Calling all MS people...

[V8 Freak]

Fridge....

I'll take anything to look at and learn from.....

I'm thinking of making up a timing table based on what some people have already done with "similar" engines and seeing what it runs like, but I'm not going to touch the fuel map even though it may be overfuelling.

I'll have a go at extrapolating the timing settings from one table to another and see if I can then run from what I believe the master timing setting to be. (I'll set them up on Excel and see what the shape is like before I run the engine..)

I'll get a proffessional to l look at the fuel maps... I have no oxygen sensors attached presently so I don't want to head into the world of supreme guessing and cook my engine.

If the timing map is pants, I can always back out to the current working map.

Does MS have voltage compensations for the injectors, or does anyone have a voltage compensation table or details on the injectors used int he RV8? I've got the green striped variant.

Now starting much easier when cold, needs nursing for a few seconds but then looks after itself quite well. So would like to check that I'm getting enough fuel in there while cranking and low voltages etc.

Does MS have a set of cranking settings ?

Also... (I know this is starting to ramble...) The fuel (VE) maps in MS.. Are these actual time the injectors are firing fuel in milliseconds or do they relate to another injector setting in any way ?

All this comparing systems is a big learning curve but keeping the old grey matter strirring....

Neil

(Mmm.... Oxygen sensors..... )

[Hybrid_From_Hell]

Neil,

I have been having a good look at your Spark table, and had a good long thinky or 4.

There are a couple a variables as I see it which are causuing us to have a big prob, these are the "unknowns" :

• The original Position of the VR sensor, ...when you 'whacked it' it moved from where it was to were it is now - after you 'whacked' it back - and it would SEEMto not be the same
  
• This means the base setting is out, but unsure as to how much, but its gone "soft" as the other way would be over adavnanced, so thats one thing maybe.
  
• Everything else is as it was, the cam timing, the engine build, whilst some builders do "Degree in a cam" doesn't really at this point matter - as if you hadn't of accidendly whacked it none of this would potentially be needed ?. As such for the moment don't worry about the cam and how its set / what it is, however if we can find out (often they are stamped one the nose with the number) this may be useful, as I have reservations re the state of quality of the tune / spark map.#
  
• The only thing really we should be tinkering with are setting around the spark map, it doesn't matter how much out the spark map is, the fuel map is independant and therefore is unaltered by you having clouted the VR sensor, once the spark settings are back to what they should be then the fuel map should rematch the revised position of the spark table
  

.

Hmmmm, and heres my last concern - I am really uncomfortable with the spark table generally. shoving -30 as a spark cut off for the ignition is a bad idea, I tried this originally on the Megajolt I just set to 10 degrees, and Mark Adams comment was whilst he fully understood why and what I was trying to do having a High RPM engine on its limits suddenly in a nanosecond having a HUGE cahnge in adavnce was "Not good for its long term health" and that it should be done via cutting the spark as oppossed to shunting massively down the range.

As such looking at the table and its contents and then the -30 bit I would question just how good this MAP was when done ?. It to me doesn't smack of a quality map, that just needs the base setting at the VR sensor sorted to bring back a beautifully tunned engine ?

So, I see a way forward as folows :

Forget for the moment everything except the base setting.

Plan.

1st is I think to ensure that the TDC Marker is at TDC, here is a farily quick and dirty way of gaining TDC accurately without removing the heads a la dial guage best way

Disenge the battery so engine dead.

Get an old spark plug, weld on (best) or / arladite on BIG TIME a small - say 20mm lump of thick rod with a flat bottom and edges removed (bench grinder)

Remove all 8 plugs - Screw the extebnded plug in carefully to No 1.- and then GENTLY turn the engine clockwise by hand until it GENTLY jams on the pistion

The MARK the pulley with a line on the TDC Marked. Now revolve the engine the opposite way - remark the Pulley when it rejams. Remove plug, put all 8 back it

The 2 marks on the pulley - the middle position is true TDC - does this match what you thought is was pre doing this ?

Now we have TDC.

Take a datum reading of the VR sensor as it is now, then on paper write down the sets to incarse the advance of the base setting in small increments.

