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#15
by
arb
on 21 Apr, 2009 11:21
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If you are actually going to try to go that high, I think you should find some stiffer plunger return springs.
Maybe a fuel cooler as well?
Call Giles and ask him if there is anything that will allow the IP to go that high and still fuel the beast. He's probably heard it all as far as the pump goes.
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#16
by
idgtd
on 21 Apr, 2009 11:27
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I think if nothing else your mean piston speed is going to start being an issue. The long stroke of our diesel engines hurts us for durability at high revs because the piston speeds go through the roof. Most cars on the street have mean piston speeds at redline of about 3000 ft/min. Performance and race engines are in the 4000 - 4500 range. An F1 engine will be ~ 4900 ft/min. An AAZ at 8000rpm has a mean piston speed of 5013 ft/min! At that speed, you have some serious technical issues regarding ring and piston design that might be difficult to overcome.
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#17
by
lord_verminaard
on 21 Apr, 2009 11:32
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8000!?!? That's way too high! Mind you I don't even like the idea of going past redline on these engines. You have to remember they weren't designed to rev high like that and anytime you bring an engine that high the wear and tear on it increases.
I doubt you would get good solid power up that high. IMO stay in the lower rpm power band and use your gears! 
The engine RPM isn't the problem- the basic VW inline 4-cylinder design can handle just about any RPM's you could make power at. Therin lies the problem though, making power at those RPM's. VW's typical naturally-aspirated 8v design, even with extensive porting and cam work, runs out of airflow at around 7500 rpms tops, and that is in a formula super-vee type cylinder head- which was limited to 1600 cc and therefore the valves could only go so big.
Of course, the turbo can fix that. Just stuff more air into the head. But there is still a limitation of valve size and maximum airflow before efficiencies get thrown out the window and cylinder pressure becomes so high that it lifts the head off the block.
Then there is the pump. I doubt even Giles has seen a Bosch VE-style pump that was capable of turning an engine 8000 rpm's. At least not more than for one glorious instant.
I don't know the physics involved of the internals of a VE pump well enough to know what goes on at that sort of RPM but I would imagine it's mind-blowing.
If there was a way to get an inline-injection pump easily adopted to a VW engine, that would be road I'd take.
Brendan
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#18
by
jtanguay
on 21 Apr, 2009 11:51
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everyones forgetting about balancing/lightening too. the crank would have to be very well balanced, rods, pistons, flywheel... probably the best platform for an 8k rpm-o-death diesel would be a 1.5, but modify a 1.6 block as the 1.5's don't hold up so well with the 11mm head bolts. studs everywhere will be a requirement for everything to hold together, and a girdle would be highly recommended.
get rid of any accessories that you can such as a/c and power steering, and get an underdrive pulley. you might want to consider an auxiliary coolant pump at this point to ensure proper cooling, or add something to the coolant to increase efficiency.
i think this is totally do-able, but will take $$$ to pull off. i think head sealing issues will also arise if you're making high power in the upper rpm ranges.
a nice VNT-17 (or 20) turbo would really complete this engine :twisted:
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#19
by
Aki-76
on 21 Apr, 2009 12:04
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8000rpm is too high..7000-7200 maybe,we will see....
crank is very spesial,piston light weight and rods..jeah,you see later
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#20
by
Op-Ivy
on 21 Apr, 2009 12:05
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I think if nothing else your mean piston speed is going to start being an issue. The long stroke of our diesel engines hurts us for durability at high revs because the piston speeds go through the roof. Most cars on the street have mean piston speeds at redline of about 3000 ft/min. Performance and race engines are in the 4000 - 4500 range. An F1 engine will be ~ 4900 ft/min. An AAZ at 8000rpm has a mean piston speed of 5013 ft/min! At that speed, you have some serious technical issues regarding ring and piston design that might be difficult to overcome.
Exactly! Like I said before, these engines are not designed to rev that high. With serious modification however, 8000rpm could be achievable with many of the original parts. But even then I wouldn't count on reliability for too long.
