3.4 L32 V6/60... questions... compared to L44 (Page 6/9)
82-T/A [At Work] MAY 22, 08:00 PM

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Originally posted by sleek fiero:

82-T/A yes the 3050 Crower will work with 9.0 or better CR. I would order it with the matching components, springs and lifters. If possible get the lifters with the Groove down the side to provide more oil to the cam lobes. also if your engine doesn't come with a high volume oil pump I would change that up as well.



RGR, thanks. Yeah... I've already ordered the high-flow oil pump... will definitely be using it... no reason not to! Thanks!



quote
Originally posted by lou_dias:

Please recall, when I say 'block' I mean just the short-block. I resell the aluminum heads to AL head zealots who are replacing their warped heads for basically what I paid for these dime-a-dozen junkyard motors. Then I get the short-block rebuilt with 3.4 pushrod or 3.4 TDC pistons depending on if it's a street motor or not.
I considered using LFX 3.6 pistons in my current 3.500+ build but used custom ones instead.

The 3.6 [LFX] uses the 3.37" stroke over the 3.31" stroke to achieve 3.6L using pistons that would normally get you 3.5L (97mm/3.7" diameter)...

...this is all with Fiero IRON heads.

Oh gee...I wonder what length rods the 3.6 uses...and what length I'm using...
https://molnarrods.com/gm-lfx-connecting-rods




Honestly... it's kind of crazy. When I bought the 3.4, it said that I would get it until August, so I was like... ok, great... I can buy and forget. I got a call later today stating that they want to schedule the delivery, and I'm like... **** ... what? It's getting dropped off at some point betwen 0900 and 1700 on Wednesday. LOL...

But yeah, I bought the entire long block. I'll still have to drill and tap for the starter, and also remove the heads so I can clean them up, etc... but my goal is mostly reliability. Reliability ---> Originality ---> Performance ---> Cost. In that order.


I had a 1984 Porsche 944 5-Speed a little over a decade ago. I really do miss that car. That's a car that I really think needs a smooth running engine. I never did like the Porsche 2.5L 4 cyl. The Porsche people of course think it's an amazing engine, they talk about it having two balance shafts going counter to the rotation of the rest of teh assembly to defer negative torque effects. But honestly, it's just a Porsche 5.0 with one side lopped off. It's not the best... it's really a slant-4, and I've always felt like the V6/60 is a perfect motor for there.

For many years, I'd have a Pontiac Grand Am as a rental car... the one with the 3400 V6/60, and I always loved how smooth that engine was. It pulled hard in that big plastic-clad 4-door sedan of a Grand Am, and enjoyed the noise it made. I never liked the turbo in the Porsche 944s... and I just think a 60 degree engine (with those harmonics) is really what the 944 should have had, something like that. So... I absolutely plan to buy another 944 and swap in a 3400 or 3500. I don't want any of that barn-door Jetronic-K BS stuff.
pmbrunelle MAY 22, 10:30 PM

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Originally posted by 82-T/A [At Work]:
Yeah... definitely the upper-rpms is a problem. Back when my engine was stock, I noticed a significant difference EVEN just replacing the stock ignition coil with a higher output one. I haven't put much thought into it, but the assumption here is that the factory coil couldn't build power quickly enough to supply the ignition at those RPMs. It's never an issue for things like V8s and what have you, because they simply don't require that kind of rpm. If you look at some of the more high-end performance engines of the 60s through early 80s, they even had multiple ignition coils (sometimes a bank of plugs supported by one coil) in order to properly support the ignition.

But... back in the late 90s when I replaced the factory coil with an Accel (I even painted it black to look stock), I immediately noticed better performance in the upper RPMs... felt like it pulled harder. I hope to actually solve this problem with the use of the MSD 6EFI.



Variations in engine power with spark energy is not something I understand.

It seems to me like an ignition system either works or it doesn't; if the mixture catches fire on every cycle, then that should be good enough.

For an engine power increase to have occurred, are you implying that the factory Fiero coil was failing to ignite the mixture on every cycle? If not, via what mechanism did the Accel coil improve performance?

[This message has been edited by pmbrunelle (edited 05-22-2023).]

zkhennings MAY 23, 01:00 AM
I assume weak spark due to the coil failing to energize fully would lead to power breaking up at higher RPMs due to either weak spark acting like retarded ignition due to slower/poor flame propagation or general misfires on random cylinders.

In my dyno of my 2.8 (earlier in this thread) up to 6000 RPMs the power gets wavy at the top. I think this was probably mainly due to valve float but I imagine you would see something similar if the coil can't handle what is being asked of it.

The 2.8 was probably designed for a 5500rpm max when stock and was running out of breathe well before then.

