TWM/Accel Gen 7+ DFI tuning.

[Mike]

Does anyone know of an Accel DFI specialist in the Mid West/St. Louis area familiar with TWM and Ford motors? I'm about ready to pull everything off and run a carburetor. The car runs rich, the plugs are always black and sooty, and when I lean it out, it won't run. It's only happy at wide open throttle (350/350 RWHP/TQ). Low and partial throttle A/F mix. are too rich.
Any names/phone numbers/TWM or Accel Gen7 experience out there? Working VE/A/F/Spark maps? Getting seriously frustrated with this.
Thanks,
Mike /ubbthreads/images/graemlins/mad.gif

 

Mike, I would suggest you find someone in your area with a tuning dyno ie: 1750 mustang,or dynopack.Anyone who has invested the amount of money these machines cost should know what they are doing. A few hours of what we call step tuning should solve your problems. Check the websites of these dyno manufactures for dyno's near you. I have found TWM to make exelent pieces, have never worked with accel, too drag race orientated for my type of customer.Best of luck
Ron

 

[Paul Thompson 'Hooligan']

Hi Mike,

What size injectors are you running (cc/min or lbs/hr)? - what fuel pump?, what's the rail pressure (Psi)? and does the regulator have a vacuum connection from the manifold?

Finally, are the injectors batch fired (wired in pairs) or sequential (each wired alone and req's cam posn)?

We ran an early Accel Dfi system on Roy's 40 for a while and it worked well so don't lose heart and fall back to carbs - 'old technology', once you have it sorted it'll be great and knowing how to sort it will make any future plans you may have all the easier to achieve... /ubbthreads/images/graemlins/smile.gif

 

[Mike]

Hi, Paul. Been to 'Brands Hatch'lately, or do you cruise around the beaches at Brighton? (4 yrs. at RAF Lakenheath).
Re. the DFI pain, I've gone through both the earkly gen 6 (Alpha N modes) as well as this new Gen 7+ (MAP mode).
I run 36lb low impedance injectors (the early 30lb injectors were pushing 90+% duty cycle), two Holley fuel pumps at 45psi, and sequential firing. I do NOT have a manifold referenced fuel pressure regulator.
I can't find a 'professional' tuner in the area. Over 10 years, this thing has always had black sooty plugs. Idle and partial throttle tuning is where the mixture just doesn't seem to want to lean out. WOT is fine.
Short of trucking the car to another state for tuning, I'm at something of a loss.

 

[Ron Earp]

Mike, that is a shame to have a nice car that won't run well for that long. Is there no chassis dyno near you? I've not used that system before. Does it use a MAP system and a lookup table to figure out everything? How is the lookup table generated? Any chance of putting a wide band O2 in the system? Even if it doesn't work with the system, a wide band (about $450 with gauge) could show you where you have issues so you could alter the programming, which I assume you can.

 

[Paul Thompson 'Hooligan']

Hi Mike -

Just downloaded the pdf manual from Accel site - very interesting as they still use a version of Calmap albeit a far more extensive version. I liked the early version of Calmap that I used on Roy's initial ECU and this version seems very good indeed, plus the documentation enclosed is very helpful.

Anyway, reading the blurb - I notice they specify (1.4.2) "A vacuum line must be attached between the fuel pressure regulator and the side of the intake plenum"

This would enable the fuel pressure to be raised for boosted applications such as turbo or supercharging, Plus, more importantly, will lower the fuel pressure from 45psi to perhaps 32-33psi at idle where there is a substantial vacuum available on the plenum. This lowered fuel pressure effectively extends the controllable range of the injectors because there is a minimum time that the injector will correctly operate. If this 'pulse' gets too small, the injector will fail to operate as designed and fuelling become erratic. So, by lowering the fuel pressure 'at idle' the ecu can use a larger pulse width (bigger numbers) and therefore better control the fuelling.

IF and it is a big IF, IF your ECU was initially programmed with this vacuum connection expected. Then without it, the fuel pressure would be higher than expected and hence more fuel would flow than required = sooty rich mixture.

Don't get me wrong, I'm not saying ALL engines require this connection, (We don't on Roy's!) BUT the fuel maps do look very different with and without it and in general, I believe it is a useful arrangement.

Connecting one would be worth a try as at full throttle, it would not change your existing mixture, but at idle, would definately be leaner as the fuel pressure is lowered.

Also - do you use a Map sensor? a fluctuating vacuum at idle can trigger acceleration enrichment if the Map sensor/parameters are not correctly configured.

I will print the Accel Manual and have a further read as it is very good in its explanation of EFi in general (would benefit other forum members interested in Efi as a general read) the various trigger types detailed is especially extensive. (flippin heck! - how sad do I sound?!)

