It's all about the FUEL

[hoodeng]

If you do get into running fuel this may help.
When mixing and looking for a percentage, if you are new to mixing you can get caught when putting straight methanol in to cut the percentage, it is very easy to go under % and very hard to bring it back. What to do is if say aiming for 90% and you are at say 93%, is mix from a churn that is already under at say 87%, or whatever you have drained previously at hand that is under [this stuff does not go off quick like gas or methanol]] and use this to cut your mix, the change in % will be much easier to control.
Fuel percentage is a whole separate area of tune.

Pictured are a couple of old hydrometers that i used many years ago to check new drums of race gas and methanol to use as a gauge later, they were calibrated at 60°f which is 15.5°c, there are scales available to correct back to ambient, any deviance over time meant the fuel was going off

[Dave Koehler]

This may be of use to some of you when measuring a nitro mix with a hydrometer.
I have some pdf charts for nitro percentage vs temperature on this page.
https://www.koehlerinjection.com/tech-articles.html

[ptuomov]

Then let’s do the E85 trick with nitromethane and gasoline.

“Nitropropane is not useful as a race fuel, unlike nitromethane. Nitropropane has the same specific energy as gasoline.“

Per unit of air ingested by the engine? I’m talking about an air limited engine. Nitropropane brings its own oxygen.

Nitropropane has an oxygen content of 36%, very similar to ethanol at 34.7%.
It is not a monopropellant; nitropropane stoich = 5.8, ethanol stoich = 6.4.

Nitromethane is often used with methanol as a co-solvent. A mixture of 20% nitromethane in methanol will increase power by approx 20%. The power output will increase in proportion to the percentage of nitromethane that is used.

Nitropropane is sometimes used in place of methanol as a co-solvent for nitromethane; while no improvement in power results, the knock limit is somewhat raised, allowing a higher compression ratio to be used.

[ptuomov]

How much acetone does one have to mix in with E85 and nitromethane to keep it all mixed in well including that 15% of gasoline in E85?

Also, I wonder what nitromethane + acetone + ethanol + gasoline does to the turbine when the engine is run rich, anyone know?

[nitro2]

How much acetone does one have to mix in with E85 and nitromethane to keep it all mixed in well including that 15% of gasoline in E85?

Also, I wonder what nitromethane + acetone + ethanol + gasoline does to the turbine when the engine is run rich, anyone know?

A fair bit.

That concoction results in an expensive fuel that sounds a little snappier and makes a bit more power. Interesting at first (if you have an engine that already makes a lot of power) but the novelty wears off really fast. Soon you will curse the gasoline and get rid of it. Then you will run alcohol and some modest amount of nitro which assuming is done right and causes no engine damage, that novelty will also wear off quickly.

The thirst for power continues and there is the ONGOING desire to add more nitro %, some will chicken out, some will add more % until they blow something up (ending their desire to experiment with nitro), and some (very few) will successfully make quite a lot of extra power, but of course nothing like what a Top Fuel car makes.

When people say the word "nitro" most people equate that with a Top Fuel car or bike, but those applications are just very extreme ways to use nitro. Nitro can be used in much saner ways than that, for go fast enjoyment purposes.

How much extra power would an average enthusiast, or a drag racer (racing a division not bound up by rules) be happy with via nitro ? Many would appreciate a 25% increase in power, most would be ecstatic with a 50% increase in power, and a few would need 100% increase in power to be satisfied. All easily attainable.

Nobody wants an engine that self destructs, and therein lies the trick to it.

[ptuomov]

In practice, what are peak power numbers for in a modern street turbo car? Bragging rights, mostly. So the practical (ok, stretching the meaning of the word here) application here would be an additional fuel component that could be run with minimal modifications but that would nevertheless give 10-20% more power. This was the motivation for normally running E85 and “on special occasions” blending in nitromethane, acetone, and high octane gasoline. I don’t know if it would work, certainly haven’t tried.

[hoodeng]

I think the idea of just running a percentage of nitro in a general use engine is not taking a few of the maintenance factors of nitro into account.

You are aware that if you use nitro the engine needs to be blown down before it is run? The oil needs to be changed after use as it becomes highly contaminated with fuel. The fuel system is drained after use and stored in appropriate containers and location. The fuel when used will need its SG checked to ensure it is still in the range being used. The fuel system needs to be checked thoroughly before use.
It is not a fuel to be trifled with, It looks simple till this stuff bites you on the ass.

Cheers.

[nitro2]

I think the idea of just running a percentage of nitro in a general use engine is not taking a few of the maintenance factors of nitro into account.

You are aware that if you use nitro the engine needs to be blown down before it is run? The oil needs to be changed after use as it becomes highly contaminated with fuel. The fuel system is drained after use and stored in appropriate containers and location. The fuel when used will need its SG checked to ensure it is still in the range being used. The fuel system needs to be checked thoroughly before use.
It is not a fuel to be trifled with, It looks simple till this stuff bites you on the ass.

Cheers.

Low percentages of nitro doesn't require high maintenance, other than keeping an eye on the fuel system and not letting it sit in the fuel system indefinitely. 20% nitro on an NA EFI (E85 + additive) application is orders of magnitude less nitro volume/mass than what a Top Fuel engine sees. Mostly apples and oranges.

However, if one is running low percentages of nitro on a carbureted engine, then it becomes a different story, more care is required to prevent unexpected surprises, and even then surprises can sometimes happen, even at low percentages.

[RDY4WAR]

I think the idea of just running a percentage of nitro in a general use engine is not taking a few of the maintenance factors of nitro into account.

