MoTeC Global Forum

Hello can anyone give some tuning tips for low engine speed also cold start. I have a sequential injected Holden 5ltr with the Morrison motorsport 8 throttle body X over manifold. 1-I'm have some issues getting a consistent idle(looking for around 1200 to 1400 RPM Street driven). I use the Q key with the Lamda sensor but it just seems to run rich as with this function. or it pops back through the trumpets if you try to lean it out.
2- Cold start is a problem when trying to fire the engine up, once going its great but it takes a lot of cranking before it actually fires but wont idle until around 50 degress.
Engine is a solid roller motor. manual gearbox with 3.25 gears. TP sensor no Map sensor. VT dizzy for No 1 and a 36 minus 2 crank magnetic sensor trigger whell. Ali heads and dry sumped. any help or ideas would be great thanks in advance

I had to do a double take when I read this. I thought you were describing my engine.
All details you describe here are the same as mine except that I've recently converted my 304 to a 355.
I'm also not using a 36-2 chopper wheel as I haven't been able to get it working properly.
Anyway, your idle problem. Firstly there are some mechanical things that need to be looked at.
It is very important to get all the throttles synced. This makes a big difference. To do this you'll need an airflow meter. You can get one from Steve Newing at Speed Technology.
You need to get the airflow within about 1.5-2 points at idle.
The problem I had with mine was that there were big variations between adjacent cylinders but the 2 cylinders shared a common shaft on the Morrison manifold.
The solution is to cut the shafts and join them with adjustable joiners. Also from Speed Technology. I got the cheaper ones rather than the fancy ones. Once set, you can forget about it.
Obviously you can already adjust the relationship between the front pair and the back pair on each bank.
The other problem in my opinion is the design of the manifold. Its designed for full power rather than good idle. The injector above the butterfly means that the injector isn't squirting on the back of the valve which is generally the preferred method.
Next trick is to get the idle mixtures correct AFTER warming up the engine. You can't do the cold start before getting the warm base map values correct.
I normally wouldn't use quick lamda for this but do it manually. Adjust the mixtures down to be relatively lean. When the motor starts popping back up the trumpets, richen it slightly so it just stops this. I found this is around .92 - .94 lamda.
I run mine as lean as possible at idle as I've had a lot of problems carbon fouling plugs during warm up.
Now that the warm mixtures are hopefully correct, its time to do the cold start mixtures. Obviously the motor needs to be stone cold to do a proper test which makes it very time consuming.
Here are the settings I use. Yours may need to be different based on lots of factors.
First things first. I use the manifold wetting function when stone cold.
Under General Setup - Miscellaneous Setup - Stopped Fuel. Set to 250. First Injection 60.
With this function, its like an old carby setup. With the engine stopped for first cold start, I pump the throttle twice (to the floor) This gives a couple of squirts of fuel to wet the manifold etc. This makes all the difference between instant start or cranking for a while and eventual start. Mine starts almost instantly.

Cold Start Parameters are as follows:
Cold Warm up Enrich -1
Post Start Enrich 120
Cranking Enrich 500
Post Start Decay 20
Cold Accel Enrich 20

Warm up Enrichment is by Engine Temp compensation in the fuel table
Values I use are:
Temp 0 20 30 40 50 60
Trim% 35 35 25 12 7 0

All other compensations are as recommended by Motec in the help.

Re the cold start. Its interesting that you say that you have to wind it over for a while before it starts. I had exactly the same problem when I experimented with a 36-2 chopper wheel. I never got it working properly. Would run fine in the shed, but on the track would misfire under load. Tried all sorts of different things. Have given up on it. I'd be interested if yours works, how you set it up. I've gone back to the VT distributor for the ref and sync.

After all this, mine idles smoothly at 1000rpm. Can be turned down with adjustable idle stop to as low as 800 rpm but its not comfortable there. Engine has roller cam. 260 deg at .050". ~ .670 lift. 11:1 comp running BP98 unleaded.

I see your post was from Oct last year so I'd be interested if you got it sorted out. I've had my combo for around 15 years.

Cheers
Paul