Megasquirt: Can I run one TWM TB with my Lynx manifold?

[AustrianVespaGuy]

This idea has been nagging at me for some time. I currently run Megasqurit on a 318 plenum setup which is fine, but I although I don't think I'll go back to a carb, I really miss the lynx manifold setup! So I'm wondering if it's possible to run a single TWM throttle body on the lynx with Megasquirt injection. I've run some of the numbers and two ~45lb. injectors set up for 2 injections per cycle (either batch or bank fire) should provide the correct amount of fuel, but I'm just not sure how important of a role the injection timing will play while trying to feed 2 cylinders with one injector. One other option might be to use a 1.8i head with the 4 injector ports in the head, but I don't know how well those heads fit with 2002 blocks/pistons. Any thoughts? Thanks!

-Carl

[Tommy]

I don't see any problem in your plan. Just set the MS for 4 cylinders and 2 injectors. At least I can't tell why it wouldn't work. Your calculation about the injector size seems correct too.

Tommy

[ifayeoh]

Man that would be one $ick install if you did that! I would love to see that, keep us posted!

[Swiftus]

Don't worry about the injection timing if the injectors are not next to the ports. Some old school injection systems used to fire all of the injectors on every cycle... just leaving a build up of fuel that would eventually get sucked in to the cylinder.

Here is my question. Not being familiar with the parts, why is it that you can,t have individual injectors for the cylinders? Is it that the manifold has no accommodations for them? And since there is no place for the injectors in the manifold, the throttle body would be where the injectors go?

Throttle body injection on single throttle body cars has worked in the past. Its fault is that it is less precise than single cylinder injection which makes the whole injection process less efficient and less responsive. Also, with a poorly designed manifold, one can easily have fuel condensation and very inaccurate fuel control.

However, if the manifold you are using was designed for a carb, putting a throttle body equipped with injectors on it would be like putting an electronically controlled carb on the manifold.

I like it! Do the math, get the right parts and follow through. It should work perfectly.

HTH,

Jay

Post... It has been a while since I last read the Megasquirt documentation, but I do believe that you can have two different banks of injectors that are controlled under alternative load circumstances. So, you would have a set of injectors that can supply most of the fuel required for the car to drive around normally... an "idle circuit" of injectors and you can also have a set of injectors larger than normal for your "secondary circuit"

I believe it is worth looking in to. I think v3.5 can control 4 injectors internally and having a set of just-to-small injectors as well as a set of just-to-big injectors will allow you to be more precise with your fueling of the car when efficiency is key.

One more thing to add. I don't know what type of throttle body you are looking at using, but if I were you, I would try to find a staged throttle body if you are using only 1. Having only a single, large, butterfly plate makes causes the control of air at low throttle input to be a crapshoot. Having a staged throttle body (like on m42 motors) lets the driver (and ecu) have more precise control over the air entering the engine at lower throttle positions. This is another key part into making an efficient driving machine.

However, if you are only after a WOT beast, disregard most of what I just said. WOT control via fuel injection is very easy and requires very little thought. Do some volume displacement calculations and you're done

[TKMad]

It will work, but then you will have a wet manifold design, which is a lot harder to tune well. My first megasquirt project was an MGB, which has siamese ports so I ended up with a setup similar to what you are contemplating. It was WAY better than carbs, but I certainly prefer the injector-over-the-valve setup.

[Dave_PA]

AGREED!

when you do this please put up a blog on it. I WOULD LOVE to do this!!

Dave

[Preyupy]

With the Lynx manifold you should not have any trouble running a single 2 BBL throttle body with the MS system. There is a HUGE advantage having the manifiold pairing the cylinders that are 360 deg apart (crankshaft degrees) The MGB and other engines that siamese cylinder intake ports wind up with a air pulse problem with 2 cylinders being back to back then a long pause while the other 2 paired cylinders have their intake events. You just need to fire the 2 injectors like they were 4 indipendent injectors (easy to set up in MS) This should be a great system.

[eurotrash]

I LOVE this idea.

Do you EFI mad scientists think that having the runners machined and injector bungs pressed in, to emulate the 318i positioning, for an over the valve system would be advantageous? - or just stick with the above injector set up?

I have a 318i fuel rail, which is why I ask.

[Preyupy]

I don't know how much of an improvement installing the injectors right at the port in the head would be but I doubt it would be very much. There MIGHT be a slight change in drivability (for better or worse) but I seriously doubt it will make any difference in peak power or torque. I really don't think it would be worth the time and $$$ but if you are a machinest and want to give it a try and the only cost is a couple of extra injectors you might want to try it. I would start out with just the 2 injectors in the TB and see how it works, you can always change later without much trouble.

[Dave_PA]

Porn...you're giving me porn to look at in the office Jason...

omg would that be a setup of setups!!!

[TKMad]

Unequal length runners and a wet manifold are far from an optimum setup. That said, having the injectors over the valves would be better. No more power probably, but better efficiency and tunability.

