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individual throttle bodies MAP or TPS

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Hello,

I want to ask for an 4 cylinder engine with individual throttle bodies (ITB), if we can use a pipe connector between 4 bodies and use a MAP sensor, does it work fine?. I prefer to use MAP and not TPS because it is a rally car , and it race to different height so with different atmoshere pressure.

Thanks you

You don't mention forced induction, so I'll assume it is NA. MAP is not a good reference for load on a ITB setup, as you loose vacuum on quite small throttle openings. Use an atmospheric pressure sensor to deal with altitude differences.

With ITB's you need to use TPS as the load axis for fuel/ignition. If I'm dealing with an engine with mild to moderate cams, I'll incorporate the manifold pressure balance tube to provide a MAP signal that's used for a background fuel calculation (ie double MAP equals double fuel). This provides a more consistent fuel delivery under light throttle conditions on the road.

I'll be trying out that recipe on the next opportunity. ITB on low load is a bit tricky. Thanks! But would you bother with this on a rally car?

Thanks you very much for your answer. I don't understand exactly how to you use the second map with MAP. Simon, if you could explain a little more , it would be helpful.

I'm using a MAP & TPS blend fuel map on my own car that is running ITBs! It's tricky to tune! I'm not sure that I have it done correctly because i use the MAP until 20% throttle position and above that only TPS. I'm going to test the reverse in the next few days to check my theory! I believe the guys in here have more experience in this!

Hi Kindinos, the recipe you describe is how the motorcycle OEMs do it (I believe...). For example Kawasaki ZX-10R; when flashing the ECU, there are fuel maps with MAP as load, and fuel maps with TPS as load. It does some blending/switching in the background that I can't reach with the software I use, but basically MAP for idle and cruise. I believe that the reverse (TPS on idle and cruise) is used in plenum configuration with extreme cams and forced induction. I'm sure there are other people on the forum that know more about this. I have never tried this.

The whole point is to find a signal that is a good representation of load. Using only TPS as load, presents a challenge if you are fussy about your AFR. ITBs flow exponentially, and the difference between for example 2% throttle opening and 5% throttle opening is huge, and not linear at all. So in between the load breakpoints, when the ECU interpolates, it will run rich. You can remedy this by have very tight breakpoints on low load.

Using MAP for load also presents some challenges. There is virtually no more vacuum after approx 30% throttle opening. Depending on your plumbing, the signal can be very noisy. Not all ITBs come prepared for MAP sensor.

So you can see that neither TPS or MAP on its own will give a perfect representation of load in a ITB setup. The best is to use a combination of the two. Different ECU have different ways of dealing with this. I believe Andre had Link ECU in mind when he described "MAP in background calculation". Please correct me if I'm wrong. In the PCLink software, you can set "Equation Load Source" to Load=MAP. This background calculation should stabilize/assist the fueling accuracy on load load when using TPS as load. It should also account for different altitudes.

In some race applications it is considered "good enough" to use TPS only, as the engine doesn't spend a lot of time at idle and cruise. Depending on the ECUs capabilities, using an atmospheric pressure sensor may be your only option to deal with altitude.

Peter, feel free to tell us what brand of ECU you are using.

First of all I want to thanks you for your answer, I didn't have work with ITB and I don't know the tricks. Also, it is important to know how the automotive industry calibrate a stock engine with ITB, so if someone know something more it is my pleasure to read it. For this engine if I calibrate it, I will use a Link G4+ monsoon.

@Helge, I really have no issue with low load tuning performance on alpha n with ITB's. It is important to make sure you use tight zoning for the TPS break points near close throttle. I'd typically use break points such as 0,2,5, 10, 15, 20, 30, 40, 50, 60, 80, 100. You need more resolution near closed throttle than you do at WOT.

@kindinos, I'm not sure what your application is but using a blend like you've described sounds like a potentially messy tuning scenario. If the engine has itb's I'd always use TPS as the axis for the fuel table. If it's turbocharged/supercharged then you'll need to use a separate overlay based off MAP. There's two things to consider depending how your ECU works - If the ECU does a background compensation for MAP (ie double MAP equals double fuel) then all you need to do is use the overlay to adjust your AFR/lambda. If there is no background comp for MAP then you'll need to incorporate this too. I'ts explained in this webinar here: https://www.hpacademy.com/previous-webinars/4d-tuning-link-g4-plus/

@PetroMS check the webinar I linked to above ^^. To answer your second question, traditionally an OE manufacturer will use a MAF sensor for most applications (itb or single throttle/plenum), and hence it doesn't really make any difference to their tuning strategy - mass airflow is mass airflow.

@Andre, I'm sorry for that last comment about TPS only being "good enough", it probably should have been "perfectly fine". I don't really have any issues with it either, but a road car I tuned failed emissions test 2 years after I tuned it, because the TPS had shifted ever so slightly. (It now runs closed loop.) Fun fact, the ZX-10R break points: 1,2 1,8 2,4 2,9 3,5 4,2 4,8 5,4 6,0 6,5 7,7 10 12 15 18 23 29 41 53 76 100 (from factory in the Mitsubishi ECU).

I find it interesting to see what the OEMs that don't use a MAF sensor are doing. Both GSX-R 1000 and the ZX-10R have fuel maps for both IAT (intake air pressure) and TPS. You recently reflashed a YZF R1, right? Can you please share what control strategies you found?

@andre I'm running a B20/Vtec motor with the stock ECU and a Demon2 daughter board! The software I'm tuning is NeptuneRTP! I chose this option as a temporary to run the motor! I haven't decided yet what aftermarket ECU to buy to run the motor! I'm trying to use a TPS only fuel map but I can't start the motor! This is my first time tuning and I'm still learning. Thanks for any tips and advices!

@helge I recently saw the fuel map from a 2014 zx6r using TPS but I didn't have time to check how the setup actually is! I'm sure there is a MAP sensor because there is a common tube below the throttle plates!

@PetrosMS if you have access on a factory Fuel map from a Toyota Corolla 4AGE 20V black top motor you might get a lot of hints! That motor was running ITBs by factory! Everyone correct me if I'm wrong! Also all the BMW M motors are running ITBs if I'm not mistaken!