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Tofuball's '94 XFi; It's all about city MPG
Topic Started: Mar 12 2011, 08:59 AM (39,441 Views)
bogs
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Duct tape heals all wounds

Tofuball
Apr 24 2011, 04:53 PM
...flames can travel all the way from your combustion chamber to a tailgater near you!
Huh, back in the day we put sparkplugs into the tail pipe to achieve the same result :lol
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Bad Bent
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Facetious Educated Donkey

:smackface I was going to say...
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Good post bogs. :lol
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Tofuball
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Strange Mechanic

bogs
Apr 25 2011, 04:37 AM
Tofuball
Apr 24 2011, 04:53 PM
...flames can travel all the way from your combustion chamber to a tailgater near you!
Huh, back in the day we put sparkplugs into the tail pipe to achieve the same result :lol
Back in the day you didn't have a catalyst in the way :) And cars ran insanely rich from the factory . . .

Besides that's not the reason I'm removing it, I just deemed it superfluous for my build.
Edited by Tofuball, Apr 26 2011, 09:54 AM.
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100MPG


good thread and you have some good ideas, when i first told a friend of mine about my FE project he said that i needed to get WB02 and run the mixture at 18to1, also said that planes have been flown at 22 to 1. it certainly seems your going in the right direction.

how bad does that exhaust port suck, i couldn't believe it when i seen a hard 90 around the head bolt and again around the spark plug. i'm all about getting the heat out of the head and the hot gases slamming those walls is going to be a real problem. i think ceramic coating the port is going to be the only answer.

i like your idea for hot cold intake

i plan to fallow your thread as i'm curious to see how that mega squirt works out

Dana
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Tofuball
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Strange Mechanic

You don't need a WBO2, it just helps, especially since the MegaSquirt can basically tune itself with one (And full time closed loop)

You don't run 18:1 all the time. You run different ratios and timing at different speeds, loads, temperatures, ect.

You can DEFINITELY run leaner then the stock 14.7:1 on cruise.

Getting heat OUT of the engine isn't your goal - in fact you WANT to keep a good bit of it in . . a hot engine likes to run leaner . . . just doubt that this is the way to do it.

Glad you like what I've said :)

I HAVE the MS, it's ready to go in, the only thing stopping me is the lack of a decent baseline. I have to fix my cam-timing issue and exhaust leak - and get good repeatable baseline numbers before I can start raving about how much my mods helped :P
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100MPG


yep, i read the whole thread and seen that you already had the MS and were having a hard time getting a baseline

i'm probably going to baseline mine on a dyno because i am going to try to pull the torque peak lower. higher torque at lower rpm so i can pull a taller gear. 100 mpg at 70mph is the goal.

heat as far as getting into closed loop is your friend, the rest of the time its your enemy. i think i'm working with some different theories than you are. i don't even know where my compression will fall yet, it may be 12 or 16 to 1 so everything needs to be smooth and cool.

i have a new project thread and will document and explain everything as i go.

you have a much better handle on the mapped fuel and spark mapping than i do, i understand all of it but not that computer savy to be able to program it.. but i just may learn

Dana
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Tofuball
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Strange Mechanic

That's fine, I plan to share my maps :)
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Tofuball
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Though if you're running some insane compression ratio they'll have to be modified a bit, but at least you'll have a base map to work with.

Just a guess, but I don't think you're going to run as hot as you think you will, sure things get hotter when you run a bit leaner, but after you get "over the hump" things cool down again. You're also not going to have your foot that deep into the throttle so density will be much lower.

It's LOADED driving (not so much cruise) that you'll run into issues there. You can keep temps down with water\alky injection, changes to timing, EGR, etc.

Or you could get rid of a whole lot of heat by converting to a miller cycle type

Basically, you have a camshaft that keeps the intake port open much longer, and you use a supercharger to compress the air instead of the piston (the super charger is also more efficient at it for the first part of the stroke, have the intake valve close when the graphs cross eachother). Then you can run the compressed (heated) air through an intercooler before it enters the chamber, dumping a lot of excess heat that way.
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100MPG


Tofuball
Apr 27 2011, 06:14 AM
Though if you're running some insane compression ratio they'll have to be modified a bit, but at least you'll have a base map to work with.

Just a guess, but I don't think you're going to run as hot as you think you will, sure things get hotter when you run a bit leaner, but after you get "over the hump" things cool down again. You're also not going to have your foot that deep into the throttle so density will be much lower.

