soldave

iTrader: (1)

For the first time since getting this once non-working S5 Tii FC I got it onto the roads and finally got it into boost. Have a very old HKS EVC boost controller and set it up to use normal stock boost. Put my foot down and watched my boost gauge (aftermarket, not the stock one). Quickly headed up and hit over 9psi before I got off the gas. Was expecting the fuel cut or boost controller to come in but it just didn't.

Now the boost controlling problem is a separate issue, and could be down to a duff controller or a sticking actuator or something. But I was really surprised the much talked about fuel cut didn't hit. I don't have a visible FCD in my engine bay or anywhere else, so I was wondering if it's possible the previous owner has ghetto-rigged something by cutting a wire. Very curious as to how the boost was going so high without a cut coming in. If it doesn't fuel cut then that's potentially great, but I'd really like to know why.

LunchboxCritter

iTrader: (9)

crack your ecu and see if it has been "chipped"

soldave

iTrader: (1)

Might be a good call. Don't think it's the case but will take the top off the ECU in the next day or 2 and have a look.

arghx

iTrader: (3)

You're in Japan, a chipped computer seems likely.

soldave

iTrader: (1)

Could be, although I didn't see any stickers when I glanced at the ECU before though. Could be wrong though - not too hard to inspect and find out.

soldave

iTrader: (1)

Just a thought, but can anyone confirm that the N374 ECU does have a fuel cut? Might seem like a silly question, but just through past experience with DSM ECUs in the States compared to early Mitsubishi Evos here in Japan. The ECUs were almost identical but a couple of things like fuel cut were not in the Japanese cods.

HAILERS

I'd GUESS that it does have fuel cut seeing as how NZCONVERTIBLE obviously had a series four JDM car and it had fuel cut.

You might make sure the ECU is seeing the signal from the boost sensor. Get a meter out and turn the key to ON and check your reading against the Fuel and Emissions section of the FSM. Look in the Control Unit pages for the value.

soldave

iTrader: (1)

I'll check it, but I think it is seeing some sort of signal as I've seen the stock boost gauge move. Will have a look tomorrow night.

soldave

iTrader: (1)

Will finally get to do some multimeter testing on my ECU tomorrow or Monday as I've got a long weekend due to a national holiday.

Was on the expressway though and floored it in 5th. As soon as it got spooling is was heading way up to 1bar/15psi and I had to get out of it. Could be a sticky actuator or duff boost controller but I'll find that out in time. No fuel cut though. One thing I did notice was that the stock boost gauge only starts to show any movement at all once I'm already in boost. What I mean is that the needle is nowhere near 0 on the stock boost gauge until I'm at least at 3-4psi. Is this normal for the stock boost gauge or should it be a little more accurate than that?

Will test voltages tomorrow and see what results I get.

soldave

iTrader: (1)

OK, voltage tests finished and it doesn't help me a huge amount. 2.35V is detected at the sensor, and when 100mm of vacuum is applied it drops to 2.05V which is right within spec as checked by page F2-82 of the FSM. Checked pin 2H at the ECU and got exactly the same voltages, which would suggest that there is are no breaks or resistors in the line between sensor and ECU.

However, I think the FSM is throwing out some false spec values on page F2-78. It states that the voltage at the ECU from pressure sensor should be 2.8-3.2V. But that value is higher than the original signal voltage coming from the pressure sensor (spec is 1.9-2.1V). Now I'm no electrical expert, but voltage shouldn't increase along a stretch of wire). Do you get what I mean?

Doesn't help with the lack of fuel cut but thought I'd let you know the results.

HAILERS

**********However, I think the FSM is throwing out some false spec values on page F2-78. It states that the voltage at the ECU from pressure sensor should be 2.8-3.2V. But that value is higher than the original signal voltage coming from the pressure sensor (spec is 1.9-2.1V). Now I'm no electrical expert, but voltage shouldn't increase along a stretch of wire). Do you get what I mean?
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I don't understand what you mean. Where do you get the 1.9-2.1vdc figue from? I musta missed reading something somewhere again.

