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1976 Wagon with 308.000 miles!

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Hey guys. Look into JEG'S or any other racing equipment outlet and you will fine VACUUM pumps designed for this purpose. And that is to keep a vacuum in the crankcase!! Read up on it too.. They claim to gain up to 14 or so horses!

Modify Your Engine’s PCV System to Gain up to 17% MPG
The idea is to reduce our country’s dependence on foreign oil and save you money. I do not want your money in any way.

Now that you understand where I’m coming from, here’s the deal… Would you spend about 20 minutes and under $10 to modify your vehicle’s engine, and gain 5 – 17% increase in miles per gallon? There is nothing to wear out, replace, clean, renew, or change ever again. This is a one-time modification that will last for many years.

Still interested? Read on.

In the very competitive game of bracket drag racing, the engines are covered by many extremely restrictive rules. Any small horsepower gain that can be found within these rules is a huge advantage. Reduce the internal “drag”, or rotational resistance, and you have a more efficient, more powerful engine. Some “old” drag racers have known this for a long time. They have been connecting vacuum pumps to their engines for an overall gain of nearly 10 horsepower. Small gain, yes; but an advantage of about 5%!!

In this application, we will put the engine’s own Positive Crankcase Ventilation (PCV) system to work for us. We use the PCV system to reduce the pressure inside the engine’s crankcase, thereby reducing the quantity of air that must be displaced by each piston as it travels downward. With the reduced air resistance within the engine, it naturally rotates easier.

So, how do we do this?     What you need to understand is how the PCV system works. It pulls filtered air into the engine block. This purged air is then pulled into the intake manifold, where it is burned in the engine. Simple, all we have to do is cap, or plug this airflow INTO the engine’s crankcase. This is usually done with a small (1/2”) tube that leads from the airbox (or downstream of the air filter) to the engine. It is generally connected to the engine on one of the valve covers. By capping this tube, be certain that you are preventing air infiltration two ways: into the tube leading to your valve cover; and into the air intake, or airbox. Because we don’t live in a perfect world, make sure that all the tubing connections are tight. Let me go beyond that, they need to be VACUUM TIGHT. This may not be an easy task on older vehicles, as I will explain later, but well worth it.

We are now causing the crankcase air pressure to be changed from near atmospheric to at least -4” mercury (HG). The manifold vacuum usually runs at about -24” HG at idle. This is transferred to the crankcase by blocking the air flow. (The nasty vapors are still drawn off and burned in the engine, so the emissions have not increased, and the EPA will be happy.)

Does this REALLY work?    The first engine I modified is my 1976 Pinto with a 2.3 liter 4 cylinder. (Yes, they still DO exist!) This engine now has 291,000 miles, and runs as well as anything else on the road. I probably have driven about 1,200 miles since I capped the PCV, and I have seen no increased oil consumption, or other adverse effects. This is a true high-mileage engine with plenty of wear and blow-by. In my mind, if any engine is going to bite the dust through this, here is a classic case. (I wasn’t especially worried because I have a rebuilt engine awaiting the day this old one dies). The around-town MPG increased from 21 - 23 up to 25 - 27, depending on the temperature. (Since this is a carbureted engine, the choke does play a role in economy). After the first tank of fuel, the MPG dropped back down to the normal (22 MPG) range. Slightly discouraged, I took a closer look at the whole PCV system. What I found was a bit of a shock. The oil filler cap on the old Ford was set up for a hose to the air filter. I had simply blocked this at the cap. After a while, the oil that had soaked into the seam of the two-piece metal cap had been pulled out by the vacuum, creating a new air leak. I eventually replaced the cap with a non-breathable one from another application. This, along with being extremely aware that vacuum leaks are nasty little annoyances and, careful attention to the gasket on the cap, cured the leak. The crankcase vacuum now runs at -4 to-5” HG at idle. The in-town fuel economy again changed for the better! Back up to, per the latest tank of fuel, 26.49 MPG. Not bad for November…

I did this on my dad’s 2003 Ford Ranger. This is a two-wheel drive, 4 cylinder with a manual transmission.  He was getting similar MPG’s around town, averaging 22 to 23. In the latest report, he is still getting 26 to 27 MPG in town.

I want to point out that the on-board computer in newer vehicles doesn’t care about this modification! (The computer does not control or monitor the PCV in any way.)

In both cases, this is an increase of 17%

I honestly do not have enough data on highway mileage to conclude anything, but I suspect the increases would be slightly lower. More in the range of 5 – 10%, due to the decreased manifold vacuum at highway speeds.

