Ryan.G Posted May 25, 2011 Share Posted May 25, 2011 Yeah mate , you should see that power then , just be mindful now that u have larger cams and if the timming belt tensoner snaps it could damge ur engine , titan offer a billet timming belt tensioner . Very good advice! Seen it happen twice now on the dyno, One got away with it the other did not and was a complete rebuild Quote Link to comment Share on other sites More sharing options...
hodge Posted May 25, 2011 Author Share Posted May 25, 2011 Yeah mate , you should see that power then , just be mindful now that u have larger cams and if the timming belt tensoner snaps it could damge ur engine , titan offer a billet timming belt tensioner . Beat order 1 of those too then. Quote Link to comment Share on other sites More sharing options...
Ricky49 Posted May 25, 2011 Share Posted May 25, 2011 As im not very technical but my understanding is that isn't it the rod bolt that goes under more stress with higher rpm. Wouldn't the rod just hold on until the rod bolt gave up. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 27, 2011 Share Posted May 27, 2011 95% of the time a snapped rod is caused by an over rev. Jamie's bent rod was almost certainly caused by the piston's partial seizure evident around the ring lands, probably a result in itself of detonation or excess crown temps. Despite what the Americans claim to get away with it's a production engine designed to handle X amount of BHP at Y pounds of boost, on Z octane fuel. For sure, it's a strong engine, but to say the stock bottom end is good for 700 BHP is plainly ludicrous. It may survive it in short bursts, with very safe air fuel ratios, occasionally. It certainly is pushing your luck to expect it to survive a track day, in the summer, driven as hard as it will go. 11 seconds up a drag strip with long cool down periods is one thing. 30 minute sessions round Donington, quite another. The physics of heat rejection are immutable. A proper 700 BHP engine will be freshly built, using mainly new parts, with a steel crank, forged pistons, steel rods, a huge oil cooler, properly ducted rad with maybe the viscous locked solid, and decent fuel on a properly done map, with load points held throughout the map to allow temps to stabilise on the dyno, not mapped via datalogs of AFR from inertial runs through one gear, done in a few seconds. I cringe at these high mileage engines that really should be used with respect in stock form, in their latter years, being asked to produce monstrous power on tired bottom ends, and leaky valves Quote Link to comment Share on other sites More sharing options...
Kirk Posted May 27, 2011 Share Posted May 27, 2011 (edited) I hate to butt in here but my car managed to do this and its only an NA.... http://a2.sphotos.ak.fbcdn.net/hphotos-ak-snc1/9720_165364287213_584057213_3773909_5318098_n.jpg And you worry at your power level...... honestly Edited May 27, 2011 by Kirk (see edit history) Quote Link to comment Share on other sites More sharing options...
Rob_Mitchell Posted May 27, 2011 Share Posted May 27, 2011 wow!! ouch Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 27, 2011 Share Posted May 27, 2011 I am not being personal, even Skyline engines sometimes decide they have had enough. This was an old engine of mine that went beyond its maintenance hours and decided to break a Tomei rod bolt. No over revving, just old age and fatigue. http://www.gatesgarth.com/bang/bang.html "It'll manage one more track day, then it can be rebuilt over the winter". Right...... Quote Link to comment Share on other sites More sharing options...
Samurai 20V Posted May 27, 2011 Share Posted May 27, 2011 I am not being personal, even Skyline engines sometimes decide they have had enough. This was an old engine of mine that went beyond its maintenance hours and decided to break a Tomei rod bolt. No over revving, just old age and fatigue. http://www.gatesgarth.com/bang/bang.html "It'll manage one more track day, then it can be rebuilt over the winter". Right...... Thats a right mess.. From my experience with my 4A-GE 20V, the rods tend to snap with excessive revs.. The car revs to 8200rpm stock, they can rev to 9000rpm "safely".. Some ppl have pushed them to 9500rpm, many have snapped them after 9000rpm.. Jamies rod is not revs for sure, just metal pushed past its limit for too long.. I tend to agree with Chris, I think someone who has used a high power supra for a long time (every day, track and drag use) on the stock bottom end might be a decent benchmark to determine a "safe" limit... Just my thoughts... Quote Link to comment Share on other sites More sharing options...
Thorin Posted May 27, 2011 Share Posted May 27, 2011 I did this to one at about 750-800bhp on a top speed run, flat out in 6th. http://i30.photobucket.com/albums/c338/jamie450x/c35f0a80.jpg http://i30.photobucket.com/albums/c338/jamie450x/7fcf407c.jpg Makes a nice souvenir for the mantle piece though! Quote Link to comment Share on other sites More sharing options...
Wez Posted May 27, 2011 Share Posted May 27, 2011 Loving the pics in this thread Quote Link to comment Share on other sites More sharing options...
Geo Posted May 27, 2011 Share Posted May 27, 2011 So what would cause a Stock Rod to Snap My Answer is...... JamieP Job Done!!! Sorry Bud. Quote Link to comment Share on other sites More sharing options...
Steve Posted May 27, 2011 Share Posted May 27, 2011 So what would cause a Stock Rod to Snap My Answer is...... JamieP Job Done!!! Sorry Bud. In all fairness, he didn't snap it just bent it slightly Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 27, 2011 Share Posted May 27, 2011 A rod will bend in compression, like JP's, due to one or more of three things. Hydraulic lock due to incompressible fluid above the piston. Piston seizure making it all but impossible for the crank and rod to push / pull the piston up and down the bore (50 / 50 as to whether the rod bends in compression, or snaps in extension here, depending on the forces and timing of the event). Massive cylinder pressures due to very excessive boost. Obviously the strength of the rods will dictate how much abuse they will stand, and a steel rod will stretch or bend before failing, whereas a sintered rod will usually just fail catastrophically. Quote Link to comment Share on other sites More sharing options...
fastby4 Posted May 27, 2011 Share Posted May 27, 2011 My old engine runs 60 000 Km without any problems set up HKS GT28/35,rev limiter 8500 rpm @ 1,9 bar boost, Dyno 840 PS than I am change to bigger Turbos GT 32/37 and 2,4 bar boost,one push and this is the result. Thomas Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted May 27, 2011 Share Posted May 27, 2011 (edited) 2.4 bar is a LOT of boost. I think that, and the rods DEFINITELY think that, too Quite impressed by the S shape without a total failure though! I take it the artificially shortened rod caused the underside of the piston to touch the crank counterweight? Did it chop off the oil squirter nozzle, too? A friend of mine had a wonderful "Black Museum" cupboard with some remarkable bits of blown engines on display. The cupboard bore a nice engraved sign proclaiming "Maximum power comes at unforeseen prices, how fast can YOU afford to go" Edited May 27, 2011 by Chris Wilson (see edit history) Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted May 27, 2011 Share Posted May 27, 2011 "Maximum power comes at unforeseen prices, how fast can YOU afford to go" Now theres a mantra to tune by Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted May 27, 2011 Share Posted May 27, 2011 Remember Jurgens engine? Quote Link to comment Share on other sites More sharing options...
Samurai 20V Posted May 28, 2011 Share Posted May 28, 2011 Its amazing that did not break under 2.4bar boost... Quote Link to comment Share on other sites More sharing options...
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