It's LOADED driving (not so much cruise) that you'll run into issues there. You can keep temps down with water\alky injection, changes to timing, EGR, etc.

Or you could get rid of a whole lot of heat by converting to a miller cycle type

Basically, you have a camshaft that keeps the intake port open much longer, and you use a supercharger to compress the air instead of the piston (the super charger is also more efficient at it for the first part of the stroke, have the intake valve close when the graphs cross eachother). Then you can run the compressed (heated) air through an intercooler before it enters the chamber, dumping a lot of excess heat that way.
yer getting pretty deep on me..lol... it's weird to get my head around this, i'm used to building for high performance.

i'm thinking that at low rpm the cam only lets air in and out and otherwise doesn't effect anything, at high rpm it effects everything. also at low rpm the friction is low and you have lots of time to cool everything, flow air, burn fuel, etc. therefor i'm not too concerned about airflow in the high performance sense, but concentrating on the exhaust port getting the heat out and the intake port being the proper velocity for my rpm range.

for the most part i am going to redesign the combustion chamber for fastest and cleanest burn and narrow the intake ports so they find harmony at under 2k. if this engine shuts off at 4k for lack of air, that will be just fine with me as high rpms is not its purpose. i kinda look at it as tuning a gas fueled engine like a diesel.

so initially i'm going to work on engine design mods and let the computer adjust for the better burn efficiencies and what. after i get that established, then maybe i will look at some fuel and timing mapping.

shocking how cheap the mega squirt is compared to units like motec. but i'll be watching and learning from you, so that when the time comes for it i will hopefully be ready.

i may even need to add some toluene(114 octane) to my fuel or run race gas..lol.. i'm just looking for crazy FE.

and a more efficient burning combustion chamber will run cooler.

Dana
Edited by 100MPG, Apr 27 2011, 09:54 AM.
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Tofuball
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The stock ECU simply will not "remap" to handle changes like that, except where it runs closed loop. It doesn't even have a MAF, so it has no clue about the mass of air flowing in, it infers it from MAP and air temp signals.

Cam timing affects low RPM just as much as high. But you're right about wanting to keep the engine at low RPM.

Some high performance stuff still applies, making it easier to flow air in and out of the engine is always a plus.

And remember, the more POWER you can make at a low RPM, usually the higher you can gear it!

Also, if you're worried about getting heat out that much, just drop the temp of the thermostat.
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Coche Blanco
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Don't run a thermostat.

The stock ECU or whatever it is called is mapped really good. IIRC. CoyoteX told me this at Geopalooza '10.
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100MPG


Tofuball
Apr 27 2011, 02:20 PM
The stock ECU simply will not "remap" to handle changes like that, except where it runs closed loop. It doesn't even have a MAF, so it has no clue about the mass of air flowing in, it infers it from MAP and air temp signals.

Cam timing affects low RPM just as much as high. But you're right about wanting to keep the engine at low RPM.

Some high performance stuff still applies, making it easier to flow air in and out of the engine is always a plus.

And remember, the more POWER you can make at a low RPM, usually the higher you can gear it!

Also, if you're worried about getting heat out that much, just drop the temp of the thermostat.
thats my whole plan is to make more torque at a lower rpm and gear it to the moon. in theory if your turning half the rpms at the same speed, you should be burning half the fuel.

i didn't realize the the stock ecu was so inept at doing adjustments

i'm not sure if you can really affect anything with cam timing at 2k rpms, i kinda think its just letting air in and out and the XFI cam is probably about as good as it gets. that was their plan when they designed it.

with lift and duration changes you can allow more air for higher rpms and horsepower, but i don't think we have a use for more air at 2000 rpm. as long as it gets what it needs, its fine.

the single biggest event in cam timing is when the intake closes as thats where your dynamic compression is decided. thats how you put a big cam in and make less pressure/power. the static compression and the intake closing have to match. when you advance the cam, the intake closing is what your moving that makes the difference

torque i believe is a function of cubic inches, compression and combustion efficiency. you can move it around in the power band with cams and ports, but it kinda is what it is.

i think that best torque happens a best volumetric efficiency and that to me is when the intake port is flowing and mixing air/fuel for best burn. there is a sweet spot in the velocity curve.

iv'e seen a lot of race engines that were over ported and made low power. the ford boss 429 engines were dogs until they made them 600 cubic inch and they moved enough air to make the ports work.

