adjustable T-VIS

apampe

New member
I just put together a digital tachometer that you can then adjust when it opens and closes the T-VIS on our cars. Takes power, ignition in from the Diagnostics terminal, and then T-VIS control out which you connect to the T-VIS VSV (disconnecting the ECU). It works by taking over the ECU's job of grounding the T-VIS VSV to close the valves, based on the digital tachometer. It has a 2X16 character screen in a small box to fit easily under the hood, or inside the cabin.

Anybody want to dyno their car and send me the "open" and "close" graphs? I'll give you a T-VIS controller with screen to use during and after the dyno. Keep it for free in trade for your graphs and "testimonial" on my website. First person who seems legit and can dyno their car relatively soon will get one. http://www.pampeperformance.com
 

ST185pinjo

New member
I have no dyno, but I tested this on my car with the SM4.

8dxvs4i.gif


It is in RPM and seconds.

Blue line is T-vis closed(A/F is good).
Pink line is T-vis open(A/F is good).
Yellow line is T-vis closed and open at 3000 RPM(A/F is good).
Red line is T-vis closed and A/F is to rich.

You can clearly see the yellow line (closed and open) is the fastest to reach 6750 rpm. The blue line is ging to be more than 3 seconds slower to reach that rpm in 3rd gear.

I don't know if the stock ecu is changing fueling when you keep the T-vis shut. If it isn't, then compare it to the red line. If the T-vis is open, there is more fuel needed than when the T-vis is closed. Then the difference is even bigger.

When we first installed the SM4 I drove with the T-vis closed, but with good A/F. Then we opened the T-vis and it needed fuel(was leaning out).
After tuning the car with the T-vis opening at 3000 rpm, the difference was big enough that we could notice the extra power very good.
 

Andy

Member
Ever try a GTech, it will produce Time vs. RPM and or HP graphs. May not be as accurate/good as a dyno but it's good for confirming a mod made a change w/o running to and paying for a dyno.

Send me one! I'll send you RPM & HP vs. Time.... :D

Andy
 

Shaggz00

Active member
I'll do it for you. I was actually going to do it anyways because I wanted to control my T-VIS with an E-manage. Your method sounds simpler though because I won't have to try and screw with getting the e-manage VTEC controller to work with the TVIS. I have access to an AWD dyno whenever I want, also.

I was reading that basically we should do one pull with it closed and one opened like you said, and then open the T-VIS wherever the power graphs intersect. Won't it be mod-Dependant though? Cuz my car has some mods. or are you looking for a stock 165 graph? Let me know what you think. I can have the car on a Dyno ASAP
 

MrDB

New member
If im reading that graph right you would be quicker to have TVIS closed till about 4000rpm or 4500rpm then open after, looks like almost half sec quicker that way??
 

apampe

New member
Avi-

Yeah, it is mod-dependant. That's why I want someone with some mods to give it a whirl, and see how far from stock is optimal on a modded engine. The whole point is to be able to adjust it after mods. What you 'read' is what I've heard too, and it makes sense. BUT, I haven't had time to study the posted graph; it seems interesting. I may want to complicate my controller and add some time delay portion to the T-VIS on/off decision, other than going purely on the current RPM. Right now you simply set a high valve-opening RPM and a low valve-closing rpm. In between it matters if rpm's are on their way up or down. I've set this range small (200 RPM on my alltrac through). It's basically to prevent it flickering if your cruising right at the "set" RPM.

I'll PM you about getting your address.
 

apampe

New member
So, as for the RPM vs. Time graph....

What's graphed agianst time, is a addition of two things, that give some insite into the horsepower of the engine, but it's not necessairly the horsepower. What we need to know is the instantanious horsepower at each RPM. The graph shows data based on it's own previous data...

The two components that contribute to the RPM reading at a specific time:

1. How fast the engine/car are traveling, which relates to the required energy to get it sped up. This tells how well the engine's performed from the start. So, the "T-VIS open" graph has a signifigant portion, that reflects the T-VIS being open at low RPM's. The "T-VIS closed" graph errors the other way... At 5000 RPM, you'll get a good number, because it's including how well the engine did when it was at 0-4000 RPM too!

2. Wind resistance... this gives a good connection to horsepower. It's a bit more complicated though. It's not linear... as in "MPH top speed" (which is all wind/drivetrain resistance) per HP. Basically it dosen't matter and isn't worth discussing beacuse #1 throws it off already..

So, you need a dyno to see when it needs to be open/close.
 

ST185pinjo

New member
If im reading that graph right you would be quicker to have TVIS closed till about 4000rpm or 4500rpm then open after, looks like almost half sec quicker that way??

This is not quite true, I thought so too after reading the graph.

