n00b- Just bought 97 GST, TERRIBLE Gas Mileage, Upgraded Turbo?!

[arbalest]

I'm new to DSMs and Turbo cars in general. I got rid of my 4.0 Ranger for something that was fast and supposedly got good gas mileage... Besides I don't have dirtbikes to haul anymore.

Its a 97 Eclipse GST. 160xxxmiles, and runs fine... I just get TERRIBLE gas mileage. 18-19 Highway!

There are no Check Engine Lights or anything of the sort. The guy I bought it from just said he had a shop put a little larger turbo in after the original one's bearings went out. Other than that, it just has a K&N filter.


What the heck is going on? It occassionaly has a LITTLE idle problem at startup (in the freezing cold), other than that its fine.

The exhaust smells like its running rich as well...


Any ideas? Remember I'm new to turbos.


Thanks!

 

[turbosax2]

Take pictures of the turbo so we can identify it for you.

Having a larger turbo should not effect gas mileage.

 

[arbalest]

Take pictures of the turbo so we can identify it for you.

Having a larger turbo should not effect gas mileage.

I'm checking if the guy can get ahold of the shop and let me know... They said it is in the original housing, just upgraded internals?

 

[bane3d]

I know my car was getting about that from the day I bought until the day that the engine blew. I'm hoping the new 6 bolt being dropped in right now will give me something a little better than that. I see some people get as much as 25mpg on highway. If you thought this car gets good gas mileage, you got the wrong version. The NT version gets decent gas mileage, the turbo required premium and gets ~20mpg from what I've seen. Sucks in my household since I have a Oldsmobile Silohuette, Cherokee 4.0L and my eclipse; all of which get ~20mpg.

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[silverbullett]

Mine had the same problem. I tracked it down to a multiple boost leaks and a faulty fuel pressure regulator. Now I'm getting like 26-28 highway, as long as I can stay out of boost, which is next to impossible. I'm going to change my throttle body seals and gasket next.

 

[GofaST4life]

upgraded internals?? on a T25??? idk about that...

but def. get some pics up of the turbo and the engine bay in general...

 

[MrBoxx]

I would say 18-24mpg would be fairly average for these cars. Considering the age/mileage of yours, 19 seems about right. If you wanted a car that got GREAT gas mileage, a Honda Civic or a Toyota Corolla would have been more appropriate. That turbocharger and low-compression engine on your car don't do much for fuel economy. To really see what's going on, you'll need some sort of logging equipment (DSMLink, pocketlogger, etc.) to find out what kind of injector duty cycles you're running, see what kind of timing numbers the car runs, and to check for any knock or phantom knock.

Regarding the idle issue: Our cars have what's called a FIAV (Fast Idle Air Valve) that raises the idle rpm on cold startups to warm the engine faster. You should notice that if you leave the car running after you start it up, the rpms should slowly decrease to about 800 or so (normal).

Other things you MUST do:
-If the car indeed has a new, larger turbo on it, you MUST get an aftermarket boost gauge. This isn't negotiable.

-Do a boost leak test as soon as you can. BLTesters are cheap to make from Home Depot, and can really fix about 50% of the problems new owners have with their cars.

- Get a pic of the turbo, and if possible, get a picture of the compressor wheel (you'll have to take the intake pipe off to see it) in case we need to distinguish between a 14b and a 16g.

- Are you recirculating your blow off valve?

-Replace your spark plugs with NGK BPR6ES. Do NOT under any circumstances fall for the auto parts store salesperson's sales pitch about platinum or iridium plugs giving you more horsepower or gas mileage; I've DONE that job, and it's all BS, at least for our cars. NGK BPR6ES, regardless what they tell you should be in there. If no one has them in your area, the dealership should.

 

[MrBoxx]

upgraded internals?? on a T25??? idk about that...

but def. get some pics up of the turbo and the engine bay in general...

Possible T28 conversion.

 

[arbalest]

MrBoxx --

Thanks for the post. I wasn't expecting GREAT gas mileage, but somewhere around 24-25 would be nice.

I'll get pictures of the turbo asap. Going to replace the plugs with the NGK's.

Will do BLtest asap as well

Its crappy weather here in KansasCity


What is "recirculating blow off valve"?

 

[MrBoxx]

What is "recirculating blow off valve"?

The blow off valve (or bypass valve as ours technically is) is the little solenoid that releases pressurized air from the intercooler pipe back into the intake pipe. This reduces the chances of the turbo being damaged from pressure spikes when the throttle plate closes. In other words, it's the thing that goes "Psshh" when you let off the gas or shift.

Now, some people want to make that noise louder because they think it's cool, so they take off the hose that goes between the air intake pipe and the BOV. This is called "venting to atmosphere" or "venting a BOV" and it's not something you can just do to one of these cars without a few other modifications. Otherwise, it screws up the A/F ratio, alters idle, and is a possible boost leak issue, etc. etc. You can read up on that stuff later. All you need to know is, make sure there's a little elbow hose between the intake pipe and a valve on the upper intercooler pipe.

 

[TurboTsiThatFly]

recirculating the blow off valve means sending the air released from the bov back into your intake system . IE recirculating the bov. because the factory ecu (engine control unit) reads the measured amount of air the bov releases into the intake system.

