VCT or VVT 5.7L
04-11-2009, 07:03 PM
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VCT or VVT 5.7L
When I got my 09 R/T 6spd I thought the engine had variable cam timing....now the dodge website lists VCT for autos and variable valve timing for the 6 spd...has something changed or have all 6spd r/ts been VVT?
This car is by far the best one made today. It is such a joy to drive. Here in Middle GA I get so many compliments...only seen 2 others, one SRT and an SE. The only thing I don't like is the skip shift...doesn't seem right to have a computer determine manual shifting.
This car is by far the best one made today. It is such a joy to drive. Here in Middle GA I get so many compliments...only seen 2 others, one SRT and an SE. The only thing I don't like is the skip shift...doesn't seem right to have a computer determine manual shifting.
04-12-2009, 02:56 AM
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Go to E-bay and get the skip shift eleminator. Easy to install. Just an unplug and a replug. 5 minutes tops. For $20.00 its the best mod yet. OK the Diablo is the best mod yet.
04-17-2009, 06:48 PM
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I just ordered an R/T Classic thursday with automatic and the printout listed the 5.7 w/auto as a VVT? Brochure shows same as VCT! Who knows? I just wonder if the car will ever be built?
04-21-2009, 07:16 PM
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They both have VVT for 09 with 5.7
The automatic also has the MDS . Think that's right. Where it will drop back to 4 cylinder's above 60 mph cruising . A Chrysler engineer said the reason the 6 spd does not . Is because they couldn't compute what gear the trans would be in as with the computer controled automatic. So the 6 speed engine run's on 8 all the time . And that was the answer to that question in Hot Rodding by the Chrysler engeener . I have a 300C automatic that does run on the 4 sometime. I'm happy with my R/T running on 8 and get better gas mileage than my wife's car most of the time.
Last edited by KyChallengerR/T6spd; 04-21-2009 at 07:21 PM. Reason: wording
09-24-2009, 05:42 AM
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The automatic also has the MDS . Think that's right. Where it will drop back to 4 cylinder's above 60 mph cruising . A Chrysler engineer said the reason the 6 spd does not . Is because they couldn't compute what gear the trans would be in as with the computer controled automatic. So the 6 speed engine run's on 8 all the time . And that was the answer to that question in Hot Rodding by the Chrysler engeener . I have a 300C automatic that does run on the 4 sometime. I'm happy with my R/T running on 8 and get better gas mileage than my wife's car most of the time.
If it's only supposed to ingauge at 60 mines broke. Mine will ingauge at 20MPH if I'm just cruising down the street.
09-25-2009, 01:38 PM
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I don't know precisely what Chrysler's abbreviation for their variable cam phasing system is, but all '09 and newer 5.7 HEMIs have it, period. The automatic-equipped cars also get MDS (part-time 4 cylinder mode), a worthy attempt to compensate somewhat for the mileage penalty you pay for a conventional automatic vs a 6-speed manual. The '09 and newer MDS is programmed more aggressively (it activates more often than it used to), so you'll see it activate at lower speeds and at greater throttle openings than was previously the case. Hope this helps...
Last edited by 1analguy; 09-26-2009 at 12:17 AM.
09-26-2009, 12:05 AM
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I can't comment on the '09 Challenger automatic's gage setup as I don't know anyone that has an automatic. However, my brother has an '09 300 and when his MDS activates, it says "ECO" in the display briefly in the same way that a 6-speed owner will see "1st to 4th" briefly in the display when the skip shift mechanism is active...
Last edited by 1analguy; 09-26-2009 at 12:18 AM.
10-08-2009, 04:19 PM
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VCT is a form of VVT from what I understand. The VCT can be had with either manual or automatic, it's MDS that's the difference.
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12-20-2009, 09:41 PM
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VCT and VVT are the same thing. I refer to the 5.7s "VVT" system as Variable Cam Phasing because it varies the position (phasing) of the entire (one-piece) cam in relation to the crankshaft. Since this relationship is what determines the valve timing for the engine, varying the relationship between cam and crank (variable cam phasing) results in "variable valve timing". The system on the Viper V10 is a bit more sophisticated, in that the Viper cam is actually in two pieces. The intake and exhaust events are independent of one another and are each varied independently of the other, and both varied in relation to the crankshaft. JMO, but it seems more proper to me to refer to this system as true VVT...