Hi all.
I am wondering about something. I am planning (as you all know) to do a A12 performance engine. My question with the planning comes now with the setup of the management system.
As I understand, most management systems comes with maps you can download for your specific engine to get it at least to idle and run and then you can start to fine tune on the dyno. Now with a completely weird setup of a modified A12 datsun engine(performance cam,head work,etc),motorbike throttles and a management system how do you setup the management system to pulse the correct injector at the exact right time when the specific valve is open for the specific piston and also with the +- right amount of fuel.
I am really confused here as this will be in my eyes a completely from scratch setup just to get the car to start at least.

Basically efi cars use sensors on the engine to let it know when to spark and squirt fuel, so even though your setup may be not very common any good tuner will have no trouble with it. Whatever way you go with you fuel and spark delivery (bank, batch, sequential etc) will determine what sensors or triggers you need to run to tell your ecu what is happening.

i'd suggest you read the megasquirt info pages to help get your head around things. this will help with understanding how any efi system works not just the squirt

good luck!

Generally speaking, most fuel computers will be able to take a crank angle and or distributor signal - to determine the rpm (which is of course a factor they need to reference in order to supply the right amount of fuel) - since they are taking this reading, they can (and do) also use it to time the start of the fuel event. On something lower end, like megasquirt (and I don't mean to suggest it's a bad option, just that it's cheaper generally) will open injectors (according to which you select) either at every spark event, or every second one. Other systems allow true sequential where they only open each injector at a time when that cylinder is on the intake cycle, and typicaly can be timed within that window.

What's probably not as obvious is that whilst sequential is definitely 'the go' if you can achieve it with any given efi setup, the difference vs batch injection isn't massive. Certainly not 'all or nothing' - and still (imho) way better than carbs (and I am a big carby fan).

As to your specific combo, I'm going to speculate that by your description it will be something with less than massive vac at idle, due to cam and possible port sizing specifics, and as such it won't work particularly well with an MAP sensor. For these situations, there's a very straightforward alternative, and not all efi setups can utilise it, so you have to check on it before any purchase. (as a trivial side note, you'll sometimes note that cam timing for modern efi cars has a slightly wider lobe separation angle (or cam phasing/timing on dohc setups) - to produce more idle/low throttle opening/rpm vacuum which gives a better signal for the map sensor and so forth.

Basically what you'd do is to map it via 2 main things - namely throttle position and rpm. That is better than it sounds - basically any time you are at a given rpm and throttle position, it'll require (or run best at) a particular amt of fuel metered in there, so in practice it works very well. Of course it's still possible to utilise coolant temp sensor and even intake air sensor temp signals (efi computer specs willing) on top of that.


Good efi setups also have the equivalent of an accelerator pump in that when they sense a rapid opening of the throttles (via throttle position sensor) they very briefly provide additional fuel over what they would for a given rpm/throttle position in steady state driving.

About the only situation where mapping using rpm and throttle position isn't too good is where you have any significant change in altitude. As you go higher and higher, a tps/rpm mapped setup would run richer and richer (it'd be adding the same amt of fuel, but the air is less dense up higher.

For what it's worth, such a situation isn't likely to come up in a car where the engine is a fairly radical.

Hi there just as another option a friend fitted suzuki gsxr 750 mekuni flat slide carbs to his opel with great succes. No maps no sensor just played around with jets and the car ran amazingly nice with the setup. So I would take a look at that option to. Good luck

Yea, it's a difficult choice superbin.
I spoke to kululadotgroen who guided me in the direction of "Batch Injection". Seems to be the easiest setup that will work for the Datto engine.

I have yamaha r6 quad throtts on my A14. Its pretty wild, and like jmac said, you can't use TPS sensor for fuelling....Well you can. Just you will have VERY poor fuel economy, because of the lack of vacuum it reads 100% after 10% throttle. I got around this with Megasquirt and running a TPS vs MAP setup. It uses TPS for the main table and the MAP for little throttle openings. It works great and I have more fuel economy and POWER!!!, than I have ever had before. I was previously running with a Haltech f7 computer without luck tuning. The f7 couldnt get correct vacuum from the MAP sensor so I had to buy the megasquirt.

Also on another note I am running a EDIS ignition setup with the megasquirt. It involves welding a wheel to the front pulley and mounting a sensor. I am running with no dizzy!!! perfect timing and injection every time. I am running commodore coolant and air sensors as they are easier to calibrate.

With regard to jmac and megasquirt, it is coming out with MSIII sequential injection and onboard datalogging!!! not bad for a DIY ECU.

Highly recommended Megasquirt II!!! it may sound like a porn star. But it is a very capable ECU. And with the promise of megasquirt 3, it will be able to compete with the big boys. Yes MS is hard to tune, but it teaches you alot about EFI. Not everything is supposed to program like a Playstation.

thanks for the info about the new megasquirt versions! I haven't looked at it closely for some years now. I remember back before it was created there was a diy-efi and efi-332 mailing lists. I used to lurk there, but never really contributed anything to the lists. There were some very savvy guys there, and afaik some of them were involved in megasquirt's creation, but I have nfi as to what or how extensive that was.

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I am a bit confused now as I understand that you must run a TPS for throttles due to low vacuum. The VW guys only run TPS with throttles without fuel economy problems at low throttle usage.

No No. I use TPS for the main table. Any TPS setup has resolution issues at low throttle openings. I'm not saying that it doesn't work, just that I use the MAP sensor to provide more control over the fuelling at low throttle openings. MAP generally provides better fuelling resolution over all throttle openings than TPS. But with Quads the there is barely any MAP only between 1-10% throttle.

Hope this clears things up.