The walls of the manifold will be coated with fuel. When you decelerate the low pressure sucks that fuel off the walls and causes a very rich condition. Then when you go to accelerate again some of the fuel added will stick to the walls so you accel enrich has to be higher. What makes that more complicated is that it is very temperature sensitive. If you heat the manifold with the bypass line it will help quite a bit.

It will certainly look cool though...

[Harv]

If you do do it, don't go any larger than a 40mm ITB.

John

[Preyupy]

You need to remember the manifold was designed to be run "wet" with a carburetor. Yes injectors mounted to spray just as the air is entering the combustion chamber is usually better but there are times moving the injector further out the intake track helps with throttle response or HP. Without knowing what the specs of his engine are ( actual displacement, compression ratio, cam, valves, port work, header and exhaust) or his entended use (street car, SOLO II, track toy or some combination of some or all) the differences in where the injectors are placed or the difference in manifold runner length could easily be unmeasurable, OR could be a huge difference After playing with these engines for a long time I'm guessing it will be much closer to the unmeasurable end of the scale. The biggest advantage to running a single TB and injection with this manifold is the ease of tuning and the fact atomization of the fuel is not as dependent on velocity and you will be able to run a larger throat in the TB than you could even think about with a DCOE and still make it run very well at low speeds.

[TobyB]

Some old school injection systems used to fire all of the injectors on every cycle

almost all still do, to a large extent, as does all but the hotrodded MegaSquirt-

the only real advantage to getting fussy with sequential is at low pulse widths.

After 30% or so, the injector has to be on longer than the valve's open

anyway.

So you might get slight emissions gains at idle and low widths,

but as Byron says, it's all gonna be fractional.

But having the Lynx and TWM- that'll be serious eye candy, and unique, too.

Do it!

t

[Swiftus]

I've had my mind juggling the intricacies of direct injection for so long that I have misplaced most of my port injection knowledge... I thought that you start to forget things when you're old... The only reason I recalled the old-school injection routine was because of my recent assistance with my neighbor's Mystery Machine (like the one in Scooby Do) and its Bosch J, K, L, M or whatever letter it should be injection system. Its a 60's Chevy van with a 3 speed manual attached to a 6 cylinder gas motor that red lines at 4200 rpm... when the $3000 MFI (Mechanical Fuel Injection or as my neighbor calls it; that Mother F%#*%@ Injection) system isn't being an idiot.

Direct injection cannot fire on every pass... hopefully for obvious reasons... And the new Piezoelectric injectors are fast enough to fire more than 7 times per injection period. Need more fuel? Get a bigger injector or more pressure... Some of the high performance diesel injection systems nowadays are running 2500+ bar at the injectors (or about 35,000 psi). That amount of pressure on a common rail system means more fuel is available faster, allowing far more precise control than even port injection, let alone throttle body injection.

A few have said that throttle body injection will produce the same amount of performance as other forms of injection and I respectfully disagree. From what I understand, One *should* theoretically be able to have the same PEAK performance from ANY fuel delivery system. Tuning for a single performance point is not the most difficult thing in the world to do and could be achieve with a spicket dripping fuel onto a hot plate in front of the intake manifold.

The trick is creating the best performance over the entire range of engine conditions, load and flow. Being a dynamic system, it is inherently better to be closer to the dynamic to have the most control. True, fuel needs time to mix with air to create a uniform and ideal fuel / air mixture, but the newest ideas are pointing to progressive burns as being more efficient at burning the fuel. For example, many direct injections systems are now doing a series of injections WHILE the fuel air mixture is combusting to create a more even and effective burn.

Efficiency in this case doesn't necessarily mean trading power for economy, it just means extracting the most amount of energy from the fuel as possible. How that is delivered in the big picture is up to the user.

That said, if one moves the fuel control further away from the combustion center, they are inherently giving themselves a bigger challenge to accurately control the ideal fuel / air mixture in the desired circumstance. Its like trying to sign your name on a sheet of paper with a longer and longer pen. You may eventually be able to sign it accurately and precisely, but only after more time and more thought than if you were to use a normal length pen.

All of that said, most of it is moot in this forum and for this case. We, being barbaric members of the tribe of the 2002 have no-where near the resources (money, time, intelligence... choose whatever reason you see fit. I know that all of them apply to myself) to reap the benefits of the more intricate fuel injection systems. Simply moving from carb to EFI (sorry tii owners... the K-fish is a glorified carburetor) is probably the only difference one will be able to notice in both power and economy. Beyond that, many days of seat-o-the-pants tuning could produce better power and efficiency figures, but nothing like redesigning the entire intake, port, valvetrain, and exhaust systems would do... as well as tuning the block's harmonics, creating better oscillation assemblies, etc.

I guess what I am trying to say is that for what we can achieve in garages and sheds, I have to agree with others here that most any fuel injection system retrofitted to an m10 motor will be equally efficient...

After seeing images of the manifold and throttle bodies being discussed, I think that this system wouldn't be complete without a set of these:

Gooooooo Methanol!!! (compressed air works too if you don't want any more power but you still want to make yourself giggle)