Most of the engine modifications that I do are geared more towards increasing fuel efficiency. However, at the same time, none of the mods that I do will decrease performance. They do lend themselves to further increases in performance, though, due to more efficient combustion and reduced detonation tendencies which allows for a higher compression (static and dynamic) that's inherent with higher combustion efficiency.
That's why I put this in the Performance Forum.
I'd like to outline the mods that I've been doing and give some background on them. Let's follow the path that the air/fuel takes through the engine.
INTAKE
First I'll start with the carburetor. Most everyone knows that our side-draft carbs are pretty good at atomization (better than most). There is a way, however, to produce a "fog" instead of a mist coming out of the throat of the carbs. This has been outlined by David Vizard in his article at GoFastNews.com
HERE. Unfortunately the pictures are missing... But the theory is mush simpler than it reads.
In Cylinder Turbulence and Combustion Dynamics
The key to the increased atomization and reduced wet flow was the sharp and microscopically ragged edge of the jet and the relocation of the discharge point within the carb body. By moving the jets discharge point away from of any nearby surface that the fuel might attach itself too prior to becoming dispersed in the air produced better down stream dispersion. So how was the atomization produced by this set up? The fuel left the jet like a fog. Where as flash photo’s had revealed small droplets in the stock Stromberg’s discharge from the jet the revised design showed none as the droplets were far too small to show as such. On the chassis dyno the results were very encouraging. With the hot spot in place the new carbs dropped about 3 - 4 hp. With the hotspot blocked an increase in output, by virtue of an increase in torque, amounting to some 14 hp was seen! So what we are seeing here is that mixture preparation in conjunction with temperature, is contributing to a better combustion process to the tune of some 20% increase in output. In addition to this drivability, throttle response and part throttle fuel economy were all improved.
At this point the value of not only a cool intake charge carrying the correct mixture but also one having (on average) appropriate fuel droplet sizes and dispersion of such for the engine concerned is showing to be a distinct advantage. So how did all this work out on the track? The carb changes along with a whole host of selected and/or blue printed parts netted a totally legal engine that would leave even highly illegal cars for dead in the water. The first time out with this engine we put the champ from two years previous who was supposedly the 'King of Mallory" , with, what we later found to be a highly illegal engine, down by about 200 yards per lap.
This will be the toughest mod that I do to my bike, as I'm not extremely experienced with disassembling my carbs (and the jetting requirements will be drastically altered towards the lean side). It will, therefore, be the last thing I do.
The second one is done to the intake ports. It's called "Power Lynz" and was developed by Mike Holler. If you can envision screw threads running down the length of your intake port, that's basically what this is. The "threads" run perpendicular to the airflow to help stop liquid fuel "flow" and to create what Mike calls a "variable boundary layer."
Powre-Lynz
Back in about 1998 I purchased a product called the Power Plate. I installed it on my already modified ’70 Duster with the 225 /6. I rebuilt the engine, did some head port work (very conventional), slightly larger cam (252 M Comp Cams), 0.030” bore with otherwise factory style cast pistons, factory exhaust manifold, 2 ¼” exhaust, factory /6 2-bbl carb with factory 2-bbl manifold, OD 4-speed, and electronic ignition. With the addition of a screen under the carb, I took the Duster from a stock 17 mpg to a best of 29.8 mpg. I bought and installed the Power Plate and immediately felt a substantial increase in power and went to a best of 44.7 mpg! (I’m mpgmike, mileage is important to me.)
The Power Plate was a 1” aluminum spacer that went between the carb and intake. It had a coolant jacket with a coolant inlet and outlet. They were “T”d into the heater core hoses. There were tapered cones under the throttle plates. The cones were 8 degrees with a 20 pitch thread turned into them. The cones extended about ¾” under the throttle plate gasket.
As good as it worked, I realized that most of the vehicles on the road were PFI, and the Power Plate principle would somehow have to be placed between the fuel source (fuel injector) and the combustion chamber. It took me about 2 years to come up with the Powre Lynz concept. I had LL Brown (the company making the current batch of Powre Lynz tools) make me up a single tool that had the 20 pitch thread, with a ¼” shank that I could mount in my die grinder, and a 3/8” X 1” head with a domed head. I did several sets of heads with just the 20 pitch with very encouraging results:
Dez: ’89 LeBaron, 2.5 turbo, 180k miles. Ported head, ported factory exhaust manifold, ported 2-piece intake (said porting done by me). Dez added larger turbo, injectors, FMIC, custom cal, water/meth injection, and a few other minor mods. He went from factory 156 HP, 23 mpg city, 27 mpg hwy to 430 HP @ 27# boost, 35 city, and 43 hwy. He destroyed 2 413 ATs before wiping the 180+k bottom end.
