RE: Fuel Mix Computer

From: Bernd D. Ratsch (bernd@dodgetrucks.org)
Date: Wed Mar 19 2008 - 00:21:12 EDT


It really depends on several items first:

(1) What's you're A/F at right now?
(2) What are the fuel adaptives at right now?
(3) What are the CO%, CO2%, HC%, and NOx% at right now?

Without those...it's too hard to say in an email on what you really need.
Without the actual readings, it's only speculation.

If you do decide on using an aftermarket fuel control system (piggy back in
this case), definitely think about using one step up on the injectors and
underdrive them. The factory injectors are run at a slightly higher
pressure than actual rating pressure so they're already being overdriven (to
a small extent).

- Bernd

-----Original Message-----
From: Jamie Calder [mailto:JCalder3@cfl.rr.com]
Sent: Tuesday, March 18, 2008 9:37 PM
To: dakota-truck@dakota-truck.net
Subject: Re: DML: Fuel Mix Computer

Marty did the porting (yes I've heard good and bad things about his porting)

and I believe he sold me 10:1 pistons (8 years ago now).
How does the AEM compare to the Apexi?
You would recommend the 24# injectors no matter which piggyback is used?

--------------------------------------------------
From: "Bernd D. Ratsch" <bernd@dodgetrucks.org>
Sent: Tuesday, March 18, 2008 9:42 PM
To: <dakota-truck@dakota-truck.net>
Subject: RE: DML: Fuel Mix Computer

>
> I'm familiar with that cam - it's the same one in my new 5.9L and the same
> one I use on other builds I've done at the dealership. It also depends on
> compression ratio and how much porting was done to the heads (flow
> characteristics). Yes, it will run rich at idle due to the overlap - no
> way
> around that unless you either custom program the PCM or run a fuel
> "tuning"
> add-on.
>
> Best combination I've found (yes, on a dealership Dyno and fuel curve
> tuning) - AEM Piggy Back, 24# injectors, and an effective compression
> ratio
> right close to 10:1. It's much easier to take away fuel% with larger
> injectors than with smaller ones. The APEXi will help out quite a bit
> though - it took care of my rich condition at idle on the old V6 (10.5:1,
> .540" lift, 220 duration, and a lot of porting and CC work to the
> heads)...even passed a sniffer test on our emissions machine (without the
> cat - we were curious and had to check).
>
> - Bernd
>
> -----Original Message-----
> From: Jamie Calder [mailto:JCalder3@cfl.rr.com]
> Sent: Tuesday, March 18, 2008 8:08 PM
> To: dakota-truck@dakota-truck.net
> Subject: Re: DML: Fuel Mix Computer
>
>
> Ray,
> It's a '93 318, 30 over, Comp Cam 604 specs:
>
http://www.compcams.com/Technical/Search/CamDetails.asp?PartNumber=20-604-8
> 4bbl M1, ported throttle body, FMS 19# injectors, ported heads, MP PCM,
> 1.7:1 RR's...
> Isn't it that cam that causes it to run rich at idle? It use to have a
> couple hi flow cats but they got ruined within 1000 miles.
> I'd like to have it run with the proper air/fuel mix. My brother in NJ
> will
>
> be buying it from me and it will need to have cats installed. Sounds like

> a
>
> piggyback fuel controller is the answer but I'm open to any suggestions.
> Thanks for any help,
> James
>
>



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