VVT motor with T-56 bad idea ??
02-08-2012, 02:59 AM
#1
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VVT motor with T-56 bad idea ?? Friend of mine who knows engines pretty well and is in his late 40's gave me some info in his opinion.
I'm just looking to bounce it off people here who know the VVT motors to give a solid accurate answer.
We were discussing the 2010 SS Camaro 1/4 mile speeds of the manual VS auto.
L99 Auto with 400hp being the same as the
LS3 6 speed manual with 426hp.
I'm putting a LY6 / T-56 into my 442 already, and he just said this to me yesterday.
Is this seriously something I need to worry about ??
True, or not true ??
I'm just looking to bounce it off people here who know the VVT motors to give a solid accurate answer.
We were discussing the 2010 SS Camaro 1/4 mile speeds of the manual VS auto.
L99 Auto with 400hp being the same as the
LS3 6 speed manual with 426hp.
I'm putting a LY6 / T-56 into my 442 already, and he just said this to me yesterday.
Is this seriously something I need to worry about ??
You DON'T want to do that. (put VVT motor with T-56)
Reason --- piston to valve clearance issues with the VVT. it is WHY most VVT cams have low lift. Power band is in the duration
however so it makes up for the low lift with lots of advance down low and lots of retard up high in RPM. Stick a maunal trans into
that equation and you could be tapping an intake valve off a piston @ 6000 RPM.
Too many downsides to VVT/manual, that's why neither GM nor Dodge have VVT with the manuals. Gotta be something to it
if they engineer TWO different engines, one for manual, one for auto, the diff betweem primarily VVT (and MDS, but that's not
sometrhing you'd be doing with your build.)
Reason --- piston to valve clearance issues with the VVT. it is WHY most VVT cams have low lift. Power band is in the duration
however so it makes up for the low lift with lots of advance down low and lots of retard up high in RPM. Stick a maunal trans into
that equation and you could be tapping an intake valve off a piston @ 6000 RPM.
Too many downsides to VVT/manual, that's why neither GM nor Dodge have VVT with the manuals. Gotta be something to it
if they engineer TWO different engines, one for manual, one for auto, the diff betweem primarily VVT (and MDS, but that's not
sometrhing you'd be doing with your build.)
02-08-2012, 06:30 AM
#2
If you're doing a stock swap, those concerns might be well founded, but because GM also warranies their vehicles, they can't afford anything without a wide margin of error.
Don't try to build a vvt rpm screamer
Do put in the mechanical limiter in the cam phaser
Do put in better valve springs
Try to use light weight rotating and valve train components
Do check PV and replace or fly cut the piston reliefs
I'm putting a vvt L99 and T56 into a 92 vette and am concerned but am not being blind to the issues.
Don't try to build a vvt rpm screamer
Do put in the mechanical limiter in the cam phaser
Do put in better valve springs
Try to use light weight rotating and valve train components
Do check PV and replace or fly cut the piston reliefs
I'm putting a vvt L99 and T56 into a 92 vette and am concerned but am not being blind to the issues.
02-08-2012, 11:41 AM
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I'm doing the same thing, & have had the same concerns. On the flip side however, I also figured that both Mast Motorsports & Comp Cams have reasonably intelligent people who have done a fair bit of engineering to ensure that their products work with these engines, even if their use is "extended" a bit beyond the normal truck operating range.
A few months ago, I saw a magazine article (don't remember which magazine) that featured a mid-60s Chevelle with an L92/T56 combo, so I tracked down the owner & asked him about it, & here's what he had to say:
Finally, I've asked a couple of people who (I believe) have industry connections if they might be able to get the straight scoop regarding VVT + manual transmissions, so far I haven't heard anything back yet. I think it's about time for me to bug 'em about it again...
A few months ago, I saw a magazine article (don't remember which magazine) that featured a mid-60s Chevelle with an L92/T56 combo, so I tracked down the owner & asked him about it, & here's what he had to say:
When I was looking at buying the L92 with VVT someone told me that Stacy Tucker (Detroit Speed) had it on her 69 Camaro. So, I called up Kyle and asked him what they thought of it. He said they were very happy with it and it made great torque at basically all RPM's. Of course, she showed up at the start of this season with a different engine without VVT, so I don't know what that says... I also called Mast Motorsports since I planned to use their cam and control package and they convinced me that they had it well sorted. They did and it ran very well as soon as we fired it up. The only issue I had with their program was that it seemed to carry RPM's when I let off the throttle at higher RPM's which really sucked when autocrossing. But, I recently had Mike Norris do a dyno tune on it and although he said he couldn't get much more power out of it, he was able to sort that problem out. So, with all that said, we are thrilled with the way the car runs with the VVT. As a matter of fact, we have about 5K miles on the Chevelle with the L92 now and recently won the Goodguys auto-x in Charlotte. We did nothing to connect the T56 to the ECM so it doesn't even read MPH's. That might change if Mast comes up with a cruise control system in the future.
Finally, I've asked a couple of people who (I believe) have industry connections if they might be able to get the straight scoop regarding VVT + manual transmissions, so far I haven't heard anything back yet. I think it's about time for me to bug 'em about it again...
02-08-2012, 12:17 PM
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I wouldn't see why vvt/t56 wouldn't work left alone, put some higher # valve springs just for ease of mind, Honda bump off rev limiter at 8000 rpm s2000 at 9000 both stock and its a variable valve timing motor. just about every manufacturer has a manual trans with vvt motors.missing a shift might damage any motor, just with vvt its usually tighter piston to valve clearance at higher rpms, float a valve and motor might be done.
