john banks

BTTT for Pascal.

http://www.scoobynet.co.uk/bbs/threa...D=84125&Page=6 The circuit on this page with the LMC7111BIN, 470R and zener is the one that ended up at 290 BHP and 290 lbft at 3100 RPM at PE with a Dawes, exhaust and TD04L hybrid with AE801 ECU at 21 PSI

[Edited by john banks - 7/2/2002 3:14:15 PM]

Paul_H

This thread is for posting the results of the DIY Fuel Cut Defender development, to save trawling through 150 postings.

It is possible that there will be other circuits developed in time, but the idea is that any circuit posted here has been developed, tested, and works.

So here is Circuit number 1:




This is what it does:




It is not just a defender, it is a LIFTER i.e. it prevents a fuel cut due to increased boost, but also provides a new higher fuel cut to protect against catastrophic boost levels caused by a fault e.g. wastegate failure.

The fuel cut defend point and the new fuel cut level are both fully adjustable.

Datasheets for pinouts for the chips are here, they take some time to download.

LMC6462BIN http://www.national.com/ds/LM/LMC6462.pdf
LMC7221BIN http://www.national.com/ds/LM/LMC7221.pdf
MAX325 http://www.maxim-ic.com.cn/Max2700-378/MAX323-M.PDF
R3 and R5 are 10mm multi turn top adjust cermet trimmers, to enable fine adjustment of the defend & fuel cut points.
The diode is 1N4001

This is what it looks like when built up:



There has to be a disclaimer here of course - no warranty of any kind, express or implied is given. This has to be, given that it is a DIY development - hope you understand.

[Edited by Paul_H - 12/11/2002 12:14:02 AM]

[Edited by Paul_H - 12/11/2002 12:15:27 AM]

john banks

Plot of above circuit going up and down through the input voltage range. Seems pretty clean. Most noise is probably the ADC - only about 9 bit accuracy. There are about 600 data points on the plotted graph. 5V supply. Note the defend zone seems to work to spec. Note that the upper limit is about 4.4V because of the voltage drop across the diode. This circuit is defending from 3.9 to 4.2V.

[Edited by john banks - 3/10/2002 2:52:56 PM]

[Edited by john banks - 3/10/2002 2:55:27 PM]

john banks

TTT. Any comments?

Floyd

iTrader: (9)

Look John, I've just about had enough of you! I've got a bag full of AFR bits and a wad of instructions. I've got a brand new DD from the original group buy, sitting on the garage bench and now I've got to try and build a programmable boost control and a fuel cut lifter.

Arrrgghhhh. I can't take anymore.

I feel I'm straying from the chosen path and my meditation can't cope with it all.

I'll just have to buy an STI7 instead.

F

Adam M

Guys, I know you are only trying to help, and I dont doubt for a second that you know exactly what you are doing, but does no one else think it is really dangerous making such info easily available to masses of people who might not be as handy as your selves?

I know there is caveat emptor and all that, but if you have the intelligence to work this out, what do you gain from making it so dangerously easy for those with less understanding?

I am sorry but in your position I would no be offering this "help" to others.

dowser

John - does it work in the car? Does it provide enough scope (what is the MAP sensor seeing between 3.9 and 4.2)?

Shaddup Adam - I mean, first there's the Dawes to modify boost. But you can't kill your car with that 'cos of OE fuel cut......OK, so maybe you have a point Maybe we need a password protected area for those "I want to kill my car but dont know how" type threads? Thanks for the pump by the way!

Richard

Adam M

np re pump.

will take that shaddup as a compliment for warning those who just follow the leaders blindly.

john banks

Not tested on car yet. 3.9V is about 16 PSI, 4.2V is about 19 PSI. So it will comfortably allow you to run 17.5 PSI.

Adam, it would take quite a bit of knowledge to build this from what I posted. Anyone that could do it would presumably have the nonce to know what they are doing.

I am not going to censor information just because it might be misused. Posting in a public forum allows things to get developed better.

But this is not one for the muppets to try. I do hear what you are saying but I am not the engine nanny. There are easier ways to blow your engine up - like fitting a Superchip, but we don't ban that.

dowser

Thanks John - seems fine. I'll order the bits for both (gee - my chip collection is growing ), but please let us know if you discover operational problems in the short term (maybe time to try your original ecu with dawes and fcd?!).

I agree on the censorship issue btw - how else are we supposed to learn?

Richard

john banks

I think you will beat me too it with the schedule I have presently. The only issue is as Paul where to take the 5V supply. I think this circuit will only be 2.5mA, but I don't have an ammeter that reads that low. You could use a 7805 and 2 caps as he showed. You could increase the 5K pots to 10K bring the current down to estimated 1.25mA.

john banks

Can you tell me the exact voltages you are running at Paul? Then it is just two proportional dividers = 4 resistors. Maybe my circuit needs to be like this since it is more susceptible to muppetdom being so easy

Paul_H

Richard

These are the readings I took on my car, they are only as accurate as my boost gauge of course

Bar--------MAP sensor output
0.9--------3.63V
1.0--------3.78V
1.1--------3.92V
1.2--------4.07V
1.3--------4.21V
1.4--------4.36V

let me know if you want me to carry on......

john banks

Between what voltages do you defend sir?

