High altitude tips for MPFI engine

[Gonzalo Bravo]

What you think is the most effective method to run an aspirated MPFI gas engine at high altitude? let say, over 15.000 feet?

Will a O2 bottle feeding the intake manifold will make a noticeable work? How about NOS?

[Triaged]

You don't want to use O2!
Use NO2 or just a forced induction.

[Gonzalo Bravo]

Originally Posted by Triaged

You don't want to use O2!
Use NO2 or just a forced induction.

Sorry, but what a Forced induction is?

[Scott@Rockstomper]

Originally Posted by Gonzalo Bravo

Sorry, but what a Forced induction is?

Supercharger/turbocharger

Is this for up to and back from 15k feet, or do you actually intend to drive around for extended periods of time at that altitude?

[Triaged]

A supercharger or a turbocharger

[Gonzalo Bravo]

Originally Posted by Scott@Rockstomper

Supercharger/turbocharger

Is this for up to and back from 15k feet, or do you actually intend to drive around for extended periods of time at that altitude?

Ouch, stupid question

Its for up and back, not for long periods. Just for the most steepy areas.

[Gonzalo Bravo]

In this case, where I am trying to put more O2 to engine only, do I need to switch to forged pistons and all that stuff to run NOS or I can keep the engine stock?

[Triaged]

So you are going to try injecting small amounts of NO2 over a long period of time in order to make up for the lost power? You will still need to inject fuel (or trick the computer into richening up the mixture by using a potentiometer instead of a coolant temp sensor) to make up for the computer leaning it out because of the thinner air.

[Scott@Rockstomper]

How much more power do you want available at these high altitudes?

Honestly, unless you're trying to compete at such altitude, I would recommend against doing anything at all, just leave it alone and allow it to run in closed-loop (oxygen sensor functioning) mode and adjust mixture appropriately.

If you are competing at such altitude, a smallish supercharger, while possibly the most expensive option, will probably net you the best possible performance gains.

Feeding O2/N2O into the intake at lower engine RPM's isn't likely to have much result, as there probably won't be enough air velocity through the intake to assure that it goes straight in, as opposed to dissipating in the intake and out the filter. And like Triaged notes, you'd have to fool the computer into injecting more fuel, unless you do this slowly enough for the closed-loop system to deal with--in which case, you're back down to the lower-RPM-range levels where it's not likely to matter anyway.

[Gonzalo Bravo]

I need to climb very high, and the last 500 feet are steepy and with loose terrain, so I need to reach certain speed. Most probably needs to try to keep the engines over 5.000rpms if feasible (red zone at 6.200rpms).
So bassically will need extra help on the last meters and keep the engine at high revs.

Is it still a bad idea to run nitrous?

Engine is a 1.600cc MPFI

[MrWillys]

The oxygen level in the atmosphere is fairly constant at 20.8%. What changes is the pressure that's available when you climb in altitude. Fuel injection systems take a reading to determine the air pressure on startup. if you were to turn off the motor at various points during the climb you would allow the computer to readjust to the newly gained elevation upon restart. The power loss is due to loss of pressure. I don't see how this can be overcome using N2O? As has been mentioned you could force induce pressure which would help. Otherwise, try the restart method and see if it makes a difference.
On second thought here: N2O is an oxidizer, therefore could be introduced in small amount to replace the lost pressure. You mentioned concern about needing forged pistons? I would think you could get away with using small amount as a replecement for lost pressure without the excessive heat build up known to occur when using it for racing. Start with a small shot for your application and turn the pressure way down.
Someone else here mentioned the use of a POT to control the TPS. This I don't understand. I would think you might possibly need to fool the MAP sensor, but I would try it first. My guess is this won't be needed.

