief occurs every time the EGR Valve closes (which can be several times per second), and is the occasion where oil-mist is pulled into the Freq. Valve and beyond; and leads to it's early demise. It fails because even this tiny amount of oil causes the Freq. Valve's interior seal to lose that ability to isolate between vacuum and atmospheric. See failed N18 Solenoid disassembled to show the internal seal which fails in photo at link:

https://forums.audiworld.com/picture...ctureid=174563

Despite that the mod's original author called it's purpose incorrectly, the net result is entirely positive, as EGR Freq. Valves are not cheap to replace, nor should they ever need replacement do to this unfortunate factory mistake. The Freq. Valve is not the only component to suffer from the original plumbing configuration.

For those wanting to learn more about their EGR System function, here's my experience:

https://www.audiworld.com/forums/sho...php?p=22438033

Other manufacturer's have "commented" on "the Mod" and voted with their OEM hardware, as detailed previously here:

https://www.audiworld.com/forums/sho...highlight=Ford

...other manufacturer's install dedicated air-filters <i>just</i> to prevent this exact failure mode of internal seal failure due to oil contamination.

Furthermore, after your Freq. Valve has failed, your EGR System does not function, your CEL is illuminated, you cannot pass an e-test; you have a constant vacuum leak; you will have drive-ability issues if your EGR Valve itself is stuck open; <i>and</i> if you wait until then to do the mod, you will also have an un-metered air-leak into your Intake System.

All of the above is entirely preventable by this simple little mod. Many thanks to Mori & to Austinado for their persistance! Not many mods allow you to march out to your car, throw open the hood, yank off a hose, get all the above benefits, and save 100+ bucks on a new replacement part that you now don't need to buy! Dare I say perhaps the best mod ever!

So in conclusion I would argue that the EGR Mod itself was never shot down in flames, but that due to the detailed contributions of fellow forum members being able to build on each-others knowledge, our understanding of the EGR System function has grown such that we better appreciate the perhaps unintended brilliance of why the famous EGR Mod actually works!

You're totally right about relieving the solenoid vacuum with cleaner engine air than the crankcase blow-by gases at the TB inlet! Over time that pays H-U-G-E dividends!

I had to go check my car as I've moved all the evaporative emissions solenoids from the MAF mounting bracket to the firewall. Yep, that mod followed the solenoids. Additionally I run a small micro particulate filter over the EGR solenoid vent inlet. But unless the engine is highly modified people "should" retain the x-over provision. I only converted when it became a detriment and adversly affected 15MPH-60MPH 2nd gear ET's.

Pic shows my vac X-over solenoid completely capped off as I no longer use manifold switchover provision and running no high-RPM butterflies in the IM. However, with OEM engine management you'll have to run power to the x-over solenoid or otherwise deal with the resulting CEL. Tho its possible a jumper wire between the 2 harness leads might eliminate that... I can't remember.

Further I would suggest/recommend this particular modification be given a new name or referred to as something other than EGR mod. That proper name's time has come to an end. Reason being, 1; "EGR mod" least to me conjures thoughts of the EGRV being tampered with, altered, changed or modified somehow. 2; Due to the term's origins any effort to use the search feature now and for all time is destined to produce vague, ambiguous and/or totally wrong findings and 3; at first glance it instills the notion that somehow people's emissions compliance might be challenged, compromised or at the very least "could be" when little is further from the truth. IMHO I think it should be termed a little closer to what it is, ie; "EGR Solenoid-Saver" or "ESS-mod" and skip the EGR reference altogether! ANYTHING but EGR-mod! Anything that eliminates all the ambiguity/confusion that is created, aggrivated or compounded today just by the very mention of "EGR-mod." Call it something new from this point forward and leave any/all references to "EGR" and/or "EGR-mod" term out of the new name altogether. This and many threads to follow, ad infinitum, only promise to continue otherwise.

Re: Propose a new name for the EGR Mod...
 

That's a great idea. Perhaps something like Frequency Valve Vent Mod, since their aren't too many Freq. Valves out there. FVV Mod for short. N18 mod would work too.

Interesting info about your I/M cross-over butterflies getting in the way. As I remember you even doubled them up at one point for improved port-sealing; the theory, testing and practice of this latest configuration would make an interesting post some day to hear how you arrived there, and what the threshold was whereabouts they become an obstacle.

Is there a DIY for the egr mod?

VAP, that is one clean engine bay! :cool: