Injectors: Design I or Design II???

[stamar]

definiitely using different injectors makes the mpg on the obc totally irrelevant. it could have actually gone down.

[nando]

Just an update for this posts.

I did purchase and install Design III injectors. Noticed a significant difference!

MPG increased 8-10mpg per OBC
Low range torque increased slightly
Idle smoothed out slightly

Worn Design I's vs rebuilt Design III's.

Highly recommend Design III upgrade for M20 owners.

you can't go by the OBC if you change your injectors. the DME will decrease the PW (to keep overall fuel flow the same). the OBC and econometer measure fuel economy by injector size and PW. since it thinks you still have stock sized injectors, it looks like it's flowing less fuel (lower PW).

[Gregs///M]

I see, thanks for those updates regarding economy acquisition. I have not calculated the MPG difference, however I can say that my gas tank does last longer.

[stamar]

Ive heard that a lot.

But just like you, everyone is replacing old injectors with rebuilt ones.

Like I said somewhere in here, design one isnt necessarily any more wasteful its just less reliable. More likely to be dripping after these years.
its got 1 hole going down as opposed to 4 going out at an angle, a design made mostly to leak less when theres slop
Thats the smooth idle. 1 mpg should be really optimisitic. It shouldnt be any worse at least unless someone messed it up.

[Quinthirty]

I have not calculated the MPG difference, however I can say that my gas tank does last longer.

Is everything on your engine stock?

Perhaps use the same old method to measure number of miles / kms ran over number of gallons / liters to find out fuel consumption?

[Gregs///M]

Yes, my M20 is completely stock with the exception of Supersprint cat-back system. 60K on motor.

[stamar]

id be interested in your gas mileage, and also the symptoms you had before the new injectors that got cured.

Ive got a really common thing which is cold idle shudders. Id give it like 50 50 chance its some injectors. I cant think of anything to do but pull some out and switch em around and see if they leak in a different cylinder or not.

when it takes longer to start and warm up it definitely uses gas could be a lot.

[Gregs///M]

When the block and head was swapped into the car, the PO used the original parts such as injectors, etc. After 200k (mileage on chassis,) the idle became a bit rough, only at idle tho. That's about it.

The new injectors smooth idle.

[a_thomasmr23]

I would like to point out that the injectors spray on the valve when designed correctly i.e. the factory ones so when you go to the the 4 valve style set up your now spraying on to the intake track in the head which is much cooler than the back of the valve.

You rely on the heat to evaporated the fuel and a smaller droplet size evaps in a shorter period of time. There is about a couple hundred SAE papers covering this for those with access and the time.

The best choice would then be a single cone with the right angle Design III injector. Which I've found minus being 20mm shorter. Comes from 98-00 ford explorer with the 4.0 SOHC v6 engine. part #: xl2e-a1c, 0 280 155 900 ford and bosch.

[Quinthirty]

Did you have to change the wire connectors when you converted to Design IIIs?

[Gregs///M]

Nope, same connectors

[Quinthirty]

Care to share the brand and part number of the injectors? I'm seriously thinking about an upgrade now. By the way, are you running on 2.5 bar or 3.0 bar on the FPR? Would that have an effect on performance? Just want to make it closer to stock as possible...Ok, maybe an ebay chip, if that makes for more fuel efficiency and a bit of power.

Thanks.

[Gregs///M]

They are design III from Bosch. Purchased them from a forum member here but they are all over the internet. I do not know the part numbers. They are yellow with all plastic body.

[a_thomasmr23]

They are general from the ford mustang and are designed for 3 bar pressure use them at 3 bar to get the best effect though they will work at both pressures.

[Gregs///M]

I use 3 bar yes.