THE QUESTION OF FUEL                                                     Printer-friendly format
PART 6 -
Additive Performance Testing

By John Copeland

In earlier segments of this series we've talked about fuel additives used to improve engine performance. We've looked at the basic properties of fuels that may impact how much energy they make available upon combustion and how some additives may increase ( or decrease) that available energy. We've also looked at various means of detecting these additives and how the tech man can spot them in the field. Now it's time to take a hard-numbers look at what sort of advantage the fuel cheater can expect to gain from using these materials.

As you may recall from Part Five, (NKN June 1995), we established a threshold of detectability for each of the nine additives that we have been testing, both on the Digatron meter, and with two different water absorption tests. In order to generate meaningful data for this performance testing portion of the project, we ran fuel samples with more than one concentration of the additive in question. For example, earlier testing showed the threshold of detectability for Propylene Oxide to be about 2% by volume, when mixed with otherwise legal race gas. We then ran dyno testing on that fuel with 2% Propylene Oxide added and compared it back-to-back with the same sample with 10% added, also back-to-back against a legal sample. Hopefully this will address the question of "Oh yeah, Well I heard that Johnny Go-fast put some of that stuff in his gas and it gave him more top end between 18,000 and 19,000 RPM!" Let's find out if adding this stuff really works, and how.

In order to insure uniformity of results, all samples were based on Phillips B32 race gas. Comparison testing on the dyno has shown that this high-quality race gas will produce consistently higher performance than four other race gasolines generally available, and substantially higher performance than any pump gas or combination of pump gases. As with earlier tests in this series all samples were mixed 20:1 with Burris oil, mixing four ounces of Burns Castor and two ounces of Burris Blend per gallon of fuel. All testing was done on Fox Valley Kart's electronic engine dyno with periodic base-line samples re-run to insure repeatable data. Torque readings, from which horsepower is calculated, are accurate to .001 foot-pounds. All data, torque, RPM, cylinder head and exhaust temp, are collected by the computer 10 times each second, then computer averaged around each plotting point. While the absolute horsepower numbers may vary from one dyno to another, what we're interested in here are comparative figures.


Propylene Oxide's primary contribution to the combustion process centers on it's high heat of vaporization. As we discussed in Part Four of this series (NKN June 1995), this high heat of vaporization means that, as it passes from a liquid to a gaseous state in the carburetor, it absorbs a significant amount of heat and, thus, cools the incoming fuel charge significantly, making it denser. While Propylene Oxide brings along some of the oxygen it needs for it's own combustion, it also takes additional oxygen from the carburetor air. It's specific energy is slightly less than that of gasoline, so don't expect any help there. It's combustion products are C02, CO, and water vapor. As you can see from the graph, there is no measurable performance difference between the base-line fuel and the sample containing 2% Propylene Oxide, slightly above the threshold of detectability with the Digatron meter. However, by increasing the concentration to 10% by volume, well above what even the most bumbling tech man should be. able to spot, we begin to see the effect of improving the charge density on the low end. This effect diminishes as RPM increases, probably because this higher air velocity through the carb dramatically improves the atomization of the gasoline and the resulting chilling of the incoming charge.

Conclusion: Yes, using Propylene Oxide may help the low end performance or used in sufficient quantities. But unless there is no fuel tech at all, you can't get away with running enough to get any improvement.


Nitromethane has been the number one fuel in the drag race's bag forever. When it comes to delivering maximum bang in the combustion chamber, Nitromethane is the ticket. But that big bang only comes with massive quantities of Nitromethane. Drag racers have the luxury of passing almost unlimited amounts of whatever fuel they choose through the induction system. Karters do not. To burn efficiently and liberate more energy than regular gasoline, you'll need on the order of 10 times more fuel if you use Nitromethane! Not a likely scenario given karter's garbs and their pumping capabilities. Anyway, in our first graph we see the effects of using 2% Nitromethane by volume verses un-doctored race gasoline. Last time we showed that Nitromethane was detectable on the Digatron meter at concentrations of less than 1%, but we chose to use 2% here to assure an adequate response. You can note that there is a very minor enhancement on the low end of the curve, and this may again be due to improved heat of vaporization as with the Propylene Oxide. But, as before, the output is absolutely identical at RPMs over 11,700. In the second graph, with 10% Nitromethane, we begin to see some measurable results from this additive. The low end increase is still there, indicating some higher energy output as well as the cooling effect. At higher RPMs the considerably higher specific energy of Nitromethane begins to show. Higher concentrations would undoubtedly generate even higher performance. But, because this material is so easily detectable, we do not see the need. One rather less attractive feature of Nitromethane that appeared, even in the 10% concentration, is it's substantially higher heat output. During the relatively short duration of our dyno run, we saw cylinder head temperatures climb dramatically over what we had seen with the gasoline only sample. At the same time we saw exhaust temperatures fall, a combination indicative of detonation. It should be expected that extended running would require a richer mixture to avoid sticking. Such a richer mixture would probably diminish the performance improvements somewhat.

Conclusion: Like Propylene Oxide, it's unlikely that any performance improvement can be achieved using concentrations of Nitromethane that would make it past even the most rudimentary tech inspection.