Fltcoils: older gentleman, so no power numbers, ’88 Sundance 2.2 TBI. Stock 25 mpg city and 29 mpg hwy. Modified got 35 mpg city and 42 mph hyw.
Diamondlarry: (2 heads) ’96 Saturn SOHC 1.9 L, 38 mph hwy stock, 65 mpg hwy modified. Noticeable increase in power. Done with only the 20 pitch Lynz.
Diamondlarry: ’99 Saturn DOHC 1.9 L, 34 hyw stock, 57 mpg modified. Registered 130 HP stock (accelerometer) and 165 HP modified.
These are the only numbers I received, but I had anctedotal reports of really incredible results from well over a dozen other individuals (without documentable numbers).
I did get results when I was only using the 20 pitch thread Lynz tools that under certain operating conditions, power and mileage improvements were considerable, but under heavier loads, the results seemed to go away. That got me thinking about the thread pitches and what could be done. I had LL Brown make me up a set of Powre Lynz tools that included a new 20 pitch, but also 16 and 12 pitch threads. Now I could tailor the pitch to the velocity zones in the ports. Results got much better. Higher velocity zones, such as short-side radius’ were treated with a coarser pitch, while slow velocity zones were given the finer pitch Lynz.
Benefits seemed to improve across a much wider operating range. I was definitely on to something. I’ve worked on Toyota VVT-I, Mopar 2.4 head/2.2 block hybrid, Saturn DOHC, Viper V-10, 8-valve 2.2/2.5, SB Chevy, 3.5L V-6 Chrysler, and probably others (I’m going from memory here, so bear with me). Based on feedback, I formulated what pitch was appropriate for what range of velocity zone. Some of the heads were performance oriented, and others were strictly fuel economy oriented. The more feedback I received, the more I knew I was onto something big.
I ported a 2.2 8-valve head and added the Powre Lynz and sent it up to my machine shop to be flowed. I requested them to flow it at 10” water column pressure, then at 28” and finally at 40”. Their 3-pump flow bench was unable to get results at 40” and maxed out at 34”. To convert 10” to the industry standard 28”, take the 10” numbers and multiply by 1.67 and you will get numbers very close to what you’d actually get flowing the same port at 28”. When they flowed this head at 10”, the 28” equivalent were about 138 cfm. This is barely comparable to a stock head (about 142 cfm). The one I sent them was ported. HHHhhmmmmm!!! When they flowed the head at 28”, the numbers came in at 182 cfm. This is comparable to many porter’s best work (excepting Steve Menegon, of course). The difference between 28” and 34” was insignificant (28” numbers X 1.1 = 34” numbers). Maybe it just wasn’t that much of a jump like 10” to 28”.
What this suggested to me was a variable boundary layer. Fact: My ported heads always flowed better at 0.100” than everybody elses (including Menegon’s). This was with the Powre Lynz, as I was using conventional 3 angle intake seats and 5 angle exhaust seats with mild back-cuts on the valves. It appeared that at low flow conditions; low valve lift or low throttle body opening; the boundary layer constricted causing high velocity (a good thing), regardless of the size of the actual port. As the engine demands increased, the boundary layer collapsed allowing additional flow.
I hope this helps.
Mike
The next thing the air/fuel has to contend with before it can be used, is the valves. We all know that the valves are there to contain the combustion process. However, most fail to realize that they have a noticable effect on the chamber-delivered mixture. Smooth, polished valves tend to "catch" liquid fuel and allow it to "drip" into the chamber instead of keeping the fuel mixed with the air (the same reason polished ports are bad). This generally doesn't effect performance to a large degree, but when you're concerned with combustion efficiency, a little drip can make a huge difference.
Metric Mechanic developed a modification that is very similar to Mike Holler's Power Lynz, though it's designed for the intake valves. He calls it
Surface TurbulenceSurface Turbulence
In August of 1988, Surface Turbulence became standard on all Metric Mechanic engines. By using Surface Turbulence we've been able to lean out the engine and burn much of the wasted (emissions) fuel. This has also reduced the fuel input into the engine by 10 - 15% under moderate (part throttle) driving conditions and up to 25 - 30% under full load (wide open throttle). Surface Turbulence in an internal combustion engine is generated by causing a rhythmic tumbling action over a surface or object. This tumbling, set in motion by a surface turbulence generator, accomplishes the following:
- It re-homogenizes the fuel and air.
- It reduces laminar flow.
Instead of air dragging, it now tumbles over the surface of the valve - like a layer of tiny spinning ball bearings. Over such a surface, the main stream can now move at full speed. Also, as air flows over these ramps, the fuel mixture hits the backside of the valve and is kept homogeneous by the tumbling that the grooves generate. Having fewer heavy particles, the homogeneous mixture burns more completely. So, the effect is that the "boundary layer" which is normally lost in airflow with a conventional valve, now has an airflow gain of 2% - 4% by using the HiFlo ST Valve.
