2.7i injectors

[Jargo]

I have just completed building a m20 2.7i stroker using a s-eta bottom and complete "i" top end. I will be using a MarkD 93 oct 17-19lb chip, but I am having trouble deciding which injectors to put in the motor. I am trying to choose between 0 280 150 415 (m50 17.5lb) and 0 280 150 440 (m52 21.5lb) which I found for free. I've been researching flow rates on Witchhunter Performance (http://www.witchhunter.com/injectordata1.php4). The 17.5lb flows at 166cc and the 21.5lb flows at 208cc which is actually a typical flow of a 19lb. For example a 0 280 155 746 is a 19lb type III that flows 208cc as well and I know a lot of guys are running these.

My goal for this motor is maximum performance without sacrificing fuel economy. It is otherwise stock. My question is; would the 208cc injectors be overkill and ruin my fuel economy? Keeping in mind that the bigger ones were free and the others I'd have to purchase, which injectors would you recommend?

[eta]

Why would bigger riun your fuel economy? If the ECU is programmed correctly and the maintains the correct AFR then no extra fuel would be injected. The injectors would just run at a lower duty cycle. Fuel flow rates through injectors will depend on the fuel pressure that is used during the test. I have seen 2.5 bar, 3 bar and more for flow rate measurements. Are you sure you are comparing like with like? Decides here in the UK it is common for 2.7i builds to retain the stock 325i "715" injectors and they work fine. I have tham in my motor, no problems except for the AFR issue above 4800 rpm caused by an off the self chip.

[lennon]

good job using s-eta bottom end instead of these idiots that just put 885 heads on regular e blocks. i had a bit more radical 2.7 in my car, used the same Mark D chip and m50 17.5lb injectors. in my opinion you do not need more than that on the 2.7. i don't think either is gonna kill your fuel economy much. if you search you can almost certainly find dyno's/info on 2.7 m20s with different injectors. sorry i dont have a dyno or anything.

[Jargo]

See that's kinda what I thought too, that 17.5lb was plenty and that more was overkill. But since the DME will just adjust for the bigger ones anyway, and they were free, maybe I'll just use them and see how it goes. Wouldn't be that hard to swap smaller ones in later on anyway.

[thereisnoyun]

I'm pretty sure if you run super large injectors your range for cold start will greatly diminish and you will see cold start problems. So, the dme adjusting is kind of tru,e but not entirely.

[Jargo]

Interesting. However the injectors I have really aren't that large, they flow similarly to 19lbers that many people are using. I just put them in today, hopefully I'll have the engine running soon and I can let you know how they are.

[thereisnoyun]

Interesting. However the injectors I have really aren't that large, they flow similarly to 19lbers that many people are using. I just put them in today, hopefully I'll have the engine running soon and I can let you know how they are.

the m50 17.5 is tested and true injectors that works. You wont have any problems with that.

[nando]

I'm pretty sure if you run super large injectors your range for cold start will greatly diminish and you will see cold start problems. So, the dme adjusting is kind of tru,e but not entirely.

what? I'm pretty sure you're just guessing.

it won't have any effect on cold start. None, zero, ziltch.

there are two fuel trims. one short term (real time EGO correction, at cruise and idle), and one long term. The long term fuel trim affects the final pulsewidth no matter what the load or RPM of the engine, including cold starts.

if your EGO system is screwed (most E30s are) or if you dick around with shit like M30 AFMs and RRFPRs, THEN you will have problems.

[digger]

what? I'm pretty sure you're just guessing.

it won't have any effect on cold start. None, zero, ziltch.

there are two fuel trims. one short term (real time EGO correction, at cruise and idle), and one long term. The long term fuel trim affects the final pulsewidth no matter what the load or RPM of the engine, including cold starts.

if your EGO system is screwed (most E30s are) or if you dick around with shit like M30 AFMs and RRFPRs, THEN you will have problems.

the issue is how good is the "longterm" trim and how much can it cater for......use injectors that are correctly matched to what you need.

[nando]

17-19# injectors are well within it's range

I ran 19# injectors for years on an otherwise stock motor, never had cold start issues, poor mpg issues, check engine light issues, etc.

