mark d chip? injectors needed

[nando]

After doing a bit of searching it looks like it's more about injector design than injector size. Single pintle stock injectors have a crappy spray pattern and are probably old and clogged after 20 years of use not to mention intrinsically noisy, 17.5lb/hr M50/S50 injectors as well as 19lb/hr mustang injectors are 4 pintle (more efficient spray pattern), quieter and newer. That about sum it up?

yep! although the factory injectors are pretty well maxed out once you put a chip in there. you can get around that though by running more fuel pressure.

[MN325ix]

yah i saw info about the 4 pintle are better. Thats what im getting with my 19lb and chip thanks for the info

[MN325ix]

so with getting the 19lb 91 octane mark d chip i wont need to get anything else? just the injectors and chip?

[Wh33lhop]

You'll need tools to install them.

[MN325ix]

lol duh!!! thanks wh33lhop for the great info

[Wh33lhop]

lol duh!!! thanks wh33lhop for the great info

Hey, you asked. ;)

Be careful when you remove the stock EEPROM (stock chip).

[Wh33lhop]

yep! although the factory injectors are pretty well maxed out once you put a chip in there. you can get around that though by running more fuel pressure.

Funny, I always thought stock M20s ran rich towards redline seeing the plume of smoke I leave behind when I really rail on it.

Or is this because of the higher redline (moar revs means moar duty cycle)?

[E30Idea]

Are the 19lb/hour mustang injectors high impeadance? This is what we need right?

[nando]

Funny, I always thought stock M20s ran rich towards redline seeing the plume of smoke I leave behind when I really rail on it.

Or is this because of the higher redline (moar revs means moar duty cycle)?

actually, it can work both ways. there is a maximum duty cycle you can hit (er, 100%), and when that happens there really is no control over the flow of fuel out of the injectors, and depending on the condition of your FPR (if it's failed it will run rich regardless) you could end up dumping fuel like you experienced, or if 100% still isn't enough fuel you could run lean.

basically near the fringes of an injector's cyle range (10% and 90%) the flow rate becomes non-linear (taking injector opening times into account). Stock injectors on a stock engine run at like 80%, so add mods and a chip to that and it's not going to be pretty. Ideally, you want to keep it around ~75-80% for the most efficiency. I had my 19's pegged at 90% and ended up swapping them out for something a little bigger.

and of course, single pintle injectors have a horrible spray pattern.

[nando]

Are the 19lb/hour mustang injectors high impeadance? This is what we need right?

yes, and yes.

[xLibelle]

MN325ix, there are a few sets of the injectors you are looking for on ebay right now, *cough*170329427303*cough* ...this is an example of bottom of the stack, something to really keep your eye on and theres a set for like $70 Buy Now and those are a good deal too. Then there are the $169 sets... i dont know what these sellers are thinking, are people spending that much on injectors that normally go for $50-$80 per set of 8???

I have a set on another e30 thats just sitting there, but i'm too lazy to go pull them so i just bought another set.

[Wh33lhop]

actually, it can work both ways. there is a maximum duty cycle you can hit (er, 100%), and when that happens there really is no control over the flow of fuel out of the injectors, and depending on the condition of your FPR (if it's failed it will run rich regardless) you could end up dumping fuel like you experienced, or if 100% still isn't enough fuel you could run lean.

Well I also need a new O2 sensor. IIRC as they take a dump they tend to read lean, causing it to run rich, and making me poor. On a related note, recently I've noticed the car feels a lot slower towards redline, it'll pick up at 4k like normal and fall flat on its face around 5--I'm thinking either it's running really rich because of the O2 sensor (less likely) or my fuel pump or filter needs replacement.

basically near the fringes of an injector's cyle range (10% and 90%) the flow rate becomes non-linear (taking injector opening times into account).

What would 90%+ have to do with opening delay? I'd think that it would be linear from 10% up.

What I was saying that as the revs climb the intake valve will be open for shorter and you will need a higher duty cycle to maintain the same injector pulse width. With that logic, another 400rpm over 6500 could add a good 8% duty cycle..

Stock injectors on a stock engine run at like 80%, so add mods and a chip to that and it's not going to be pretty. Ideally, you want to keep it around ~75-80% for the most efficiency. I had my 19's pegged at 90% and ended up swapping them out for something a little bigger.

What all were you running to saturate the 19s?

[nando]

What would 90%+ have to do with opening delay? I'd think that it would be linear from 10% up.

because injectors are *not* linear. The opening time as a percent of the overall pulsewidth makes it that way. At some point your injectors basically stay open, but the computer is always adding an injector opening time correction to the overall pulsewidth, even if they aren't really closing, or the computer is commanding them to close for a shorter period than the injector reaction time (typically 1-1.3ms on a high-z injector). See what I'm getting at here?

What I was saying that as the revs climb the intake valve will be open for shorter and you will need a higher duty cycle to maintain the same injector pulse width. With that logic, another 400rpm over 6500 could add a good 8% duty cycle..

Yes it does exactly that. But if stock injectors are already at 80% (within their efficiency range), and now you've pushed them 8-10% beyond that and you can no longer accurately meter fuel through them, what happens?

Also, because you are flowing more air (assuming other mods, like higher displacement, cams, chip, etc) you have to flow more fuel on top of having a higher RPM, pushing them even further beyond their efficiency. Like I said though, you can get around this by adding fuel pressure, but the single pintle design is garbage so that's even a little pointless.

What all were you running to saturate the 19s?

just a basic 2.8 stroker. but even 19# are only really good for about 190-200hp on an M20 because it's not a super efficient motor (BFSC). A 21# or 24# would be better suited to me, but I got a deal on some 42# that gives me a lot more room to grow. I could have bumped up the fuel pressure instead but that doesn't work forever. :)

[MN325ix]

thanks for the info.