14 replies to this topic

[extreammini]

Hi,

I have a MPi with the standard injection system! The engine can and will take more power so ultimately more fuel is needed!

My question to you Mini guru's is is there another form of injection that I can put in in place of the standard MPi injection system? Also I don't really want to put a carb on it!

I want a kind of fast road or race competition injection system for it ..... BUT no carb fed (If possible)

Thanks for reading, I can't wait to hear what you guys come back with!

Many thanks and regards, Mark

[Ethel]

You're going to need injection to pass emissions tests. The Rover system (Mems) is pretty sophisticated and should be up to more than can be achieved with bolt on tuning mods.

Canems do the closest to an out of the box injection ecu as far as I know, there's also Megasquirt. The siamese inlet port is the issue with Minis, hence the interest in 7 port heads from serious tuners.

[DeadBert]

Specialist components do a replacement system.

http://www.twinkam.c...aid=SC220B.001

Not sure what I make of it as I haven't seen any results with tuned engines yet.

Chris

[R1minimagic]

MPi system should be ok up to 100bhp

[Sprocket]

Specialist components do a replacement system.

http://www.twinkam.c...3DSC220B.001%26

Not sure what I make of it as I haven't seen any results with tuned engines yet.

Chris

Add £200 to any of the cost of any aftermarket programable ECU for a wideband lambda controller. Without it any car post 1st August 1997 will fail the emissions without a doubt. Looking at the costs of the Specialist Components kit, nice as it is, can you justify the benefit for the price?

[DeadBert]

Specialist components do a replacement system.

http://www.twinkam.c...3DSC220B.001%26

Not sure what I make of it as I haven't seen any results with tuned engines yet.

Chris

Add £200 to any of the cost of any aftermarket programable ECU for a wideband lambda controller. Without it any car post 1st August 1997 will fail the emissions without a doubt. Looking at the costs of the Specialist Components kit, nice as it is, can you justify the benefit for the price?

Justifying the price is relative to the individual. For some the appeal of an advertised plug and play kit would be worth the extra cost.

Spoke to John from SC at Mini Fair in January and he was adamant that there would be no emission issues as I had the same concerns. He made no mention of a wideband lambda at all although at the same time didn't say one would NOT be needed. Make of that what you will.

Chris

[extreammini]

Hi,

Well I have a 1380 MPi and I'm running at around 84Bhp at the flywheel!

How can I get more with out changing the injection setup?

The engine is very tuned and can tell you exactly what its had done! I'll dig it out but its got 1.5 roller rockers, lightened and balanced crank and stage 4 head!

Fire away any questions and I'll be happy to return an answer!

I just thought that having a new injection system fitted would give me more power .... maybe lighten crank and omega pistons??

Any thoughts would be greatly appreciated!

Many thanks Mark

[Ethel]

With any engine, but especially one that has to pass strict emissions, you have to get it to consume more air - the fuel is added in the right proportion regardless.

[cian]

Go for the SC i made the leap and what a difference!!! I was running the standard rover set up with my 1275 stage 3 tuned head cam etc etc, and the difference in power and torque was incredable! The standard injection system was holding back my set up big time! Extreamini i would say if you went for a SC kit or similar you would be unlocking some major ponies from your engine!

[bluedragon]

80-85 bhp is about the limit for the MPi injection system. With the shared intake ports, only so much fuel can be injected in the limited time interval available to fuel one cylinder properly. Beyond that time interval, then the other cylinder/port starts getting the fuel intended for the original cylinder, defeating the purpose of fuel injection.

To make an engine deliver more HP without increasing engine displacement or adding forced induction, the engine has to be revved higher. But higher revs reduce the amount of time available to inject fuel for each port, further capping the max power possible.

A huge injector to squirt enough fuel for the short time intervals at high RPM can be inefficient and unable to accurately meter fuel under low demand conditions, and it's hard to pulse the injector anyway at high RPM's even if the capacity was there. This was certainly true at the time the MPi system was designed, though perhaps modern injection technology has changed this. I am unaware of this however - most of the custom 5 port solutions use staged injection (4 injectors, one set smallrt to handle low fuel demands and the other to kick in when demand increases.)

However, the upgrade kits can fatten the powerband. If the peak can't be increased beyond a set limit, at least the peak can be fuelled lower in the RPM range, if there's enough air coming it. This is the rationale behind the Stage 1, etc. kits. Most people don't rev their cars to redline anyway to take advantage of increased power, the engine feels more powerful if it can deliver more power than normal in the usual driving ranges between 2500-4500 RPM. This is very evident with the tall 2.76 MPI final drive.

It was the superior torque and mid-range output of the MPi system that made the 2.76 FD possible. Carbed cars might have more peak output but they might struggle in many cases to pull the 2.76 gear under 5000 rpm.

So a peak of 85bhp on a normally aspirated MPi motor is right in line. It could still feel very strong though, and be very useful, because of the broad, healthy torque and power curves possible via MPi. There are very few, if any, documented instances of the so-called "90hp" kits actually producing anything close to that in real life.

