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raygun: I was responding to cammerjeff's comment about the L3B L-4 engine that I referenced in post 2 in which he said it was likely to be a tight fit in the Kappa engine bay.

The L3B has variable valve timing and lift which combined with the dual-volute turbocharged will give some incredible performance.
 

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The DI engines are great about reducing turbo lag, but an NA motor has zero lag. There's no substitute for off-the-line torque. I love my GXP, but nothing fun happens until 2500RPM.
Why does everyone forget about normal NA engine behavior? They all (including turboed engines) have 'lag. Just take a look at a dyno curve some time. Until they reach the rpm at which they are hitting the torque plateau, they are 'lagging'. Use hotter cam and it is even more evident.

So saying that there is no turbo lag, while technically correct, as there is no turbo, ignores the 'lag' occasioned by the normal operation of the NA engine. Maybe we should start calling the fact that an engine utilizes a camshaft the cause of 'NA' lag...

And FWIW, the LNF products so much torque so early, that they deemed it necessary to set a tune that will not allow full torque production in low gear, lest there be driveline breakage - that's real low torque production!
 

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Why does everyone forget about normal NA engine behavior?
I wouldn't call that lag - and lag on any FI motor is going to be a lot more disruptive than the equivalent on an NA. The torque curve on a given NA engine is typically much more "flat" than on a comparable (whatever that means in this case) FI motor.

Sure, you don't get peak torque at 0RPM unless you're talking about a Tesla. But, it's a lot more predictable, and much easier to manage on a track. I'd rather not have to use NLS to keep power up when working my way through a road course - and it's rarely optimal in terms of lap time to shift at redline, anyway. One of the reasons that the Miata is so popular, despite being severely under powered, is that it's very, very predictable in terms of torque curve, steering (loves to oversteer, but it lets you know beforehand), etc. Having a spike in your torque is not much fun if you're actually *driving* instead of just nailing it between stop lights.
 

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lest there be driveline breakage - that's real low torque production!
That's not-so-great component selection. 260 lb ft - or even "340" with the GMPP tune - isn't that much, and the delivery isn't nearly as smooth as any NA sports car I've owned.

Again, I love the car - I have two of them. But, the goal of any engineer building a turbo motor is to get it to act like an NA, and there's a reason for that.
t
 

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Having a spike in your torque is not much fun if you're actually *driving* instead of just nailing it between stop lights.
Where is this 'spike' you speak of......

 

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Why does everyone forget about normal NA engine behavior? They all (including turboed engines) have 'lag. Just take a look at a dyno curve some time. Until they reach the rpm at which they are hitting the torque plateau, they are 'lagging'. Use hotter cam and it is even more evident.

So saying that there is no turbo lag, while technically correct, as there is no turbo, ignores the 'lag' occasioned by the normal operation of the NA engine. Maybe we should start calling the fact that an engine utilizes a camshaft the cause of 'NA' lag...

And FWIW, the LNF products so much torque so early, that they deemed it necessary to set a tune that will not allow full torque production in low gear, lest there be driveline breakage - that's real low torque production!
I don't follow your use of "lag" in this context. "Turbo lag" as generally used refers to throttle response, and would not be visible on a dyno curve since it dos not report when the throttle was opened. Since the NA engine is the baseline for measuring lag it will, by definition, have none. Belt-driven superchargers have none because their displacement changes with engine RPM. Turbo-superchargers have to react to increased exhaust flow before their displacement can increase, so there is inherent lag. Modern scroll design and valve valve timing will help to reduce lag and the dual-volute turbo, dedicated head design, and variable valve lift
of the L3B will help even more, but physics demands that there will always be some. I have seen design studies of turbos with electric assist that are supposed to eliminate lag entirely, but it seems like a lot of complication for relatively little reward.

The "spike" is not a bump in the dyno curve, it is a bump in the response curve that occurs when the turbo catches up with the engine.
 

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(Earlier response deleted since it didn't really capture the "lag," as in time lag between action and result.)

Thanks, @JohnWR. You explained it much more clearly than I could have.


