10 replies to this topic

[JSnowDude]

Hi,

Question 1: what is the general consensus on Splitfire plugs, as i've heard mixed things eg. the tips breaking off and blowing the pistons.

Question 2: Can someone explain why you cannot use a sportscoil on a SPi engine.

Question 3: Has anyone fitted one of those upgrade throttle bodies on an SPi? are they a good upgrade?

[Steve@RetroDash]

come on peeps a little helps inorder here.

i don't know the answer to your questions i'm afraid pal.
i had an spi and i didn't realise you couldn't fit a sports coil, who said?
not sure about spitfire plugs and i've not heard of any results about the throttle body, although there was a feature in a mag a while back on an mpi thottle body.

[Dan]

Splitfire plugs are like all other ignition gimmicks, a waste of money.

Certain types of electronic ignition are incompatible with sports coils. Or more accurately sports coils are incompatible with certain electronic ignitions. Sports coils are designed to produce a greater output voltage and allow a greater current flow through the secondary then standard coils when used with a conventional contact breaker ignition. Electronic ignitions however control the current in the primary to a very fine degree and so will produce a greater output voltage for a more controlled length of time than a conventional ignition will with a conventional coil. When used with a sports coil this will produce an enormous increase in the HT voltage which will be outside the insulation range of the leads and plugs. The upshot of this is basically reduced spark output and reduced life of all ignition components (coil, dizzy cap, rotor, leads and plugs). If the ignition system built into the SPi ECU is incompatible with sports coils then there's nothing you can do about it but what it means is that the sports coil is not required. A standard coil will produce a better spark with this system than it would otherwise anyway.

I think the uprated throttle body made by Burlen is only produced for the MPi, the SPi unit is markedly different AFAIK.

[Sprocket]

Keep hearing about these larger throttle bodies for the SPI but have never seen one nor can find any trace on the net. I was told it was a modification to the original, but cant work this out as there aint much metal to machine to start with and even then the injector runs out at around 100bhp. I can only think that you could get a larger throttle body and injector from another car, that is bigger, as most SPI systems appear very similar, maybe a little rework required. Either that or people are getting confused with the MPI throttle bodies.

The SPI use these plugs - NGK BPR6ES, there is no benefit to fitting exotic plugs, they cost more and do the same job. I have heard they actualy cause the engine to run worse in every case, and that is from RR operator at MiniSport. I'm not willing to fork out the extortionate price for these plugs to see if they actualy make any difference, I'lll stick with the standard ones.

Sports coils on the SPI are a no no because as Dan says they produce a higher HT voltage, therefor bigger spark and more current. This however also produces a larger current on the LT circuit that the ECU circuitry has to carry causing over heating and eventualy failure of this out put. This is also true of the electronic distributers. And before any one says that they have one fitted to their electronic distributer and works fine, then all I can say is that its a matter of time before the amplifier gives up. I found out the hard way :nugget: There may well be one available for electronic igition systems now. All I can suggest is RTFM ( Read The F Manual) on the packaging.

[Wil_h]

I don't know anything about SPis but I would assume that they use a coil pack rather than a coil in the traditional sense. So it's not a point of the sports coil having too high an output it is just physically the wrong part.

And yes, stear clear of fancy plug.

Wil

[Sprocket]

I don't know anything about SPis but I would assume that they use a coil pack rather than a coil in the traditional sense. So it's not a point of the sports coil having too high an output it is just physically the wrong part.

And yes, stear clear of fancy plug.

Wil

Yes the SPI uses a traditional style coil, the distributer contains only the rotor arm and cap and the LT is grounded through the ECU to fire the coil. The ECU obviously controling the degree of advance with relation to engine speed and manifold depression much like the Megajolt only difference is the ignition map is designed for a standard car and for economy and also can't be changed which is the only bit that makes it s&!t

The MPI, however, does use the distributorless wasted spark coil pack which does away with the distributor entirely.

[Dan]

I don't know anything about SPis but I would assume that they use a coil pack rather than a coil in the traditional sense. So it's not a point of the sports coil having too high an output it is just physically the wrong part.

Well that's why you shouldn't assume then isn't it!

[Wil_h]

indeed.

[JSnowDude]

I was looking at the mini sport ad in mini mag and according to the ad the throttle body is available for both MPi and SPi and comes in either the standard diameter or a slightly larger version. I'm just trying to get an idea as to whether this is a worthwhile upgrade. I've got the Cooper works kit factory fitted but I have the been bitten by the fettling bug and would like to gain a few more horses and quicker acceleration.

It would seem that you are very restricted as to what you can do with an SPi!

As to the plugs I thought this would be the case and I will be doing as you have all recommended and stick with the "proper" plugs.

Does anyone know what modifications are made to the works head?

[Dan]

Well don't trust Minisport, they very rarely know what they're talking about. The throttle body made by BFS is available in two sizes (48mm standard size or 52mm performance version) but is only compatible with the MPi engine. The SPi throttle body is completely different and is more like a digital carburettor. It houses the injector and several of the system sensors, the MPi part can't be adapted to fit.

The Cooper Works head (never factory fitted incidentally, fitted by John Cooper Garages in Worthing who are not affiliated with Rover) has larger valves and some porting and gas flowing done. It's got nothing exotic like slim stem valves or sleeved push rod tubes or any race bred parts like that. It's just a well uprated iron head.

[boXXer]

As said at work mate, ditch the plugs, as in the ford world, i have heard of soo many tips breaking off the ends of these "fancy plugs". Especially with turbo cars. :cheese: