Jaycar Boost and Fuel Control

[sl33ek]

33% more fuel, I didnt realise it can be that high.

Pretty sure thats whats is happening to me too

But hopefully after the tune it will improve things!

Edit - I just spoke to BelGarage, they can fit me in this Saturday because somone cancelled! They quoted $200 flat which includes 1 hour dyno time and a before and after dyno graph so I'm very happy with that. I'll post the results when I get the chance.

They were familiar with the DFA too, they'ved tuned quite a few which is great, I thought I was going to have to explain it to them!

Edited November 30, 2005 by Gengis

[benl1981]

They must have done a few since I spoke to them last. Thats great.

I've heard reasonable reports about them but havent actually taken a car there.

[sl33ek]

I've installed it in my car yesterday after work, it took 2 hours.

Most of the time was spent double checking wires from the ECU. I wanted to make doubly sure it was the correct wires as I was very nervous about cutting the wrong wires. Ben, the docos you gave me came in very handy and the wires you singled out were spot on.

I used female and male spade plugs for the connections and wrapped them in heat shrink.

At idle when cold, it is at load point 31 and settles to 30 when warm, cruising is at load point 50-60 and full throttle it is at 95, so my range is 30 to around 95.

I've done a conservative tune of -4 from load point 30 to 60 and -6 from load point 61-95. It was a blind tune, I had no info on what my AFR was, I know its dangerous, but I was careful and kept the windows down listening for any detonation.

I noticed there was alot less exhaust pops (I have atmo bov) but performance is more or less the same, maybe a little smoother.

I've attached pics of how the unit sits in my car

Edited December 1, 2005 by Gengis

[Fly_With_Sky]

hey i want to just verify something as i have a DFA and am ready and willing to put it in my r33, however as the mechanic i go to doesn't really rate them as he sees them as 'toys'.

from what i see they are a cheaper device with the same parts inside and do the same thing as the more expensive piggybacks like the safc or e-manage (the only difference being that you put them together yourself and dont look as good as a safc).

However, my only concern is that if the device does fail does the ecu still have the ability to richen up the mixtures so as to avoid engine damage?

Also has anyone installed and tuned a DFA and then checked the A/F ratios a few weeks later to see how well the device actually works.

Thanks.

[benl1981]

Hey Gengis - at low load inputs e.g. Probably about 30 to 50 or something any changes you make won't lean it out because the engine is in closed llop. I.e. ECU will vary injector pulse based on 02 sensor reading. So what you'll get is probably just a gegree or 2 more advanced timing by taking out voltage at these load points.

Glad it is going ok

[AlexCim]

Ok, Well, i have gone to retune my EBC and found some interesting things going on.

I wanted to make a std boost map and a 10psi map. My std boost map is flat across the board 100% duty cycle. Let me just say that all my vacumm hoses are now plumbed up correctly and my vent is 1mm drilled.

Anyway, for the 10psi map, i have got the duty cycles set as such 0-12 0%, 13-64 32%. This gives me a flat 10psi curve, but on the gear changes (auto) the car spikes to 14-15psi (i get scared and let off the throttle)

With my old 1.25mm std stagea vent, i was needing to use duty cycles around 72-76% to get about 9psi and was getting slight spiking, maybe 1-2psi.

I dont know, i just think 32% is too low. I think ill replace all my vacuum hoses this coming week with new units, get small clamps for everything too and make sure its all sealed up nice and tight.

Anyway, anyone got any ideas on the mega (halfed) duty cycles and the 4-5psi spike? What % are others using, i remember SK using about 80...

[AlexCim]

Ok, dont really worry about that top post. Did a search in this thread and found Post #592 till Post #594 to be very helpful.

I guess ill just flatten out my curve a little more as 0-32 is a big change. And i guess now with the smaller vent, the changes in duty cycle are even more resolute.

Ill go do some testing with a friend, its a bit hard to watch a boost gauge and steer at the same time.

Cheers.

