JamieP Posted July 5, 2008 Share Posted July 5, 2008 Out of interest why is a "built engine" stronger? ive never heard of a stock rod snapping etc? i understand an after market piston may be more resistant to det but if its mapped properly i cant see an issue. I also understand that lighter parts will make it rev easier but that has nothing to do with strength. Thoughts? Quote Link to comment Share on other sites More sharing options...
tooquicktostop Posted July 5, 2008 Share Posted July 5, 2008 When I was going through the rebuild thought process Jamie I asked a lot of questions and if I had gone small single I would have stayed with a new short block with stock internals (as Lui did) I went for the bigger power option and was advised that the weakest link in the Supra bottom end is the rods and rod bolts, I went Brian Crower in the end with ARP bolts, they are a lot lighter than stock giving the engine a much improved rev response The head is a different matter of course Quote Link to comment Share on other sites More sharing options...
Kranz Posted July 5, 2008 Share Posted July 5, 2008 A built engine is blueprinted and normally uses better components that are stronger, lighter and therefore have a higher rev limit The blueprinting means that the engine is more efficient, less wasted power through friction and EVERYTHING is individually measured to fit & suited to the purpose. Things like the microns of depth of the hone and its angle are specified to suit the piston rings, which themselves are of a material, shape and width all to suit the intended puropse (i.e. drag racing, endurance racing etc). Quote Link to comment Share on other sites More sharing options...
JamieP Posted July 5, 2008 Author Share Posted July 5, 2008 Anyone on here have a rod bolt snap? Quote Link to comment Share on other sites More sharing options...
tooquicktostop Posted July 5, 2008 Share Posted July 5, 2008 Anyone on here have a rod bolt snap? Only one I can find and it was a long time ago at 2 bar http://www.mkivsupra.net/vbb/showthread.php?t=29342&highlight=snapped+rod+bolt Quote Link to comment Share on other sites More sharing options...
jevansio Posted July 5, 2008 Share Posted July 5, 2008 You'll probably also find when people go single it's on a 10+ year old engine, if it needs rebuilding anyway there's probably not a great deal of difference price wise between new OEM & aftermarket parts, so people probably think why not go for the added weight benefit Quote Link to comment Share on other sites More sharing options...
Kranz Posted July 5, 2008 Share Posted July 5, 2008 They should only snap if over revved, or too many cycles at high revs (i.e. sitting at max revs for over 200 hours or whatever the industry standard test is) . The problem with rod bolts and rods comes when the power band is moved up the rev range and the engine is operating at a higher power and in a rev band it was not designed for. The structure & materials are specced to withstand the standard rev & power limit. Going higher with both will shorten the life of the components, sometimes dramatically! Quote Link to comment Share on other sites More sharing options...
Muffleman Posted July 5, 2008 Share Posted July 5, 2008 Totally agree, when having mine rebuilt I opted for all new toyota parts including water, oil pump etc. The only deviation was forged pistons. The engine was blue printed and built properly. I have yet to see any evidence that would suggest the need for aftermarket parts over new toyota parts in a new build. I think Envy had an end cap fail at 2bar or something ? As Jay says, if you single a 10yo car then something may fail, but new parts are fine. I opted for Toyota parts as I suspect they would be manufactured to better tolerances and specifications than aftermarket parts, plus the R&D into stock parts is far greater than non-stock. Just my opinion Quote Link to comment Share on other sites More sharing options...
Kranz Posted July 5, 2008 Share Posted July 5, 2008 Only one I can find and it was a long time ago at 2 bar http://www.mkivsupra.net/vbb/showthread.php?t=29342&highlight=snapped+rod+bolt 2.1 bar at 7200 rpm would do it Round about 8000 will kill the rod bolts for the stock power output if the rev limit is removed. Rev limit is supposed to be 6850 LOL Quote Link to comment Share on other sites More sharing options...
JamieP Posted July 5, 2008 Author Share Posted July 5, 2008 Only one I can find and it was a long time ago at 2 bar http://www.mkivsupra.net/vbb/showthread.php?t=29342&highlight=snapped+rod+bolt Nice read but its not 100% bolt failure, could have been anything imo. Quote Link to comment Share on other sites More sharing options...
