1*2 throttle body - enlarging

[Cr33do]

Hi folks,

This might have been covered countless times before. Sorry if it has but a quick search didnt throw much up.

As our track car is off the road for a while (engine rebuild/replacement) I am trying to look at other parts that could yeild improvements to performance. We already have matched inlets, which I plan to check how well these have been done, but the throttle body hasn't been touched.

My question is, rather than smoothing the step on the body can you go further than that and increase the entire (or majority) of the bore? No measurements have been taken yet, or an attempt to strip the TB but I was thinking down the lines of 2-3mm increase of bore and new larger throttle flap to fit accordingly.

In addition to this, I remember reading (quite a few years back) David Vizards book about tuning the A-series engine. I know things have moved on leaps and bounds since then but knife edging the throttle flap was recommeded and even cutting back the flap pivot shaft to reduce restriction on WOT.

Costs for us to this would be next to nothing, and it would provide a ncie little sub-project, but I wonder if other people have tried it in the past? Comments, thoughts and previous experience welcome

Cheers,
Nick

 

[BIGASH]

I'm sure someone on here had done something similar and I don't remember the gains been massive but everything is worth a try! I'm sure you could make some improvement

 

[Martin_172]

didnt someone on here a few years ago knife edge their throttle body and it ended up in the cylinders? lol

 

[Cr33do]

LOL - not good!

didnt someone on here a few years ago knife edge their throttle body and it ended up in the cylinders? lol

 

[marinemackay2003]

Getting lower profile bolts would help flow too

Did matt @ tdf not have something similar done

Sure it was mentioned in one of his threads somewhere

 

[Cr33do]

Getting lower profile bolts would help flow too

Did matt @ tdf not have something similar done

Sure it was mentioned in one of his threads somewhere

Correct - I remember the bolts being modified in the DV book too. These don't look too bad though. Will try and search for some of the TDF posts. Cheers

 

[Andyman]

On the old forum modding the TB was said to be a total waste of time with no gains to be had. No idea if its true or not in practice?

IIRC Jenvy did an enlarged single one for the Clio Sports. Obviously the rest of the inlet track prior would need to be enlarged to benefit.

If you wanted to go down this route could you not nab one off a different car down the scrappies?

 

[rosco454]

My solution would be to countersink the bolts into the throttle spindle (have also read the Vizard book but cant for the life of me remember what the bolt mods were).

Cheers Ross.

 

[sand6000]

I have enlarged the dia of a spare 172 throttle body that I have by 5mm BUT when I reconnect it to the car the throttle pedal has no effect. Have rebooted the computer but no luck. All it will do is idle. Is the ECU not recognising the modified unit perhaps??
Any thoughts anyone please.