What does the ECU have at 2H when the vacuum line is off and plugged ? Match the figure in F2-78??? The 3.4v to 3.6vdc?

The ECU number is ??? what again? Off a convertible?

I have to reach back a bit for this idea. Seems at one time I had a hand pump (can't remember the name of the device I got from AutoZone right this minute) that outputted pressure and also vacuum if rigged right.

I took that pump and put it on the boost sensors nipple and capped the vacuum hose. I ran the engine at idle and applied pressure while looking at the voltage on 2B (series four). IF memory serves I could make the rear rotor cut fuel doing that and at the same time see what the input voltage was to the ECU from the boost sensor.

So I suggest you do the same. Apply pressure to the boost sensor at idle and see how things go.

I'd be more interested in what the voltage input to the ECU is when your boosting at ??? whatever figure you say your boosting at with no fuel cut. That would be interesting. I forget exactly the voltage figure. Something like 3.65vdc. The exact figure is in the archieves in the DIY FCD thread. Paul Stoakes wrote the article on the FC3S FORUM some decade or so ago.

There might have been more to do than input pressure to the boost sensor. I might have had to disable the TPS at the same time to make the ECU think it was being driven. I'm not sure. MAYBE I can do this tomorrow one more time for oldtimes sake. But tomorrow is a busy day, what with it being the Sabath and all which means MOTOGP will be on the air and I've got to go rowing earlier, then theres the lawn needs cutting, food to be bought and a couple of long naps to do.

Oh hell, I KNOW I've gotten fuel cut in the driveway at idle inputting pressue to the boost sensor. EDIT: used a MITTYVAC.........that's the name I forgot.

HAILERS

OOOPS. MY bad. I have RTEK 2.1 in all three cars and as you know, RTEK eliminate fuel cut. So can't do what I suggested I might do.

I used Fluke88 and Mittyvacs prior to them coming out with RTEK 2.1.

soldave

iTrader: (1)

This is what I mean:



It's saying the output voltage from the pressure sensor should then increase by the time it gets to the ECU to be within spec.

The ECU is an N374 from (and still in) a 1991 JDM S5 car. When the vacuum line is off and plugged the ECU voltage is 2.35 volts, and when 100mm of vacuum is applied it drops to 2.1V, which is what it should be according to the S5 FSM, page F2-82. Have used another known working pressure sensor and got almost excactly the same results.

HAILERS

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Nope. What your read at the boost sensor is what will be read at the ECU plug.

I'll read that page in the FSM later, but what you read in the section called CONTROL UNIT where it lists the input/output for each pin, that is what should be happening.

Something is screwy with that other figure. Later.

Why not take my advice and put PRESSURE on the boost sensor and watch the voltage output of the boost sensor. See if the voltage will rise over 3.65 vdc when pressure is applied and what is that pressure when voltage over 3.65 is applied?

EDIT: I think there is a typo in that manual. The Control Unit page should ape the other page with the low voltage figure. As to which is right? Still confused on that. I notice that the non turbo Control Unit pages ape the TURBO control unit pages for pin 2H. The meaning of me writing that? Go look at Turbo vs Non Turbo in the series four FSM. Not the same for each in that manual.

HAILERS

EDIT: Reading your post #13 just above this one.........I'd say that the CONTROL SYSTEM page has the typo. That page apes the NON TURBO page if my memory is right. TYPO in the Turbo FSM for pin 2H on the Control System page.

'Wonder how many people bought another boost/pressure sensor due to that fault.

Sorry 'bout the disjointed response. Things are not working out quite right this morning. Gotta get back on track.

soldave

iTrader: (1)

That's cool man. You're responding which I appreciate and it does look like there is a typo in the S5 FSM for that. I might see if I can get hold of a Japanese FSM from Mazda to look at and see what the voltages say in there.