Engine downsizing comes with downside

[edhackett]

Originally Posted By: Ducked

OK, then:-

In the context of IC engines, I suppose it'd be defendable to apply the term "pre-detonation" to the pre-ignition-induced detonation situation I described, IF it occurs.

(Sheesh!)


The situation you describe is called:
Originally Posted By: Shannow
"end gas autoignition", where the flammable gasses remote from the ignition source are "dieseled" by being compressed by the burning gasses.


This would apply whether the ignition was pre- or not.

Ed

 

[Ducked]

Originally Posted By: edhackett
Originally Posted By: Ducked

OK, then:-

In the context of IC engines, I suppose it'd be defendable to apply the term "pre-detonation" to the pre-ignition-induced detonation situation I described, IF it occurs.

(Sheesh!)


The situation you describe is called:
Originally Posted By: Shannow
"end gas autoignition", where the flammable gasses remote from the ignition source are "dieseled" by being compressed by the burning gasses.


This would apply whether the ignition was pre- or not.

Ed


You could call it that (mouthfull though it is), though a full description ends up sounding circular.

Even if the ignition is "pre" the behaviour is actually "detonation" in its general meaning, so "end gas autoignition" is less descriptive, though in an IC context detonation is usually described (and often defined, see above) as post-timed-ignition, so it would be an exception/special case.

That said, now we have something to call it, how significant is "pre-ignition induced end gas autoignition" (= pre-ignition induced detonation)?

Is it specifically involved in LSPI?

I suppose it might not make much difference if it was (apart from perhaps allowing detection by knock sensors) since pre-ignition alone is adequately destructive.

 

[cb_13]

I think you're missing the point. The large displacement of the past is no longer needed. 6.2's are doing a good job of replacing the 454's and 460's of the past.

 

[SteveSRT8]

Originally Posted By: cb_13
I think you're missing the point. The large displacement of the past is no longer needed. 6.2's are doing a good job of replacing the 454's and 460's of the past.


Indeed. Naturally aspirated 6.1 liter here, easily faster AND quicker than my 1970 Chevelle SS454. Also faster/quicker than real genuine stock first gen Hemis in 3 different settings.

 

[L_Sludger]

These are growing pains. The trend towards efficiency mandates precise manufacturing processes for all engine and drivetrain components.

 

[Cujet]

Originally Posted By: cb_13
I think you're missing the point. The large displacement of the past is no longer needed. 6.2's are doing a good job of replacing the 454's and 460's of the past.


While that may be partially true, a 6.2L Camaro is not "chock-a-block" full of low end torque. In fact, it's rather weak down low. Same goes for a 6.2L Corvette. Once the engine is changed to a full 7.0 Liters (427 cubic inches) acceleration at low RPM is markedly more satisfying. Or they add a supercharger to make up for lost displacement.

Yes, new versions of smaller engines are excellent, new versions of large displacement engines are even better.

 

[CBR.worm]

Another contributing issue is that, as we know, lugging is bad. A modern 8 speed auto in a turbo seven series BMW will build full boost just off idle, and will short shift into top gear asap. It will accelerate well at 1,100 rpm in top gear. This is diesel territory, without the 5 pound pistons and cast iron. How can they not expect various forms of pre-ignition.

 

[SilverFusion2010]

I'm liking the flat torque curves the small turbos are making.

 

[4ever4d]

Would water injection not possibly prevent LSPI. Maybe not cost effective though.

 

[BMWTurboDzl]

Originally Posted By: 4ever4d
Would water injection not possibly prevent LSPI. Maybe not cost effective though.


Bosch co-developed with BMW a water injection system for the M4 GTS. Bosch will start offering it to other manufacturers soon.

 

[javacontour]

Originally Posted By: Kibitoshin
Heh I guess you guys got me. Apologies for the moron comment. To tell you the truth I've never driven a turbocharged vehicle and I'm impressed with the power it puts out like the Ford Ecoboost 3.5L. Still not a huge fan of these high strung small displacement engines in terms of reliability though.

But for me it's N/A V8's till I die.


Didn't check to see where you live....

But I suspect that you've not driven at elevation.

Just got back from a vacation out west, Colorado, Wyoming, South Dakota, Montana, Idaho and then the relatively low Washington state.

Our rental was a Ford Edge. IIRC, it has the 2.7 EcoBoost engine.

Didn't seem too impacted by reaching elevations of 12k ft above sea level. If you've driven a naturally aspirated car at elevation, you will notice the loss in performance. Turbos don't have the losses a NA vehicle has.

We had no problems maintaining 80 MPH with the vehicle fully loaded with 4 typical American adults and their luggage for a two week national parks tour.

Turbos have their place. Travelling in elevated terrain is one where they do quite well.