Finally - "Hi, Paul. Been to 'Brands Hatch'lately, or do you cruise around the beaches at Brighton? (4 yrs. at RAF Lakenheath)"???? huh?? or do I have a short memory?? /ubbthreads/images/graemlins/confused.gif

 

[Mike]

Thanks for the info. You've made a point I hadn't considered, viz. the fuel pressure at idle without a MAP referenced pressure regulator. The car has never had one of those. On the original Gen 6 ECU, running alpha N, you could just dial the fuel table down. With the new 'smarter' Gen 7, you don't have access to fuel directly, you dial in VE. I was aware of running straight 45psi regardless of MAP (which obviously varies the actual fuel pressure as the MAP changes) but never put it together with idle. That might be the simple answer. (Note: the low impedance/step injectors are supposed to help with small idle requirements through the very fast rise time, and in fact they worked fine...Just too damn rich.
Alohas, Mike
P.S. My cryptic note re. Brands referred to MY 4 year tour at Lakenheath. I got down to the races at Brands and Silverstone quite often (Clark, Hill the 'father', Surtees et.al), played at Snetterton etc. You're fairly close, in W. Sussex, are you not?

 

[Paul Thompson 'Hooligan']

Hi Mike -
Let's hope the vacuum connection to fuel reg works - would certainly make a simple solution and seems to fit the existing scenario. Let us know if it works..

Thanks for clarification re Lakenheath etc - I'm near Goodwood (18 minutes'ish) but Brands is about 90 mins away. Snetterton - flippin miles!! /ubbthreads/images/graemlins/grin.gif

ps - what did you fly out of Lakenheath? F15s?? - I wish! - When I was at RAE Farnborough, I had access to fly (read back seat!) in Jaguar and Harrier (T4) as it was described as 'relevant' to the project I was working on. I do remember the then resident CO, Wing Commander Mike Brookes telling me that of all the aircraft he had ever flown, some 70 if I recall correctly, he described the F15 as the most impressive and 'mentally demanding' all in one package.

 

[Garrett Clark]

Mike,

I must first admit that I have absolutely zero real world experience with the Accel system. That said, I'm considering using Accel on my car, and I have recently read a lot of fuel injection books. So beware, my information could be worth exactly what you paid for it!!!

The advice you have received so far all looks good to me, (although I'd check the actual pulsewidths before changing the regulator) but here are of a couple other things to check:

The computer may be EXPECTING a vacuum-referenced regulator. The computer would then increase pulsewidths to target the correct A/F ratio with the lower fuel pressure at high vacuum. If the pressure isn't actually lower, the delivered pulsewidths would be too long and the car will run rich.

This parameter can be changed on the system configuration screen, but it is a little cryptic. You use the return/returnless switch. Here is a quote from the calmap help screen:

"Return or Returnless Fuel System: Select Return if the fuel pressure regulator is referenced to manifold vacuum. If the regulator is not referenced to manifold vacuum, or is
mounted in the fuel tank, select returnless. In this mode of operation the ECU will automatically calculate the pressure differential across the
injector."

So your problem could be as simple as flipping the return/returnless switch to the correct location in the system setup!!

Another possible problem is the ignition timing. You said that if you leaned up the mixture the car ran poorly. You may find that you need to increase your timing advance to get the engine to run smoothly with the leaner charge.

Hope that helps!

Garrett

 

[Mike]

Thanks, Garrett. It's been in the 'returnless' mode. It also idles best at about 28 degrees, and at max power WOT it likes 38 degrees. Got a 30 RWHP increase going from 34 to 38 degrees. The latest Gen 7+ V 4. CD that comes with the upgrade chip has an excellent 'manual' included. I don't know of any way/table to read or input actual pulse width on the laptop, like the old Gen 6 version.

 

[Garrett Clark]

Mike,

Oh, well, it was an easy check at least...

I guess I've started talking without posessing any knowledge, so I might as well continue!! I downloaded the demo Calmap Gen 7 software, and in that version, the pulsewidth information is displayed on the main "dashboard" screen with all the other gauges. There are two boxes at the lower right that indicate the live pulsewidth and duty cycle. If your version doesn't have those outputs, maybe an updated version does. You can download the latest version from mrgasket.com.

I really hope you get things figured out. I'm hoping to call on you if I have trouble figuring out my car!!

Garrett

 

[Mike]

You're right, Garrett. I was referring to something like the pulse width table in the Gen 6. You can read the P/W and duty cycle (mine runs about 70 % at WOT), but you can't access it directly, i.e you have to fool with VE. You can then see what the P/W result is. A 'tuning' dyno would really be ideal, except I can't find one in the area...there is one that hooks up to a standard 5 or 6 bolt wheel hub, but it wont fit my knock offs.

 

[Paul Thompson 'Hooligan']

Any News Mike? - Still running rich at idle? or is all sorted?