My set up and advice please...

[BMWTurbo]

Hi Guys,

I had posted in an old thread, but didn't want to drift it too far off topic so I thought I'll post this here.

Originally Posted by Howerton Engineering

One calculation we have used for single stage systems is this: You want to start injecting before the torque peak. So on the dyno plot, find the RPM where the TQ is climbing to peak, and look at the HP at that point. Multiply the HP number by 1.5 to get CC/min of an injection amount.

We usually use crank hp numbers for the calculation.

Now, if the car were at 250hp during the ramp, then the jet would be a 375cc as a starting point. Not far from where you are. You can run your numbers to see what it actually is.

One more item to consider, injecting at the TB puts a lot of large droplets in the chamber which can blow out the spark. One thing I would try is moving the jet further away from the manifold, as close to the exit of the IC as possible.

Great info thanks for that.

It's a sequential twin turbo system, ie, one turbo until 3800RPM and then both turbo's after this. By about 4200RPM I have full boost on both turbo's and roughly peak torque @4500RPM odd(from memory). Power would be a modest 400 engine around this area.

I gapped the plugs down to 0.65mm last night and found I still had a bit of blow out again this morning. I can easily enough move the nozzle into the I/C piping for a trial, but it will be in a vertical section of pipe about 2 pipe dia from a 90 degree bend. I was wondering if possibly the nozzle location wasn't the best as the spark blows around 4500 and it clears up 5500rpm odd on the 400cc/min nozzle.


Here is a 1/8 BSP fitting that I have used for testing I can easily relocate the nozzle to.

The engine bay, pipe in the photo above is vertical into the large rubber bend heading into the throttle body.

Currently mounted like this in the lower part of the TB.

I'd like to run the 0.7mm gap on the plugs again if not a fraction more as the engine is more responsive with this gap, but I want the spark to stop blowing out.

My trigger ponit for the solenoid is when the 2nd turbo is told to come on-line, so it's injecting as #2 comes on-line and stops at 2psi manifold pressure, ie when I back off.

I'd move the jet first. It sounds like you are getting a lot of large droplets in the cylinders and blowing out the spark. More time in the pipe will give the droplets more time to evaporate and shrink in size, as well as get more evenly into all cylinders.

[BMWTurbo]

Originally Posted by Howerton Engineering

I'd move the jet first. It sounds like you are getting a lot of large droplets in the cylinders and blowing out the spark. More time in the pipe will give the droplets more time to evaporate and shrink in size, as well as get more evenly into all cylinders.

Thanks once again Howerton Engineering. I will relocate the nozzle and see how it goes.

I did some crude testing of the pattern before I fitted it. I think that's the 300cc/min nozzle not 400cc/min though. and I tried to create some airflow through the TB with a vacuum in resverse. Very rudimentry, but shows it isn't terrible atomisation.



Last weekend I set my spare nozzle up to spray directly onto my intercooelr core as I was concerned with heat soak. The core is only 400wx300hx100th bar and plate so is probably undersized for the power I'm making. It is compromise though as the nozzle is only 120mm odd in front of the core firing down and across it.

[BMWTurbo]

Well moving the nozzle another 400mm + down the intercooler piping from the throttlebody made little difference. The engine still seems to be blowing the spark when #2 turbo comes on-line.

I'm thinking ideally I need to stage this to come on once the second turbo has spooled rather then as soon as the exhaust valve is opened on the second turbo, or I need to drop back to the 300cc/min nozzle, or, pull the plug gap back.

I will double check with the W/I turned off to ensure that it's not something unrelated, but I'm pretty certain it's the WI.

One thing that probably doesn't help is that the mixtures go really rich at the changeover point when the second turbo is spooling, so this probably exaserbates the problem.

Making it come on a little later when the second turbo is spooling and there is more, and hotter airflow, might help.

[BMWTurbo]

Originally Posted by Howerton Engineering

Making it come on a little later when the second turbo is spooling and there is more, and hotter airflow, might help.

I don't have any spare output channels unfortunately, hence why it's piggybacked on to the control circuit for the second turbo.

I might change over to the 300cc/min injector, or I could add some more meth to the mixture :P

I'm using it for knock supression more then anything else and the highest knock instances I see are when #2 makes full boost, so I'm not sure I wan't to bring it on that much later anwyays.

[BMWTurbo]

So further to this the engine does the same without the W/I turned on. I hadn't noticed it with the W/I turned off the other day, but further testing shows it does. So it's not W/I related.

I've regapped down to 0.6mm (24 thou) and it's basically gone now even with W/I on (made no clear difference). I'll probably look at moving the nozzle back up to the TB because it's a 'nicer' place for it to be physically and doesn't appear to have been the problem.

I think it's purely down to cylinders pressures. When the second turbo comes on the boost ramps up very hard and peaks at 25.5psi, whereas later in the RPM range is settle back down to 23/24psi which is where my boost solenoid control points are.

This explains why I could replicate it by backing off and hitting it again in 2nd gear as the boost ramps up harder (and peaks higher) with WOT in 2nd from cruise than it does in 1st gear WOT.

[BMWTurbo]

Nozzle back up in throttlebody and no discernable miss again.