6 replies to this topic

[Terho]

Hey, what co2 emissions do your supercharged or modified cars have at MOT? How much emissons does a sc add to a vx with proper tuning? The problem I am facing is that where I live the co2 emssions can only be 0,2% in 2000rpm    and I am planning to do a sc conversion in the future but a yearly disconnecting seems a bit much... 

 

Thanks Terho

[Ivor]

I think UK is measured in CO2 gramms per km, so not sure what you mean by 0,2%. Mines a stage 4 turbo and passes UK emissions, but I'd need to check the mot certificate for the CO2 readout, not home till 11 Jan, I'm sure someone else will pipe up before then though

Edited by Ivor, 30 December 2019 - 04:06 AM.

[jonnyboy]

SC with a cat should be normal. ITBs no chance.

[Arno]

Hey, what co2 emissions do your supercharged or modified cars have at MOT? How much emissons does a sc add to a vx with proper tuning? The problem I am facing is that where I live the co2 emssions can only be 0,2% in 2000rpm    and I am planning to do a sc conversion in the future but a yearly disconnecting seems a bit much... 

 

I suspect you mean CO?

 

0.2% is the normal EU3/EU4 MOT limit at 2500rpm (0.3% at natural idle)  and an SC'ed car with a good working cat converter will have no problems meeting that.

 

It will/should not react any differently from the normally aspirated situation as there's no load on the engine so the SC bypass valve is open and it's just free-wheeling along.

 

The normal ECU (with new software if you switch to something like http://www.obdtuner.com/ ) will do the normal fuel control with the lambda feedback as usual.

 

With ITB's it is still quite possible, but it gets more involved and needs a lot more work as you will need to run a completely new ECU that can handle such a setup and then you'd need a good mapper and rolling road to set it all up, including the 4/5-gas emissions at idle. Also may need some checks/tweaks befor each MOT to get it to pass well. Still.. This is usually the only way to get an N/A car with wild cams to run well and pass emissions.

 

Bye, Arno.

[Terho]

Yeah co of course and it would be perfect since if I do either of them, it will need to be tested by an independent research facility for all emissions by first letting the car sit until it's cold and then simulating road driving on dyno and collecting all exhaust gasses... And all this costs 1000€   

[Mat Jackson]

A well set up itb car should pass mot emissions without any issues


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[Arno]

If you need to do a full drive-cycle for re-certification then it's usually best to do the minimum changes initially so you change the base car as little as possible.

 

Get it (re)tested with the new engine configuration and once it's approved you can then usually work within that new setup to get your desired config.

 

Eg. on a SC you would probably want to install all the bits, make it chargecooled if wanted, but run it with the completely standard OEM exhaust and cat (with pre-cat!) setup and use a big pulley on the SC so it makes only a tiny bit of extra power. Aim for around 200HP max.

 

That should have no problems to pass the drive-cycle tests including any noise tests. (likely you will be classed in a higher CO2 kg/km class though..)

 

After that you can of course do more 'stealth' modifications like going to a smaller pulley, better exhaust with a sport-cat, etc. so in the end you sould be able to get 260hp or so out of it and still pass regular yearly MOT tests as from the outside it all looks the same 

 

With an ITB setup the best would be to do nothing at all to the engine itself from it standard normally aspirated form (no cam change, no head work, no pistons, etc. etc.) and only get the ITB's working and make sure all emission related bits are working well and that it's mapped properly with good closed-loop lambda control. Extra care needs to be taken on these to get the noise down as that will likely be a part of the test, so some enclosure around the ITB's and a common air filter (perhaps even re-use the normal filter and housing).

 

It should really not make any extra power at this point and if you have it re-certified with ITB's it should also get pretty much the same  CO2 kg/km rate as the engine is still the same 147hp N/A, just on throttle bodies. Properly mapped for good cold start and warming up strategy it should be able to reach similar emission levels.

 

Once that's done then you can open up the engine and start bumping compression, cams, valves, etc, etc, etc... 

 

The SC will likely be the least difficult path to take as that keeps virtually all OEM parts including the (re-programmed) OEM ECU with all it's emission strategies and the SC itself is an OEM GM part too.

 

Bye, Arno.