Mark D and 19# on stock car?

[essi1553]

My excuses:
Yea i know its been said before honestly im in a time crunch and dont want to make another 4 hours drive for a chip and injectors. Working tonight cant search all night either.

Are 19# injectors overkill (will harm my car), with the use of a mark d chip (that requires the use of 17.5# or 19# injectors) on an otherwise stock car?

Thank you.

[Shanes325]

Your car will be perfectly fine . On another hand,When I had this question forever ago. useing the search function helps a lot and I found my answer in like 10 min .

[essi1553]

Thank you, I seriously tried, if you see my bookmarks, im literally overstuffed with pages i refer to for info. I appreciate it, I know I have the guy who sells tested ones with a loy of info in that thread but I couldn't find it!

The capatcha thing always drives me crazy, and I tried using it and google. Forgive my impatience.

[squidmaster]

Your car will NOT be perfectly fine. The o2 fuel trim will not adjust for a >20% larger injector. Especially since most of the tuner chips up the fueling a bit on the maps. You have to decrease it.

[custom e30]

your car will be fine!!! it will have better throttle response, give a small bit more power, and run smoother, before i turbo charged my car i had this set up

$40 eBay performance chip

19lb injectors

3.73 lsd

headers with custom exhaust all the way back, no cat

cold air intake

short shifter

the stock n/a e30 had 170 hp right? my car had 202 hp to the wheel on the dyno after i did all this

[ak-]

You're m20 car made a hair under stock s52 power?
I think you're confused somewhere.

[Killacortes]

You're m20 car made a hair under stock s52 power?
I think you're confused somewhere.

truth

[squidmaster]

Yeah you're going from a 154cc/min injector to a 200cc/min injector. It's not going to work. Especially if you're using a type II or 4-outlet design injector. Too much flow, not enough pressure = a stream and lack of vaporization = lack of power and decreased gas mileage.

The o2 will only correct maps via a fuel trim stored to ram, and it will ignore o2 corrections under WOT.

This is coming from someone that has 19# injectors and has tuned for them. So.

[digger]

ive used big injectors on a stock engine and it works fine, obviously not ideal especially if one wants to optimise the tune......i would have though MArk tweaked things to offer a 19lb chip.

after a while even the WOT maps get corrected somewhat based on data the O2 sensor feedsback not like a modern ECU but.......

[squidmaster]

Actually the engine reads O2, engine temp, and afm below 74%, an only engine temp and afm after 75%.

The o2 sensor will allow writing of short term fuel trims and long term fuel trims (STFT and LTFT) for basic corrections. Usually these don't venture outside of a 5% difference from what I've been able to tell. The trim maps are, from every thing I've seen while tuning, completely ignored under WOT. I'm willing to bet that you're running rich, getting late combustion, causing piston detonation, and siphoning your power and mpg.

not only do 19# injectors have a different lag time per volt, but they also pulse slower and throw in way too much fuel. These factors, and a few more, play very negatively toward your engine.

Especially when you go with an after market chip, as I've said, which almost always have a higher fueling map, which is the complete opposite of what you want.

Do you have a wideband? What about even an ARF gauge? It may run, but not well or correctly.

[nando]

The o2 will only correct maps via a fuel trim stored to ram, and it will ignore o2 corrections under WOT.

this is absolutely wrong. All motronic systems with O2 feedback loops have a long term trim as well as a short term trim, and long term trims apply everywhere.

Ask the SpecE30 guys about it - they have found ways to trick the stock DME into running a little richer, but the O2 feedback always dials it back to stock (they end up resetting the DME between runs by unplugging it for a few minutes). Also, I have loads of documentation from Bosch that says otherwise. ;)

I can't believe this is even still a debate. I ran 19# injectors on a stock motor a decade ago and never had any problems with it running poorly, running rich, or "fuel dribbling out". utter nonsense.

However, it assumes the engine already runs well and is maintained properly with working sensors. Also, there's basically nothing to gain from it, although the newer injectors will be much quieter.

[squidmaster]

^Citation needed

Have you heard of open loops and closed loops? Might want to google that.

[nando]

ask jlevie

as far as the bosch docs, I'd have to dig them up.

[squidmaster]

Here's some great info on the bosch motronic o2 sensor system. As you can obviously tell, the o2 is ONLY read under closed loop.

http://the944.com/lambda.htm

[nando]

yes, *real time* o2 feedback is only used in closed loop. But, there's also the long term trim, which isn't real time, and it's permanently stored in the DME's memory (in the case of the E30, as long as you don't unplug it). the long term trim applies everywhere.