Hot start hunting

[lancelin]

I have a Griff 500 with canems ecu. I don't have an idle valve so use spark scatter which controls the idle perfectly after a while. The problem comes when the car is left for 10minutes after a long run. The engine starts but the revs hunt up and down between 250 and 800 rpm for a good 30 to 40 seconds until they eventually settle and normal idle continues. It's annoying and means I can't pull away for that period and the engine can stall. It doesn't happen when the engine is warming up or cold. It's always done it since the canems install and I've put up with it for years.

Any ideas really appreciated. I've tried varying after start enrichment but that doesn't help.

[lancelin]

Come on Canems users, I cant be the only one?

[spitfire4v8]

Thing is, no-one can really tell you what to do because we don't know what's causing the issue. Any info would be guesswork .. you're much better off either taking it whoever did the install, or learning yourself.
Also not many people know the canems system, but outside of the canems mappers chimpongas is probably your best bet as he's got a lot of experience

[lancelin]

Thanks, just wondering if anyone else with canems had this problem. I’ll not be taking back to the original installer. I’m in contact with chimpongas.

Thanks

[ChimpOnGas]

spitfire4v8 said:

Thing is, no-one can really tell you what to do because we don't know what's causing the issue. Any info would be guesswork .. you're much better off either taking it whoever did the install, or learning yourself.
Also not many people know the canems system, but outside of the canems mappers chimpongas is probably your best bet as he's got a lot of experience

^^THIS^^

Too many variables Owen, I've given you pointers away from the forum but my pointers always come with the caveat that I'd need to physically lay my hands on the car to make any real progress, I could quote loads of possibilities and as a minimum there are many tests we'd need to conduct before we even break out the laptop. For example, do you know your fuel pressure when the fuel rail is hot? if not we need to know this, there's a reason the Lucas deemed a fuel temp sensor necessary and fuel temp is not an input the Canems makes use of.

If you go to your doctor with chest pains he doesn't just guess and send you immediately for a heart bypass, he runs a myriad of tests before he makes his diagnosis. More specifically your doctor is looking for at least two (three is better) results form different tests that together combine to conclusively point him towards a correct and inarguable diagnosis.. Following these tests and in my chest pain example the problem could easily be proved to be nothing more life threatening or hard to correct than severe indigestion, if you found that out after having a full heart bypass you wouldn't be very happy with your doctor would you

But of course given the nature of your profession and area of expertise you know this already, actually no one I know is better equipped with the right thought processes and mental approach to support correct diagnostic practice than you mate! I believe this is because you and I were made, errr... 'Special' . In my case, and according to my wife who specialises in such matters professionally... I am definitely 'On the spectrum' as they say

More ideas on a Whatsapp message near you, but I am very reluctant to keep throwing ideas at you as ultimately just as Jules says...

spitfire4v8 said:

Thing is, no-one can really tell you what to do because we don't know what's causing the issue. Any info would be guesswork .. you're much better off either taking it whoever did the install, or learning yourself.

I was brought up on carbs and schooled on this discipline by a bunch of proper old heads who knew a thing or two I can tell you, I also had formal training on the Bosch K-Jetronic system which only goes to show my age. To be honest I've looked at MegaSquirt, MoTec and others but the Canems software has to be the easiest I've ever used.

Learning the Canems software is very straightforward and when you do it gives you the power to take control of your tuning which is empowering and exactly why I bought the system as at the time I made the switch we didn't even have Rovergauge. I distinctly remember the moment I realised only the mythical 14CUX Svengali Mark Adams could burn basic fuel maps, it was at this point I thought to myself.... "I'd be better off with a Webber here!"

To be honest and for all my grumblings of late the truth is Canems system was my TVR tuning salvation, it really is elegant in it's simplicity so no one with a Canems system should be afraid to get stuck in. However, before you do its super essential the car is in perfect health ie general mechanical condition, ignition components, electrically, fuel pressures, ect ect) or you'll just end up chasing your tail while endlessly tweaking features in the ECU software wintering why you're getting nowhere fast.

