Programmable EFI Questions?

[Brian Carlson]

All,
I am a newbie to this site...Though I don't own a '40, I am finishing up a 289FIA Cobra with DC&O stack injection managed by an Accel DFI system. I am currently struggling mightily with getting a good vacuum signal to the MAP which is in a central plenum of the manifold. This, and other posts, has been of great interest to me and I am accepting any help!

Question to the group - TWM and DC&O both make manifolds with central plenums that pull from each ITB runner. I am getting 9"-10" of manifold vacuum with a cam that should pull at least 15"-18". I have read much that ITB's are not good for sending accurate vacuum signal due to reversion and other properties. My question is this...Can I actually get a good enough signal to run the Accel box? TWM says so, several dyno shops say so. True?

 

[Ross Nicol]

Brian does the Accel system allow for the TPS (throttle position sensor) to be used as the sole input for load? I have the DC&O setup with Motec M48 and I use the TPS this way, then just vent the Map sensor to barometric pressure.Works fine.
Ross

 

[Brian Carlson]

Ross,
Thanks for the note. The Accel DFI system only uses the MAP sensor to determine load. The DC&O manifold I have has a central plenum and I have the MAP plumbed to that. I have searched many threads on this site and it seems that others have used that signal as input for their ECU, however, I have not heard a definitive answer on whether that is a 'clean' vacuum signal with good resolution. (Good enough that is to control the entire EFI fueling strategy)

I was thinking that if I really got into a bind with this EFI / MAP signal deal that I could swap the MAP and TPS inputs since they are both 5 volt linear inputs. I'd like to leave that as a last resort since it is totally uncharted territory.

Does your DC&O have a central plenum as well? If so, do you know what kind of manifold vacuum you pull?

 

[Paul Thompson 'Hooligan']

Hi Brian -

Before switching to Motec, we used an early Accel Dfi unit and the Calmap software supplied with it to run a 347 with Kinsler bodies. We initially had both Map and throttle sensors fitted and although it was possible with the Accel unit to sort of filter the lower region of the Map sensor's output, we never got a sensible enough signal to get a clean idle. We eventually ditched it, leaving it to atmosphere and used just the single throttle posn sensor which worked really well. The car had a fairly agressive cam but still retained reasonable manners for road use, certainly better injected than it ever managed on a Lorus 4-barrel...

Hope you get it sorted.

 

[Pete McCluskey.]

Interesting thread, thanks for posting. I'm running DC&O throttle bodies and an Autronic ECU. It works fine but I would love to hook up with someone in the Brisbane area who could tutor me in the finer points of tuning the system.

 

[Ross Nicol]

Brian yes I have the central plenum but have not used it, so can't help on the vacuum side of things.

Pete Probably a good Idea to gain a general understanding of how EFI works via internet, books etc and then the Autronic system will make sense and you will be able to converse with other Autronic experts.

Ross

 

[Pete McCluskey.]

Hi Ross, I have a fair idea of how EFI works but I need tuning knowledge. I.E. I'm scared to hook my lap top into the ecu in case I stuff something up.

What is Electronic Fuel Injection?

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Basically, an electronic fuel injection system (EFI) works by delivering high pressure fuel to an electrically operated valve called an injector. Where the electronic wizardry comes in, is delivering the right amount of fuel, at precisely the right time for every engine operating condition, across the rev range.​

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Carbs vs Fuel Injection
Want to Compare? Click Here​

</TD></TR></TBODY></TABLE>The electronic control unit (ECU) receives information from a variety of sensors, in and around the engine and makes the appropriate adjustments to fuel delivery to maintain perfect, preset air/fuel ratios.
The problem with original equipment EFI is that reprogramming for nonstandard applications involved creating a new chip for the ECU, a process beyond the capabilities of most engine tuners. Even if a modified chip was available commercially, it was still not possible to “tune” the injection system for further engine modifications. In the late 1980s a number of programmable aftermarket injection system ECUs arrived in the US, such as those manufactured by 034EFI, http://www.aempower.com/AEM, DFI (Accel), http://www.fuelairspark.com/Electromotive, http://www.haltech.com/Felpro (FAST), http://www.pectelusa.com/Haltech, Hondata, http://www.fuelairspark.com/Link, MoTeC, OnTronic 32-bit Fuel Injection, http://www.pectelusa.com/SDS, Split Second, and Wolf. These systems can be programmed “on line” by connecting them to an IBM-type personal computer. They allow the tuner access to the fuel maps for idle, transition, wide open throttle, cold start, turbo boost enrichment, and in some cases, ignition timing.