Now for the possible down-sides of doing this, and what I have observed.

  Will the oil retain more contaminants?.    I believe it will. Since the PCV is not as effectively removing the volatile contaminants from the crankcase, the oil will become the reservoir for these contaminants. This means, simply, change your oil at the recommended intervals!

* The water vapor cannot as easily be purged from the engine.     When we look at how this water vapor enters the engine, it becomes very clear. It comes into the crankcase via the normal PCV system. Since we no longer have an open air inlet for this moisture to enter, I believe the water vapor that is now in your engine will be pulled out, albeit more slowly. However, the influx of water vapor is now nearly eliminated.
* What about a negative affect on the gaskets and oil seals?    Again, I have not seen any oil leaking from the Pinto engine. And I do mean that there is virtually ZERO leakage from the main seals (or anywhere, for that matter) on this engine. (I truly hate a leaky car.)
* Will I see increased oil consumption?     This old 291,000 mile Pinto engine has always used some oil, and I’ve driven the car daily since May, 1988. I can count on about 1,600 miles to the quart of oil consumed. This has not changed.
* Rough idle?   No, I think it actually idles a bit smoother.
* Why hasn’t Detroit done this years ago?     The auto manufacturers are after one thing, your money. They simply don’t care how much that new car costs to operate. 

I am only trying to pass along information that I believe is important enough to share with everybody who will listen. Again, I am not making a dime on this, nor do I expect to, ever. Please give this some thought, as a lot of fuel is potentially at stake. Consider at least trying it for a while.  My satisfaction will come in the knowledge that I may have had a small part in reducing emissions and our country’s dependence on imported oil. Any oil, for that matter! 

In reference to the previously mentioned negative affect on the engine’s oil seals… I have some new data to share.

Problem:  Rear oil seal leakage: I modified the PCV system on my Chevrolet S-10 class-C motorhome. The engine is a 2.8 liter V-6. In late July, 2006 we were leaving town for a long weekend of camping. I started to smell oil burning; never a good thing to experience! After finding a suitable wide spot on the highway, I noticed that the rear main oil seal was leaking quite well. Actually, it was nearly a steady stream of oil at idle. Now, please understand that we had driven this vehicle on a 7,200 mile tip across the US in September and October of 2004, with not a bit of mechanical trouble. This just had to be caused by the mods I had made to the PCV system. The process of replacing the original PCV system was done very quickly (it took about 10 minutes, tops!) and I proved to myself that it had indeed been the cause.

What had happened is this: the engine’s crankcase had a negative pressure that was actually opening the rear main oil seal. This seal is supposed to be held closed by the pressure of the oil pushing against it from the inside. But a deep enough vacuum pulled in air past the seal, allowing oil to be pushed out.

The oil leak immediately stopped, and hasn’t dripped in the 240 miles since. 

In fact, my 1992 Ford Ranger pickup and my brother’s Ford half-ton PU both have a distinctive “whistle” after we shut them off from an idle. This indicates a deep vacuum within the crankcase, with absolutely no adverse affects! In fact, my brother’s Ford pickup idles at about -20” HG., and this engine has no problem with oil leaks.  So, some engine’s oil seals just seem to be more sensitive to a vacuum.

I never did check the vacuum in the crankcase on the Chevy’s engine; maybe I should have. But I tend to believe it has more to do with the design of the oil seals than anything. I’ve chosen to run this engine without the PCV modifications due to the limited in-town or moderate loading of the engine. However, I have come up with a remedy, should this be a problem to others.

Cure:  I have researched the availability of an adjustable vacuum relief valve. They are a simple device that will prevent the crankcase vacuum from reaching below the valve’s setting. A ¼” NPT model is in stock locally for about $10 (Grainger’s). This will need to be installed in line between the valve cover and (preferably) the air box or air cleaner. If this valve setting is adjusted correctly, probably 6” to 8” HG, then it will open as needed at idle and downhill, etc. With the tubing run into the clean air stream, the engine will not have a new influx of dirt.

How are my other cars doing?  The old Pinto is still running flawlessly at 298,750 miles (as of 11/18/06). It’s still averaging right at 26 MPG in town!! This is not running on the highways; it is 99.99% stop-and-go city driving. The Ranger pickups are still running fine. We are still seeing a similar MPG stated previously.

What about the highway mileage? I really haven’t seen any increase in MPG over the 7,700 miles since I first modified the Pinto. But, there hasn’t been any DECREASE in MPG either. Our Ranger pickup; pretty much the same highway mileage, also.

Please feel free to copy and forward this to as many people as you wish!!!


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