On another thread regarding a TT install, our friend Eric (AtomicGT) said,
That got me thinking of a way to try to compare and discuss the differences of the SC set-up to a TT set-up. The root of the question assumes that RWHP is an indication of how much overall "work" the engine is actually performing. Conceptually, it would seem that an engine with 600 RWHP has a lot less strain on it compared to an engine with 800 RWHP. This is really NOT the case if the method of forced induction is not the same.
I looked through some files I had here on the laptop and tried to find some dyno charts that would illustrate this point. In particular, I tried to find an SC chart and a TT chart where the boost pressures were as similar as possiple. I *almost* succeeded in the following:
It would have been great if the boost pressures were identical, but with max difference of about 1PSI, I think we can consider them close enough to illustrate some of our points. (I left the TQ curve off just to simplify the graphs.) The first thing to notice is that the SC is really superior to bring on boost much earlier than the TT is capable of. The HP graph shows this well with the SC "ruling the roost" below 4,000 RPM. At approx 4200 RPM the TT has finally matched the boost levels of the SC and sure enough, this is where the HP ouput is also the same.
But the real differences between the SC and the TT can be seen in what happens North of 4200 RPM. If you look at the the boost graph, the boost levels are approximately the same and flat from 4200 RPM up. To maintain constant boost pressures, the TT set-up is bleeding off EXHAUST (not boost) pressure via the wastegates. The Supercharger starts falling out of an efficiency curve and the engine is expending a lot of power to turn the supercharger - power that is not being measured by the dyno at the rear wheels. And the net result... more than 200 RWHP provided to the rear wheels via the TT.
Let's get back to AtomicGT's original question. So, in this simple (admittedly inexact) example, which engine is working harder and could ultimately incur a shorter lifespan. In my view, the two engines in this example are doing approximately the same work. The TT is doing a better job of getting more power to the ground at the top end, while the SC has a clear advantage at the low end.... but is exerting a tax at the upper RPM range.
Congratulations, Impressive. Any estimate on the engine life with that kind of BHP?
That got me thinking of a way to try to compare and discuss the differences of the SC set-up to a TT set-up. The root of the question assumes that RWHP is an indication of how much overall "work" the engine is actually performing. Conceptually, it would seem that an engine with 600 RWHP has a lot less strain on it compared to an engine with 800 RWHP. This is really NOT the case if the method of forced induction is not the same.
I looked through some files I had here on the laptop and tried to find some dyno charts that would illustrate this point. In particular, I tried to find an SC chart and a TT chart where the boost pressures were as similar as possiple. I *almost* succeeded in the following:
It would have been great if the boost pressures were identical, but with max difference of about 1PSI, I think we can consider them close enough to illustrate some of our points. (I left the TQ curve off just to simplify the graphs.) The first thing to notice is that the SC is really superior to bring on boost much earlier than the TT is capable of. The HP graph shows this well with the SC "ruling the roost" below 4,000 RPM. At approx 4200 RPM the TT has finally matched the boost levels of the SC and sure enough, this is where the HP ouput is also the same.
But the real differences between the SC and the TT can be seen in what happens North of 4200 RPM. If you look at the the boost graph, the boost levels are approximately the same and flat from 4200 RPM up. To maintain constant boost pressures, the TT set-up is bleeding off EXHAUST (not boost) pressure via the wastegates. The Supercharger starts falling out of an efficiency curve and the engine is expending a lot of power to turn the supercharger - power that is not being measured by the dyno at the rear wheels. And the net result... more than 200 RWHP provided to the rear wheels via the TT.
Let's get back to AtomicGT's original question. So, in this simple (admittedly inexact) example, which engine is working harder and could ultimately incur a shorter lifespan. In my view, the two engines in this example are doing approximately the same work. The TT is doing a better job of getting more power to the ground at the top end, while the SC has a clear advantage at the low end.... but is exerting a tax at the upper RPM range.
Last edited: