300WHP Supernatural 3.XX Coming Soon! (Page 30/54) La fiera NOV 24, 08:16 AM quote Originally posted by ericjon262: OEM's have been offsetting piston pins for years to better balance the thrust loads on the cylinder walls. Very true Eric. La fiera NOV 24, 08:41 AM quote Originally posted by pmbrunelle: You did publish the title of the paper in your video, so you could share it here for other folks to read. ******************************************************************************** So there are perhaps four aspects to consider with the quick-return: 1. With a certain amount of air/fuel mixture in the cylinder, how can the most work be performed on the piston face? The is is called the indicated work. The study you refer to only analyses this aspect of the engine performance, so it's a bit incomplete (not the big picture). Also, it's only computer simulations, so who knows how good those are? The paper did not mention if they adjusted the (simulated) spark advance for different values of offset; I think that optimum spark advance could change. My personal feeling is that quick-return is not good to maximize indicated work on the piston. Ideally, to reduce the load on the crankshaft during the compression stroke, the spark should be delayed as late as possible. Then, at TDC, the spark should light the mixture, and the mixture should completely burn, causing the pressure to rise. Then, the piston should move down from TDC, ideally once combustion is complete. This is the ideal. In practice, we seek to have the mixture burn fast, and the spark is advanced relative to TDC; this gives a compromise between negative work on the compression stroke, and positive work on the power stroke. With quick-return, could the piston start moving down prematurely, preventing the pressure from getting high and pushing down hard on the piston? 2. At the start of the intake stroke, as the piston moves down, this movement kick-starts the movement of the slug of air inside the intake runner. In your engine builds, this seems to be a key factor to success. The quick-return could have a large payoff due to this. 3. Side load on the piston is affected by offset. Since this is for racing, if the engine wears out a bit faster, I don't think you have to worry about that. This doesn't look like a 100 000 km 5-year warranty kind of project. Side load can cause friction. Friction in the engine is why power available at the flywheel is less than indicated power. 4. Assuming that your racing class limits the displacement, you cannot verify compliance with the normal formula: number_cylinders * crank_stroke * bore * bore * pi / 4 You can use the formulas in the paper to find your true displacement. ******************************************************************************** General remark: On the big-bore 60° V6 models such as LZ9, the piston bores are offset (away from the camshaft) by 1.5 mm (I think that's the number). I don't know if the piston pin is centered in the piston. Anyway, if the ECM uses the same tune for both banks, then that means that 1.5 mm shift is not significant. The piston motion is the same for these two scenarios: Pin centered in piston, bore offset Bore centered, pin offset in piston The reason I sent it to you was because since you are an engineer and an analytical person, I wanted to hear your input on the matter. This is only one of the reference material I used to do my research. I also read a paper from an Italian kart engine manufacturer where the shorter ratio engine was much faster on the short and twisty tracks. On the tracks that had long straights the long ratio engine was king. I've been working on this rotating assembly and everything that comprises the engine for 2 years and after I was satisfied then I made it a reality. The only custom parts on it are the pistons. As far as the increase of wear and friction I don't think is going to be a problem. the 3.4L has a rod ratio of 1.72, My 3.7L has a rod ratio of 1.63; same rod ratio found in the 5.7L Chevy smalblock and I have personally seen cars and trucks with those engines hit 200,000 miles on the odometer. ericjon262 NOV 24, 09:00 AM I'm not sold that rod ratio is worth much of anything as long as you aren't at some kind of crazy extreme. Will NOV 24, 09:27 AM quote Originally posted by ericjon262: I'm not sold that rod ratio is worth much of anything as long as you aren't at some kind of crazy extreme. Reher-Morrison peeps have said it's just not important to maximum power... but they're into Pro-Stock, which is neither roundy-round nor road course action. That doesn't mean rod ratio is not important to getting the combination to run at its best... meaning that there's probably some cam optimization that works better with long rods than with short rods, as well as some level of voodoo with regard to vacuum pulses at the venturi for those running calibrated lea--errr... carburettors. sourmash NOV 24, 09:37 AM quote Originally posted by ericjon262: I'm not sold that rod ratio is worth much of anything as long as you aren't at some kind of crazy extreme. All racing is to an extreme. ericjon262 NOV 24, 10:10 AM quote Originally posted by Will: Reher-Morrison peeps have said it's just not important to maximum power... but they're into Pro-Stock, which is neither roundy-round nor road course action. That doesn't mean rod ratio is not important to getting the combination to run at its best... meaning that there's probably some cam optimization that works better with long rods than with short rods, as well as some level of voodoo with regard to vacuum pulses at the venturi for those running calibrated lea--errr... carburettors. True, my statement wasn't meant to imply that it should be brushed aside and forgotten about, but more that for most people operating on the level at which we are probably won't notice a difference between a short and a long rod, as long as the rod isn't ridiculously out of normal range. quote Originally posted by sourmash: All racing is to an extreme. My point isn't that racing isn't extreme, my point is that the ratio would have to be off by a massive value to have a noteworthy difference. IE, you probably won't see a difference going from a 1.65:1 to a 1.72:1, OTOH, if you were to go from a 1:1 ratio to a 1.72:1 ratio, there would potentially be a pronounced difference in performance. La fiera NOV 25, 08:58 AM quote Originally posted by ericjon262: I'm not sold that rod ratio is worth much of anything as long as you aren't at some kind of crazy extreme. Here where I live there's a lot of short oval races and the advantage of the short rod ratio (SRR) engine can clearly be seen on those short tracks. The SRR car leaps and accelerates like a Cheetah off the corners, pulling away from the LRR car. By the time the LRR car stretches its legs and gets close to the SRR car, it is time to hit the brakes. The same process repeats lap after lap. In 20 laps the SRR car almost puts a lap on the LRR car. Now, on a longer track it would be a different story. I've also heard from local 1/8 mile drag racers that the LRR engine makes more power on the dyno but the SRR is faster on the track. Then again, there has to be an advantage. I can see where the LRR engine would shine; 1/2 mile drag race, 1 mile oval track, road race at Daytona, Lemans, etc. In my case I opted for the SRR because the tracks I frequent are short, have tight turns and there's not much straights. La fiera NOV 27, 07:12 PM So, got the trans together this evening. Does anybody know what is the torque spec for that bolt? Thank! La fiera DEC 05, 07:07 PM Update!! The Quife is finally installed And the trans is ready to go in! Upgraded rods, pistons and cam are installed along with the water pump and oil pan. The only things I'm waiting for are the lifters. They were in back order but they are finally on their way. Other miscelanious stuff I'm waiting on are: Modded tall valve covers with vents, new solid clutch disc and "The Fogger" TR5 intake manifold. I'll start the engine for break-in with the TR4 intake to simplify things. claude dalpe DEC 05, 10:36 PM Good job Rei What kind of clutch and model are you going to install