These days and with the advent of Rovergauge this is where we see the 14CUXers getting it wrong from time to time, the fact is we live in an age where we expect answers to just pop out of laptop screens so the temptation to skip all the fundamentals can be overpowering for some. My best advice is to say nine times out of ten the answer is not hiding inside the ECU, its something a good old bit of back to basics diagnostic work will quickly identify.

[lancelin]

Thanks Dave, I'll be checking fuel pressure next. We need a canems self help group setting up. I'm feeling the pressure.

[ChimpOnGas]

lancelin said:

Thanks Dave, I'll be checking fuel pressure next. We need a canems self help group setting up. I'm feeling the pressure

Many of the the aftermarket ECU makers do offer self help forums, just not Canems, I'm not convinced iit would help though and may even create a problem all of it's own. The truth is engine management is a very complex subject with infinitesimal reasons or combinations of reasons for faults, not least faults that actually have nothing to do with the ECU or something you can ever hope correct using your laptop.

Anyway, what you tend to see on any technical forum is someone pops up with a specific issue hoping for a magic built solution, this is closely followed by a host of well meaning contributors guessing at what it could be and giving advice (often conflicting advice) on what settings to change.To be honest it's a recipe for disaster and very soon the OP can find he's mapped himself into a situational where the car runs worse than if he'd never touched his laptop, at this point he may also have lost track of what he's done to get himself in such a pickle.

Of course you can always reverse out by re-uploading your original un-messed with map (if you saved it), but as one element of change alters another and layering different feature changes can disguise the one thing that could have helped, it's advisable to adopt a policy of just changing one element at a time then undoing it if it failed to solve the issue.

Back to hot/warm start correction if I were you I'd start with a fuel pressure test when hot and look for vaporisation in the rail, keep in mind Lucas didn't fit that fuel temp sender for fun. Saturated petrol injectors like a nice solid column of fuel, they dont function very well with gas so if the fuel is boiling in the rail this can be a real issue especially when cranking and starting a hot engine. As we know our fuel system is a feed & return loop and your petrol tank is a giant heat sink within this circuit, so if the car stumbles into life on a hot start and runs like crapola but clears itself after 20 seconds it may be because new cooler fuel has just arrived at the injectors.

If this is indeed your issue the condition can be greatly improved by increasing your cranking correction, unlike after start which is fixed setting 'cranking correction' references coolant temp so while not perfect (fuel temp would be better) it will at least allow you to experiment with adding more (or less) fuel when the engine is hot starting.

Try this link as PH won't let me upload an image right now?

https://ibb.co/myLvHmw

But as Jules quite rightly says.... it's all guess work really... so I'll stop right there!

[Classic Chim]

Who installed and mapped the car?
Why can’t you take it back to them as surely they have the experience to find this fault?

You say it’s done this all along which I find rather shocking considering the cost of install of after market Ecu.

Why would the fuel start boiling in the rail since an Ecu install?

[cinquecento]

I had the same problem on my megasquirted Griff.

After a hot start, the after start enrichment lasted a relatively short time..by extending this to about 30 seconds, this delayed the transistion to no enrichment. So I'm not changing the amount of extra fuel..just extending the time it fades to zero.

I think a heat soaked engine needs a longer transition to its idle AFR

Don't know Canems but you could try that..backup you current config so if things turn pear shaped you can reverse your changes.

Good luck

[lancelin]

Thanks, I’ll try extending the pre start enrichment. The install is out of warranty now and the installer is too far away. Lesson learnt.

[lancelin]

Hey cinquecento, thanks for the tip. My hot start hunting is now fixed by increasing the after start enrichment to 35% for 200revs. All good now. The original settings were 15% for 100revs. Also thanks to Dave. These posts do work occasionally.

