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I thought I would let you guys and girls know of a recently started topic running over on neons.org The discussion is about altering an existing engine to direct fuel injection, or retro fitting a suitable DI engine forums.neons.org/viewtopic.php?f=8&t=407670Something to think about and discus on these long dark cold nights |
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Converting an existing engine to direct injection would have to be a massive amount of work. Assuming that you've got a DOHC four-valve engine to start with, there won't be much real estate left in the combustion chamber to fit the injector, let alone drilling a hole through the head without hitting water. If you don't have four valves then you're probably better off putting four valves in there before worrying about DI.
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Here is a basic transcript of the thread Topic started by bshurden The SKYACTIV-G is a family of direct injection gasoline engines. The engine compression ratio is increased to 14:1. To reduce the risk of engine knock at high compression, residual gas is reduced by using a 4-2-1 exhaust system, implementing a piston cavity, and optimizing fuel injection. In addition, combustion duration is shortened by intensifying air flow, increasing injection pressure, and using multi-hole injectors. Mazda motors are impressive That was cited from Wikipedia Question is this.... How exactly is Mazda running 13 and 14:1 compression ratios on pump gas? 4-2-1 headers and advanced fuel injection doesn't satisfy my hunger for knowledge. Can anyone help me understand? 13:1 dd first gen sounds fantastic! joncot1812 Super high fuel pressure. Don't worry about detonation when you can inject the fuel exactly when you need to. The Neon was originally supposed to have a 1000psi direct injected 1.5L 2 stroke with some awesome numbers. But anyway, you can run some crazy high compression numbers with a really high fuel pressure and direct injection.occasional demons To elaborate more...
Direct injection lets you add the fuel with just enough lead time before the spark, so it is not in there long enough to pre ignite. The very high pressure atomizes it better, so you don't need to rely on the combustion chamber design as much to get the fuel droplets and air swirling around to do it for you.
The higher temp of the compressed air also helps vaporize the fuel. Some diesels run at 14:1 just for perspective.
Also, since there is no fuel displacing air in the intake tract, there is more air available to the engine with the same sized valves/ports. You can run more valve overlap, because there is no risk of unburned fuel getting into the exhaust. All this makes for more power potential, with less emissions.
I'm sure there are more benefits/technical stuff, but those are the main points.BCoN One drawback to DI is the amount of carbon buildup on the intake valves from the lack of fuel in the intake tract. Some DI cars get a nasty amount of carbon buildup.
The SkyActiv-G engines have a very interesting piston design to aid in avoiding pre-ignition. Everything listed in the Wiki article is correct, but it fails to mention what the engineers were trying to achieve, lower combustion chamber temperatures. Autozine has an article with a decent section on the SkyActiv-G that includes a couple pictures to help with understanding.occasional demons I'm sure a retro fit would cost more than the average neon would ever be worth.
While cost vs value isn't really a primary concern with these things, you have to hope the car never gets totaled, unless you are paying for specific insurance to cover the value. If you can get that sort of coverage to begin with.
A drive line swap would probably be the least expensive route. But a DI 2.4 is still a decent pipe dream....
I'm sure the carbon on the intake valves ports could be solved by not having EGR, and an effective oil separator for the PCV system. If there is just air passing the valve, it should stay clean. The only way it could get contamination is if the valve is opening way too early, and pressure from the cylinder is pushing out the intake. A good air filter being a given here.
I can understand lowering the combustion temps for emissions reasons, but for a performance related pipe dream retrofit... E85 would shine pretty well here I would also think. You might even get regular injection gasoline type fuel mileage out of E85 with this.bshurden Yeah.... A beautiful pipe dream indeed... I was doing some preliminary searching on Mazda and their new engine and the compression ratios blend mind and I had to ask. Now I know... Looks like I need to research who sells DI platforms, how old they are and what not. I'd love to find a platform with DI. The possibilities are intriguing. bshurden For pipe dream sake... I would assume the dohc would be easier to retrofit direct injection over a sohc. I base this on the angle of the intake. However a sohc had on cam in the middle of head... Thoughts? I'm being bi-curious because I know a guy.... He claims to have done this with a 99s miata. Same guy who built my intake. I'm gonna bounce this idea off him after I get some basics covered. Vitor Not allot of room on the head for hole straight down through, even less on conbustion surface. Then 1500psi fuel to contend with.bshurden Why so much psi?
