Mega Squirt

[ERA 626]

Has anyone here used a mega squirt in a FE cobra? I am about to do this and looking for wiring photos.. I am an electrician by trade but Auto electrical is completely different.We will be using a cam sync sensor in place of the distributor, because of clearance issues. A crank position sensor, O2 sensor, TPS, Vacuum sensor and others I cant remember now... Looking forward to the build. The only thing I am bummed about is loosing the rumpy Idle we all love with a Carburetor motor.

[eschaider]

Which MegaSquirt are you planning on using? If you haven't purchased yet I would encourage you to take a hard look at the MS3-Pro or MS3-Pro Ultimate systems they offer. The Ultimate version will give you more I/O expansion capability.

The MS3-Pro family is the poor mans Haltech / Motec alternative. To be fair both Haltech and Motec will do things the MS3-Pro units do not do (right now). That said you will probably only use 60% or less of the MS3-Pro's capabilities.

The systems are very easy to install and easy to tune. There is a self learning capability to get you out of the blocks fast and then the ability to finesse the tune to get it just the way you want.

A very special nicety is the ability to use anyone's sensors and provide the sensor calibration to the ECU so you don't have to buy rebranded OEM sensors at high price premiums just because of the naming sticker on the sensor and the fact the ECU will not allow you to recalibrate for other sensors.

When you go EFI many people will use a tuning service or buy a day's worth of dyno time. If you get EGT sensors and use good Wideband O2 sensors (NTK) you can easily tune the car yourself without the dyno and save the $1,000 -1,200 of dyno time or whatever the tuning shop charges.

The MS3Pro system uses trim tables in closed loop to home in on the commanded lambda or AFR you specify. Once the trim tables have done their job you can look at the tune and quickly see where it 'wanted to be' and revise your tune to reflect the changes.

When you buy go to DIYAutotune.com to buy. they are the retail face of Megasquirt and have literally everything you will need to implement the EFI system on your car. They also provide a very good support forum on the web for the system.


I think you will like your new EFI ECU choice in the extreme.


Ed

[ERA 626]

Yes I got an MS3 Pro.

[bobcowan]

I used MS on two very different engines. I fabricated the harness for both of them. Read the instructions carefully, and you won't have too many problems. Building it yourself allows you to run the wires where you want them, and you can put connectors where it makes sense for easy maintenance.



I found it easy to tune, and the software is very easy to work with. You can get 90-95% of the tune done just by driving around. But getting it on a chassis dyno with a good tuner for that last 5-10% will really make a difference in drivability. Once tuned, you really don't ever have to touch them again.

One of them went on this engine; 427W stroker, huge cam, IR induction, and flex fuel. I eventually got rid of the distributer, and used a crank trigger with a coil pack.


The other one went on this LS6. Pretty calm engine, running E85, only run on the race track.


The rumpy idle mostly comes from cam choice, and not intake choice. Once properly tuned, port injection will manage a radical cam like it's a little kitten.

[eschaider]

I am in lockstep with everything Bob said, Mike. I would add a couple of additional thoughts. The Megasquirt ECU will allow you to run either a Speed Density style system or a Mas Air Flow, MAF based system.

The Speed Density style system is tuned by modifying the VE (volumetric efficiency) table essentially until the ECU is providing you the smallest fuel trim compensations in closed loop operation.The MAF based system is sort of cool because the MAF actually reports back to the ECU the lbs of air being drawn into the engine. Then based on your commanded AFR the ECU calculates an injector pulse width to deliver the proper amount of fuel to the cylinders to produce the AFR you commanded in the tune.

The MAF based system sounds like its the plan. The challenge is most MAF suppliers either do not provide or provide a MAF transfer function that both you and the ECU soon discover is somewhere out in left field. That's a frustrating clean up that you are left to do in your tune.

The best MAF supplier I have found is a place called Pro-M Racing. It was founded by one of the original fuel system calibration engineers at Ford that designed the Mass Air Flow systems that Ford still uses today. The reason for the MAF based system preference at Ford is the need to meet emissions standards anywhere in the US without the need to retune. High altitude, low altitude, Death Valley in the summer or Nome Alaska in the winter — the MAF based system works correctly everywhere, always, all the time.

