bigandy
|
| posted on 24/4/07 at 09:04 AM |
|
|
Toyota 4a-ge TVIS system, bin it?
Morning folks.
I'm part way through stripping my engine down (Toyota 4a-ge from a 1989 Mk1 MR2) and I have just taken off the TVIS system.
As I shall be building the engine back up with a megasquirt system providing control over the fuel and the sparks, I am just wondeirng if I should
keep it (i.e. the TVIS system) or not.
Is anyone aware of the benefits of keeping it versus the benefits of not keeping it?
Cheers
Andy
[Edited on 24/4/07 by bigandy]
Dammit! Too many decisions....
|
|
|
|
|
bimbleuk
|
| posted on 24/4/07 at 10:25 AM |
|
|
Not done this in the past but myself but have casually read posts on 4AGE forums. Basically the head has wide ports to match the 8 hole TVIS plate. So
if you were to bin the TVIS you may get low speed power loss as a result. Maybe this can be soted with the programmable ECU.
One reason I've seen it done before was for forced induction and usually in that case the butterfly mechanism is removed and the holes welded
up.
Might get a better answer on www.club4ag.com and similar forums
|
|
|
shades
|
| posted on 24/4/07 at 11:43 AM |
|
|
I'm doing away with mine and fitting throttle bodies instead.
As for the TVIS, I could see what it was doing (butterflys and all), but didnt realy understand how it helps with the performance? Oh and it looked
dead complicated
Thanks
Adrian
|
|
|
davew823
|
| posted on 24/4/07 at 11:48 AM |
|
|
TVIS
Andy
With a stock motor you will loose about 4.5 HP on the low end and gain about 1 HP on the very top of the power band when you remove the 4AGE TVIS
system.
Search for Garage-' There an A - B test for a 4AGE with and without the TVIS.
DaveW
|
|
|
bigandy
|
| posted on 24/4/07 at 11:55 AM |
|
|
from what I understand, the TVIS system closes off one of the two ports per cylinder at low engine speeds. Apparently this is done to increase the
gas velocity entering the cylinder, and appears to promote cylinder filling. Or something like that. So I have read. 
I think I am going to bin it, simply because it looks rather complicated, and the weight saved means I can have a jaffa cake or two tonight As the
car is going to be much lighter than the mr2, I should imagine the low down power loss will not be too much of an issue either.
It is interesting to see the comparison between a motor tested with it and without it though, cheers for that link.
Andy
Dammit! Too many decisions....
|
|
|
thomas4age
|
| posted on 25/4/07 at 10:48 AM |
|
|
If you run a Big port T-vis engine in a complete stock set-up with toyota ECU
DO NOT BIN THE SYSTEM!! IT WORKS.
it only weighs about just under a kilo so that's no reason to bin it.
it's a very simple solution to a big problem they had back then, sureley there are better way's to recoup lost low rpm torque nowadays
(hence VVT on the 20v)
but it's still a good system
the only thing you'll do by ditching it is throwing away 21nm below 4250rpm.
your choice
if using a stand alone managment and different intake system like ITB's it might get in the way even with most cam changes on the stock
manifold, it works well, the only thing being the trigger rpm needs altering to the cams of choice.
and what you say about it being complicated, that's not true.
only 1 vacuum tube and 1 wire to get it working.
grtz Thomas
[Edited on 25/4/07 by thomas4age]
[Edited on 25/4/07 by thomas4age]
If Lucas made guns, Wars wouldn't start either.
|
|
|
bigandy
|
| posted on 25/4/07 at 11:04 AM |
|
|
Hi Thomas,
Thanks for the reply. I'm going to be using a Megasquirt ECU, and a very much modified (possibly even custom made) inlet manifold, the main
reason being the stock one will not fit! I'm also going to have to bin the standard distributor due to it not fitting.
With that in mind, would you say it is worth keeping the TVIS system? I'm not sure how easy it would be to hook it up to the Megsquirt ECU, but
I am sure it can be done...
Cheers
Andy
Dammit! Too many decisions....
|
|
|
Findlay234
|
| posted on 25/4/07 at 02:39 PM |
|
|
Bigandy you are correct the tvis increases the intake flow velocity at lower engine speeds. This constriction in the system will increase the pumping
losses but the higher intake velocities will increase turbulence in the manifold and cylinder therefore promoting better mixing of the air and fuel.
This in turn improves combustion, efficiency and reduces emissions.
If you can avoid removing it then dont, it will help the engine to run better at lower speeds. If you do end up removing it tho it wont affect the
performance by very much considering the weight of the car youre putting it into.
I plan on using mine at first but when i convert to ITB's will remove it.
|
|
|
