The OE,s have been using a EGR system to control knock for years, I'm wondering
if a EGR system would help control knock on a high power turbo street motor.

Tom, I'd like to get your input on this.

 

Lots of diesel engines have been using large quantities of EGR to cool the combustion charge/ suppress knock under high boost conditions.

Hardest part of the deal is the actual egr cooling strategy. Engines want different levels of egr under a vast range of rpm. One egr system does not seem to be able to do it all (unless you were maybe in a race only situation) and in that case you would use the cold water to cool the intake charge vs cool the egr in my opinion.

More info on what you are exactly trying to do with the egr in this street application.

Tom Vaught

ps Ford has a EGR Technical Specialist that I work with but I know little about the egr/ strategy side of the deal vs his knowledge.

 

Back when I was a tech if motor with no knock sensor had egr not working it would
knock like crazy. These motors would run timing in the mid 40's at cruse and part throttle.

And the systems with knock sensors would suffer from power lose and poor fuel economy.

Egr it a very effective way of controlling knock from what I've seen on N/A stock motors.

For a given home brewed hot rod combo water/meth as far as I know has been the only way of suppressing knock
on a pump gas street turbo car.

I'm wondering if egr would do a better job of knock control than water/meth or could
be used along with water/meth to further suppress knock.

I'm like trying different things and egr may allow safer power on pump gas.

If you get the chance ask you co-worker about this.

Thanks
Chris

 

Got a reference for that??? Do they do it at full power???

I've specifically used egr to control nox in industrial boilers.
Diesels run excess air so a little egr won't hurt power. Same as a boiler.
Typically stock cars run egr for the same reason. Lean afr's lower the HC but drive nox up so they add egr to lower combustion temps and nox correspondingly. I've also used water injection for nox control on medium sized gas turbines. The big ones use steam for nox control since the run hotter than the medium sized ones.

EGR won't add power unless you do have detonation... water will at least turn to steam and add some pressure to the cylinder.

 

Your right, egr won't add power but suppressing
knock will allow for more boost and or more timing
and that's where the gains come from in any know suppression system whether it be water/meth or egr.

Or if a guy was happy with his power level and would like a bigger safety margin egr may help.

one good thing about egr is there's no refills and no mixing ratio like water/meth.

 

If you guys don't mind would explain what the EGR is doing to suppress knock.

I know it works but I'm having a hard time rapping my brain around how hot exhaust gases
can cool the combustion process.

 

from my understanding it takes up space in the cylinder, so less intake air can fill the cylinder, when the spark fires it has a smaller amount of oxygen to burn (less oxygen to burn less heat), expansion is still high enough to make normal power and the now egr gas is at a lower temp than the combusting gas and the heat is transfered to that more easily than to metal components of engine. a net loss of over all heat in the exhaust, if you are trying your best to get as much air under boost into a performance engine, at usually great expense, any thing that takes away some of that ability couldnt be a good thing?

 

Check into the Detroit Diesel Series 60 with EGR. They run a variable nozzle turbo partially for quicker spool, partially to create more backpressure for the EGR system. This is more for emissions than it is for supressing detonation so they can bump up boost.

 

The VW turbo diesels use the EGR setup, it comes right off of the turbine discharge and goes through a cooler that uses the engine coolant to transfer the heat. I thought it was just to reduce emissions?

 

Typically EGR is a "Fuel Economy Fix" If you have 25% EGR in the cylinder you have 25% less "Good Oxygen" therefore the air/fuel mix can be adjusted for smaller volume of good air on that "Putt".

Using the EGR for Knock control will allow leaner mixtures so the F.E. goes up again. Same deal for allowing as was said more boost.

THE DEAL IS YOU NEED COOLED EGR! THE MENTIONED DIESELS ARE USING MASSIVE EGR COOLERS. (Still I bet you could find Diesel EGR coolers in some salvage yards pretty cheap). Last part of the deal is the EGR valve control strategy. The engine likes different amounts of EGR under different modes. Lots of papers on the internet about this subject.

Not really a Hot Rod trick but can help you get a bunch more F.E.

Tom Vaught

 

Also lowers combustion temps which reduces NOx emissions.

 

Agree on the NOx Emissions, Thanks.