The Accel coil may be designed for faster charge/discharge (speculating) I am not an EE though so I won't pretend to be.

[This message has been edited by zkhennings (edited 05-23-2023).]

82-T/A [At Work] MAY 23, 10:13 AM

quote
Originally posted by pmbrunelle:


Variations in engine power with spark energy is not something I understand.

It seems to me like an ignition system either works or it doesn't; if the mixture catches fire on every cycle, then that should be good enough.

For an engine power increase to have occurred, are you implying that the factory Fiero coil was failing to ignite the mixture on every cycle? If not, via what mechanism did the Accel coil improve performance?





Like zkhennings said, I too am not an EE... I've got a CS degree, and a law degree, neither of which is helpful for understanding the principles of an ignition coil. On that, for some reason, I never had the opportunity to take Circuits 101 in college either.

There seems to be a narrative that a "weak spark" produces less power ... at the very least, it seems fairly universally believed (right or wrong). If that is incorrect, then the assumption must be made that any spark, no matter how strong or week, is essentially more than adequate to ignite the combustion mixture. I also understand that an engine can still combust simply as a result of heat and compression... as such with a diesel engine that doesn't have spark plugs. Incidentally, when you have a gas engine that "diesels" ... the engine is still running because the carburetor is either emptying the float, or the movement of the engine continues to power the mechanical fuel pump which feeds the carburetor, even though the ignition has been turned off. This would be evidential that an engine does not necessarily require ignition to fire under specific conditions, but we widely accept a "gas engine" won't run without an ignition system.

When I was younger, and far more dumb than I am now, I bought all the silly things to upgrade my Fiero. A side scoop, the "Tornado Air" because the Fiero Store sold it (haha), and even the Accel ignition coil. While almost all of these made absolutely no difference in performance... the Accel coil did. My car had 75k miles on it at the time, and was ~10 years old at that point, so I have to assume the factory coil was at least still decent.

Where I noticed the difference was in the upper RPMs. Normal power range was totally unchanged... but in the upper RPMs, the power felt like it continued to pull strong, longer. My assumption here has been that the factory coil simply cannot produce the actual power needed at the rapid pace that the higher RPMs are requiring... and the increased capacity that the Accel (or MSD, or any of the other aftermarket coils) are able to produce, allows a higher voltage / stronger park in the upper RPMs. I'm not believing that I'm getting 40k of volts at 6,500 rpms... but maybe I'm getting 20k. I can't remember what the stock ignition coil puts out... 25k or 30k, I can't remember. But at that same RPM, maybe it's only producing half of that.


I have to assume there is some point to this though, otherwise we'd never have gone to dual ignition, and then DIS ignition, and then CoP ignition, for which each is iteratively better ... with the goal getting a hotter spark, more quickly and directly to the source of ignition.


EDIT: It is a frustration for me because I know DIS ignition would be significantly better. Most modern cars today use COP by default. But going with DIS ignition would just be so much better than the old-ass coil that I have. But, I'm solving that with the MSD 6EFI. In addition to a higher-voltage coil, it also fires rapidly... hence the "multiple spark discharge." While I still think a DIS would be better than a coil, and a multiple-spark on a DIS would be even better, the multi-spark on a hotter coil is going to be my best bet while still looking stock. I just need to find a place where I can hide my MSD box (it's black, so it shouldn't stand out too badly).

[This message has been edited by 82-T/A [At Work] (edited 05-23-2023).]

82-T/A [At Work] MAY 23, 11:58 AM
Also, don't know if I mentioned, but the engine is arriving literally tomorrow... which kind of sucks because I wasn't expecting it until late August.

Good news though, is that I'm going to take the opportunity to build it out a little bit, and I'll have my daughter help. That way, the engine will be ready to go by the time I get my car out of storage.
zkhennings MAY 23, 03:41 PM
I think it is awesome you are getting your daughter into cars and got her a Fiero. Mad respect. If I ever have a daughter she is certainly at least going to get exposed to turning wrenches, and hopefully she is into it.
82-T/A [At Work] MAY 23, 05:20 PM

quote
Originally posted by zkhennings:

I think it is awesome you are getting your daughter into cars and got her a Fiero. Mad respect. If I ever have a daughter she is certainly at least going to get exposed to turning wrenches, and hopefully she is into it.




Yeah, I thought about it for a while when she was younger... always told myself I would do it. And then I realized one day... she's 14 years old. I have maybe 4 years left with her, and she'll be legally allowed to drive by herself in 2 years so... it's now or never, so I just decided I was going to do it. She actually really likes it too, and gives her a sense of pride that she's doing something that (probably) not a single other kid in her school knows how to do, let alone another girl.
pmbrunelle MAY 23, 09:30 PM
An inductive ignition coil needs to be designed such that its L/R (Inductance/Resistance) time constant is somewhat less than the interval between spark plug firings.

