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Help with building your Speeduino, installing it, getting it to run etc.
By kaighn80
#46103
so basically Im putting my speedy onto a ford v6 engine, so i will have to pair the injectors, so when i come to size the injectors should i halve the size i would normally need, i.e. if i would normally need 42lb/h injectors for the level of power Im aiming for would i use 21lb/h because Im squirting twice per cycle?
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By jonbill
#46104
No. in normal ranges, the amount of fuel needed is the same whether you give one or two or more squirt so its the same.

at the limit, you need more capacity on 2 squirts because opening and closing is taking up more of the available time in the cycle.
By LPG2CV
#46112
Assuming like for like set up, check out engines with similar HP, not engine capacity for choice of injectors.
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By PSIG
#46135
kaighn80 wrote:
Fri Oct 30, 2020 11:10 am
… i.e. if i would normally need 42lb/h injectors for the level of power Im aiming for would i use 21lb/h because Im squirting twice per cycle?
The others have explained it, but again, no. The number of injection events divides the amount of fuel required ("Req_fuel"), so 2-squirts injects half the fuel on each injection as a 1-squirt setup would. However, the primary reason I jumped-in here was to ask about your build. I know 42 PPH injectors was only an example, but a 2.8L V6 using only 85% flow capacity and properly tuned would generate around 430 horsepower. Even the very expensive Cosworth 2.8 twin-turbos didn't quite get there, so I'm curious... ;)

David

PS: You can see I did injector sizing-to-estimated HP calculations to get that number, and with conservative values. You can calculate it also, in order to properly size your injectors. Proper injector size is important to a well-running setup. If you're just estimating, you can just use an online calculator to get an idea of size, with the most common hurdle being realistic power estimation. Neither smaller or bigger than well-sized is good, and you can read the many reasons why in other threads here.
By kaighn80
#46707
my question was basically because i wasn't sure if i could for example use smaller injectors squirting twice at a higher percentage of max like your 85% example to provide the same amount of fuel as a single larger injector, but having seen how you've explained it that makes sense. I'm building a 2.5l duratec v6 turbo. the aim initially is 400bhp for my kit car, then i intend on building another engine that will go to around 600bhp, swap the two over and put the 400bhp one into my mondeo daily driver if it proves to be reliable, other wise ill dial it back to maybe 300-320bhp which would still be quick enough for everyday normal driving.
By theonewithin
#46708
kaighn80 wrote:
Fri Nov 27, 2020 10:37 am
my question was basically because i wasn't sure if i could for example use smaller injectors squirting twice at a higher percentage of max like your 85% example to provide the same amount of fuel as a single larger injector, but having seen how you've explained it that makes sense. I'm building a 2.5l duratec v6 turbo. the aim initially is 400bhp for my kit car, then i intend on building another engine that will go to around 600bhp, swap the two over and put the 400bhp one into my mondeo daily driver if it proves to be reliable, other wise ill dial it back to maybe 300-320bhp which would still be quick enough for everyday normal driving.

Duty cycle is calculated over any engines entire cycle (720 degrees) so if a 200cc injector is at 85% DC a 100cc will NOT be able to supply enough fuel.

To add... If a 100cc injector is just hitting 99-100% DC swapping them out for 200cc will reduce DC down to ~50%.

At 100% DC a fuel injector is just open for the entire 720 degrees.

It's not open just when the valve is open.
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