finally some technical posts. lol
about the reliability fatman(i feel stupid/rude calling you that, have you alternate first name? haha) how would you sum up the reliability of a car setup safe as it may be flatout on a dyno or 1/4mile, how would you describe it, and do you agree with my comment that i may find the constant abuse of a drivers road abit overwhelming?
Phil
Hehe, if it makes you feel better you may call me Greg.
My thoughts on reliability are still evolving. Calling a setup 'reliable' can mean different things to different people. A serious drag racer might call something that didn't immediately explode into flames reliable, somebody building a street car might deem less than a 50,000km lifespan the minimum level to be considered 'reliable' and a circuit racer might want to see 2 years of events from a bottom end.
With reference to a street car, a bracket which I believe the vast majority on this forum would fall into, reliability in my mind would mean years of good performance without dramatic failure. Unfortunately this measure is tailored to my own personal driving style and level of mileage. It's entirely subjective based on the conditions I experience and not really quantifiable. Mileage, whilst quantifiable is definitely not a good measure of reliability as very high powered cars are actually under stressed conditions for LESS of the time under street driven conditions.
Picture a standard 4e-fte, CT9, 0.6bar etc etc. On a motorway onramp from a 20mph roll it might take you 8 seconds of boost in third gear to attain 70mph. These are purely theoretical numbers I'm pulling out of the air here. On a td04l running 1.5 bar, intake, exhaust, ECU etc etc the equivalent acceleration might only take half the time. On a td05 a 2nd gear blast might only take a couple of seconds (traction dependant)
My point is that although you're running a lot more power, you can only use that power (and put significant stress on the engine) for a correspondingly shorter period of time before you hit you goal speed, be it the speed limit or just the practical limit of safety for any given road. In my observation this can actually be kinder over the long term.
To go back to the original engine that caused all this controversy, in Ryans car 2-3 seconds of boost put you WELL into highly illegal territory. 10+seconds of boost and you would be knocking on rev limit in 5th gear. This is I believe why this motor didn't blow itself to pieces, it was well tuned, well optimised and it was virtually impossible to actually stress it for any length of time outside of the Dyno environment.
Compare this to circuit racing. Here is a video of yours truly at a test day at my local racetrack, Pukekohe a couple of years ago.
http://www.youtube.com/watch?v=6Y1GbUPbUmc
This race track is the fastest in the southern hemisphere, average speed over the whole circuit is enormously quick when compared to anywhere else in NZ, Australia or Asia. This was in a standard Glanza V save for some damper adjustable coilovers, fairly crap semi-slick tyres and some good brake pads. As you can see on this clip, I'm actually at WOT for MOST of the track. 25 seconds or so full throttle in 3rd/4th gear to rev limit down the back straight, full throttle 2nd, 3rd and 4th gear before backing off over the hill and then wot 4th gear till rev limit for 30 seconds before turn in to the sweeper, then neutral throttle through the S's before the back straight again. This is enormously hard on an engine. This is what forged internals are for. Would a ragged edge stock bottom end tune running 350hp last under these conditions for 8 20 minute sessions over a test day? Probably not. Does that make it unreliable for street use? I don't think so.
Drag racing is another interesting scenario, different again from street or circuit use. The motor is under significant stress, but for a relatively short period of time, usually with significant warm down time between runs. Certainly harder on the car than street use (how often do you get to 120mph from a standing start on your daily commute?) but much, much less brutal than circuit racing. I believe in this scenario the stock bottom end is suitable and even running very high power levels should last for a very long time (subject to tuning of course). Your driveline on the other hand!
I guess in conclusion to my mammoth post, forged internals certainly have their place. They can cope with prolonged stress better, cope with short term stress (knock, boost spikes etc) better and provide a margin for error essential in building an engine for competitive circuit/rally etc racing. The stock bottom end is very capable and I believe can provide a reliable base for a VERY fast street car capable of being competitive at the drag strip for long enough that I would deem it to be capable of being reliable. That's my opinion, not saying it's a fact. For what the vast majority of the users of these forums need, in my opinion money should be spent on tuning and not on forged rods etc.
