V70 T5 can I do the unthinkable & actually lower boost?

evdrive · Post by **evdrive** » 26 Aug 2011, 11:59

I've got a 1998 V70 T5M and love it!

My question has more to do with fuel economy. I've got it running very well, but you can only squeeze so many mpg's out of a high performance turbo engine. I'm not a speed demon and I don't track the wagon so I'm happy with the current performance. It's just that with times being what they are I would be nice to go farther on a tank. Is there an easy way to put a switch in the car to actually lower boost to help improve mileage and then switch it back when I need it? I've done some reading up and seen multi-stage boost controllers. Is that what I should be looking into? I don't need much boost when I'm just sitting in traffic on the way to/from work.

FYI, currently I get about ~21mpg with the Atlanta traffic I'm faced with. Even if I bring it up another mpg that's another 16 miles I get from my typical fillup which adds up.

Has anyone ever done this before?

I like to think of myself as thrifty not cheap.

Post by **JRL** » 26 Aug 2011, 12:27

I don't think anyone has but you can!!!
Adjust the wastegate the other way, loosen the rod instead of tightening it.
The boost will come in later and if you hit the sweet spot less boost averall.

May I suggest you sell the T5 to the many that are looking for one and buy a non turbo

Post by **JRL** » 26 Aug 2011, 14:55

BTW I also should mention that since T5s are sort of a dog off the line anyway, lowering the boost by re-setting the wastegate will result in a 0 to 40 or so time that's..... unbearable!

evdrive · Post by **evdrive** » 27 Aug 2011, 20:20

No way am I selling it! You know how hard it is to find manual transmission volvos let alone V70 T5's. I wanted a way I could easily switch back and forth from standard boost to low boost to help with fuel economy. I don't want to make the car a total dog all the time.

Post by **keepersboy** » 27 Aug 2011, 22:18

I'm thinking that in traffic your really not using the turbo anyway, so I kind of wonder if it affects fuel use. The extra fuel does not inject untill the manifold pres. comes up. I have a 94 850, 222 hp and a 98 v70 with the smaller turbo. I have noticed they both get around 25 mpg if I am careful and In my driving conditions, but with the 94, with the bigger boost, if I get a little throttle happy the mileage drops quickly

D_V_ENT850R · Post by **D_V_ENT850R** » 28 Aug 2011, 07:35

I found that when I fixed my boost I got better milage! When I got my car it was only capable of 6psi! Now that I fixed the issues and added some stuff I'm at 25mpg in my R! I was at 16mpg when I bought it! So going lower may not be the answer...

Post by **boosted5cyl** » 28 Aug 2011, 09:49

Changing the wastegate actuator pressure will not yield any fuel consumption improvement whatsoever, it may even make it worse. If you plan setting it, set it right or dont set it at all. Or go the other extreme and hold the wastegate open. I dont think you'll see and improvement in consumption by doing so however.
There's only so much you can do to make a 3500lb lump efficient when you are stoppin' and goin'. Your turbo is spinning, but its not boosting in any real, appreciable way.

For sure its pays to make sure things in your engine are as good as they can be.

Good ignition components, incl correctly gapped spark plugs. Good cables, cap and rotor.
Injectors in good condition, clear of crud for a good spray pattern (B12 cleaner is potent for this).
Fresh pre-cat O2 sensor (dont bother with the post cat, it doest affect peformance).
Clean motor internals, good compression (steam clean combustion chambers/AutoRX treatment to decoke ringpacks)
Correct alignment, correct tire pressures.
Fresh gear oil in the transmission (makes a nice difference in feel too)
No excess weight in the car, ie junk in the trunk.
Correct viscosity motor oil.

FWIW, 21MPG is about what I get with my V70 T5 with a slushbox on my weekly commute. Longer roadtrips I get between 27 and 30 depending on gradients and of course what speed I am doing. Honestly, if all of the things above have been done, the biggest improvements are going to be found in your driving techniques.

http://ecomodder.com/forum/EM-hypermili ... riving.php

Post by **jblackburn** » 28 Aug 2011, 10:28

The biggest improvement you can get from it is absolutely babying the throttle. Make your foot weigh as little as possible and shift early - I can let mine shift around 1900-2200 RPM and get pretty good gas mileage.

https://www.matthewsvolvosite.com/forums ... =1&t=38721

evdrive · Post by **evdrive** » 29 Aug 2011, 13:09

Thanks for all the advise guys. I think I just need to adjust my driving technique & do some of the mentioned maintenance to get her running tip top to eek out all the mileage I can. I did have a screw in one of my tires so that tire being low probably affected things too.

D_V_ENT850R · Post by **D_V_ENT850R** » 29 Aug 2011, 15:56

Bump tire pressure to 36-38psi!! Little help!!