Tim Suddard, owner and editor of Grassroots Motorsport Magazine, writing in an article about EFI states the following major advantages:​

• The extreme accuracy of fuel delivery by the ECU, at any load or RPM, provides the engine with air/fuel mixtures that fall within a tiny window of accuracy required for maximum power, or maximum economy.
• EFI systems are not subject to the usual fuel surge and frothing associated with floats and float bowls in carburetors. One of the limiting factors in race car lap times has been the ability of the fuel system to deal with G forces. Gravitational forces in both horizontal and vertical planes have no effect on EFI systems.
• ECU control of air/fuel ratios allows racing engines to safely operate nearer to the “ragged edge”.
• PC programmable EFI can easily be adapted to suit future engine modifications as a vehicle evolves. Adjustments to fuel and ignition curves being as simple as making a few keystrokes on a PC.
• EFI generally permits greater flexibility of intake manifolds designed to achieve higher inlet air flow rates and consistent cylinder to cylinder air/fuel distribution.
• More efficient, higher compression ratios are usable, due to accurate fuel metering. This is especially the case with EFI units incorporating ignition control.
• When converting to forced induction, turbocharging, or supercharging, EFI will enable the user to program boost-relative enrichment easily, usually leading to substantial power increases as a result of accurate fuel delivery.
• Most EFI systems compensate automatically for changes in altitude and ambient temperature. Calibrating a fuel system for a specific race venue is hardly necessary with EFI, if adjustments are to be made, a few keystrokes on a PC are all that is necessary.
• Some EFI systems also have a provision for a cockpit-mounted mixture control with which the driver can vary the air/fuel ratio. TWM's HALMETER AF30 is particularly useful for this purpose, providing a visual, onboard read out of the air/fuel ratio with its 30 LED display.
• The solid state electronics in EFI systems are not susceptible to the mechanical failures associated with carburetors. Tuning parameters remain as programmed, with never any need to adjust for wear.

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[Ross Nicol]

Time to plug in the laptop then Pete.Just make sure you have the data backed up securely and then play, it's the best way just like the young kids do and we don't.

Ross:uneasy:

 

[Brian Carlson]

Ross,
Thanks, I appreciate the response. If I keep looking long enough I'll find someone who knows - lots of good expertise here and other sites.​

Pete,
Agree with Ross, if you have your data saved there is nothing that cannot be undone and very little to lose. A keen sense of observation and an understanding of basic engine physics is all you need. EFI and carbs do the same thing, one with physical hardware the other with the laptop. There is no more or less capability to negatively impact your motor through EFI versus a carb and distributor - might as well learn!​

The description of EFI from the top of the thread is a bit daunting...I had my head spinning about EFI tuning a while back and a friend sent me the following note to help me get straight. It's a little basic, but serves the purpose. Enjoy.​

Brian - think of your V8 as eight single cylinder engines. Every one needs a beer-glass full of air and a shot of petroleum based spirits (gas) to operate. The air is controlled by the hard bits of the motor you already have installed, your ECU simply controls the size of the shot. Depending on whether your motor is just waking up or it's partying hard, it may ask more or less 'spirits'. The EFI is simply the bartender that follows the rulebook for how much to serve and how often. Your rulebook may have lots of conditions to follow or only a few. But at the end of the day, it's all about the shot. Engines (and people!) have very predictable behavior if they have had too much or too little. Tuning is all about the exercise of observing that behavior under all conditions in the rule book and making changes to the size of the shot! Let the party begin!​

 

[JohnMcL]

Kalun,
You asked about books. Try "Engine Management" by Dave Walker, published by Haynes in the UK, www.haynes.co.uk. Comes with Emerald mapping software on CD and details the whole procedure of using it. It's the perfect guide even if you use non-Emerald ECU and software.
John McL

 

[Peter Olliviere]

I bumped this thread to ask a question of the folks who have lived with the Motec EFI.

I have been driving my car quite a bit since I had it tuned on a Dyno and have begun the bug swatting part of the build. I have one problem that effects my ability to drive in a smooth manner at low speeds. When running in second gear or even third at around 2K RPM holding a steady speed, any movement of the throttle makes the engine act like it is on a light switch, either on or off. If I ease the throttle the fuel is cut and the car compression brakes suddenly. If I step on the gas the engine comes back right away as fuel is restored.

I see several parameters within the Motec software that effect the adding or deleting of fuel but I am unable to understand which ones would help reduce or smooth the lift throttle fuel flow.

Peter

 

[Paul Thompson 'Hooligan']

Hi Peter -

From your desciption of the fuel being cut - have you tried disabling the 'overrun fuel cut' ?

It is found in the Misc Functions menu as per pics below.

Also - what configuration are you running? Throttle position sensor + Manifold pressure, Wideband Lambda?

Does it run cleanly throughout the rest of the map and at all other throttle positions?

Finally - do you have a progressive linkage on the throttle bodies - we made a lever arrangement such that half pedal gave much less than half butterfly movement - beforehand the car was a bit of an animal to drive.

 

[Peter Olliviere]

Paul,
thanks for your response.

First the car runs cleanly across the rev band with good throttle response cold or warm.

I am running TPS as my control method.

No, i have not installed a progressive throttle, I have a direct one to one relationship between the linkage and the butterfly.

I do not have the laptop I use for tuning with me right now but I believe the Overrun Fuel Cut looks like the sample you attached. My question is, is the example shown active or inactive?

 

[Paul Thompson 'Hooligan']

In the example above it is inactive..

I assume the throttle pot has been tested and definately does not have any dead spots ? - I have seen a brand-new Ford one faulty from new...

The progressive throttle is not essential, but made the car a lot friendlier on the road in traffic - on track it was never an issue.

 

[Ross Nicol]

Peter
As Paul suggests I reckon your problem will be fixed by fitting a progressive throttle.I have a linear one like yours at the moment and it is pretty digital (on or off).On the highway you barely touch the throttle and your at the speed limit. On the track it's not a problem because unless I'm braking, the pedal is on the floor, well as far down as fear allows anyway.

Ross