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Terrible MPG...?
http://classiccamaroclub.mfatw.com/viewtopic.php?f=4&t=4209		 Page 1 of 3
Author:  The Seer [Tue Nov 25, 2014 1:59 pm ]
Post subject:  Terrible MPG...?
I've worked out I'm paying 40-50 quid in fuel to cover circa 40 miles...something ain't right. I'm new to the car and as such I'm driving it normally, not quickly or spiritedly.

Here's the spec:

ZZ4 crate engine, trick flow ally heads held down with an arp bolt set on top of ultra thin metal head gaskets raising compression to 10.5:1, trick flow cam, trick flow hardened push rods, Weiand stealth warrior dual plane inlet with a 750DP Holley carb fed by a 110gph Holley fuel pump, upgraded Davies unified ignition HEI distributor, new rotor arm, new leads and new plugs, full length headers into 3 inch collectors with exhaust dumps, power now estimated @ 460+ bhp all kept cool by a 3 core ally be-cool rad and steel flexi fan with billet reduction pulley, also new battery and alternator just fitted

Drivetrain
Rebuilt TH350 with B&M 3200 stall converter, shift kit, external cooler, and quick silver shifter
Rear end is a rebuilt 10 bolt posi with 3.90 gears

I'm getting 4-6 mpg which I figure is too low, but then again considering the spec and gearing is it?? I will say a fair amount of town driving has been involved, and I have noticed at 70 mph the engine is around 3500 RPM.

Any ideas? Thanks :)
Author:  chevy-stu [Tue Nov 25, 2014 4:09 pm ]
Post subject:  Re: Terrible MPG...?
with that Carb, that gearing with a 3 speed, i'd be suprised if you crept much into the teens with mixed driving, but I'd have thought you'd get a bit better than 4 - 6 mpg..
Could be on choke all the time.. ?
Author:  The Seer [Tue Nov 25, 2014 4:25 pm ]
Post subject:  Re: Terrible MPG...?
Quote:
with that Carb, that gearing with a 3 speed, i'd be suprised if you crept much into the teens with mixed driving, but I'd have thought you'd get a bit better than 4 - 6 mpg..
Could be on choke all the time.. ?
Err...there's no choke. I warm the engine for a few minutes at steady RPM then let her idle.

I wasn't expecting any more than 10-11 mpg either but 4-6 is very disappointing. Surely there's gotta be something wrong??
Author:  The Seer [Tue Nov 25, 2014 4:26 pm ]
Post subject:  Re: Terrible MPG...?
Quote:
with that Carb, that gearing with a 3 speed, i'd be suprised if you crept much into the teens with mixed driving, but I'd have thought you'd get a bit better than 4 - 6 mpg..
Could be on choke all the time.. ?
Err...there's no choke. I warm the engine for a few minutes at steady RPM then let her idle.

I wasn't expecting any more than 10-11 mpg either but 4-6 is very disappointing. Surely there's gotta be something wrong??
Author:  78 Camaro [Tue Nov 25, 2014 4:52 pm ]
Post subject:  Re: Terrible MPG...?
That does seem low... has the engine been tuned? As there has been a lot modified i wonder if all of the components are working to compliment eachother?
Author:  The Seer [Tue Nov 25, 2014 5:07 pm ]
Post subject:  Re: Terrible MPG...?
Quote:
That does seem low... has the engine been tuned? As there has been a lot modified i wonder if all of the components are working to compliment eachother?
Personally if it has been tuned, it hasn't been tuned correctly. She runs fine though, I've not felt and flat spots, no bad idle, engine picks up through the revs just fine.

To answer your question, no I don't think it has been tunedby someone in the trade. There's no record of it, the chap who owned it probably tuned it himself.

What's exactly involved in tuning, can you shed some light on this?? Thanks :)
Author:  sportsroof [Tue Nov 25, 2014 6:26 pm ]
Post subject:  Re: Terrible MPG...?
First things that jump out at me are the loose converter and silly gears. These will always fight you if you want any economy. Engine tune is also a possible as already mentioned.
There are a few things you can do to improve economy, sometimes dramatically but your drivetrain will always be an issue. Personally I like manual gearboxes (no slippage) and sensible axle gears. When tuned properly you can then have economy and performance , my own 351 racer gets about 20mpg on a run, can do 12 second quarters and 140 odd topend (RPM limited) with 3.50 rear. HTH
Cheers, Martin
Author:  The Seer [Tue Nov 25, 2014 8:07 pm ]
Post subject:  Re: Terrible MPG...?
Quote:
First things that jump out at me are the loose converter and silly gears. These will always fight you if you want any economy. Engine tune is also a possible as already mentioned.
There are a few things you can do to improve economy, sometimes dramatically but your drivetrain will always be an issue. Personally I like manual gearboxes (no slippage) and sensible axle gears. When tuned properly you can then have economy and performance , my own 351 racer gets about 20mpg on a run, can do 12 second quarters and 140 odd topend (RPM limited) with 3.50 rear. HTH
Cheers, Martin
I suspected the gearing wouldn't help. The guys that owned her before me had Santapod in mind when the modifications were made. I do like the performance and acceleration the car has and I'd be loathed to change that.

I'd be quite happy with an average of 10-11 mpg but 4-6 is ridiculous. What do you mean by loose converter and how may this effect the mpg? Thanks :)
Author:  3rdGenmalc [Tue Nov 25, 2014 8:49 pm ]
Post subject:  Re: Terrible MPG...?
"We can never select the one result we want to the exclusion of all others" David Pye.

If your running a car initially designed to run on a drag strip you are, being subtle, screwed. :lolno:

You need different rear gears and swap in a TH700R4.

When I did all the mods to my car I never expected economy, I wanted the rush of acceleration,
and luckily I don´t have to use the car that often.

The 1978 Camaro I had when I lived in Germany was a bar steward of a gas guzzler and only 5.0 motor.
Author:  The Seer [Tue Nov 25, 2014 10:21 pm ]
Post subject:  Re: Terrible MPG...?
Quote:
"We can never select the one result we want to the exclusion of all others" David Pye.

If your running a car initially designed to run on a drag strip you are, being subtle, screwed. :lolno:

You need different rear gears and swap in a TH700R4.

When I did all the mods to my car I never expected economy, I wanted the rush of acceleration,
and luckily I don´t have to use the car that often.

The 1978 Camaro I had when I lived in Germany was a bar steward of a gas guzzler and only 5.0 motor.
The gearing isn't fantastically low, admittedly it's not gonna help just as the town driving won't either.

However I'm still yet to properly open the throttle. I can't believe with its spec and gearing an average of 4-6 mpg is present.
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