Help with TVIS ??

[Snip3r]

Somebody want to explain to me in great and not so great detail exactely how my TVIS sytem works on my 89GTS.

How I've been told is that over a certain RPM a 2nd, larger set of ventricals (valves??) open up giving the car more power.
So does this work similar to the new celica engine,(or the new Lotus Exige/elise) where it gets to that same magical RPM and it jumps onto a power cam opening a bigger set of venticals giving the car more power?

If so, would it be possible to get a set of bigger cams for my engine, that would boost my power even more?

Does any of what Im saying make sence at all?

Cool thanks guys!!

(PS: what is the magical RPM on my engine)

[REN69]

SEARCH button my friend.. there was a thread on this either last year or the year before.

If you get cams.. you would experience power gains whether you got TVIS or not.

I believe the magical RPM is 4500rpm or so.. can't you feel it??? the car goes BOOOOM!!!

[RakeRon]

And no, TVIS is nothing like VVTL-i found on the new Celica. TVIS stands for Toyota Variable Induction System. It has nothing to do with the valves or cam timing like VVTL-i. What it does is this. In your intake manifold there are a set of butterfly valves. This valves normally stay shut until you reach that magic rpm (usually somewhere between 3500 -4500 depending on the condition of your engine) wich keeps the intake velocity up for the lower rpms. When it hits the magic rpm the butterflies open giving the engine more air for better breathing in the upper rpm band. VVT-I completely replaced TVIS being much more efficient by auto-adjusting your cam timing for the same affect but on a more precise scale and is always on unlike TVIS. VVTL-i is the evolved form of VVT wich adds a second lobe set on your cams wich kick in at a magic rpm to give the upper high end of the rpm band even more needed air. Feeling educated Snip3r?

[Snip3r]

Yeah Im getting there. So by putting on a new set of cams to open the bigger valves that I thought I had wont help at all will they.
What can I do to the butterflys to let/force more air in?

[REN69]

It would help... just not in the way you thought it would.

[bob022004]

HKS does have cams for it still. Personnally i'd love to get the newer 4A-GE's that had the TVIS removed. they made more power and were still effecient. about 140 compared to 120.

[RakeRon]

You mean the redtop/small port ones. They have alot more than the TVIS removed!

Snip3r: you can either disable it or remove it entirely. If you only plan on a light-mild tune disabling it is fine, but in higher tunes I hear it can become restrictive unless removed. Also any cam above 264 degrees you will not notice any power gain from the TVIS nor can you use higher cams on the stock ECU. Anything higher you'd need a standalone, though the current generation piggybacks are pretty close to a standalone now you you might be able to tune the ECU with a Greddy Emanage or similar piggy back to handle the higher duration.

[Snip3r]

Wow, now I am feeling educated. So why do you need to change the ECUwith CAMS bigger than 264. Just to help manage all that new air and fuel, make sure its mixing it properly and all that jazz.

So would you guys say that the TVIS system was agood idea, but just didnt work all that well?
What again are the benifits of having the small ports? To me it would make more sence to have more power outta something with bigger ports. no?

[RakeRon]

Originally Posted by Snip3r

Wow, now I am feeling educated. So why do you need to change the ECUwith CAMS bigger than 264. Just to help manage all that new air and fuel, make sure its mixing it properly and all that jazz.

So would you guys say that the TVIS system was agood idea, but just didnt work all that well?
What again are the benifits of having the small ports? To me it would make more sence to have more power outta something with bigger ports. no?

The stock ECU just can't handle the extra airflow beyond that and theres only so much that can be done with a piggyback. For the era in witch TVIS was implimented it worked great... for daily driving. Variable induction systems are actually still pretty common on low end american cars even on newer cars. Seems like only Japanese and Euro cars put variable cam technology to full use on just about every car in their lines.

[toyotaspeed90]

i call BS on the 264 being a limit...... the main reason i could see there being problems is that generally a larger cam will make more power at higher rpm's.... meaning the only limiting factor of the ecu is the rev limiter holding you back (and probably cutting fuel during the higher powerband)..... reason i say this is that right now i have a smallport running on a 4afe.... and if anything, it runs rich..... ecu has NO problems with the much higher airflow (map based) and the much larger injectors.... i am also planning to run it (for now, maybe go with megasquirt on the corolla.....already on the mr2) with the 4afe ecu when i get the silvertop 20V itb's and yet even larger injectors on the motor.....

that being said..... simpler way to talk about T-VIS..... if you look at your intake manifold there are 8 runners (basically where the air goes from the single throttle body and breaks apart for each cylinder) which means 2 runners per cylinder. For each cylinder one of those runners has a plate that blocks it off (looks like a throttle body, for lack of a better explanation)... TVIS is vacuum controlled via a solenoid... so when the solenoid gets the set amount of vacuum it pushes a valve that has all of the blocking plates open...... The entire t-vis setup is about 3/4" long.... Another engine that used the EXACT same technology was the 90+ 4xe1/4xe1t's in the isuzu impulse/stylus (and a lotus elan).... only difference on them is the "t-vis" setup is roughly 1 1/2" long on that one (so it lengthens the intake runners a bit).

[RakeRon]

Originally Posted by toyotaspeed90

i call BS on the 264 being a limit...... the main reason i could see there being problems is that generally a larger cam will make more power at higher rpm's.... meaning the only limiting factor of the ecu is the rev limiter holding you back (and probably cutting fuel during the higher powerband)..... reason i say this is that right now i have a smallport running on a 4afe.... and if anything, it runs rich..... ecu has NO problems with the much higher airflow (map based) and the much larger injectors.... i am also planning to run it (for now, maybe go with megasquirt on the corolla.....already on the mr2) with the 4afe ecu when i get the silvertop 20V itb's and yet even larger injectors on the motor.....

Jeeze dude, can we say smog machine? Larger injectors, ITBs, and larger cams on a stock econo driven ECU. That thing will run like crap and will most likely LOOSE power. Reasons: you just admited that running the larger cams makes it run rich as it is and larger injectors & ITBs hooked up to an ECU not programed with the proper feul maps (from what I can gather NO piggyback can adjust the feul maps accordingly for the ITBs to get them to run right). Running rich =/= more power. Running rich = waisting gas.

[toyotaspeed90]

actually as of now i'm putting down 109.6whp (and that was a year ago..... i have the car running much better now)... which is very respectable for a bone stock internally 4ag....

i didn't pass smog ONLY because it doesn't have a TPS on it and the ecu never goes into idle mode..... i was very very close to passing (and then just decided to register it in the city i go to college in.... and don't have to take tests). Also i'm still getting around 30mpg in the ae92.... i'm guessing i'm running rich mainly because my o2 sensor is bad

to be quite honest i'm not sure you understand how maps work...... especially with the clock speed on the 4afe ecu running slower, the map burned in the ecu is working just fine. the reason it works so well is because not just one thing is raised more than the other...... when i upgraded to the 4ag both the airflow and the injector size went up..... for the most part the pulsewidths didn't need to increase or decrease (obviously) because the injectors in the motor were matched with the airflow characteristics of the engine (greentop 250's). Same goes with the 20V itb setup.... airflow will increase so you should increase injector size

worst case scenario it doesn't run too well and i get megasquirt....... not like i don't know how to use it & build/wire it.... no talk about this piggyback garbage