You are aware that if you use nitro the engine needs to be blown down before it is run? The oil needs to be changed after use as it becomes highly contaminated with fuel. The fuel system is drained after use and stored in appropriate containers and location. The fuel when used will need its SG checked to ensure it is still in the range being used. The fuel system needs to be checked thoroughly before use.
It is not a fuel to be trifled with, It looks simple till this stuff bites you on the ass.

Cheers.

Low percentages of nitro doesn't require high maintenance, other than keeping an eye on the fuel system and not letting it sit in the fuel system indefinitely. 20% nitro on an NA EFI (E85 + additive) application is orders of magnitude less nitro volume/mass than what a Top Fuel engine sees. Mostly apples and oranges.

However, if one is running low percentages of nitro on a carbureted engine, then it becomes a different story, more care is required to prevent unexpected surprises, and even then surprises can sometimes happen, even at low percentages.

Could the same work with non-ethanol pump gas? Say 80% gasoline, 10% methanol (as binder), and 10% nitromethane using a 3 gallon, front mounted fuel cell. Dump it and put in straight pump gas for when it sits between races. I'm not sure where to get straight nitromethane or 90% nitromethane. I'm basing this off blending in VP Nitro 50-50.

That combination should have a stoich AFR around 12.5:1 and 1357 btu/lb of air which is ~6.5% more than pump gas alone.

[hoodeng]

Would those lower percentages negate the necessity to blow down? and under what percentage does this routine become unnecessary?

[nitro2]

Would those lower percentages negate the necessity to blow down? and under what percentage does this routine become unnecessary?

Low percentages results in just a small amount of FUEL volume/mass compared to high percentages, 1) because the percentage is low and 2) because the AFR is much higher. 20% is not just 5 times less than 100% (actually 99%), it is more like 50 times less FUEL than the same engine would run on straight nitro because the % is 5 times less and the AFR is 10 times greater, thereabouts, going with a straight nitro AFR of 0.5 to 0.75.

If you were to run 20% through an EFI there should be no reason to blow down before restarting as the EFI should be shutting off the fuel when the ignition is shut off so the crankshaft spins X number of times with no fuel going in before it comes to a stop, and really there should be next to nothing unburnt in there anyway at idle with EFI.

A carb is a different story. Fuel gets left in the cylinder when the engine shuts off, nitro will hang out in there. Also under the right situation during start up the engine can "take off". If you don't blow down before start up then it is best to squirt some gas down the carb before start up to make sure it squashes any possibility of a significant nitro start. Actually best to do that anyways.

[In-Tech]

Great fun discussion, one thing I don't see here is ignition. We all remember the Super Mag 3, then when Brian decided to take an electronics class at the local college after work, we got the super mag 4, then 5 and nitro classes got very very fast. Now with the new MSD mags I don't think the ignition is the limiter any more and spark plug wires get thrown away every pass since they have suppression for the electronics.

[hoodeng]

Ignition with nitro is it's own story, bear in mind i have only used nitro in a class specific with over 90%, not in the manner described above.
The ignition routine used in drag racing fuel is that you would be starting with an engine that was clear so before cranking over to start the ignition circuit would be activated, you would fire the engine on methanol or petrol either from a squirt bottle or dedicated manifold injector, after the engine is fired on start up fuel and all cylinders firing you would switch on the nitro valve/tap and then the engine would come on line on nitro, once the engine had settled into idle you would remove the auxiliary fuel supply. You need to get heat into the engine for nitro to burn efficiently,,there are a number of routines used after starting and doing a pass,, all routines are the ones that you have found work best for your set of wheels..We found big burnouts hazed ground straps even before the bike made a pass.

Not sure what nitro2's take would be on when shutting an engine down in the circumstances being discussed here but the big big rule with what we were doing is always shut the ignition off before the engine stops rotating, do not turn if off after the engine has been stopped as some ignitions make a spark when the ignition switch is turned off. Any spark in a cylinder with residual fuel can give pretty spectacular results, you would also pull all leads at the end of a pass.
Ignition timing will be whatever makes the best power without burning up the engine. Spark advance in fuel bikes is varied throughout the pass as a form of traction control, you would look at your pass data and if the traction line was spiking or breaking traction and going up in smoke you could pull a couple of degrees at that point of the track then put timing back in where the traction line said you could not exceeding the engines max.
There will be various opinions on what i have said as routines in teams can vary.

If nothing else, if you are looking to go down the nitro route, do spend time with someone who is running it and get them to explain what they are doing and why, some things seem inconsequential only to find it will either save your ass or the vehicles.

Cheers.

[hoodeng]

I should have also included in the previous post, that spark energy is the key to lighting the fire. I have no experience with Supermag's but understand their function, they make a lot higher primary current through a transformer than a traditional 12v supply to a coil, so making a lot more powerful spark at the plug, the traditional Kettering VR/VA is not used here, the higher the primary current the more joules will be provided at the plug regardless of load. The higher the amount of Joules the system generates the more fuel you can light, hence the ignition systems seen on fuel racers regardless of class.

A misfire with fuel can lead to $$$$, source an ignition compatible with your requirements, and as nitro2 pointed out you will get bored fast with low percentages and the quest to run more is inherent with the fuel, so buy an ignition that has the capacity to accommodate beyond your intentions. This is an area not to get economic in.

If only one thing, never hold a plug lead if the ignition is activated, i have seen the dance!

[In-Tech]

Yes, you are correct. The joules are an important factor but can be had in many different variants so spark duration is very important with slow igniting nitro. Hence the need for increased ignition timing so the kernel has time to expand and peak cylinder pressure is still ~15-18 degrees atdc. One time in the mag room at Mallory while "burning in" a Super Mag 5 at over 5" of spark travel, the delivery lady from the warehouse came in and said, oh that's cool and pointed at it and hit her from 3 feet away and knocked her right the fack out, ambulance carried her off