Modifying the 48mm Throttle Body

Re-assembly is now just a case of rotating the spindle, inserting the disc and fixing with the two screws. Your throttle body should now look like this







which is a vast improvement in air flow compared to what you started with or the SU plastic bodied throttle






Refitting the throttle body is simply the reverse of removal.

Just make sure you reconnect the throttle cable first then fix the four bolts and finally the two rubber hoses not forgetting the throttle position sensor plug like I did first time wondering why the car was sitting at 1800 revs in idle.

After moving things around or replacing a throttle body you need recalibrate the throttle position sensor.

To do this follow this simple procedure;

1. With the engine off, insert the key and turn to position 2, all the instrument check lights on, without starting the engine.

2. Press and release the accelerator pedal 5 times, using all of the accelerator pedal travel.
This will let the ECU calibrate the throttle position.

3.Turn the ignition off, remove the key and wait for the ECU to power down saving the new settings. This normally requires about 20 secs.

4. Start the car in the normal way. The throttle should now be reset.


Go for a drive, but do remember to let the oil temp get up before revving over 3000 rpm, now enjoy the difference, more torque at the low end and a more responsive throttle. With my K&N 57i I could also hear a difference.

An excellent modification, Paul! :thumbsup:

Something to add to the list! :yesnod:

You could have also knife-edged the leading edge of the butterfly, to increase air flow. :yesnod:

Looks like it should make a good bit of difference. Am I the only one who would be worried about the solder falling out though? :ohmy:

gotenks1321 wrote: Looks like it should make a good bit of difference. Am I the only one who would be worried about the solder falling out though? :ohmy:

I thought about that, but the thread in the hole should keep it secure. :yesnod:

David Aiketgate wrote:

gotenks1321 wrote: Looks like it should make a good bit of difference. Am I the only one who would be worried about the solder falling out though? :ohmy:

I thought about that, but the thread in the hole should keep it secure. :yesnod:

Ah yes, of course. I was thinking he'd smoothed the hole for some reason when he's just cleaned it up :silly:

I'm going to have to go and look at my 52mm now whilst I've got the filter off to see if it's the same setup.

gotenks1321 wrote:

David Aiketgate wrote:

gotenks1321 wrote: Looks like it should make a good bit of difference. Am I the only one who would be worried about the solder falling out though? :ohmy:

I thought about that, but the thread in the hole should keep it secure. :yesnod:

Ah yes, of course. I was thinking he'd smoothed the hole for some reason when he's just cleaned it up :silly:

I'm going to have to go and look at my 52mm now whilst I've got the filter off to see if it's the same setup.

Tbh, I was surprised that there was a wedge on there, I don't think I've ever seen it before.:shrug:

The wedge was originally there to make the throttle response more subdued, making the car more drivable by anyone around the supermarket car parks (not late at night doing doughnuts :lol: ).

Regarding the solder.

I chamfered the holes on both sides and heated the disc until it was hot enough to melt the solder with ease. Thus the shape of the solder is a sort of I (capital I) in profile so it cannot fall out and as long as the area is clean and the disc hot enough you will get a permanent bond.

Regarding feathering the leading edge, yes you can do that but be careful not to damage the sealing edge otherwise when the throttle should be closed you could get air entering. I reckon the improvements gained by removing the wedge are very large compared to the small extra gain from feathering the edge.

PQD44 wrote:

Refitting the throttle body is simply the reverse of removal.

Just make sure you reconnect the throttle cable first then fix the four bolts and finally the two rubber hoses not forgetting the throttle position sensor plug like I did first time wondering why the car was sitting at 1800 revs in idle.

After moving things around or replacing a throttle body you need recalibrate the throttle position sensor.

To do this follow this simple procedure;

1. With the engine off, insert the key and turn to position 2, all the instrument check lights on, without starting the engine.

2. Press and release the accelerator pedal 5 times, using all of the accelerator pedal travel.
This will let the ECU calibrate the throttle position.

3.Turn the ignition off, remove the key and wait for the ECU to power down saving the new settings. This normally requires about 20 secs.

4. Start the car in the normal way. The throttle should now be reset.


Go for a drive, but do remember to let the oil temp get up before revving over 3000 rpm, now enjoy the difference, more torque at the low end and a more responsive throttle. With my K&N 57i I could also hear a difference.

So this is what I have to do, and all I have to do, if I replace my 48mm body with a 52mm body?

:yesnod:

PAUL, my 1996 MGF has an alloy throttle body on it, which was replacing the plastic one. very, very difficult to read the codes printed on the top , tried rubbing it but made it worse, as far as i can see the code is TV6 unable to read the other numbers even with a high intensity light. I have a loupe, see if that works :slapme:

If it looks like a 6 then it's probably a 5 and someone has done you a favour and replaced the original with a 52mm throttle body. The way to be sure is to just measure it.
The other numbers are not needed to identify the size.

Paul

i think only the 48mm has the wedge on the butterfly, so no wedge and alloy means a 52mm TB

T