So somewhere in my box of doodads and whatchyacallits I have a Cold Start Injector from some old project of mine that I gave up on, or was it cause of a science project... anyway; I have one. I ALSO, thanks to an engineering project last year, have a pressure switch from Hobbs. I was just thinking. Suppose all hell breaks loose, and for some reason my engine starts overboosting and/or going lean. (wastegate failure, just plain **** up in the tuning, bad gas, whatever), Has anyone ever seen a system that injects a bunch of gasoline into the engine suddenly/outside the normal fuel system? My thinking is I could put the pressure switch onto any old boosted vacuum line, and in addition wire in a switch based on the output of my AEM wideband, and a dash switch for driver discretion. Like so /------Pressure Switch-----\ 12v-------voltage switch------------injector-----ground \-------toggle on dash-----/ Obviously it wont protect against EVERYTHING, but if **** starts going south I'd rather bog the engine down with an influx of fuel (which IIRC also will cool the engine) than just shut it down and maybe not have the reaction time required and have a borked engine. Anyone got anything to add? Other switches you think it should encompass? Will it not work? etc. Input is welcome!
A boosted vacuum line will not tell you if you are going lean. If you overboost by a couple psi, your fuel system should handle it (and you will, boosted systems fluctuate a little). If you overboost a bunch, insufficient fuel will not be your problem, it will be pre-detonation due to increased combustion chamber pressures. That is just the way I see it. Are you going fuel injected or carbureted?
No the boost sensor is more because i wont have tuned for say... A complete wastegate failure. I think this turbo flows enough to push this motor to 20 psi iirc.. And if i dont notice on the boost gauge right away, I'm buying some new things right there haah (in addition to a wastegate) I may have worded it poorly but i have an aem wideband with an auxiliary output. So with a switch working off of that, when it crosses a certain threshold (say 4.6 v) i know my afr is at an undesirable level... I was under the impression preignition is usually caused by to hot of a chamber/hot spots on the piston.... And that by keeping the boost low/at the desired level and by making sure to NEVER run lean i should be able to avoid this. I do intend to buy and install forged pistons eventually, but id like for that to be when my budget permits, not when something unforeseen ****s up and blows a ring land or similar. I'm going carbureted, but I'm taking most of my logic from tuning my fuel injected chrysler for nitrous... I was told to add monitor my knock sensors and if i saw any (small amounts) to add a but of fuel as it will a) richen it up and b) cool it off.... So i guess i thought that if i see a LOT of knock like if a wastegate fails or the carb fails or the fuel pressures boost reference pops off or.... Etc. i could add a LOT of fuel to stop it, temporarily. This may have been in error.. Thanks for the input btw, I've never found a community as willing to help as this one.
Good info. Look at it this way, if your waste gate fails, and your boost shoots way up (more air), if you add fuel based on that (more fuel), you are adding 2 of the 3 ingredients for more power, plain and simple. The only way to reduce the power is to pull timing, pull ALL fuel, or pull air (let off the throttle). Since you are carb'ed, there is no pulling fuel. I would guess (I have not read/tested/seen this) that by the time your over boost switch activates, your solenoid opens and fuel starts to flow, the extra fuel will be too late anyway. You would need a high pressure pump so that you could get the required delta across that cold start injector to flow. (if you want 30psi at the injector, and with 10psi boost, you need fuel at 40psi on the injector) Instead of a fuel solenoid, I would invest in a big, red shift light and wire that to your over boost switch. If you see red, lift!
Well i do already have it, but i do like the red shift idea as i was mainly concerned with if i happen to not be staring directly at the gauge when it happens... Also just to clarify i wasnt planning in continuing at wot if the system went off, id be lifting regardless... And i do have a high pressure pump, I'll see if anyone has an old shift light i could buy! Thanks
you would be better off with having the pressure switch turn off the ignition than trying to put more fuel in. detonation occurs from hots spots or over compressing fuel to the point of self ignition. fuel can only handle so much compression. that what octane ratings are all about. you could use the hobbs switch to trigger a timing retard module if you didnt want it shut the motor off completely.
I hadnt considered that... my first thought is that having the engine shut off 100% might be dangerous. It is manual steering though.... and I would be stopping the second i slowed down anyway... Ill look into the timing retard module! In fact I'm looking right now to see how hard it would be to integrate that into my existing ignition system. If it's super difficult I could probably setup a relay that would cut power to the fuel pump AND ignition system. Just make the engine a big ole rolling air pump. Just thinking out loud here guys....
cutting the fuel pump on a carb wont help. cutting the fuel will cause it lean out. leaning it out will melt pistons. dont cut fuel.