way back when in the early days of the harley xr750 flat track program, they always concentrated on the intake ports and ignored the exhausts. when they did finally show the exhaust some love, they realized that getting the heat out of the head allowed them to run much higher compression.

i believe that everything has to be in balance to work together, and to me it makes no sense to have a 7000 rpm port hooked to a 4000 rpm engine. iv'e seen harley stroker race engines ported so big that they couldn't even achieve the rpms necessary to make the ports work because of the long stroke.

you hear all your life that the horsepower is in the heads. so everybody grabs a grinder and ruins their heads by porting em out, all that really does is move the sweet spot up in the rpm range and kill some low rpm power. the real power to be found is in the combustion chamber. torque does the work, more rpms wont give you more torque.

head porting is badly misunderstood, its not so much about getting more air as it is getting the ports to work for best air fuel mix and burn. i believe that you can make an engine run really smooth at a really low rpm, you just need the right size port that is working at that low rpm. why not make the port do its best work from 700 to 4000 rpm when now its working from 2000 to 7000 rpms.

then port injection begs the question of air velocity and fuel/air mixing when the fuel is injected almost into the cylinder. where does the mixing take place? is the short distance of port enough to get a good mix?

these things are all just my opinion of coarse but my opinions are formed by many years of research and hands on involvement

i was wondering if it was possible to bypass whatever sensor does the closed loop thing and run closed loop all the time, and i'm sure that you know the answer to this.

and hey its fun to bounce my thoughts and ideas off you, i wish i knew the lingo for the ecu dialog, sorry i did'nt mean to write a book

Dana
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100MPG


Coche Blanco
Apr 27 2011, 03:20 PM
Don't run a thermostat.

The stock ECU or whatever it is called is mapped really good. IIRC. CoyoteX told me this at Geopalooza '10.
the thermostat does two things. one of them is to hold the water in the radiator long enough to cool down..in a lot of cases taking out the thermostat gives you a slow warm up and then it just keeps getting hotter and hotter, all the conditions matter of coarse.

i'm going to try not running a thermostat, but i will be switching the flow off and on with an electric water pump

Dana
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Tofuball
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Coche Blanco
Apr 27 2011, 03:20 PM
Don't run a thermostat.

The stock ECU or whatever it is called is mapped really good. IIRC. CoyoteX told me this at Geopalooza '10.
The hotter the engine runs, the leaner it is comfortable running. This tends to save gas, but has its own issues (especially above 210)
The colder it runs, the richer it will want to be. Colder will tend to net you more power (to a point) but I wouldn't go much below 160 as wear becomes a factor.

I agree with the idea that the stock ECU is mapped VERY, VERY well - for a stock engine.
At least this XFi ECU, as I watch it, does very efficient things that I am not used to seeing in stock ECUs, especially given its age.
(Fuel cut on at 1500, stays on down to about 1250. Runs lean at most transitions, rather accurately. Stays in closed loop for a much larger span then most ECUs, closed-loop idle control, etc)


However, it is not made to handle an engine that runs too far outside the parameters of a stocker, and has almost no method for adjusting to modifications.
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Tofuball
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100MPG
Apr 27 2011, 04:44 PM
thats my whole plan is to make more torque at a lower rpm and gear it to the moon. in theory if your turning half the rpms at the same speed, you should be burning half the fuel.


Somewhat, though you will be deeper into the throttle, but generally more efficient :)

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i didn't realize the the stock ecu was so inept at doing adjustments

Some stock ECUs, rarely, can adjust to mild changes. And those tend to be newer ECUs (such as the ones you usually find controlling the LSx)

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i'm not sure if you can really affect anything with cam timing at 2k rpms, i kinda think its just letting air in and out and the XFI cam is probably about as good as it gets. that was their plan when they designed it.


Somewhat. If you were willing to sacrifice emissions and power, you could gain even more MPG from the cam.

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with lift and duration changes you can allow more air for higher rpms and horsepower, but i don't think we have a use for more air at 2000 rpm. as long as it gets what it needs, its fine.


More air, more power, more gearing. Though after about 80% throttle the mixture tends to have to run even richer (I would not go leaner then 13.8:1 for most of that point unless you really know what you are doing there, and that's pushing it).

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the single biggest event in cam timing is when the intake closes as thats where your dynamic compression is decided. thats how you put a big cam in and make less pressure/power. the static compression and the intake closing have to match. when you advance the cam, the intake closing is what your moving that makes the difference


Everything makes a difference, but yes, you are correct. :)

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torque i believe is a function of cubic inches, compression and combustion efficiency. you can move it around in the power band with cams and ports, but it kinda is what it is.


