The Roadster NA Journey Begins

[mrpham]

[gslender]

For my build would batch fire be better than sequential considering I have no regard for fuel economy or being able to drive it below 5,000 RPM? I owned 2 stroke road bikes in my youth Plus I have no knowledge or understanding the tuning process of a car. I will however google sequential/batch tuning whilst at work. For the record my car is tuned via TPS not AFR's.

The CAS would be for sequential injection and/or spark fire. Ice88 mentioned all the spark reasons but there is also a few reasons to consider sequential fuel (which is what I run using a MS3 Pro and have zero issues with a very old NA6 CAS using stock harness with the max RPM at 8,000) - the main reasons would be for fuel delivery at idle. Having big injectors and small PW at idle can be tricky if all injector ports are being fired at once. Also a challenge for idle exists if that port is big and has low air velocity. Another reason for sequential is fuel economy. I did sequential because I could, and because the MS3 has 12 spark and fuel outputs... so it seemed wasted to just use batch. But hey, if you are "100% Because Race Car" then ignore that and stick to batch fire. Ditch the CAS and be done with it....

One more thing to try, is if you've got that scope, is stick it on the CAS signal wires at the ECU - take a pic of the signal at idle, and then again at 7000rpm (if you're happy with free revving that high). Then compare the signal and it should show any creeping noise, bad shape or potential electrical issue that might appear more aggressively under different conditions - eg when temp rises and resistances change etc. Even a poor connection will normally show as crumbling of the signal at various times. What you want to see is a nice solid and clear signal.... at idle and at whatever max rpm you dare to test on.

That's what I would do, but then again, I did all my work myself so probably seems easy from my point of view.... so maybe ask the guys at Plus to at least consider checking things with diagnostic scopes as just replacing stuff randomly isn't a cheap way for you to fix this (unless they're doing all this for free).

G

[Magpie]

Thanks for the explanation G. I could set the scope up in the car with a 240v inverter power source and take it for a drive, I only need to go above 6,000 to get the issue. Depending on Saturday I could do this on the Sunday, other half/family dependant... Changing to batch maybe a solution it is not as if it is a real daily drive But again why loose the benefits of sequential...

Over doing change for change sake, being very methodical about this issue. Matt from Haltech is also providing advice so hopefully there is enough brains working on the issue. As stated Morgan Park will be used to isolate the ECU and try and replicate the issue on another ECU.

After Morgan Park is Noosa Hill climb so the information from Morgan Park will be used to make the decision for the Noosa Hill climb. After this there is no more events planned for 2015.

[gslender]

Thanks for the explanation G. I could set the scope up in the car with a 240v inverter power source and take it for a drive, I only need to go above 6,000 to get the issue.

I'd start off just doing a free rev in the driveway with the scope on the 240V from home... and if nothing is seen, then think about an inverter etc. I have a USB scope for laptop etc, but you'll probably get to a solution before we meet/catch up etc.... but if you ever need it, I can leave it with you as I don't use it that frequently.

G

[Magpie]

Thanks for the offer G. Mine spends more time packed away than on the bench as well

[MattR]

Mark, if the ecu swap solves the problem then I would say that is your answer, you have used too many CAS's and changed the wiring for it to be anything else if the issue is solved.

Personally, if the swap works, then happy days and just drive the ring off the thing at Morgan Park and Noosa and then worry about the whys and wherefores when you have plenty of time to sort it and no pressure on yourself to be ready for the next event.

ECU's do break and it could be something as simple as a dry joint in the box. I don't know how many TV's my dad fixed by finding dry joints when he had his business in the 70's early 80's and even with the technology used to solder joints now they still happen.

[tbro]

HEY!!!!!!!

After reading all this, my head hurts, so much technical humdum.

Stick to basics,KISS, You've changed parts and made no difference, two things you haven't changed
1/ ECU
2/ Wiring.

No 1 can and will be a pain in the arse, your going to need to retune said spare ecu because doesn't matter how much someone says
that you can download and reload to new ecu, I don't think so.

No2, Multimeter, make up nice long leads and go for it. Check resistance from ecu( not plug ) to any connectors, through front and backfed and
then to the sensor. Check every wire, not just the ones you think might be the problem do all of them. Its very rare to find manufactured plugs not to be
seating properly BUT it does happen, so even though its an absolute arsehole of a job you need to start at the beginning and work your way through,
and you WILL need assistance and if you need it just ask. Do you soldier all of your joints????? that can and does at times cause issues, so as I say,
if you want help just ask. The other thing I was thinking, do all your sensors that runs to your dash and logging stuff and all the other stuff that
you have wired into the car, does anything run with or parellel to the wiring for the ecu. The reasoning behind this is your only having troubles when
running the car at max loads, and this is when your playing/using all the other stuff you've put in. Are you running radios, unshielded aerial leads or wiring
for the radio. These have caused issues way back but you've fitted a lot more extra "stuff" than most people who track or race their cars.Have you or anyone else probed through the wiring sheath to test voltage or resistance at any time??? this can open up a whole can of worms as well, make and break wiring under heat or heavy load conditions.

