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| This is power to the wheels, not engine. This is stage I turbo, stock exhaust, no intercooler, air temp today 86 F, 93% humidity. What the graph shows is, the engine builds power to around 4250 rpm then goes almost flat! At about 3500 rpm, the boost creeps back from 5 lbs to about 4. This shows that the stock exhaust is backing up the turbo at about 3500 rpm which accounts for the sag in the hp and torque graphs at the same time. You can see that it is so out of wind at 4900 rpm and the hp starts to fall off. We stopped the test at 6000 rpm, cause the rev limiter comes in at 6250. The way we test is; start rolling, shift 2, 3, level out at 30 mph. The operator signals me and I flat foot it. The computer takes it from there. Test range is 35 mph to 80 mph, which is 2500 rpm to 6000 rpm in third gear. These engines are real breathers at high rpms, so this all points to a problem on the exhaust side. If a turbo is restricted on the discharge side, its turbine is not able to function, because the pressure is almost equal on both sides of the wheel. I almost locked the waste gate closed and got NO increase in boost. This from a turbo that is capable of over 20 lbs on this engine. Enough said on that! A belt driven supercharger could make more pressure in this exact situation, because it does not rely completly on ex flow to operate. It to might suffer the same fate, but possibly at a slightly higher rpm. If you can't get it out, you can't put more in! Hooking up the Intercooler might not help this situation much. I say much because the cooler, denser charge of air should make better power everywhere, so the power below the 4900 rpm bottle-neck should be better. I spoke with Bill Hahn after the run, he recounted similar results. He said the PT stock produced about 110 hp at the rear wheels. "Un-cork that baby"! For my stage IV asperations, I should be running 3" hi-flow cat, muffler and pipe all the way back. Its just a big air pump. If you restrict it on either end it becomes less efficiant, thus limiting boost and horse power. The car feels great to me, but it does flatten out after 4500. Before the turbo, it was weak before 4000. In truth, the car is better every where now, but the "punch" of the turbo fizzels after 4500. From 2500 to 4500 it is a whole new animal. This is exactly what the dyno graph shows. With the intercooler hooked up and 10 lbs of boost, this setup should make well over 250hp at the wheels. Well I know what to do next! I wanted to see how restrictive the stock setup is, and check out the Dyno Shop. $75 for three pulls, could have done another, but the car wasn't happy, so I'll save it till I open the ex up. Thanks for looking in, .... more to come ! Bob Stockum |
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| Proposed exhaust routing. I'll have prices on all this stuff, including the turbo kit, in a few days. I'm in "the ZONE " right now and not trying to keep track, too closely. I have been buggeting for this for over 6 months, so it's not like I'm going in blind, ... Crazy maybe! You are seeing this project as fast as it is happening .... and that will include any mistakes that may happen along the way. I am not going to "sugar coat" the results or make excuses. This is uncharted water. I am having a blast. Hope you enjoy the ride! I planned to jump in, without a life vest when I started this thing. Lets go make some noise!! |