flamethrower exhaust

silverado42000 wrote:

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if your wanting flamethrower exhaust its better to just get the propaine system, then you dont hurt your motor at all, just hook the system up at your exhaust tip(s) and press a button when you want to show off(or get that tailgater off your ass)

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As long as you don't max out the duty cycle on your injectors you won't hurt the engine at all.  Fuel injectors have a tendency to stick open if ran at 100% duty cycle.  Anything under 100% duty cycle isn't going to add any extra stress to the injectors, they will just stay open longer each stroke. 

Of course you'll have some unburnt hydrocarbons in your combustion chamber, but that shouldn't be a big deal since I assume you'll only want the car to run rich when you want to activate the flamethrower, and not at all times.  I doubt you'll have any issues at all with damaging the motor (especially if you take the cats out, which in itself is illegal).

Do a search for a voltage divider circuit.  You can make one using a static resistor and an adjustable resistor and be able to manually adjust the output voltage.  You may want a 1VDC voltage regulator feeding the voltage divider, but other then that it should be pretty simple.

What kind of kit did you get?  I've heard of them, but never actually seen one. 

Please read the forum rules concerning information about illegal activities.  Thanks.

Keeping in mind of course that the engine computer uses the O2 sensor data to control the fuel mixture of the engine.. so when messing with the O2 voltage it's causing the computer to richen the mixture (which is what you want I guess) but when you allow the voltage to go back to actual O2 sensor output the computer is going to try to lean back out.. the problem is when the computer hits the far limit of adjustment.. certainly a problem with OBDII cars, but I don't know how much of a problem it would be with an 88 Honda. Regardless, the computer will never allow a 100% PW on the injector.. I'd suggest adding fuel downstream of the cat in the exhaust system.

Jim

Mad Scientists wrote:

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Keeping in mind of course that the engine computer uses the O2 sensor data to control the fuel mixture of the engine.. so when messing with the O2 voltage it's causing the computer to richen the mixture (which is what you want I guess) but when you allow the voltage to go back to actual O2 sensor output the computer is going to try to lean back out.. the problem is when the computer hits the far limit of adjustment.. certainly a problem with OBDII cars, but I don't know how much of a problem it would be with an 88 Honda. Regardless, the computer will never allow a 100% PW on the injector.. I'd suggest adding fuel downstream of the cat in the exhaust system.

Jim

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You would be surprised at how some engine management systems work these days.  Case in point, a brand new Saturn Red Line ('high' performance, supercharged Ion).  Near red line when everything is working perfect they actually max out their stock injectors at 100% duty cycle.  I couldn't believe it when I saw it, but my Fluke 189 doesn't lie.  I would guess that not many OEM ECUs will do this, but I wouldn't use the word 'never'.

I'll retract the 'never', and rephrase to say that 'I would find it hard to believe that a vehicle manufacturer would allow more than the recommended 75-85%'

"The injector duty cycle is the percentage of time that the injectors stay open. The more fuel that is burned the higher the injector duty cycle will be. In general, the duty cycle should never exceed 75-80%. If you start going beyond these figures due to upping the power, then you need to replace your injectors with bigger items.

As a rule of thumb, Bosch injector max is 80%. ND and Rochester injector max is 75% and Lucas injector max is 85%.

If the injectors are opened for longer than, then they will begin to experience flow problems and the closer they get to 100%(continuously open), the more erratic the flow will become and the injectors risk being overheated and burned out."

https://www.ttmtechnical.com/fueldelivery.htm

"An injector in an engine turns on and off very quickly to control the amount of fuel delivered. The amount of time an injector is turned on and delivering fuel is known as the duty cycle. This is measured as a percent, so 50% duty cycle indicates that the injector is held open and held closed for an equal amount of time. When the engine needs more fuel, the time that the injector stays on (its duty cycle) increases so that more fuel can flow into the engine. If an injector stays on all the time, it is said to be static (wide open, or 100% duty cycle). Injectors should not go static in a running engine. If an injector is static in a running engine (open 100% of the time), that injector is no longer able to control fuel delivery. This could be an indication that the injector is too small for the needs of the engine. Injector duty cycle should usually not exceed 80% in a running engine at any time."

https://www.docinjector.com/info.htm

I would be more inclined to believe 100% on a throttle body style injection system vs. a port injection system. I would be more inclined to believe 100% on a (port injected) 2 stroke engine vs. a 4 stroke engine.. that's a lot of time on the 4 stroke the injector would be spraying fuel at a closed intake valve. If I have the chance to check this out I'll gladly retract my statement.. again..<grin>

I've got a Fluke 88 (among others).. what setting are you measuring duty cycle on a Fluke 189 with?

Jim