LT1 gas mileage

[deja]

Yep I am running the PCV hose. I think I got it on EBAY. Can I assume you removed the EGR stuff too? Have you stuck a vacuum gauge on the engine yet? You live in California, how are you going to pass the smog laws with that open exhaust and no PCV? Nice thing about Georgia if the car is 25 YO, no smog requirements.

 

Heres an Idea. The crankcase vent valve hose running from the right valve cover to the trottle body. I don't have one. I have just a breather on the valve cover. Are you guys using the valve and hose to the TB? Could this be a problem.

[78Z/250GTO]

As long as it passes your Calif, smog test I don't understand the big concern about MPG. You converted to a V8 for the power,speed 'wheel spins, bragin rights,and any other number of reasons I don't think MPG was on of the build concerns. IMO

[deja]

I for one drive my car everyday so mileage is a concern. Granted not the biggest concern but at $2.50 a gallon it matters. No point in throwing money away and his car should be getting a lot better mileage than it is for a stock LT1 in a very light car. To me that points to issues that could also be hurting performance. Of course if I was that worried I wouldn't have put that LT4 hot cam kit in it, LOL.

 

 

As long as it passes your Calif, smog test I don't understand the big concern about MPG. You converted to a V8 for the power,speed 'wheel spins, bragin rights,and any other number of reasons I don't think MPG was on of the build concerns. IMO

[Z48LT-1]

Have you considered data logging? I'm eons away from getting my LT1 on the road but my research suggests you can learn a lot about what's going on in your engine by data logging. Alas, the '93 has the tuning parameters on an eprom (or is that an eeprom?) so it's a little more involved than '94-'95, which are flash-upgradable. Regardless, apparently, Freescan might allow you to look into what your O2's think might be wrong with your combustion process.

 

Which reminds me to ask whether you've had a chip burned for your current setup in the first place?

 

Good luck in your efforts, regardless.

 

Cheers -- Gary

 

-------------------------------

 

It has long been an axiom of mine that the little things are infinitely the most important.

 

Sir Arthur Conan Doyle

[lgoodson@pacbell.net]

I haven't did a vacume test yet but if I place my finger over the port at the throttle body, I don't feel any suction. The manual says to check for engine leaks like valve covers and pan gasket. I have no leaks. Can't explain the lack of vacum yet.

In Calif. 75 and older= no smog check. I picked up a crankcase valve and hose at the wrecking yard off a 94 Z28 but with no vacum, no difference was made.

 

The reason I am concerned about mileage is because I want to drive this car places other than to car shows like to Vegas or to Texas or lots of places and at over $3.00 per gal, it adds up. Besides, when people on this web site tell me that I should get 22 to 28 MPG if I do this swap and I spend the money to do the swap, I think I should get what I was told I would get or at least come close. My last mpg check yesterday revealed a whopping 11.2 MPG around town and I was trying to keep my foot out of it and shifting in the low 2000 rpms and still no mileage. What is wrong here?

 

Right now my Dodge Ram 2500 is in the shop for some metal straightening so th Z is my primary.

 

PCMS For Less did the chip reprogram. If that had not been done the car would not event start. Security concerns you know, Vatts I believe it is called. I should check with them to see if they did anything to cause the poor fuel economy. The reprogram was done by the PO

Data logging or power tuning is something I haven't done or even know where to go to have it done and have it dynoed. Just still geting the bugs out

[Inferno 08]

If the car has been reprogrammed there's a possiblity that the tune they put on it has it running rich, which would again explain the terrible mileage. There's no reason a correctly running LT1 should be getting 11 mpg, especially in something as light as a Z.

 

Out of curiosity, what transmission and rear gearing are you running?

[RTz]

As long as it passes your Calif, smog test I don't understand the big concern about MPG. You converted to a V8 for the power,speed 'wheel spins, bragin rights,and any other number of reasons I don't think MPG was on of the build concerns. IMO

 

11 to 14 MPG with a mostly stock LT1 indicates there is something wrong. It needs to be fixed. At minimum, he could be short a fair bit of power. Or worse, he could be shortening the life of his engine.

 

 

Out of curiosity, what transmission and rear gearing are you running?

 

Post #1...

 

It has the T-56 and the stock 3.36 rear end.

[lgoodson@pacbell.net]

93 T56 and 3.36 or so I believe. I think it has the stock rear end and 3.36 gears should give me better mileage rather than worse. I have ordered some GM O2 sensors. We'll see if that helps. Also I have sent an email to PCMs For Less to see if they did something. They say that they did nothing to cause the problem but without a Data Log,they can't say what's wrong but they say that they would think I have a bad sensor. Which one, they didn't say.

 

Can anyone tell me wh at a Data Log is and how do I get one?

[RTz]

Can anyone tell me wh at a Data Log is and how do I get one?

 

It means a sort of 'ticker tape' of running information. There are myriad of way's to go about it. Googling will fill you in.

