"A" engine info

[REN69]

BTW guys.. Toyota has 2 systems.. VVTi and VVT"L"i as in "LIFT"

[thespud]

Originally Posted by freakinbox

yea you missunderstood what I said... I was saying that the 20v didn't have it because vvt-i only came out in 98 in the altezza I NEVER said the altezza had a 4age...
I was saying that the blacktops have vvt.... because the spud said it had vvt-i but when this has come up before in previous threads it was told that they have vvt
I thought the only difference between a silvertop and a blacktop was the face the black top has lighter internals.

Blacktop also has MAP, Silvertop AFM - Another difference between them. Compression ratio is different, ie: Silvertop is 10.5:1 Blacktop is 11.0:1. Internals ar lighter, so you are correct there. But there are more differences than just that...

vvt-i uses changes in the timing which another gear is pushed into the timming chain.... or is it belt on the 20v?
that wasn't just for toyota that applies to the vtec's and such for honda too since they use the same idea just different name

That is VVTL-i. Not VVT-i. VVT-i is just a better computer controlled system of the VVT.

[StealthSeo]

oh thats why you said it ren said it was better

[canadianae92]

BOTH 20v's Blacktop and Silvertop have VVT, not vvt-i or vvtL-i. Neither of the 2 links to wikipedia or the one freakinbox posted said the blacktop had vvt-i ifnact they said the 20v's had VVT.


Here is a description the VVT system copied from club4ag.com "vvt vs vtec post" in the beginners section.


By using a conventional valve system, to keep a modern multi-valve engine usable for the road, you are limited to about 85hp to 90hp per litre. You can use a bigger camshaft quite easily get a lot more power, but only at higher revs, and at the expense of power at lower revs. So, with a bit of lateral thinking, it is now becoming more common to be able to change that very cam timing that limited the engine power while the engine is running. The Toyota VVT system isn't new, however, as similar systems have been in use for many decades before. But not for a mass production engine and certainly not with the highly accurate control of the modern engine management systems. The Honda V-Tec system is a relative new comer, and by using a system of far greater complexity than that used by Toyota, Honda is now making an engine that produces as much power as many of the better racing engines!
So lets have a look at each system, and how they work ...
Toyota Variable Valve Timing system, or VVT & VVT-iThe VVT-type system has been around and in use by various companies for at least 40 years that I know of.
(I can remember seeing a 1960's catalogue from the US that showed a special cam wheel that bolted onto a small block Ford engine's cam, and it had a mechanism that worked like a mechanical advance system in a distributor, so that as the revs picked up it advanced the cam timing. I also believe that Alfa Romeo or Fiat used a similar system back around then, or maybe before)
VVT is simple and fairly effective. It consists of only two main parts; an 'oil control solenoid' and the VVT mechanism itself.
This diagram shows a few more bits & pieces, but you can clearly see the main two - the VVT pulley and the OCV. (Oil Control Valve, or oil solenoid as it's often called.)
Closer view & cutaway of the VVT controller The early VVT system was relatively simple, ie, at a specific rpm (~4400rpm on the 20 valve 4AGE's) the computer signals the OCV to open, this lets oil pressure go through a special gallery in the #1 inlet cam bearing, through the centre of the inlet cam to the VVT pulley. There's a small piston in the VVT pulley, and once it gets enough pressure behind it, it starts to move outwards, causing the outer part of the pulley to turn in relation to the inner part, due to the helical spline that guides the piston's fore & aft movement.

So, when the computer signals for the VVT to operate, the OCV opens and thus causes the VVT pulley to advance the inlet cam timing by 30°, reference the crankshaft. (15° on the pulley itself)
The rpm at which this happens is worked out by running the engine on a dynamometer with the inlet cam in both the fully advanced and fully retarded positions. Since the two different cam timing's will make different power throughout the rev range, (advanced inlet give more top end power at the expense of low end power, and vice-versa) there is a point where the power will be identical for both cam settings, and this is where the VVT is programmed to operate. Because the power output is the same with the VVT in either position, you can't feel anything when it happens. You can, however, hear a change in engine note, just before there's a big increase in power!
More detail on the the VVT logic - The VVT comes in three types for the 20 valve. To the best of my knowledge, silvertop 20v's pre May 1993 have the VVT actuate at about 4400rpm. Post May 1993 they seem to work on throttle position and ignore revs.
The blacktops seem to work like this, as described on Club4AG -
1. Starting. When you crank the starter there will be VVT operation until the engine fires up, obviously to allow more air into the engine to allow an easier fire up.
2. Coolant temp. There is absolutely NO VVT operation when the coolant tempt is below 50°C except for that brief moment when you operate the starter. Reason obvious, who want to stress a cold engine.
3. Engine rpm. VVT will operate in any rpm between the range of 1500 and 7200 when the inlet manifold pressure is right. The min and max range can be a little out because I was reading from the car tacho. Trust me they are very close.
4. Engine load/inlet manifold pressure. This seems to be the single most important parameter controling the system. The VVT will NOT operate if the inlet manifold has more than about 5 inches of vacuum (can't get the exact reading because everything happen so fast. It's very close.). This is very close to zero vacuum which is atmospheric and that is about the maximum load the map sensor will read to tell the engine in an NA car. As you can figure out the throttle will usually be in the more than 3/4 position for this to happen.
5. VVT will work without the speed sensor.

