DTN

Seriously, someone has fallen into the marketing scheme. The guy who makes signh grooves is trying to sell signh grooves to people. You may slightly decrease compression and slightly increase cylinder size. You may increase atomization. You may more thoroughly burn fuel which may add a couple of HP to a stock design. However, it's not a magic cure all for the engine that will make a poor design run perfect. It's not going to make up for engine imbalance. It's not going to net a ton of gas millage. It is not the next gift from god which will revolutionize the car industry. This is simply the icing on the cake modification when you have your engine machined back to manufacturer's specs.

You will still need the same octane gas or higher because the fuel burns more readily. More so then ever. Why? The fuel is more thoroughly atomized. This is a simple scientific fact. When the fuel is more atomized, it increases the flame front speed and burns more readily. Now if you were decreasing the flame front speed, then maybe. However, fuel atomization is the whole principal behind Signh groves.

Octane resists detonation at higher temperatures. You're not going to obtain the same results from any sort of groove. There is no such thing as mechanical octane. Why? Compression flashpoint does not change. You may have lowered your compression slightly because you removed part of the head, but not enough to make a difference in the compression ratio. Compression adds heat, directly.

Compression is the principal of operation behind your air conditioner. When you compress anything, the temperature raises. When you decompress anything, the temperature lowers. An A/C unit compresses the freon, runs it through a radiator to remove lots of heat due to the dramatic difference in the radiator vs ambient temperature, then decompresses it, runs it through another radiator which takes the heat out of the air and blows the lower temperature air on you.

Whenever you compress fuel and air, the temperature will raise up. This makes every bit of fuel and air in your cylinder like a powder keg ready to explode. A single predetonation is not that big of a deal because the engine was designed to compensate for detonation or ping using it's ping sensor. It retards the timing and goes on it's merry way.

When you run nitrous oxide, the fuel air ratio stays the same as when you run 21% ambient air. However, the oxygen concentration is raised to as high as 33%. Still running 14.7 to 1 fuel ratio means you are able to burn alot more fuel and generate alot more power. This makes for a very powerful predetonation if one occours and can destroy the pistons. So if anyone recommends that you attempt to run Nitrous Oxide without the proper grade fuel, you should kick them in the balls promptly for telling you to destroy your engine.

Albuquerquefx

Hey, you won't get much argument from me. If nothing else, it's always nice to have someone give it a whirl to see if it works. Most of the success stories I see are around 2-valve heads; I'm not sure what the relationship is honestly. Either way, what the hell, right? smile.gif


I can't really say, honestly. This is one of those cases were "it depends" is the best answer I could give. The head gasket is, I believe, somewhere around .010-.015" give or take. The unfortunate part is that we have no solid data on expected rod stretch and piston expansion at full operating speed / temps for the stock parts, nor do we (so far as I know) have conclusive data about how much clearance the stock head gasket provides under full compression.

Conversely, the manufacturers for aftermarket rods and pistons (and even had gaskets) can indeed give you those sorts of details (or at least good guidelines to follow.) I suppose, if we say the stocker head gasket is at least 0.005" at full compression, then I would think any combination of stock piston and rod and crank combo should probably have enough clearance.

Here's another, potentially far more risky problem that not everyone thinks of: I generally trust the machine shop to do what I pay them, but did they do it right? In order to properly zero-deck a block, they need to know the exact measurement from crank centerline to piston face at TDC -- with the bearings installed, with the pin inserted, blah blah blah. If they screw up any one of those measurements (even by a few thousandths), then you have the potential to do some uber damage to your poor head.

Or maybe the opposite -- maybe they didn't get it right, and now you've got 0.035" worth of clearance when you wanted 0.010". The best way to find out is to pinch off the tiny segment of clay and roll the assembly around on EACH cylinder to ensure they got it right. And if they didn't? Well, hope the didn't take enough off wink1.gif And if they did? Then tada, you know that you have at least one less problem to worry about. Same goes for any other change they've made, such as turning your crank, milling the head, seating valves, boring cylinders, et al. It's always worth it to double-check their work, because otherwise you're only guessing as to what's underneath.


