Larger Throttle Body
The original throttle body has a fairly small opening, bigger is better. For the smart 450 and Roadster ONLY. NOT 451.
Thanks to Ian from BIG Performance for the information.
Thanks to Rob from S2Smarts for testing several ideas.
Thanks to Tony from Tune4Performance for possibly solving the idle problem.
This is the throttle body that we are going to fit. It is from a Vauxhall/Opel Z10XEP,
Z12XEP or a Z14XEP engine. These were mainly Corsa engines but where found in
other Vauxhalls too.If you do a search on eBay for XEP THROTTLE you will find some.
Make sure it has the port that the intercooler pipe connects to as the Z10XE, Z12XE and
Z14XE don't have it and they are sometimes incorrectly advertised. Also look for the
inline cranked hoses on the side as another give away to the correct type.
Take a hacksaw and cut the side cranked hose joiner off the throttle body.
Harsh but necessary or the engine cover won't close, these don't enter the throttle body.
With the side cut off, take a look at the comparison between the smart throttle
body on the right and the Vauxhall throttle body on the left. The XEP is far bigger.
You'll need a spacer, I had one made from plastic for testing.
A proper aluminium spacer and gasket can be bought at Smartmods.
Remove the original throttle body and plug in the Vauxhall one. It's a direct fit.
You will need either Forge, Janspeed or Mocal intercooler pipes and a bit of patience to stretch the end over the new throttle body. If you have the Janspeed pipes you can exchange the final silicone pipe for an adapter pipe that goes from the smaller IC pipe to the larger throttle body inlet.
Tighten it all up and give it a go.
The original throttle body was a bit of a bottle neck so this must increase performance.
Considering I bought mine for £35 including postage from eBay, it's worth the try.
Is It Worth It?
I would say that this is a final mod, not an initial one.
If you have a heavily modified car and you are running out of things to do then try it.
In the grand scheme of things it's an easy and cheap thing to test out.
If you just have a couple of mods, I wouldn't bother yet.
Part Numbers And Info
Bosch Artikel Nr: 0 280 750 13
Vauxhall/Vauxhall/Opel part number: 24420536 and 93181025
Vauxhall/Opel Agila (H00) 1.0
Vauxhall/Opel Agila (H00) 1.2 16V Twinport
Vauxhall/Opel Astra G Estate
Vauxhall/Opel Astra G Estate 1.4
Vauxhall/Opel Astra G CC
Vauxhall/Opel Astra G CC 1.4
Vauxhall/Opel Astra G Saloon/Notchback/Saloon
Vauxhall/Opel Astra G Saloon/Notchback 1.4
Vauxhall/Opel Astra H
Vauxhall/Opel Astra H 1.2
Vauxhall/Opel Astra H 1.4
Vauxhall/Opel Astra H Estate
Vauxhall/Opel Astra H Estate 1.4
Vauxhall/Opel Astra H VXR/GTC
Vauxhall/Opel Astra H VXR/GTC 1.4
Vauxhall/Opel Astra H VXR/GTC 1.2
Vauxhall/Opel COMBO Kasten/Kombi
Vauxhall/Opel COMBO Kasten/Kombi 1.4 16V
Vauxhall/Opel COMBO Tour
Vauxhall/Opel COMBO Tour 1.4
Vauxhall/Opel Corsa C
Vauxhall/Opel Corsa C 1.0
Vauxhall/Opel Corsa C 1.2 Twinport
Vauxhall/Opel Corsa C 1.4 Twinport
Vauxhall/Opel Corsa C Kasten
Vauxhall/Opel Corsa C Kasten 1.2
Vauxhall/Opel Corsa D
Vauxhall/Opel Corsa D 1.0
Vauxhall/Opel Corsa D 1.2
Vauxhall/Opel Corsa D 1.2 ecoFLEX
Vauxhall/Opel Corsa D 1.4
Vauxhall/Opel Corsa D 1.4 ecoFLEX
Vauxhall/Opel Meriva 1.4 16V Twinport
Vauxhall/Opel Tigra TwinTop
Vauxhall/Opel Tigra TwinTop 1.4
Some people have discovered that on fitting one of these larger throttle bodies that the idle tick
over on the car fluctuates up and down by as much as 1500 rpm. I didn't find that fault with my car
but luckily enough I found one that did. Rob from S2Smarts tried a few things along with Tony from
Tune4Performance on the project car but the jury was out as to why this was happening.
Faulty throttle body, spring too weak, sensor faults, map data were all looked at and ruled out.
I suggested changing all the internals over from the OEM throttle body to the new one.
Tony took the 2 apart and noticed a big difference in the resistances of the resistor tracks
on the internal circuit board so just swapped the back plate over and gave it a go.
So far, it would seem that doing this, possibly in conjunction with disconnecting
the battery for 5 minutes will sort this fault out. More testing is being done.
This is the back plate, removal can be seen here. The red quadrant highlights the resistor tracks.
Take the smart back plate and fit it to the new, larger throttle body, then fit to the car.