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Tofuball's '94 XFi; It's all about city MPG
Topic Started: Mar 12 2011, 08:59 AM (39,437 Views)
Tofuball
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Strange Mechanic

Blegh, my Camry sprung a coolant leak, so I figured I'd do the timing belt while I was in there, that took forever (the V6 Camry with all options sucks to work on). and parts are still on order for that before I can put it completely back together.

My Vanagon decided to spring a massive vac leak somewhere so driving it is like having it at WOT all the time.

And my Geo's exhaust fell off.

Three cars and nothing to drive!! (I'm driving the Geo today, gonna try my hand at welding again . . .)
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100MPG


Tofuball
May 4 2011, 08:15 AM
Maybe. I'm 29.

Fuel injection is pretty simple, you've got a computer and some injectors. Injectors are either on or off, they open and close very quickly, the way that the computer controls them is deciding how long to hold the injector open per squirt.

It makes the decision on how long to hold the injector open per each cycle based on basic input from a few sensors, the main ones being Manifold Air Pressure, Coolant Temperature, Air Temperature, and Engine Tach Signal. Everything else tends to be optional (TPS, EGT, AFM, O2, etc). Optionally you've got an O2 sensor that will allow the ECU to aim for a specific AFR.

Controlling the homogeneity of the mixture isn't as hard as you might think, with sequential fuel injection, you can choose when the injectors fire and for how long- so if you fire just before the beginning of the intake valve opening . . . or somewhere else . . . you get to control where the fuel is during intake.
i think my hairs on fire from just reading that..lol.. i was kinda thinking that it was mostly the o2 sensor controlling air/fuel ratio. and i'm thinking that it can't measure raw fuel. so you could be wasting a lot of fuel even though you can control the o2. this is where good fuel mixing by the ports and good complete burning by the combustion chamber comes in in my mind. i think homogeneity happens in the port and then can be enhanced by the squish in combustion. this is where it gets confusing to me because i have seen cars with carburetors get crazy FE. i'm not convinced that the fuel delivery system is the beat all end all answer to FE. it is great to have a computer to measure and keep things in check according to the sensors, but i'm unsure of the gains to be made by fiddling with the computer. i'm thinking that the fiddling has already been done and the computer makes the tuning easy with the program thats already there. my personal thinking is that the big gains are going to be had from improving the efficiency of the combustion area and port tuning. and based on that thinking, i'm not convinced that the placement of the injector is that critical.

you fire the injector before intake opening, you'll make a puddle of raw fuel for lack of airflow.

its interesting that the NHRA pro stock cars are so well tuned on carburetors, that fuel injection wouldn't show a gain.

i got 26 years on ya... nearly twice your age sparky.. :lol ... thats why you get the computer thing and i don't. boy if i had your energy and my resources, i'd be dangerous.. :lol

Dana
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Tofuball
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You don't get a pool of raw fuel, you avoid it by not firing beforehand :) I was only providing that as an example of how you could tune it - ideally you probably want it opening at some point trailing for best FE, I'll have to read up on what others have done. I can tell you I've made huge MPG gains on other cars mucking with the computer alone :)

NHRA is a great example of not-real-world driving conditions. Carbs can do great things in the hands of a competent tuner, but on a street car they are far from ideal.

Anyway, I plan to preform actual tests to show my theories, so until then I guess it's just theory.