[eta]

885 head matched to stock eta bottom end (the U.K 10.2:1 kind) works very well lemon. Many people of Mye28 have gone down this route using the lower CR U.S engine with an 885 head and they report good results. It's not lunacy if its what you have got to hand. Granted a seta block will give better results.

[thereisnoyun]

what? I'm pretty sure you're just guessing.

yes, well I have no actual experience, so you are right.

now, I read some basic injector literature, and it says that it would cause unstable idle, and

"larger injectors may take longer to open. This can cause unstable idle, since the ECU cannot accurately meter very small quantities of fuel."

other than that... i'm still running stockers. I stand corrected and would like to know why you wouldnt use more fuel either. It seems like a widely accepted theory that 19lbers would use more fuel even on r3v.

base one what you say, most e30 ego are messed up already, I'm assuming this is the o2 sensor signal? I know no other exhaust oxygen sensor.

[lennon]

885 head matched to stock eta bottom end (the U.K 10.2:1 kind) works very well lemon. Many people of Mye28 have gone down this route using the lower CR U.S engine with an 885 head and they report good results. It's not lunacy if its what you have got to hand. Granted a seta block will give better results.

hey buddy i wasnt referring to high-compression eta bottom ends we didnt get here in the USA. if you have an m20b25 and wanna put the head on a US m20b27, be my guest i dont really care. obviously the high compression block would work better but there's issues there. i already built one with 11:1 eta pistons, youre not schooling me on any new info with your secondhand mye28 "reports" on 2.7i's.

by the way, you should be able to say my name, LENNON. the great John Lennon was from your land.

edit- and way to take this off topic into a eta block + 885 head argument. im thru arguing over that shit anyways but theres better places for it than this guys injector thread.

[nando]

yes, well I have no actual experience, so you are right.

now, I read some basic injector literature, and it says that it would cause unstable idle, and

"larger injectors may take longer to open. This can cause unstable idle, since the ECU cannot accurately meter very small quantities of fuel."

other than that... i'm still running stockers. I stand corrected and would like to know why you wouldnt use more fuel either. It seems like a widely accepted theory that 19lbers would use more fuel even on r3v.

base one what you say, most e30 ego are messed up already, I'm assuming this is the o2 sensor signal? I know no other exhaust oxygen sensor.

the difference in opening time will be negligible. like, maybe .01ms. typical injector opening time on a high-z injector is around 1.1ms. the difference between the opening time of stock injectors and say, ford 19# injectors is vasty dwarfed by the extra fuel.

also, you misunderstood what you were reading anyway. yes, large injectors can cause an unstable idle, but not because of the difference in opening time. since most high-z injectors are going to have somewhere around 1.1ms for an opening time, and because some very large injectors will require a very small PW at idle, you can end up with an idle PW that's too close to the opening time. Flow becomes non-linear and you can't control them very well at this point.

however, 19# injectors are *so* far away from that point on a stock M20, you will never have that problem. 19# injectors will have an opening time of around 4ms, stock will be maybe 5-6ms. 3ms of actual fuel flow is plenty vs 1.1ms of opening time. you can easily get away with .5ms of fuel flow and not have troubles - but you'd need like 50-60lb injectors to get to that point.

right now with 42# injectors in batch fire my idle PW is 2.1-2.2ms. these are way bigger than stock, and although my engine isn't quite stock the differences at idle are pretty small.

the reason they wouldn't use more fuel is because if 14.5# inectors require a 10ms PW to get stoich at cruise, and you put 19# injectors in, the computer is going to dial back the size of the PW until it reaches stoich. after a while it will begin to adjust the long term trim (which is GLOBAL) until it no longer needs to use as much short term trim to reach the target.

lots of people say lots of BS on r3v, that doesn't mean any of it is true. ;)

and what I meant about most E30's being messed up is poor maintenance and plain worn out shit. Just look at how many poor starts, bad idle, cutting out, etc etc. threads are started all the time in the M20 section. If you take an engine like that and put bigger injectors in, it's only going to make it worse. It's no wonder why there is so much BS on this subject.

these engines aren't complicated and neither is the engine management. You only really need three signals for it to run halfway decent (coolant temp, afm, and crank pulse). Everything else is just to make it smoother, faster and more fuel efficient.

[Luis325]

I just did my 2.7i and have the 17.5 injectors with a Mark D chip and it runs Great!!!!