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.
Quote:
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.
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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.