Scott.T

iTrader: (2)

Pipework is the same for early UK and WRX's and this was a concern that Subaru and Prodrive had when running more than 1 BAR. They were concerned that the 'Plastic' pipe to the intercooler would fail leading to Warranty issues if the PPP was greater than 1 BAR.

The MAP sensor is also thought to become un-reliable above 1 BAR, although I am lead to beleive that the WRX uses a different MAP Sensor. But then a Standard early WRX only runs about 10psi. Greater performance is achieved by better mapping and larger injectors (among other things).

We need a comment from Scooby Racer 'I think'

[Edited by Scott.T - 4/4/2002 2:30:02 PM]

David_Wallis

Forgive my stupidity /ignorance... what ever...

Just out of interest.. this method doesnt actually add any more fuel does it??

Are you just upping the boost to within the limits of the car running rich??

I understand everything in theory and could make the circuits... but just wanted to understand this a bit more first...

The bit that confuses me is that John was running a prodrive ecu, but you say that you have tried this with a standard ecu...

I've got a 94 uk turbo.. which I believe has the td04l??

David

Paul_H

For information, the current passed by the MAP sensor is absolutely miniscule. Something like 0.002 mA.

If anyone is interested, my lifter posted on the DIY Fuel Cut Lifter thread has fully adjustable defend and fuel cut points, and has been on my car for quite a while now, just sitting there quietly doing its thing in a most effective way. I've almost forgotten it's there It's too good for just one to be built surely? Come on, just one more?????

john banks

David:

I don't think your car has a TD04 - probably a TD05?

Fuelling is MAF not MAP based, so it actually fuel at least as rich at 18 PSI than say 14 PSI - so there is more fuel going in because the ECU sees more air passing through the MAF sensor. The MAF sensors on early cars can saturate though apparently along with the other "weaknesses" outlined above.

Paul:

"the current passed by the MAP sensor is absolutely miniscule. Something like 0.002 mA."

Do you mean the current flow from the MAP to the ECU?

If so that suggests a very high input impedance at the ECU which means we could get away with only a single op amp in James design at the MAP sensor end?

I am keen on James' design over ours because it will allow the ECU to control held boost - if it goes higher because of gear or environment/track - it will just peak higher but the held will be the same. It would be a wonderful solution.

Paul_H

Yes, negligible current flow from the MAP sensor to the ECU. The MAP sensor is expecting a very high input impedance from the FCL input. Current levels are so low that I found the capacitor (0.01uF) which I was using as part of a high pass filter on the input caused a check engine light (once only, after starting the engine) when first opening the throttle in anger. I think the MAP sensor was charging the capacitor! hence I removed it.

I think that as long as the output impedance of the FCL is equal to, or lower, than that of the MAP sensor it should be OK.

David_Wallis

so basically you are saying that adjusting the actuator and modifying / replacing the restrictor increases the boost, presumably by holding the wastegate shut longer.. thus flowing more air and the ecu adds more fuel as required.. How does the boost cut then work?? Is this down to the restrictor??

David

Paul_H

Fuel cut is done by the ECU which reads the voltage put out by the MAP sensor. As boost rises, the voltage sent to the ECU increases. When it reaches a preset level the ECU cuts the fuel. Hence if you modify the signal that the ECU receives from the MAP sensor, you can modify at what boost level fuel cut occurs.

David_Wallis

I see... I was being stupid and thinking that there were two different sensors... thick twit... now I see..

Think I may get tinkering.

Port the exhaust manifold weld the heatshield back on, and make my own down pipe first though...

Can you remember the link to the lambda sensor monitor??

David

john banks

You mean the DIY AFR? If so it is in drivetrain within the last month and has about 5 or 6 pages. Scan down the posters and look for my user name.

Paul_H

With just 2 turns on the actuator I'm getting 1.2 Bar held, about 17.4 PSI, and while this is good, it isn't quite doing it for me if you know what I mean

I was running 1.25 Bar - about 18.1 PSI with the Dawes, this makes it much better . John, from your experience, will another turn on the actuator make much difference or am I better looking at the restrictor? I've actually just put another turn on the actuator, so will see tomorrow, and taken the restrictor out to measure it. On my car it's about 1.1 - 1.2mm - a 1mm drill passes through it with clearance, so I can easily make a 1mm restrictor by drilling the shank of a bolt etc. Any ideas what would work best?

john banks

It was a cool evening and misty so I though I would take advantage since I still had double dose octane booster in the tank from the track session and the ambient was only 6 C. Put the boost to 19 PSI 1.3bar - rich all the way, pulling very hard indeed right past 6000, but get this - charge temps never went over 23C. No wonder it was running well.