Nitropropane is, of course, chemically related to Nitromethane. It's more complex chemical bonding structure does not lend itself to the same specific energy potential as Nitromethane, and it is slightly more oxygen hungry. It is generally considered to be about 70% as potent an additive as Nitromethane, when used in sufficient quantities. One advantage over Nitromethane is Nitropropane's higher resistance to detonation. However, it's lower heat of vaporization diminishes the increase in charge density at low RPMs. Nitropropane is even more visible to the Digatron meter than the other additives tested, tripping the meter to +6 at only 2% by volume. Nonetheless, we tested it on the dyno at 2% and 10% to maintain some continuity with our testing procedures. As expected, the 2% Nitropropane sample exhibited no measurable performance improvement over the straight race gas results. Low RPM output actually decreased in the 11,300 RPM to 11,700 RPM range, with no apparent explanation. Likewise, there is a minor improvement between 13,200 RPM and 13,500 RPM. This increase is neither of sufficient magnitude or duration to be of any real value. The next graph, showing the effects of 10% Nitropropane, exhibits the same low RPM depression, only to a greater degree and longer duration, as the 2% sample. While we do not have a firm explanation for this effect, it is consistent with the earlier run. Further up in the RPM range, however, the enhancement effect of using Nitropropane is more apparent. Also, we did not see the same evidence of detonation with this sample as we saw earlier with the 10% Nitromethane.

Conclusion: Nitropropane can be a useful additive in settings where no fuel tech is being used. While less powerful than Nitromethane, it's higher resistance to detonation more than makes up for that deficiency. However, some as yet unexplained low RPM phenomenon actually hurts lower RPM performance, and the effect increases (that is the power DECREASES) as the concentration is increased. But, if the Digatron meter is in use, it'll probably go off when your drive in through the gate with this stuff.


Most commonly used, fuel-wise, as the major component in starting fluid for those cold winter mornings, Ethyl Ether has both a very high heat of vaporization and a very low flash point. Those properties make it the perfect cold weather engine starter but, (thank goodness) we don't race in sub-zero conditions. It's specific energy is lower than gasoline and it's very low boiling point (95 degrees) make it difficult to keep around in mixed fuel for very long: it simply evaporates away! Regardless, some folks have insisted that it was the secret key to better lap times, so let's take a look. In the first graph, again using 2% Ethyl Ether, We could find absolutely NO measurable variance in power output over the same fuel without the Ethyl Ether. Tiny variances in the raw data were too small to show up on the graph at all. By increasing the concentration to 10% the effect of the high heat of vaporization begins to show up on the low end. The cooling effect of the vaporization of the Ethyl Ether treated fuel was greatest at the lowest RPM and steadily decreased. Although it is hard to pick up on the graph, the performance actually dipped below that of the undiluted race gas at the highest RPM range, although very slightly. Once again, Ethyl Ether is very easily detectable with the Digatron meter in concentrations as low as 1%.

Conclusion: Unless you're racing at the South Pole, there really isn't anything to be gained here. Small concentrations don't do anything at all. And even if you wanted to run enough to get the minor low speed charge cooling effect. the smell is a dead give-away. Spend your time and money elsewhere.


We've chosen to lump Toluene and Xylene together for several reasons. If you read the previous article (NKN July 1995), you probably noticed that we poured substantial quantities of Toluene and Xylene into the base fuel samples trying to get the Digatron meter to react. The best we could do was to push it down to ?8, and that with over 50% of each additive! The reason is simple: both Toluene and Xylene are major components of normal gasoline! They're already in there in substantial quantities. Increasing the concentration does nothing but raise the octane rating of the fuel, and, if you've kept up with your reading, you already know that raising the octane, in and of itself, is of no benefit to almost all karting engines. Again, in keeping with our goal of maintaining consistency in our testing routine, we dynoed samples with 2% and 10% of each, both Toluene and Xylene. As expected the 2% graphs show only the most minor variation, with some gain in the low RPM range. This is most likely due to the increased octane rating from adding these materials helping to suppress some high load, low RPM detonation.

Conclusion: This one's a red herring. If you must pour something in your fuel to feel like you're getting some sort of special advantage, add Toluene and/or Xylene. The won't do you any good, but they won't do you any harm either, and you most likely won't get caught. One note of caution: if the tech man is using either of the water tests we outlined earlier in this series, a 10% or greater addition of Toluene or Xylene may show up.


Of the additives we tested, this one has caused the greatest concern amongst the karting public, and with good reason. It is a skin- absorbable poison and a Class-A carcinogen. While it does not show up on the Digatron meter, it is easily detectable with either of the two water absorption tests outlined in Part Four. Again we ran dyno tests at two concentrations. However, because of 1,4 Dioxane's much higher threshold of detectability, we chose to test at 10% and 20% by volume. The results on the two graphs point out what the effects of this material are, both good and bad, as well as it's cumulative effect. It is generally thought that 1,4 Dioxane's benefit lies in it's improved oxygenation of the combustion reaction. That appears to actually reduce power output in lower RPMs by, in effect, leaning out the mixture. In this RPM range the carb settings are often too lean already and this additional leaning may result in failure. However, as RPMs increase and the Walbro carb translates into an over-rich condition, the oxygenation effect begins to pay off. Higher combustion temperatures will likely accompany this change. Comparison between the 10% graph and the 20% graph indicate that the addition of more 1,4 Dioxane increases both the negative low RPM effect and the positive high RPM effect.

