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4AGE 20V Silvertop open throttles modification

Wanted to install open throttles to your Silvertop? The Silvertop is running on MAF which it needs to measure the AFM before entering the engine. However there is still a way to do this whereby to convert the Silvertop ECU to Blacktop ECU and modify the ITB. Below is the list of the differents between Silvertop and Blacktop.
  • The Silvertop Throttles need to run on an AFM due to the ST ECU The Blacktop throttles use a map sensor
  • Stock ST Throttles generally cannot be run open because the ECU requires the air to be measured by the AFM BEFORE it goes into the engine.
  • Stock Blacktop Throttles can be run open because the MAP sensor reads vacuum pressure from BEHIND the throttles.
  • The Silvertop Throttles CAN have a MAP sensor adapted to them. You have to wire the MAP plug and an Intake Air Temp plug and sensor in place of the AFM. I don't know if the ST ECU can interpret this correctly or not so a BT ECU may be needed as well.
  • The Blacktop Throttles have a port the reads the Vacuum behind the throttles
  • The ports on the Blacktop Throttles are larger than that of the Silvertop.
  • The Blacktop Throttles are physically larger as well, something like 5mm each. The Silvertop airbox does not bolt up to BT ITBs.
  • The Blacktop and Silvertop ITBs share the same bolt pattern on the plate, allowing the blacktop throttles to bolt right onto a Silvertop head. Use a blacktop gasket.

Blacktop ECU and special adapter harness to go betweeen the ECU and my ST harness

An older photo of engine w/ Silvertop throttles installed

Throttles removed I should note here, I sanded the surface lightly to clean it. I used a 90-deg cross-hatch pattern.

Backplate of both throttles. Blacktop on top. Note the difference in size of the port. You can also see the channel the MAP sensor uses to measure vacuum

Front of the ITBs with the Blacktop throttles on the bottom. The number one Cylinder is on the left hand side of this picture. You can see the white valve on the blacktop throttles near the TPS. A rubber line connects this to the MAP sensor.

Blacktop Gasket on ST throttles to show port size difference. I should note here that the ports on the head are just as small. I am still trying to find out if they could be opened up safely to allow for unrestricted flow.

Blacktop Gasket on Blacktop Throttles

Blacktop Throttles installed

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