[ianwayne]

Only just noticed this thread, the title didn't lend me to think it was about canems! I have it fitted to my Chimaera by a previous owner. I can plug my laptop into it and read off the settings, sensor readings, idle speed settings, idle control duty cycles etc, but this 'enrichment after start' is a new one on me. I wasn't aware of it at all.

Mine sometimes is slow to pick up on a hot start but usually only takes a few seconds to settle at 950 rpm (or whatever I set it to)

[ChimpOnGas]

I've spent the last four years deep diving the Canems system, mine operates two different fuel types so effectively requires mapping twice. I have some experience with MegaSquirt which is a very feature rich system but sometimes more is not better as it just gives you more opportunity to to screw things up.

For the amateur home mapper the Canems system has all you need, like any after market engine management system there's still plenty of opportunity to map yourself into trouble as there are still a large array of features to ensure a good result. As after market engine management systems go there's nothing I've seen to beat the simplicity of the Canems highly intuitive software, this ensures you can get excellent results without spending a fortune having a professional map the car.

If you have an after market engine management system, before even considering opening up the software its essential you understand the working principles of a four stroke engine. My background in carburetor and distributor tuning has certainly proved invaluable as it's important to accept all the fundamental principles of ignition timing and what we used to call mixtures (AFRs) are of course exactly the same with carbs and distributors as they are with distributor less ignition stems and fuel injection.

When I bought my Chimaera I distinctly remember the moment of disappointment when I realized I couldn't really effectively tune my fueling on the Lucas 14CUX system, at the time I gave serious consideration to the argument I would be better off on a carb!

I'm super fussy about how my cars run and to be honest when I bought my Chimaera 10 years ago I felt my well maintained 30,000 Chimaera had a number of undesirable characteristics operating that I simply couldn't address in the way I am used to when tuning a carb on the good old principles of engine sound, exhaust smell, plug colour ect ect.... with a bit of help from a good dial back timing light and a basic vacuum gauge thrown it.

I'd recommend anyone with carb tuning experience who enjoys the process of correctly setting up an engine to take their tuning skills to the next level by installing an after market ECU, and the Camems system is an ideal place to start as the software really has been very well conceived, it's what I would refer to as elegant in it's simplicity.

Saying that my new thing is proving you can get excellent results from the 14CUX, a good basic setup here is key along with a few little tricks like,,,,,, ditching the dreadful restrictive catalytic converters, getting the base idle right, setting up the TPS, making sure the fuel pressure is correct, sorting the sometimes poor engine earthing, making sure there are no ignition related misfires, switching the distributor vacuum advance to full vacuum, sorting out the idle air control system and the overly aggressive crankcase breather setup ect ect ect all of which can all yield fantastic improvements.

It's all good fun proving you can make a standard Chimaera run better for peanuts, but would I personally ever go back to a distributor and the 14CUX?........ No chance

[ianwayne]

Checked my Canems settings on 'after start enrichment' today and mine is set to +15% for only 30 revs. Basically negligible.

But how does the system know the engine has actually started? I presume its by engine speed over a threshold because there is no feedback from the ignition key position as far as I can see.

[N7GTX]

Don't know the canems system but some use the crank sensor and others the alternator which gives a 'run' signal.

[ChimpOnGas]

ianwayne said:

Checked my Canems settings on 'after start enrichment' today and mine is set to +15% for only 30 revs. Basically negligible.

But how does the system know the engine has actually started? I presume its by engine speed over a threshold because there is no feedback from the ignition key position as far as I can see.

Crank sensor Owen.

You can choose the engine speed the ECU transitions from 'cranking mode' to 'engine running' within your cranking settings like this:



In the above example as soon as engine speed exceeds 150 rpm the ECU will come out of 'cranking mode' and will tradition to 'engine running', IE the engine speed you transition from your 'cranking mixture' settings to your 'after start' settings.



Be aware you'll need to crank the engine for a good second or two before the ECU recognises the signal from the crank sensor, and the ECU will not activate the coil packs until it sees a crank signal which is why you will never enjoy the instant starts even a basic carb fed engine can give.

