ChapmansTailpipe
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| posted on 9/7/14 at 11:32 AM |
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Engine selection - pre or post cat?
I'm choosing a donor engine and am aware that pre-95 units are pre-cat legislation and this is good because:
- no cat (cost+performance)
- less stringent emissions testing
My problem is that these donor cars are now almost 20 years old and I'm having a hard time finding one.
Am I wasting my time and should I forget the pre-cat advantages and just get a more recent, post-95 model?
I would appreciate any advice
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loggyboy
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| posted on 9/7/14 at 11:47 AM |
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Any argument that pre cats will be more powerfull could be countered with more modern engines being better designed and able combine equal or better
performance with stricter emissions and better economy.
Also depending on how you plan on registering the car then it may not matter - Ie a Q plate will only be tested for visible smoke for MOT, so you
would only need to worry about emmisions for IVA, after which, parts be swapped/removed, or conservative mapping/setting up can be adjusted in favour
of performance.
Mistral Motorsport
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pekwah1
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| posted on 9/7/14 at 11:51 AM |
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Is this for a build prior to IVA?
I went with pre-cat because i thought it would be easier but still failed emissions tests the first time.
If you have a modern engine that needs a cat, i believe many people on here have done so without much hassle at all.
Depending on your intentions for engine setup, i don't think you should struggle too much
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Smoking Frog
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| posted on 9/7/14 at 11:52 AM |
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Depends on the manufacture. Some older ones are still good performers. In my opinion stick with newer engines and install a cat. Welcome to the
forum.
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Mr Whippy
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| posted on 9/7/14 at 12:03 PM |
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Mind too if this is really a 'new' car that in the future you will need spares and parts. Unless it is a popular engine like a pinto etc
you may find getting hold of engine parts difficult to get hold off.
I've been put off a few modern car engines (ones that were low miles and free) that were available for my old tin top just because I could not
guarantee that I could get the spares in the future, especially the electronics. I can see it being a Nissan/Ford hybrid in the future 
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Slimy38
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| posted on 9/7/14 at 12:05 PM |
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I went for an early mark 1 MX5, they came out early enough to avoid the cat restrictions but are still very capable engines. And they can have a lot
done with them.
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ChapmansTailpipe
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| posted on 9/7/14 at 12:13 PM |
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Thanks for the warm welcome and the quick responses.
To add some meat to the bone, it's a GKD build so it's a 3-Series donor I'm on the scout for.
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coyoteboy
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| posted on 9/7/14 at 12:49 PM |
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quote:
Any argument that pre cats will be more powerfull could be countered with more modern engines being better designed and able combine equal or better
performance with stricter emissions and better economy.
Also depending on how you plan on registering the car then it may not matter - Ie a Q plate will only be tested for visible smoke for MOT, so you
would only need to worry about emmisions for IVA, after which, parts be swapped/removed, or conservative mapping/setting up can be adjusted in favour
of performance.
This was my opinion. Bought a cat engine, will fit cats for the IVA and will have absolutely no problem passing emissions and will then pull them off
because I'm going Q plate and the emissions limits are not as strict.
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40inches
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| posted on 9/7/14 at 01:40 PM |
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You should be aware that, post IVA, the V5c will in all probability have the emissions that you passed IVA with printed on it.
Mine passed emissions better than post 2002 limits, with a 1998 carbed engine, that is the limits I will have to pass when MOT is due 
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deezee
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| posted on 9/7/14 at 04:39 PM |
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On the IVA, it sets the emissions the vehicle needs to pass. This is undertaken by VOSA and entered in the vehicle database against that vehicle.
How the DVLA choose to license and tax the vehicle (Q reg or age related) won't change your Vosa V5C emissions.
That being said, some garages only do a visible smoke test on a Q plate. Others will go off the database. So your really rolling the dice when it
comes to MOT, hoping you get an easy going garage.
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mcerd1
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| posted on 10/7/14 at 07:29 AM |
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quote:
Originally posted by 40inches
You should be aware that, post IVA, the V5c will in all probability have the emissions that you passed IVA with printed on it.
Mine passed emissions better than post 2002 limits, with a 1998 carbed engine, that is the limits I will have to pass when MOT is due
^^ that doesn't sound right to me, I thought that if it didn't have an entry for your model in the database then you follow the same
flowchart as the IVA test
also if the engine is older than the chassis you can use this from the MOT manual:
quote:
Vehicles Fitted with a different engine
Test according to which is older, engine or vehicle.
e.g. A 1995 car fitted with a 1991 engine (of whatever make), test to 1991 standards for emission purposes.
Note: The onus is on the vehicle presenter
to prove engine age.
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loggyboy
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| posted on 10/7/14 at 08:45 AM |
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quote:
Originally posted by deezee
On the IVA, it sets the emissions the vehicle needs to pass. This is undertaken by VOSA and entered in the vehicle database against that vehicle.
How the DVLA choose to license and tax the vehicle (Q reg or age related) won't change your Vosa V5C emissions.
That being said, some garages only do a visible smoke test on a Q plate. Others will go off the database. So your really rolling the dice when it
comes to MOT, hoping you get an easy going garage.
Mot Manual specfically states than Qs should be tested for visable smoke only. If a tester doesnt then it should be queried.
Mistral Motorsport
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deezee
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| posted on 10/7/14 at 09:22 AM |
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quote:
Originally posted by loggyboy
Mot Manual specfically states than Qs should be tested for visable smoke only. If a tester doesnt then it should be queried.
Not the best photo, but you are certainly correct. Regardless of the flow charts and the IVA man, the MOT handbook (issue date April 2013) says Q
plates are visible smoke only. Pretty Awesome!
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whitestu
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| posted on 10/7/14 at 11:56 AM |
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Are you sure that is right about Q plates. I have no information to suggest it isn't, just that it doesn't make sense.
My car was SVAd with a 1990 Sierra CVH engine and so had to pass emissions based on that engine [3.5% CO / 1200ppm HC].
When went for registration there was a question over whether I got an age related plate or a Q. I ended up with an age related reg. and so have to
pass the above emissions at MOT time.
If they had given me a Q plate would I only have to pass a smoke test?
Stu
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mcerd1
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| posted on 10/7/14 at 12:40 PM |
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quote:
Originally posted by whitestu
If they had given me a Q plate would I only have to pass a smoke test?
That's right 
as I remember they changed the MOT manuals wording a wee while back to simplify/clarify the rules for Q plates
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whitestu
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| posted on 10/7/14 at 01:19 PM |
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quote:
quote:
Originally posted by whitestu
If they had given me a Q plate would I only have to pass a smoke test?
That's right
as I remember they changed the MOT manuals wording a wee while back to simplify/clarify the rules for Q plates
Interesting. Wish I hadn't pushed for an age related plate now! One less thing to worry about at MOT time.
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