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  1. #1
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    Default About VVTI engine and how to control VVTI

    There was a diskution about VVTI, and the engine did not make good powerband if you didnt make it varibel.
    We did test using stock ECU, and with megasquirt.
    We made the megasquirt control the VVTI like normal VVT.
    As you se on dyno, it made better powerband with the megasquirt contoling the VVTI.
    This was after only 15min tuning on road.

    Just info, many give up when they hear VVTI, thinking you cant control it.



    Last edited by Toyota T23; 29-12-2007 at 10:42 AM.

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    Nice, what car and engine is this?

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    Quote Originally Posted by NDR008 View Post
    Nice, what car and engine is this?

    It is a MR2 with 3SGE VVTI BEAMS engine

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    Registered Trader www.TuningDevelopments.co.uk Nick@TD.co.uk's Avatar
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    Turbo'd VVTI engine is what is needed, you get awesome power out of VVTI engines if forced induction is added just need people brave enough to do it.
    Tuning Developments Ltd - Stri-Racing UK - 01925 822 266 - tgtt@tuningdevelopments.co.uk
    http://www.tuningdevelopments.co.uk - http://www.stri-racing.com

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    Lets look at the situation.

    Toyota's VVT (Variable Valve Timing) and VVT-i(Variable Valve Timing with intelligence). Both systems are not like VTEC. They do not affect lift. They affect duration. Also VVT isn't always on, again unlike VTEC. It turns on and off.

    VVT: VVT is found on the 1st and 2nd generation 4AGE20v. VVT advances the cam 15 degrees on activation. This means once ON the cam ratchets forward 15degrees. The Silvertop engine (gen1) VVT comes ON at 4400rpm and is OFF at 6000rpm. On the Blacktop (gen2) VVT is dynamic. It operates on several parameters of which the two major ones are throttle and rpm. Once past 60% throttle VVT kicks in. The operational rpm range for VVT is 3000rpm to 6000rpm, however VVT has a dynamic range of 1600rpm to 6500rpm. It will differ due to too many variables to list, but these are the peaks at which it operates. The car may opt to end the VVT cycle at 5500rpm or extend it to 6200rpm, just depends. It has a matrix in the stock ECU it uses to compute. The reason VVT ratchets back at 6000rpm+ is because the valve overlap moves from short (torque creation) to wide (max flow). Discussion on how it affects the powerband later.

    VVTi: Is now the standard basic Toyota VVT system. It can be found on all Toyota's modern engines like the 3SGE, N and JZ series engines, in Dual form on the Altezza SXE10 3SGE. The cam lift side of things was added to 2ZZ to create VVTL-i. VVTi built on the dynamic nature of VVT. Its job is to maintain the smallest valve overlap to build torque in any condition. What this system does is not simply go to a fixed position, but move the cam to any position +/-15edgrees for 30degrees of actuation. This means that if the car wants 22degrees at 4000rpm at one point and 9degrees at the same exact rpm in a different situation it can do so.

    So the fundamental differences is that VVT goes to a fixed point when activated, and VVTi doesn't. VVTi dances back and forth as its needed within its operational parameters.

    VVT can have three states of operation, ON, OFF and CONSTANT. Remember VVT turns itself on and off by the stock ECU, but you can bypass that signal and turn it on when you feel like, turn it off, or have it on constantly from any rpm point. VVTi, when given a constant signal (aftermarket), goes to its maximum forward position 15degrees and stays there, eliminating its dynamic programming.

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    Several years ago, I decided to map the 4AGE20v in my country. A lot of these cars were floating around and people didn't know a lot about them so I set about gathering data from my customers. One of our tests was a stock AE111BZR verses a race prepared 2nd gen 4AGE20v. The racecar was an engine swap into an EP82 (http://hardcore.ep91.com/features_olivert.html). So this was a comparison on VVT on a stock ECU alongside 4AGE20v using a MoTeC.

    Now the VVT system works on grounding. The ECU sends a signal (ON) to the VVT solenoid which gets grounded out by another signal (OFF). This was not something the MoTeC could replicate as the extra channels on the standalone can only turn something on or off at a set rpm.

