60mm vs 65mm throttle body?

[jimmyhackers]

theoretical/possible gains between the two?

cars a 306 gti6

2.0l NA engine already at 167ish bhp from factory.

the intake port on the inlet manfold is already about 65mm as is. i did a light rework/flow of the throttle body with some improvements felt, then went and found a throttle body that was 65mm and wondered about just swapping to that.

thoughts?

[E-bmw]

Did similar on an e36 & r53.

ANY restriction removed CAN help. whether it is noticeable or not may be a different question.

[stevieturbo]

I'd be very surprised if it made any difference.

And then the TPS would need to be set to the same parameters as original, and if it did make any difference which it might do low down at smaller openings....the ecu may need adjusted to suit any different airflow at various throttle openings.

But I doubt it will actually offer any more power, just a different feel relative to same throttle position.

[GreenV8S]

jimmyhackers said:

i did a light rework/flow of the throttle body with some improvements felt,

"Felt"? If you aren't measuring, it's very easy to convince yourself that you've made an improvement when you haven't. It seems to me unlikely that a production part would have such problems that light rework made a measurable difference. If you want to know whether it's worth upgrading the throttle body, measure the pressure drop across it at peak power - that will give you a sense of the upper limit on the potential power gains. Changing the throttle body size could affect driveability too - maybe not for the better.

[richhead]

GreenV8S said:

jimmyhackers said:

i did a light rework/flow of the throttle body with some improvements felt,

"Felt"? If you aren't measuring, it's very easy to convince yourself that you've made an improvement when you haven't. It seems to me unlikely that a production part would have such problems that light rework made a measurable difference. If you want to know whether it's worth upgrading the throttle body, measure the pressure drop across it at peak power - that will give you a sense of the upper limit on the potential power gains. Changing the throttle body size could affect driveability too - maybe not for the better.

This is very true, manufacturers dont tend to throw on any size throttle body just because they had some kicking around, they know how to build things more than a bloke in a shed does, they may have not been looking for peak power etc, but it will be that size for a reason.

[jimmyhackers]

thanks for info,

your right, a butt dyno is not accurate. but it felt a big peppier all over the revs especially lower down, and i noticed the intake note changed slightly aswell.

they didnt throw a random throttle body on from factory and it was all calculated....they did make thousands of those throttle bodies (at cost) so there was a fair amount of gains in turbulence reduction to be had with what i did. they even put it on the v6 engine so it was sort of a "what we got in the french parts bin?" type deal from peugeot.

bad casting, combined with bad machining meant there were a fair few mold lines, steps, shelves and other artifacts left over from a "rushed" production line.
by design it blocked/ovaled itself on either side to slow/block where/when the butterfly valve opened partially and restricted its inner diameter more than the 60mm valves area when fully open.

the system is 76mm intake piping to a 60mm TB, then a 65mm inlet manifold hole, the intake runners in the plenum are 4x45mm so they equate to a 90mm diameter hole. so the TB area is the restriction in the setup.

ive seen claimed 180ish bhp (+13bhp) with individual throttle body kits but £1-2000 vs a sub £100 single 65mm throttle body (same bolt hole pattern)......and to get any more power from ITBs you need cams+ecu tune....so i imagine there is a "limit" to TB enlargement gains.

thought it'd be worth a try/laugh.