Water injection

[user-23911]

If you're using EFI, in particular the speed density variant of EFI, it's really not compatible with water injection due to the way it works (Cooling the charge in the manifold increases the density, but the computer has no way of knowing how much by) . It's going to lean out the AFR when it turns on. Adding methanol or ethanol to the mix will tend to richen it back up.
That's yet another big disadvantage of speed density systems and a big plus for MAF based EFI.

If you're starting with a MAF based EFI system and the AFR is correct then adding water and methanol will make it richer, same with a carburettor.

This is a very interesting take on what happens and worth remembering when doing this

Not only that but if you're using a WB o2 sensor, it won't read correctly either, even using WI on a MAF based system.
WI always makes them read incorrectly.
It changes the partial pressures of all the gasses involved.

[volodkovich]

How about running the IAT sensor in an intake runner? Would have to insulate it from the manifold but seems like it would be a good idea.

[Circlotron]

If you're using EFI, in particular the speed density variant of EFI, it's really not compatible with water injection due to the way it works (Cooling the charge in the manifold increases the density, but the computer has no way of knowing how much by) . It's going to lean out the AFR when it turns on.

Shouldn’t matter with a MAF sensor though because the change in air temp and density is all downstream of the sensor. No different to the air being heated by the inlet manifold after it leaves the MAF sensor.

[Truckedup]

The basic idea of octane is that it is harder to burn and therefore the burn is slower but that is not how peak HP is made .... up to the point of an uncontrollable burn a higher speed burn does better and will make a higher peak pressure so it is a fine line between to fast and to slow and this is tuned with timing and fuel .....

What you're saying is not true..In the case of pump gas, higher octanes may or may not burn slower, increasing octane is to prevent spontaneous combustion of end gases not slow down the main charge burn... High octane race fuels all have a fast burn for high rpms's..And the faster the fuel burns, less chance for detonation.And there's more to fuel than octane, evaporation rates and RVP pressure contribute to detonation control....Go to Sunoco race fuel and vP race fuel websites to read about it..
This is a good article on detonation...http://www.contactmagazine.com/Issue54/ ... asics.html

[dwilliams]

Never dreamed it would enter into the combustion process.

The gold standard is Iving Glassman's "Combustion." The book is fairly expensive, but you can get it through Inter-Library Loan.

The book is written for engineers who want to know, not just fuels, but how to burn stuff in general, like the furnaces that dispose of hazardous waste.

Besides the usual hydrocarbon fuels, it covers combustion of metals like iron and aluminum, stuff like boron, ammonia, hydrazine, and hydrogen peroxide, the effects of water (liquid or steam), and how gases like argon can accelerate the combustion process. (catalytic reaction)

What makes Glassman's book useful is that it's basically "how to" process handbook, not chemical engineering. He doesn't assume you're a chemical engineer, just someone reasonably intelligent who is looking for information to solve a problem, said problem involving FIRE, GLORIOUS FIRE, BWA-HA-HAAAA!!!

There's some excellent information on the intarwebz, but it can be hard to sort out from the logical-sounding BS.

[F-BIRD'88]

Its a a passenger car internal combustion engine, not a blast furnace.
Keep it real.

[roc]

The basic idea of octane is that it is harder to burn and therefore the burn is slower but that is not how peak HP is made .... up to the point of an uncontrollable burn a higher speed burn does better and will make a higher peak pressure so it is a fine line between to fast and to slow and this is tuned with timing and fuel .....

What you're saying is not true..In the case of pump gas, higher octanes may or may not burn slower, increasing octane is to prevent spontaneous combustion of end gases not slow down the main charge burn... High octane race fuels all have a fast burn for high rpms's..And the faster the fuel burns, less chance for detonation.And there's more to fuel than octane, evaporation rates and RVP pressure contribute to detonation control....Go to Sunoco race fuel and vP race fuel websites to read about it..
This is a good article on detonation...http://www.contactmagazine.com/Issue54/ ... asics.html

Truckedup is on the money.