[extreammini]

BlueDragon,

With the shared intake ports, only so much fuel can be injected in the limited time interval available to fuel one cylinder properly.

I have a stage 5 head which is fully worked but unsure how many ports it has (I think it has 7?) I am also unsure how big / small the valves are!

Most of the custom 5 port solutions use staged injection (4 injectors, one set smaller to handle low fuel demands and the other to kick in when demand increases.)

Would you recommend I try and adopt the above set-up? Also excuse my ignorance but if you 4 cylinders you have 4 injectors!? Does the above system mean you will have 4 idle / low power injectors and 4 medium / high idle injectors? Or does 5 prt mean you have 5 ports where fuel is received from 4 injectors and therefore 2 injectors are for idle / low power and the other 2 injectors are for the medium / high idle?

Forgive my ignorance (again) but what do you mean by ports? Are you talking about inlet ports?

So a peak of 85bhp on a normally aspirated MPi motor is right in line. It could still feel very strong though, and be very useful, because of the broad, healthy torque and power curves possible via MPi.

Mine has a 3.105 final drive on it and as you said its a cracking motor! As you said It pulls very well and has a very strong, healthy torque range. It never seems to be out of power, it is very good and I'm very impressed!

But as a fat kid in a cup cake store, I want more! I want faster acceleration with a higher top speed .... This is basically because I'm a child at mine and just want more more more! Haha!

Thank you BlueDragon, I look forward to your response!

Cian,

Go for the SC i made the leap and what a difference!!! I was running the standard rover set up with my 1275 stage 3 tuned head cam etc etc, and the difference in power and torque was incredable! The standard injection system was holding back my set up big time! Extreamini i would say if you went for a SC kit or similar you would be unlocking some major ponies from your engine!

Thank you for your advice! I rang John at SC and he spoke to me in great detail about the set-up and he was very helpful. He told me I could expect around 100hp from my engine with his kit!

I think I will start saving the pennies, have the injection upgraded first and then might just be really greedy and put a Turbo on the old girl! Haha!

Thanks for everyone who has posted, your help is really appreciate it and has developed my knowledge on the A-Series engine vastly!

Many thanks again, Mark

Edited by extreammini, 04 April 2012 - 12:12 PM.

[Sprocket]

Lets not get confused here about the methods of fuel injection. For the ease of simplicity, all injection systems function in a similar manor. Where the Mini's funky 5 port head is concerned, it matters where and when the fuel is injected.

The SPi or TBi, throttle body injection as it is sometimes known, injects fuel before the throttle much in the same was as an SU carb jet and needle supply fuel before the throttle. It dosn't matter too much when the fuel is injected, and functions in a similar manor to the carb, within reason.

The MPi is also known as a port injection system, is multi point since there is more than one injector, where fuel is injected directly into the ports of the cylinder head, right at the back of the inlet valves. There lies the problem of getting the right amount of fuel into each cylinder. Four cylinders, two inlet ports, means two cylinders share each inlet port. Without getting into the technicallities of it all, the system is somewhat restricted in what you can achieve because of available valve open time, without resorting to a complex programable ECU and larger or staged injectors as already discussed above. The racier the cam the bigger the problem.

The specialist components 'MPi' system should be considered a TBi system since it injects fuel at the throttle body similar (but not the same) to the Rover SPi system, and not directly into the inlet ports of the cylinder head like the Rover MPi system. This removes somewhat, the complications inherant when injecting direct into the inlet ports, and is one reason you can get more from your engine. This system can still generally be called a multi point injection system since it uses more than one injector, but it is most definately not a port injection system that the Rover MPi systm is.

I take back my previous comments about the SC system and emissions, since I am sure they still use the narrow band lambda sensor to provide closed loop control. This system should still pass the emissions test, and the benefits of being able to tune the ignition curve fueling to suit the engine and releasing that extra HP the standard ECU was holding back on. Obviously the racier the cam, the more dificult you find achieving the emissions limits imposed on the MPi engines. You need the catalytic converted installed in any case.

Do not confuse the SC MPi system with the Rover MEMS MPi system. The operate in two different ways

[nz_seamless]

Question for people who have actually pulled an MPI system to bits. Where are the injectors? What sprocket describes is "proper" port injection which I didn't think existed for the mini. My understanding was the injectors aren't mounted in the head, they are still only in the inlet manifold, and therefore the 2/3 robbing issue is still just as much an issue. Is that not the case, are there mini heads that actually squirt down on the inlet valve?

Edited by nz_seamless, 18 July 2014 - 11:58 PM.

[KernowCooper]

All inlet mounted the casting on the A series head could not be modified on the MPI, not cost effective so late in the minis final few years, not it could be done on the original head.

Edited by KernowCooper, 18 July 2014 - 11:57 PM.

[nz_seamless]

Cool, that's what I thought, closer to the head face than SPI, but still a wet inlet. Thanks