Jardim Posted May 22, 2012 Report Share Posted May 22, 2012 If the fuel was cut, the engine should stop revving higher. The question then is did the ECU simply not respond to the rising RPMs quickly enough, or did it not cut at all? I would expect a significant change in EGT and AFR if it did actually cut. That is quite possible, 20 psi on a large turbo + sudden slip of clutch/no connectivity to drivetrain could cause the revs to "teleport" north. 4 Quote Link to comment Share on other sites More sharing options...
Captain Bondo Posted May 22, 2012 Report Share Posted May 22, 2012 That is quite possible, 20 psi on a large turbo + sudden slip of clutch/no connectivity to drivetrain could cause the revs to "teleport" north. No. Just no. The engine won't "teleport" from 8400rpm to 9600rpm magically. The fact that apparently no one here even grasps what happens when you cut the fuel to an engine... there's just no facepalm that's even sufficient. 3 1 Quote Link to comment Share on other sites More sharing options...
Jardim Posted May 22, 2012 Report Share Posted May 22, 2012 Um, then you go drive your car at WOT and put the clutch down while holding down the gas and see your revs climb 1200 rpms slower than it normally would with the clutch engaged.........-__-And you cant grasp what happens when the fuel gets cut to the engine in this case, cause it didnt happen. 1 3 Quote Link to comment Share on other sites More sharing options...
mdlimy Posted May 22, 2012 Report Share Posted May 22, 2012 No. Just no. The engine won't "teleport" from 8400rpm to 9600rpm magically. The fact that apparently no one here even grasps what happens when you cut the fuel to an engine... there's just no facepalm that's even sufficient. i agree, dont think i would ever consider using fuel cut by itself as my primary way of limiting revs. either way, the ecu didnt limit the revs, for what ever the reason. Sure the clutch slipping would let it climb quicker in the rpms than if it was grabbing but thats why we have rev limiters, if its not going to function when you need it the most whats the point in having it. im sorry but H, your car just keeps proving to me that TT sucks lol. Your car is going to rip on the vems at 9k rpm :tup: 1 1 Quote Link to comment Share on other sites More sharing options...
dublin14 Posted May 22, 2012 Report Share Posted May 22, 2012 (edited) i agree, dont think i would ever consider using fuel cut by itself as my primary way of limiting revs. either way, the ecu didnt limit the revs, for what ever the reason. Sure the clutch slipping would let it climb quicker in the rpms than if it was grabbing but thats why we have rev limiters, if its not going to function when you need it the most whats the point in having it. im sorry but H, your car just keeps proving to me that TT sucks lol. Your car is going to rip on the vems at 9k rpm No doubt a standalone is the best choice for any of us running big turbos, but I have Turbo Tuner with a 50 trim - 630cc injectors - and I have to say it doesnt (suck). I also have my rev limiter set at 7400rpm and its worked anytime Ive hit it. Any adjustments made have worked great. For getting the most out of a big Turbo setup and running 20+psi, Turbo Tuner isnt the best choice... but then again its working with a 4.4M ECU. Really TT works great for guys with OEM turbos that want to custom tune or dyno tune - The big turbos like Hussein`s 6262 VEMS - MS ect is the best option of course. Edited May 22, 2012 by dublin14 1 2 Quote Link to comment Share on other sites More sharing options...
blkaplan Posted May 22, 2012 Report Share Posted May 22, 2012 Really TT works great for guys with OEM turbos that want to custom tune or dyno tune - The big turbos like Hussein`s 6262 VEMS - MS ect is the best option of course. MS is getting to be a pretty solid option but I wouldn't consider it the best, there are other products out there like some of the AEM and motec units that I would call "best" Quote Link to comment Share on other sites More sharing options...
dublin14 Posted May 22, 2012 Report Share Posted May 22, 2012 MS is getting to be a pretty solid option but I wouldn't consider it the best, there are other products out there like some of the AEM and motec units that I would call "best" Thats why I said VEMS- MS ect... 1 2 Quote Link to comment Share on other sites More sharing options...
Jardim Posted May 22, 2012 Report Share Posted May 22, 2012 Motec is the stuff you want, but you better be ready to spend some cash. Quote Link to comment Share on other sites More sharing options...
lookforjoe Posted May 22, 2012 Author Report Share Posted May 22, 2012 No. Just no. The engine won't "teleport" from 8400rpm to 9600rpm magically. The fact that apparently no one here even grasps what happens when you cut the fuel to an engine... there's just no facepalm that's even sufficient. Well I guess I'm just stupid then. You still haven't indicated how any rev limiter (on a Motronic ECU) is going to restrict the engine from free- revving if the clutch slips under load as mine did. As far as I can see, there is nothing that will prevent the engine from continuing to rev if the throttle is held open even for an instant once the clutch is no longer engaged. I hope the tear-down will indicate what is going on with the clutch slippage, disengagement issues, and what appear to be bearing particles in the oil. As far as I can see, the upper end failure is from over-revving, the lower end, I dunno. I'm still working on the VEMS ECU wiring. Having to rebuild the engine again is only going to delay that further. Quote Link to comment Share on other sites More sharing options...
