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928 engine design??? Strengths-weaknesses?

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Old 04-08-2013, 02:00 AM
  #16  
blau928
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Originally Posted by Lizard928
Brian,

None of those that you list are linked to a weak bottom end.

And as to the oiling deficiencies, there are some weaker spots for sure, but to think that the oiling system is 100% is blame is silly.

Greg Brown told us awhile ago about a 911 variant that had soft bearings (like ours), and when on the track would nuke engines very fast. But once the timing was pulled back a little (not run on the edge like the S4), they lived happily. All because the light knocking that was happening would hammer the bearings to the point of failure. This is the first I have really mentioned this on here. But this needs to be given thought.

A race motor that is held at higher RPMS really should have the injectors MUCH further from the valves to help obtain a more even AFR throughout the combustion chamber. This will help to give a better burn, show less knocks, as well as help to control/reduce some ring flutter (of which the S4 engine is HORRIBLE for).

The intake manifold that I have (99%) completed for my turbo car is using a shower style injector placement for these specific reasons. Along with a vacuum pump to help try to obtain a better ring seal and prevent ring flutter.

Everyone is always chasing after more power out of the engines and for good reason, you want to be faster, especially on the track. And on a street car I will put a MUCH more aggressive tune then I would EVER put on a track car. The VEMS setup that I just put onto Sean's track car with VEMS uses a maximum of 26 deg of advance (stock cams), and above 5k rpm you can clearly see that the intake is a massive restriction. My dyno testing on a stock S4 showed negligible difference on output between 30 deg, and 26 deg. But with 26 deg, there was not even a hint of knocking.

You have had good success with the 16V motors, I feel this is likely that a) their crankcase breathing isnt total gobshiyte, b) stock form run less advance, c) smaller bore diameter is less prone to ring flutter.
There are likely more factors at play, but these are a good portion of them.
Hi Colin,

I am curious about your injector theory about being further away from the valve..

How far away, and what angle in the runner are the ones you intend to put in..??

Thanks,
Old 04-08-2013, 02:37 AM
  #17  
Rob Edwards
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Seems to me that a large piece of the pie in engine failures (other than just plain metallurgic failures) is a combination of poor oil control and insufficient control over ignition timing and fueling. Which both boil down to preventing detonation.

Sharktuner, Alpha N, VEMS, megasquirt, Link, etc, are amazing tools, I have to imagine that the the initial buy-in on any of these systems would save their costs many times over in preventing or at least prolonging the on-track lifespans of these motors.
Old 04-08-2013, 02:42 AM
  #18  
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Richard,

There are many articles on this, I challenge you to do your own research, your own tests, and draw your own conclusions.

That being said, for the intercept angle of the injector to the airstream. It should never exceed 45 deg, but is best to be shot straight into the runner therefor being straight in line with the airflow to achieve the best atomization.

Having the injector far away from the valve can hurt idle quality especially with big lumpy cams/low vacuum (less than 14" Hg). However there are definite gains to be had from this. Moving the injector farther away from the valve allows more time for the air/fuel to atomize properly and remain in suspension when air velocity comes up at high rpm. This should improve peak power but-because of poor low-rpm velocity-at the expense of idle quality especially with injectors larger than 96#.
Some engines have seen 50+ hp gains just from moving the injectors further away from the valves because of the more consistent AFR in the chamber, and better atomization.

As for my intake. I made my runners vertical, 90 deg straight up. I could have angled them at 15 deg to match the one wall on the S4 intake port. But I chose vertical, and then modified the port where the injector notch is to achieve a more vertical port. My total runner length is closer to 7.5", and the injector sits above the port looking straight down the middle into it. I'm running 60# injectors btw, which did achieve a very nice idle on a stock S4 intake manifold. Keep in mind, this intake is designed around my own theory (which hasnt been fully tested, but will be soon!), for maximum HP with boost on a 5.0L motor.
Old 04-08-2013, 02:48 AM
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Originally Posted by Rob Edwards
Seems to me that a large piece of the pie in engine failures (other than just plain metallurgic failures) is a combination of poor oil control and insufficient control over ignition timing and fueling. Which both boil down to preventing detonation.

Sharktuner, Alpha N, VEMS, megasquirt, Link, etc, are amazing tools, I have to imagine that the the initial buy-in on any of these systems would save their costs many times over in preventing or at least prolonging the on-track lifespans of these motors.
Those tools you refer to Rob, are just those, tools. And any tool in the hands of an inexperienced person is a very dangerous proposition.
I have done multiple standalone installs, and I can say, when it actually comes to the tuning of an engine, and having it be reliable, the learning curve is bloody steep. The sharktuner is a great tool, and the factory brains are actually great for their vintage, but they can only save so much. The sharkplotter again is a great tool, which I am certain has probably saved a number of engines from those who are unaware as to what is truly needed to make it run right.
However, I would not trust many if anyone else to tune my engine and expect it to actually last under race conditions.
Old 04-08-2013, 02:56 AM
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For race tuning, I agree 100%! I am barely competent to do a safe street tune with the ST2 and SP (where 'safe' = no knocks anywhere on the map), but on track the margins are so much smaller. At least I'm willing to know what I do'nt know, and the motor we're planning for the white Zombie is certainly not going to be tuned by me.
Old 04-08-2013, 03:04 AM
  #21  
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Originally Posted by Rob Edwards
For race tuning, I agree 100%! I am barely competent to do a safe street tune with the ST2 and SP (where 'safe' = no knocks anywhere on the map), but on track the margins are so much smaller. At least I'm willing to know what I do'nt know, and the motor we're planning for the white Zombie is certainly not going to be tuned by me.
A wise man knows his limits, and always challenges them.
When you are ready to tune the zombie, there will always be help. Just be ready to learn. That's the only way I know as much as I do today!!! Research, listening, asking questions, and absorbing as much as I could.
Old 04-08-2013, 12:20 PM
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Originally Posted by Lizard928
Richard,

