SC vs Turbo - long and nerdy
Christo:
I'm willing to attempt to sharpen that stick a bit, cuz turbo guys tend to be intrigued by superchargers, and I suspect vice versa.
If you take to the idea that power is mostly a function of boost (I can present that argument easily in my theatre of operation), the 5-6psi is 5-6psi, super or turbo. For more on turbo/supercharger theory Corky Bell's Maximum Boost is a good start, and Humphries Automotive Supercharging & Turbocharger Manual can get you into the real nerdy stuff. Further, to compare the two as apples to apples, you only need 4 data points (along with ambient temp and pressure): Turbo/supercharger compressor outlet temps and turbo/super inlet temps (simply - pre and post intercooler) and Turbo/Supercharger compressor Pressure pre and post IC. The rest is just math. Dual temp (and differential temp) guages can be had from Andial (made by Davtron)
I'd offer that a really bad place to install a supercharger is directly above the exhaust manifold, but shielding and/or ducting air could help immensely there. Let's also not forget that turbos also can heat soak over time as well.
You have a constant pressure in both systems, so the only variable you could have is temp. It's easy to argue that a monster turbo with 5-6psi, will most likely have a lower compressor outlet temp compared to a SC. This means that more dense air is entering the combustion chamber (lbs of air and lbs of fuel). However, big turbos pushing 5-6psi aren't very efficient either. Without those temps and pressures, 'addressing' the problem won't be systematic. And your dyno numbers are a bit misleading. IF it's only heat between the two systems, then address the heat, it's the cheapest thing you can do to either system.
Air to water IC or air to air IC's can dramatically affect the Tim (Temp inlet to manifold ), as can well placed ducting, as can reducing engine temps (by oil cooling for instance). Underhood temps are generated from either turbine, and can be addressed with coatings/ducting/shielding and hi/lo pressure zone airflow control
There is also the question of tuning on a ecu that wasn't designed for boost parameters. IIRC the SMT6 doesn't offer any knock control, which would concern me greatly. There are very few affordable systems that do, but I'd argue for that in a big way. IME, the 034 EFI system would probably be well matched for the I6, although they too, don't offer knock control... Yet.
Christo, I believe your conclusions are premature. Enough development work on a SC, should yeild the same power as the turbo in the low pressure type systems. Get above 13-14psi, IME the advantage goes to the turbo systems, btdt. 10psi or below, I say enough stick sharpening should get the apples and apples to taste sweeter with the SC. Get rid of the 'flapper' MAF (one of my first goals), the SC should do really well.
Then again, if you have any take off SC's for my FZJ80, I'd be most happy to share any pencil sharpening I get done.
I've spent the last 15 years with turbochargers in audis, and understand the application and theory in regards to them. If I was making a track FZJ80, I'd go turbo, if I was looking for big HP gains and hi end HP... turbo. I have a really tweeked quattro for that. I'm looking for low and mid range performance to rival the X5 boys, and bit extra grunt for my tandem axle trailer. At 5-6psi, I'm thinking it's premature to call the SC anything less than what a turbo can do. IMO/E, there isn't much turbocharger theory or practice to support a 'win' for the turbocharger.
Toyota made a good start with these bolt on SC kits. Improving on their application shouldn't be too difficult.
There I go, still no chicken and I'm already sharpening prodding sticks
Scott Justusson
QSHIPQ Performance Tuning
Chicago IL
'94 FZJ80
sleeoffroad said:
The trubo trucks do not suffer from this, but as Dan says, the SC is better than a poke with a sharp stick. However maybe someone has to sharpen that stick a little.
