Upgrading Injectors to 17.5lb : New FPR?

[E turd]

Alright. So, I'm pretty sure my injectors are the original ones and I'd like to run the m50/s50 17.5lb injectors to get a better spray pattern and to possibly reduce engine noise resulting from noisy injectors. My question is, so I need to run the matching FPR or anything else to get the most out of the new injectors?



Thanks in advance:)

[jlevie]

I think the existing FPR should be fine.

[xLibelle]

are the m50 injectors DesignIII?
if not, how are they an upgrade in spray? (dont mention increased output)

[nando]

pretty sure they are design III but I've never seen a set in person

I think these are a better match to the stock motor than the 19#s everyone uses. Just make sure everything else is working correctly before you put them in, if you have vacuum leaks or broken/worn sensors the injectors are going to make things worse.

[nickpdx]

Nope, M20 FPR will be just fine. My car started running really lean (I was getting lots of detonation in mid-high RPMs) and I was more frequently getting that annoying condition when the engine was warm where I would have to crank the starter for 7-8 seconds before it would turn over - due to leaky injectors. I picked up a set of pretty clean 17.5lb M50 injectors from someone on here and didn't even bother rebuilding them (I'll have 19lbers and a Miller MAF before too long). They have made a huge difference in how smoothly my engine runs and idles, and my butt dyno seems to notice more power in the top end. After the ECU adjusted to them I haven't had any decreased gas mileage or rich-running.

Here's what my stock ones looked like after 151k original miles!

[nickpdx]

I'm not sure what design III means, but the green top M50 injectors have four spray holes.

[E30_fiend]

Design I's i.e. the ones that come stock on all M20s are a single pintle(sprayer) design. This equates to poor atomization of the fuel and ultimately bad gas mileage.

Design II's and Design III's are both a 4 pintle type injector. The spray pattern on the are drastically different than the spray pattern on the Design I's. Since the holes in the tip of the injector are much smaller and placed close together, the spray under correct pressure is more of a mist rather than a stream like Design I's.

The only noticable difference between Design II's and Design III's are the asthetics. The Design II's are the more common "fat" bodied injectors. The Design III's are a more rare "skinny" bodied injector. Its is about the same size as the o-ring all the way down.

It hasnt been set in whether or not the Design III's work as efficiently as the Design II's on the stock M20 motor but I have heard that the Design II's work better with the 20 year old technology that our cars have. That is the reason why I run the Design II's on my car and not the Design III's.


Hope that helps.

And to answer the OP's question, no you dont need to upgrade your FPR. It will do just fine with the 17.5#ers. Mine loves the 19#ers with a stock FPR.








Taylor

[E turd]

Great. Thanks a mint for all the help. I guess I'm off to find a set now!

[xLibelle]

thanks for clearing that up!

[nando]

It hasnt been set in whether or not the Design III's work as efficiently as the Design II's on the stock M20 motor but I have heard that the Design II's work better with the 20 year old technology that our cars have. That is the reason why I run the Design II's on my car and not the Design III's.

if they are both high-z injectors and the dead time characteristics are similar, there won't really be much difference.

[E30_fiend]

if they are both high-z injectors and the dead time characteristics are similar, there won't really be much difference.

true. I was responding entirely on hearsay. A few people on here have said some things about the injectors having some sort of electrical dificulties. I figure if our cars came with a certain injectors style, then thats all that I will put in there.







Taylor

[nando]

ours come with high-z, ~1.15ms opening time injectors. Pretty much all high-z injectors have about the same dead time (within .05ms or less), there's not really anything else electrical that could be different.

so basically, don't worry about it. ;)