Major drop in MPG after Do88 Intercooler upgrade

[aewoodhouse]

Hi All,

Not getting anywhere with my internet searches about this so forgive me if guidance may already exist. I installed a Do88 intercooler on my 2007 V70R and MPG is down about 25%. Have now been through 3 full tanks of 93 octane. No change in driving conditions / habits.
Air filter was also changed at the same time, plugs are relatively new and all other major services have been done in the last 15k miles.

Initial reinstall of airbox caused a small leak that triggered a MAF code but leak was fixed and code was cleared (w/DICE unit and VDash). No other relevant codes past or present. I realize that given the nature of the install, a vacuum leak is the likely culprit, but the car runs perfectly and again - no codes to indicate one. In an effort to avoid littering the internet with more generic MPG advice, I want to emphasize that this was a sudden drop that came on ONLY after the intercooler install. Before the install, I could get about 230 out of a tank - mostly very spirited city driving. Now its a stretch to get 175. Thanks for any ideas you can lend.I thought this was supposed to give a slight bump to MPG.

[scot850]

My opinion is there is either a leak as you surmise, or something has not been reconnected. Like you said, it only started after you did the swap, so something in that process has caused the sudden change. Try to run back through what you did in the swap in your mind, and remember what was disconnected and check it all.

Has your muffler tip color changed? If it has turned more black or white, something is not connected or an air leak and running lean.

A lot of work, but if you still have the original, worst case swap it back and see if mileage returns.

Neil.

[jonesg]

have you smoke tested it?

[scot850]

Good point, but OP may need to find access to one or build one. Quite cheap on Amazon these days.

Neil.