12 miles per gallon!!

[viperkd77]

Prior to exhaust install.... bcs restrictor removal, kn filter, dump tube cut, mbc set at 15psi, got 19-24 mpg...

exhaust install 3inch turboback.... 10-12 mpg, sluggish driving, fast in wot, low torque, bogged ran like a boost leak during partial throttle...black smoke...also sounds like a tractor and really raspy and ricer (in drive, in park, A/T, sounds like it should, deep and throaty)

**not sure if done the same day or a few days after exhaust install (think i did this after exhaust install bc of bad gas mileage)... used fuel injector cleaner with full tank of gas. Did nothing...

boost leak test... leak in tb shaft seals... put 1g tb on... bad idle, but no major boost leaks....

also install dsmlink, adjust tps for 1g tb and fix idle... but still runs like crap after no boost leaks.... and 10-12mpg

tune fuel ratios... fast and smoother in wot, but still eats gas at like 10.5-12.5mpg... idles well.

replace 02 sensor even though good link readings... no fix...

REINSTALLED stock exhaust.... replace ground strap near rear 02.... STILL bad mpg and sluggish!!!

Leaned fuel out even more with link and adjusted timing, faster in wot, but still sluggish and runs like it has a boost leak... Also, got insight from a friend that my bov could be bad and i do have a boost leak...

Did boost leak test last night from turbo inlet... pressurized at 12psi... back down to 5psi within 3 seconds, then slowly from 5 to 0 in like 20 or 30 secs... (is this normal?) slight leak in bov out of recirc hole... why?

Also, i hear a leak on the drivers side of the car...

Also, i hear bubbling

Also, it smells

Do i have boost leaks or not and what in the world is going on with my 97 gsx a/t.. it has been like 2 years since the day she was sitting pretty... PLEASE HELP WISEMAN...

 

[spyderturbo007]

Boost leaks will cause an a drop in gas mileage due to the inflated airflow numbers from the MAS. Also, I would take a look at your front O2 sensor, which is the cause of bad gas mileage 99% of the time.

 

[ZmanIV]

1+ for the O2 sensor

 

[crimsondragon]

He already replaced the O2 sensor. It's definitely running rich though since black smoke is coming out of your exhaust. Check your spark plugs to see if they're good.

 

[Gs Dewd]

Check for leaks everywhere. Vacumme everything. Also check your mas for dirt. you are running way to rich. Most likly reason is your pulling in unmetered air and the ecu is trying to compensate for it but as you see is doing a bad job of it.

 

[Boost92awd]

First off you need to do another boost leak test the right way. If your loosing 5 PSI in 3 seconds during your test you definitly have some leaks that need to get taken care of. Start of by spraying all the vaccuum lines, UICP and LICP couplers, BOV, Injectors, TB, down with soapy water this will help your find all the leaks much easier and help find the real little leaks that you cant hear. Now pressurize the system to about 20 PSI. Then just keep doing boost leak test till you find them all. Having boost leaks will cause your car to run rich and give you bad gas mileage.

 

[viperkd77]

I replaced the 02 sensor a while ago........ as qouted above..."replace 02 sensor even though good link readings... no fix..."....

What can I do to Dsmlink to see if my MAS is bad or not... That makes sense though. If they car is gettng unmeter air, then the ecu will simpply dump fuel in... This could explain why i still get full boost on my boost guage too...

 

[viperkd77]

More testing today.... Did boost leak test on tb elbow, past the bov...

The pressure drops from like 11 to 5 psi in about 6 seconds. Then it drops from like 5psi to 0 in about 10 seconds... The boost is leaking bad and i can hear the BISS screw (im 100% sure) and the TB shaft seals leaking ( I think). I didnt hear leaks newhere else.

Do u guys think this is causing my 12mpg and poor performance.....remember i got 20-24 mpg before the TURBOBACK and FUEL INJECTOR CLEANER...

ALso, i fixed all boost leaks before and it still ate gas...

What else could it be????

 

[crimsondragon]

Check for exhaust leaks as well. I doubt it'll affect your mileage but check anywy. Get some Seafoam and dump it in. Look for white smoke around all the flanges of your exhaust as well as smoke from the engine bay.

 

[snowborder714]

There is no way using DSMlink to check you MAS. I would do another boost leak test and use soapy water as boost92awd suggested. This way you can 'see' your leaks instead of trying to listen for them. Your pressure shouldn't drop that fast though. That drop is too big/fast to be your tb seals and BISS. Have you checked your intercooler couplers/clamps? Also make sure you don't have any random vacuum hoses or electrical connectors lying around unconnected. Maybe you disconnected something to install the exhaust and forgot about it.

Why did you do the BSC restrictor mod when you have an MBC? The MBC replaces the BCS.

You also could probably switch to BPR6ES plugs since you're running low boost. They will work better for you than the 7's.

When you log the front o2 sensor in DSMlink does it cycle between .05 and .95 (or so)? And are all your other setting in DSMlink correct for your current setup (ie inectors)?

And I hope you're actually calculating mpg using gas receipts and a calculator and not using the mileage feature in DSMlink.

 

[ZmanIV]

I don't know how the second O2 sensor affects mileage but did you do anything funny to it when you installed the exhaust?

 

[bling5tatus]

I don't know how the second O2 sensor affects mileage but did you do anything funny to it when you installed the exhaust?

If the o2 sensor decides it is going to read lean all the time your car will run rich to try to compensate... also, I believe if the ecu senses a dead o2 sensor it will go into a "safe mode" in which it runs richer than normal all the time to prevent you from grenading the motor.

 

[Splitpi]

If the o2 sensor decides it is going to read lean all the time your car will run rich to try to compensate... also, I believe if the ecu senses a dead o2 sensor it will go into a "safe mode" in which it runs richer than normal all the time to prevent you from grenading the motor.