Need to measure more in daylight heat, but on the road it works incredibly well, and it felt incredibly brisk and smooth. There is so much power that you just couldn't be on it enough of the time to heat up the charge temps too much I don't think, but I'll try on a hot day. If I get the temps over 45 C on the road I'll turn it down. Until then I think I should enjoy If I watch the charge temps the engine should be happy. If the turbo goes wonky it is a good excuse for another one. However, some have run 25 PSI for several months and only after a while did it start to get dodgy, so running 6 PSI less hardly seems too silly.

This is two turns of the actuator and 1.3mm restrictor. This runs 2 PSI more than a 1.35mm restrictor and one less turn, so I think you will smile if you get it right

Note that with the PPP though the duty cycles are higher hence me being on a larger restrictor.

This combination I have now only peaked up to 19.5 in 5th, in other gears it was 19. The boost is holding now 15 PSI at 6000 RPM which is better than the Dawes was holding. It is incredibly good to drive, very smooth, best my car has ever been with any boost control setup. Just need to hit that sweet spot.

Paul_H

Sounds good Mine too is very smooth, and I think much better reliability wise, particularly the gearbox - just that more grunt is required so more tweaking tomorrow!

David_Wallis

Where do I find the information on the restrictor as well... what sort of boost should I look at running is 16psi asking for too much with the standard ecu??? I presume I need to make my own restrictor... I guess from what you are saying that there is one on the car allready?? not that I have to make one and add it..

Is there anything else I need to change if I look at doing this??

David

john banks

On an early model 16 PSI may be a lot more sensible for some of the reasons outlined earlier in the thread.

Adjusting the actuator seems the easiest way. But I have made some restrictors using 5mm bolts. Drilled a hole down the middle with a Maplin precision drill set and then cut to the same length as the original restrictor. Much better than the drill/solder/redrill routine. But only 0.1mm can be 2-3 PSI so adjusting the actuator is a bit finer to get it right.

On my car two turns of the actuator adds about 2-3 PSI and you can turn in in half turn increments, so it has about four times the resolution of a fine drill set.

I intend to work out James circuit as I want to be able to adjust in cabin the held boost by changing the gradient which this will allow - the peak boost is determined mechanically on the classic shape Scooby.

Cosie Convert

Can I just say EGT to you guys

It may not be a problem but I think it's worth someone checking.

The smaller TD04 will build a lot of exhaust back pressure in driving the small turbine to achieve the higher boost levels. This can cause additional hot exhaust gas to stay in the cylinder from the previous cycle.

So whilst charge temps may be controlled due to a low ambient and fuel may be adequate, exhaust gas temps could be higher than desired.

I'm sure the i-club guys said their EGTs were highest on cold (dense air) days.

Just a thought !

hmhaga

If I tighten the actuator by e.g. 2 turns - WITHOUT modifying the MAP signal - max boost level will not rise at all?

In other words, to increase the boost level on my MY98, I have to tighten the actuator _AND_ install a fuel cut raiser?

The reason I'm asking is that increasing max held boost from 0.9 to 1.0 bar by simply tightening the actuator would be a VERY straightforward modification

David_Wallis

Where do I find this restrictor??

Edited to say I found it... 18 pages back http://www.scoobynet.co.uk/bbs/threa...threadid=57428

Also what are the differences between td05 and td04.. and dont say 1!!!

What is the best way of measuring egt's what is capable of these temps?? anything cheap of the shelf??

David

[Edited by David_Wallis - 4/5/2002 12:22:21 AM]

[Edited by David_Wallis - 4/5/2002 12:23:50 AM]

Scott.T

iTrader: (2)

Just adjusting the Actuator will increase boost initially, but after just a short drive the ECU will change the duty cycle and bring the boost back to stock levels, as you have breached the pre-determined limit.

You will need the lifter to fool the ECU, therefore allowing more boost and no change to the Boost Control Solenoid Duty cycle.

P.S This is just theory on my part, as I have no got round to building the lifter yet.....

David_Wallis

anybody got any links to thermocouples?? as I am about to make a new downpipe so I could mount one in a similar place to the lambda sensor whilst I was at it..

