Throttle Body Question

[ed94r]

OBD1 Throttle Body.

When the throttle is fully open (car off!), the throttle plate is not at 90* to the bore. It is actually about 94-95*...somewhat blocking the inlet air path. I checked and ALL the OBD1 throttle body's I inspected (4) are like this. Is there a reason??? I tweaked my TB so that the plate opens at 90* but I'd love to know why the factory does it differently.

I looked at an aftermarket OBD1 Big bore TB and it's plate opened exactlly at 90* to the bore. Is there free horsepower in adjusting the plate on the stock TB?

Ed

[Mike B.]

Most, if not all, stock throttle plates that I have looked some additional play like this. Just adjust the throttle cable so the plate is at 90 degrees when the pedal reaches the stop.

[ed94r]

Thanks 4 the quick reply.

The cable's good. When the throttle pedal is pinned, the throttle plate is pinned. It seems to me that if you adjust the cable to the full opening of the TB (when it hits the stop at the TB) the plate shoud be at 90*

What I'm getting at is when the throttle plate is opened, it rotates PAST 90 degrees, to about 94-95*. I adjusted the throttle plate adjuster so that when floored, it opens to 90* and not past 90* like stock. BUT, all the OBD1 TB's I've seen overrotate the throttle plate to about 94-95*. I'd like to know why? Is it engineered that way for a reason? Is it tuned to work this way with the manifold? Is BMW accounting for stretched/maladjusted cables to fully open the TB? It seems to me as tho it restricts airflow...

Remove your air intake boot at the TB and take a look. Pin the throttle and see if your plate goes to 90* or past 90* like I'm seeing.

Aftermarket TB's go to 90* at the stop and not past it , unlike the stockers.

Ed

[aeryk7]

This is true and thus why i readjusted mine to near flat lock up or 90 degrees

[tonytony]

i never noticed this, i shall take a look and report back when i get a chance

[1990m3]

mine sits at perfectly at 90 at full throttle. Never adjusted since new

[aeryk7]

Could have already been adjusted.


-I noticed this same throttle boddy issue on my previous e36 m3's and both at full throttle would over-rotate to about 10 degrees past 90. However it wasnt quite noticeable when the engine was in the car . When i had my s50 on the engine stand i noticed this issue cause i could get face to face with it.

-If you look on the throttle body there are pins to control how far until lock up dont worry about playing with the cable.

[DanThe]

If you look at the linkage there is a tab that hits an adjustable stop (screw)
This can bend slightly depending on how well the cable is adjusted and how heavy the drivers right foot is :)