EricVonHa
Well-known member
First lets understand how the turbo and wastegate controls boost. When exhaust gas flows out of the engine, it goes through the turbo blades which spins the turbo. As the turbo spins the boost goes up and forces more air into the engine. More air into the engine means more exhaust gases, which come out into the turbo to make it spin faster again. See a problem here? In a few secs you would have infinite boost. This is where the wastegate comes it. It sits in parallel to the turbo in the exhaust path. So when exhaust comes out of the engine, it can either go through the turbo, or be bypassed through the wastegate. During light throttle and low boost the wastegate stays closed. This causes all air through the turbo so you get the best spool up time and response. As soon as the wastegate sees full boost-- It opens up to let some air bypass the turbo to maintain the set boost, and (in theory) not going over.
The biggest problem with modifying almost any parts of a turbo car with a stock wastegate and control is boost creep. (Different then a boost "spike") Creeping is when the boost goes higher then what it is set at while on the throttle. The higher the gear, the more it will creep as there is more load on the engine, so 5th gear is worse, 4th is bad, 3rd might creep a little..Even though the boost is being raised which you might want to do, Creep is not a good thing-- the safety systems that have been put in place in any "stock" fuel injected car can only work within certain pre-defined parameters. This is especially true on Callaways. Have you considered changing Micro-Fueler settings or have metered your A/F ratio or have even adjusted fuel pressure in response to --> Changing exhaust is easy.. dumping the cats is easy.. how it effects other components within the system is the real test. Recently, a turbocat guy came in here and boasted of mods-- looking for solutions and didn't listen carefully. Maybe this full page response will offer some clarity to the issue. THE CORRECT WAY TO RAISE BOOST AND EFFECTIVELY CONTROL BOOST ON ANY MODIFIED CAR IS WITH A BOOST CONTROLLLER! The problem(s) here with the Callaways is the hole in the wastegate isn't that big. Plus:
1) There is no user adjustable electro-mechanical boost controller on a Callaway. The wastegate is purely mechanical and was engineered to operate within CALLAWAY'S ORIGINAL DESIGN PARAMETERS. No crap if you modifiy everything else that your motor will suffer the effects of boost "Creep"
2) Modifying the wastegate is big $$$. Consider the fact that even finding a turbo housing is next to impossible for these cars.
3) What is your ECM fuel table, spark timing and injector pulse width doing from just changing exhaust..? Dunno for sure but guaranteed that it varies enough from car to car that a $300 dyno session is a walk in the park compared to spending close to $20k on an engine re-build. If your car is building more boost than the factory tuned it for initially.. it's time for a modified ECM program or at a minimum a tweak on the Micro-Fueler. Again, a $300 dyno session with A/F feedback is a necessity. It takes less than a nano-second to burn a hole at the outer edge of a piston and burn a ring land at the same time. Pooof!
Adding an aftermarket exhaust, dumping the cats, putting in a Wonderbar, putting in a larger free-er flowing throttle body/air intake makes the engine flow so much more air. When all that added air tries to go through the wastegate, it can't all fit through, so more goes through the turbo instead. This causes the boost to raise above the pre-set (engineered at Callaway) amount. The only way(s) to lower the boost creep are to remove the turbo and port the waste gate hole to be larger, restrict your airflow through and out of the engine with smaller exhaust or intake. (And guess what, modifying the geometry on a stock-ish wastegate is next to impossible) as a result, then we're headed back towards a "stock" condition. But, of course, that will lose power across the whole rpm band... The last way to achieve total control is with an external wastegate, boost controller and associated feedback with electro-mechanical controls. But this requires a new exhaust manifold and a new turbo, as well as the wastegate. If you're driving a DSM/Audi/Porsche or any other late model turbo car the mods that are available are endless and these parts are "off the shelf". Callaway? You may be better off getting a new set of clubs!
The biggest problem with modifying almost any parts of a turbo car with a stock wastegate and control is boost creep. (Different then a boost "spike") Creeping is when the boost goes higher then what it is set at while on the throttle. The higher the gear, the more it will creep as there is more load on the engine, so 5th gear is worse, 4th is bad, 3rd might creep a little..Even though the boost is being raised which you might want to do, Creep is not a good thing-- the safety systems that have been put in place in any "stock" fuel injected car can only work within certain pre-defined parameters. This is especially true on Callaways. Have you considered changing Micro-Fueler settings or have metered your A/F ratio or have even adjusted fuel pressure in response to --> Changing exhaust is easy.. dumping the cats is easy.. how it effects other components within the system is the real test. Recently, a turbocat guy came in here and boasted of mods-- looking for solutions and didn't listen carefully. Maybe this full page response will offer some clarity to the issue. THE CORRECT WAY TO RAISE BOOST AND EFFECTIVELY CONTROL BOOST ON ANY MODIFIED CAR IS WITH A BOOST CONTROLLLER! The problem(s) here with the Callaways is the hole in the wastegate isn't that big. Plus:
1) There is no user adjustable electro-mechanical boost controller on a Callaway. The wastegate is purely mechanical and was engineered to operate within CALLAWAY'S ORIGINAL DESIGN PARAMETERS. No crap if you modifiy everything else that your motor will suffer the effects of boost "Creep"
2) Modifying the wastegate is big $$$. Consider the fact that even finding a turbo housing is next to impossible for these cars.
3) What is your ECM fuel table, spark timing and injector pulse width doing from just changing exhaust..? Dunno for sure but guaranteed that it varies enough from car to car that a $300 dyno session is a walk in the park compared to spending close to $20k on an engine re-build. If your car is building more boost than the factory tuned it for initially.. it's time for a modified ECM program or at a minimum a tweak on the Micro-Fueler. Again, a $300 dyno session with A/F feedback is a necessity. It takes less than a nano-second to burn a hole at the outer edge of a piston and burn a ring land at the same time. Pooof!
Adding an aftermarket exhaust, dumping the cats, putting in a Wonderbar, putting in a larger free-er flowing throttle body/air intake makes the engine flow so much more air. When all that added air tries to go through the wastegate, it can't all fit through, so more goes through the turbo instead. This causes the boost to raise above the pre-set (engineered at Callaway) amount. The only way(s) to lower the boost creep are to remove the turbo and port the waste gate hole to be larger, restrict your airflow through and out of the engine with smaller exhaust or intake. (And guess what, modifying the geometry on a stock-ish wastegate is next to impossible) as a result, then we're headed back towards a "stock" condition. But, of course, that will lose power across the whole rpm band... The last way to achieve total control is with an external wastegate, boost controller and associated feedback with electro-mechanical controls. But this requires a new exhaust manifold and a new turbo, as well as the wastegate. If you're driving a DSM/Audi/Porsche or any other late model turbo car the mods that are available are endless and these parts are "off the shelf". Callaway? You may be better off getting a new set of clubs!
problems) will be higher than a stock car.