Basically, yes. There are some exceptions to this, such as turbos\supers (worse MPG unless being used in some form of miller cycle) velocity tuning (can make better MPG) and intake pressure wave tuning (can DEFINITELY make better MPG).

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i think that best torque happens a best volumetric efficiency and that to me is when the intake port is flowing and mixing air/fuel for best burn. there is a sweet spot in the velocity curve.


Best VE is usually with your foot all the way down and the revs up. It's good for power but this won't produce the best fuel used to power produced ratio. You are thinking on the right track though.

Quote:
 
iv'e seen a lot of race engines that were over ported and made low power. the ford boss 429 engines were dogs until they made them 600 cubic inch and they moved enough air to make the ports work.

way back when in the early days of the harley xr750 flat track program, they always concentrated on the intake ports and ignored the exhausts. when they did finally show the exhaust some love, they realized that getting the heat out of the head allowed them to run much higher compression.


The issue with this kind of thinking is it is somewhat different then max MPG thinking - heat management theory is almost completely different, you're not running under such heavy load . . .

I'm interested to see what you come up with - you might prove me wrong :)

Also, from what I've seen, gains from increased compression ratio start to really drop off after 11:1 or so if you're running gas (they're still there though).

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i believe that everything has to be in balance to work together, and to me it makes no sense to have a 7000 rpm port hooked to a 4000 rpm engine. iv'e seen harley stroker race engines ported so big that they couldn't even achieve the rpms necessary to make the ports work because of the long stroke.

you hear all your life that the horsepower is in the heads. so everybody grabs a grinder and ruins their heads by porting em out, all that really does is move the sweet spot up in the rpm range and kill some low rpm power. the real power to be found is in the combustion chamber. torque does the work, more rpms wont give you more torque.


Heh, I used to do the opposite, controlling the shape, texture, and size of ports (sometimes making them smaller, changing the distance to the "head" etc) I've found some pretty impressive gains porting even stock intake manifolds for some vehicles (particularly the S5 N/A RX-7)

Quote:
 
head porting is badly misunderstood, its not so much about getting more air as it is getting the ports to work for best air fuel mix and burn. i believe that you can make an engine run really smooth at a really low rpm, you just need the right size port that is working at that low rpm. why not make the port do its best work from 700 to 4000 rpm when now its working from 2000 to 7000 rpms.


Agreed. Though that's kind of a fat range to tune for. I recommend using 1K to 2K for your calculations. Again, you may be able to prove me wrong here. I'm interested to see what kind of port you come up with and how it differs from mine, or stock.

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then port injection begs the question of air velocity and fuel/air mixing when the fuel is injected almost into the cylinder. where does the mixing take place? is the short distance of port enough to get a good mix?


It mixes by hitting the hot intake valve, and having a better injector from the start (smaller droplet size, finer control). Also less fuel is stuck to the walls.

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these things are all just my opinion of coarse but my opinions are formed by many years of research and hands on involvement

I can tell, I usually don't run in to people who have even a beginning understanding of port velocity or dynamic compression ratio.

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i was wondering if it was possible to bypass whatever sensor does the closed loop thing and run closed loop all the time, and i'm sure that you know the answer to this.

When you're in closed loop, you're only at 14.7:1. Why not just go standalone? It's not a single sensor, but a host of them helping the ECU decide to be in closed loop.

Quote:
 
and hey its fun to bounce my thoughts and ideas off you, i wish i knew the lingo for the ecu dialog, sorry i did'nt mean to write a book

Awesome, glad to help, remember I am not all knowing, still learning. If something I say looks wrong, PLEASE correct me. And by all means, write all the books you like; I join forums for discussions such as this.

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the thermostat does two things. one of them is to hold the water in the radiator long enough to cool down..in a lot of cases taking out the thermostat gives you a slow warm up and then it just keeps getting hotter and hotter, all the conditions matter of coarse.

i'm going to try not running a thermostat, but i will be switching the flow off and on with an electric water pump


Remember, the coolant is still circulating in a stock setup when the thermostat is closed, just not going out to the radiator. If the water stays still for any reasonable length of time, you will develop hot spots, warping, or even evaporation.
Edited by Tofuball, Apr 27 2011, 05:50 PM.
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