440cc injector thoughts? - Mazda MX-6 Forum
 
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post #1 of 4 (permalink) Old 3-28-16, 7:26 Thread Starter
 
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440cc injector thoughts?

I plan on using some 7mgte 440s to start off with, going to be running pump gas as well until I can get a fuel system set up that would support e85. Anyone have any experience with those injectors? Did you max them out quickly? With a good tune are they enough for some decent power? Just bored and thought I'd ask.

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440cc equates to around 41lbs/hr. Accoring to a few online calculators like Fuel Injector Calculator from WitchHunter Performance you would need 56.xx lbs/hr injectors for 300hp @ 40psi base injection pressure considering a max duty cycle of 80%. It's not 100% accurate but it puts you in the ballpark. They use brake specific fuel consumption and assume its gasoline and not ethanol. You need a ratio of about 10/1 under power for ethanol so much bigger fuel system for the same hp. Burn way more ethanol but run much cooler and other good stuff that comes with it.
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How big of a difference is running 50psi fuel pressure than the stock 40? The injectors still only flow 440cc's of fuel at max duty cycle correct?
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Originally Posted by juanpac_tupac View Post
I plan on using some 7mgte 440s to start off with, going to be running pump gas as well until I can get a fuel system set up that would support e85. Anyone have any experience with those injectors? Did you max them out quickly? With a good tune are they enough for some decent power? Just bored and thought I'd ask.
System set-up, people run E85 on performance fuel pumps (like walbro 255lph) all the time, you usually hear they had no problems but eventually swapped in a bigger pump.
When chasing maximum performance you'd want to upgrade everything, bigger lines, rail, regulator, filter, 1000+cc injectors...but most do it in several stages.

As for the 440cc's you get 25% more fuel then stock GT injectors to tune with, you will have the advantage over factory management of being able to pull more timing for higher rpm's and higher boost so you won't need as much fuel to cool the charge air and prevent detonation.
It's all a formula, how much boost can run and how much timing can you pull before it makes no difference running 440's and how efficient your engine (pump) is, you have increased your pump's efficiency by increasing compression and valve travel, turbo, probably exhaust manifold, exhaust size, intercooler pipes...(looking into porting head, other things are larger TB's and intake manifold, external wastegate...) each of these upgrades require more fuel to go with the added air/exhaust the engine should flow and the trade off is the limit of the tuning and fuel and were that puts your turbo on it's flow chart. Mods like lightening the crank, rods, flywheel don't require more fuel and simply reduce the power loss between the pistons and wheels.

Personally I am running a T3 45trim, 2.5" intake/exhaust, a chip and 900cc's of extra fuel, a wide band. The turbo comes to life between 17 and 19lbs
15 lbs was the limit I could boost on stock injectors alone, with the eic controller I could increase boost, 16lbs is a bit faster then 15lbs but 17lbs is a lot faster then 16lbs (the same was true for my mx6 running the same turbo and a long list of performance mods and work I was running 1320 cc's over stock and was maxing them out boosting in the low 20's but I hit the timing wall on stock management).
I am upgrading the set-up with a ported head, intake and TB, a T3 60trim , adjustable FPR and aftermarket fuel pump (worried the extra injectors will starve the fuel rail on the stock pump).
On paper the 60trim flows 62% more then the 45trim, but it has the same trim turbine and housing as the 45trim, I would say on the MX6 setup I would have maxed out the 900CC's of extra fuel at 19 or 20lbs with the 45trim.
With the port work and larger turbo the engine should get more volume of air at the same boost levels as the 45Trim. According to the 60trim map it should flow 21lb/min at about 15lbs (which is the total flow of the 45 trim). How will the turbine wheel and .48A/R housing effect engine flow, how many lbs can I boost on a 60trim before maxing out the 900cc injectors, will the cooler lower boost more air volume require less rich A/F's then the same flow of the 45trim?
Will I make more power maxing 2 extra 450cc's on a 45trim or a 60trim?
Hopefully the 60trim.

---------------------

For swapping to E85, if you want to keep your fuel maps upgrade your injectors by 42% and advance timing and increase boost.
-----------------------A/F--------Lambda
E85 Stoichiometric 9.765 1.000
E85 Max Power Rich 6.975 0.7143
E85 Max Power Lean 8.469 0.8673

E85 has many of the same property's as water/meth injection, predetonation is less likely then cylinder pressure putting a rod through the block.

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