10 replies to this topic

[TrialsLife]

Right, I know that the cooper Spi is good for 90bhp.

Now to get past that what would hold the engine back the most, the Injector itself or the ecu.

I know you can get better injectors, throttle bodies. Or a better ECU.

What options would there be with the ECU?

[Big_Adam]

well if you decide to get the ecu done chipped or new eprom then that should give a bit more power.

don't know what would be best.......hmm....on second thoughts i should have just stayed quiet.

[1984mini25]

what would hold the engine back the most, the Injector itself or the ecu.

Both

You can get the ecu chipped or re-mapped but there is a limit to how much the injectors can give before they need upgrading.

*Think I’m right till some one else points out otherwise*

[pikey7]

Paging MiniSprocket!

IMHO, its the ECU. Usually these things are tuned for emissions and engine life, so it needs reprogramming to be able to give more ponies. However, once you do that, then you'll run past the effective duty cycle of the injector.

However, you'll need to know what to program the ECU to. It's not as simple as just giving it more fuel to get more HP. hell, just dumping a ton more fuel in will make it run worse!. A slight tweak will probably give you a couple more, but you need to be looking at more ccs, better breathing and cams before you can effectively use any more fuel that the reprogramming can give you.

As for how to tweak the ECU, no idea! I've heard there is some interceptor unit (But I can't recall the name), but that just sounds a bit hit or miss to me!

[Sprocket]

Injector

The standard ECU is a very clever piece of kit, more than most will give it credit.

Granted the ECU is a limiting factor, but its only like tuning a carb engine and still using the standard dizy. The injector is stretched to 85% duty cycle at around 87bhp so a bigger injector is required. Go too big with the injector though, and the idle suffers dramaticaly, may not even pass emissions depending on engine spec.

The interupter type of programaple ECU's are IMO a half way house and at 300 notes you could buy the latest Megasquirt II hardware version 3. Dont know of any one who has yet set up the SPi to run with MegaSquirt, the way it should, though i'm sure it has been done.

Throttle bodies can only be increased to 44mm from 36mm but is not the simplest of tasks to get the new disc to seal and alow correct idle control. Wood and Picket sell them ready to fit for about 300 as well. To be very honest, its not worth it except for a highly tuned engine consuming a considerable amount more air.

Twin point is a whole other ball game

[pikey7]

MS, does that mean no-one really offers a remap service on the standard ECU? It's either interceptor or dump it for a megasquirt or similar?

[Sprocket]

Yup

Good old Rover does it again

[pikey7]

Lol! Gotta love them!

I know with the Porsche (well, early ones anyway), there are a few places that make adapters for fitting chips that can be reprogrammed, of course though you need to understand the code in the chip first! I'm amazed no-one does similar for these cars! Well actually, its Rover, so no I'm not"

[Bill USN-1]

A quick fix for a minor lean condition is to adjust the fuel pressure regulator up a few pounds.
I play with FI systems but haven't played with the Mini.(yet)
My plan is to use the GM TBI system on the MINI. It is well hacked and completely programmable (now). Like the Megasquirt.
I have not built one yet so this may be a chance to try the MS with spark control.

By increasing the pressure, the injector will spray a larger volume of fuel for the same pulse width. Effectively giving you a bigger injector.
This will only work for correcting a small ammount of lean conditions in the upper rpm.

The FI system should be a closed loop system that uses an O2 sensor to provide feedback to the ECM. This maintains the 14.7:1 AFR(stoick).

So as long as you don't go outside the ECM's capability to adjust the AFR, it will continue to correct for the increase in fuel.

Since at what-wide open throttle the motor need to operate at about 12.5:1 AFR the O2 is no longer used and the ECM goes into open loop.
The fuel is based strickly on the tables in the ECM.

So a what on a rolling road(as you say) Dyno run...will tell you if you need to adjust the fuel pressure up or down to achieve the 12.5AFR at what.

Another way is to use a Wide Band O2 sensor. These have a wider operating range than the stock narrow band sensors.
I currently use the innovate LM-1 set up. Saves on Dyno run time!!

This can be a very in depth subject so this is only meant to be a very brief overview.

HTH

[Sprocket]

By increasing the pressure, the injector will spray a larger volume of fuel for the same pulse width. Effectively giving you a bigger injector.
This will only work for correcting a small ammount of lean conditions in the upper rpm.

This method works, but is not ideal and again the idle can suffer.

Personaly I would rather stick with standard pressures as most things in life are not linear and it is my opinion that this would affect other areas of the fueling at other RPM.

I say this in respect to using the standard ECU. At least till I get my MSII sorted. Bigger injectors are easy to get hold of anyway.

[TrialsLife]

Cheers for the advice so far. I'm sticking with the injector. Going to get some engine work done soon.

Instead of opening up another topic.....

Looking through mini speeds website I found this Injection manifold
its says its for the cat when its removed so I'm guessing I'll need this Clicky

Am I right?

Cheers.