Quote:
Originally Posted by sqidd
That's a whole lotta beans out of a itty bitty 4cyl!  |
Thanks Man!!!
A few items that I'm very happy with as far as the compound system goes.
#1 The low end torque of my small 13g with out the heat and peak flow numbers suffering. My little 13g turbo by itself would max out around about 26lbs/min. I did some testing with just the 13g turbo and the engine would hit a wall at 24lbs/min and not pull at all. Plus the IAT numbers would increase at a unreal amount and light up the knock sensor. Now I have all the low end torque the 13g provides without any upper air flow limitations up to 65 lbs/min.
#2 Running just the large FP Red turbo my engine had some turbo lag. It would take around 5500 rpm to reach max boost. This made the engine very peaky. Now the FP Red large turbo thinks its hooked to a 310CI engine instead of a 122CI engine at 4000 rpm as a example. So it comes on-line very fast.
#3 Decrease Back Pressure. This is one thing I didn't believe until I seen it with my own eyes. My back pressure is very low for the air flow its running compared to a single match turbo of the same flow. The reason behind this is that the large FP Red turbo is now running at a much lower pressure ratio then if it was a single. I'm running at or under a 2:1 PR with the compound system. Running it as a single I was running it at a 2.5 to 3.0 PR. When you run a high pressure ratio you have to run a higher wheel speed. To run a high wheel speed you have to have a higher drive pressure or exhaust pressure.
#4 This is about the FE side of things that the compound systems is helping with. At 5 to 10 psi around 25 to 35% throttle I'm running at 14.7 to 20:1 A/F.
This has helped when the car is at a dead stop and has to accelerate up to speed. In making this car a dual purpose car. I had to make some sacrifice when it came to engine compression. I wanted a car that could run on pump fuel without any race fuel, and still run in the mid 10's. So to do this I drop the compression down to 7.7:1. I also knew that I could get some of efficiency back at mid to light load with added back pressure when the small turbo is on its own. Plus my goal was to make up for what I lost in static compression and get it back in effective boost compression. Well so far it looks like its working. I need to do a video of this when I'm going from stop light to stop light. The engine sounds like a diesel with the turbos singing.lol I even had a guy in a diesel ask me if I was running a diesel and what turbo I was running because of how loud it was.
Sorry for the long post.
