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Discussion Starter #1
On a new engine is gas milage effected for a while while it breaks in? Since I have gotten the new engine in my milage is horrible. 200 miles to a tank if Im lucky. Im at 185 now and I need to fill it up again.

I understand its a performance build and that the days of 400 miles to a tank are gone but this just sucks. I expected at least 250-275, thats were I was before the new heads/block. Even in normal driving conditions I can see the gauge dropping. 35 bucks for a short weekend is rediculous.

Does this sound right? The engine is barely broken in..has about 500 miles on it..perhaps it will get better with time?

My build is as follows:

Renegade block/Heads
VT blower cams
AED SC
SCT tune
42# injectors
255 lphp
90mm LMAF
2800 PI stall
TL 3.73's
Kooks
ART exhaust

What do you guys think?
 

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I would say you will get a little better mileage as she breaks in.
I say this just because as the motor breaks in friction will reduce.

But yeah a modded motor usually uses more fuel = less mileage.
I have some 42# squirters and yeah I noticed a decrease.

Steve 4.6L
 

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Uhh

I was getting 130 miles to tank in my RX7 if it makes you feel any better! :p

- Pelezo
 

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Discussion Starter #5
I might want to talk to Lonnie. Wonder what he would charge to mess with those settings only.....

Anyone have his email address?
 

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Gee! I just got 16.2 on the last tankful..... I felt pretty darned good about that, as 14-15 has been about average for me... staying away from boost and WOT would make things better, but we all want to have more power and use it... I will replace my 02 sensors next to see about another couple tenths of a mile per gallon, then , of course make a few more changes looking for , .... MORE POWER! :D :D
 

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The Pete rutinely gets 15-16 going to and from work every day (strictly city driving), and 24-25 on the highway. Typically, I fill up at 235 miles and take on 15 gallons...having a heavy foot is an expensive habit.

Pete
 

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42lb injectors are NOT efficient at lower flow rates. So there's part of your problem there. But you know what I see as #1? The fact that you have over $10k under your hood but haven't pony'd up $800 for the ability to tune it yourself and datalog the car to see what it's doing and why. Get the SCT PRP and be done with it. Then when you have a questoin, you post the data from the car, somebody who knows cars will tell you what to adjust, YOU adjust it and see if it helps. :D You'll thank me for this public service announcement later.
 

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Discussion Starter #11
Sir William said:
42lb injectors are NOT efficient at lower flow rates. So there's part of your problem there. But you know what I see as #1? The fact that you have over $10k under your hood but haven't pony'd up $800 for the ability to tune it yourself and datalog the car to see what it's doing and why. Get the SCT PRP and be done with it. Then when you have a questoin, you post the data from the car, somebody who knows cars will tell you what to adjust, YOU adjust it and see if it helps. :D You'll thank me for this public service announcement later.
It is next on the list. You have to cut me a little slack though...the car just got out of the garage a month ago after a 2 year hiatus. :) Im still trying to get all of the small bugs worked out.

It will be mine within the next year. Even if I have to stop driving the car so I can afford it. :)
 

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hey AEDM8

i just drove my motor today for the first time. Im 100 miles into it. Im having the exact same problem... but about twice as bad. I got from 7 - 8.5mpg on the highway driving easy. Shes running totally sluggish. Ive done the sct flash etc also. But my kit came with the 30lbs injectors.

I have code logger so im going to see what I can find. The problem is I have no idea what to look for let alone have a base line for anything.

If you found anything wrong or have fixed your problem please let me know.

GOOD LUCK!!!
 

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Discussion Starter #13
Sorry to hear about your problems, glad to hear you have the beast running again though. :)

My car has been parked for the last two weeks. I cant afford to drive it as much as I used to so its been sitting. I plan on pulling it out this Friday and giving everything a once over. Probably going to borrow my buddies datalogging equiptment and have that hooked up while we cruise the strip. (Back to the 50's car show, should be a blast....)

In the back of my mind Im convinced it has something to do with the tune. Ill let you know if I figure anything out. Let me know if you get any leads.
 

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yep sure will. im confident i will find the problem... its just a process of elimination... you know whats funny... I dont know if you remember but my original thread i posted when i had hooked up the MAF wires wrong etc. and I reported that after fixing it my boost was crazy, my needle would climb and shake like crazy, and had no power etc. first suggestion was bad ring lands, i then checked for compression and it was low and my piston rings were stuck etc.

Well when I finally put the new motor in and drove her yesturday, i nearly got diaria!!! SAME FRICKIN problem with my bad power and crazy needle etc. I said NO WAY... :eek:

it finally dawned on me that it had to be a flow restriction problem... drove her straight to the muffler shop and said take these CATS OUT!!! The first cat was pretty clogged.... the second cat was fried and IN PIECES.... totally torn apart inside. Fired her up with just the headers... wala... problem solved (and sounded like a car from Monster Garage)

Put the straight pipes on and totally fixed.

Conclution:

Bad wired MAF caused VERY lean condition, fried my rings closed, and the heat blew my CAT to shreads.

So now im starting to wonder if my problem now with my rich or bad mileage condition is originating from the MAF as it could have been damaged from the past bad wiring.

Ill let you know when I find the problem.....

Hope you find the problem also.....

I know what you mean... i almost used up an entire tank of gas on 105 miles yesturday!!!
 

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let me just say one thing to end your gas problems ... buy a 4 cyl. i drive my T-bird when it's nice or if im going somewhere close to home, other than that, i bust out the VW Jetta .. that cures my problem for gas prices.
 

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properly set up you should get OK mileage with 42 lbrs.

I was getting 14-17 depending on how heavy my foot was around town and
22 mpg on the highway.

cams and all will change that.

BTW, with the blower setup, 10-12 around town, hard to keep foot out of it.

rm
 

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I actually reached 16mpg (255 miles/15.8 gallons) for the first time since I got 3.73's, thanks to Lonnie. Prior to SCT, ~15mpg (240 miles before fillup) was typical. Before the gears, I remember I could top 300 miles per tank fairly easily if I wasn't too heavy on the throttle for the whole tankful. My problem is I like to give the car a lot of gas at lower rpm's, then backing off to let it shift, repeat...makes it sound like a standard and I'm not trying too hard to accelerate. :)
 

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I still say it was the tune. My 19lbs are only getting me 14mpg in town and 19 on the interstate with the cruise set at 75mph. For the year I ran the car before the tune with all the exact same equipment got 20mpg in town and 27mpg on the hwy. Hence the money back from SCT and going to Hi Tech. Not including the shifting issues.

SCT not ranking high on my list at all.

Thus, let the flaming begin.
 
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