 

[turboglenn]

The rich smell could be from a gutted cat. My car has no cat and shoots wet suit out in the mornings that's so black it stains the driveway , But my car is heavily modded and when t's 14 degrees outside it takes a lot of fuel to keep it running til it's warm anoutgh to vaporize fuel from internal heat.

Being tht modified and with 720 injectors and a turbo that doesn't spool unill about 4500 in 1st gear i have to use a lot of fuel just getting off from the red lights. The car is on a rough tune stable ranges are 14.7 - 13.4:1 (i'm shooting for that perfect tune that would eliminate closed loop ) and right now I'm not running closed loop, because i'm stil changing things for this springs when the clicks go back on. I'm getting 16-19 in town, depneding if i get on it a lot or not. On the highway i can get 26MPG @70-80 MPH. I can run my car lean with the cruise and get upwards of just over 30 when i'm running about 17:1 under light cruise. ( i have realtime fuel trimming knobs in the car sp i just back it down till it's as lean as it wil get before breaking up too badly), I think there's some timing to be played with to make this even more efficient and more stable in cruising.

Sorry I rambled, hopefully some of eh info was helpfull or at least a relief to hear it's not TOO abnormal

 

[arbalest]

The rich smell could be from a gutted cat. My car has no cat and shoots wet suit out in the mornings that's so black it stains the driveway , But my car is heavily modded and when t's 14 degrees outside it takes a lot of fuel to keep it running til it's warm anoutgh to vaporize fuel from internal heat.

Being tht modified and with 720 injectors and a turbo that doesn't spool unill about 4500 in 1st gear i have to use a lot of fuel just getting off from the red lights. The car is on a rough tune stable ranges are 14.7 - 13.4:1 (i'm shooting for that perfect tune that would eliminate closed loop ) and right now I'm not running closed loop, because i'm stil changing things for this springs when the clicks go back on. I'm getting 16-19 in town, depneding if i get on it a lot or not. On the highway i can get 26MPG @70-80 MPH. I can run my car lean with the cruise and get upwards of just over 30 when i'm running about 17:1 under light cruise. ( i have realtime fuel trimming knobs in the car sp i just back it down till it's as lean as it wil get before breaking up too badly), I think there's some timing to be played with to make this even more efficient and more stable in cruising.

Sorry I rambled, hopefully some of eh info was helpfull or at least a relief to hear it's not TOO abnormal

So is there a way to tune it after i go thru all the routine/tuneup maintenance?

 

[TAndrus]

I have the same problem as you. I'm getting 14-15mpg city. I bought it thinking I would get atleast 19-20mpg city. I live in KS also so the cold weather seems to murder my car till it's warm.

 

[Defiant]

Those are fairly normal mileage numbers. You can gain another few by driving it like a slow car that gets better mileage, but if you're using the turbine to cram air into a motor, there's going to be gasoline to go along with it.

 

[turbobird14]

check you o2 sensors as well... if those are bad or worn... those are the sensors that regulate your air/fuel ratio... on my dsm i had a bad front o2 and my check engine light wasnt on... it had full 3" turbo back.. and still no cel. cars are weird...

 

[arbalest]

Question:

At idle my boost gauge says its just a litle under the middle.. I thought at idle it should be sitting at (-). (stock)


Is this messed up?

 

[allwheelTSI]

That could prove to be a vacuum leak, though if its the stock gauge they are not known for their accuracy.

 

[Splitpi]

Stock boost gauge is the ECU's guess at boost levels. boost is not actually measured.

I would do a boost leak test. It is likely that after the shop changed the turbo, they didn't bother to boost leak test the car. This will cause you to run rich, and have crappy fuel mileage.

 

[h8r]

I would look at o2 sensors, and V leaks as stated! For you, some sort of logger should give you a nice idea of the fuel consuption issues. If there is a turbo upgrade(i would presume big 28) maybe the car was never tuned, the injectors may be dumping large amounts of fuel. You could easily wash cylinders with excessive fuel. Be Careful.

 

[puskaitis]

I recently took a long trip. I saw 36 MPG. That is 499 mi. on the trip Odometer! I'll keep checking, but 30 MPG is not a problem. I just replaced a cam angle sensor and I am waiting for the ECU to settle in.

 

[meliketoball]

upgraded internals?? on a T25??? idk about that...

but def. get some pics up of the turbo and the engine bay in general...

They're called sleeper t28's. Go buy some fuel injector cleaner, gas improver or whatever STP makes, and fill her up with some fresh gas!

 

[arbalest]

Here's what I'm talking about... Something is definitely wrong.. Even if the stock boost gauge is not that accurate, it shouldn't be boosting @ idle should it?

 

[danny_l_2005]

the stock boost gauge that comes with the vehicle is useless. In order for accurate readings you need a mechanical boost gauge like autometer and other brands. Like most said it might be several boost leaks that are causing you to have lower gas mileage. Here's how to check for boost leaks 2G Turbo DSM Boost Leaks -How to test and fix It is preferred if you use a air compressor and limit regulator to around 25psi than using a bicycle air pump

 

[rich3389]

The picture looks normal.