After making a change(open/close), it takes some time to get the rpm to go up quicker. If you follow the yellow line, knowing that my T-vis opens at 3000 rpm, you don't see imediate change.

At 4750 rpm you can see the line go up, while I opened my T-vis at 3000 rpm.

Please keep in mind that I don't have the CT26 any more.

Some guy at the celica forum here said that the engine doesn't handle the O2 sensor readings at more the 60% throttle. I don't know this fore sure.
 

Conan

New member
ST185pinjo":49d5snn4 said:
Some guy at the celica forum here said that the engine doesn't handle the O2 sensor readings at more the 60% throttle.
That's correct except for the %, it's 75 (3/4 throttle).
 

Shaggz00

Active member
One interesting thing I noticed this morning when I started up the car...
I took off driving before it reached the normal operating temp, which for me is anywhere from 199 - 209 degrees Fahrenheit (I have a digital water temp. sensor). I started driving this morning when it was about 165F and I saw (according to my e-manage real-time display) that the T-VIS was opening every time I hit the throttle. It did this until I reached operating temp. at which point it started opening at the normal 4100-4200RPM range.

So my question is this, apparently the T-VIS must have something to do with cold starting. Does your controller account for this? Is it possible to only activate the controller once the car has reached operating temp? I suppose even just a switch that can be flipped once the car is warm. I need to wait for my car to cool down again so I can double check what I saw, just to be certain I'm not lying to you guys :p . What do you guys think?
 

apampe

New member
very interesting. No it dosen't open it under throttle when cold, but great observation. I'll hold off on sending you one and see how to add that feature.

So the easiest solution would to have a switch like you said. Or I could have it watch the temp sensor, and let the ECU control the T-VIS until it's warm. Better yet tap into the TPS as well and implement cold, throttle-open, opening of the T-VIS on my controller. Maybe there is some other way to do this...

I'm going to go watch the ECU's T-VIS output when my car is cold and see what happens, then try to get something working to cover this. Likely I'll add two more interfacing wires (temp and TPS) to the controller. I'll keep you guys posted.

One more thought.... if it goes open every time you hit the throttle, what's the point of closing it when idling? Could it just be held open until warm? I'll test all this out tonight and this weekend.
 

darryl_p

New member
i can tell you on the RC/CS ECU the tvis is used by throttle/engine load, not rpm alone

and i can tell you from data logging everything useful ( external to ECU ) that the ECU comes out of closed loop when the TVIS opens. and its mainly controlled on throttle openning. i say this cos its at 18% throttle on my car, allowing for tolerances, i think you will find its between 15 and 20%

this amount of throttle on the flat, is enough to get you approx. 80mph after that its open to the maps of the ECU and from my wideband data logging this is the case.
no way not on earth will it be closed loop until 50% or 75% that amount of throttle gets you 110mph+ speeds and i saw on my particular car 12.9:1 at that speed/throttle.
 

darryl_p

New member
standard ST185CS ecu. just wired so i can log everything.
forgot to say, eventually under no load ( ie. in neitral ) i can get the revs to 4200rpm when the TVIS will open. on my logging i need about 7% throttle and its about 4% on the AFM. so the TVIS can be rev openned, providing the load on the engine is low enough.
 

apampe

New member
Sorry It's taken me a while. Went on a couple snowshow trips with short notice. So I've tapped the TPS sensor, just have to build the new controller now.

So, consitering what everyone said... what would the ideal T-VIS controller do? I've just tapped into the TPS sensor signal. Temperature should be easy, so I'm about to program this thing. I'm planning on an adjustable RPM setting, where it will only open if the throttle is above 15% (should that be adjustable?). This is while it's warm, if it's cold then it will open when the throttle is above 10% no matter the RPM.
 

Shaggz00

Active member
I guess that if it opens at 10% it should be good. Is there any way to lower it though? I mean like 5% or lower? I dunno what percentage the throttle is normally at when you take off slowly... Did you get a chance to verify what I suspected? That it opens when cold?

As far as the temp switch, what you got goin on sounds good. Just gotta figure out what the 'warmed up' temp is I guess... 200F? or maybe lower like 190F?

The adjustable RPM setting is perfect since that is what we are looking for. As far as only opening above 15%, I'm not really sure what you mean. I'm assuming that it's like this ( Which is also what I feel would be ideal):

The TVIS will open with every throttle touch until the car is warmed up to operating temp. After which it will open at whatever RPM we set it to, as long as it's above 15% throttle. Meaning that if we are cruising on the freeway above 15% throttle it won't operate, but it we want to get on it real quick and push that throttle past 15%, then it will activate. Or if simple driving with spirit :evil: it will also open.