I would then suggest going up in 3 steps at a time, then back 1 step, you should find that 3 steps offers a significant difference to feel and power, and that it the step of 3 is too much then there is too mauch adavance over the entire MAP (your only playing with the base setting this affects EVERY Map cell the same variable) if this is the case the OVER adavnce will give misfires and or poorer perfomance, as max power reduces if the advance is too highj, this way up 3 then compare with back 1 if going back 1 feels better then the 3 step was too much, if back one seems to be porrer then the 3rd was maybe not enough, up another 3 and compare with a step of back 1 etc. This is why you will need to have the steps written down, and do it methodically and use the same road for comparrions.

When you get to a point where you are unconvinced that the back one has any difference for saftey back another 1 this should then still be under the max advance. Crude but effecyive.

This should put you spark map back to where it maybe was, it would then be interesting to compare with where you are now, but do record and save this, in effect if you had this now then you could just reset it today. Lastly I have heard that tuners like to protect their owrk, so what they do is to deleiberately set the base wrong. ie for a simple example lets say that you have a engine that will work best at 30 degrees advance. that is 30 degrees BTDC, and the key here is TDC, if you have this info then its easy to reset if you ever need, but what some tuners do is change the TDC point they say work off 4 degrees BTDC, and set at 26 degrees, everyone assumes that the setting on the map of 26 degrees is for TDC, but here its not the base is 4 BTDC, maybe this was done to yours deleiberatley ?

At the end of the day if you keep the setting recorded you have now you can always gop backwards

Lastly even with the above sorted I belive the MAP is not that clever, so there is another option, Mark Adams knows more about V8s and tunning than most others will ever forget, He also is familair with Emerald, so for ££s and a rolling road and his time you could get this resolved - but its not a cheap exercise

HTH

Nige

[V8 Freak]

I was reading the stuff above the quote and nodding... Not sure about sticking something in the bore without being sure I won't lose it though ! May have to think about that... I understand the principle fine though.

Lastly even with the above sorted I believe the MAP is not that clever, so there is another option, Mark Adams knows more about V8s and tunning than most others will ever forget, He also is familair with Emerald, so for ££s and a rolling road and his time you could get this resolved - but its not a cheap exercise

If all "reasonable" attempts to understand the timing concerns fail I was considering an expert as mentioned in my post.... But do I have to switch to Emerald for Mark to do it ?

(I've still got an Omex 710)

(And I'm smiling because I know you are really trying to help me here..)

I think I'll do whatever I can do check TDC this weekend without risking losing something inside the cylinder... I'll also see if there is a way I can figure out approx. where the master timing should be based on counting teeth and centre position of the sensor versus the falling edge.

You never know.. Might get me within a degree and help to confirm current setting is near....

Regards the -30's in the spark map.... I've taken those out those in the middle. Like Ian said, it's going to be a bit of a shock for the engine if I hit one of those cells. I've put in some numbers that don't look out of place when looking at the 3D graph of the map.

I've also changed the two that could have been rev limiters and used the correct function to set the soft limit to 5200 and hard limit to 5500. I doubt I'll ever go there but better to be sure for now.

I can see that a programmer might want to protect their work. If that's the case, then paying for some time with someone like Mark might be not only the best way to go, but one of the very few ways to go.

For now I'd just like it running and not killing itself so I can at least get about when muddy / wet after walkng the dog etc.

Neil

[TOR4x4]

Sorry that you feel you are still having problems,

I would first of all check the setting of the crank sensor, gap and position to centre of gear wheel, the temp sensor was calibrated, are you sure you are plugged into the correct one?

The engine has allways needed nursing for the first 5 seconds or so, after that it should be ok.

The engine was mapped with the breif of making it a safe map, the -30's around 6800rpm mark should never ever get used,so therefore why bother mapping that area, 6800 rpm with no load :

The others in the middle'ish of the map i don't know about.

I never noticed any misfires, but maybe it went through them cells to quickly to notice.