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#21
by
jtanguay
on 21 Apr, 2009 12:17
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personally i would rather a super long stroke over short for high revving. cruising at 1000 rpm would kick butt
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#22
by
truckinwagen
on 21 Apr, 2009 12:24
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I am going to try to build a short stroke 1.6 with a 1.5 crank and 1.9 rods and pistons in a sleeved 1.6 block.
I am going to see how high it can go and still make power, then I will throw a G60 supercharger on it.
if my car ever runs that is...
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#23
by
idgtd
on 21 Apr, 2009 13:02
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VW's typical naturally-aspirated 8v design, even with extensive porting and cam work, runs out of airflow at around 7500 rpms tops, and that is in a formula super-vee type cylinder head- which was limited to 1600 cc and therefore the valves could only go so big.
Exactly. Those FSV engines had a 80mm stroke, so that works out to about 4000 ft/min at 7650rpm. And a FSV engine is a full out race engine, make no mistake. The issue really isn't balancing and such, it's that the acceleration forces at those piston speeds challenge the most advanced material properties. Ring flutter induced by rapid piston acceleration has a detrimental effect on sealing, which on a loaded engine is death. The pistons and rings have to be extremely light to resist the acceleration induced problems, but then the rings are so thin that their life on boost is measured in minutes rather than hours.
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#24
by
Smokey Eddy
on 21 Apr, 2009 15:00
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I read the first 6 or 7 posts and it continued on about governor and the rollers in the pump.
But is no one going to be concerned about pistons ejecting them selves from the crank at 8,000 rpm? I don't feel like doing the math right now but those are heavy pistons to be traveling at those speeds and changing direction 180 degrees in a matter of milliseconds.
Another thought,
If the engine is "safe" to rev that high... can you red line (be it 5,000?) these engines with no concern?
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#25
by
truckinwagen
on 21 Apr, 2009 15:10
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there are a couple things to think about when revving, first is the valvetrain, to get that high you would def need a mech head and HD springs/lightweight valves/retainers/lifters
next, shorter stroke is always better for revving as it will slow the pistons at a given RPM compared to a longer stroke motor.
also longer rods are better as they have longer dwell times and will help keep the acceleration/de-acceleration down with higher RPM's.
the 1.5 motor has both a shorter stroke and longer rods making it a better candidate for revving, but I want to take it further with a 1.5 crank(shorter stroke) and 1.9 rods(even longer rod)
using the 1.9 piston brings the displacement back up to 1.6L.
everything will have to be lightened/balanced as much as possible without sacrificing strength.
I will probably get a set of aftermarket rods (tdi ones most likely) and go all out with ARP hardware to keep it together with low friction coatings on everything that can take one.
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#26
by
Op-Ivy
on 21 Apr, 2009 15:10
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That came up a few posts ago Eddy. Basically, the higher you go the more stress that the engine will be put under. You probably could run the car up to 8000 rpm many times, but eventually something is going to, quite literally, fall apart.
Going to 5000 still poses the same threats. The higher you go the more strain. :twisted:
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#27
by
burn_your_money
on 21 Apr, 2009 15:50
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Has anyone actually found the redline of one of VWs diesel engines? I mean with stock internals but a modified pump. I was hoping to blow up my NA that way but when the tranny went there went that idea as well.
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#28
by
RabbitJockey
on 21 Apr, 2009 16:02
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Has anyone actually found the redline of one of VWs diesel engines? I mean with stock internals but a modified pump. I was hoping to blow up my NA that way but when the tranny went there went that idea as well.
i wish i had a tach on my old rabbit when it ran away and blew up, that would have been nice to know since there was no piston, rod or valve train damage and that thing was screaming. honestly though i think revving one of these motors to 8k is going to take alot of work, maybe a custom inline pump would be able to do it, but really common rail and a computer would be what i would think would work best, or maybe an 8cylinder pump setup some with 2 lines to each injector. but honestly with the weight of the internals and many other factors i just really can't see this being done in any kind of way that is even remotely cost effective or practical.
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#29
by
Smokey Eddy
on 21 Apr, 2009 21:05
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What is the advantage again of reving to 8 grand? other than sounding like a street bike...