arghx

iTrader: (3)

I mean seriously, besides engine bay simplification, can anyone show proven and demonstrable performance gains from this?

I say this because I had an s4 n/a without the TB mod (or at least, most of the stuff was on there), and then I bought a T2 with the full TB mod and I find driveability hampered and the car is just annoying sometimes.

I am looking at page 4-24 of the training manual.

http://mazdarx7.iougs.com/Training/4...%20Systems.pdf

Let's consider the components here:

dashpot -- reduces chance of the car stalling after you let off the throttle quickly

thermowax/fast idle cam -- keeps the car from stalling when cold

double throttle system -- Reduce low throttle hesitations? Now this seems questionable to me. I also understand that it's there to keep you from letting too much air into a cold engine, but beyond that it's just a bunch of bullshit in the engine bay. I don't think I want to put this back on my car.

water thermovalve -- this is part of the double throttle system and needs some vacuum lines and coolant or something.

Does anyone have any kind of dyno sheet showing the benefits of removing these things? Either way, I guess what I really want to put back on my car (s4 T2) is the dashpot and the thermowax. I just hate having to keep my foot on the gas when it's cold. I understand some of you will think that I am just being a whiner, but the point is that the full TB mod is hampering my enjoyment of the vehicle.

I'm currently trying to find an unmodded s4 T2 throttlebody. Should I just then remove the double throttle plate actuator thingies and the thermovalve, while retaining the dashpot and thermowax/fast idle cam? I still need a coolant line to the TB for the thermowax to work correctly. Can I use the stock one? Or is it not possible to "cherry pick" your TB modifications? I'm just trying to figure out how I would go about doing a "1/2 throttle body mod"

http://www.mazdatrix.com/bhose2.htm

Hypertek

iTrader: (3)

search for tb mod
theres a thread where a guy actually did some bench testing on a modded and unmodded tb and had numbers to show it allowed for more air travel /cfm. Would be more beneficial for turbo cars, or cars where you dont really care for how it idles. I dont know if thats been done to my fc but its something i want to check out.

edit- heres the thread https://www.rx7club.com/showthread.p...OTTLE+BODY+MOD

NZConvertible

Personally I think the phrase "TB mod" is misleading. People assume you have to remove both the double-throttle system and the thermowax, but this is completely untrue. The two systems are completely unrelated and perform two completely different tasks. They have no effect on each other and have different pros and cons. You can remove one without affecting the other at all. The TB mod should be regarded as two different mods, not one.

IMO removing the thermowax is a bit silly unless you have another means of increasing the idle speed when the engine's cold, like a programmable ECU controlling the BAC valve.

The double-throttle system is different for NA and turbo engines. On both engines the upstream secondary throttles are held closed when the engine's cold to prevent idiots romping on the engine until it's warmed up. This is controlled by the thermovave, which is screwed into the side of the thermowax. It opens and closes a path for manifold vacuum to act of the double-throttle actuator. Once the engine warms up, the two TB's act differently.

On NA's once the coolant reaches ~140degF those throttles open and stay open until the next cold start. This is why removing them has so little effect. The TB is huge for the NA engine's power, so there's just not much gain there to be had. The air is already disturbed by the downstream secondary throttles, and two sets of open throttles don't make this twice as bad.

On Turbos once the coolant reaches ~140degF those throttles close and then move in sequence with the downstream secondary throttles (i.e. they open when you press on the gas pedal), except that their opening rate is slowed by a damper so that you can't open them too fast. Because of the delay between the throttles opening and the AFM sensing the change in airflow, opening them too fast at low rpm results in a brief lean spot that will cause the engine to stumble briefly. The reason Turbos need this and NA's don't is because of the much longer path between the AFM and TB. This is only an issue at low revs, Above ~3000rpm it makes no difference.