I ask because the Mercury optimax 2 stroke has been on my mind. It's a direct port air and fuel injected motor. 90 psi air and 80 psi fuel. Both spray into each other for better atomization. Compression is only 180 psi... Similar to a neon. Dave99rt yippie, all that fancy technology got them 155 hp and 148 tq
the mileage rating is respectable at least, but there are a bunch of competitors cars that are rated the same.
maybe you can toss some huge cams in it and gain 50 hp?Vitor
if your cylinder pressure cold is ~300psi, you need at least that much fuel pressure to get fuel into the cylinder. Want it to atomize, then you need 3 to 4x that at very least. Now imagine hot engine, cylinder pressure will be even higher, hence the DI fuel pump pushing pressure into 1500psi+ range.MCarp22
The previous gen 3 is 12:1 and lacks the 4-2-1 header, they still put down a respectable 140wtq and 142whp. Out of a 2 liter on 87 octane, that's pretty awesome.bshurden Ok maybe I'm not grasping what I need to here but 1500 psi isn't necessary if the piston isn't actively in a compression stroke. If the valve is open why so much psi? Your saying all Mazda SKYACTIV-G motors have 1500 psi fuel pumps? Seems absurd.... I know the Mercury had a maximum of 80 psi at operating temperature. MCarp22
DI engines have a much shorter window of time to inject fuel, as you can't just have the fuel waiting in the intake port for the next intake phase. The modern high pressure systems are also set up to inject late in the compression phase, after the intake valve closes.MichNeon
^This and the fact that the higher fuel pressures create a finer atomization of the fuel when it gets sprayed. Also, the higher compression goes, the higher fuel psi you need to atomize the fuel for better and complete combustion, not to mention for better emissions.
In the automotive world, (new car wise) there is no such thing as a carb anymore. Due to the regs that the U.S. gov't is pushing out, even the engines on the lawnmowers, snowmobiles, etc are going into the fuel injection direction. W/in the next 20 years or less, there won't be any carbs at all.Vitor Good riddance! There are now batteryless Fi system on low CC motorcycles that work very well and don't die or plug up if left with fuel for extended periods of time.I for one, look forward to our new fuel injection overlords on small power equipment.CGS12 One thing I would like to know is just how bad the fuel/oil delusion is with one of these mazda engines. One thing people have not really been paying too much attention to just how bad direct injection engines are with oil life. I believe Audi owners are lucky to get 4K-5K oil changes even with the best synthetic oils and this seems to also be a issue with Fords new Ecoboost as well.Drakito A valid argument.
Another valid argument against direct injection is that if the injector sticks open it can cut a hole through the piston. I have seen it on diesels, a bluetec cummins to be exact. Injector stuck due to red farm fuel contaminants and a bypassed filter/dryer. The injector went into nuts mode and 30,000psi shot into the cylinder, cutting the piston, rod, crank, and oil pan. Engine was dead about 2 seconds later.occasional demons
Interesting.
You would think since unburned fuel is in the cylinder for a much shorter window of time/less cylinder wall area exposed, and a bit less of it is needed to produce the same power, there would be less oil contamination.
But then if one technology is exceeding the capabilities of another in the system (piston rings), there isn't going to be perfect harmony. I guess it comes to a point when you can only put so much new tech into the original platform of the piston engine. You have to wonder how much longer before the EPA bans that too. :grin:autoxer62 Speaking as one who owns a bunch of old cars with carburetors, I'll take the new tech over the old. Yeah, it's fun to play with the old cars, but it was even more fun taking the Neon to autocrosses this year and just driving it instead of worrying about whether or not it would behave itself all the way through the run. What would be cool is a Dodge engine we could swap into a Neon with DI included.occasional demons The carburetors I truly don't miss are the ones that they botched up trying to meet emissions requirements. You needed to darn near take out a second mortgage if one wore out. I recall the one for my Omni was somewhere in the $700 to $800 range.
