I put a 64/14-71 on my 2006 last week. I used to run 5-6 psi on the freeway at 70mph, now I am running 1-2 psi with the larger turbo. Have others gotten the same results? Is your fuel mileage suffering from this? It seems to run good and spool up quickly, just wondering how this affects everything. Thanks

 

It's common to see reduced boost while cruising with a bigger turbo, but that sounds a little too low. Is there any haze while you're cruising? Have you done a thorough leak check on the manifold at the head and turbo flange?

What's your max boost look like?

 

that sounds normal to me too as that's what my 64 did. At 70 running with low rpm's the drive pressure is very low so you're not going to be building a lot of boost.

The joys of owning a larger turbo :-)

 

I'll see 2psi or so at 70mph w/ a 62/14.

 

Yepper... With my 5k turbo that's what i would run too!!

 

I drive around and the boost gauge barely moves lol. in town its like the boost gauge doesnt work. but when it needs to do its job it does

 

I see around 4 psi at 75+mph crusing with my SPS66. I does depend on how sensitive your gauge is on the low and high end. My autometer gauge does not really start moving accurately until I see around 4psi on the TST Remote.

 

Mine is about 4 psi at 75.

 

My 66 is 4 psi at 120 kmh, my fuel milage is still decent.
Nick.

 

The new turbo is moving the air more efficiently. The pressure is down, but it's moving just as much if not more air that the stock turbo was.

 

Will going to a bigger turbo hurt fuel mileage, or will it not affect it at all?

 

I noticed a drop of 1-2 mpg with the 62-14 but performance improved so much I wouldn't go back.

 

I see about 7psi at 80mph with my HTT 62/13.

 

Not a chance. When A turbo is operating at 30-40 psi, a bigger compressor might move more air (mass) at lower pressure, but when they're both on the bottom end of the map (or not even on it), pressure is pressure, and 6psi is more air than 4psi.

It's part of life with a bigger turbo-- lower cruising boost means higher average EGTs.

jh

 

I just got back from a 400 mile trip last night. TST 1, X2 milage max, at 65-70 I got 20.4 mpg. 75-80 was about 18.2. This is with a new 66 with only 100 miles on it when I started! On mine the bigger turbo didnt hurt my milage. My exhaust temps for most of the way were around 600-650 and boost was 2-5 psi.