The engine management system on your everyday car does not have this delay, indeed in my experience all OEM engine management systems since the advent of crank sensors have always found their crank signal pretty much instantly. But all the after market ECUs typically fitted to our cars seem to exhibit it the delay, in the world of engine management they are all very very basic systems after all.

[ianwayne]

Now I know why I don't get that 'first turn of the key' starting that is often bandied about, especially when it comes to classic cars. I have a carb fed motorbike that does, but nothing else.

I've adjusted my 'after start enrichment' from 15% and 30 revs to 20% and 100 revs. I have a slight stutter / very low idle speed for a second on starting sometimes (usually when hot) so this should assist in eliminating it.

My cranking mode RPM has been set to 300 rpm, presumably at installation.

[ChimpOnGas]

ianwayne said:

Now I know why I don't get that 'first turn of the key' starting that is often bandied about, especially when it comes to classic cars. I have a carb fed motorbike that does, but nothing else.

I've adjusted my 'after start enrichment' from 15% and 30 revs to 20% and 100 revs. I have a slight stutter / very low idle speed for a second on starting sometimes (usually when hot) so this should assist in eliminating it.

My cranking mode RPM has been set to 300 rpm, presumably at installation.

My EXAMPLE of 150rpm is not necessarily correct for your car Ian, it's just an example and the installers choice of 300rpm is not necessarily wrong. Keep in mind you don't want the ECU to come out of cranking mode and transition into after start enrichment too early and the Rover V8 typically cranks around 250rpm so 300rpm is safe threshold as anything over 300rpm figure is clearly a running engine.

Do also keep in mind the amount of air introduced under cranking has a huge influence, which is one of the reasons I removed my idle air control valve, fitting a manual extra air valve very quickly teaches you exactly what the engine really wants in the way of air under cranking and during warm up. I'm afraid I lost faith in my Canems controlled PWM idle valve, fitting a vacuum gauge to it proved the thing was unstable and the software wasn't always showing it's true behavior, trying to tune like that is impossible so I replaced the pattern part fake Bosch idle valve fitted by he installers with a manual system of my own design.

This simple manual setup along with the vacuum gauge test both proved my theory the ECU controlled PWM system was unstable and so unpredictable in it's behavior, and there's nothing more conclusive than running some tests based on how far in or out my manual idle valve knob is set. These tests helped reveal a number of interesting facts about what a Rover V8 in a Chimaera really wants and more important doesn't want in the way of extra air during cold start cranking, warm up, and hot start cranking.

Armed with all this evidence I conclusively proved without any doubt the unstable fake Bosch PWM idle air control valve had for a long time been the enemy of all my attempts to tune my engine correctly, this was especially true of idle and low speed drivability tuning as it is quite clear the plenum arrangement we have makes the a Rover V8 engine unusually sensitive to changes in air ingress (or we what I would call a vacuum leak).

Lets not lose sight of the fact that an idle air control valve is just an ECU managed vacuum leak and to be 100% clear the plenum arrangement we have is not a setup that responds well to or even needs closed loop idle management via the variable introduction of extra air, the sensitivity is such that I can now see why Chimaeras tend to run so badly if there are any issues whatsoever with the stepper motor.

Given what I've learned if I was designing an ECU managed extra air valve system for this engine I would not be using a PWM rotary idle valve, I would be copying the Magneti Marelli stepper motor system Jules uses on his Emerald installations as my guess is he (or the tech at Emerald) worked all this out long before I did

[lancelin]

My canems idle was terrible with the PWM air control valve! It ended up as a really unstable control. My idle is now running purely off the main butterfly adjustment. I don’t even have spark scatter enabled. For cold starts I’m using an extra air valve solenoid attached to the side of the plenum to let a fixed amount of air in when cold. I switch the valve manually via a relay when engine has reached 50 degrees and she sits perfectly at 850rpm. I could use a temperature controlled switch.