Hey all,

A long time ago, I had my car dyno’d, and as you can see by the dyno printouts (see below), it was running rich as (top readout, bottom two AFR lines). It was at a dyno day at BDT, and they then went demonstrating the effects of reducing the fuel pressure to increase Air Fuel ratios, increasing performance and also improving the economy. The final result was a 3kW gain and with the AFR sitting around 12.1-12.8 as seen on the lower picture.

Now whenever I have contacted them lately, they just try and sell me a UniChip is they are now a retailer, and don’t want to know about the AFPR method. SO, I want to install one myself, and then have it adjusted on a dyno (BDT or Elsewhere) to improve economy and performance.

I am aware that standard fuel rail runs at 270kpa or 39.15psi. I have been looking at other inline adjustable FPR’s on Ebay, and came across the following:
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... 43724&rd=1
I believe this to be correct for my usage, as it is adjustable from 20-85psi, and also has a vaccum feed, which would be fed from the manifold to adjust pressure accordingly at idle and WOT. Accordingly, I would set the fuel rail pressure again at 39 psi to ensure no running lean until I could get it onto a Dyno to set correct AFR’s

NOW, can anyone confirm that I am correct, as I don’t want to go spending $150 on buying and fitting this thing to find out it doesn’t work. Also, could anyone recommend a dyno shop in Adelaide that would tune it for me?? (Grant or Martin??)

Thanks
Lee

Dyno Results

**Edit** If pic doesnt show, its in my gallery

try rpm on deloraine ave. i had the exact same thing. obviously all fords will. runs rich as buggery at top end. they too suggested adjustable fuel pressure but from memory they quoted around $190 fitted and tuned. with fuel the way it is i might start down this road again also. let me know how you go if you do it.

The first problem with all these adjustable regs is that they are installed in the fuel return line and don't replace the stock reg. This is fine if you want to increase fuel pressure, but if you try to drop it the stock reg will take over and hold it at 39psi. For it to work you will have to remove the stock reg somehow. Another problem is the lower fuel pressure will result in the EEC gradually learning (over a few hundred kms) to richen up the mix to get the correct AF ratio under light load and this will then transfer back to WOT, so the result may not last.

Personally I would be putting the money towards a EEC mods like a unichip or chiptorque. If you are running a stock or mild cam, an off the shelf chiptorque chip can be quite usefull because it is simply changing the AF ratio targets in the fuel table and usually add some timing too. With large cams it becomes more difficult as the load functions are thrown out quite a bit.

I was wondering abou this, If the pressure is reduced though, how would it then bring it back to rich again? would the injectors just be running at full duty cycle all the time then? The reason I ask is as Chris (MightyEF) had one put on his EF a year ago, and he still gets good economy?


I appreciate what you are saying here, and if I had $1,000 in the near future I would. The thing is I wont be keeping the car for much more than 1 year, so its not worth the $$ as this isnt a long term investment, I just want an improvement now and the $200 for a reg I can come up with.

The reduced pressure sees less fuel go in for every ms the injector is "open" (compared to standard fuel pressure). This is the premise of the idea - less fuel, leaner burn, more power.

EEC has a target air/fuel ratio when you are crusing around - 14.7:1 IIRC. Therefore, if you reduce the pressure and therefore lean the mixture to, for example, 15:1, EEC will immediately increase the amount of time the injectors are "open" to bring the air/fuel back to its target 14.7:1

Let's say it increases the injector pulse width, on average, by 3% at the new, lower fuel pressure to achieve the 14.7:1 a/f... it will apply this to the full throttle fuel map.... i understand it takes a significant amount of time before it applies this to the full throttle settings.... would like to hear grant's thoughts on this....

could be negated by resetting the ECU on a regular basis?

It doesn't take long at all to apply the changes to the WOT maps, it actually occurs straight away. As soon as you start the car it will target the AF ratio given inthe fuel maps, for cruising that is 14.7. The EEC knows how much fuel it should give to make that AF ratio but obviously that is not always correct, especially when mods are done or fp is changes. To adapt it has a function called KAM or short term fuel memory, so yeah as you said it then measures how much more fuel is required to obtain the correct AF ratio and then it applies that across the board.

The thing is that lowering the fp will have a greater effect at WOT than while cruising so although the EEC will add more fuel to compensate for the lower fp, it won't be able to totally adapt at WOT. So it will work to some degree, but to get the desired AF ratio at WOT you will probably need to dramatically reduce the fp, and that may max out the injectors.

Regarding the chip, yeah I understand that you want a cheap fix and I think the reg may be worth a try. What I was thinking of was the off the shelf chiptorque chips for $595, still expensive but at least they are cheaper than the unichips at $1200.

Well then the answer is easy isn't it?

Increase the fuel pressure. This reduces injector duty cycle and pulse width @ cruise, so it will lower fuel across the map. Dat's what we want isn't it?

You could just wait till a few of us here get the Megasquirt-II adapted to the Falcons and get complete control.

Edit: Jesus! Unichips $1200? I'll gladly sell Megasquirts with wideband O2 for $1200. That's just stupid to spend that much on a unichip.

if the EEC looks for an optimum of 14.7, looking at my dyno readout it gets no where even near that. (12.5 is best at low revs/power) Now, I know that is at WOT, but just cruising, does the AFR change that much? Surely just under normal cruising the AFR would be close to 13.5?? so there is improvement to be made I would have thought. What would be everyones thoughts on this?

Yep, sure does. 2 key words here are closed loop, and lean cruise.

Waggin,

could you explain a little more to me? so when at WOT its in open loop mode (ie. does not look to 02 sensor reading) but when at cruising it is in closed loop. What sort of AFR are normal during closed loop operation? Does it often range over the 14.7 and therefore increasing of fuel is common?

My car is running rich and I seem luck to get 400kms out of 58L of fuel (14.5L/100kms) which is pretty average.

Yeah you pretty much got it mate. In closed loop EEC will target 14.7. The standard oxy sensors only have two states - rich and lean, so it will manipulate fuel injection to "average" stoich ratio (14.7:1)...

Check out the flash anim on this page:

http://hp.autometer.com/techtips/faq_te ... _fuel.html

14.7 is in the middle of the gauge (top)... rich is green, lean is red... this is what these gauges do at idle and cruise.

are those gauges worth it martin? mine is running very rich, and have been following this thread with interest as i was going to be throwing an AFPR onto my car

They are purely imformative. Nothing more. You can tell when the car is in closed loop and when it's not. I like mine because i've learnt quite a lot watching what EEC is doing at certain load points - but then, im kinda fascinated by the ins and outs of EFI. It is handly in telling something is not right - i.e. if it hangs in the green area then it's running rich, constantly, and is not running properly in closed loop.

They are simply expensive voltimiters calibrated to HEGO output (0v-0.9v). I had a lot of money at the time

whats the cost like for them mart? i'm pretty uninformed about the EEC etc, so i guess it would do sweet FA for me really!

Think it set me back about $150