02-08-2012, 12:27 PM
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Originally Posted by Nissan LS240
I wouldn't see why vvt/t56 wouldn't work left alone, put some higher # valve springs just for ease of mind, Honda bump off rev limiter at 8000 rpm s2000 at 9000 both stock and its a variable valve timing motor. just about every manufacturer has a manual trans with vvt motors.missing a shift might damage any motor, just with vvt its usually tighter piston to valve clearance at higher rpms, float a valve and motor might be done.
02-08-2012, 01:11 PM
#6
I think the reason they use VVT+Auto on the OEMs is the auto sucks away some fuel economy and potentially adds to emissions, so the VVT can offset that. Meanwhile the manuals save money by eliminating the VVT.
Performance wise, why would you be any more concerned about valve float or PTV issues on a manual than an auto? A manual might change RPMs faster, but valve float is caused by RPM not change or rate of change in RPM. Take a manual from idle to 6000rpm or take an auto from idle to 6000rpm, the potential for valve float should be about the same IMO.
They make phaser limiters for a reason.
Performance wise, why would you be any more concerned about valve float or PTV issues on a manual than an auto? A manual might change RPMs faster, but valve float is caused by RPM not change or rate of change in RPM. Take a manual from idle to 6000rpm or take an auto from idle to 6000rpm, the potential for valve float should be about the same IMO.
They make phaser limiters for a reason.
02-08-2012, 09:04 PM
#7
Agreed - that's why I think that 85MikeTPI's suggestions are good advice. I'm going to try to replace at least my intake valves with lighter-weight units, step up to better springs & retainers, use the cam phaser limiter, & have a "hard" rev-limiter programmed in, and I think I should be in pretty good shape. (If not, well, that's a good excuse to build that 400+ cid stroker...!!)
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02-08-2012, 09:11 PM
#9
02-08-2012, 09:13 PM
#10
I wouldn't see why vvt/t56 wouldn't work left alone, put some higher # valve springs just for ease of mind, Honda bump off rev limiter at 8000 rpm s2000 at 9000 both stock and its a variable valve timing motor. just about every manufacturer has a manual trans with vvt motors.missing a shift might damage any motor, just with vvt its usually tighter piston to valve clearance at higher rpms, float a valve and motor might be done.
02-09-2012, 05:52 AM
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Sounds like he didn't have any issues with the VVT and Manual.
More or less issues with his factory speedo and tach.
But the stronger springs would probably be a solid idea.
02-09-2012, 09:58 AM
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I didn't say rev the LS to 8000, just saying other manufacturer's rev their vvt motors at a higher rpm, and I rev my LS to 7600, not stock internals, well not stock anything.
02-09-2012, 10:02 AM
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Performance wise, why would you be any more concerned about valve float or PTV issues on a manual than an auto? A manual might change RPMs faster, but valve float is caused by RPM not change or rate of change in RPM. Take a manual from idle to 6000rpm or take an auto from idle to 6000rpm, the potential for valve float should be about the same IMO.
They make phaser limiters for a reason.
They make phaser limiters for a reason.
02-09-2012, 10:33 AM
#15
That makes sense. Thanks for explaining. If the phaser fails to hold the cam, it is going to hit the phaser limiter and I don't think that would cause any additional float or clearance issues, but I could be wrong. It certainly adds a variable to be considered.
02-09-2012, 05:05 PM
#17
"Piston to valve clearance = the reason for low lift"?? NOPE! That's actually because of the constraints of the lifter and its design, not piston to valve clearance.
Let her eat
We've got quite a few customer running the LY6 in swaps (because they're inexpensive) with a T56 (because they're common, inexpensive, and everyone wants to row gears in their swap cars for the most part) and they all love it!
Let her eat
We've got quite a few customer running the LY6 in swaps (because they're inexpensive) with a T56 (because they're common, inexpensive, and everyone wants to row gears in their swap cars for the most part) and they all love it!
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Someone local please trade me my TH400 with 2800rpm BTE stall and TCI flexplate for a T56. Please?
02-11-2012, 09:46 AM
#19
02-11-2012, 10:06 AM
#20
[QUOTE=-TheBandit-;15943431]Those are low volume vehicles with forced induction. They spent their money on the huffer. By comparison VVT has very little gain to offer over a supercharger and complicates development, so I can see why they left it off the list. I don't know that it had to do with the manual tranny. But I could certainly be wrong.
Well, then what about the LS7 and LS3? I don't think it has to do with the manual tranny either.
I think it would be a good idea to swap to the T56. I might get shot for saying this on this forum, but I trully believe (from my experience) that going from a th400 to a T56 will transform the car more than the LS swap. I simply would not enjoy mine as much or as often without overdrive, and if I was banging gears I would enjoy my car even more. A TH400 is better for a dragster, but thats about it.
Also, I hope you prove me wrong on this, but I think the biggest gain you're going to see in keeping your vvt will be in fuel efficiency, and that will be harder to appreciate with the th400 and 3.73. You really have so much to gain with a t-56.
Well, then what about the LS7 and LS3? I don't think it has to do with the manual tranny either.
I think it would be a good idea to swap to the T56. I might get shot for saying this on this forum, but I trully believe (from my experience) that going from a th400 to a T56 will transform the car more than the LS swap. I simply would not enjoy mine as much or as often without overdrive, and if I was banging gears I would enjoy my car even more. A TH400 is better for a dragster, but thats about it.
Also, I hope you prove me wrong on this, but I think the biggest gain you're going to see in keeping your vvt will be in fuel efficiency, and that will be harder to appreciate with the th400 and 3.73. You really have so much to gain with a t-56.