I bought the one from Mopar Performance for $225. And even that felt like not a lot of Vaseline was used. At least throttle bodies use needle bearings now, and rarely wear out in that aspect. You can buy 4 new injectors for a bargain compared to what a carburetor costs.Taylor@blackstarperformance i guess you have not looked at the cost of a set of id1000's or id2200sMichNeon Those would be the mid to late 70's to mid 80's, before the companies started going to fuel injection. The worst ones were the japanese carbs, where they tried to put all the controls in them and make them work like a fuel injected system. I had a 86 D50, the Mikuni carb on the 2.6 in the truck had a choke system so automatic, you never needed to do the close the choke routine on cold start. It also had a water cooling circuit in it.newlitemotorist www.google.com/patents/US6955154
This is how I would start! A buddy of mine and I have talked extensively in the past about doing something like this, using our own design but after looking through google patents we found that the idea was already out there. Use and injector like this with your existing cylinder head, plumb the fuel lines out the tip where the plug wire boots are and run a belt driven rotary pump. It would not be that hard...if you could get a hold of a set of these injectors.
The quoted patent isnt exactly what I would use but the concept is spot on. Develop some sort of pop style injector that would be activated by the rotary pump.newlitemotorist Here is another one...still uses a solenoid which I would avoid. Still a pipe dream but its a way around the issue of fitting an injector.
www.google.com/patents/US5497744MichNeon FYI, all electrically/electronically controlled injectors are solenoid operated. The exception is the ones that are mechanically operated off of the camshaft. Those do not have solenoids in them.newlitemotorist I am referring to the injector design which is mechanically popped by a rotary pump...no solenoids, just line pressure. Look into the pre-2004 ve tdi injection system for reference.MichNeon Oh, i'm familiar with the mechanical poppet type, those were used on diesels for many years before the newer electronic injectors that are in them now. The problem with the mechanical types is that they have a fixed profile. The electronically controlled injectors can be held open longer or shorter to suit the conditions. Not only for performance, but also for emissions and fuel mileage, especially with the higher system pressures nowadays.bshurden Ok, This has been on my mind since 2006....
Do away with intake cam, intake all together. Machine down cam journals for intake cam. Ski jump pistons, direct port and air injection... Install compressor where stock ac compressor is. Reserve a tank in trunk for sudden loads the compressor can't handle.
Inspired by 3.0 liter 250 hp and 300 hp mercury outboard optimax motors.
Less moving parts and responsive like a supercharger. Just new direction.... Money would be extensive I know. Bouncing theories here.
Now.
Someone play devils advocate.Drakito Why don't we have someone just make some solenoids for the valves and we can run without cams, ala F1 cars. You setup your "cam" through the computer and let the solenoids drive the valves to match. That way you could have a stock idle, crane 18 midrange, and crane 28+ top end....
Og I guess the price might get in the way, $1,500 per solenoid is kinda spendy.occasional demons I recall Electromotive was playing with that idea, or someone was using Electromotive's hardware. This was back in the late eighties or early nineties. I'm not sure they had fast enough solenoids to actuate the valves then tho. But yeah, it is an awesome idea. You can have the ultimate sleeper. Might actually get some low end torque out of a 2.0 :grin:"MichNeon The Dart's multiair engine uses solenoids to actuate the intake valves inline with the cam. :pardon: The solenoids can vary the lift of the intake valves quite a bit, they can even keep the intake valves closed.occasional demons That would hamper compression braking significantly. No air coming in to compress.
I can see the benefits for longer coast periods with MTX cars and even ATX, depending on how well the clutches stay locked during decel. Longer off throttle times mean more MPG.
Getting rid of engine driven cams also frees up power to the wheels, to some extent. Depends on how much electrical demand the solenoids place on the alternator. The downside is, you may not limp it home from as far when the alternator takes a poop. Of course there is one more argument for higher than 12 volt systems.bshurden Sounds interesting..... But intriguing... Motors with no intake manifold tb or intake cam.... The possibilities... |
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