On a conventional intake valve, as fuel leaves the fuel injector or the discharge Venturi of the carburetor, it is atomized into the "main stream." This mixture is either taken into the cylinder through the opening created by the valve and the seat, or the mixture runs into the backside of the valve. Fuel hitting the backside of the valve is then knocked out of suspension. Because the air flowing over the face of the valve is moving so slowly, fuel particles tend to adhere to the valve's surface. Eventually there are sufficient fuel particles collected on the valve to grow heavy enough to be shaken off the valve, due to a beating action against the seat. Or they get swept off by the "main stream". Since these heavy fuel particles aren't very combustible, they're wasted in part!
Here's a pic of the back-side of a ST valve:
http://www.sheenconsulting.com/car/pics/ValveTopST.JPGYou can see the chamber side of the valves in the pic further down showing the ST combustion chambers.
The first three mods both help keep the fuel and air well mixed throughout the intake tract. Once the air/fuel mixture gets into the chamber, it needs to stay that way.
CHAMBER
Turbulence and Combustion Dynamics
The first point to note is that the cylinder’s charge does not explode when the plug fires. It burns - and it in no way resembles an explosion. In a Cup Car engine at peak rpm, the charge across a 4-1/8 inch bore burns at approximately 150 mph. An explosion is something that ignites at over 2000 mph and dynamite burns a whole lot faster than that. At a 700 rpm idle the flame speed barely makes 10 mph! This is why we have distributors with ignition advance curves.
SCR
Without turbulence in the combustion chamber we would burn the mixture at the laminar burning rate which is ten to twenty times slower than the turbulent rate. This would make practical engines that rev higher than about 1500rpm an impossibility.
Pistons -n- Chamber Design
The ability to induce the proper swirl frequency and depth of rotation is paramount to maintaining a layered homogeneous mixture which will provide a lengthened primary burn followed by a rapid secondary burn, all of which will yield considerable resistance to detonation, greater over all combustion efficiency and fewer bad guys coming out the exhaust. The over all time of burn is so short and complete that the spark advance may be reduced to the extent that you're not doing as much "negative work", and the exhaust gas temperatures generally are in the 800 degree area, which means that the heat of the burn provided considerable better thermal efficiency, and something we and our competition noticed early on was the sound of the exhaust....it was almost a "whisper" rather than what you'd normally hear from an un muffled race engine.
I cast some small block Chevy heads back in the mid 80's, and although I did rotate the deck to lessen the 23 degree valve angle, and reduce chamber volume. The plug position was optimized, and of course the ports were adequate, and the inlet ports were properly biased to promote swirl. The pistons were "unique" in shape...all I'll say is they had no dish, except two .120" valve reliefs. They were certainly of the domed variety. Those small blocks were 358 cid. engines with 1.75-1 rod length to stroke ratio, very short cam timing...235 degrees @ .050", and the intake manifolds were some of my Edelbrock "specials" with Murray Jenson prepared Holley 830 cfm carbs. Those engines had "over" 16-1 static CR, and dynamic compression was so high we had to use custom starters run off 24 volts.
They were installed in some Camaros and two pick-up trucks. They all ran 91 octane unleaded pump gas. They never detonated; the mileage was 37 (combined) for the cars and 25 for the trucks. The Camaro's had Turbo 400 automatic transmissions, and from off idle you'd swear that there was at least a 454 under the hood...the throttle response was almost too quick. Those "loaded" cars all ran 12's with ease. The trucks had pulling ability that no body imagined, and were a dream to drive, especially compared to their street counterparts.
So, yes. If something as crude as a small block Chevy can be that efficient, some of the more "modern" chambered heads can certainly do the same and considerably better.
These two posts alone should demonstrate the importance of chamber turbulence. Knowing that the air/fuel burns more slowly at lower RPM and at part throttle, it should be clear, that increasing the burn rate will help part-throttle performance and efficiency. Chamber turbulence is good, as it speeds combustion by mixing everything up very well. While I don't have the resources that Mr. Widmer has, I'm working with what I have available. The combustion chambers (below) have been modified with Metric Mechanic's Surface Turbulence.
Now that the air/fuel has made it into the combustion chamber, the piston is moving up in the bore and starts to compress the mixture.
PISTON/COMPRESSION
Now to the more local work... Soos machined a set of late-model SOHC 750 pistons to work in my CB650. They are a little more "unconventional" than most, however.
http://forums.sohc4.net/index.php?topic=63523.msg714245#msg714245
You should be able to recognize my pistons when compared to the more conventional models. As you can see, there is more Surface Turbulence in the top of the piston to further maintain mixture motion and homogenization. The added turbulence keeps the air/fuel well mixed while combustion starts.
