eyecandy

iTrader: (19)

I have been contemplating doing the TB mod. The main reasons is because it is permenant and causes sub 4K hesitations...

How bad is the hestiations and any other draw backs? Or is it even that beneficial? Is it possible to remove the separate linkage that slows the rate of opening and just have it open with the other throttle plates?

On a S4 TII what does the ACV all control? I know sending air to the cat, but does it have anything to do with the cold start assit or BAC valve?

What are the symptoms of a bad EGR? Also what is all involved in removing the EGR? basically keeping it on there and just removing/rerunning the vac lines or whatever is hooked up to it. Or how do you clean/fix it? And is it good or bad to remove it?

NZConvertible

I'll post the same thing here I posted on teamfc3s in case it helps others.

If the throttle is opening suddenly, there's a momentary lean condition as the secondary ports suddenly start flowing, which causes a slight stutter. The damped operation of the TB's #2 secondary throttles stops this occuring, but it also slows throttle response since the throttles are opening slower than normal. Removing these throttle plates noticeably increases throttle response, and you soon learn not to slam the throttle open as quick at lower revs. It's no big deal, and a worthwhile compromise. It also removes the restriction caused by the second set of open throttles.
That would have exacly the same effect (the same stutter would occur since the throttles can open faster), but you'd still have a set of open throttles causing a restriction. The only advantage of doing this is that it could be done without removing the TB and doesn't require the empty shaft holes to be blocked off.
No, it only does three things. It sends air to the exhaust ports (ECU controlled, reduced emissions), it sends air to the cat convertor (same again) and it dumps a bit of air into the intake manifold on deccel to stop popping in the exhaust. It has nothing to do with starting or idling.
There are no advantages to removing it, in fact fuel consumption will increase slightly if you do. It can be tested as per the instructions in the FSM. Removing it involves capping the lines and installing a block-off plate in its place.

RETed

It really only affects under 3kRPM.  Under 2kRPM, the intake charge velocity isn't strong enough for you to be suddenly opening the throttles.  Above that, it's a lean condition which the stock ECU cannot compensate for.

If you change your driving style to compensate for these downfalls, you become a much better driver...


All the ACV does is direct air from the air pump to either the main cat or bypass to the silencer in the front passenger fender corner.  It really has no connection with the cold start or BAC valve.


There are two modes in which the EGR valve fails.
1) EGR internal passages gets blocked from exhaust gas curd - this basically negates the effect of the EGR valve.
2) EGR valve diaphram leaks - this induces an intake vacuum leak on top of have a partially working EGR valve.


-Ted

eyecandy

iTrader: (19)

Thanks for the help guys, a few more questions.

When doing the TB mod, does that get rid of the 3k high idle on cold start? Is it possible to also remove eveything except the plate rod? I more or less do not want to make it permenent by using JB weld...Or just remove the plates and leave everything intact?

Now on the EGR how do you determine if the diaphram leaks?

eyecandy

iTrader: (19)

Also how do you reroute the coolant line?

NZConvertible

No, that's caused by the AWS valve and the BAC valve. If you remove the AWS valve (and you should) it'll only rev to ~1500rpm.
If you remove the plates but not the rod or linkages, the rod can move sideways and jam the lingages. This could be very dangerous. You can remove the linkages and wire the plates wide open. This will provide the throttle response improvement but still leaves a restriction on the TB (the open plates). I did this on my Cosmo without any problems.
Dunno sorry.
You mean after removing the thermowax? You run a line from the nipple on the top of the rear plate to the nipple on the rear of the water pump. Remember that the thermowax doesn't have to be removed as part of the TB mod. It is completely seperate from the double secondary plate system and can be left in place giving you a decent cold idle.

RETed

Yes and no.  There is still an AWS, but it's knocked down to 2k to 2.5k RPM.  The ECU still triggers it via it's own dedicated thermosensor at the bottom of the radiator through the BAC valve.  If you unplug the two-wire sensor at the bottom of the radiator, this will total eliminate any signs of the AWS.


Yes, you can do this.


You'll need a manual vacuum pump.  Stick the hose onto the EGR valve vacuum fitting and pump the hand pump until you see the diaphram move.  Wait a minute to see if it's still open - if it closes, it's bad.