 

[HemiHawk]

I'm pretty sure unless it was a sport, you had the 2.0 4 cylinder turbo in the edge. Not meaning to correct you, instead just pointing out that its even more impressive that at elevation fully loaded as you had it the little 2.0 turbo hauled the SUV and its cargo easily enough.

 

[javacontour]

Originally Posted By: HemiHawk
I'm pretty sure unless it was a sport, you had the 2.0 4 cylinder turbo in the edge. Not meaning to correct you, instead just pointing out that its even more impressive that at elevation fully loaded as you had it the little 2.0 turbo hauled the SUV and its cargo easily enough.


Could have been the Ti or the Sport. Don't recall.

I thought I looked under the hood and saw 2.7L, but it was a 2800 mile journey, so some details may be blurry.

I do know we averaged about 21-22mpg according to the display in the car over that duration and terrain.

Just looking at the specs of both the Ti and the Sport, it's possible we had the sport. A rental with AWD etc could be the Sport as the Intelligent AWD was standard.

It was a pretty loaded up rental.

But either is impressive.

But needed an oil change by the end of our trip.

 

[loneryder]

Originally Posted By: Virtus_Probi
Originally Posted By: Linctex
Originally Posted By: meep

turbocharging is not new---


Just think - the 1987 Buick GNX (underrated at 276 hp from 231 cubes) was 30 YEARS ago!!!


My FXT makes 250HP (probably accurately reported) from 122 cubes and has the benefit of water cooling for the turbo...one of the advances made in the last 30 years. The supposed 420 lb-ft that the GNX made is much closer to the FXT per cube, though.
I actually made a rash decision to go find myself a new Grand National when I was a young punk, but this was around 1988 and their last model year was '87...probably lucky for me, would have been "fun" dealing with that RWD power in snow and ice when I moved back North. Actually, I probably would have crashed and died right away in Dallas...

I test drove a new GN and that thing was [censored] fast. The long needle speedo just jumped to past 60 so you had no idea how fast you were going. Don't know how well they held up. I did see one on the road this past summer going slow in the right lane.

 

[Jarlaxle]

The GN was way underrated, for a simple reason: they had to have a rating lower than the Corvette. Note the 86 and 87 had different power ratings, (230 and 245) despote being identical.

There were water-cooled turbochargers in tbe mid-80s.

 

[Ducked]

Originally Posted By: Ducked
Originally Posted By: edhackett
Originally Posted By: Ducked

OK, then:-

In the context of IC engines, I suppose it'd be defendable to apply the term "pre-detonation" to the pre-ignition-induced detonation situation I described, IF it occurs.

(Sheesh!)


The situation you describe is called:
Originally Posted By: Shannow
"end gas autoignition", where the flammable gasses remote from the ignition source are "dieseled" by being compressed by the burning gasses.


This would apply whether the ignition was pre- or not.

Ed


You could call it that (mouthfull though it is), though a full description ends up sounding circular.

Even if the ignition is "pre" the behaviour is actually "detonation" in its general meaning, so "end gas autoignition" is less descriptive, though in an IC context detonation is usually described (and often defined, see above) as post-timed-ignition, so it would be an exception/special case.

That said, now we have something to call it, how significant is "pre-ignition induced end gas autoignition" (= pre-ignition induced detonation)?

Is it specifically involved in LSPI?

I suppose it might not make much difference if it was (apart from perhaps allowing detection by knock sensors) since pre-ignition alone is adequately destructive.


The description in this recently linked blog suggests that "pre-ignition-induced detonation" IS a feature of LSPI (they call it "superknock", but when used carefully "knock" is usually a synonym for detonation), so this does appear to be an exception to/widening of the usual post-ignition definition of knock/ping/detonation.

http://stratifiedauto.com/blog/low-speed...coboost-motors/

Told you so.

 

[UG_Passat]

Originally Posted By: Lolvoguy
"there's no replacement for displacement"

That also apples to the turbochargers themselves as well.

 

[UG_Passat]

Originally Posted By: Jarlaxle
Originally Posted By: Virtus_Probi
Originally Posted By: Linctex
Originally Posted By: meep

turbocharging is not new---


Just think - the 1987 Buick GNX (underrated at 276 hp from 231 cubes) was 30 YEARS ago!!!


My FXT makes 250HP (probably accurately reported) from 122 cubes and has the benefit of water cooling for the turbo...one of the advances made in the last 30 years. The supposed 420 lb-ft that the GNX made is much closer to the FXT per cube, though.
I actually made a rash decision to go find myself a new Grand National when I was a young punk, but this was around 1988 and their last model year was '87...probably lucky for me, would have been "fun" dealing with that RWD power in snow and ice when I moved back North. Actually, I probably would have crashed and died right away in Dallas...


Chrysler had water-cooled turbochargers 30+ years ago. (And managed 224HP from a 2.2 litre engine.)


Chrysler had had Variable Geometry Turbos back then also, well before VW used them on TDI's and Porsche using them on certain 911 engines.