Real tech discussion on design, fabrication, testing, development of custom or adapted parts for Pontiac Fieros. Not questions about the power a CAI will give.
Supposedly, the 3.4 DOHC and 4.0/4.6 N* came with "split spray" injectors from the factory. That is, the orifices are grouped and angled so that half spray at one intake valve, and half spray at the other. I could only find one online reference to this, and it was called a "Directional Multi Orifice injector"
I'm very curious about the "consequences" of using a standard fuel injector on a DOHC engine, where the spray might just be a 30 degree cone, where the port divider would be hit directly with fuel.
Here are some SOHC Quad 4 injectors, it is only an 8 valve engine, but the injectors look the same as my DOHC HO injectors, except mine have more lb/h rating.
They are peak and hold type injectors, and are 32lb/hr. I remember reading in a book at work that listed injectors, and I remember seeing that the Quad 4 HO injectors were bigger than stock 5.0L mustang injectors.
Last edited by befarrer on Sat Jun 02, 2007 1:01 pm, edited 2 times in total.
I figure that if you knife edge the divider your issues will not be too severe. But requires porting heads, and alot more work. Either way there are alot of DOHC engines that probalbly use the single spray type injectors.
depending on the distance of the injector from the divider and the width of the front of the divider (eg not knife edge) you may see varying results. Cant be that big a deal.
Fierobsessed posted this pic of the 3.4 dohc injectors on 60v6:
Shaun41178(2) wrote:There would probably be a hp increase going to a split type pattern if not originally equipped with them. Better MPG too.
The N* has split spray injectors stock.... I ditched them when they started leaking. I'm wondering if what I've got in there now is costing me both hp and mpg.
This is def. a driveability/economy/emissions purpose for OEM engines. Low port velocities and cooler intake valve temps dont vaporize fuel well.
So if you aim smaller jets of fuel directly at the valves and into the chambers, mixing will be better when at low engine speeds, reducing unburnt hydrocarbons, lowering fuel consumption and helping with smoother engine feel.
Once you get the port velocies up high, all bets are off, which is why more race motors mount injectors far from the optimum street engine location which is close the the valve.
Does it matter to our motors?
Ya since we arent running them at 4000rpm and above for more than a couple of seconds now and again.
Will you notice a HUGE differnece in mpg?
Probably not. OEM's do this for emissions for the most part. The EPA doesnt like too see lots of unburnt hydrocarbons in exhaust and if there are huge globs of fuel in the chamber when the plug goes off...they probably wont be lighting as well as they could be.
Emissions is the huge thing here.
You can find injectors that have split spray patterns and ones that have wide angle cones. Normally they are made by Multec and Lucas.
Pintle injectors normally have a 30 degree cone while drilled disc and ball and seat injectors have much wide angles and spray coverage.