[chrissso]

Its the size of the vent... alhough 1mm to 1.25 mm doesn't soundlike much - its whats making the difference. I have a 1mm vent and My duty cycle is 32% to make 10 PSI... So, it sounds right. I can't find a 1.25mm drill bit anywhere.. Someone on this firm was using a 1.5mm vent and it wouldn't boost below 13 PSI...

[AlexCim]

haha, that was also me, before i resoldered it and drilled it to 1mm (didnt have a 1.25mm drill bit)

I think thats a standard 180sx vent...

[Sydneykid]

hey i want to just verify something as i have a DFA and am ready and willing to put it in my r33, however as the mechanic i go to doesn't really rate them as he sees them as 'toys'.

from what i see they are a cheaper device with the same parts inside and do the same thing as the more expensive piggybacks like the safc or e-manage (the only difference being that you put them together yourself and dont look as good as a safc).

However, my only concern is that if the device does fail does the ecu still have the ability to richen up the mixtures so as to avoid engine damage?

Also has anyone installed and tuned a DFA and then checked the A/F ratios a few weeks later to see how well the device actually works.

Thanks.

<{POST_SNAPBACK}>

Hi, the DFA is simply a voltage changer (same as an SAFC, EManage etc) it takes the voltage output from the AFM and lowers or raises it (depending on your mapping) so that the ECU sees different voltages. This modifies the A/F ratios a lot and the ignition timing a little according to the standard ECU mapping.

The components used in the kit are all high quality and very stable in their operation. I built my unit more than 10 months ago, it has travelled 15,000 k's in all sorts of conditions. The voltage output mapping is precisely the same as when I installed it. Every time I have checked the A/F ratios they are exactly as I mapped them. I have made several steps in the modification process and the DFA has been able tune for all of them so far.

If the DFA fails, it will stop working and the car will stop because there is no AFM signal getting to the ECU. You then have 2 choices, you can restart it and drive it home in limp home mode. No more than 2,500 rpm, super rich running, retarded timig, slow but safe. This is exactly the same level of protection as Nissan built in for AFM failure.

If you want you can simply disconnect the DFA and join the AFM input and output wires together and the car will drive exactly as it would with a standard ECU (ie; no mapping changes).

If the DFA partially fails, voltage spikes, etc the ECU will see this as faulty AFM readings and go to limp home mode.

Talk to your mechanic about the above, if he still thinks it's a toy, better off that you find another mechanic.

cheers

[NewKleer]

If the DFA fails, it will stop working and the car will stop because there is no AFM signal getting to the ECU.  You then have 2 choices, you can restart it and drive it home in limp home mode.  No more than 2,500 rpm, super rich running, retarded timig, slow but safe.  This is exactly the same level of protection as Nissan built in for AFM failure.

<{POST_SNAPBACK}>

i think if it fully fails (eg power wise) then it will pass input off as output (ie, a short circuit between in and out? i remember with it switched off there seemed to be a short circuit between them.

if u are a bit hesistant, then wire up a switch (which is what i did) to get it to bypass the DFA.

[sl33ek]

Well I had it dynoed and the result wasnt good. I had it removed because my car was undrivable and I'm sure its because there is a fault with my particular DFA.

On the Dyno my car blew alot of black smoke - enough to blacken their wall - at full throttle so that was a sign something wasnt right because I've had mates follow my car in the past going full throttle and they've said I dont blow that much smoke, only small puffs between gear changes.

Then the big surprise was when the dyno found I was running dangerously lean (like 18:1). It still made good power (~158kwatw 400nm torque)

They tuned it to the best of their ability to a safer ratio but it had a nasty dip in power in the mid range. So I left the place scratching my head.

Driving home, I found the car hesitated at random, just like on the dip in power on the dyno graph, I'd be cruising in 4th or 5th at 2000rpm and it would feel like the fuel pump stopped for a second and come back on, so I pulled over, got a pen and wront down all the tuned values - and reset the DFA. But it still happened even after the reset so that got me sctrathing my head too.

I drove around that night to make sure it wasnt a one off thing but the same thing happend after 15 minutes.