In addition, the ECU richens up the combustion as part of the CAT testing to ensure the cat is working properly. And reads the difference between front and rear. A faulty rear can cause the ECU to get confused.

 

[turboglenn]

Driving habbits have a lot to do with it too. You keep mentioning WOT, well that brings you down to 6 or less MPG while wide open. My can is lucky to get about 15.5 MPG in daily driving. factors like turbo size, how often you spool it and how hard you accelerate will all play a role in you getting crappy mileage.

fill up your tank and drive 50-75 miles on the highway only, then top the tank back off and see how many gallons it took, then divide miles by gallons and see what you get on the highway

If your car is really as stock as your profile says (stock turbo stock injectors) then you definitly need to find out what is wrong though, even beating the piss out of a stock car with stock injectors whould get at least 15-16mpg

Also remember that with everymod that lets more air in and out of the engine there will need to be fuel to match it so just fcount on every mod you make taking a little more MPG away from you

 

[viperkd77]

I did the boost leak test upstream on the TB ELBOW.... It went from 10psi to 0 within 20 seconds... therefore the problem isnt the intercooler,piping, turbo or bov... It is after that... Either the tb, intake mani, fuel injector seals, something...!~?!?!??

I was told there was a second ground strap on the car up by the front 02 sensor on 2g's.. I only replaced the rear one by the rear 02....

I will do another test and spray soapy water too...

** I dont know how a new turboback exhaust led to boost leaks causing 10-12 mpg....

SOmething else must have seriously happened....

The front 02 was replaced and reads good oscillating nbrs.. It reached up to 1.04 volts without a dsmlink tune, which i know is high and rich.... BUt it does work..

I looked in the back (inside) of my 2g tb plate and inside my turboback downpipe entrance by the flange and in bo0th spots, all u see is black soot... brutal...

Maybe my rear 02 is shot... I will have to do a dsmlink check.... We did take a torch to get the rear 02 out the first time and i simply reput it in.... THe car didnt even give me a cel when i had no cat... so maybe it is screwed up.... I was told that a bad rear 02 didnt matter tho?? is this true?

 

[crimsondragon]

The rear sensor just makes sure your cat is working right. It takes the data from the front and compares it with the rear. The front is the major factor in fuel consumption.

 

[viperkd77]

** I dont know how a new turboback exhaust led to boost leaks causing 10-12 mpg....

SOmething else must have seriously happened....

What is it?

 

[crimsondragon]

Does it matter? Have you fixed all the leaks and done another test at the turbo to be sure it's free of leaks?

 

[viperkd77]

No. Thats the next step I am taking. When i fix the tb shaft seals and BISS screw and make sure there are no leaks.... I will go from there.

How long should a 2g gsx stock motor hold boost for on a pressure test?? I hear 1 minutes, I hear 20 minutes... How long is good. Also, what is the deal with oil bubbling?Good or bad, normal or not normal? I only hear bubbling for like 1 second, then its gone.

 

[crimsondragon]

What you mean oil bubbling? How do you know it's oil bubbling? It could be your coolant as well or power steering or brake fluid you know...
Base your boost leak test off this.

1. Disable your mbc.

2. Turn your motor to 30* ATDC to avoid valve overlap.

3. Start your test at the TB elbow and focus on area behind the TB first.

4. Spray soapy water at TB gasket, BISS, TB shaft on both sides, IM gasket, injector insulators, brake booster, afpr and all vacuum lines/connections.

5. Open your oil cap and listen for leaks. (PCV, valve seals/guide, rings)

5. Listen to your tailpipe for leaks. (EGR, valve overlap, jumped timing, bent/unseated valves)

6. Once all leaks are fixed, move the tester back to the turbo inlet.

7. Spray down the compressor cover (known leak), BOV return/flange (DO NOT TAP YOUR BOV LINE FOR YOUR MBC!!!), IC end tank/fins and all connections. Re- test.

8. Note that you will leak air into the crankcase through the turbo seal but do not panic, this is normal during a static pressure test as long as there are no shaft play.

The desired test result from the begining of the LICP (bypassing turbo) is around 20psi (on boost gauge) with the compressor set at 30psi, while taking no less than 30 seconds to bleed down to 0.

As a reference, my last test on my 500 mile new engine, I was able to pressurize the system to 25psi, bled down to about 16psi (my 1G bov) in about 30seconds, then took about 3 mins to 6psi and just kinda lingered there for a while. It's not easy to do but the point is it's possible. My next goal is 30psi After motor break in and Dodge modding my BOV. A boost leak test is one of most pita but important regular maintenace task, the key is patience and endurance

 

[snowborder714]

Did you warm up the engine before performing the boost leak test? I'm assuming that's when you heard the bubbling.

And it should at least hold a good bit of pressure for a minute or two. Mine will hold 25psi for a good while as it drops and then it'll take a long time to go from like 7 to 0psi or so. I'm don't have any exact times since it's been a while since I did a boost leak test.

 

[crimsondragon]

Has this been resolved yet? I just remembered something very vital. You should reset your ECU. I vaguely remember reading about it somewhere on this site but it's been too long. I actually just installed a turboback as well and I was getting less than optimal mileage till I reset the ECU. She's running better now. Give it a try.

 

[viperkd77]

I have had the battery disconnected many times and reseted the ecu hasnt done anything...

 

[viperkd77]

however, for one reason or another, I do have a significant battery drain. If the car sits for more than a week, the battery is too drained to enable the car to start...

 

[crimsondragon]

How long have you had the battery? Put a new one in if it's old. Last thing you need is another problem. If it's not the battery and is actually something with the alternator, check to see if it's going out the door.