but it also looks like you've gained after 4k rpms. the boost kept going up to almost 20psi!!
what was the hp and tq numbers?
Tony sir you are amazing and i was woundering when you would do this
Due to the TRD SC, it is driven off the crank so the amount of airflow provided by the SC is determined by engine RPM. Combined with the turbo, since the 1MZ engine naturally loses its efficiency after 5000RPM or so, this in turn also puts out more exhaust energy per given amount of HP that is created by the engine (BSFC goes up, VE goes down). When exhaust energy is increased, then exhaust pressure against the exhaust valves increases as well, thus, reducing VE and the amount of air that the engine can ingest.
What happens is that boost pressure will automatically creep and keep rising because the TRD SC is trying to maintain a linear airflow curve. The 1MZ engine cannot ingest the air since it loses effiency up top naturally. If you check out the TurboMagazine twincharged MR6 (summary section), this defines their findings describing that the supercharger behaved like a "big cam" at upper RPM's. They didn't really know why it increased power up at high RPM at the time, but this was the reason. Boost kept rising because the TRD SC is trying to maintain a flat torque curve for an engine that has a falling torque curve. Imagine the TRD SC is going to ram in an extra 350 CFM of air into the engine at 6000RPM @ 6 PSI on top of what the turbo is pushing through (ie: 20PSI + 6 PSI); if the engine can't take in all that air, then the residual CFM becomes additional boost. Boost pressure automatically increases as RPM increases and as torque drops.
The goal for this twincharged setup is to prove a few things, mainly myths and misconceptions. The other goal is to achieve excellent throttle response and totally useable power (flat torque curve). I am sure you've heard about people saying that you must bypass the supercharger when twincharging. Or when folks say that the supercharger is restrictive at big power levels and so forth.
First of all, the supercharger cannot be physically restrictive.. It can create boost out of atmospheric air, so it is an air pump. If you feed say 10 PSI and 1000 CFM of air through the supercharger, it just adds another 350 CFM through it. But whenever we think about air pumps running in series, we think about restriction because you can only flow as much as the largest pump in the system. In my case, the largest "pump" in the system is my T51R turbo. So if the turbo can only allow 1000 CFM of total flow, and you are feeding this amount into the SC, it will not produce more than 1000 CFM -- not more that what the turbo can flow for.
The idea is to size a turbo big enough for the power goals, and then have the supercharger "clean up" the rest of the power curve. When I approached this twincharged setup, all the places I have been reading from (Mustang Cobra forums, etc...) and all my local buddies blatantly said that the supercharger hurts and kills top-end power. That's totally wrong... Even before I physically ran the setup, it sounded wrong in theory.
I managed to run my Camry up to 26 PSI with the supercharger and it actually made slightly more power than without it. As a result, I have gained tons of midrange and achieved a much flatter torque curve (flat torque curve = good) and a torque band that goes higher RPM (I will be posting better graphs once I get more data). My old record was 567 WHP @ 26 PSI, but I've easily matched that power at 24 PSI being twincharged. It eventually made 580 @ 26 PSI with one weak piston, showing a definite power gain despite feeding boost through the SC. The T51R turbo I have on my Camry can flow up to 800 HP with a turbine sized nicely even for a bigger motor, so there was no restriction in my setup at all.
The supercharger's job was to do these few things:
- improve low-end power right off idle --> success
- improve full boost spool time for my big turbo --> success (reduced spool time by 1000RPM)
- maintain the same level as single turbo, showing that feeding boost through the TRD SC is not a restriction at all --> success (SC gave more power instead, probably due to a shift in compressor efficiency from the turbo)
- improve boost response within spool range (reduce "boost lag" between shifts or during a roll-on racing situation --> success (the motor literally behaved like a 4.0L motor instead and spooled the turbo like its not even there at higher RPM's)
- improve horsepower curve and extend powerband --> success (my torque now wants to stay much flatter, therefore, maintaining a linear HP curve with the SC)
So really, the twincharged setup is to allow quick useable power right from the get-go, but without tire shredding torque. Totally mimicking what a true useable powerband should be, along with much better throttle response everywhere. My old twin turbo setup was considered a failure because all it did was make shit loads of torque, and it was totally unuseable (unless it was a truck and I want to tow stuff with it). The old TT setup looked great on paper because I managed to get full spool at 3200RPM and over 500+ lbft of torque, yet, the boost took a while to fully come in (lacks throttle response), and there was no resolution in the powerband (either on/off, not manageable and falls off up top).