Conclusion: This is a tough one. Here we have an additive that actually does something; part good, part bad. But more importantly, this stuff is VERY VERY BAD FOR YOU!! Some of you other old-timers will remember when some folks ran Hydrazine (that's liquid rocket fuel, really) back in the 60s. Like 1,4 Dioxane, it was very dangerous to mess with. The sanctioning bodies made it illegal and threatened lifetime suspensions for anyone caught using it. Now there is considerable pressure coming from several sanctioning bodies and clubs to suspend anyone caught using 1,4 Dioxane for life. I totally support this position. Any competitor who exhibits so little regard for themselves or their fellow competitors as to expose them to this material has no business in karting. Let me repeat, 1,4 Dioxane is VERY DANGEROUS, both to use and to be around. If you see anyone using this material, notify the officials IMMEDIATELY! In liquid form it is highly absorbable through the skin and HIGHLY TOXIC. It is also listed as a LETHAL CARCINOGEN. This is not anything that you want being used around you or your family, it has major health risks!. DON'T STAND FOR IT!

HI REV 3:1

This additive is described as a fuel conditioner and combustion enhancer. Because of it's relatively low delectability with the Digatron meter, fuel tech will be best accomplished with either the water-fuel Digatron test or the 30-30-30 test. Thus far none of these is definitive when looking for Hi Rev 3:1. As we do not currently have any definitive data on the composition of this product, and MSDS data sheets are not available, testing is continuing. Once we have a better handle on what is in there, we'll be able to give you
specific testing protocols to spot it.

Conclusion: Until we know more about what is really in this stuff, and what it's benefits and hazards are, we can't really speculate. We'll also have to get better tech procedures for this additive, and we will. More on this one later.

KLOTZ COXOC (Stealth Additive)

This product is from one of the longtime leaders in the lubricant industry. During discussions with several at Klotz, they repeatedly pointed out that it is not intended for use at sanctioned events, or events where fuel is required to meet standard tech guidelines. Nonetheless, they have promoted it as being an undetectable performance enhancer. We will continue to pursue further information about the specific makeup of this product and how that may be of interest to the karter. Please note; Klotz COXOC is readily detectable both with the fuel/water Digatron test and with the 30-30-30 test. As we learn more about the composition of this product, we will pass on additional tech testing information.

Conclusion: Like the Hi Rev 3:1, our inability to get hard data on the composition of this product was temporarily limiting our ability to reach any conclusions. It is somewhat disturbing to see a product marketed as "undetectable" in tech, regardless of the manufacturer's claim that it is not intended for use in sanctioned events. It is, of course, not undetectable, as we have shown. As we learn more about it's composition we will pass that information along.

So there you have it; real numbers testing. What works and what doesn't. By now it should be pretty obvious that do-it-yourself fuel chemistry is not only dangerous, it's foolish. Unless you're a PhD chemist, or have access to sophisticated testing facilities, the chances are that messing with your fuel will only make you go slower, increase the likelihood of damaging your engine, and get you bounced at tech for your trouble. The people who really know about fuel are the people who do it for a living; the oil companies in their racing divisions, and the professional additive manufacturers. Trying to outsmart them, and the tech man, is a fool's mission. As we've stated earlier, there is almost no likelihood of you producing any kind of fuel concoction that will perform better than high-quality racing gasoline. It's designed to do the job you have to do, it's free from any of the EPA and other government tampering that makes pump gas such an unknown from week to week, and, very importantly, it's going to be the same day after day, week after week, month after month. I know we haven't found the final answer to the fuel question yet. Nor have we pinned down how to tech for every possible additive the fuel cheater might use, but we're working on it. In the weeks and months to come we'll bring you updates on our research.

The goal is, and will continue to be, to keep honest karters honest, to catch and penalize cheaters, and to continue the spirit of safe, fun competition. On a personal note, I think it's very important to recognize that the overwhelming majority of karters play by the rules, fuel-wise and otherwise. I hope this series of articles has not given anyone the impression that fuel cheating is wide-spread. I don't believe that is the case. But what I really can't understand is what satisfaction those few that do beat the rules get from their efforts. A trophy won unfairly can't be much of a source of pride, and how sad to know, in your heart, that it's the only way you could win. Cheaters may try to justify their actions by saying that they're only doing what everyone else is doing, but I know that's a lie, and so do they. What a pity.

Well gang, where do we go from here. I've learned a lot from doing this series, and I'm not through learning yet. As I said, I'll be passing along what I come up with from time to time, but for right now it's time to look forward. Next time, we'll be doing a little crystal-ball gazing; trying to see what's on the horizon, fuel-wise. We'll look at some alternative ways of seeing to it that every competitor on the grid has safe, legal fuel. See ya then.

The Question of Fuel - Part 7

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