Now, onto the uglier stuff: sad.gif


I think we need to rehash what octane does. Higher octane does not burn "more readily". In fact, it actually burns more slowly, which is why it is more resistant to predetonation. Further, higher octane does not equate to better atomization in any way, shape or form -- it is simply a longer hydrocarbon chain that is slightly less volatile than it's lower-octane cousin.


Yes and no. In a "perfect world" where fuel atomization is at it's absolute best, there's no such thing as mechanical octane. But we don't live there, and perfectly atomized fuel and air isn't a reality in our engines. "Mechanical octane" is a general term given to any physical device that allows the fuel and air to more uniformly mix, thus reducing the lean and rich "regions" in an otherwise stratified mixture. In this scenario, quench area is a form of mechanical octane, as the piston's sudden rush to within ten thousandths of an inch of the cylinder head at almost 11 meters/sec is more than enough turbulence to force quite a bit more of that fuel into fine droplets.

A lean mixture will indeed burn faster, even if it's a localized lean region in an otherwise rich environment. Lean "pockets" can very much cause predetonation, and since we're not in a perfect world, proven mechanical octane methods such as quench area can indeed help us even out the mixture. Singh groves on the other hand have some fallbacks that I'm not entirely certain about...


This sentence didn't make much sense to me. 14.7:1 air to fuel ratio means you're combusting not-quite 15 parts of air for every part of fuel, as measured by volume. If you want to burn more fuel, you'll want to run a more rich A/FR ratio, such as 12:1, or 11:1, or the like. Burning more fuel does not specifically result in more power, and in fact, after a certain logical point will reduce power. Nobody makes maximum power at 14.7:1 air/fuel ratio, most normally aspirated motors seem to make their best power around 13 - 13.5:1 or thereabouts. I'm still not quite sure why this was brought up though, as air/fuel ratio isn't really what we're on about in this thread. At least, not as far as I've seen...

I'm not really sure what you mean here either. Given a multitude of options, fuel octane rating isn't specific to a certain amount of nitrous. Now, the higher potential cylinder pressures provided by using nitrous might need some timing adjustments, of which you could avoid or minimize by using higher octane fuel, or you could minimize by cam timing, compression changes, or even some measure of 'mechanical octane' if you don't have absolutely perfect fuel atomization from the factory (most don't.)

As for a 75 shot? Yeah, if you did absolutely nothing else to the engine, higher octane is a pretty solid idea for a ~55% performance increase. A DIS2 unit certainly isn't a requirement though, nor would Singh's grooves. But hey, if these grooves are such a wonderful antidetonant and actually work, then they could certainly help.

DTN

You did not read what I wrote. You said the exact same thing that I said.


thank you. I didn't know that better atomization was called mechanical octane.

Because nitrous was brought up. Wet shots of nitrous deals with changing the amount of oxygen in the cylinder. You should be able to see why it was brought up, or you're nit picking. I pretty much laid it out in order.

Nitrous burns hotter, therefore the internal chamber temperature is higher after use. Higher temperatures = more detonation. Higher octane = less detonation.


I put as much faith into these grooves as I do a e-bay power chip. They may work in some circumstances. They probly won't hurt. But they're not going to do much spectacular.

If you're going to take apart your engine, may as well put these grooves into them. Apparently, they can't hurt. Without airflow calculations I can't see them doing much of anything.

Albuquerquefx

More uniform fuel atomization does two things: more cooling effect to the cylinder temperatures, as more surface area of the fuel droplets are exposed to the air, and a more uniform mixture (less "lean" and "rich" layers, aka less mixture "stratification".) The former is an obvious example of how it results in less detonation, the latter also means less "lean layers" that can predetonate due to hotspots or spontaneous combustion. The result of better fuel atomization will always be less tendency to detonate, which is where the term 'mechanical octane' came into being.


You really didn't mention it in your thread; I suppose I see where you're going now.


