Garbage gas mileage, 10mpg

[5.0 HOtrain]

I think im gonna try and solve this problem by doing a new engine 10.5:1 347 with ported TW heads,

You gonna stick with the Too F-n Slow heads What are you thinking, look at my crappy #'s with box stock TFS heads

On a side note, glad to see you are going for it, good luck and make sure to keep up updated.
mike.

 

[Grn92LX]

Mike, the new engine is gonna cost an arm, leg and a left and right nut but I think im gonna say F it and do it! I'm hoping to see over 400rwhp. I think its gonna be a killer street car combo!!

I still gotta figure out WTF is up with my gas mileage?!!?

 

[mat50ho]

green 93 lx

What has been the air temp you have been driving in lately ?

What is the normal operating temp of your motor ?

Have you checked all the basics plugs, wire, timeing etc etc

In my opinion I would have the car tuned before i buy a new maf. The cost would be close and the tune would be more benificial.

I picked up 2 mpg with my current tune.

 

[TrickStang37]

I used to get 13ish city drivin and 22+ mostly highway with my mods. also, i know it was way back like on page 3 or somethin, but I once dropped one of my o2 sensors in a bucket of coolant (dont ask how) and the sensor worked fine, so i doubt yours are bad from that when you blew your headgasket. Im definetely thinkin its the changed resistance to the o2's though.

as for the big deal with the 30's, Im not buying the 225hp = 19lbs chart you guys came up with. I mean, LT1's came with 24's and stock they push out 305++ so im sure the 24's, for most people, are enough when runnin 350 hp or less. What do LS1's come with? And yes I do know they run different fuel pressure as well and the rating they have. But I would also think that an automaker would rather over inject the car than to under inject it and have it run lean.

whatever, every one has their own opinion. good luck on findin out the problem or the new motor, whichever comes first. or both.

 

[5spd GT]

as for the big deal with the 30's, Im not buying the 225hp = 19lbs chart you guys came up with. I mean, LT1's came with 24's and stock they push out 305++ so im sure the 24's, for most people, are enough when runnin 350 hp or less. What do LS1's come with? And yes I do know they run different fuel pressure as well and the rating they have. But I would also think that an automaker would rather over inject the car than to under inject it and have it run lean.

I'm not exactly sure who your reffering to on this...

But the lt1's have 275 (93-95)- 285hp (96-97)...not the ls1 rating of 305hp (which is underated)...

The ls1's come with 28lb injectors...I believe...

The chart doesn't lie on what would be optimum if the ECU/MAF/Injectors/Fuel Pump/Fuel Pressure where to be optimized in stock trim as they are by Ford...

225hp = 19lb injectors (stock 87-93 5.0)
265hp = 24lb injectors (actual output of 93 Cobra)
300hp = 30 lb injector (if you follow the same pattern)...
330hp = 36lb injector? (average AFR/FTI combo)

These are bhp numbers not rwhp numbers...

Now again...this is not with a "home tune" with these injectors to be optimum...this is as if all the above mentioned "controls" (ECU, injectors, etc) where all installed as one and meant to work together as one as they come out of the factory...

So 30lb is not to much...it might be "slightly" argueable for someone that does a "hometune" to give that out...but if you look at the numbers of the out put of the cars you will see where I'm coming from...

I run 30lb on mine with no problem... Besides an everynow and then idle surge but then again my computer is meant for the 19lb injector flow ratings/duty cycles and all that mess...

 

[TrickStang37]

the LT1 could come from the factory with 305 with all the options and it still ran the same injectors. And the LS1 is underrated, closer to 345 runnin 28#'s. So, according to your layout, your sayin 42# injectors would be optimal for 360hp N/A?!

 

[5spd GT]

the LT1 could come from the factory with 305 with all the options and it still ran the same injectors. And the LS1 is underrated, closer to 345 runnin 28#'s. So, according to your layout, your sayin 42# injectors would be optimal for 360hp N/A?!

No the ls1 dynos 290-300rwhp...so that is around 330bhp...not 345bhp (the rating of the ls1 vette)...

The lt1 SS had 305 hp...but not the "regular" lt1...specify next time

Well the ls1 computer/engine is different than the Ford computer/engine...even though the pushrod engines are very similar there are difference in cams/head flow design/ etc...

Don't need to compare an ls1/injector to 5.0/injector question...

Just to show you the differences in the motor design and what their certain parts can adhere to certain mods...you put a cam in a stock 5.0 and you might get 10rwhp...you put one (in the already 290rwhp) ls1 you can gain 40rwhp...totally different cars in that respect...you put longtubes on an ls1 and gain much more power than on a 5.0...

Yes if you follow the chart...it only seems obvious what would be next...again this is not just slapping it on a "wild" h/c/i package with 360bhp (42lb injector) but this is with all the matching components (as from the factory)...computer/fuel pump/pressure/etc...all needs to be optimized...

No I would not put 36lb or bigger (even though the chart shows it) on my h/c/i car...because I have the stock computer/ECU...

Again this is from the factory...

 

[TrickStang37]

its not rare for an LS1 Fbody to dyno up to 315ish rwhp, which would put it up there.

and your focusing on the wrong part of the discussion. I know the how the cars react to mods, were not talkin about reaction to mods. were talkin about fuel needed for a certain hp level on a V8. and most people would agree that even with the 19#s on the stock motor, and even modded, the 5.0 would run slightly rich and ran best with a lower fuel pressure, effectively lowering the fuel needed and at the same time gave a couple more hidden hp back. And most fbody (LS1) crowd dont upgrade the injectors till they're runnin about 350rwhp or more. And I even think the LT4 came with 24#'s as well.