[user-23911]

It's a lot to do with the difference between single carbon - carbon bonds and double carbon - carbon bonds.

The single bonds are easily broken compared to the double bonds.
Higher octane fuels tend to have more double bonds, the auto ignition temperature is higher.
In particular the benzene rings(aromatics)........3 single bonds, 3 double bonds.
That's why benzene, toluene and xylene make the best high octane fuels.
The downside is they're carcinogenic.

That's what you learn when you study organic chemistry at university, or it used to be what you learn.

[roc]

It's a lot to do with the difference between single carbon - carbon bonds and double carbon - carbon bonds.

The single bonds are easily broken compared to the double bonds.
Higher octane fuels tend to have more double bonds, the auto ignition temperature is higher.
In particular the benzene rings(aromatics)........3 single bonds, 3 double bonds.
That's why benzene, toluene and xylene make the best high octane fuels.
The downside is they're carcinogenic.

That's what you learn when you study organic chemistry at university, or it used to be what you learn.

Good info Joe, now I know why folks cut nitro with some toluene to calm it down (increase detonation resistance).

[Truckedup]

It's a lot to do with the difference between single carbon - carbon bonds and double carbon - carbon bonds.

The single bonds are easily broken compared to the double bonds.
Higher octane fuels tend to have more double bonds, the auto ignition temperature is higher.
In particular the benzene rings(aromatics)........3 single bonds, 3 double bonds.
That's why benzene, toluene and xylene make the best high octane fuels.
The downside is they're carcinogenic.

That's what you learn when you study organic chemistry at university, or it used to be what you learn.

And what happens when the tetraethyl is added for those of us using leaded fuels..?

[MadBill]

... This is a good article on detonation...http://www.contactmagazine.com/Issue54/ ... asics.html

It's rare to see an article on detonation as error-free as this one!
I have only one little quibble: Although it was long believed to be, the ideal Location of Peak Pressure of combustion, especially at part throttle, is not universally fixed at 14°. A number of years ago, a GM researcher developed a pressure feedback system utilizing a sensor-equipped head bolt, for the purpose of dynamic spark advance control to maintain LPP at 14° ATDC. As the work continued, corrections had to be introduced for various applications and operating conditions. Eventually it was realized that the resulting tables were pretty much as complicated and time-consuming to create as a normal spark table, and the project was dropped.

[user-23911]

And what happens when the tetraethyl is added for those of us using leaded fuels..?

It's the lead atom in the middle with 4 bonds that makes the difference.
All 4 bonds have to break before there's complete combustion. It slows down the reaction.

A bit like burning a diamond.
It's still carbon but it's got lots more bonds holding the carbon atoms together so it's slow to burn and needs lots of heat and pure oxygen.

[Truckedup]

... This is a good article on detonation...http://www.contactmagazine.com/Issue54/ ... asics.html

It's rare to see an article on detonation as error-free as this one!
I have only one little quibble: Although it was long believed to be, the ideal Location of Peak Pressure of combustion, especially at part throttle, is not universally fixed at 14°. A number of years ago, a GM researcher developed a pressure feedback system utilizing a sensor-equipped head bolt, for the purpose of dynamic spark advance control to maintain LPP at 14° ATDC. As the work continued, corrections had to be introduced for various applications and operating conditions. Eventually it was realized that the resulting tables were pretty much as complicated and time-consuming to create as a normal spark table, and the project was dropped.

The author of the article worked at GM as an engineer in that field .... Watch this 6 minute video.. Kevin Cameron has been know to motorcycle tuners for many years and is considered one of the best
https://www.youtube.com/watch?v=aH-lDh3rVFQ

[midnightbluS10]

Don't know if it's been posted but there's a decent thread in Advanced Tech about this. Last page(55).

https://www.speed-talk.com/forum/viewtopic.php?f=15&t=5632

[3pedals]

Not only that but if you're using a WB o2 sensor, it won't read correctly either, even using WI on a MAF based system.
WI always makes them read incorrectly.
It changes the partial pressures of all the gasses involved.

how does water injection make the wideband O2 sensor read incorectly?