So where is the rub? Why doesn't everyone use a MAF based system? The MAF based system challenge turns out to be a composite problem made up of the squirrely MAF suppliers and the actual meter geometry along with a poorly calibrated mass air meter.

The Pro-M guys do it the same way that Ford does it because the founder, as luck would have it, is one of a hand full of guys that actually noodled it out at Ford for Ford. Sadly he has passed on but his original partner and current President, Chris Richards, carries the tradition on for him. Here is a short video clip showing the difference in signal quality for one of their design MAFs vs a more traditional aftermarket tonsil design available just about everywhere. Click here => Pro-M MAF Signal Quality.

A significant challenge for EFI systems is the quality of the voltage signal from the MAF. As the voltage bounces up and down the ECU will continuously chase it, recalculating injector pulse widths to compensate, so the proper air / fuel ratio is maintained. The snafu is the air flow is not really changing, the air flow meter is just not capable of providing a clean signal to the ECU. The continually moving mass air target creates havoc with the fueling logic in the ECU depending on how well the ECU can mute or if you will smooth the voltage perturbations from the MAF.

The second video (it follows the first one) speaks to, among other things, reversion at the MAF attributable to a cam with adequate overlap to give us our rumpity rump idle. As the camshaft overlap causes the air flow to change direction at idle in the MAF, traditional MAFs essentially double or triple count the air mass moving back and forth over the meter tonsil causing the EFI to add more fuel and you guessed it, surge back an forth from rich to lean at idle. The fuel delivery see sawing makes idling the engine more challenging that it needs to be. The second video right after that first one speaks to how the Pro-M meter design defeats the reversion problem.

A MAF will add about $400 to the cost of your EFI system but after you first use one you'll never want to do build anything but a MAF based system.


Ed


p.s. another nicety that's free for nothing is the ability to change intake manifolds, throttle bodies, heads and even camshafts and the tune remains the same because everything you just did only affects the volume (mass) of air the engine injests and of course the MAF catches the change in air flow, reports it to the ECU and the ECU makes the proper fueling corrections all without any intervention on your part — pretty cool, all things considered ...

[ERA 626]

will the Pro-M work with a cross ram manifold with 8 separate runners? where does it get installed?
My builder is telling me that the rumpy Idle will go away due to the lack of a common plenium? lack of reversion? I think I am correct on this not 100% My builder/tuner is pretty sharp on this but I like listening to what others have to say. Putting +/- $30k in a motor I want to educate myself and not rely on others. Thank you for the wiring photos as I am an electrician by trade. But as we all know auto electrical is a complete different ball game...

[bobcowan]

An IR intake system does have different requirements. You need to limit the amount of overlap, because that limits the "fuel cloud" that Webers were famous for. You limit overlap by increase LSA and decreasing total duration. That is what decreases the lumpy idle that you're talking about. Look at the Thumper line of cams. They get their character simply by decrease LSA to 108*.

Also, a "huge" cam will not behave like a huge cam in a stroker. It will be smoother, and act more like a smaller cam.

My point is, an IR engine with EFI will not behave like a carbed race engine with a wild cam. And that's a good thing! It will take that wild high HP engine and tame it, make it purr like a kitten. Until you stomp on the skinny pedal - and then it will scream like a banshee and take off like a rocket.

Been there, and done that.

[ERA 626]

will the Pro-M work with an IR intake? how?

[eschaider]

Originally Posted by ERA 626

will the Pro-M work with an IR intake? how?

Yes but you will need to run it in speed density mode because there is no easy way to use a MAF w/o fabricating an air box that feeds all eight stacks from a common inlet plenum.

Absent the common feed plenum I believe the original Weber equipped cars used a copper tubing sort of interconnect between the bottom side of all the inlet ports to mitigate some of the IR pulsations that play havoc with the fueling of the engine. I don't know how effective the 'fix' was in real life. Perhaps some of the Weber crowd could chime in with their experiences.


Ed

[bobcowan]

Originally Posted by eschaider

Yes but you will need to run it in speed density mode because there is no easy way to use a MAF w/o fabricating an air box that feeds all eight stacks from a common inlet plenum.