The downside of the Turbo's damped double-throttle system is that because the system works even when not needed, high-rpm throttle response suffers. Removing the double-throttle system provides a noticeable and worthwhile improvement in throttle response. This is not something you can see on a dyno for obvious reasons, but it is a definite benefit. The downside to doing this is going to be the stumble problem described above, but this is simply a matter of learning to avoid it. This will actually improve your driving style, as there's no point or need to be slamming the throttles open at low rpm.

If the TB mod causes constant drivability problems then something is wrong, because that's not normal. Even if you do open the throttles too fast at low rpm, you should only get one short, mild stumble. It's not a big deal, it's just not something you expect on a production car which is why Mazda did something about it.

Note that the flow bench testing referred to above gives a very exaggerated indication of the performance improvement. There are many other restrictions all the way from the intake to the exhaust tips, and some of them are far more restrictive than the TB.

RRTEC

iTrader: (13)

The point is to screw up your idle...

arghx

iTrader: (3)

my main gripe is removing the thermowax, which the previous owner did and I'm not happy with. I can deal with everything else.

so starting with an unmodded throttlebody, if I want to keep the thermowax but remove the double throttle system, how do I run the coolant lines? Do I need the thermovalve to retain the thermowax? I will not have a BAC. And I can retain the dashpot right?

On the stock TB doesn't coolant go from the rear iron to the thermovalve, to the throttlebody, then to the BAC, then from the BAC to the water pump housing? I guess I have to run coolant from the rear iron to the TB and then to the waterpump housing?

gxl90rx7

iTrader: (1)

on my s4 n/a, the 2ndary throttle plates were completely vacuum controlled. you can remove it without affecting the thermowax operation at all. the thermowax uses the coolant lines to expand a cylinder which pushes down on the throttle, raising the idle when cold. should be self explanatory if you look at a stock setup

i have the same problem on my TII, someone removed the thermowax, what a pita. i have a spare thermowax but cant figure how it went on stock. anybody have pic?

NZConvertible

If the TB mod screwed up your idle, then you screwed up the TB mod. Other than cold idle if you remove the thermowax, idle quality should be completely unaffected.

You don't touch the coolant lines, you leave them as they were.

No, but there's no point in touching it other than removing it's vac lines.

Why not? That makes as much sense as not having a thermowax.

It's completed unrelated and unaffected.

Rear iron > thermowax > BAC valve > water pump.

If you don't have a BAC valve then yes.

arghx

iTrader: (3)

i'm sure all this routing will become apparent when I get my hands on an unmodded TB, something I've never actually worked on before. As far as the BAC goes, i stupidly cut the damn connector off the harness plus routing the coolant line around will be difficult with the way I have stuff set up right now. I'm not ruling out putting it back on, but it's just one more part to chase down ( I don't have one right now).

Thanks for the help.

NZConvertible

You're right, it's pretty clear when you see it. The coolant inlet is on the bottom of the thermowax and the outlet on on the top of the TB. There's a couple of pics in the FSM Fuel Systems chapter that show them.

SpeedOfLife

iTrader: (16)

Could a broken TB assembly cause my motor to seem like it cuts out at a certain RPM? NZ, you mentioned how it could screw with the high RPM performance of the turbo models and I still haven't figured out why my '87 TII seems to hit fuel cut right at 6500RPM, regardless of boost level and I guess it doesn't even have to be at WOT... So maybe not, but I thought I'd ask. I do know that the little plastic piece on the secondary butterfly rod is broken, I think it's supposed to act as a stopper.

blmcquig

iTrader: (15)

very good information NZ.

i myself removed everything, in order to make working on the car much easier. i dont have any drivablility problems, and during autocrossing, i dont feel much if any lag in the lower rpms.
also, have an 87TII. i think that setting things up correctly, and making sure you have NO (cant repeat this enough; NO NO NO!!) vaccum leaks at all will make this mod much more worth it. If you half-*** it, and dont take you time, you will see the results of that, too.

NZConvertible

I can't see how, all the TB does is regulate airflow based on you right foot. Cutting out would indicate a fuel or ignition problem.

No I didn't. The TB mod should have no effect on high-rpm performance.