David

john banks

RS 206-3722 meter and 363-0294 exposed junction fitted plug K thermocouple with 2m lead is what T-uk and I are using for intake. Looking at my downpipe with a drill in mind just now...

The I-club guys seem very keen on 3 inches after the outlet of cyl #3, but the downpipe does look a bit easier!

john banks

I'll order one and come and pay you a visit then. My only reservation is if you remove it later will the sealant adequately seal the hole? 800 deg C and 1.5mm?

I was thinking of measuring at the turbo outlet-downpipe flange by loosening it and putting the probe in slightly, but being twin dump this would not get the wastegate area, and from what you say might be unrepresentative?

john banks

397-1236 is the number you previously emailed me.





Do you just chop short the long probe?

Appears also to have only 1m of wire. Did you need to extend yours?

It also say diameter 1.5mm and then on the drawing 1mm?

Also it says this for the probes we already have:
"Type K- Nickel Chromium/Nickel Aluminium; Its temperature range is extended -200°C (up to 1100°C)." I am puzzled why this would not work for EGT?

[Edited by john banks - 4/5/2002 1:13:18 PM]

Cosie Convert

My mistake, I assumed that T uk and youself had the same charge temp probe that I have, it's only rated to 400/500 C region IIRC

The picture you post is the EGT I use (1.5mm) DON'T cut it
I bought a K type plug/socket (2 quid) and a roll of wire to lead it into the cockpit.

I have plenty wire so dont buy any, having said that, if your probe is suitable and has 2 m cable, you will not need an extension.

Which probe are you using ?

I'm at Crail on Sunday (trying to blag a shot of my old V8 beast )if you want to have another look at my set up. Or I'll be playing at my garage Saturday if you want to take a run across ?

Hopefully I'll not be rebuilding my engine tried 2 bar boost today with uprated fuel pump and plenty water/methanol injection. Yea mad I know but how else find the limit

john banks

363-0294 is the one we are using. Looking at the RS site this looks as though it may be OK?

I just want an estimate whilst setting up the car and I won't be permanently monitoring it - I don't think it will be stupid high, so I might try it just after the turbo - saves drilling holes and putting 25cm probes in unnatural orifices I am a doctor this sort of thing shouldn't freak me out but the temperatures are usually lower

Anyway, I am running 10 PSI less than you You are a Grade A nutter - good on ya.

john banks

I can't get the bolts off the downpipe and the gasket does not look like it will be friendly to thermocouple wiring. I think I'm just going to leave the EGT/knocklink business.

I'll just keep it at 19 PSI and not go higher. I'll setup the boost control so the ECU can make sure that held boost is not higher and then turn held down to 17-18 for the track with a peak of 19 and run lots of octane booster, and also not bother leaning out the mixture but leave it rich as it is. I am fairly happy with this as it doesn't feel like it is retarding (and it wasn't on the select monitor at only 1 PSI less on 2 RON less), I run 4 RON higher than it is mapped for safely running on and only 2.5 PSI extra held across the range with the benefit of a downpipe too. The ECU can pull plenty of timing and reduce the boost if it wants - AND IT IS STILL 10 PSI less than Cosie Convert

Reason being that there are big gains to be had in spool up and how long the boost holds. All it is is basically 2 turns of my actuator from the normal PPP setup with the same restrictor size.

There what a nice justification to myself. As they say though, my engine.

john banks

James I built the above on breadboard. I am puzzled by the results - any insights? The -0.02V offset disappears when you unplug the zener diode. Also the use of 4.3V zener to get this sort of effect seems odd. Using a 3.6V zener gave a -0.08V offset at atmospheric to achieve a -0.30V offset at 4.2V target boost.

john banks

The resistance of an unpowered MAP sensor is 11.6K between signal and ground and 2.5K between signal and 5V supply (disconnected).

If the current flow is only 2uA from what Paul says then the input impedance at the ECU must be over 1M ohm - ie basically like an op amp or a DVM.

Doing some research, it looks like the voltage output MAP sensors often have an op amp inside them. So we may not need any op amps at all.

We may just be able to use a zener diode and a variable resistor

Paul_H

Thanks John, but have you ever tried "jiggling" a 1mm drill bit? The words "snap" and "f***" spring to mind

Paul_H

Not being good at "jiggling" , I've ordered a drill set from Maplin - order code GU87U. 20 drills ranging from 0.3 to 1.6mm - seems made for the job.

Paul_H

You're sure that this one doesn't? there are several sets available. This one looked the most likely with 20 drills. Just my luck if it doesn't.