-Ted

RETed

You have three options...
1) Plug both ends
2) Run a hose from the rear iron to the front to the water pump housing - this can eliminate the BAC valve
3) Run a hose from the rear iron to the BAC valve, then from BAC valve to the water pump housing - this keeps the BAC valve.



-Ted

eyecandy

iTrader: (19)

Ok so I can or cannot remove just the plates? I more or less do not want to destroy my TB by doing this mod, incase I would ever like to go back or if I sell it and would want to put it back on..... So how would I do it by not making it permenant?

So if I keep the AWS and BAC then my cold start idle is about 2k-2500 and if I just keep the BAC it is about 1500?

Doesn't the thernowax control the secndary throttle plates? If so, what would be the point of leaving it on?


Is it smart to do this before I install my reman? Or should I do this later after I know it runs?

RotaryRevn

This is what I am pondering myself....I am going to be doing a first gen t2 swap and am thinking about waiting until I get it all up and running before doing the mod so if it won't run, I will know why. Havent decided yet though on what to do

NZConvertible

Yes you can, but do not remove the linkages.
It should be ~3000rpm with both valves working, and ~1500rpm with the AWS valve removed and just the BAC valve working. The TB mod will have zero effect on this.
No, the thermowax only controls the primary throttle. As I said, the thermowax and dual secondary throttle systems are totally seperate and one has no effect the other. The dual secondary throttle system can be removed without affecting cold idle (as I've done).
Do it now so you eliminate one possible cause if you have problems with the new engine.

eyecandy

iTrader: (19)

Can the coolant line be rerouted with the thermowax still on?

Or can the thermowax, coolant line and secondary plates ONLY be removed?

So let me recap, to get rid of the 3k idle, I remove the thermowax,right? Then to get better response I can remove just the plates as long as the linkage is all still connected.. And where does the coolant line come in?

BTW I really want to thank you for the help!

RotaryRevn

Yes, thanks for the help, these are all very good questions and answers!

Pinfield357

rated!

NZConvertible

No. The coolant line is what controls the thermowax. If you remove the coolant flow through it but leave it in place your idle will always be high (1000-1200rpm). The coolant line is only removed/rerouted if the thermowax is removed.
Yes, or you could leave the thermowax in place and only remove the plates. Why do you want to remove the coolant line so bad?
No! For the third time, the AWS solenoid valve mounted on the UIM controls the 3000rpm start, NOT the thermowax or anything on the TB.
Yes!
There's a nipple on the engine's rear plate that connects to the bottom of the thermowax.

Clear now?!

eyecandy

iTrader: (19)

With the secondary plate removed, with sudden blips of the throttle in the higher RPM range, it creates a lean condition?

Could the thermo wax have been the cause of my 1100rpm idle? With the BAC valve completly closed it was down to 900-950 rpm...

I want to reroute the coolant line because it will very slightly lower the intake temps....

Sorry I was at work and typing fast, I meant to say the AWS and with the AWS removed cold start idle is at around1500rpm, right?

Digi7ech

iTrader: (1)

Actually you can keep the BAC and remove the coolant lines. The BAC and coolant lines aren't permanantly connected. Just 2 screws and you can remove the coolant tube on it.

It's just a fixed point for the coolant lines to mount to.

I plan to cap the rear iron and water pump housing and remove this tube from the BAC.

I am also keeping my secondary throttle plates on for laziness unless my turbo isn't fixed within a week. Then I may tap the holes and remove the seconadry stuff.

RETed

The BAC valve has a thermosensor in it, and it will not function properly if it has no coolant line running to it.


-Ted

fstrnyou

DO NOT REMOVE ONLY THE PLATES!!!!! AS STATED BEFORE, THE SHAFT CAN MOVE AND WILL JAM THE THROTTLE OPEN PARTIALLY. this happened to me, so i re-installed the plates and just cut the rod that holds the plates closed. problem solved.

NZConvertible

No it doesn't, it's just a solenoid valve.

Digi7ech

iTrader: (1)

I know someone running without the coolant tubr on their BAC. Their car seems to be fine.

Anyways I live in AZ where it is over 100`F for 200 days a year. The sensor probably doesn't do very much since I doubt the thermowax did.

NZConvertible

The wax in the thermowax doesn't melt until the coolant gets to ~140degF, so it works even in hot climates.