    The BZR was tested for the first two states. ON, as stock control, and OFF, solenoid disconnected. The graph showed that with VVT ON peak hp was less than when OFF, but the torque suffered greatly when OFF. This was to be expected because VVT is for torque. Even more clear was the difference in the overall powerband. It wasn't until after 6000rpm the OFF figures started to climb on the ON figures.

    The EP82 was tested in three states, even though we knew the BEHAVIOUR would be the same. ON and OFF on this engine was the same situation (not figures as its a tuned engine not stock). We didn't adjust any parameters other than ON/OFF. We could have re-tuned, but that wasn't the aim. CONSTANT produced interesting results. The car had a 8500rpm limit, and the VVT was turned on from 0rpm to 8200rpm, basically CONSTANT. This was to see where the dyno graph would pick up so we could set a proper ON/OFF point. Holding the VVT on to redline gave the best torque figures, but the top end power (6000rpm+) in comparison the OFF (6500rpm) suffered. Suffered may not be the right term, but the ratio between the torque and hp in CONSTANT mode was smaller than in OFF. We deduced that the VVT overlap was restricting flow at high rpm. However, because torque was what was needed the car was run with VVT CONSTANT.

    Bottomline, best powerband with VVT ON(BZR/EP82) and CONSTANT(EP82). Higher peak horsepower numbers with it OFF (both engines).
    Last edited by hardcoreep; 29-12-2007 at 12:23 PM.

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    a great read very intresting mate!

    youve certainly put alot of work into it.

    now i wanna see it turboed and fully controlled

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    VVTI proved different. The car tested was a SXE10 with dual VVT-i, stock ECU. On this engine VVT-i works on both the intake and exhaust side camshafts, but I'm going say that results on this engine would reflect a similar situation as I've seen the same behaviour on a 2ZZ-GE.

    Remember VVT-i is dynamic. It can operate over varied rpm points up to 6000rpm and differing states of advance and retard. When VVT is OFF, they disconnected the wire (the ECU later threw a error code), the cams stay where they are. The surprise (to me) was when the VVTi was given a CONSTANT. The operation was the same as VVT where the cam jumped forward to its maximum position. During ON, reconnected back to ECU, it behaved as normal. The dyno showed that like VVT OFF was the worse powerband. The best overall poweraband was ON.

    This was after only 15min tuning on road.
    My issue with Toyota 23 is that the tuners of the Megasquite re-tuned the engine to make up any difference in performance between the OFF and CONSTANT states. CONSTANT because that's what the megasquirt is doing. This is my first issue with the comparison

    Now before I continue need to clarify what is happening with the Megasquirt. Is the user is sending a single trigger signal at set rpm (ON/OFF), or multiple signals at different rpms duplicating the variable programming of the stock ECU?

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    We use on/off signal, not duel trigger.
    Cant remember witch rpm on, and witch off.But i can fin out if it is very importnant
    Last edited by Toyota T23; 29-12-2007 at 02:22 PM.

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    "The dyno showed that like VVT OFF was the worse powerband. The best overall poweraband was ON."

    Well should say so.
    The powerband is poor all the way to about 5800rpm on 4age 20v if you dont use VVT.But when you keep VVT on past 5800rpm, then you cap of top end power.

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    This now comes to the comment of contention. Having VVTi CONSTANT (using a single trigger) against using it variable ON (operating as stock). Having it variable will give you better yields than just a single trigger. This has been proven by Power Enterprises who make the only of two devices that can control VVTi the CAMCOM.

    I'll get to that in a second. So you can see in detail how VVTi works. Notice the cam stages based on the variables thrown at it.

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    For further clarification, the CAMCOM on a 1ZZ-FE

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    The graphs are to allow people to see what I'm getting at. VVTi operates at multiple rpm points, so even in theory, just to trigger it at one rpm would seem less efficient than its normal operational mode.

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    Quote Originally Posted by hardcoreep View Post
    The graphs are to allow people to see what I'm getting at. VVTi operates at multiple rpm points, so even in theory, just to trigger it at one rpm would seem less efficient than its normal operational mode.
    well not at our test, mabey we did something wrong :-)

    But what i am trying to say, you can contol VVTI without making it varibel, and still get good result.
    And i bet 98% of users here dont want/or can adjust the VVTI properly.
    Last edited by Toyota T23; 29-12-2007 at 04:18 PM.

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