New throttle body isn't the same as old one
10-11-10, 02:24 PM
#1
New throttle body isn't the same as old one
So I ordered a new TB for my 89 T2 from a fellow forum member. Everything looks the same except for one thing. The new TB doesn't have the thermostatic air switch that controls the second set of secondary butterflies in the TB for when the engine is cold. As long as I cap off the vacuum line on the intake it was connected to, is it going to be a big deal? In theory I'll just need to not stomp on the car till its warm right?
10-12-10, 08:31 AM
#4
Here is a photo of my old TB. You can see the little vacuum diaphragm that has a linkage that connects to the first set of secondary throttle plates. There's a vacuum line that goes to a plastic thermostat that's threaded into the coolant passage on the other side of the TB.
Here's the new TB. It lacks the vacuum diaphragm and even the threads that go into the TB for the thermoswitch.
Here's the new TB. It lacks the vacuum diaphragm and the threads for the thermoswitch on the other side of the TB.
Here's the new TB. It lacks the vacuum diaphragm and even the threads that go into the TB for the thermoswitch.
Here's the new TB. It lacks the vacuum diaphragm and the threads for the thermoswitch on the other side of the TB.
Last edited by Bamato; 10-12-10 at 08:34 AM. Reason: silly stuff happening
10-12-10, 08:44 AM
#5
It's been removed, probably to eliminate the minor restriction of an additional set of butterflies (the No. 2 secondary butterflies as Mazda calls them). On a manual transmission car the water thermovalve will allow manifold vacuum to the diaphragm so that the No. 2 secondary butterflies are closed when the engine is cold. When water temperatures increase enough, the thermovalve cuts the vacuum and the No. 2 secondary butterflies will be allowed to open. On the FD the double throttle system is controlled by a solenoid. On the Rx-8 there is an electronic throttle so the vacuum-based system was eliminated completely.
The whole point is to sort of "idiot proof" the car for people who like to beat on cold engines. Just don't drive the car hard until it reaches operating temperature. I would pressure test your engine for boost leaks before you run this TB though. There's always a chance they didn't seal everything up thoroughly. As for the plumbing, well you can cap off the ports on the thermovalve as you said. But you may not even need to do that. Normally vacuum for this system comes from the bottom port on the rear of the UIM, with a check valve in-line.
The whole point is to sort of "idiot proof" the car for people who like to beat on cold engines. Just don't drive the car hard until it reaches operating temperature. I would pressure test your engine for boost leaks before you run this TB though. There's always a chance they didn't seal everything up thoroughly. As for the plumbing, well you can cap off the ports on the thermovalve as you said. But you may not even need to do that. Normally vacuum for this system comes from the bottom port on the rear of the UIM, with a check valve in-line.
10-12-10, 10:56 AM
#6
It doesn't appear to have been a feature that was removed. It looks like it was never there at all. The threaded hole where the thermovalve on my current TB is located, is non-existent in the new one, it was "formed" without one. So I don't think it would cause any boost leaks.
I'm going to take some pictures of the thermowax and such tonight, was hoping you guys could give me an opinion on some of the settings on it. They look a little off.
I'm going to take some pictures of the thermowax and such tonight, was hoping you guys could give me an opinion on some of the settings on it. They look a little off.
10-12-10, 07:41 PM
#7
Here are some pictures.
These two photos are a comparison of where the thermovalve is on the old TB, and where it isn't on the new TB
New
Old
My question is on a few of the settings...
Thermowax on the new TB (looks extended more than it should be?????)
Thermowax on the old TB. I know the thermowax works on this one as my fast idle has never been a problem.
New TB cam location
Old TB cam location:
New TB stop screw
Old TB stop screw
So my question boils down to if it really is necessary for me to even mess with the setting on the new TB at the moment? Reset it to factory spec? Because if I do, it doesn't allow the throttle plate to close after the thermowax activates.
The whole reason I bought a new TB was because I kept getting inconsistent TPS readings with multiple TPS's.....
These two photos are a comparison of where the thermovalve is on the old TB, and where it isn't on the new TB
New
Old
My question is on a few of the settings...
Thermowax on the new TB (looks extended more than it should be?????)