 

I may be able to loan you a wideband O2 and logger, but it'll have to wait a bit. I'd like to see where you land with your other findings (O2's, vacuum verification, etc)

[lgoodson@pacbell.net]

RTz, I agree but where would you start. The car seems to have a lot of power but I have no experience with LT1's. I can easliy break the tires loose in 1st and 2nd.

I see no smoke indicating a rich condition. The car runs fine just doesn't get any economy.

 

What would you suggest that I check. I h ave new O2 sensors on the way.

Larry

[RTz]

RTz, I agree but where would you start.

 

Under cruise conditions, the WB02 should confirm you are in closed loop and running pretty close to 14.7:1. Medium acceleration need not be any richer than 14:1. Heavy acceleration need not be any richer than 13:1. That's where I'd start with respect to fueling.

[lgoodson@pacbell.net]

Forgive my ignorance but what is WBO2. I don't do fuel injection work so I have a big learning curve to overcome.

Thanks for the help

[Z48LT-1]

I found a web site with some clearly written stuff about the whole ECM/PCM tuning process, including datalogging: http://www.lt1pcmtuning.com/

 

I have no fiduciary interest nor any personal knowledge of their services but I thought the explanations were well-written and logically consistent.

 

You'll want to do a lot more research on the subject but google is your friend.

 

WBO2 is refers to 'wide band O2' monitor/sensor/whatever, used to reveal your air/fuel ratio by sensing 'excess' oxygen in the exhaust. The O2 sensors in your exhaust system apparently have the ability to cause the computer to make minor adjustments to the injector behavior, and are considered, therefor, to be 'narrow band' devices.

 

At least that's the way I think I understand things.

 

Alas, everything I think I know about this subject I 'learned' on the internet...

 

Cheers -- Gary

 

I have yet to see any problem, however complicated, which, when you looked at it in the right way, did not become still more complicated. -- Paul Anderson

[lgoodson@pacbell.net]

Thanks for that link. Looks like it will be a good one

[gvincent]

Yep I am running the PCV hose. I think I got it on EBAY. Can I assume you removed the EGR stuff too? Have you stuck a vacuum gauge on the engine yet? You live in California, how are you going to pass the smog laws with that open exhaust and no PCV? Nice thing about Georgia if the car is 25 YO, no smog requirements.

 

I just have a breather on each valve cover... Is this a no no?

I plugged the old PVC hose connection on the throttle body.

I kept the PVC valve and metal tube from the side of the intake manifold to the front of the engine block.

95 LT1

Thanks,

Greg

Edited December 11, 2009 by gvincent
add picture

[datsun723]

I just have a breather on each valve cover... Is this a no no?

I plugged the old PVC hose connection on the throttle body.

I kept the PVC valve and metal tube from the side of the intake manifold to the front of the engine block.

95 LT1

Thanks,

Greg

 

Norton, Ma?? Nice! I used to live there as a kid!

 

Sorry for the thread jack

[deja]

Bad? I don't know but I've always been told pulling fumes from the engine is a good thing and a breather doesn't do as good of job.

 

 

I just have a breather on each valve cover... Is this a no no?

I plugged the old PVC hose connection on the throttle body.

I kept the PVC valve and metal tube from the side of the intake manifold to the front of the engine block.

95 LT1

Thanks,

Greg

[wheelman]

What fuel pump and pressure regulator are you running?

When I first installed my LT1 I ran a Walbro 255lph pump with the stock regulator. I'm not certain of it but I think the pump produced too much flow for the regulator to handle which increased the pressure in the rails. This caused my engine to run rich.

I solved the problem by indirectly by replacing my stock (modified) Datsun tank with a 2001 Camaro tank that has an intank pump. This pump flows a lot less than the Walbro did consequently the stock pressure regulator can handle it.

If you're running a Walbro pump you should check your fuel pressure as well as everything else thats been suggested.

If the pressure is higher than it should be you will have to replace the stock regulator or the pump.

[deja]

You might be on to something. In an earlier post he said he was running a a fuel pump from a 81 280ZX turbo that produced 66 psi, way too high for the stock regulator. I don't know if he addressed that or not.

 

What fuel pump and pressure regulator are you running?

When I first installed my LT1 I ran a Walbro 255lph pump with the stock regulator. I'm not certain of it but I think the pump produced too much flow for the regulator to handle which increased the pressure in the rails. This caused my engine to run rich.

I solved the problem by indirectly by replacing my stock (modified) Datsun tank with a 2001 Camaro tank that has an intank pump. This pump flows a lot less than the Walbro did consequently the stock pressure regulator can handle it.

If you're running a Walbro pump you should check your fuel pressure as well as everything else thats been suggested.

If the pressure is higher than it should be you will have to replace the stock regulator or the pump.

[Inferno 08]

Bad? I don't know but I've always been told pulling fumes from the engine is a good thing and a breather doesn't do as good of job.

 

Not having the stock PCV system shouldn't do this to your mileage. The point of a PCV system is to evacuate fumes from the crankcase. Breathers will do the job, but the stock PCV system will work a little better. The downside to the stock system, however, is that it routes those fumes (along with oil vapor) back into your intake, which isn't exactly a plus for performance applications.