With applied voltage, the ignition coil current increases over time, until it asymptotically approaches a value which is determined by R. This can be considered as a first-order linear system.

By increasing the inductance, more magnetic energy is stored in the coil for a given current, however, the greater the inductance, the longer it takes to charge. So there is a tradeoff...

Ultimately, you reach a performance limit with a given mass of iron/copper, so within the stock form factor, you can only adjust the RPM vs. energy tradeoff.

For information, ignition coils supply an electric current to the spark plug when fired, not a defined voltage. The voltage is a function of the electric current, and resistance of the wires/gaps.

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I think that distributors were phased out due to a desire to simplify the mechanical aspect, remove the need for timing adjustment, and the need to measure engine position at the crankshaft.

Crankshaft position (without the slack of gears/chains) allows for a more accurate spark, so potentially more optimized spark timing, without risk of over-advancing and knock. So this was a way to gain efficiency.

OBD2 added the requirement of detecting misfires; accurately measuring crankshaft position and double-differentiating it allows the computer to detect torque variations from misfires.

This brought us to wasted-spark coil packs + crankshaft position sensors.

Later on, the EPA required that cars maintain good emissions performance without maintenance for a long time. Spark plug wires (a maintenance item) had to go, which brings us to COP.

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quote
Originally posted by 82-T/A [At Work]:
There seems to be a narrative that a "weak spark" produces less power ... at the very least, it seems fairly universally believed (right or wrong).



I find that "weak spark" idea smells bullshitty. The automotive modification world seems rife with myths, so I'm cautious when I read stuff like this.


quote
Originally posted by 82-T/A [At Work]:
If that is incorrect, then the assumption must be made that any spark, no matter how strong or week, is essentially more than adequate to ignite the combustion mixture.



Yes, that is my hypothesis, as long as the spark is strong enough to light the fire.

Once the initial spark occurs, the flame grows like an onion; a layer of mixture on fire causes the next surrounding onion layer to catch fire, and so on, until the limits of the combustion chamber are reached.

I think that more spark energy can cause the flame kernel's initial size at the instant of ignition to be larger. If you give the a smaller spark a bit more timing advance, then I think the onion can grow to the same size at the same instant as the larger flame kernel from a bigger spark.


quote
Originally posted by zkhennings:
I assume weak spark due to the coil failing to energize fully would lead to power breaking up at higher RPMs due to either weak spark acting like retarded ignition due to slower/poor flame propagation or general misfires on random cylinders.



I think that once the onion of a certain size gets going, whether it came to exist from a large spark, or from a smaller kernel that grew, doesn't matter. This is intuitively what I understand, but I am not certain.

I remember the time I broke a rocker arm (and thus one cylinder was inoperational) that the engine mostly drove normally (besides the loud tapping sound). So I'm not sure that generalized misfires would be easily detectable by the butt dyno. My butt dyno is not sensitive.

Maybe misfires were happening to the stock car with the stock coil, but not necessarily perceived as misfires?

Misfires should be detectable by an oxygen sensor as an abundance of uncombusted oxygen (corresponds to a lean fuel mixture).

[This message has been edited by pmbrunelle (edited 05-23-2023).]

La fiera MAY 23, 10:42 PM

quote
Originally posted by pmbrunelle:
My butt dyno is not sensitive.



That's no bueno Patrick! Do whatever it takes to make it sensitive. Use less cushioning on your seat or something. I have nothing on the seat of my car. Its an aluminum seat bolted directly to the floor with no dampers whatsoever. I want to feel every little glitch!

[This message has been edited by La fiera (edited 05-23-2023).]

fieroguru MAY 24, 06:54 AM
Fixed this for you!
Wasted spark coils and crankshaft position sensors started with OBD1 so the timeline was just slightly off.


quote
Originally posted by pmbrunelle:
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I think that distributors were phased out due to a desire to simplify the mechanical aspect, remove the need for timing adjustment, and the need to measure engine position at the crankshaft.

Crankshaft position (without the slack of gears/chains) allows for a more accurate spark, so potentially more optimized spark timing, without risk of over-advancing and knock. So this was a way to gain efficiency.

This brought us to wasted-spark coil packs + crankshaft position sensors.

OBD2 added the requirement of detecting misfires; accurately measuring crankshaft position and double-differentiating it allows the computer to detect torque variations from misfires.

Later on, the EPA required that cars maintain good emissions performance without maintenance for a long time. Spark plug wires (a maintenance item) had to go, which brings us to COP.
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