07_wrex Posted June 20, 2014 Report Share Posted June 20, 2014 Hey guys. I will include my pcl file so you can look at my settings. I would like a softer rpm limit. I initially had it setup per the help file. It was pretty harsh when it hit. I have changed a couple things on this map and would like your thoughts on it. Basically, I see so many cars where you can hold it on the limiter and not really hurt anything. I don't want to destroy valves after a handful of times on the limiter. I'm not planning on holding there by any means, but it is brutal the way it is setup according to the help file. Thanks, Seanclosed deck tune 2 40 psi timingNEW1.pcl Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted June 20, 2014 Report Share Posted June 20, 2014 Hi, I have downloaded your PCL I just had a quick look as I have to go do some dyno work now. May I ask why you want to used the advanced RPM limit mode when the standard rev limit works so well, you just have to put the limit level 250 rpm higher than the rev limit value you wish to use. Regards Dave. Quote Link to comment Share on other sites More sharing options...
07_wrex Posted June 24, 2014 Author Report Share Posted June 24, 2014 I have not tried the standard rpm limit. so, you're saying that it will start fuel cut 250 rpm before the value in the rpm limit table if I don't use advanced? Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted June 24, 2014 Report Share Posted June 24, 2014 Hi yes, 99% of the time just use standard rev limit with fuel % cut. So if you wish to rev the engine and have hard cut at say 7500 rpm then the ECU will soft touch limit the engine approx. 250 rpm lower than your set rev limit value. If I want the engine to rev limit at 7500 rpm I set the limit table to 7750 rpm, soft cut will cut in at 7500 and if you keep pushing hard the full cut will activate at 7750. But the soft cut is quite effective and you can definitely feel it. This type of setup is by far a lot kinder to the turbocharger. Regards Dave. Quote Link to comment Share on other sites More sharing options...
07_wrex Posted June 24, 2014 Author Report Share Posted June 24, 2014 Thanks Dave, Would you suggest a longer soft-hard cut window on an engine making 800 whp? Sean Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted June 25, 2014 Report Share Posted June 25, 2014 Hi Sean, at the end of the day the REV LIMITER is there to serve a purpose, it is to help save the engine. The way I see it as soon as rev limit is active you shift gear or back off. It is amazing (not referring to you in anyway) how many people out there think that holding an engine on a rev limiter or boost cut is safe. It couldn't be further from the truth, fuel cut limiters lean the engine out, ignition cut limiters can destroy turbos, but can also damage big end bearings ,main bearings, pistons etc. So in a perfect world when one sees the shift light come on or the limiter kick in , then BACK OFF or CHANGE GEARS. Extending limiting times etc on 100 HP or 5000 HP really ends up with the same consequences at the end of the day, if the limiter is abused , then the engine ultimately gets abused. Regards Dave. Quote Link to comment Share on other sites More sharing options...
07_wrex Posted June 25, 2014 Author Report Share Posted June 25, 2014 Dave, Ya. I figured. Just checking. I haven't really looked at any other manufacturers setup on rpm limits. The car has seen the limiter maybe only a few times. The reason for this thread is that I recently had a super tech stainless intake valve just decide to break while I was cruising. No boost and not getting on it. It destroyed my 1400 mile closed deck short block. Most likely beyond repair. I will definitely be going with another brand of valve. I just want to make sure I didn't cause this with my tune. I'm 99% sure it's just a bad valve. I documented the long block tear down and it didn't jump time or anything like that. I really don't want to spend another $9,000 just to have it happen again in 1400 miles. lol. Thanks, Sean Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted June 25, 2014 Report Share Posted June 25, 2014 Hi , unusual for an inlet valve to go. Could be bad production. The only time I have seen an inlet valve failure was in a customers 555 cu/in twin turbo ski boat race engine, these engines run over 0.850 thou lift roller camshafts with like 750 -800 lbs on the nose of the cam spring pressure.. These engines normally run at 5800 - 6800 rpm for 40 mins plus with anything from 7 psi to 18 psi depending on the load. So one can understand valve failures in these cases. But strange for what has happened to you. Retainer and collets ok, or valve has just snapped. Did it break on the stem or did the valve head break off. Regards Dave. Quote Link to comment Share on other sites More sharing options...
07_wrex Posted June 26, 2014 Author Report Share Posted June 26, 2014 Hi Dave, Ya, that's understandable. Sounds like a fun ride though! Here's a couple pictures. The valve broke off in the middle of the stem somewhere. The valve head I'm holding has been beat up and 4 3/16" pieces of stem were later found in the oil pan. I assume from punching through the piston. Everything on the top side of the head looks great. Springs, retainers, buckets (shims for a subaru), cam, and cam journals all look good. I thought I'd find the timing belt destroyed for something like this to happen after 1400 miles. Or at least some other issue that might cause this. Timing belt was fine and the engine was still in time when I took it apart. I'm sure it was just a bad batch since I can't find any reason why it would fail like that. I don't rev the car to their (supertechs) recommended rpm limit of 9500...or anywhere near that. Sean Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted June 26, 2014 Report Share Posted June 26, 2014 Ouch, could be faulty valve manufacture. But I would also check the valve to valve guide clearances. Remembering that these things get hot, not as hot as the exhaust, but they still need the correct clearances. Check all valve stem to guide clearances on all valves. Just to be sure. I would also replace all of the valves to a different brand to be safe. Regards Dave. Quote Link to comment Share on other sites More sharing options...
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