I had sold the TBI unit earlier in the cars life because I had always planned on doing something bigger than the stock TBI could handle. I aquired a throttle body off of a 5.7 litre chevy truck (it looks almost identical to a LS throttle body). Picture to the right shows size difference from stock opening to new throttle size. WOW that's huge. So now I have to modify the stock intake to get the new TB to fit. This is going to take a lot of work. First I started by cutting off the coolant passage that ran under and around the intake, GM put it there for driveability with the TBI, but I am going to convert to port injection so i don't need a hot manifold. As I cut more and more of the coolant passage away I realized that the intake was very small inside. Notice in the second picture how small the opening is from the plenum
to the runners. This can not be good for flow and HP. After some consideration I decided to remove the plenum and the adjacent restrictions and start over to correct GM's poor design. See Third picture.
After having gotten the intake down to short runners and a plate I started to mock up the shape of the intake using cardboard to see how big it needed to be to allow me to use the throttle body, and to see if it would fit in the car. The plenum was looking quite huge to accommodate the size of the TB and spacers needed for throttle linkage clearance. The setup was looking like a low budget version of one of
Ron's Flying Toilets. At the same time I was researching intake design theories on the web trying to get some idea of what I sizes I needed to accomplish my goals.I found a few discussion boards where the guys were saying that to decease turbo lag the intake needs to be smaller and have no large size transitions. I had designed an intake tract that went from 2" to 3.5" to a large plenum, lots of lag in my plans. Back the the old drawing board. So I started my search for a new throttle body (smaller but still good sized). Working in a shop that does lots of engine work, we have a somewhat decent selection of used parts and after some digging I found the throttle body off of a 3100 v6. This allowed me to still use the OE
IAC motor and TPS sensor, so my ECM will be somewhat happy. Next step is to install a piece of aluminum pipe to eliminate the bellmouth shape, and allow me to keep all piping under 2.25 inches, that should allow the turbo to spool up really fast.
I had sold the TBI unit earlier in the cars life because I had always planned on doing something bigger than the stock TBI could handle. I aquired a throttle body off of a 5.7 litre chevy truck (it looks almost identical to a LS throttle body). Picture to the right shows size difference from stock opening to new throttle size. WOW that's huge. So now I have to modify the stock intake to get the new TB to fit. This is going to take a lot of work. First I started by cutting off the coolant passage that ran under and around the intake, GM put it there for driveability with the TBI, but I am going to convert to port injection so i don't need a hot manifold. As I cut more and more of the coolant passage away I realized that the intake was very small inside. Notice in the second picture how small the opening is from the plenum 
to the runners. This can not be good for flow and HP. After some consideration I decided to remove the plenum and the adjacent restrictions and start over to correct GM's poor design. See Third picture.
After having gotten the intake down to short runners and a plate I started to mock up the shape of the intake using cardboard to see how big it needed to be to allow me to use the throttle body, and to see if it would fit in the car. The plenum was looking quite huge to accommodate the size of the TB and spacers needed for throttle linkage clearance. The setup was looking like a low budget version of one of Ron's Flying Toilets. At the same time I was researching intake design theories on the web trying to get some idea of what I sizes I needed to accomplish my goals.I found a few discussion boards where the guys were saying that to decease turbo lag the intake needs to be smaller and have no large size transitions. I had designed an intake tract that went from 2" to 3.5" to a large plenum, lots of lag in my plans. Back the the old drawing board. So I started my search for a new throttle body (smaller but still good sized). Working in a shop that does lots of engine work, we have a somewhat decent selection of used parts and after some digging I found the throttle body off of a 3100 v6. This allowed me to still use the OE 
IAC motor and TPS sensor, so my ECM will be somewhat happy. Next step is to install a piece of aluminum pipe to eliminate the bellmouth shape, and allow me to keep all piping under 2.25 inches, that should allow the turbo to spool up really fast.
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