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View Full Version : 21.5lb vs 24lb injectors...


JazzM
11-21-2003, 10:59 AM
What are the HP ranges for each of those?

I know that dinan stays with stock injectors on their N/A products and that goes up to around 275 hp, however Eurosport cam kit goes to 24lb injectors @ around 295 hp...

What is the maximum hp that the stock (21.5lb) injectors will sustain before risking to run lean?

Thanks,


T.
RRSperry
11-21-2003, 11:09 AM
The stock injectors are good to about 275-280 Hp. At that point, you run into duty cycle issues. The stock injectors are fine up to the point of adding the cams. If you track the car a lot, ie run at really high rpms, you may gain some margin of safty going to bigger injectors before adding the cams.
tybmw
11-21-2003, 11:15 AM
17# injector suck too!
RRSperry
11-21-2003, 11:27 AM
Exactly why would you say that? On the 95 S50US motor the 17# injectors are just fine, and the above facts apply as well.
stom_m3
11-21-2003, 11:45 AM
The 21.5# injectors run out of steam at about 245rwhp. I was able to get them to cut out at that level before switching to the 24#'s.
tybmw
11-21-2003, 11:48 AM
I doubt that the stock 17# injectors are rated for 285 hp, I've heared that they are barely sufficent for the stock set-up.
JazzM
11-21-2003, 11:50 AM
Thanks guys, much appreciated...

... so I'm assuming that the ECU will have to be re-tunned with the new injectors...

T.
Armo95
11-21-2003, 11:52 AM
Originally posted by JazzM
Thanks guys, much appreciated...

... so I'm assuming that the ECU will have to be re-tunned with the new injectors...

T.

Yes. I'm assuming you're going with a different intake system as well...you'll need to reprogram your chip so that it understands you're dumping more fuel and compensating with more air rushing in.
E30 Stu
11-21-2003, 11:59 AM
I run 17# injectors at 62psi (at WOT), and I love it. Killer throttle response, due to the vacuum drop.

Perhaps I am not making as much power as I could be, but I havn't dyno tuned it yet. I have 21.5's laying around, though I will probably wait until I get an AA custom chip before putting those in.
E30 Stu
11-21-2003, 11:59 AM
I run 17# injectors at 62psi (at WOT), and I love it. Killer throttle response, due to the vacuum drop.

Perhaps I am not making as much power as I could be, but I havn't dyno tuned it yet. I have 21.5's laying around, though I will probably wait until I get an AA custom chip before putting those in.
JazzM
11-21-2003, 11:59 AM
But if there's more air comming in, ie M50 manifold, cams, CAI and HFM doesn't that make up for having additonal more fuel...

... I guess generally speaking it does, but the tuning fine tunes everything...

Any benefit to going to OBD I? It seems like it's much easier to tune...

Thanks,

T.
Armo95
11-21-2003, 12:03 PM
Originally posted by JazzM
But if there's more air comming in, ie M50 manifold, cams, CAI and HFM doesn't that make up for having additonal more fuel...

... I guess generally speaking it does, but the tuning fine tunes everything...

Any benefit to going to OBD I? It seems like it's much easier to tune...

Thanks,

T.

Like I said, if you're going to run 24# injectors, I hope you're going to compensate it with more air coming in(HFM etc.). If not, you'll run rich and that's pointless. I don't see why you would want to run larger injectors on a stock motor.

Then comes dyno tuning your car to reach optimal gains and efficiency.

Benefits of OBDI? Too many to list, you can't go wrong and the power gains would be tremendous. It's the main reason I was interested in 95s ONLY.
Dinan330ic
11-21-2003, 01:05 PM
hmmmm, can you just add larger injectors and run an adjustable FPR to tune???

I have 245 rwhp with the 17# injectors.
Armo95
11-21-2003, 01:10 PM
Originally posted by Dinan330ic
hmmmm, can you just add larger injectors and run an adjustable FPR to tune???

I have 245 rwhp with the 17# injectors.


Sure, I don't see why not.

Wait...aren't you forced?
Dinan330ic
11-21-2003, 01:17 PM
Originally posted by arrag
Sure, I don't see why not.