Though, if I could attempt to put it in simpler terms: lag is the difference between what you expect to happen, and what actually happens, when you mash the throttle. The difference is always more pronounced on a FI engine - way more so on a turbo vs SC or nitrous - vs an NA engine. Unless, of course, you're driving an Aspire uphill - but who would do that on purpose?
 

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The LNF exhibits noticeable although not (to me) objectionable lag in its throttle response. Hit the throttle and the engine reacts ever so slightly later. In contrast the supercharged LE5 almost seems to anticipate the need for power: Touch the throttle and the power is already there with no detectable lag. The NA LE5 has no lag either, but the markedly lower power output makes it difficult to compare to the other two.
 

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Not sure I am understanding you - do you believe that the NA Kappa is much easier to drive than the turbo Kappa?

We haven't really had much lag issue on turbo cars in recent years. I drove race car of a friend - turbo BMW 2002. The lag was so bad that you had to floor the accelerator about when you hit the corner apex in order for it to 'come on' by the time you exited the corner. Worst case I've ever driven.

The LNF in comparison has negligible lag, although those replacing the K04 with larger turbos will experience some.

I drove a Fiero that I had turboed for 20 years and it was one of the smoothest most forgiving cars I've owned.

I currently drive two high output sports cars, one turbo and one not and there is nothing to choose between them - drivability of both is excellent.
 

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Not sure I am understanding you - do you believe that the NA Kappa is much easier to drive than the turbo Kappa?
Yes. My '06 was easier to drive on a track before the turbo kit, and more so than my GXP.

The NA was less entertaining due to being WAY, WAY underpowered, but much easier. By "easier," I mean more predictable. A good driver that's familiar with their car will compensate, and do well. But, and I hope you'd agree: having a jerk in torque when you're approaching an apex is not ideal.

On the other hand, there are many examples where this isn't a big deal, like the late model Boxters with turbo 4's. The engine architecture and management system are so good that lag is barely perceivable. Again, they did their best to make it act like an NA.

The electric assist systems mentioned earlier attempt to counter lag by sending compressed air into the intake before the turbo spools up. (My understanding is that they generally fail in just about every way imaginable.)

The difference between the BMW you mention and the GXP is lag. Sure, it's a really freaking heavy car, but...

The GXP has less lag. But, it's still there and, in my opinion hardly qualifies as negligible. My original point: I'd rather have no lag at all, which means alien technology, nitrous (blech), piping intake through a parallel dimension, or: an NA swap.
 

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The ideal is the supercharger which really is instant power - ran one for awhile on a 4 cylinder MG. Only problem is that they run out of 'whoof' the higher the rpm.

I guess the slight lag that exists in well implemented turbos doesn't bother me much - must have become inured to it with the Fiero, which had a well chosen turbo but still showed a bit more lag than 21st century cars have.
 

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The ideal is the supercharger which really is instant power - ran one for awhile on a 4 cylinder MG. Only problem is that they run out of 'whoof' the higher the rpm.

I guess the slight lag that exists in well implemented turbos doesn't bother me much - must have become inured to it with the Fiero, which had a well chosen turbo but still showed a bit more lag than 21st century cars have.
supercharger on a clutch plus turbo charger.... best of both worlds.... originally implemented 35 years ago.
 

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OP, you might want to research which family of ECMs your desired new engine uses in the chassis GM shipped it in. If it's not the same 'type' as the GXP's Bosch unit, you may find that the wiring becomes far more difficult.
 

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Rough approximations taken off fully dressed engine
with top cover still on.

A-25" to front pulley, seems to be close to the same to the intake front (under the cover).

B-22 1/2" to top of engine cover, perhaps 1/2" to 1" clearance under it (hard to see center of pulley).

C-Approximately 6 3/4"( hard to see center of pulley) to 3" pan depth. It is another 5 3/4"+ from the 3" pan part to the bottom of the deep part of the sump, so a total of 12 1/2"+.

D- sump is deep at back, but only for approximately 5 1/4". This makes for transplant ease!

E- 9" at rear( see D above), 3" for front. ( Note slight inconsistancy with C measurement above - at most 1/4".

F-The widest point is oddly at the front bottom, due to the a/c and alternator being at the bottom. Perhaps they can be relocated. It is approximately 25 1/2".
 
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