View Full Version : Miles per gallon

douglas james
08-02-2005, 11:29 AM
Good Morning:

A few questions if I might.

1. At what speed (mph/rpm) does the 87 GN shift into overdrive. I spend most of my time commuting at 35 to 40 MPH and at 1800 to 2000 RPMs.

2. I have an external wastegate. Why would I want to adjust it and how do I do it?

3. The previous owner adjusted the boos so that the it does not exceed 13 psi and I want to increase it. How do I do so? How I far can I increase the boost before I need to modify the fuel system which is stock?

Thanks, folks.


08-02-2005, 03:46 PM
1. The TCC lockup is controlled by the chip and can be reprogrammed. Stock was somewhere around 40 MPH at light throttle. Lots of the aftermarket chips move it up a little (45-50 MPH) to avoid the "on/off" feeling when driving in city traffic. Lockup is governed by vehicle speed and load.

2. Depends on the brand/type? Deltagate? Plumbing? ATR gate? Racegate? Some gates have plumbing that you can put an air regulator valve in place and then manually adjust it up or down from the cockpit. Others have a screw in the wastegate body that puts pressure on the diaphragm when you screw it in or out to adjust boost (usually tighter is more boost). Many use a combination of both ... using the mechanical adjustment to get the "base boost" and then use the vacuum lines to adjust from there.

3. See #2.

08-08-2005, 06:00 PM
:crackup: mine shifts into OD @115mph in WOT.
1> locks ups @ 44mph which is annoying so i keep it in drive WOT locks at 60mph

2 . what ken said

3. I would check to see if you have the factory fuel pump they were lousy from the start replace with an xp or walbro. chances are if it has an external wastegate the guy might have upgraded the pump.