Terminator Posted November 9, 2007 Share Posted November 9, 2007 LOL I know the internals of the RB25DET quite well unfortunately. What HG and studs are you using Chris? Quote Link to comment Share on other sites More sharing options...
b_have Posted November 9, 2007 Share Posted November 9, 2007 I have indeed had experience of plenty of rod failures, my own Skyline engine broke an ARP rod bolt this year. http://www.gatesgarth.com/bang/DSC04209.JPG Looks like a stud to me? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted November 9, 2007 Share Posted November 9, 2007 As stock the RB25 and RB26 rods use through bolts and nuts, which is a bit naff, IMO, but there you are Quote Link to comment Share on other sites More sharing options...
Daston Posted November 10, 2007 Share Posted November 10, 2007 If you were going to change your cams what else is needed? Or is it just a straight swap? Quote Link to comment Share on other sites More sharing options...
Guest whatthe Posted November 14, 2007 Share Posted November 14, 2007 You've experienced many failures at 7500rpms on the 2JZ-GTE, or you've experienced many rod failures? , although its a sample size of one. Good for him for being prepared to try it out, though. Personally, I know that inertia loads increase by the square of the change in engine speed, so you won't have to go too far before you are going seriously beyond what Toyota will have considered in their design. Unfortunately, without access to simulation codes or an actual test engine that someone is willing to sacrifice, there will never be a definitive answer. Sample size of 2JZs running at 7500rpms = Many, not one. I think you missed my first post showing the software that RCTS has been selling for 2JZs with 7500rpm limit for a long time (8-10 years?). Also, the mention about math that would imply very quick failure for those guys running over 8000rpms if it was going to pop at 7500rpms. As for RCTS, there have been days where you could walk in and see 2 MKIVs on the lifts, 2 under the lifts, 1 on the dyno, and a few spread on the floor. RCTS has built a lot of MKIVs for a lot of customers who have paid a lot of good money for good advice. I could list his collaborations with Toyota and at Toyota and probably do an ok job at his personal resume, but I really don't see the point. I was just looking for a straight forward answer to my question in the first post and wanted to provide more than 1 example for you. The makers limit seems like a moot point without actually having the documentation from Toyota engineering. Do people actually try to blow stuff and find the limits of an engine when it's not available? Absolutely. I would expect this to be the case especially on an engine like the 2JZ-GTE which has already had basically every mod possible done to it. Even for me, I've tried to induce mechanical failure/find limits on cars that I've owned or raced. I had a Swift 1.3L dohc with what is listed as a somewhat unfavorable r/s ratio. Red-line 6750rpm, fuel cut at 7500rpm in north America. With rev-limit removed and stock cams, the engine would reach somewhere around 8500rpms and not make enough power to overcome all the horsepower robbing forces to accelerate the vehicle/increase rpms any further. With a turbo on, I pushed it over 9000rpms before feeling a tad worried that I was probably too far from the garage to be trying it. I even had a wonderful 2nd gear downshift at a good cruising speed and hit a peak of 9800rpms. I'm pretty sure the valves knocked the carbon off the tops of the pistons, but it always drove me home and still wasn't in need a rebuild. It's not a 2JZ, just an example that 700 rpms over the 'makers limits/fuel cut' doesn't fault to - it should blow up. Quote Link to comment Share on other sites More sharing options...
tbourner Posted November 15, 2007 Share Posted November 15, 2007 I think whatthe is asking whether or not anyone here (specifically CW) has had any number of people saying "I've got a rod failure, is it because I'm running at 7500(+) rpm?", because he got an implication from his posts that there is actual evidence of higher rpms causing damage, rather than CW simply saying he doesn't advise it. Quote Link to comment Share on other sites More sharing options...
TLicense Posted December 11, 2007 Share Posted December 11, 2007 I could fairly easily model a stock piston and up, and do an FEA test on it. It's fairly easy to generate what the forces will be on the individual components for given RPM's, then it's pretty easy to see if for the material's that we think they're made from will stand the kind of abuse. It'll be a bit hit and miss due to guestimations with regards to the material and it's properties, but I think we can have an educated guess as types of material's have similar properties and if we're out by a couple of % in terms of say youngs modulus, it's not going to make that big a difference to the failure point. Quote Link to comment Share on other sites More sharing options...
Matt H Posted December 11, 2007 Share Posted December 11, 2007 youngs modulus I didnt think i would ever hear that outside of the class room Quote Link to comment Share on other sites More sharing options...
TLicense Posted December 11, 2007 Share Posted December 11, 2007 lol. Quote Link to comment Share on other sites More sharing options...
Lee P Posted December 11, 2007 Share Posted December 11, 2007 I could fairly easily model a stock piston and up, and do an FEA test on it. It's fairly easy to generate what the forces will be on the individual components for given RPM's, then it's pretty easy to see if for the material's that we think they're made from will stand the kind of abuse. It'll be a bit hit and miss due to guestimations with regards to the material and it's properties, but I think we can have an educated guess as types of material's have similar properties and if we're out by a couple of % in terms of say youngs modulus, it's not going to make that big a difference to the failure point. The standard rob bolts are the main problem at high RPM and horsepower. Would be good to know at what RPM the rod bolts start to fail. Quote Link to comment Share on other sites More sharing options...
