19 replies to this topic

[cal844]

With my 1993 carb car(still fitted with its factory carb and engine) I removed the cat, doesn't need it!!

[Tags]

Once again the topic of converting back from SPI to Carb resurfaces. I just ask Why would you want to ??
 
As FlyingScot says we have a starting figure of around 63bhp.
Also, although he's not mentioned it here, If my memory is correct, Sprocket has also proved that you can get very close to 100bhp with the stock ECU.
So depending on your budget and commitment in time you can achieve a figure somewhere between these two 
Now lets also figure in the RELIABILITY Factor. If everything is working as it should a fuel injected car, even with the standard SPI Cooper map, has the ability to match fueling to the exact moment. Don't misunderstand me I've nothing but admiration for my Carb bretheren. I'm just not as dedicated, and I never have enough time to do all the other things I want to do on my mini let alone worry about the "Tuning Issue".
 
So it's Fuel Injection everythime for me, and so far this year my driving to tinkering ratio is well over 100:1. Oh and the stock 63bhp should put a    on anyones face. It's certainly enough for me.

The car I bought came with a lot of parts missing i.e. immobilizer, key fobs and i always had the intention of trying to build a more powerful engine.

After ready many different threads it seems just about all of them recommend carbs over injection for making more power. And i don't want to have to worry about/waste money on getting the ECU matched to a new immobilizer. Also all of my previous cars have been fuel injection and i would like something a bit different.

That being said I have been looking at special component & mega squirt ECUs and if i could find one for the right price i might change my mind about the whole thing.

[chaulkup]

I do not blame you for wanting to get rid of the spi and put carbs on.  I had a 95 spi that was completely standard and still failed it's MOT on emissions.  Just go to an MOT tester that will be more lenient.

 

I now have a 93 that started life as an spi but is now a 1380 twin carb with no cat which will fail emissions but will still pass its MOT.

 

Also getting 100bhp out of an spi is very expensive, all tuning parts for spi's are more expensive, from LCB's to cylinder heads and that was one thing that really annoyed me about my spi (apart from being unreliable and harder to diagnose problems)

 

 

 

You will need to swap your fuel tank for one off a carb mini as the spi tank has return pipes and the pump in the fuel tank which doesn't work very well with carbs.  I've just found this out on mine as someone else before me did the conversion so if you're going to go ahead with it you'll need a solid state fuel pump (i've been recommended a facet one) and a carb fuel tank.  

 

Will

[Nu2mini]

OK i know its an emotive subject, but the facts are to my knowledge the last car to be made with Carburetors was the 1996 Lada. Now there's obviously a reason for that.

Injection cars are not hard to diagnose. Like everything else you just need the right kit and practice. How many motor technicans these days know how to setup and balance a twin carb setup ??. They all should know how to diagnose an injection setup.

Now any SPI that is still in good fettle should pass the emissions test. If not then fix it. If it doesn't pass the brake test do you take it somewhere else who'll turn a blind eye to it

I also don't know where this notion of SPI engine components being more expensive comes from. It's the same engine. It's the same head, as standard. What costs is the work that goes into whatever your changing. Uprated CAM, uprated head etc.

Finally as you say there's a whole lot of buggering about to put the thing back to a Carb setup. Fine if someone else has already done the work for you

I'll settle for my SPI
Starts on the button first time every time
Flies through the MOT emissions and all
Idles all day long at 600 RPM
Immediately responds to the throttle
Happily cruises at 70 on the motorway
The fueling never needs tuning

As I say its an emotive subject. We are two halves of the same tribe. Let's just agree to disagree and all enjoy the ride.

[tiger99]

If you get a Megasquirt or similar you can change its settings with your laptop. No need for faffing about with carburettor needles and springs, or involvement with the immobiliser. That also makes it much quicker and easier to tune on a rolling road. Modern engines are utterly fuss-free apart from regular oil and spark plug changes etc, and that is down entirely to getting rid of the carburettor and the mechanical ignition timing and providing closed loop control via the ECU. There is nothing wrong with the A-series block that inherently makes it any less reliable than a modern car. I would therefore strongly suggest keeping with injection and mapped ignition, albeit with up to date equipment.

 

Carburettors never were all that good. The SU was one of the better designs, probably the best (only real comparison was with the vaguely similar Stromberg), because in theory you could have any needle profile and therefore optimised mixture over the full power range, whereas fixed jet carburettors only are optimum at certain fixed points. But no carb ever compensated properly for atmospheric pressure variation, or temperature for that matter. It is a technology that is best only retained where originality matters, if you want reliable, fuss-free performance and economy.