I think you need to try and set the master timing by what ever method you feel best. It was set origonally by the mark on the front pulley, the numbers in reallity are irrelevant, they are all relative from a point that was used on the day,

The cam timing is set to 0 degs with duplex timing gear, no verniers.

The Ultimate big valve heads may loose you a little bit of torque, but it gains a lot at the top end, in a car that weighs ~1400 kg's and doesn't spend all day doing 800 rpm i thought that was the best choice, but i'm sure you all know better.

Stick with the Omex, can't believe anybody would get rid of that in favour of MS.

I'll dig out the old laptop with the maps on and email them to you.

[FridgeFreezer]

Stick with the Omex, can't believe anybody would get rid of that in favour of MS.

That's funny 'cos I was going to say by the time you've paid Mark Adams to tune the thing on a rolling road you could've fitted MS, downloaded my fuel & spark maps to it and then run the auto-tune routine a couple of times.

Not knocking Omex, or Emerald, but I've yet to see either of them do anything that MS can't.

Edited to add: Jeebus, I've just seen the price of the Omex 710, you could buy three MS ECU's for that.

[Hybrid_From_Hell]

Somw very usefull stuff Mr POD

Sorry that you feel you are still having problems,

(So Pod, wots the warranty then )

I would first of all check the setting of the crank sensor, gap and position to centre of gear wheel, the temp sensor was calibrated, are you sure you are plugged into the correct one?

(Not as daft as it sounds, prob your right but definately worth a check, we've all done seriously daft things in the past....well, I definately have )

The engine has allways needed nursing for the first 5 seconds or so, after that it should be ok.

Does it have any sort of Cold start unit, ie Extra Air Valve ?...most race engines don't as really no need?...prob not too tricky to add later if really needed )

The engine was mapped with the breif of making it a safe map, the -30's around 6800rpm mark should never ever get used,so therefore why bother mapping that area, 6800 rpm with no load :

The others in the middle'ish of the map i don't know about.

(Yep, This is odd, I noticed them, can't work it out, also the steps in the advance doesn't seem steady and they go up and then later down, most odd but it obvioulsy all worked more than fine, its just possible that if it was a tad hit and miss more could be gained....)

I never noticed any misfires, but maybe it went through them cells to quickly to notice.

(Yep you could be through almost jumping vertcially and diagnolly at the same time, could maybe bypass them ! - if not with foot doing the 2Mr Stampy" method, it would be a fast visit through them)

I think you need to try and set the master timing by what ever method you feel best. It was set origonally by the mark on the front pulley, the numbers in reallity are irrelevant, they are all relative from a point that was used on the day,

(THAT is useful, worth resetting on that basis alone as a base point to start from trhe "Mark" you mention - Mark Adams - doubt it..... but have to ask ?????)

The cam timing is set to 0 degs with duplex timing gear, no verniers.

(Thank God - I have a vernier set of gears on mine - mit a blob of weld I spoke to JE he said "Yep - to stop idiots like you Nige ever taking tham apart and finding you can't get it to run again never a true word - cleaned it and weld let alone )

The Ultimate big valve heads may loose you a little bit of torque, but it gains a lot at the top end, in a car that weighs ~1400 kg's and doesn't spend all day doing 800 rpm i thought that was the best choice, but i'm sure you all know better.

(Big Valve heads may loose a tad of torque, but of a big bore engine like this the effect is massively reduced, to the point where the benifit gives more Uuumph than the small loss - in real terms it will feel more powerful even at low RPM)

Stick with the Omex, can't believe anybody would get rid of that in favour of MS.

(Come here - 'smack' - now go away, at least you didn't mention the "D" word )

I'll dig out the old laptop with the maps on and email them to you.

(also useful too to compare)

[Bull Bar Cowboy]

Hello Adrian…………………..good of you to come in with your 10 penny worth ……… so what are you building as a replacement ?

I was working on the basis that it always worked well enough for you, so it should be OK……………..yes I have seen the videos……………

The loss of low end torque with big valve heads is arguable ……………. The low end torque is also significantly effected by cam and the exhaust system design. So whilst the loss of torque may be very noticeable with a high overlap cam designed to push the power band higher in the rev range ……….. the loss of torque with a milder cam be not be so noticeable, and could probably be compensated for in exhaust design ……….