Wait...aren't you forced?

yeah. I'm not too fond of Mechtech's tuning techniques.
Armo95
11-21-2003, 01:24 PM
I'd say...245rwhp is like an NA car.

Have you dyno tuned your car since you've had a turbo? Do you have a FPR?
Dinan330ic
11-21-2003, 01:26 PM
Dyno-tuning will be next Wednesday. I have two hours of dyno time.

245rwhp is untuned with stock injectors, stock software, and a RRFPR/FMU.

I'll be adding 30# injectors and AA software.

I didn't know whether software is absolutely necessary to run larger injectors. I just wanted to know.
Armo95
11-21-2003, 01:34 PM
Awesome, hey man, keep us updated(either here or on FI). I'm actually going to FI myself...

I'll be looking forward to your thread and seeing your results with injectors and software. Good Luck!
DocWyte
11-21-2003, 01:36 PM
You have 245whp on a 3l M3 engine AND a turbo?! So you picked up 20-25whp from the turbo system?

That's just totally wrong. Your car must be running either horribly rich or horribly lean...
Armo95
11-21-2003, 01:44 PM
Originally posted by DocWyte
You have 245whp on a 3l M3 engine AND a turbo?! So you picked up 20-25whp from the turbo system?

That's just totally wrong. Your car must be running either horribly rich or horribly lean...


In his case, probably VERY lean because of the stock injectors.
Dinan330ic
11-21-2003, 03:15 PM
yeah, it's very lean. Detonating all over the place. The 245rwhp isn't even accurate. It was the highest "arch" the graph made =\

The turbo is only running 7psi of boost.
DocWyte
11-21-2003, 06:00 PM
I hope you're not driving it...
Dinan330ic
11-21-2003, 06:05 PM
Originally posted by DocWyte
I hope you're not driving it...

Nope, haven't driven it in three months. Haven't even driven 100 miles on it.

I'm in Boston right now for school. Driving my beater (94 325i).
Armo95
11-21-2003, 07:08 PM
Well hey man, good luck and again, let us know how it turns out...can't wait to hear results.
UserName
11-21-2003, 09:29 PM
I've got 239@wheels on stock 17#s
RRSperry
11-22-2003, 09:17 AM
Originally posted by arrag
Like I said, if you're going to run 24# injectors, I hope you're going to compensate it with more air coming in(HFM etc.). If not, you'll run rich and that's pointless. I don't see why you would want to run larger injectors on a stock motor.


WHAT? Are you sure you know what you are talking about? The flow rate of the injector is expressed as # of pounds of fuel deliverd per hour at an 80% duty cycle. Provided you have a chip the is properly set up for the injectors, then HFM, CAI... really doesnt matter.

The ECM reads the input sensors, like HFM output, TPS,... and reads the map. it then fires the injector pulse width for the given parameters.

You run into problems when the chip, or ECU flash isn't correct for the given injectors or other sensors.
paul e
11-22-2003, 11:03 AM
>>You have 245whp on a 3l M3 engine AND a turbo?! So you picked up 20-25whp from the turbo system?<<

I thought most stock e36 m3s made around 200-205 sae rwhp on the dynojet.
Croak
11-22-2003, 01:04 PM
True, but he was putting out low 220's with his NA mods before the turbo install, so his net gain is pretty low.

I think he's going to be a happier camper when he gets his fueling and timing sorted out and has his HFM in the "proper" location.
Armo95
11-22-2003, 07:47 PM
Originally posted by RRSperry
WHAT? Are you sure you know what you are talking about? The flow rate of the injector is expressed as # of pounds of fuel deliverd per hour at an 80% duty cycle. Provided you have a chip the is properly set up for the injectors, then HFM, CAI... really doesnt matter.

The ECM reads the input sensors, like HFM output, TPS,... and reads the map. it then fires the injector pulse width for the given parameters.

You run into problems when the chip, or ECU flash isn't correct for the given injectors or other sensors.

Actually I do...what I meant was, who the hell would want to run 24# injectors on a stock car? I sure as hell wouldn't...