Tonight, if the rain holds up, I hope to have enough time to finally nail this cam-timing issue. Once I do that I can get my baseline and begin to show what gains (if any) I can net. I am positive that I can improve both city and highway MPG significantly (5% to 15% conservative, though others have gained more but done things I wont that impact drivability) simply by messing with the ECU.
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100MPG


your right about NHRA not being real world, WOT is a whole different bag of cats.. my point was that fuel delivery systems of all types can be dialed in to near perfection. how ever maybe in a narrow range of operation. electronic injection is superior for real world driving.

i can't wait to see what you come up with, i'm very interested.

as far as pooling raw fuel, i keep forgetting that you are injecting near the valve and i'm always thinking more like throttle body. you'll be using fine mist and hot valve to atomize fuel. and i'm trying to mix air/fuel by blasting it through the intake runner. two totally different schools of thought.

at some point i hope to get to stand alone tuning and individual injectors, that has to be a better situation

when i do get there, i will probably be using a custom manifold with the injectors a considerable distance from the valve because i still believe in velocity mixing. or i'm old school stuck on it. maybe you will be the one to convince me otherwise.

as far as crazy head work, we are limited by the water jackets in the original castings. it would be fun to relocate the spark plug, but that would be very difficult or really involved for a negligible gain.

Dana
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Tofuball
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http://www.technologyreview.com/energy/24701/page1/

"The key is heating and pressurizing gasoline before injecting it into the combustion chamber"
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Woodie
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Smokey Yunick did that exact same thing to a Pinto back in the 80's.
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Tofuball
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Mac, I'm tired, but I got some quick pics to make you happy ;)

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mcmancuso
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YAY!!! Lookin' good :D
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Tofuball
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That is one of two mufflers on the S2K. I doubt it would fit. Though the blue presilencer seems like it would fit.

I gotta find a decent muffler for this car.
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Tofuball
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Today, did a bunch of work on the Camry.

Also did some exhausting work (with a friend helping with the welding)
Posted Image
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Tofuball
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Ordered a Magnaflow muffler. There is simply no way the S2K muffler will fit without cutting into the spare tire well. Also it's heavy. I'm interested to see what this exhaust sounds like, it'll be straight through the whole way, but I'm hoping the presilencers cut out any drone and help quiet it down some.

The exhaust is painted with 2000F Rustolium paint to help keep it from rusting. The welds each got a bunch of super thick coats of it baked on.
I have no clue what that large silencer is, a friend of mine just gave it to me a long time ago.

I'm probably going to coat and wrap the manifold down to the first silencer to keep heat in. The system is built to slowly expand as the gas travels through it, up to 1.75 inches at the muffler. If the exhaust is quiet enough I will add a larger diffuser, failing that it will get a 1.75 tip pointing at the pavement. If it is still too loud I might consider a reducer before the tail pipe, or a different muffler.

The factory presilencer on mine might have been dead anyway, were they glass packed? I don't think there was anything in it :P
That is one of the reasons I prefer stainless packed. It should still have a slight quieting effect, but the larger one I added quiets things down a lot more (for a totally non scientific test, just try yelling through either one!)
Edited by Tofuball, May 9 2011, 05:33 AM.
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100MPG


looks like you've been busy. i like that injection. the plan is to run three injectors so they can be tuned to each respective cylinder, is that right?

this will be interesting

Dana
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Tofuball
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Not just tuned per different cyl, but timed per cyl. The MS2 can control exactly when to open the injector, I can tune this as part of my attempt in what I was describing earlier, the non homogenized mixture - the very same that allows some engines to "Lean Burn" at incredible ratios.
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100MPG


Tofuball
May 9 2011, 11:33 AM
Not just tuned per different cyl, but timed per cyl. The MS2 can control exactly when to open the injector, I can tune this as part of my attempt in what I was describing earlier, the non homogenized mixture - the very same that allows some engines to "Lean Burn" at incredible ratios.
cool... i do understand fuel and ignition mapping.. its that unmixed rich lean mix thats got me curious. i'm guessing that if you gave it the squirt at the end of the intake stroke versus the beginning that you would certainly get some different end result. this will surely be interesting to follow. :popcorn

Dana
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Tofuball
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My life is insanely busy. I'm really aggrivated at how long this is taking. The parts haven't come yet (muffler) and I'm sure my wudruff key is in fact sheered like previously mentioned and I said "no way" :P

Easy fix if it's the case, easy to get to, just need TIME.
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