The main thing that has me stumped is that the amount of Mxs race cars in qld with haltec ecus and no one has heard of this issues with sensors so
maybe as Nick said, you maybe chasing ghost why the real devil is having fun at your expense .
T

[Magpie]

http://members.rennlist.org/951_racerx/SequentialVsBatchFiring.pdf

FUEL-DELIVERY AT HIGH-RPM
Under high-RPM operation, the fuel-injectors have longer duty-cycle periods. At redline, they are close to their maximum capacity and the differences in fuel-delivery is only 20% for a complete 720-degree 4-stroke engine cycle .

Another interesting tidbit is that the sequentially-fired injectors spend just as much time firing fuel at the back of a closed intake-valve as the batch-fired arrangement.

CONCLUSION AND DISCUSSION
Upon viewing a graphical display of the fuel-injector duty-cycles, one can see that the two methods of fuel delivery are not all that different. At low-RPM operation, the volume of fuel metered is minimal given the time available that these two systems have identical performance. At high-RPM operation near redline (where maximum-power is generated), the two systems are even more similar in fuel-delivery characteristics.

The only difference is really at which time during the closed-intake period to squirt fuel at the back of the intake-valve. Therefore, we can conclude that the differences in maximum power output is similar as well. This is supported in real-world cases of minimal differences.

The last scenario is not often used due inefficiencies in controlling the injectors at idle and low-RPM operations (because of minimum injector duty-cycle). High-RPM operation is also compromized because double the fuel has to mix with the same volume of air flowed making atomization difficult. Race cars that employ this configuration have resorted to pre-heating the fuel prior to injection and some even aim the injectors upstream to face the full brunt force of the incoming air for violent turbulence and maximum vaoprization.

These factors (and others) are probably the reason the majority of fuel-injection systems use batch-fired or semi-batch-fired fuel-injection(pairs staggered 360-degrees).

[Steampunk]

Eeeep... don't go complicating things by thinking it's OTHER things. Eliminate one thing at a time, then move on to other components once you are 100% satisfied.

As with injector duty cycle, you do know, and I surely hope that many people have told you, that maximum "safe" duty cycle is 85% of injector capacity right? so is that what the Haltech display shows? The car will still run fine over 85%, and you won't feel any detrimental effects, but not at sustained periods.

[Magpie]

It is just me trying to learn more about tuning. Taking the cam angle sensor out of the equation (as suggested by others) requires batch injector firing so I need to understand what this requires. Are there are advantages/disadvantages to going to batch.

My injectors reached about 65% duty cycle at WTAC in sequential mode, not sure if there is enough headroom in there for batch... again google (and the forum) are my friends.

No chance of doing more than one change at a time, just me thinking ahead. Having a backup plan...

[MattR]

Mark, once you have sorted the miss fire then move onto fuel delivery.

However as a comment on your post, in your application, and 99% of everyone else here whether you use batch or sequential firing for the injectors will make bugger all difference.

Get the miss sorted first using KISS.

You said that you are swapping another ECU, then if this solves the problem, the fault is either ECU or conectors. Get through track day and then Noosa if it works with the alternate ECU, have fun with the car and then get the full problem sorted once you and everyone else working on the issue has the time to do everything right without being under the pressure of a tight deadline.

As I said, when you find the fault, it will be a "doh" moment and I reckon something very simple that just got missed.

Don't overthink things.

[Magpie]

MattR this hurts, but I agree

My nature to have a backup plan just in case. There is a reason why I always score in the high Machs range!

[speed]

Hi Mark, firstly, apologies for not being able to make it to wtac and come chat.

I also often over think things and want a backup plan. Problem is we become dangerous when we don't have the complete knowledge and understanding which can lead us off on a tangent.

One thing at a time, so you can properly cross each issue off the list.

The good thing is that you have the support of other forumites

[Magpie]

Thanks Speed. Trying to stay objective is hard when your too involved. Having other people's thoughts/suggestions really does help.

I have a plan, (subject to rapid change)
1. Run car with swapped in PS1000 computer at Morgan Park. Collect data requested by Matt from Haltech and send to him/Automotive Plus on Sunday.
a. If fault develops try the zip tie method.
b. If fault does not develop swap in a previously failed cam angle sensor
2. If zip tie method works (1a), scratch head then thrash the hell out of the car.
3. If swapped in sensor works (1b) then thrash the hell out of the car and it is a computer issue
4. If the swapped in sensor fails (1b), insert new OEM sensor and thrash the hell out of the car as it is not a computer issue. When/If sensor fails put in another (rinse and repeat)
5. If 3 - leave computer installed
6. If 2 or 4 - insert Haltech sensor and re-test before Nossa Hill Climb

[madjak]

I'm running the old NA6 optical CAS with a haltech PS1000. When I first set it up I had issues with missing and thought it was the CAS but since I had no replacement I debugged other things first. By chance I figured out it was the COPs being bolted down to tight causing a missfire somehow. I only figured it out by chance as I was lazy and didn't bolt them down when switching coil packs. It was doing something similar... missing when hot and at revs but running fine when cold.

With the ECU, try changing the input to the second trigger line and switching the input in the ECU. That way you can make sure it's not one of the circuits in the ECU faulting.

With the Hall effects sensors, they really need to be mounted close, square and solidly so there is no vibration. On my dad's mini we had all sorts of problems getting the crank sensor to read cleanly. Probably didn't help that it sits right next to the alternator but in the end it got mounted very close (like 1mm clearance) to the toothed wheel and it now works fine.

Not sure what else it could be... I hate these sort of issues. They are the most frustrating ones to fix.