More VVTi information

[Guest Terry S]

Ok guys as I am sure you know we believe the VVTi system truly rocks.

 

Migster and I have been working our cods off doing research into this stuff.

 

There have been a few posts about control of the VVTi system. We have now managed to see the full VVTi map and from our findings there are two 256 cell tables controlling the stock VVTi unit. The degrees ATDC vary a lot & its a fully variable system so the notion that other standalone ecus can easily replicate a stock cars drivability seem to be wide of the mark. From what we have seen you would need to do a lot of mapping and research to get the car to have the overall performance of the stock system.

[Ian C]

A controversial post to get you thinking - if the VVTi map is so big and so great, how come there isn't a noticeable difference in performance between VVTi and non? You've driven both Terry, wouldn't you have expected a real noticeable increase in low down grunt, top end power, or possibly both for such a complex system? A fatter and wider torque curve maybe?

 

It's only because people haven't raved about it being so much better that I suspect it isn't by the way, I've never driven a VVTi and I can't say I've noticed much difference in Alex's car (not that he goes above 3500rpm anyway )

 

-Ian

[Guest Terry S]

A controversial post to get you thinking - if the VVTi map is so big and so great, how come there isn't a noticeable difference in performance between VVTi and non? You've driven both Terry, wouldn't you have expected a real noticeable increase in low down grunt, top end power, or possibly both for such a complex system? A fatter and wider torque curve maybe?

 

It's only because people haven't raved about it being so much better that I suspect it isn't by the way, I've never driven a VVTi and I can't say I've noticed much difference in Alex's car (not that he goes above 3500rpm anyway )

 

-Ian

 

I do think there is a noticable difference in lowdown grunt. I think the stock figures for torque confirm this. I think it is also partially responsible for why my car spools like it does too.

[Pete]

I'm really looking forward to the Motec plug and play systems that have been announced is all I can say. I guess they'll have to come with a base map or it's not really plug and play is it?

[Guest Terry S]

A controversial post to get you thinking - if the VVTi map is so big and so great, how come there isn't a noticeable difference in performance between VVTi and non? You've driven both Terry, wouldn't you have expected a real noticeable increase in low down grunt, top end power, or possibly both for such a complex system? A fatter and wider torque curve maybe?

 

It's only because people haven't raved about it being so much better that I suspect it isn't by the way, I've never driven a VVTi and I can't say I've noticed much difference in Alex's car (not that he goes above 3500rpm anyway )

 

-Ian

 

To be just as controversial, Your car and my car. Yours has a bigger turbo, and high lift cams at both events. Would you say there is much of a performance difference?

[Guest Terry S]

I'm really looking forward to the Motec plug and play systems that have been announced is all I can say.

 

Assuming they actually put the work in and not just generic settings

[Pete]

I do think there is a noticable difference in lowdown grunt. I think the stock figures for torque confirm this. I think it is also partially responsible for why my car spools like it does too.

My VVTi is definately better to drive than the Non VVTi turbo I had. As you say - noticable low end difference.

[Miguel]

I'm really looking forward to the Motec plug and play systems that have been announced is all I can say. I guess they'll have to come with a base map or it's not really plug and play is it?

 

Will be very interested in seeing how this pans out with Motec. I really cant see the map that comes (if it comes) with is being anything other than a very very basic map. There are far to many specs for it to be trully plug and play. What if you have 720cc injectors in there then the map will be useless. I think from terms of P&P is more refering to the physical fitting of it. So still plan to have mapping costs on top.

[Ian C]

To be just as controversial, Your car and my car. Yours has a bigger turbo, and high lift cams at both events. Would you say there is much of a performance difference?

 

Well, I didn't say there was *no* difference, just that proportionally, considering the effort invested into the VVTi mapping, there doesn't appear to be a big fat difference. But I am judging it on the lack of people going "I want VVTi as the bottom end grunt pisses all over the non-VVTi version" or whatever. Because normally people aren't afraid to say one thing is better than t'other Do you see what I mean?

 

There isn't much difference between ours, no. But then there was even less difference between mine and SecondJumps' top speed at TOTB4, and he's a non-VVTi T61... Trouble is there are a lot of variables in there - boost pressure, sodding great boost leaks ignition timing, aerodynamics, mechanical sympathy turbo bearing technology... etc etc but considering the problems you had, yep, it's fast

 

I'm wondering just how much difference there is between the T61 and the T67. Maybe the T67 only starts shining above 1.4bar where the '61 runs out of puff? But that's another discussion...

 

-Ian

[Pete]

From my personal point of view I'm interested in the benefits from simply remapping the VVTi ECU before going ahead and changing injectors and other major parts. I reckon there's some good gains to be had ironing out the eco friendliness put in for emmissions law.

[Ian C]

Will be very interested in seeing how this pans out with Motec. I really cant see the map that comes (if it comes) with is being anything other than a very very basic map. There are far to many specs for it to be trully plug and play. What if you have 720cc injectors in there then the map will be useless. I think from terms of P&P is more refering to the physical fitting of it. So still plan to have mapping costs on top.

