Combining two stock TBs
Combining two stock TBs
(OP)
This question might be in the wrong place because it's almost an EE question but here goes. I'm building an intake manifold and would like to use two TBs from dodge stealths on it, aka 3000gt. The ECU I plan on using has output for a stepper motor, but in this case I would have two. I'd be able to control the stepper as much as i want but I cant for the life of me think of how to wire the two of them together. I've found a site that has a lot of model specific information on these motors . . .
http://www.stealth316.com/misc/dsm_tech_manual.pdf
I know it's a large file, but the pages I'm talking about are pg 156 - 165 they have everything about how the motor works, more than enough information. If it's possible to use these ISC servos I'd like to.
If anyone could help me it would be greatly appreciated.
Thanks!
Dan
Also these throttle bodies have a coolant input that has an open passage when the engine is cold and closes when the engine gets warm, I'm not planning on using these at all.
http://www.stealth316.com/misc/dsm_tech_manual.pdf
I know it's a large file, but the pages I'm talking about are pg 156 - 165 they have everything about how the motor works, more than enough information. If it's possible to use these ISC servos I'd like to.
If anyone could help me it would be greatly appreciated.
Thanks!
Dan
Also these throttle bodies have a coolant input that has an open passage when the engine is cold and closes when the engine gets warm, I'm not planning on using these at all.





RE: Combining two stock TBs
RE: Combining two stock TBs
RE: Combining two stock TBs
Why double the idle control? Each would flow half as much air as designed for and sloppiness would double.
RE: Combining two stock TBs
FYI, twin throttle bodies are quite common on V8 engines, GM applications use stepper motor idle air control, so you might be able to find yourself a ready made solution instead of cobbling one together yourself.
RE: Combining two stock TBs
RE: Combining two stock TBs
RE: Combining two stock TBs
Now, if you had some special reason for very high flow idle control valves (rally style anti-lag system for example) then it may be worthwhile to think about double idle valves. Otherwise, keep it simple!
RE: Combining two stock TBs
Franz
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RE: Combining two stock TBs
RE: Combining two stock TBs
RE: Combining two stock TBs
RE: Combining two stock TBs
The problem your facing is keeping the throttle bodies balanced throughout their operating range and won't be as simple as tying the plates together with a common linkage, you'll have to control the IAC's individually to keep the intake air balanced between the 2 sides or your gonna have idle problems as well as mixture imbalances, and when the IAC passages start to carbon up (whick won't be identical between the 2 throttle bodies you'll need to compensate one or the other. You'll prolly end up completely closing the IAC passages, tying the 2 throttle plates together with a common linkage, then repositioning the TPS to some point to convince the ECM that the plate is closed (even tho it's not- to allow the engine to idle), and hope that both throttle plates carbon up evenly,or your back where you started.
I'd say your best bet is to take a lesson from BMW and run 2 seperate ECM's (one for each side of the engine).
RE: Combining two stock TBs
That is the way the few TB's that I have work on were setup too. But they all had screw adjustable throttle stops, some under a pressed in cap. I have not done dual TB's but on singles I usually adjust the throttle plate such that the stepper is just open a couple of steps when the engine is warmed up and idling under optimum conditions. That way the stepper is not hitting bottom routinely and the engine should not stall if the ECM over reacts or if a little carbon builds up in the stepper passageway. If you start out with both butterflies open evenly or the one without the stepper open a little extra you should be okay. Will you be running seperate closed loop systems from each plenum cylinders?
RE: Combining two stock TBs
Do you ever use min idle spec ?? It basically is a mode in the ECM that forces a fixed timing and closes the IAC completely so that you can adjust the closed throttle position (and base TPS position), otherwise your gonna get starting problems, idle speed fluctuations (hunting), off idle hesitation, incorrect idle maps, etc.
Just curious is all
RE: Combining two stock TBs
RE: Combining two stock TBs
Forget about how hard these guys are making it out to be it doesnt really matter whether the thing idles or not, you just have to be a bit canny with the throttle pedal - or keep a throttle plate cracked open slightly and let it find its natural idle speed. Its not like you a have an FTP-75 to pass...
MS
RE: Combining two stock TBs
I agree with Matt, go for it. The small passage between the plenums will allow it to balance at idle. MPI will take care of the mixture.
Lord,
I have not used the min idle spec. I just kept increasing the butterfly opening until the aldl said the stepper counts were down to 2-3. I understood that the ECM would recalibrate for the base throttle position on the next restart.
RE: Combining two stock TBs
Don't try to wire your IAC's in parrellel, just close em off completely and run a pipe between the 2 throttle bodies BEHIND the throttle plates and rig a single IAC motor to feed that pipe. That should keep the idle problem managable. Don't forget to run your inlet hose into your air cleaner.
Then tie the throttle plates together with a single linkage and only use 1 TPS to tell the ECM what the throttle is doing.
The computer will think you still have 1 throttle body (even tho' you have 2), but you'll still have to calibrate your connecting linkage. It's similiar to carb balancing on a multi-carb motorcycle.
Good luck
RE: Combining two stock TBs
The cavity and air passages for the IAC on most cars are somewhere between quite and extremely, simple. There is no reaon you can't relocate an IAC to the balance port or other shared air flow. Many "foriegn" cars have separate or external IAC's. BMW used a hose mounted unit for years. This might also open the door to using a different or larger IAC.