TLicense Posted December 11, 2007 Share Posted December 11, 2007 Anyone know what size they are? I'm guessing M8 / M10? If so, using fairly standard bolts you'd be looking at a tensile strength of 47.6kN for M8 or 75.4kN for M10. To make that real for you, 1kN = 1 ton. A decent M10 equivalent NAS bolt (they're generally imperial) then you're looking at about 100kN. If someone know's the stock crankshaft throw, rod length and weight and piston weight then it should be possible to work out how much load is put into the bolts. If it's more than these figures, or approaching near to these figures to allow yourself a factor of safety, then it's going to let go. Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 12, 2007 Share Posted December 12, 2007 Anyone know what size they are? I'm guessing M8 / M10? If so, using fairly standard bolts you'd be looking at a tensile strength of 47.6kN for M8 or 75.4kN for M10. To make that real for you, 1kN = 1 ton. A decent M10 equivalent NAS bolt (they're generally imperial) then you're looking at about 100kN. If someone know's the stock crankshaft throw, rod length and weight and piston weight then it should be possible to work out how much load is put into the bolts. If it's more than these figures, or approaching near to these figures to allow yourself a factor of safety, then it's going to let go. Tony, These are the figures I pulled together in the past - no idea how accurate they are though. Bore x stroke = 86x86 Reciprocating mass (small end plus piston) = 0.4kg (might be a tad light) Rod length = 0.139 I reckon this gives you a maximum inertia load of just over 12kN @ 7000RPM I make the preload from a couple of yeild tightened SAE 10.9 M10x1.25 bolts would be approx 2x40kN, so a 6.6x factor of safety. If someone could get pukka piston and rod masses (weighed seperately) and an idea of the bolt size and thread pitch I could refine this. There's also the bearing crush load to take into account, which will also be working to separate the big end cap from the rod. Quote Link to comment Share on other sites More sharing options...
TLicense Posted December 12, 2007 Share Posted December 12, 2007 Nice one mate. Can you work out the inertia loads at incrementing RPM's? Say from 7000rpm up to 10K in 250 RPM steps? (I know, I know, never happy with what we've got!) Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 12, 2007 Share Posted December 12, 2007 I can certainly do that. In the meantime, if someone could dig around and try to get the correct rod length, piston masses and bolt specs that would be handy, because without them whetever I produce could be total cobblers, tbh. Quote Link to comment Share on other sites More sharing options...
Wez Posted December 12, 2007 Share Posted December 12, 2007 This could be some great info, I hope someone has the info needed to get these figures Quote Link to comment Share on other sites More sharing options...
Ian C Posted December 12, 2007 Share Posted December 12, 2007 I have this stashed from when JamieP weighed his: Stock piston + conrod + rod bolts = 1150grams Alas I didn't get the seperate component weights... -Ian Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 12, 2007 Share Posted December 12, 2007 I have this stashed from when JamieP weighed his: Stock piston + conrod + rod bolts = 1150grams Alas I didn't get the seperate component weights... -Ian I remember that. A golden oppurtunity missed Sadly not much use weighed as a complete assembly. Quote Link to comment Share on other sites More sharing options...
SUPRASUZUKI Posted December 12, 2007 Share Posted December 12, 2007 Come on Digsy, you must have enough benchmark info to be able to apportion a fairly accurate weight to each component. I'd do it myself, but I'm laid up at home!! I assume you're at work? Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 12, 2007 Share Posted December 12, 2007 Come on Digsy, you must have enough benchmark info to be able to apportion a fairly accurate weight to each component. I'd do it myself, but I'm laid up at home!! I assume you're at work? Weeeell, I wanted to be accurate and all that I'll look through a mass rollup and see what I can find. Or you could whip one of yours out and weigh it for me, since you're not doing anything Quote Link to comment Share on other sites More sharing options...
Wez Posted December 12, 2007 Share Posted December 12, 2007 Stock 2JZGTE rod weights from SF :- Rod 1..... 761.0 grams Rod 2..... 757.5 grams Rod 3..... 758.0 grams Rod 4..... 762.0 grams Rod 5..... 762.5 grams Rod 6..... 759.5 grams Quote Link to comment Share on other sites More sharing options...
SUPRASUZUKI Posted December 12, 2007 Share Posted December 12, 2007 Sorry mate, if the wife catches me working in the garage my cover will be blown and I'll have to get back to work or house work. Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 12, 2007 Share Posted December 12, 2007 Ok... A comparable piston weighs 0.313kg If the rod is 0.76kg then and so the small end mass approx 0.25kg. So if the reciprocating mass goes up to 0.313+0.25=0.563kg, then the inertia load would be 17kN Cheers, Wez and Rob Quote Link to comment Share on other sites More sharing options...
Wez Posted December 12, 2007 Share Posted December 12, 2007 Some more 2JZGTE rod weights Carillo H beams : 580g Pauters : 680g Eagle : 594g Crower Titanium : 392g Quote Link to comment Share on other sites More sharing options...
Thorin Posted December 12, 2007 Share Posted December 12, 2007 Crower Titanium : 392g Wow, they're light. Quote Link to comment Share on other sites More sharing options...
SUPRASUZUKI Posted December 12, 2007 Share Posted December 12, 2007 Some more 2JZGTE rod weights Carillo H beams : 580g Pauters : 680g Eagle : 594g Crower Titanium : 392g F^&k me, those Crower's are light! Any idea how they compare strength-wise? Quote Link to comment Share on other sites More sharing options...
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