When it comes to combustion speed, I can't say it any better than Larry Widmer.
The Soft Head
If the combustion process is quick and complete, there will be very little burning when the exhaust valve opens, and the exhaust gas temperature will be very low. A quick burn also permits us to use less ignition timing advance to complete the combustion cycle and, therefore, the engine is doing less "negative" work since we’re not trying to compress as much ignited and rapidly expanding mixture. Unfortunately we can’t light the mixture at TDC and still complete the burn by BDC (with gasoline), but we can run only 5 - 15 degrees advance and create a thorough burn cycle.
Once combustion is underway, the added turbulence increases the flame front speed and makes for much more efficient combustion. This further adds to thermal efficiency by producing chamber pressure where it is needed. These specialty pistons assure that plenty of kinetic energy is transferred into the mixture thereby increasing turbulence and burn rates.
IGNITION
Once all of the air/fuel has been mixed, ingested, and compressed, the plug needs to start the fire. Though all of the modifications help produce an easier-to-light and quicker-to-burn mixture, no matter what you do the mixture will never be "perfect" 100% of the time; there will be some variances between combustion events.
While my engine will have more turbulence than the typical Hemi-chambered Honda SOHC4, there will undoubtedly be room for improvement in the ignition department.
Practical Plasma Power
To burn the charge of air and fuel as effectively as possible means delivering as much energy to the plug as possible up to the point of overkill. The question here is what is totally sufficient and where does overkill start? I have done a lot of ignition testing in my time and in almost every instance it seems that a bigger, fatter more aggressive spark produces better ignition. Sure I have come across some notable exceptions here. Two that come to mind are the ‘A’ Series Mini engine that powered the original Mini Cooper and the big block Chevy with a certain type of factory head (casting number escapes me for the moment but if you are into real high performance you are unlikely to use them). In both these instances I found that at first the combustion got better as the spark got better but after a point not that far up the scale in terms of spark technology and delivery all gains topped out. On the Mini engine it seemed that once we had a good strong spark that even lightening bolts would show no improvement. On the particular engine involved we went all the way to about 21/1 fuel air ratio’s before any sign of a lean misfire was experienced. But that’s not the norm it would seem – especially for the modern multi valve engines with limited mixture motion and a centrally located spark plug.
To better understand what we are dealing with here let us consider what a conventional high performance ignition delivers to the plug. A typical modern high performance ignition system (factory or aftermarket) that we might categorize as a grade ‘A’ system will dump between 40 to 50 watts into the plug gap. This will produce a spark that is typically around 3000 to 4000 degrees Celsius.
To create an extreme temperature plasma spark of the type we are calling for here requires a lot more wattage in the plug gap than is produced by a conventional ignition system. The problem is that once the voltage at the plug has risen to the point of breaking down the resistance at the gap we find that once it fires across the gap it becomes, to an extent, self canceling. The spark will fire across the gap but the fact it has ionized the gap means the resistance within the gap had dropped. The spark characteristics in this secondary ‘after burn’ phase are not conducive to lighting off the charge.
For the ignition I'll be modifying my own. I already have an Ignitech programmable ignition unit which provides me with complete control over the timing curve as well as vacuum advance once I get around to tuning for it. However, I'll also be utilizing a "High Voltage DC" ignition booster of my own design which I can adjust to the point of melting the plugs in a couple of minutes. I'll obviously have it "turned down" to make the plugs last. I'll demonstrate this once I iron out all of the kinks.
Distributor Curve Science Simplified
When you back out of the throttle the manifold vacuum goes up. This means the compression pressure at the end of the compression stroke is way lower. When a spark timed for a normally fast burning charge (as it is at WOT) fires under these circumstances it is going to occur far too late for the pressure to be at it’s peak at 15 degrees after TDC. This means that less than optimal use of the energy content of the fuel has been made. That in turn means burning more fuel to get the level of power being demanded by the driver at that particular moment. By having vacuum advance pull in appropriately more timing you can let out of the throttle more and consequently cruise on less fuel.
For you circle track racers here is something I want you to think about. If your car’s engine had vacuum advance it would get about 20% more mileage on the yellow flag laps. Just how many times have we seen a lead car run out of fuel with just half a lap to go?
Note that our SOHC4's don't have vacuum advance. Also note that modern bikes
do have vacuum advance. This should net a measurable gain in mileage
and part-throttle performance by itself.
After applying all of these techniques to my '79 Honda CB650, it will quite a bit more power (can't put a number to it, though) and I am shooting for ~100 mpg. Call me crazy, but all of these working in tandem should have no trouble gaining >100% MPG from my baseline of 47 mpg.