lookforjoe Posted May 22, 2012 Author Report Share Posted May 22, 2012 Since it rained all day yesterday, I worked some on the ECU wiring now I just have to solder these to the VEMs board, bridge the coil circuits, then figure out all the software parameters.... I also have to get the cam tool I bought cut & rewelded - they weren't to careful about keeping both pieces parallel to the blocks Quote Link to comment Share on other sites More sharing options...
sconeman Posted May 22, 2012 Report Share Posted May 22, 2012 (edited) I wonder if that's why my exhaust cam was out of alignment after I used a similar tool... "I also have to get the cam tool I bought cut & rewelded - they weren't to careful about keeping both pieces parallel to the blocks Edited May 22, 2012 by sconeman Quote Link to comment Share on other sites More sharing options...
lookforjoe Posted May 22, 2012 Author Report Share Posted May 22, 2012 I wonder if that's why my exhaust cam was out of alignment after I used a similar tool... Probably - that's enough to retard the exhaust several degrees (early) relative to the intake - is yours also the "KTC" set? Quote Link to comment Share on other sites More sharing options...
sconeman Posted May 22, 2012 Report Share Posted May 22, 2012 I'd have to look, I bought it off ebay last year for about $200 Quote Link to comment Share on other sites More sharing options...
fischmama Posted May 22, 2012 Report Share Posted May 22, 2012 Well I guess I'm just stupid then. You still haven't indicated how any rev limiter (on a Motronic ECU) is going to restrict the engine from free- revving if the clutch slips under load as mine did. As far as I can see, there is nothing that will prevent the engine from continuing to rev if the throttle is held open even for an instant once the clutch is no longer engaged. I hope the tear-down will indicate what is going on with the clutch slippage, disengagement issues, and what appear to be bearing particles in the oil. As far as I can see, the upper end failure is from over-revving, the lower end, I dunno. I'm still working on the VEMS ECU wiring. Having to rebuild the engine again is only going to delay that further. If I remember correctly Motronic uses Spark cut as its rev limiter, maybe fuel cut as a secondary hard limiter. Not sure if thats still the case with TT. I can see that the engine can maybe go 100-200 RPM past that but when spark is cut (and fuel) the engine will not rev higher (unless the fuel self ignites which it shouldn't). I have three limiters set on MS and they all work and won't let me over rev the engine. I have a soft limiter that retards timing, then spark cut and fuel cut after that. It never gets to the fuel cut limiter. Please correct me if I'm wrong but thats how I remember Motronic to handle the rev limiter. 1 1 Quote Link to comment Share on other sites More sharing options...
Captain Bondo Posted May 22, 2012 Report Share Posted May 22, 2012 Well I guess I'm just stupid then. You still haven't indicated how any rev limiter (on a Motronic ECU) is going to restrict the engine from free- revving if the clutch slips under load as mine did. As far as I can see, there is nothing that will prevent the engine from continuing to rev if the throttle is held open even for an instant once the clutch is no longer engaged.. You've gotta be shitting me. You seriously can't grasp that even free revving, if an engine is revving up, hits 8400rpm, and fuel is cut, If I remember correctly Motronic uses Spark cut as its rev limiter, maybe fuel cut as a secondary hard limiter. Not sure if thats still the case with TT. I can see that the engine can maybe go 100-200 RPM past that but when spark is cut (and fuel) the engine will not rev higher (unless the fuel self ignites which it shouldn't). I have three limiters set on MS and they all work and won't let me over rev the engine. I have a soft limiter that retards timing, then spark cut and fuel cut after that. It never gets to the fuel cut limiter. Please correct me if I'm wrong but thats how I remember Motronic to handle the rev limiter. Exactly. The flywheel does have some inertia, so in some cases it could be possible to get a 100-200rpm bump post-fuel cut - but it takes actual ENERGY input to accelerate the crankshaft, pistons, etc.In fact it takes energy even to hold them at a constant rpm. When you cut the fuel, it's like switching the key off. The engine speed is not going to continue to rise 1200rpm. I won't call you stupid, but if you actually think that the engine speed could continue to rise that much after cutting the fuel... you definitely don't have your head wrapped around the dynamics involved. 2-step rev limiters don't even cut fuel or spark completely, and they are able to hold an engine at a fixed rpm, they don't way overshoot. That would be ridiculous. Rev limiters in general would be basically pointless. When you cut the fuel, it's like hitting a wall. 4 Quote Link to comment Share on other sites More sharing options...
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