Boost...

[Jordan72]

Hey guys I have an early 99 with a 6637 intake and 4 to 5 inch straight piped exhaust. I only get about 12 miles per gallon and have tried a lot of the "common fixes" such as the EBPS and tube as well as additives, filters, a new set of injectors keeping it under 1900 rpms or so and anything else I could try. I also tightened all my boots at least I thought I did, but now I'm reading people saying while cruising at 65-70 they are getting 5-7 lbs... I started watching mine and got these numbers...

56 mph and 1500rpm 2psi
67 mph and 1750rpm 0psi
73 mph and 1900rpm 1-2psi
77 mph and 2000rpm 3-4psi

they are readings once I get up to speed and have my foot in the throttle just enough to cruise at that speed...

being that my truck has the smaller early 99 turbo would it make less boost or should I investigate further into boost leaks being the cause of my bad mileage...?

Thanks in advance

[stuntlife21]

check ur uppipes i had the same problem if they arent leakin id try an aftermarket wastgate the stock one doesnt hold after time

[jacobford]

Originally Posted by stuntlife21

check ur uppipes i had the same problem if they arent leakin id try an aftermarket wastgate the stock one doesnt hold after time

also make sure your boots aren't cracked or leaking somewhere, i know you said you tightened them, but try spraying them with soapy water like you would a tire for leaks... a small mirror will help see behind the turbo so you can check your up pipes...

[dentexpowerstroke]

have you checked to see what that max boost you build? I know cruising 60-70 I only hit maybe 2-3 psi if that. Also what are your egts at that speed?