Paul_H

John

I have the defend pot set to 3.85V and the new fuel cut set at 4.3V which according to my boost gauge is defending at 1.05 Bar and new fuel cut at 1.35 Bar

in English money, based on 1 Bar = 14.5 PSI this is

3.85V = 15.25 PSI
4.3V = 19.7 PSI - don't want a cut whilst overtaking!

My best guess for a 19 PSI fuel cut is 4.21V
And really I think a defend at 3.9V is OK = 1.1 Bar = 16PSI

BugEyed

Wow

That is a serious level of boost you are looking at running!

Do you think that your turbo will make that sort of boost - I just can't see the MY01's TD04 managing anythign like that amount.

Duncan

PS Inovators are often called mad in their lifetimes! Well done for being the first.

john banks

We are only talking about fuel cut over 19 PSI, not running boost up there. My car runs 18 PSI with a fuel cut of 19.3PSI with sensible fuelling, timing, no knock, and sensible injector duty cycle. This I feel is the reasonable limit on a TD04L-13G - similar to what a lot of remapped cars run. Only 1 PSI more than a PPP in the midrange.

Paul_H

....and even then someone will flash past you like someone just did to me after the Wiggin Tree meet mind you I was in 5th

There is no doubt that the potential is there to get it wrong. I've got my Dawes set at 1.25 Bar, about 18.2 PSI - I may turn it down a little. It is bloody good fun though at this level

....of course - this is the problem.

Which is why some fixed value resistors in John's circuit, setting a more moderate fuel cut limit would be a very good idea.

john banks

Update on the circuit I posted. The start of the defend zone can be up to 4.4V off a 5V supply (approx 1.45 bar) and it can clamp all the way up to 5V if you wish. The only issue is that after the defend zone the output will be 4.41V because of the voltage drop across the diode. So as long as your car ECU as standard fuel cuts below 4.4 V you are OK. If it fuel cuts higher than this then this is a fuel cut defender not lifter. Most Scoobies would fuel cut before 4V and if they don't you don't need this circuit!

Previously I thought it would not defend beyond 4.4V.

So in summary it is better than I thought. 2 pots, 2 chips and a diode. Must try it on the car soon!

john banks

The circuit I showed works on the car. In fact these fuel cut lifters are better than that and allow a very neat solution see http://www.scoobynet.co.uk/bbs/threa...ThreadID=84125

john banks

This one works too.

Advantage: simplicity, cost, laughably easy to build
Disadvantage: If you need to change the gradient a lot, fuel cut can become very high (potentially so high that it won't ever be reached) and the atmospheric reading may be altered slightly - only 10-20mV - probably insignificant.

john banks

This works on the bench as shown off a 5V supply with good stability and no oscillations as shown. It places a perfect notch of 0.3V (3PSI 0.2bar). It does work lifting a bit more, but the voltage is only allowed 0.3V over supply so not recommended. 3PSI should be plenty

It uses two LMC7111 op amps, two 5K pots, and a 1N4148 diode.

I will post graphs and more results, but basically it works and I have no plans to modify it at all. Can't see how we can get any simpler. Hope it is not premature to post it here.

[Edited by john banks - 3/9/2002 11:46:19 PM]

Paul_H

I've been away for a couple of days and was wondering if there had been any interest. Glad to see there has

My lifter is working well on the car

I think that the information here should be posted and be available as a resource. No-one is forcing you to use it Adam and I respect your decision, please don't try to censor mine.

My lifter is truly adjustable i.e. you can set the defend zone to be anywhere you like which I suppose also means that it is easy to get it wrong too

John, is it possible to work out fixed value resistors for your circuit instead of the pots? to make it less possible to be mis-applied (I was going to say idiot proof but guess that would be naughty )

[Edited by Paul_H - 3/12/2002 6:29:54 PM]

BugEyed

[Edited due to multiple post]

[Edited by BugEyed - 3/12/2002 9:04:50 PM]

BugEyed

[Edited due to multiple post]

[Edited by BugEyed - 3/12/2002 9:01:55 PM]

Mclain

After looking at the schematics and stuff, i am willing to give it a try. I want to get rid of my Fuel Cut Defender and replace it with this lifter. But to every radioshack i go to, nobody can get the LMC chips and the max325. Now i think i found a replacement for the LMC7221. At least i think a LM311 would do the trick. And for the 6462 i could use a LM358. But what about the Max325.

Or does anybody know a online store wich ships to "The Netherlands"?


Thanx in Advance.

Mclain

john banks

I think there was another thread with a very simple fuel cut lifter which still allowed a fuel cut, I think it had a diode, a resistor and an opamp.

john banks

Or was it this one:

Mclain

I considered the option of the plain and simple fuel cut lifter. But considering the ammount of knowledge(electrotechnical) i can gain from this project i want to complete the lifter with dual opamp, comparator and analog switch. And the ability to control the fuel lifter completly gives it an advantage.

Gonna check some books to see if i can find a replacement for de Max325. Or else i will need to search for an online store to order the parts.

If i cant find a online shop or a replacement for the parts, is there someone who would be willing to buy the parts in a local store and send them to me(against payment offcourse)

TIA

john banks

You'll need to search the datasheets. RS and Farnell are good suppliers of these sorts of bits.

I can't remember the details it is all so long ago, but I think op-amp choice was primarily so that they were rail to rail off a 5V supply.