Big thumbs up, dude! Sounds like this thing is gonna be awesome!
 

gt4tified

New member
The HKS VPC looks like a good upgrade for our genII engines but when does it become a necessity? I for one think its a big piece of junk taking up vital room in my engine bay (as I'm now looking for a location for my water/alco pump).

I'm also trying to follow RickyB's power primer to get to at least 250hp to the wheels and about just over that in torque, and he says that the AFM does not become a nuisance until higher up on the power chart.

How many of you have considered this mod, and for those who have done it, are there any issues. My pal with his 280hp MR2 turbo put one in and said that every morning, the engine "searches" for proper idle, and he has to fine tune it a bit.

I'm currently considering one but at the same time wondering if my $450 would be better spent elsewhere. Your input please!
 

GMan

New member
> gt4tified
> All Trac Elite
> Location: Trinidad, W.I.
> Posted: Fri Feb 08, 2008 5:33 pm
> Post subject: HKS VPC question

Hi ~Ralph~;

> The HKS VPC looks like a good upgrade for our genII engines

It is ok, good for removing the AFM.
Maybe running 550 inj's with a new VPC chip ??
( I have heard of even 720's )

> but when does it become a necessity?

NEVER.
If you Need to remove the AFM due to Major upgrades,
the VPC is Not the way to go. A Full EMS Is IMHO.

> I for one think its a big piece of junk taking up vital room in my engine bay

The VPC is not really tuneable. Just a few knobs.
An HKS GCC Helps a bit so you can vary fueling by RPM's.

The AFM does a good job of adjusting for changes in VE,
which changes with upgraded intake, exhaust...

> I'm also trying to follow RickyB's power primer

Excellent read.

> to get to at least 250hp to the wheels

No "need" to go VPC or remove the AFM at That level.

> he says that the AFM does not become a nuisance until higher up on the power chart.

See. :D

> and for those who have done it, are there any issues.

How cold does it get ? I had issues with my VPC when
temps dropped below freezing. The VPC bypasses the
air temp. So the ECU never sees the actual air temp.
Good for when the air temp gets hot. Not godo when you need
cold start help.

My car Generally ran much better with the stock AFM.
I switched back to the AFM in the winters actually.

> My pal with his 280hp MR2 turbo put one in and said that every
> morning, the engine "searches" for proper idle, and he has to fine tune it a bit.

It is a bit finicky. The car does rev a bit beter at Higher RPM's with
the VPC, but I have few mods to take advantage of it.

> wondering if my $450 would be better spent elsewhere. Your input please!

If one falls into your lap. It is Ok to buy.
I'd save for a Nemesis or other Real EMS.
Last computer related upgrade you'd ever need.

Where were You when I was Selling My VPC ??? :shoots:
Another board member bought it. I wish him luck. :smokes:

Regards;
 

___Scott___

Active member
Just a quick observation. If you are just grounding the T-VIS wire to open the T-VIS plates, (that's all the ECU is doing.) You don't have to emulate the behavior of the ECU, just wire in parallel and "wire-OR" the two. That lets the ECU control the warmup behavior and your controller set the opening earlier than the ECU will. If you want to override/block the ECU from opening the T-VIS, you just need to add a relay or transistor in the wire to the ECU and control it as desired.

You'll end up with a very simple hybrid T-VIS controller and retain most of the stock behavior.
 

apampe

New member
Good call. I'll think I'll go ahead and do that to handle the cold-behavior. Sould be only a difference in wiring it into the car.

Sorry It's not done yet, I'm learning to use/program the USB port I put on a test version, which is something I've never done. I'm testing if it'd be worth it to have a more advanced settings adjustable on the computer. Currently It's "on at X RPM if Throttle > X %". Another possible advantage to the USB is that you could get it for cheaper without the screen and buttons. Screen/Buttons cost about $15-25, where usb support is an extra $5. I believe most people would like to change settings without the use of a computer though.

I have my USB test unit setup right now with an adjustable graph of throttle % needed at each RPM to open. A typical settings would then be over 100% until a major drop to around 15% at 4200 RPM. I'm tring to test if it's smoother under more conditions to have the graph slope a bit instead of a completely sudden drop, like the simple and stock setting. It seems smoother more often with a sloping line where at 100% throttle it opens at about 3600 and at 20% it opens at about 4200 (if things work perfect you'd never notice the TVIS engave/disengage by a change in power).

If you want one with a small screen and two settings: RPM and throttle %, then I have a few of them made. Wait a little more to see what I end up with for the final version I'll stick with. Also, if anyone knows exactly where T-VIS was used or has a list, my list at www.pampeperformance.com needs signifigant help as of now. Thanks.
 
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