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#58163
Hi could please anyone help me?

I have just installed a speeduino V04 board on my Suzuki Vitara 1.6 Throttle body injector and I could not make the injector open while cranking. It is a Low-Z injector with resistor in series to limit the current and it works fine when I go to tunerstudio->hardware test and test the injector.

In this option, the injector opens and closes fine according to the specified duty cycle. Also in this conditions I checked the input signal arriving (ground) to the injector and the noise and signal levels are the same when cranking. However, when I’m cranking the engine, the injector stays closed all the time until I stop cranking. When I stop cranking it opens just a little.

Can anyone help me on this? I’m a newbie in this subject.

I attached my current tune.
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#58166
Your resistor is probably too big too allow it to open, you need around 3.25A. I gave up with the resistor idea because you get either a stupidly long opening time or far too high power dissipation in the injector. I took the injector driver from a stock ECU and used that.
#58170
I was going to ask what resistor values you are using. I have had no issues with resistors on TBI injectors with very good latency, though I have not tested the ones Suzuki uses. I use the calculator and set for 14V and 2A, which typically works well. As a general thing, most setups tend to work well with a 5-ohm 25W wire-wound resistor, but calculate it. Please post the injector number.
#58176
PSIG wrote:
Wed Aug 17, 2022 4:46 pm
I was going to ask what resistor values you are using. I have had no issues with resistors on TBI injectors with very good latency, though I have not tested the ones Suzuki uses. I use the calculator and set for 14V and 2A, which typically works well. As a general thing, most setups tend to work well with a 5-ohm 25W wire-wound resistor, but calculate it. Please post the injector number.
I don't think that there is a number on those injectors, I have the number and the specs somewhere but I'm about to go away for a few days. Its a 1 Ohm injector, like I said it needs around 3A to open, from memory the stock driver is a peak-hold, 3.25A peak with a hold current between 1 and 1.25A.
Allowing for 10V at cranking, which is very generous, you would have to come down to a 3 ohm resistor but then at 14V you get 3A which is going to increase the power dissipation and heat to something like 7 times the designed amount. When I was working with these the injectors were over £200 each so reliability was paramount.
Also the opening times become stupidly long (around +10ms) because the peak current is so low and because the fuel delivery in the part open position is non-linear and its a big injector accurate fuelling at idle becomes impossible and you will run out of fuel at higher rpm.
#58180
Well, then that's an odd duck, and a nice coincidence for @nuno_leonor you have info on it. 8-) Sounds like a P&H driver may work, or a careful balance of small resistance for good function. I ran some Rochester TBI injectors on my daily with no resistance (accidentally while testing P&H versus resistor performance) without any problems :lol: but I have to assume the wrap-around fuel flow for cooling (side feed) and accurate latency had something to do with that. Those Rochester/Holleys had 0.7ms latency @14V with 5-ohm resistors, so I wonder why the Suzuki injector is so bad. :?

Assuming the low-volt latency is only during cranking, and the voltage corrections were incapable; then high-latency for that purpose would not be a problem anyway as the cranking PW would be set to deliver the correct fuel, and once running would be at normal voltage and latency. Not that this is going anywhere until we know what the OP is using and the log @jonbill requested. @nuno_leonor?
#58182
it's feasible with the resistors. the opening is way to low. Add to that, the low VE values you have in the area where cranking takes place, and that could account for the injectors not opening.

As a test, in the top third of the first column, set to 100 VE, and see if it improves.

The enrichments that are applied are added as percentages of the current VE value.

Cranking values apply, until the Cranking RPM threshold is passed, and then the fueling transitions from Cranking into Running.

WUE is always applied, and is the % of the current VE. The slope must end at 100%

When in Running mode, the ASE values (and duration) take over. I can't remember if the values need to greater than 100% though!

I'm sure someone will remind me :D
#58288
There is a tendency among the aftermarket ECU community to only consider the resistance of an injector but if you want to compare two injectors electrically you need to know the inductances as well (injector impedance = resistance + inductance).

The specs I have for this Suzuki injector are:
15710-56B00 (OEM)
0-280-150-671 (Bosch) 468 cc/min
1 Ohm
1.65mH

The last time I did any tests on these was around 9 years ago, I'll try and upload some pictures but I'm struggling to get the link to work although its OK if I paste it into the address bar.
The injector opens around 2.6A and the peak detect circuit switches current off at 3.25A with the hold phase switching between 1A and 1.5A.
If you do the calculations on those numbers then at 10V/2.6A you get the following:
No resistor - 0.6ms
1.2R resistor - 0.83ms
2.2R resistor - 1.8ms
3.3R resistor - won't open

I haven't got a record of what the minimum injector PW is I think its about 1ms which is why a fast opening time is important.
The other problem being that if you are then running at 14V with 2.2R resistors the current will be 6.36A in the hold state and the power dissipation is 40.5W*s whereas it should be 1.25W*s - it may run but you will be burning through injectors.

The on-line calculators really aren't much use in the real world.

Image
#58293
Interesting. Those specific Rochester 65 lb·hr units I tested were 2.1-ohm and 1.59mH. While double the resistance, nearly identical inductance. I wonder why the huge difference in operation? Any Ideas?

I also have not encountered the same level of resistor latency as you did in other low-Z injectors, such as the Ford 2-ohm 4.73mH Bosch TBI top-feed injectors or the popular Mitsu INP-008 gray-top 2.4-ohm 7.22mH I've used in several projects with resistors. I'd like to figure why the Suzuki is so odd, as the calculators do tend to work for me. Obviously these others have much higher inductance, but perhaps there is a knee somewhere above 1-ohm and that 1.6mH area, but I'm not sure how I would calculate it at this point, if I had the data.
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