Not exactly. Nitrous doesn't burn at all, you can open a nitrous bottle straight into a fire pit, and if it's a full bottle, you'd have a solid chance of putting the fire completely out. However, under high compression and heat, the N2O molecule will crack and separate the oxygen from the nitrogen. As for thermal differences, they're only related to compression changes at best -- otherwise, your combustion temps (and EGT's) should be no different than the car would otherwise register at full throttle. If your combustion temperatures spike during nitrous use, it's not a good sign...


I disagree. First, they will not affect airflow in any measurable way; this is solely a combustion chamber adjustment. The engine's total volumetric flow will not be altered by adjusting combustion chamber volume. Second, you could very certainly do some harm to your motor by doing these grooves in the wrong way. In fact, we'd have to know what the right way is before we could even denote what the wrong way might be.

In my educated opinion, there will be far more wrong ways to put these grooves into your cylinder head than right ways. Sharp edges, cutting the grooves too near the cylinder walls, the uniformity, depth and shape of the groves -- all of these things can adversely affect your combustion efficiency, and all of them could do it in a very negative way. Unless I had a way to empirically test the changes I was making, I'd be very leery of making these changes to my motor.

But that shouldn't stop anyone else from giving it a shot smile.gif I simply don't have the willingness to try something new this "late" in the game for my setup. My only suggestion for those trying it is this: be cautious.

DTN

Nitrous oxide works, like you said, by separating the nitrogen from the oxygen. More oxygen and more fuel in the space = hotter burn. More energy in the same area. The exhaust will be a bit of a higher temp, but the head gets much hotter. There's also more pressure in the cylinder causing higher temperatures.


The idea of the signh grooves is to cause turbulence by moving certain areas of the air quicker then others. This swirls the air around similiar to a small quench area causing more turbulence during the compression stroke. Also, on the site, they demonstrate signh grooves around the valves on a few of their pictures.


Also, this is the first time I've heard anyone whom I know, knows something about engines say anything about being leery of signh grooves. I kinda figured that they had been tested to the point of being safe, but the gains were unknown.

Albuquerquefx

Combustion temperatures will not change; the only way it will get hotter is if it's running too lean. Otherwise, going by your logic, the stock ~1600*F EGT's from a 140hp car would turn into multiple thousands of degrees if we doubled or tripled the horsepower. This is simply false; gasoline engines at stoichiometric fuel mixtures will top out something just shy of 2000* fahrenheit. It doesn't matter if you're normally aspirated, boosted, or feeding it nitrous. It also doesn't matter if you're making 100HP or 1,000HP. If you get hotter than that, you're not making the most efficient use of the fuel.


Nope. They're still quite the extravagant hype box, and if it were as easy as simply taking a dremmel to your cylinder head with no other care for measurement or uniformity, then I think we'd see at least ONE OEM use it in a production vehicle of some sort -- don't you?

No, it's not proven, and dremmeling (or die-grinding, or angle-grinding, or filing) notches into your cylinder head is not safe either. If you don't know what you're doing, you could do far more harm than good.

Albuquerquefx

I don't think I told you anything about how to operate your own life, car, or thread.

Howabout this: I'm here to share with you the logical reasons why this may not be a good idea. I haven't bashed you in any single portion of my reply; it is your car to do with what you want, and I will not stop you. Nevertheless, I also feel obligated to state the obvious for those people who are reading your thread who otherwise wouldn't know the difference.

It's entirely possible that Singh was on to something (or on something! Ha! laugh.gif ) There is at least the distinct possibility that he discovered a way to use a "groove" of some sort to do what he is describing. But let's think about it more: he's patented is approach, and is selling it. By this logic, it isn't something that you can simply recreate with a dremmel and a bit of crunching on a head. It's like how porting the intake side of a head is quite a bit more than simply "making it bigger inside."