[Gonzalo Bravo]

Originally Posted by MrWillys

The oxygen level in the atmosphere is fairly constant at 20.8%. What changes is the pressure that's available when you climb in altitude. Fuel injection systems take a reading to determine the air pressure on startup. if you were to turn off the motor at various points during the climb you would allow the computer to readjust to the newly gained elevation upon restart. The power loss is due to loss of pressure. I don't see how this can be overcome using N2O? As has been mentioned you could force induce pressure which would help. Otherwise, try the restart method and see if it makes a difference.
On second thought here: N2O is an oxidizer, therefore could be introduced in small amount to replace the lost pressure. You mentioned concern about needing forged pistons? I would think you could get away with using small amount as a replecement for lost pressure without the excessive heat build up known to occur when using it for racing. Start with a small shot for your application and turn the pressure way down.
Someone else here mentioned the use of a POT to control the TPS. This I don't understand. I would think you might possibly need to fool the MAP sensor, but I would try it first. My guess is this won't be needed.

and if you Force the air do you need to inject more fuel like at sea level or you only needs to put more air to compensate the lower pressure at same fuel amount?

[Triaged]

What type of fuel injection? Does it use a MAF or MAP sensor (or both)?

Just about all fuel injection systems use the coolant temp sensor to function like a choke would on a carbed engine. If you fool the engine into thinking it is very cold it will inject more fuel. Retards post these on ebay all the time as a "chip" that will get you 15hp and sell them for like $30.

If you really want to do just a bit of NO2 do some searching on google for things like "Nitrous PWM" or "Nitrous Progressive". PWM stands for pulse width modulation. It will make your nitrous selenoide more like a fuel injector and you will be able to limit the flow. Combine this with a pot. for the coolant temp sensor and you might be able to get the power you need.

[Tim84K10]

Originally Posted by Triaged

So you are going to try injecting small amounts of NO2 over a long period of time in order to make up for the lost power? You will still need to inject fuel (or trick the computer into richening up the mixture by using a potentiometer instead of a coolant temp sensor) to make up for the computer leaning it out because of the thinner air.

I'm not sure what kind of EFI he's running, but an O2 sensor is designed for this exact purpose.

The mixture will get RICHER in thinner air, not leaner. Injector pulse width will stay the same but you have thinner (less) air. Less air + same amount of fuel = richer mixture.

I'd say you're just going to lose power at 15,000 feet, but your computer will compensate for it. You'll have way more power with EFI at that altitude than you would with a carburator.

I would not use a pot with the CTS at all. That'd be an uncontrollable way to enrichen the mixture. At WOT, the mixture is programmed to stay pretty rich anyway.

[MrWillys]

Originally Posted by Gonzalo Bravo

and if you Force the air do you need to inject more fuel like at sea level or you only needs to put more air to compensate the lower pressure at same fuel amount?

If by saying "forcing air" we're still talking about using a small amount of N2O. It would be my opinion that the learn function of the computer reading the O2 would increase fuel to compensate for a slight increase in available oxygen.

[MrWillys]

Tim,
This is not really true. I made it a point to take my scanner with me at 10,000 feet. I noted a great decrease in barometric pressure and a slight decrease in injector pulse width. However, the basis of your statement is somewhat correct. At 15,000 the pressure is close to half of that of sea level. I believe half is about 18,000. I can say that at 10,000 my 350 hp small block has a great loss of power. I can see why he would be concerned at 15,000....

Originally Posted by Tim84K10

I'm not sure what kind of EFI he's running, but an O2 sensor is designed for this exact purpose.

The mixture will get RICHER in thinner air, not leaner. Injector pulse width will stay the same but you have thinner (less) air. Less air + same amount of fuel = richer mixture.

I'd say you're just going to lose power at 15,000 feet, but your computer will compensate for it. You'll have way more power with EFI at that altitude than you would with a carburator.

I would not use a pot with the CTS at all. That'd be an uncontrollable way to enrichen the mixture. At WOT, the mixture is programmed to stay pretty rich anyway.

[MrWillys]

I have seen people selling resistors to fool the intake air temp, but not the coolant? Some sell coolant bypass kits to avoid running coolant through the throttlebody as designed for TPI, and LT1's.
Fooling the coolant sensor would perform a similar function, but may not allow the converter to lockup. GM computers must see 122f before the converter locks, and 113f before it will go closed loop. Also, at this temp it only adds 1.1% fuel. Of course these settings are for TPI and may vary slightly depending on application.

Originally Posted by Triaged

What type of fuel injection? Does it use a MAF or MAP sensor (or both)?

Just about all fuel injection systems use the coolant temp sensor to function like a choke would on a carbed engine. If you fool the engine into thinking it is very cold it will inject more fuel. Retards post these on ebay all the time as a "chip" that will get you 15hp and sell them for like $30.

