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Bigger engine = more fuel?

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Old Apr 18, 2014 | 01:33 PM
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Bigger engine = more fuel?

Hey guys,

First off, I know I need a wide-band. And I am going to buy one. But I'm just curious here. When I had my H/C/I L98, at WOT my narrow-band reading was right around 900mv. Which I am told was a decent ball park number.

Now my 427 is broken in, and for now is running the same chip that was in my H/C/I L98. At WOT, my narrow-band is reading 995+ mv. Wouldn't you think the much larger engine would need more fuel at WOT and not less? The fuel system, injectors, AFPR..etc all are the same.

Last edited by IROCThe5.7L; Apr 18, 2014 at 01:37 PM.
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Old Apr 18, 2014 | 01:37 PM
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Car: 1983 Z28
Engine: 385 Fastburn
Transmission: T-5
Axle/Gears: BorgWarner 9-bolt posi, 3.27 gears
Re: Bigger engine = more fuel?

Originally Posted by IROCThe5.7L
Wouldn't you think the much larger engine would need more fuel at WOT and not less?
That would make sense, unless it's being starved for some reason.
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Old Apr 18, 2014 | 01:42 PM
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Engine: 427 SBC
Transmission: ProBuilt 700R4
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Re: Bigger engine = more fuel?

Originally Posted by RedLeader289
That would make sense, unless it's being starved for some reason.
You'd think so. It still has the stock throttle body. I'm sure that's probably not supplying enough air. I have a 58mm throttle body waiting to go on though.
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Old Apr 18, 2014 | 01:46 PM
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From: Louisville, KY
Car: 1983 Z28
Engine: 385 Fastburn
Transmission: T-5
Axle/Gears: BorgWarner 9-bolt posi, 3.27 gears
Re: Bigger engine = more fuel?

Curious. TB's aren't my forte, but I bet that'll wake her up
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Old Apr 18, 2014 | 03:33 PM
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Re: Bigger engine = more fuel?

Originally Posted by IROCThe5.7L
Hey guys,

First off, I know I need a wide-band. And I am going to buy one. But I'm just curious here. When I had my H/C/I L98, at WOT my narrow-band reading was right around 900mv. Which I am told was a decent ball park number.

Now my 427 is broken in, and for now is running the same chip that was in my H/C/I L98. At WOT, my narrow-band is reading 995+ mv. Wouldn't you think the much larger engine would need more fuel at WOT and not less? The fuel system, injectors, AFPR..etc all are the same.
im surprised a mod is asking a question! but no one knows everything!! lol im actually glad that the Mods & admins actually mingle in with us members its nice
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Old Apr 18, 2014 | 09:04 PM
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Car: 84 Trans Am, 84 Fiero, 86 944
Engine: 5.0, 2.5, 2.5
Transmission: 5spd
Re: Bigger engine = more fuel?

is it still tpi?
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Old Apr 19, 2014 | 10:25 AM
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From: Camden, MI
Car: 1985 IROC-Z28
Engine: LB9
Transmission: 700R4
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Re: Bigger engine = more fuel?

which ECM/mask are you running?
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Old Apr 19, 2014 | 10:42 AM
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Re: Bigger engine = more fuel?

Honestly, with how inaccurate the narrowbands are I would not even use it.


Make sure you get a wideband that has a narrowband output and hook that up to your stock ecm input so you can just use one o2 sensor for everything.

For now..... kick it some and then pull plugs. See how they look
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Old Apr 19, 2014 | 11:24 AM
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Car: 1988 IROC-Z
Engine: 427 SBC
Transmission: ProBuilt 700R4
Axle/Gears: Moser 12 Bolt / 3.73 TrueTrac
Re: Bigger engine = more fuel?

Sorry should have been more detailed. HSR intake on both engines. And 165/$32b. Nuff, that sounds like a good idea. Then I don't have to drill and install another O2 bung.
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Old Apr 19, 2014 | 08:58 PM
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Re: Bigger engine = more fuel?

I'm all about easy!
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Old Apr 19, 2014 | 09:20 PM
  #11  
IROCThe5.7L's Avatar
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Engine: 427 SBC
Transmission: ProBuilt 700R4
Axle/Gears: Moser 12 Bolt / 3.73 TrueTrac
Re: Bigger engine = more fuel?

Originally Posted by NufNuffZ28
I'm all about easy!
Is that O2 sensor you speak of heated also?
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Old Apr 19, 2014 | 09:26 PM
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Engine: 357 Single plane and a Ysi vortech
Transmission: T56
Axle/Gears: 3.50 9"
Re: Bigger engine = more fuel?

Yes. all widebands are heated.

I got the AEM setup and it has the narrow output.

We also found a cheap(60ish) replacement sensor if yours ever fails. Much easier than the $149 AEM replacement and its the same Bosch sensor!
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Old Apr 20, 2014 | 02:05 PM
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IROCThe5.7L's Avatar
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Car: 1988 IROC-Z
Engine: 427 SBC
Transmission: ProBuilt 700R4
Axle/Gears: Moser 12 Bolt / 3.73 TrueTrac
Re: Bigger engine = more fuel?

Jackpot! Thanks!
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Old Apr 22, 2014 | 01:43 PM
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Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: Bigger engine = more fuel?

As said use a wideband to verify but although it makes sense more engine more hp would be more fuel it may not be the case due to efficiency...

A more efficient engine will make same power with less overall fuel flow. Brake specific fuel consumption. Theres a chance improved dynamics of the intake side of the system are creating a situation where less commanded fuel is required.
I have seen a heads cam L98 run on a ARAP bin that required less fuel than what was listed for a stock motor yet it made 100 hp more. Narrow band also never really read right
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Old Apr 22, 2014 | 04:59 PM
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Re: Bigger engine = more fuel?

I would think the duty cycle of the injectors would be something to use as a comparison. A/F could be similar but if the duty cycle on one datalog is 80% and the other log is at 90% more fuel is being used to achieve the same 12.50/1 A/F.
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