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On one hand it's just a car forum so perhaps it really doesn't matter, but I also don't see why it should degrade into name calling like you'd read in replies to almost any Youtube clip.
Personally I think we should attempt to keep the discussion on point. :-)
It's kind of odd you do not realize how much of a fool of yourself you have made since the beginning of this thread, and you keep digging your own autistic so-called "theoretic" hole instead of listening to people who have field experience to back up their claims.
Your BMW engine has failed? $hit happens. It's nothing but stupid to extrapolate that any 4V head will fail for the same reason on any other engine platform, and this is just what you are doing.
Just take a sit back now and show us how good you can make a 3L 8V.
There are only few examples of built 16 valve turbo cars. That is experimental at best, not a proven reliable solution.
Multivalve heads crack on multivalve turbo cars that were tested to oblivion, and they still crack and here I am expected to just buy the package since few people had good results and everybody else is all wet about the idea?
Failures on piston engines are sometimes simple but other times they are result many undetected factors.
Again, you're wanting us to believe that essentially we are guaranteed of failure if persuing a 16v turbo project yet it's based on very little hard evidence at least in the 944 world. Obviously these builds are still relatively rare but many of us are quite aware of who has done these in the past/currently.
We run our car in Time Attack where we are up against a multitude of turbo charged cars. Mostly all from Japan. They ALL run multivalve motors boosting well over 30psi. While they definitely do suffer mechanical issues, I haven't seen / heard of any that are due to cracked heads.
Quattro GMBH farmed out the B5 RS4 motor to Cosworth ( who they owned at that time) to design/ build and sand cast new blocks/ heads with Comcast. The cracking occurred only in Comcast heads not in the thousands and thousands of turbo charged 1.8/2.7 B5's
BTW, no two F's given that you, literally , don't know what you are talking about.
You're drawing a long bow when expecting us to assume by some cases of a different manufacturer that has a record of some cracked heads that may have been all due to a casting problem therefore we can't make the statement that 16v heads are better than 8v heads?
Another problem with your logic would be that I can't think of any other 2 valve turbo motors that have been made in the last 2-3 decades, hence when you would google cracked heads they would generally only be on multi valve heads. It's a skewed comparison.
I'm not sure that anyone is trying to twist your arm into changing your build from 8v to 16v. As has been stated a number of times, the 8v is quite sufficient for the majority of builds and we agree that it's a simpler path to follow. I don't feel that you've convinced me that I shouldn't consider finishing my 16v build though.
I am not trying to convince anybody in to anything.
I do not support the 'common knowledge' that says 4V head is 'superior in everything' as I believe it is not.
It can breathe better and make more power, but we can't even discuss reliability of it in turbo application since apart from the obviously much more complex cast and mechanic component, it was designed for N/A engines and initial design on such complex casts does matter contrary to popular belief here.
Ill leave these pictures of cut P8V and VW4V stolen from the Internet here and anybody can draw own conclusions about why I claim 4V is more prone to cracks and why most of old 4V heads sport a lot of developed or yet undeveloped internal cracks of all shapes and sizes.
Aprox at the same time, Ford UK also tried to develop F1 4 cylinder turbo engine and failed miserably at that. Although these F1 4 bangers worked they self destructed when put to a proper testing.
I thought i watched a documentary about this engine (and the design of the new one) but they described the engine failure as internal harmonics design flaw
I has been a couple years since i have seen the video but that did seem to stick out to me. I could be wrong.
Yep, the impressive thing about it to me was that it actually worked well enough until they torture tested it, then it repeatedly exploded due to harmonics.
The reference I was trying to point out is that even if an engine runs relatively well, it doesn't mean it wont self destruct when put to proper full blown testing that determines if a certain modification is indeed reliable or not.
Lol in that case 2.5 16v turbo engine has been proven itself to be quite good as it held up the 24hour race, despite the fact that it ran at just 420 hp. And it was completely new design back then.
To me, there is no question. I have tuned tens and tens of 4v engines, heavily turbocharged (I tune ems as a business), some more than 1200 hp and so far there have been no issues with heads cracking. There are other problems like snapping cranks etc but no issues with heads. And yes, most of these cars are BMW M engines and Audi 20V Turbo motors.
Ive been around head repair business and Have burned a valve that destroyed my engine, plus made some money on 24V bmw heads that I bought from germany and sold to locals that had massive cracks, one had more than 10 on single head.
It can work but it can also be a nightmare. 8V head chance of being a nightmare is significantly smaller.
I distrust BMW heads so much that I bought factory new head (even though my wasnt cracked but was welded at some point) for my bmw engine and paid for it probably 10x what I would pay for used one because its like a china vase. It breaks when you look at it from wrong angle.
One of the most popular budget builds over here is just take stock M50B25, mill pistons down by 1mm, put some HX40 there, plug and play MS or VEMS with bigger injectors and boost it to 1.5 bars. It gets you ~450-500 hp quite easy and safe so that drifters use it all the time. It driveas easily through whole season and drifting is very harsh to the engine mostly because of bad cooling and constant high revs.
My take on this is that you being involved in repair business makes your opinion a bit biased because you mostly see cracked heads Failures are everywhere but the percentage is much less than it seems. Take for example 996 and its intermediate shaft bearing issues. While it is notorious for this failure mode, the total percentage is 1% or less..
03-25-2015, 08:23 PM
Failures are everywhere but the percentage is much less than it seems. Take for example 996 and its intermediate shaft bearing issues. While it is notorious for this failure mode, the total percentage is 1% or less..