Thermowax on the old TB. I know the thermowax works on this one as my fast idle has never been a problem.
New TB cam location
Old TB cam location:
New TB stop screw
Old TB stop screw
So my question boils down to if it really is necessary for me to even mess with the setting on the new TB at the moment? Reset it to factory spec? Because if I do, it doesn't allow the throttle plate to close after the thermowax activates.
The whole reason I bought a new TB was because I kept getting inconsistent TPS readings with multiple TPS's.....
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10-12-10, 08:08 PM
#8
The stop screw on the old is unlike the stop screw on the new for some reason as the new appears to be spring loaded if I'm looking at the pic properly. More importantly though, the gap at the stop screw should be nonexistent when fully warmed up and not before if I understand it correctly, and I'm using info from the thread I provided you.
10-14-10, 09:30 AM
#16
The cam should completely roll off the roller pin and when it does observe the position of the throttle plates. Take some pics perhaps of the throttle plates. As I understand it the primary throttle plate should be almost completely closed when the thermowax is fully warmed up and extended and until then the primary throttle is vented open which allows more air to enter and thus a higher rpm during early idle. If not, then some adjustments are likely necessary. There are two screws key to the thermowax. One gauges how much the cam moves in relation to the roller pin while the other screw sets the idle speed. These screws in addition to the stop screw are to be involved in a symbiotic relationship helping to provide for a proper idling system and therefore a happy engine. I suggest you read through the link I provided you as it is very educational and should give you the necessary insight into dealing with your throttle body. That and other advanced searches should help to point you in the right direction.
10-14-10, 04:53 PM
#18
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10-14-10, 06:11 PM
#19
^^There are no physical differences. Aside from whats been discussed, they are the same.
Here's pictures of me testing the thermowax.
Thermowax, fully warm
Throttle plate when cold
Throttle plate when hot
The cam roller just barely disengages from the cam when it's totally warm. Think I'll be ok? I want to make a test pipe to sub the intercooler so I can make adjustments, any suggestions? What should I do with the little vacuum line that goes to the PS? Cap it? And the AWS solenoid?
Here's pictures of me testing the thermowax.
Thermowax, fully warm
Throttle plate when cold
Throttle plate when hot
The cam roller just barely disengages from the cam when it's totally warm. Think I'll be ok? I want to make a test pipe to sub the intercooler so I can make adjustments, any suggestions? What should I do with the little vacuum line that goes to the PS? Cap it? And the AWS solenoid?
10-14-10, 06:25 PM
#20
It looks close enough but since you'll be able to fine tune it w/o the intercooler mounted on the engine that will help. One thing though from your pics, the throttle plates are fairly dirty and grimey especially around the edges so cleaning that up as much as possible should help a bit.
10-14-10, 06:50 PM
#21
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the FSM has the spec for the wax pellet hot and cold. also the wax pellets are the same s4/s5 they will pop out of the aluminum casting, which does change s4/s5 and na vs t2
10-14-10, 08:04 PM
#22
It looks close enough but since you'll be able to fine tune it w/o the intercooler mounted on the engine that will help. One thing though from your pics, the throttle plates are fairly dirty and grimey especially around the edges so cleaning that up as much as possible should help a bit.
10-17-10, 06:56 PM
#23
Bolted everything together today. Started it up, fast idle was a little high, so I adjusted the fast idle screw so it was idling around 1900 rpm. After it warmed up, it began bouncing from 1200-1500. If I put it in gear, it would bounce from 800-1100. If I turned on the AC, it would idle steady at around 1200. I was unable to build a test pipe at this time, I bought 2" pvc and its too big around. So I'll have to go back to lowes... Any suggestions?
Forgot to add, TPS is adjusted to one volt.
Forgot to add, TPS is adjusted to one volt.
Last edited by Bamato; 10-17-10 at 07:02 PM.
10-17-10, 10:20 PM
#25
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Car warmed up and idling + can of starting fluid/ carb cleaner = Vac leak location tool.
Spray around near vacuum central... Change in tach, you've got a leak.
I know; real rocket science, in that one, huh?
Spray around near vacuum central... Change in tach, you've got a leak.
I know; real rocket science, in that one, huh?