Tom Vaught

 

Smaller engines won't use EGR at higher loads as its best to use as much fresh air as possible for making power. When you get into bigger engines, diesel engines that is they do run more EGR at higher loads, sometimes upwards of 60% EGR at higher loads. The new emission regulations are making it interesting for companies to make the requirements. It should be interesting to see how things turn out.

 

everyone i know with EGR on a big rig, Disables them.

Results are lower EGT, Cooler engine temps and increased fuel economy.

I firmly believe the sole purpose of EGR in a large capacity diesel is nox reduction, which comes at the expense of the above.

Also, service life IS reduced by the hotter temps.

 

My diesel's egr is disabled and the crankcase is vented to the atmosphere.
Dont no if I would trust a knock sensor. My 5.7 truck as well as my wife's 5.3 truck will both ping
on occasion, and if you can here detonation then thats bad right?

 

I would keep an eye on the oil in the crankcase, Patl, as removal of the PCV (Positive Crankcase Ventilation) offers no real performance benefit. Many racers today use special Crankcase Ventilation Pumps to make more power: better ring seal, etc.

Engines, many years ago, would last a few thousand miles due to the corrosive gases in the crankcase produced by the combustion process and then leaking past the rings.

A "Road Draft" system system was engineered that would pull crankcase fumes from the engine and a "Breather" / filter would allow fresh air into the crankcase.

The PCV system removed the corrosive gases better, burned them, and eliminated the oil residue build-up under the vehicle from the road draft tube.

There are some cases where the PCV valve could not flow the required air to remove the pressure in the crankcase as well as the corrosive gases. The Closed Crankcase Ventilation System CCVS addressed that issue by using a PULL-PUSH system. Normally the gases were pulled from the crankcase through the PCV valve and into the intake manifold. WHEN the crankcase had too much pressure, the gases "pushed" out the inlet hose into the air cleaner and were drawn into the system by the flow through the carburetor or throttle body. Diesels have unique crankcase venting strategies.

Tom Vaught

 

I understand the question at hand, but why not just switch to E85. From what I read detonation, combustion temps, EGTs and knock are all controlled with E85. The downside is some places don't have the same availability as others. Just a thought.

My buddy has a GM 3800 supercharged in an 86 Fiero he recently (a month or so) switched to E85 and then went to the 15lb pulley. His knock retard issue is non-existent. The ecu would pull damn near all the timing now it adds more than it took away. His engine runs way cooler and I am sure the combustion temps dropped too. He used to fill up every 3 days now it is every 2, BUT he is in the pedal alot more as well and he has an 8 gal. tank. Just a thought.

 

What is the proper way to modify an OEM PCV system after adding a turbo? A lot of guys use catch cans with breathers. How can you retain the benefits of a functioning PCV system? Check valves? Part numbers?

 

Ford offered some PCV valves in the 1996-2000 time period (OEM) that were sealed in one direction of the flow. The valve in the normal vacuum mode would allow Crankcase fumes
from the engine to be drawn through the PCV and into the intake manifold.

Under boost pressure from the intake manifold, the PCV valve would seal completely and not allow boost pressure into the crankcase.

Any excessive pressure (from the crankcase) would travel OUT the normal inlet hose to the crankcase and then through the boosting device. This would relieve any pressures in the crankcase and eliminate crank seal, oil pan gasket, and timing cover seal oil leakage.

Yes, you can successfully make a PCV system work properly. The KEY IS THE PCV VALVE AND MAKING SURE IT SEALS IN ONE DIRECTION.

Tom Vaught

 

This is a good question. I guess it varies application to application depending on how good the factory check valve seals. Adding a brake booster check valve is required on some applications.
The vent side can be a problem as well, enlarging it to add more breathing under boost seems to make the PCV valve leak more vacuum than it should (making life difficult with idle AFR etc.).
So some PVC flow adjustments maybe needed when the vent is enlarged.

Thats why I'd rather have the vent hooked to the turbo intake so the crank case can enjoy the negative pressure caused by the compressor sucking on the filter.

As far as catch cans, a sealed PCV one with separator (scotch brite pad sandwiched between some sink screens has worked well for me) on the intake side seems to be the best IMO.
As far as the vent side make sure its baffled or install a separator like mentioned above.