If you really want to do just a bit of NO2 do some searching on google for things like "Nitrous PWM" or "Nitrous Progressive". PWM stands for pulse width modulation. It will make your nitrous selenoide more like a fuel injector and you will be able to limit the flow. Combine this with a pot. for the coolant temp sensor and you might be able to get the power you need.

[Tim84K10]

Do you have a wideband? I'd be interested to see some high-altitude data logging if you do.

Would make for an interesting project.

[Gonzalo Bravo]

Originally Posted by Triaged

What type of fuel injection? Does it use a MAF or MAP sensor (or both)?

Just about all fuel injection systems use the coolant temp sensor to function like a choke would on a carbed engine. If you fool the engine into thinking it is very cold it will inject more fuel. Retards post these on ebay all the time as a "chip" that will get you 15hp and sell them for like $30.

If you really want to do just a bit of NO2 do some searching on google for things like "Nitrous PWM" or "Nitrous Progressive". PWM stands for pulse width modulation. It will make your nitrous selenoide more like a fuel injector and you will be able to limit the flow. Combine this with a pot. for the coolant temp sensor and you might be able to get the power you need.

it use a MAP.-

[Beat95YJ]

Originally Posted by Triaged

Just about all fuel injection systems use the coolant temp sensor to function like a choke would on a carbed engine. If you fool the engine into thinking it is very cold it will inject more fuel.

Generally speaking this is only done on dry systems on vehicles with returnless fuel systems. The majority of dry systems I have used increase the fuel pressure and let the injectors do the rest.

Or run a wet system.

[deepmud]

Reading carefully, it sounds like you need a burst of power at wide open throttle at high rpm, at very high altitude.

Sounds like it's perfect for a shot of Nitrous Oxide. Nitrous was first used on fighter planes for this exact thing.

[SOUTH SHORE 4X4]

Exactly, any of you wheelers ride sleds? Sounds like a Hillclimb-crazy zuk. Stuff a 60 shot kit in her and dont hit the on switch until you're in second gear wide open. The kits come with a gas-pedal sw. also so it will not allow Nitrous to flow until wide open throttle. This would be the simplest answer otherwise a spendy supercharger is perfect. if it was a clutched model with an on switch that would be ideal.

[Gonzalo Bravo]

Originally Posted by SOUTH SHORE 4X4

Exactly, any of you wheelers ride sleds? Sounds like a Hillclimb-crazy zuk. Stuff a 60 shot kit in her and dont hit the on switch until you're in second gear wide open. The kits come with a gas-pedal sw. also so it will not allow Nitrous to flow until wide open throttle. This would be the simplest answer otherwise a spendy supercharger is perfect. if it was a clutched model with an on switch that would be ideal.

Can you guide me about such kit? thanks

[Gonzalo Bravo]

Originally Posted by Triaged

So you are going to try injecting small amounts of NO2 over a long period of time in order to make up for the lost power? You will still need to inject fuel (or trick the computer into richening up the mixture by using a potentiometer instead of a coolant temp sensor) to make up for the computer leaning it out because of the thinner air.

How can you do so?

[Triaged]

I have no idea what the specs are for your temp sensor but this is for a GM (delphi) one.

www.pe-ltd.com/Downloads/coolant_temp.pdf

so about...
10Kohm = 0 deg C (ice water)
3.5Kohm = 20 deg C (about room temp)
180ohm = 100 deg C (boiling water at sea level)

You would have to get something like a 50Kohm pot. (or even a 10Kohm should work). Get an "audio" one because they are non-linear (logarithmic) just like the curve of the sensor. If you wire it in-line with the coolant temp sensor anything other than 0 ohms will make the computer think the engine is cooler than it is. This could make it think it needs to turn on the "choke" giving the engine more fuel...exactly how much fuel is up to you to find out...

Pull your sensor out and figure out the values of your sensor to see if it is the same as the one in my example. Then put the pot (short for potentiometer) in and turn it to some of those values. Drive it and read plugs (or look in the rear view mirror) to see how much richer (if any) it is running.

Note: This will not work at crusing at less than about 75% throttle because the O2 sensor will make the computer compensate to lean it back out. Once in power enrichment mode the computer ignores the O2 sensor.

Have fun!