There are many articles on this, I challenge you to do your own research, your own tests, and draw your own conclusions.

That being said, for the intercept angle of the injector to the airstream. It should never exceed 45 deg, but is best to be shot straight into the runner therefor being straight in line with the airflow to achieve the best atomization.

Having the injector far away from the valve can hurt idle quality especially with big lumpy cams/low vacuum (less than 14" Hg). However there are definite gains to be had from this. Moving the injector farther away from the valve allows more time for the air/fuel to atomize properly and remain in suspension when air velocity comes up at high rpm. This should improve peak power but-because of poor low-rpm velocity-at the expense of idle quality especially with injectors larger than 96#.
Some engines have seen 50+ hp gains just from moving the injectors further away from the valves because of the more consistent AFR in the chamber, and better atomization.

As for my intake. I made my runners vertical, 90 deg straight up. I could have angled them at 15 deg to match the one wall on the S4 intake port. But I chose vertical, and then modified the port where the injector notch is to achieve a more vertical port. My total runner length is closer to 7.5", and the injector sits above the port looking straight down the middle into it. I'm running 60# injectors btw, which did achieve a very nice idle on a stock S4 intake manifold. Keep in mind, this intake is designed around my own theory (which hasnt been fully tested, but will be soon!), for maximum HP with boost on a 5.0L motor.
Hi Colin,

I have done my own research, and come to some different conclusions..

Actually, not far off from some of the things you mention, but without knowing several other parameters like velocity of the air charge, injectory type, and where any of the bends (if any in the case of non-ITB setup) are in relation to the injector and port I would not be able to comment properly.

Sounds interesting though...



Rob,

I agree with you on the detonation issue.... Thermodynamics is the issue to resolve for a powerful and efficient motor..

BTW, great that you're the custodian of Anderson's car..!
Old 04-08-2013, 12:56 PM
  #23  
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I speak from personal experience...

Old GTS motor blew up as it had no oil in the dry sump tank and was run for close to a minute at at full throttle... Damage was two bent 2R rods (2 and 6), 8 galled pistons and damaged 2/6 area on the crank journal. X-rayed the block - no damage, x-rayed the crank - no damage... That's pretty strong in my book...

There is no point theorising - new block, new schmlok... By the time you get into that sort of cash outlay, you are buying a E46 V8 M3 GTR or a 997 Cup Car anyway... Fact is, everything breaks when subjected to abnormal loads or unexpected conditions. I think if I had bothered to check my oil level, I would be several thousand dollars richer...

Dry Sumping does solve the oiling problems, provided the design of the pan is correct - we have three cars in the UK running the same design - a 470rwhp stroker, a 360rwhp GTS and my 438rwhp GTS. All three have been running for years and the bearings are like new. Perhaps the fact that PACE Products usually works with F1 helps?

With regards to tuning/mapping... Agree with most of what Colin says... We spent close to 12hrs on a Mustang trying to get the car to drive right... FYI, first time we did a run with the stock maps (1990 GT) we registered 240knock events by 5500rpm. Now she drives fine. Let's just also say, that I think my engine is pretty unique when it comes to ITB-ed 928s with regards to injector placement, runner length, runner orientation, ITB shape etc. I guess that's why it makes what it makes with stock displacement...

Is it reliable - I hope so. Can I do something more - sure - go and buy a 996GT3 Cup car, but that kind of defeats the purpose...
Old 04-08-2013, 01:03 PM
  #24  
Mike Simard
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Originally Posted by IcemanG17
I was doing research on successful long lasting V8 race engines......the single different "design" difference I see vs our 928 engines is the bottom end....the block & girdle design of our engines appears much weaker than many other designs.....specifically the chebby LS series and the Ford Windsor Y block design.... Looking at how many stroker or high HP 928 engines crack the block webbing it has me thinking that the lower girdle might be a significant weak spot...
Aside from the brittle material, the 928 design is very good and had features that are superior to the old American pushrod v8s.

The cracking seen in the main webbing is real though and feel that I've greatly reduced (I nearly say eliminate) the chance of that ever happening in my own engine but nobody else at all seems to care.

The reason for any V engine cracking there is detonation forces.
(the friction welding TBF failures in autos are a different story)
I consider fastener design the most misunderstood part of engine building and that's key to why I don't worry about my block cracking. I make special head and main studs and use a girdle over the bottom of the engine that must look pointless to everyone else. I know the direction of forces seen when things go wrong and that's what dictates the design.

