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How does MS translate to fuel percent being deliver (Rotary)

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HI to all,

Lately I have been trying to street tune my Mazda Rx7 turbo 2 S5, and I am having some issues with the fuel percent being delivered when tuning. So far I haven't been able to understand or properly tune such fuel table. I have gained some knowledge from the fuel tuning rotary-link G4+, but somehow I can't apply the methods provided in the video, as I am tuning with MS. The video mentioned before gives examples of fuel enrichment but it is all being presented in percentage instead of MS, and there is not a fuel graphic 2D or 3D being display at such video. Below I will include my base fuel map which is in MS and if is not to much to ask could some one please help me understand how it works when tuning on MS versus the percent of fuel being delivered. I have included my injector firing angle and around were is the red circle, there is were all of my tuning issues are.

My second question is the Staging Bar Injection on such car. How does it work what should be the input data on it. I have been searching around all the web, but I have not found yet any useful data or relevant to my build. Any help on the above mentioned I will appreciated it.


Attached Files

So first up let's deal with millisecond-based fuel tables. These really aren't much different to tune than a percentage or VE based fuel model. Doubling the number in the map will supply twice as much fuel. On this basis you can still make percentage corrections to the fuelling in the same way you see me do in the webinars. The downside from memory with the Haltech injection time model is that there is no background map correction applied so it means you need to make a larger magnitude change as you increase load than you would in the likes of the Link G4+.

I've had very little to do with the staging and I'm certainly not an expert. I'd suggest you open up some of the rotary base maps though so you can see how the staging is dealt with. The staging bar defines the load point beyond which the secondary injectors begin injecting fuel. As such you want a very fine resolution at the staging bar because you then need to reduce the injection time values to cope with the extra fuel being supplied. You'll see this saw tooth step in the base maps.

The staging system on the older Haltechs is unfortunately a little primitive because it doesn't account for load and rpm and you kind of end up doing a juggling act to ensure the primary injectors don't end up maxed out at before the secondaries stage in at high rpm, but also retain a reasonable injection time at low rpm (ideally 1ms or thereabouts).

Feel free to post or send the map along if you'd like specific help. Also, what kind of injectors and whats your base fuel pressure?


Thanks for the response I have found a great resource the information you have provided of the milliseconds. Somehow now I think I have been building a bad or not suitable fuel base map for my turbo Rx7... I do not have that saw tooth step in my fuel base map. Reason being when I uploaded the Haltech fuel base map I do remember that saw step but I eliminated it because I changed my injectors to bigger ones an I tough that was not necessary (Excuse me for the NOOB mistake if so). Andre after reading your response twice I have understood that MS does somehow works like a fuel percent being delivered, but now my question is, if 1MS or thereabouts is ideal for idle how do I know what percent of the injector's CC I am using in such injector at idle.


I will attach my fuel table and others if you could assist me to understand or provide examples of such tables of the MS, how they work, I think I might get a better grasp of how the MS concept works. Any help on this I do appreciate it sincerely. The injectors I am using are the ID1050X for the primaries and ID2000 for secondaries. On the fuel pressure, I have been running 43psi the majority of the time, but I will not lie I have tried 40psi to control the AF ratio as I did not know 1MS was the ideal number for idle. The fuel lines and rails have been upgraded, not sure but I think they are 10AN with automotive fuel regulator. For the pump, I have a Walbro 525lph, think they call it the hellcat fuel pump. Turbo is a Borgwarner S366SX3, and the port of the engine is a large street port.

Thanks again!

Attached Files

Rather than post screenshots just post or send the map itself. Multiple cropped captures just makes more work for everyone.

Also, I think you're making things way too complicated and I don't think you understood what Andre was trying to say. MS = millisecond, that's how long the injector is on after a few compensations for dead time etc. There is no magic number here for your fuel map RE: what it should be set to for idle.

Millisecond pulse numbers in a fuel map don't really mean much by themselves. For instance, if you started with OEM injectors and adjusted every cell in the fuel map so the engine ran perfectly... changing the fuel pressure or swapping to different fuel injectors would require you to change those millisecond numbers. Depending how the battery offset and other compensation tables are set, you might be able to have some rules of thumb like 'the shape of the fuel table should match the shape of the torque curve on the dyno' or 'swapping to injectors that flow twice as much needs you to decrease the fuel pulse by half' but those aren't always perfect relationships. The most useful rule of thumb is probably 'give the engine what it wants', in other words adjust the fuel table numbers so the engine runs well according to the dyno and the wideband sensor.

If you want to know how much fuel you're injecting into the engine, you can get a decent estimate for injector flow using duty cycle. For instance, if the duty cycle is 100% (and there is fuel pressure) then your 1000cc injector should be delivering about 1000 cc/min of fuel. 50% duty should result in half that much, so about 500 cc/min, 10% duty would be about 10% fuel delivered, about 100 cc/min. It's possible to do more math and calculate other things based on fuel flow, but most people use injector duty and fuel pressure to check if the fuel system is near its limit. For instance, high injector duty cycle and abnormally low fuel pressure usually means the engine isn't actually receiving as much flow as the injectors can provide, usually some sort of fuel delivery problem like a clogged filter or low voltage to the fuel pump.

I think Scott has summed things up nicely. There are no magic numbers and you just need to adjust the injection pulse width to achieve the correct air fuel ratio. I'd suggest going back to a Haltech base map and then you can simply increase or decrease the entire fuel table initially to get you in the ball park with your new injectors. Then you can start making finer changes to individual cells. If you change injector size you'll probably need to adjust the staging bar in order to balance the pulse width in the table after the secondaries stage in.

I sincerely appreciate all of your help on this. I now have a better understanding of how MS work. I will take your advice Andre and go back to the base fuel map and start modifying it from there. Again I appreciate all the support on this, as I wasn't being able to understood what was the deal with the MS. Scott thanks much for the detailed explanation (A+).

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