17# or 19# Injectors?

[Roque]

Hi everyone!!!

I'm planning to track my 1990 E30 and for some reason added a set of 17# or 19# injectors in the mod list. Heard a rumor that M20's tends to run lean at high rpm's... is that correct? Any data logged available?

If NOT, why Mark D chips comes for those specific injector sizes?

If is good to run bigger injectors, what brand and model is recommended?


Same thread discussion here.

[MR 325]

I have a stock motor with 17lb M50 injectors, M30 AFM, and a chip. It runs awesome with this setup and is worlds better than before I did it. I am also planning a cam for it at some point in time.

[nando]

please don't get a regrind, ESPECIALLY one from IE. if you want an inexpensive cam, at least get one from Catcams...

[whowhatwhere]

My engine goes just as fast with stock injectors as with 17 pound injectors.

[g22]

I had the IE regrind and did not like it. I'll sell you mine if you want it.

I'm running 17.5 M50 injectors, bored throttle body, Turner chip and a lightened flywheel and absolutely love the responsiveness of the motor...

[MR 325]

I had the IE regrind and did not like it. I'll sell you mine if you want it.

Why didn't you like it?

[g22]

Just didn't feel like I got any extra hp on the butt dyno and since that was my first IE part and after than everything else i bought from them turned out to be crap...

[RobertK]

Just didn't feel like I got any extra hp on the butt dyno and since that was my first IE part and after than everything else i bought from them turned out to be crap...

Different cam setups aren't really intended to increase your HP as much as they are meant to adjust your torque curve.

[nando]

Different cam setups aren't really intended to increase your HP as much as they are meant to adjust your torque curve.

this just isn't true. a good cam will allow more air into your engine, more air + more fuel = more power.

also, a cam doesn't mean you're going to lose all your bottom end. just another myth..

[AndrewBird]

this just isn't true. a good cam will allow more air into your engine, more air + more fuel = more power.

also, a cam doesn't mean you're going to lose all your bottom end. just another myth..

Exactly. A cam will more give you more top end and not as much bottom end (generally speaking), but it won't take away low end power (once again, speaking generally).

I would also agree on not getting a regrind. Get a new billet or don't get one at all. Regrinds just aren't worth it.

[digger]

this just isn't true. a good cam will allow more air into your engine, more air + more fuel = more power.

also, a cam doesn't mean you're going to lose all your bottom end. just another myth..

usually a hotter cam will let more air in at mid to higher rpms creating more torque and hence power at mid to high rpms.

Not all cams will kill the bottom end but some will and this is definitely not a myth. It really depends primarily on the intake valve closing position (number of degrees after BDC) which determines dynamic compression, overlap also causes low end loss as fresh air is mixed with burnt exhaust gas meaning you get less oxygen and the charge can be often drawn straight form the intake valve to the exhaust via scavenging (low pressure pulses in exhaust). Dynamic compression goes along way to giving volumetric efficiency (i.e. torque) and is important when the air velocity is low at low rpm as air is pushed back out the intake valve. The reason for vanos is the delay the closing of the intake valve (retard it) at high speed and advance it at low speed to produce a greater spread of torque

One of the reasons for increasing the static CR with hot cams is so there is still reasonable dynamic compression as hotter cams lose dynamic compression. Another reason why running high CR with stock cams produces End Gas Autoignition (detonation) as the dynamic compression is too high for the fuel used. This is the reason static CR go hand in hand with the cam and why a poorly chosen cam can limit the operating range of an engine

Nando if you were to put back in your stock cam i am almost certain that below 2000rpm it would produce more torque.......not a whole lot more since the Schrick 284/272 is not a particularly hot cam compared to some others.

[digger]

A properly chosen regrind is ok (i know people with regrinds that are excellent) provided they treat it properly. If you aren't required to use bigger eccentrics its probably not a worthwhile cam as only when you use bigger eccentrics can you get more lift from a regrind because the base circle needs to be ground for more lift (remember that lift is not determined by the height of the nose its the difference between the nose and base circle)

[nando]

that's the problem, the regrind IE makes are not good quality. :p

Maybe it would make more torque with a stock cam, but it would be insignificant I'm sure. and right now at 2000rpm I make about 185ft-lbs at the crank, which is more than a stock M20 makes peak by a long shot. I'm not really worried if I'm missing 2 ft-lbs of potential. ;)

[digger]

that's the problem, the regrind IE makes are not good quality. :p

Maybe it would make more torque with a stock cam, but it would be insignificant I'm sure. and right now at 2000rpm I make about 185ft-lbs at the crank, which is more than a stock M20 makes peak by a long shot. I'm not really worried if I'm missing 2 ft-lbs of potential. ;)

But yours is a 2.7 so thats not really fair now is it.....lol.
Have you had it on the dyno? Can you post it up if you have as there aren't many ix graphs around.