Kranz Posted July 5, 2008 Share Posted July 5, 2008 Nice read but its not 100% bolt failure, could have been anything imo. Could have been anything that led to rod bolt failure, as the rod bolts are the weak link in the system. Crank flex (whip) caused by the massive cylinder pressures at a specific (harmonic) rpm could have caused bolt failure. Probably a good idea as Matt said is to use NEW components such as rod bolts. Crack test, lighten and microbalance the crank, con rods, flywheel, damper and pistons; blueprint the engine and ensure all clearances are suitable for the rev limit. Also replace the weak link components at a specified interval, such as rod bolts at say 50k miles? When thay're replaced have them measured for stretch Vs the installed (torqued up) length and crack tested etc. Good insurance Quote Link to comment Share on other sites More sharing options...
rob wild Posted July 5, 2008 Share Posted July 5, 2008 I would have though that the only reason you would choose an after market part is if the OEM is not to that spec? I.e if your running high boost and higher rev limit then obviously your creating more friction = heat which would be above the OEM parts specification. Therefore perhaps using for example a forge pistons that is designed to take the extra heat be the right way to go. Just thinking of a practical example with my own car and Ryan stopping at 1.4bar because the EGT's were getting above 950c which it we had pushed it to say 1.5/6bar to egt would have been to high and the oem pistons would have failed. On a different note it would great to have mkivsupra.net R&D car were we could test things like this Quote Link to comment Share on other sites More sharing options...
Wez Posted July 5, 2008 Share Posted July 5, 2008 2.1 bar at 7200 rpm would do it Round about 8000 will kill the rod bolts for the stock power output if the rev limit is removed. Rev limit is supposed to be 6850 LOL Isnt 7200rpm the stock rev limit of the VVTI which has the same bottom end I rev mine to 7200rpm, I did have it set at 7500rpm for a while but turned it back down to 7200rpm EDIT: some Mines ECUs raise it to 8000rpm. Quote Link to comment Share on other sites More sharing options...
Kranz Posted July 5, 2008 Share Posted July 5, 2008 Possibly, I'm not well versed on the VVTI. But the VVTI doesn't run 2.1 bar at 7200 I'd expect it to have quite low power on the limiter by comparison. There are some calcs you can do to determine the max rpm of a certain con rod & bolt specification. I don't have them to hand.... I think they're in a book I gave to Ian C Quote Link to comment Share on other sites More sharing options...
bondango Posted July 5, 2008 Share Posted July 5, 2008 (edited) There are some calcs you can do to determine the max rpm of a certain con rod & bolt specification. I don't have them to hand.... I think they're in a book I gave to Ian C Performance Tuning in Theory and Practice, by A.G.Bell? If not, this is defo worth a read too. Especially for anyone wanting to know about engine survivability. things like Piston Speed, bearing speed vs max rpms are worth reading up on to see the effects on stock vs after market crank/conrod components etc etc An example calculation on the standard 2jzgte engine stroke Stock component engines: cast iron crankshaft, stock connecting rods, stock cast pistons Stroke:3.39 Inches Mean Piston Speed:3500 Feet per Minute Result: 6194 Max RPM Heavy duty engines: forged or nodular iron crankshaft, shot peened connecting rods, forged pistons Stroke:3.39 Inches Mean Piston Speed:4000 Feet per Minute Result: 7079 Max RPM Racing/Performance engines: forged crankshaft, high strength alloy rods, high strength alloy pistons Stroke:3.39 Inches Mean Piston Speed:5000 Feet per Minute Result: 8849 Max RPM Edited July 5, 2008 by bondango (see edit history) Quote Link to comment Share on other sites More sharing options...
AndyT Posted July 5, 2008 Share Posted July 5, 2008 I think Kranz is our new Ian C. Keep it coming. Just my observations. The stock components are designed to take twice the power generated. CW has never found a big end bolt stretched. Those bolts are either designed to stretch ie you torque 'em up to fit a designed gauge, or they snap. Nothing in between. OEM are over engineered and as Matt states R &D'ed much more than aftermarket stuff. Good read up on the blue printing though, explains why it's so darn expensive. Quote Link to comment Share on other sites More sharing options...
jevansio Posted July 5, 2008 Share Posted July 5, 2008 I have one question, is it black & white to say OEM is better than aftermarket just because Toyota make them? It depends on which aftermarket manufacturer you're comparing them to, take Jun pistons for instance, made by Cosworth, are we saying Toyota have as much R&D in their 2JZ pistons as Cosworth do (taking into account that although the Supe is a performance car, the 2JZ was taken from their luxury cruiser the Aristo)? Quote Link to comment Share on other sites More sharing options...
bondango Posted July 5, 2008 Share Posted July 5, 2008 (edited) You gotta remember too that the 2jz engine (ref. head+block) was basically a larger capacity 1jz (which was introduced in 89 but amazingly has few interchangable parts between the two) so i doubt there was much R&D in comparison to a "new" engine design. With Regards to OEM vs After market though - Technology and manufacturing processes have advanced a lot in the last 15 years, Toyota stopped their R&D process on the 2jz a long long time ago, but JUN and HKS for example are still continuing with theres, so there lies a strong argument there. Edited July 5, 2008 by bondango (see edit history) Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.