megasquirt3 injector choice
12-23-2011, 02:40 PM
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megasquirt3 injector choice OK I am trying to pick the best injector for my forged 370 with all pro heads and a pt88 turbo on e85. I am really leaning towards the fic 160's. I just need some extra assurance that the high impedance bigger injectors will work well for my application. I do not want to run resistors, and would run a driver box for low imp. if I had too. Any real world input would be greatly appreciated
12-24-2011, 08:07 AM
#2
160s should be large enough for your engine. That or what about running 2 different injectors per cly. Or is this just an all out race car. If a road car, running 2 different ones will allow you to use say 60lb injectors while regular driving, then when boost kicks in run both 100s and the 60s?
Another option would be to run the Fuel pump at lower the fuel pressure down like in most newer vehicles when at low Tps settings then ramp in full when it sees any boost. Like 25-30psi then 70..
Another option would be to run the Fuel pump at lower the fuel pressure down like in most newer vehicles when at low Tps settings then ramp in full when it sees any boost. Like 25-30psi then 70..
12-24-2011, 11:33 AM
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Thanks for the reply. My entire fuel system is ready to handle the 160's. I was running low impedance 160's on my turbo v6 with a classic fast system. with this 370, I am pretty set on the idea of running 160's I just want to know how people are liking the high impedance models for tuning and idle. I would say this: with the megasquirt I am considering running 8 low impedance 120's with the driver box in sequential mode than also using the megasquirt to drive two more injectors pre throttle body. My thinking was that this will do two things, supply extra fuel and since I am running E85 it will substantially drop the inlet temps helping my intercooler.
12-24-2011, 11:47 AM
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What i was getting at was that the fuel injectors have a minimum time that they can physically shut on and off smoothly and be in a controlled state. At higher fuel pressures the MINIMUM amount of fuel the injector can flow is higher than with lower base fuel pressure. The Injector being so large will just make for poor idle characteristics due to it just cant go slow enough to dump in less fuel smoothly. Rich conditions at too low of rpm and inj pw. From the 160s may occur just due to your engine isnt making the power at idle / low rpms to use what the MINIMUM amount of fuel is. Once you get into the sweet spot of inj pw then things are better. That is why running 2 sets instead of one is better sometimes.
As for the low vs high, With that big it may just be better to go with your 120s and the 2 more injectors if needed. It will be easier to tune down low rpm range.
When picking the injector, I try to see what the smallest injector i can use for my application and still have just a bit of safety margin on top. Usually 85-90 duty cycle max is target. I minipulate fuel pressure at different loads to maintain a 50-80 duty cycle on the injector as that is where it is pretty happy and i get nice fuel atomization from this. On large builds it may take a few injector swaps to find the exact size needed. But that is just how i do it...
As for the low vs high, With that big it may just be better to go with your 120s and the 2 more injectors if needed. It will be easier to tune down low rpm range.
When picking the injector, I try to see what the smallest injector i can use for my application and still have just a bit of safety margin on top. Usually 85-90 duty cycle max is target. I minipulate fuel pressure at different loads to maintain a 50-80 duty cycle on the injector as that is where it is pretty happy and i get nice fuel atomization from this. On large builds it may take a few injector swaps to find the exact size needed. But that is just how i do it...
12-24-2011, 12:10 PM
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That is good info that I will consider. My experience on the bosch low imp 160's on my 231 cu inch v6 on e85 was that they did not idle well unless i set it on the rich side. I used a base pressure of 43 psi and a 1:1 regulator. I had to tune them to about 12.8afr (fuel scale) with the wideband. Then it would idle ok. One nice thing about e85 is I never fouled the plugs idling it that rich I drove this setup on the street alot. It had good throttle response and ran a best of 10.4@130 at 28psi boost. I have read some posts of people saying that with the new hi imp 160's you could run a lower PW which allowed them to idle better. Isn't it true that you can get more out of a low imp injector than a high imp due to the fact that a low imp can be driven to a higher duty cycle and the low imp opens more responsive due to a higher current flow. That being said I have heard that the new high imp bigger injectors technology has improved and they perform much better than they used to.
02-28-2012, 07:10 AM
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That is good info that I will consider. My experience on the bosch low imp 160's on my 231 cu inch v6 on e85 was that they did not idle well unless i set it on the rich side. I used a base pressure of 43 psi and a 1:1 regulator. I had to tune them to about 12.8afr (fuel scale) with the wideband. Then it would idle ok. One nice thing about e85 is I never fouled the plugs idling it that rich I drove this setup on the street alot. It had good throttle response and ran a best of 10.4@130 at 28psi boost. I have read some posts of people saying that with the new hi imp 160's you could run a lower PW which allowed them to idle better. Isn't it true that you can get more out of a low imp injector than a high imp due to the fact that a low imp can be driven to a higher duty cycle and the low imp opens more responsive due to a higher current flow. That being said I have heard that the new high imp bigger injectors technology has improved and they perform much better than they used to.
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02-28-2012, 08:56 PM
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I am not familiar with that system. I was using a fast system with C-Com software. In c-com I just set the injector size to 160, then I set the injector opening time to 1.0 mS Then after getting it to start and run I monitored the wideband to achieve the best idle which for me was at 12.8 AFR using a wideband o2 sensor set on the gas scale. With my idle at operating temperature and 850 rpm's my injector DC was at 1.2% I should also include this was using E85. That is all I did, I hope this helps and good luck. James