Now, back to the above schematic of the VVT. It shows the second evolution of the VVT system - called VVT-i - where instead of the simple 'on' or 'off' positions of the earlier VVT system, this version can make the inlet cam retard/advance to any angle between the maximum limits, and to do this the camshaft has a position sensor on the back of the head. This means that the engine is even more flexible in it's power output than before. The latest version, VVTL-i is described on this page. It's completely different to the original VVT system, and is more like the V-TEC in operation.
There are two engines that commonly use the VVTL-i system, the 1ZZ-FE/2ZZ-GE series and the latest (in 1999 & onwards) 3SGE, as used in the sporty Altezza. The early generation 'redtop' four 3SGE's have a single inlet VVT-i and the later 'blacktop' generation four 3SGE's have dual VVT-i controllers, one on the inlet and the other on the exhaust cam, and makes 200hp from 2 litres.
So, using VVT technology, it's pretty easy to get around 100hp per litre.

[StealthSeo]

awesome info, i still wonder if you can make the VVT to VVT-i or even VVTL-i conversion?

[freakinbox]

vvt is bascially what replaced TVIS on the early 4age to give you power in both low and high rpm. same reason's for both different apporaches

[StealthSeo]

works for me!

[freakinbox]

I like tvis... engine will still run ok if it breaks... alot less to it too LOL even though vvt/vvtL-i and vvt-i all work more efficient

[StealthSeo]

i hear tvis is constricting to air flow? also how would you get rid of it could you just swap mani's from the ae101?

[freakinbox]

meh I don't need power, I just need to think/feel as if it's there... TVIS does that well .

[canadianae92]

I havn't driven a TVIS but my smallport it pretty slow if your not reving it very high. My normal enjoyable driving goes up to 4500rpms just licking the power band mountain and my "gas saving" approach to driving it goes up to 2700 rpms or around there(don't really look) which is lugging it if you push hard on the gas and I got about 15L to 100kms in the short time that I tried this in city pizza delivery but I figured it wasn't worth it and was hard on the engine and engine mounts so my daily driving is around up to 3500rpms now a days just staying above 2500rpms where it would lug. TVIS sounds like it would be great for dailing driving it close the single runner to each port to create greater intake velocity, how is the power down low guys?
freakinbox I have a question what type of gas milage, and how many litres do you get to 100 kms, also where is you daily driving band at(where its comfortable).
and anybody else could answer those questions it'd be great even for a 20v would be sweet and a tvis 4ag.

I hope I cleared that VVT thing up, I had it explained to me in person and I remembered the info from club4ag so enjoy you guys I think you guys should pay more attention to club4ag it has great info on all 4ag's.

[freakinbox]

I didn't get to push the 86 very hard but it felt powerful the whole way through. My ae92 with the 4af doesn't feel like it has anything until at LEAST 2500. And my 4af takes a hell of a beating. I am pretty sure your smallport could do it no problem

I usually do about 3500 - 6000 rpm. I used to push it to 7000 but I figured why. you loose to much rpm per shift then... BUt I usually only get maybe 400 to a tank if I am lucky. carb is actin up.. and christ on the hwy I do 140 km/h - 180 km/h and at 140 I am doing 4000 rpm dead on...

[cuzman]

Boys! thanks for the vct info..That sounds aboud right.....
my 20v ST COmes in at bout 4400 and the change over is as smooth as a babys butt.
THe note changes and she goes sick!!!!!LOve it!!
Now heres some info u might find usfull
An aftermarket efi computer manufacture (haltech) can control the vct on a sivel top!.N/Sht
To get the best power from a silver top they mod the vct cut in rpm.. in cunjuntion with ditching the afs sensor for a map....afs is very retrictive(whats the point of 4 throttles if they cant breath?) As this is what the black top did factory...
As the motor is very peaky they allow an 8200 rpm cut out.....yer hang on bear with me
it wont blow if you only peak it.. and the next gear is in its prime for more pullen..
to achive this you need a good exhaust system and a shit hot intake system

A mag i read a few years ago had a t.starlet(smaller than a rolla) with a sivel top in in) for racing use only..the motor was stock but the efi and more important to us the intack system!!

it had a cold air intack box of a v8 hsv holden commodore (pontiac gto)

We have sht loads of these here as we have wagons ,sedans,coupes,utes ets and we acually built the gto here for you in lhd!.....

The box and hose will fit no worrys just a few small bolt issues and will take an awsum /large air cleaner......it has the same dimensions as the 20v rubber intake track

P.s the shorter the intack track the greater the top end.vice versa...
It has somthing to do with the vacume and air flow velocity.....

[cuzman]

By the way i get 25 mpg but it runs rich as my efi was stuffed..still is stuffed

so im gunna drop in haltec $1500 au +bout 600 to tune right

if i floor it it goes to 22 mpg

these figure are approx only but close as!

[canadianae92]

With a aftermarket ecu on a 20v I'd just run open ITB's....