Enlarged throttle body

[deadmau5]

fozzymandeus said:

Out of interest, (and I've read all the posts, so apologies for not noticing if it's been mentioned) but what was the original application of the modification TB? Was it intended for a larger displacement engine?

To achieve the specific output the 2.0 sport clio engine achieves it'd need a pretty enormous compression ratio and therefore a high air mass flow rate at full throttle anyway.

Most attempts to tune this engine I've seen have resulted in failure, somewhat O/T but aftermarket induction kits are a bit of a no-no in this application. When I bought my F1 it had some kind of K&N universal fit "cold air induction" kit fitted and all it achieved was lots of noise and a loss of linearity of torque.

I dunno. Great cars, sport clios, one of my favourites, but not a good subject for dubious modification. Just buy a VW and put some stickers on it instead

There are a few mods proven to give an increase in power but it's very expensive for relatively small gains.

[ShayneJ]

As the more eloquent posters have said you fitted a larger throttle body
so in simple terms you have moved the "normal" throttle response down
so less peddle input for the same air flow BUT to work the injectors
need to match. it seems you're current set cannot keep up.

More air requires more fuel to maintain the balance.

So you're choices are back to original TB and forget the idea or

higher flow injectors and a remap to suit and enjoy a small gain.

[john banks]

Aside from the wise words about low OEM restriction and throttle position sensor calibration, there are many potential ECU ramifications of changing the throttle body, which should be considered generic although the Nissan ECU I reverse engineered increasingly shares more with Renault as time goes on. If there is a mass airflow meter (likely) and a speed density (or atmospheric pressure and temperature compensated alpha N) calculation as a backup (likely) then the ECU could compare the two with throttle position for plausibility. It may target torque by means of airflow compensation with an adjustment to account for ignition timing.

There can be illusions related to a 14% increase in cross sectional area of the throttle. If you didn't throw fault codes in driving, then you might experience sharper throttle response than OEM, but no extra power at WOT. Even if you saw initial gains that could be "proven" on a dyno, they are very likely to be spurious and not persistent.

If you want useful results from modifying normally aspirated road car engines, whilst keeping them civilised, find something that the factory have deliberately crippled by easily reversible means to sell a more expensive model. Something running c.100 BHP/litre is not a good candidate as it has already been done by the factory.

[Captain Muppet]

FoundOnRoadside said:

Captain Muppet said:

You think an extra 4mm of TB diameter will be enough to max out the injectors at 4,000rpm?

I dunno, that's why I posed it as a question. It was a suggestion.

Renault do run some of their injectors at almost full capacity on standard engines (the 1.2TCE is like this), so there's no margin for tuning.

Injector max mass flow is usually near max revs (unless there is some wacky enrichment to control knock or exhaust gas temperatures).

Also yes, OEMs tend to optimise components correctly - why fit bigger injectors than you need? This is why aftermarket modifications often either fail to work or cause a spiral of further upgrades.