Boost and Milage

[MKIII87Turbo]

Two questions. On my sons 95 GST at idle the boost is running about 1/8 on the gauge. Is this normal? What type of mileage should he be getting? Right now its at 16 MPG. Of course like me, he has a heavy right foot, but my Supra gets 16.

[kjewer1]

The stock guage is boost and vacuum, so its probably not in the boost range. Unlike the 1g guage, the 2g doesnt provide any numbers on it. 16 mpg sounds way too low even with a heavy foot, for stock turbo and mild setup. Even running mid 12s I would still get 30 on the highway, and 25 average. And I spent most of the time driving like an asshole A failing front O2 sensor can really kill mileage. If you have access to a logger or a scantool you can either watch for a lazy O2 voltage trace, low values, or high fuel trim numbers. Most poeple will just replace the sensor though since all this sounds like greek to them. But they are now about 90 bucks from Mitsu, and I only use Mitsu o2 sensors in the front location (use generic in the rear if it saves cash, it doesnt affect fueling at all).

[TreeFrog]

my stock boost gauge read nothing at idle.

i get 23 mpg city. he probably has something causing poor fuel economy. check normal maintnece. fuel filter, air filter, plugs & wires, exahust, tire pressue, boost leaks, etc also check to see the SMIC is cleaned out.


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Edit: my boost gauge is at 1/8 boost on idle. i checked my gas milage today and it was 16. now i'm pissed!!

[kjewer1]

Its reading vacuum. Those "guages" vary a lot, but perhaps there is a vac leak or something else lowering idle vacuum. Either way, I give no credit at all to the stock boost guage that doesnt even measure boost.

[MKIII87Turbo]

Thanks for the info. I thought I changed the plugs and wires when I bought it for him, I thought wrong.

[GotGrip666]

and do the filters too and maybe the timing belt