Sunday morning, I removed the DFA completely, called a friend and I we went for a drive with him following behind me so if anything happens he can help. I drove for 200kms without a problem, so I felt brave enough to go full throttle up to 4th gear and my friend said he only saw small puffs between gear changes so it seemed fine.

I dont think its the fuel pump and I've had the AFM tested and the spark plugs and cam timing. I'm hoping its just my particular dfa giving out incorrect readings. I havnt had time to test it on the bench again until this weekend to be sure

Well thats my experience with it, I wish it was more positive but oh well it was still a great learning experience.

Here's the dyno graphs

DFA untuned, note how lean it is:

DFA tuned to a safer AFR:

Edited December 5, 2005 by Gengis

[NewKleer]

did u do it in course mode or fine mode? is "untuned" meaning the -4 or -6 u did urself just for fun? or all zeroed? definitely something stuffed up there. if u did it in coarse mode and -4 to -6 without a dyno, im not surprised if u damaged some part of the engine, that is a pretty major change (30%?)

[sl33ek]

it was all in fine mode..

Edit- I dont think I damaged anything, it drove exactly as it did before i put the dfa in for all of Sunday and to and from work today

Edited December 5, 2005 by Gengis

[NewKleer]

all the calibration turned out fine as per the manual and so on?

tried setting a load point to 0 and make sure that in = out?

[sl33ek]

yes, the input=output. Well, it was out by .2 of a volt but it was pretty much the same

[NewKleer]

.2 of a volt is about 10% of your average usable AFM range (eg load points 30->90 = 2.5v range) so that could have something to do with it. and maybe since you dont seem to think its much of a problem, perhaps you were a bit too lenient with other calibration steps? maybe retry it all again?

[benl1981]

Hey Gengis - sorry to hear that mate..

I think I have the receipt for the DFA somewhere here...

input should have = output spot on. I don't know if 0.2 volts should have made that much difference but the whole point in the calibration is to make sure input = ouput.

Shame they didn't stop the tune after they found the lean running - that should have indicated something was not right!!! Either fuel pump or the DFA or injectors or Fuel pressure reg or fuel filter.

Wonder what the black smoke was then.

If you check the DFA on the bench and get output to = input there shouldn't be a problem. Then when you get it in the car check when settings = 0 (i.e. no adjusment) that the output = input for idle and then at 4000rpm held constant. If you keep the cover on the DFA open you can check this easy.

So sorry to hear you had such bad luck. When I had it working on the bench it seemed to do exactly what it should have however I just wanted to check with a constant voltage source to ensure calibration was right.

I think the 0.2volts difference may have been causing the issue.

Let me guess output was 4.8volts when input = 5v

i.e. by doing this it is the equivalent of using a resistor to shift all the AFM values down.

It may be a combination of the the DFA calibration, and some fuel system issue. Shame they didn't just take the wires out of the input and out of output and joined them together to check the AFRs then. Then you would know for sure if it was the DFA causing lean out or other issue..

Edited December 5, 2005 by benl1981

[sl33ek]

well yeah but its weird, I'd get it spot on on the bench, but I'd test it with the voltmeter and it would be out by .2 again.

I dont think i want to put it in again hehe. I'm going to get another dyno done early next year and see if I'm running rich or lean and go from there maybe with an safc. I'm not bagging out the dfa, its great for what it is but I think mine just had gremlins

Yeah Ben, thanks. Don't worry about the receipt, really its not your fault, you were honest about it needing to be calibrated so you didnt know. The black smoke got me puzzled too, my car never blows black smoke. After I removed the DFA the smoke was gone

Edited December 5, 2005 by Gengis

[benl1981]

Thats a bugger. I'm really disappointed about that..I don't really think there is anything wrong but calibration...if there is I will take it back for you

I found that with the unsteady voltage from the pot that as soon as you removed the multimeter from the I think input measuring terminal the load point increased so you were no longer comparing apples with apples when you moved the multimeter to the side that was measuring the output

Wierd. Thought having a stable supply would definately stop that. I.e. a 5v source or similar...

Edited December 5, 2005 by benl1981