Absent the common feed plenum I believe the original Weber equipped cars used a copper tubing sort of interconnect between the bottom side of all the inlet ports to mitigate some of the IR pulsations that play havoc with the fueling of the engine. I don't know how effective the 'fix' was in real life. Perhaps some of the Weber crowd could chime in with their experiences.


Ed

It worked very well.

[olddog]

Just a passing though. I suspect the size of the vacuum can could be optimized to get the smoothest signal. If you could figure a way to plumb this all up on top of the engine, temporarily, such that it could all be removed with no ugly after affects, then use an air cylinder instead of a can. You need a way to lock the cylinder shaft, although allowing it to flutter might be interesting. Now you can vary the volume of the vacuum can, while the engine runs.

[eschaider]

Originally Posted by bobcowan

It worked very well.

Thanks for stepping up Bob. I was hoping one of you guys would. The first time I saw this type of a solution I was impressed both by the ingenuity of it and even more so by the invisibility. Best of all it works!

Way cool ...


Ed

[Gaz64]

Any form of vacuum can plumbed to all runners is only to supply a more steady vacuum signal for MAF sensors, and for power brakes.
It does nothing for reversion since the takeoff port is insignificant in comparison to the inlet port area.

Some manifolds come with the bottom sealed off with a removable plate, where the runners are connected by a small about 3/16 port.
That volume then becomes a large damper to give steady pulsation-free signal strength to MAFs, etc.

Gary

[eschaider]

Originally Posted by Gaz64

Any form of vacuum can plumbed to all runners is only to supply a more steady vacuum signal for MAF sensors, and for power brakes.
It does nothing for reversion since the takeoff port is insignificant in comparison to the inlet port area.

Some manifolds come with the bottom sealed off with a removable plate, where the runners are connected by a small about 3/16 port.
That volume then becomes a large damper to give steady pulsation-free signal strength to MAFs, etc.

Gary

The size of the under port balance tubing can impact the signal muting capability however, once you get up to somewhere around a 0.250" to 0.3125" tubing orifice ID and a sufficiently large vacuum accumulator the majority of the reversion pulsation can be mitigated, not eliminated but virtually eliminated.

The challenge of using a MAF gets into additional creative fabrication and plumbing. Somehow you need to seal all eight of the intakes to a common feed plenum that has a single vent to atmosphere. That vent must house a MAF sensor and air cleaner. Not impossible to do but a not an insignificant design and fabrication challenge.

An interesting variation would be to eliminate the eight individual throttle butterflies and use only a single throttle between the MAF and the common plenum. The streamlined port entry w/o the throttle blade hardware for the eight throttles could easily improve cylinder breathing and therefore engine volumetric efficiency with obvious horsepower improvements.

Ford took the clear individual runner approach on their FR500C road race engine, building the intake manifolding similar to the design I just described. this is what it looked like on the engine with the plenum covers in place;

This is what the manifold looks like with the plenum covers removed;



The individual runner length could be adjusted to tune the engine power to differing rpm bands depending on the track.

Later when Ford went Daytona Prototype racing in 2012 a next generation version of the same intake design was used but fabricated in carbon fiber to reduce weight. The work was done primarily at Roush-Yates and not surprisingly there doesn't seem to be a lot of pics of the engine or it's components available. This is one of the few examples out there;



By mid 2011 the engine was being groomed to go head to head with GM, BMW and other factory teams at the 50th running of the Rolex 24 in Daytona. The intake runners had been shortened, straightened and married up to a new plenum. That January despite all the smart guys betting on the likes of the Factory BMW and Corvette entries to win the event Roush-Yates swept the field cleaning everybody's clock and delivering a 1,2,3 finish reminiscent of Le Mans decades earlier.

In each of these implementations the challenge with using a MAF based EFI with IR style intakes was always the same. Somehow you had to get all the intake runners to draw from a common plenum. Ford had long since dropped the throttle blade per port configuration in favor of individual tuned runners and a single throttle body with a MAF in front of it.

For vintage appearing replicas like ours, we want to see the throttle bodies and eight stacks so barring someone coming up with a really creative approach, the EFI systems will of necessity end up having to use a speed density based fueling model. Although a MAF based system brings some nice benefits the speed density style fueling model does a very good job and is much easier to implement on our cars using IR style intakes.


Ed