There is some level of science that you are quite obviously ignoring. Use common sense if nothing else - a trench with uniform depth means that air and fuel at the "outside" will not be equally forced into the "inside"; it will simply stagnate at the corner. A trench of uniform width simply exacerbates the same problem. A trench with non-uniform texture could result in inequal fuel distribution during compression. Think about these things, and you'll start to understand why your chosen methods may completely invalidate the science that Singh has developed.

I'm not saying it doesn't work, I'm warning you that your implementation is akin to taking that same dremmel to the intake ports on your head. Drilling for sake of doing something does not automatically get you a positive result, just like "bigger" intake ports are quite often NOT better.

DTN

Which one of these flames is hotter? a match stick, or a bonfire?

Ok, now across the same area at the same pressure with the same oxygen concentration, both flames will burn at the same temperature. So, they're the same temperature right?

Ok, so you take that same bonfire and compress it down to the size of the matchstick (physically possible?) and then set them both on fire.. Which one is hotter?

When you increase the amount of fuel which is combusted in the engine at the proper air/fuel ratio, you have more energy released in the same area. This is the reason nitrous oxide works. Same with super/turbo. When you release more energy, more heat is generated. Once it decompresses into the exhaust system and takes up relatively massive amounts of space, it will not retain that high temperature. The temperature lowers in the exhaust because it is no longer under pressure and can expand out distributing the same energy across a larger area.

I'm not saying it's a 1,000F difference in temperature, but there is a reason that nitrous "fries" piston rings if you use it for too long, in improper mixture, or in too high of a concentration. The exhaust does not see as dramatic of a temperature increase as the cylindar does because it's not under pressure.

Albuquerquefx

Assuming equal fuels, neither is "hotter".


No, it isn't physically possible in the realm of current human capability; you don't "compress heat" just like you don't "compress light". While technically we have some amount of technology that is possible of doing tiny bits of what you describe, you're talking about particle accelerators -- not something you'll have underhood.


While you didn't really articulate it well, what you're saying is generally correct. By increasing the mass of both the fuel and oxidizer in equal proportion and ignite them in an otherwise identical space, the gasseous result will be of higher volume. This means more total expansion in the combustion chamber, which translates to more mechanical energy (downward push on the piston crown.)


You're connecting two concepts that aren't linked. Rings don't fry because of temperatures due to nitrous, they fry because someone didn't get the air fuel ratio correct. They also fracture because of detonation (bad timing, bad gas) and they also can fracture under severe duress of all the extra compression force. Here's a commonly overlooked fact about nitrous: it actually lessens combustion chambers if all else is equal. Why? Because the extreme decompression from the ~1000psi bottle to your ~15psi intake manifold results in a massive temperature drop of the injected nitrous. This massive temperature drop can actually force your combustion chamber temperatures to decrease, which is why you don't always need exactly "75 horsepower" worth of additional fuel with your 75 shot -- keeping it slightly leaner allows the combustion chamber temps to be where you want them. Again, you're still targeting around 1850*F combustion temperatures.


The exhaust gas temperatures will see a direct and proportional temperature increase to the combustion chamber temperatures. The temperature delta depends on exhaust port design in the head, cam profile, valve shape, manifold / collector design, and how far away you have placed your thermocouple. But your exhaust gas temperatures WILL raise in accordance with your combustion chambers. Nitrous doesn't "magically" cool off more than any other exhaust coming out of those chambers, and no amount of you trying to teach me about thermal expansion and contraction is going to hide the fact that exhaust cooling rate isn't going to change in a motor where the only other alteration was nitrous injection.

Again, 1850*F is where the combustion chamber needs to be. If it's getting hotter than that, then you're having fueling issues, or you're using some other compression alteration device such as a turbocharger or supercharger. Combustion temperatures is actually one case where nitrous does NOT behave the same way as other forced induction methods, and it's actually IN YOUR FAVOR.

DTN

You're wrong man. If you take that theoretically impossible scenario I mentioned earlier and relate that to fuel in a chamber, that's the same scenario as Nitrous, turbocharging or supercharging. You're burning and releasing a larger amount of energy and heat in the same area with nitrous then without and that's why you need higher octane.