Hi guys,
I wanted to tell you about my "7 port head" setup experience on my 1380cc unit.
I've just finished setting up the following setup:
- MED 7 port head "Trackday" version
- twin Jenvey DCOE Throttle body 30mm long / 40mm diameter
- 4 x 250cc/mn IWP042 pico injectors
- Calver RE13OT camshaft reprofiled on genuine MPI camshaft (in order to use a camshaft sensor for sequential injection)
First of all 2 big warnings:
- MED 7 port head and Jenvey throttle bodies do not share the same threads, one is metric, the other is imperial, which means it's not a direct fit
- 30mm long throttle bodies are too short: the cable linkage does not have enough space and gets into the air filter base plate, so we had to add some alloy sleeves to give enough clearance
So the way to go would be to choose the (slightly more expensive) solution that MED sells along with it's 7 port head...
The ECU setup is now 90% completed.
The injection setup was quite simple: my car was already running on an Emerald ECU, and I've developed a nice excel macro that takes the log files from the Emerald ECU and outputs a corrected fuel map. After about 4 or 5 iterations, the fuel map is totally stabilized, but is still in a "batch mode". I still have to adjust it for sequential injection.
The ignition map I was starting from was way too retarded, because my previous setup had a somewhat aggressive compression ratio (about 11.2:1) along with a very mild cam (SW5) which (I figured out only later) is not the right way to go. I now run a much more reasonable compression (10:1) and the more aggressive cam profile means that the dynamic compression you get is even lower compared to the previous setup (some of the compression is "lost" since the inlet/exhaust valves openings overlap). I used a map found on this very forum from a megajolt setup for a Kent 276, and it seems to work very well, without any detonation. I still need to put the car on a rolling road to fine tune the ignition though.
Now what is the result ?
First of all, setting up an injected 7 port head is a real joy. The very short distance between the injector and the inlet valve, and the fact that you have a 1 to 1 relation, means that all the issues related to "the fuel not arriving properly to the engine" disappear. Engine start-up for example is very fast (and clean) since you don't need to inject an enormous amount of fuel to "wet" the inlet port before your cylinder gets some of it. The same applies when you floor the accelerator. In my previous setup I add to apply and enormous "acceleration fuel correction" to compensate for the fact that the engine would become very lean while accelerating, but then this compensation would translate, after about 1 second, in a very rich mixture during 2 or 3 seconds... So basically with a 5 port head it's almost impossible to properly stabilize your AFR ratio to the desired value, whereas it's quite straightforward with a 7 port head.
The result is an engine that is very nice to drive. The power gain is yet to be properly measured on a rolling road, but the difference in feeling and amount of air/fuel that the engine can burn (from +15% to +20% between 5000 to 6500 RPM) suggest an increase from 95hp to about 110-115hp. The car becomes alive above 3000 RPM, which corresponds to the point where it starts to drink more fuel that my previous 5 port/SW5 setup, with a real kick above 4250RPM. Between 2000-3000 RPM you can drive as a gentleman but will not spin your wheels. I expect the sequential injection setup to add some (little) torque in this zone, by enabling a slightly better air/fuel mixture.
On the down side (apart from the price tag of course...), with a 7 port head the engine becomes very loud. So your Mini becomes a "head turner", which is nice since then people can have a look at it, but If I don't receive very soon all the noise absorbing materials I ordered on Ebay, I will probably turn deaf before next year... I was not expecting it but, if you think about it, since you can almost see the cylinders through the throttle bodies, it also means there is very little preventing the noise to flood your engine bay...
Another thing that is annoying me is the fact that I have "too much air" getting into the engine at idle... With the throttle bodies "fully closed", I need to retard my ignition to about -5º to get my engine to idle at about 1050RPM which is still too high. If I set the ignition to a more reasonable -20º, idle sets at 1600 RPM... I've checked for leakage and the problem really seems to come from the throttle bodies being poorly "air tight", and with 4 throttle bodies only a small leak can give enough air for a fast idle... I will have to find some way to increase the TB air tightness...
As soon as I have more data on this topic (rolling road figures...) I will let you know!
Cheers
Diogo
Edited by diogoteix, 16 December 2013 - 05:53 PM.