I've made bunches of head studs and am making more now but nobody ever wants the mains.

These threads always seem to bring up chevy and ford fanbois and they spout about durability (and cheapness) but I've seen plenty of them fail. When I go racing there's typically a vette motor that fails every time but yet we have to hear about them being bulletproof in these threads.

It's an ironic case of mass perception, in daily driver cars, most consumers that buy a Honda feel that they are so smart and if it breaks down it's something that happens even to the best sometimes. if they buy a Ford, it gets taken back to the dealer for minor stuff becasue it's a damn POS!

And so it goes with Porsche and Chevy engines
Old 04-08-2013, 01:44 PM
  #25  
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If you got a kit which helps prevent it, offer it. I am sure someone will buy it (I will too once I get my 928)

Hondas and Fords:
Hondas are usually good until ~100k-200k before any problems arises long after the warranty expires (their quality went down in recent years, but usually the warranty expires before problem arises)
Fords on the other hand it can be ~5k-20k which the warranty is still in effect.
Another problem is with Fords, it is a hit or miss with their lemons (IE their quality control was very bad around 10-15 years ago).
I got two friends with the same year Explorer. One never had problems, the other had the explorer at the Ford dealer every month for some type of problem. They improved over the years, but it is very hard to shed off that image of being a lemon car maker.

Personally I say Hyundai/Kia replaced Honda/Toyota in quality, while high end cars kept their quality mostly the same across all brands maybe one or two hickups but on average good quality [Japanese/German/Italian/USA/Brits]


Originally Posted by Mike Simard
Aside from the brittle material, the 928 design is very good and had features that are superior to the old American pushrod v8s.

The cracking seen in the main webbing is real though and feel that I've greatly reduced (I nearly say eliminate) the chance of that ever happening in my own engine but nobody else at all seems to care.

The reason for any V engine cracking there is detonation forces.
(the friction welding TBF failures in autos are a different story)
I consider fastener design the most misunderstood part of engine building and that's key to why I don't worry about my block cracking. I make special head and main studs and use a girdle over the bottom of the engine that must look pointless to everyone else. I know the direction of forces seen when things go wrong and that's what dictates the design.

I've made bunches of head studs and am making more now but nobody ever wants the mains.

These threads always seem to bring up chevy and ford fanbois and they spout about durability (and cheapness) but I've seen plenty of them fail. When I go racing there's typically a vette motor that fails every time but yet we have to hear about them being bulletproof in these threads.

It's an ironic case of mass perception, in daily driver cars, most consumers that buy a Honda feel that they are so smart and if it breaks down it's something that happens even to the best sometimes. if they buy a Ford, it gets taken back to the dealer for minor stuff becasue it's a damn POS!

And so it goes with Porsche and Chevy engines
Old 04-08-2013, 04:22 PM
  #26  
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Originally Posted by Mike Simard
Aside from the brittle material, the 928 design is very good and had features that are superior to the old American pushrod v8s.

The cracking seen in the main webbing is real though and feel that I've greatly reduced (I nearly say eliminate) the chance of that ever happening in my own engine but nobody else at all seems to care.

The reason for any V engine cracking there is detonation forces.
(the friction welding TBF failures in autos are a different story)
I consider fastener design the most misunderstood part of engine building and that's key to why I don't worry about my block cracking. I make special head and main studs and use a girdle over the bottom of the engine that must look pointless to everyone else. I know the direction of forces seen when things go wrong and that's what dictates the design.

I've made bunches of head studs and am making more now but nobody ever wants the mains.

These threads always seem to bring up chevy and ford fanbois and they spout about durability (and cheapness) but I've seen plenty of them fail. When I go racing there's typically a vette motor that fails every time but yet we have to hear about them being bulletproof in these threads.

It's an ironic case of mass perception, in daily driver cars, most consumers that buy a Honda feel that they are so smart and if it breaks down it's something that happens even to the best sometimes. if they buy a Ford, it gets taken back to the dealer for minor stuff becasue it's a damn POS!

And so it goes with Porsche and Chevy engines
Mike,

I totally agree with you on this... The detonation control is key to it all... Great job on the girdle, and stud hardware.. I also think that so many miss the point of what needs to happen on a race motor..

I am surely going to get heat for these words...
Old 04-08-2013, 08:29 PM
  #27  
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Without a doubt Mike does amazing work....same for Doc Brown..... There must be hundreds of hours of engineering little things inside Mikes motor that nobody even knows about... A proper main stud & rod bolts is another excellent idea.....

As I said early on....I am far from an engineer.....I am just a passionate 928er who races 928's & doesn't want to install my LS2 engine in it.... Of course I want an ideal 928 engine....one that is supremely reliable AND makes great power....

I think I have found a reliable solution for very little money with just a 3/8 pan spacer + OB oil pan.... 120+ hours on my old estate with this setup...no other race 928 EVER can come close to this.... keep in mind this is an endurance racing 928....all the others were sprint racers that ran at most 30 minutes at a time vs 8+ hour per day. But I didn't want to make this an oiling debate.....



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