 

If you guys can get at the stock map, perhaps Motec can too and they will use a tweaked version of that as the base map...? Just a thought

 

-Ian

[Guest Terry S]

Well, I didn't say there was *no* difference, just that proportionally, considering the effort invested into the VVTi mapping, there doesn't appear to be a big fat difference. But I am judging it on the lack of people going "I want VVTi as the bottom end grunt pisses all over the non-VVTi version" or whatever. Because normally people aren't afraid to say one thing is better than t'other Do you see what I mean?

 

There isn't much difference between ours, no. But then there was even less difference between mine and SecondJumps' top speed at TOTB4, and he's a non-VVTi T61... Trouble is there are a lot of variables in there - boost pressure, sodding great boost leaks ignition timing, aerodynamics, mechanical sympathy turbo bearing technology... etc etc but considering the problems you had, yep, it's fast

 

I'm wondering just how much difference there is between the T61 and the T67. Maybe the T67 only starts shining above 1.4bar where the '61 runs out of puff? But that's another discussion...

 

-Ian

I actually think the VVTi system is more of a benefit on a modified car. And your T67 is nicely in its map at 1.4 bar trust me

[Guest Terry S]

If you guys can get at the stock map, perhaps Motec can too and they will use a tweaked version of that as the base map...? Just a thought

 

-Ian

 

Depends what they are willing to pay

[Miguel]

Depends what they are willing to pay

 

 

And if MoTeC are willing to pay for it they will no doubt pass that cost on and boy they know how to charge. Right then ill have 2 sold the cars to buy em mind you:p

[foodfreak]

Hi Ian,

do you remember when Matt H & Rob oldham were down at G force for the rolling road day?. They both had almost identical mods, but Robs car had quite a bit more torque all the way through.More top end power as well

just food for thought

 

John

[TrickTT]

Surely since VVTi doesn't alter the duration or lift of the cam (unlike honda VTEC)it isn't going to make all that much difference

[Miguel]

Surely since VVTi doesn't alter the duration or lift of the cam (unlike honda VTEC)it isn't going to make all that much difference

 

Let me get this correct . What you are saying it dont alter lift or duration. Ok scrap the VVti then.TMC just wanted a bulge on the cam cover.

 

The VVti plays with cam timing therefore afecting duration

[Digsy]

The VVti plays with cam timing therefore afecting duration

 

Sorry, Mig. VVTi does not affect duration. You cannot do that unless you swap cam profiles, or emply a much more complex variable geometry system.

 

And as for it not making "much of a difference" because it doesn't change duration and lift, had you considered that it might allow you to optimise the car for top end power and then re-tune it for more grunt lower down?

 

C'mon you lot. It's not all about boost pressure, how much air you can shove into the cylinder and the peak bhp figure on the dyno sheet.

 

There's a whole torque curve out there.

[Guest Terry S]

Sorry, Mig. VVTi does not affect duration. You cannot do that unless you swap cam profiles, or emply a much more complex variable geometry system.

 

 

 

mmmmmmm. We need a drunken chat, you me, Mig & Chis.

[Miguel]

Sorry, Mig. VVTi does not affect duration. You cannot do that unless you swap cam profiles, or emply a much more complex variable geometry system.

 

Yup thats what we are talking about here

 

And as for it not making "much of a difference" because it doesn't change duration and lift, had you considered that it might allow you to optimise the car for top end power and then re-tune it for more grunt lower down?

 

Yup

 

Trust me Digsy. How else can you make a smaller duration cam act like a bigger one.

[Digsy]

Yup thats what we are talking about here

 

Confused now...

[Miguel]

Confused now...

 

 

Just Trust me ...Read the 1st post ...it far far more complex than given credit for with lots and lots of ajustment. Not saying no more:music:

 

Over a beer sometime:yes:

[Digsy]

Awwww. Are you guys trying to play a trick on me or something? C'mon...where's the camera? Where's Jeremy Beadle?

 

VVTi doesn't change the geometric cam duration one iota. All it does is schwing the cam maximum opening point forwards or backwards about a nominal point. This will alter the way the engine breathes by varying overlap and the compression height by changing the intake valve closing point, etc, etc, but the geometric cam duration won't change.

 

But you guys must know that, so what gives?

 

There are ways and means to alter effective duration by using VVTi type technology, but that's waay outside of what the Toyota VVTi can do, plus it has other side effects.

 

You lot... Pffft This is one of those "Hit Squad" things that Noel Edmunds used to do isn't it?

[Miguel]

Awwww. Are you guys trying to play a trick on me or something? C'mon...where's the camera? Where's Jeremy Beadle?

 

VVTi doesn't change the geometric cam duration one iota. All it does is schwing the cam maximum opening point forwards or backwards about a nominal point. This will alter the way the engine breathes by varying overlap and the compression height by changing the intake valve closing point, etc, etc, but the geometric cam duration won't change.

 

No one said it changed the physical cam duration profile that would involve alien hardware and cams in semi liquid form.

 

 

But you guys must know that, so what gives?

 

There are ways and means to alter effective duration by using VVTi type technology, but that's waay outside of what the Toyota VVTi can do, plus it has other side effects.

 

You so close you could fry bacon on your head!

 

 

 

You lot... Pffft This is one of those "Hit Squad" things that Noel Edmunds used to do isn't it?

 

 

LOL:hug: need beer