 

[5spd GT]

its not rare for an LS1 Fbody to dyno up to 315ish rwhp, which would put it up there.

and your focusing on the wrong part of the discussion. I know the how the cars react to mods, were not talkin about reaction to mods. were talkin about fuel needed for a certain hp level on a V8. and most people would agree that even with the 19#s on the stock motor, and even modded, the 5.0 would run slightly rich and ran best with a lower fuel pressure, effectively lowering the fuel needed and at the same time gave a couple more hidden hp back. And most fbody (LS1) crowd dont upgrade the injectors till they're runnin about 350rwhp or more. And I even think the LT4 came with 24#'s as well.

Yes it is rare...I have seen them dyno those numbers...but the average is 290rwhp bone stock...depending on 6spd/4l60E....it can go up or down...

No...you took it out of context...I was going against you comparing the ls1/injector to the 5.0/injector ratio...you were saying they make this much power but run this injector...etc...etc...and I was showing you examples (different parts of the engine and its management) on how it proves the engines are different in that respect...

A "certain" injector is not proportional to a certain power level out of just any v8...that is why I compared "my chart" as Ford numbers...engines are different and therefore need different fuel "pulses" and other supporting fuel mods to maintain the tune from the factory...not based just on the power they are making...

 

[5spd GT]

Oh and the LT4 = 28lb injectors @ 43.5psi...not 24lbs...

 

[Grn92LX]

Aight, I did some more testing and fiddling around. My cars idle absolutely blows on a dead cold start, I have to keep my foot on the gas or it'll stall. What I tried was, taking off the remote optimizer and starting it up and it didnt stall. It ran better, but it idled low and a little sluggish and a little surging. I am gonna keep the optimizer off and see how my gas mileage does.

I also tried lowering my fuel pressure to help the cold start problem and that didnt do anything.

I also probed wires C and D on the maf harness and found something pretty interesting. With my electric fan OFF I got about .72v at idle on wires C and D and 14.00v by probing the power wires. Now with my electric fan ON I got under .5v on wires C and D and 12.00v on the power wires. Now heres some theory, my last tank of gas I got crappy mileage (8mpg) and that was with the hotter running stat BUT I also had the electric fan on most of the time when I was driving. My last tank with the colder running stat I got about 13mpg but rarely used the fan. You would think the hotter running car would get better gas mileage so i'm wondering if keeping the fan on most of the time making my maf voltage lower is screwing my gas mileage?

Anyone else ever probe wires C and D on the maf with and w/o electric fans?

Lower voltage means the car runs leaner. Is it possible that the eec saw that lean condition and added in a lot of fuel, thus the bad gas mileage? Im lost.

Mike

 

[TrickStang37]

maybe, thats a good theory i think. what alternator are you runnin?

 

[TrickStang37]

and my car has ALWAYS had bad cold starts, even when i was just about stock. Actually, now it cold starts better than when it was stock.

Also, maybe thats not the only sensor thats being affected voltage wise when the fan is on.

 

[Grn92LX]

I use a 130a alternator and I have the 4g wire and fuse kit. I'll see how it starts up tomorrow now that I removed the optomizer.

 

[Michael Yount]

Grn92 - was it ever getting better gas mileage with your current setup?

 

[evn_05]

My car is pretty well stock (mods in sig) and all I really get is city mileage, and it sucks. I usually get about 12 mpg. I took a highway trip the other day and I think I got around 18 mpg or so. Anyway I just had a total brain fart. Last summer when we put in my autometer gauges (WATER TEMP & oil pressure) we took out the stock sending unit and left it out with the wire disconnected.

I had never thought of this until just now. Would this be a culprit for my bad mileage. Or does the computer even use the water temp in the calculations. I dont think it does but I dont remeber. Does anybody have the answer to this???

 

[TrickStang37]

im pretty sure the computer doesn't read the temp and oil pressure from those sending units.

 

[TrickStang37]

and my milage is 12 city /22+ highway at about 3000 rpm.

Off topic but hey Michael, or anyone else who may know, does a car get better milage closer to peak tq or lower in the rpm range? I would think lower in the rpm range since air + fuel = power but i dont know.

 

[Michael Yount]

The computer reads engine coolant temperature from the ECT sensor. It screws into one of the black metal heater hose tubes that run across the passenger side lower intake. The gauge sending unit, which is on the other side of the intake, and screws directly into the manifold, is just for the gauge. Leaving the wire off of it should have no impact on fuel mileage.

Have you pulled the diagnostic codes out of the computer? Is it giving you a check engine light? Probably the most common cause of poor gas mileage is driving style and heavy stop and go traffic. The second most common cause is bad/worn out O2 sensors.

 

[Grn92LX]

Grn92 - was it ever getting better gas mileage with your current setup?

When I added the 30lb injectors, my speedo was not working so I never calculated the mileage. With my current set up and 24lb injectors with the lean condition I remember getting about 16mpg around town.

I'll see how mileage is now that the optomizer is off the car.

What do you think about the electric fan making my maf voltage lower?