I was guessing that the cam would be zero …………..applications that require other than this are usually reserved for standing quarters and circuit racing………….

My original thoughts were that the engine would never see 6800rpm ………. unless you are going down a f’kin steep hill in Low 1st ………….. so I was assuming that these cells were never mapped………..

As I said above, my only critique of the timing map was the lower rpm settings ……….. I would have expected to see a tad more advance ……………..also the WOT could maybe do with another couple of degrees but that’s just being fussy……..

Omex was originally developed for race cars ………… that why it has features like 14x21 tables (for fussy engines, and the computing time is quicker), voltage compensation for the injectors (not particularly an issue with the Bosch units), triple fuel maps with individual injector trims for balance, voltage compensation for the coils and very fine settings for both TPS and MAP functions……………

At the end of the day, there is no real difference between any the systems once they are correctly set up. Granted……. some are more unfriendly to manipulate that others, but you should always end up with the same result ……………….a spark table that is MBT (Minimum Best Timing) …………. this is the minimum amount of advance that gives maximum torque………..and a fuel table that provides the correct Lambda right across the rpm / load range ………… generally this will be 12:1 to 13:1 AFR at high load and 14:7 at cruise and low load……………..the idle cells are adjusted for any given engine combination to produce the most stable idle together with emissions that are acceptable……….. for an RV8 this will generally be 13:1 to 13.5:1 AFR.

I would say, stick with it and learn the Omex foibles ………….. It would be a shed load of work and a steep learning curve to go over to MS / EDIS…………

The principles of engine tuning remain the same for both………………. And the final outcome from both systems would (or should) be identical………

Ian

[V8 Freak]

Thanks for jumping back in and helping Adrian....

I don't feel like I have "problems".. More thinking of them as opportunities.

I'm not after warranties (Slaps Nige for suggesting such... ) so no worries there.

I'll have another check of the crank sensor when I next get to play with the car in daylight. It's telling the ECU to give out a spark and the engine running smooth once warmed up so I think it's doing it's job, just not maybe in the same position it was when originally installed by you, and hence my desire to make sure the master timing is bang on.. Then it should be happy on everything else that you had set up. (Except the -30's of course)

Regards the numbers reflecting the timing as it was on the day the tuning was done.... If it was not set as the Omex manual suggests then I could clearly be looking for a totally different master timing number than the whole system is expecting. Thus, pure guessing could get me a more accurate position when compared to the application of science and timing light.

Not the best place to be in as I'll never have a truly scientific way of ensuring things are in the right place if anything needs to be dismantled etc. Hey ho.... Guess work it will be !

If you have any old calibrations that will be fantastic... Any other reference points will help me....

I've spoken to Chris at RPi and he can find no record of the sale, so we know nothing more about the cam and I'm not going to pull the front off to look for a potential stamp on it !

It's going to be either Torque Max or RP4 so how different are they ??

Regards the choice of heads, they are great.. Loads of extra springs, mahoosive ports and what is this torque thing.. Not sure I'm going to notice any small losses I didn't have in the first place! Revs will always sound better than torques in my books !

I'll be sticking with Omex primarily because I already have it, it's installed, I have a loom, it's working and it has options to grow....

Can't do the "auto tune" stuff like MS but if I add a lambda sensor or two I can at least tell it what my target mixture is.. More fun to be had I recon !

Bring it on.. Lets get this baby sorted out....

Neil

[FridgeFreezer]

if I add a lambda sensor or two I can at least tell it what my target mixture is..

You'll need a wideband lambda for that, just to be clear.

[V8 Freak]

You'll need a wideband lambda for that, just to be clear.

Can I get away with one strategically placed after the pipes merge into one in the exhaust ? Or do I have to fit 17 or so like Nige did ?

Do they have to be the heated jobbies or can I be a cheapskate and go for the simple single wire version?

Neil

[FridgeFreezer]

Can I get away with one strategically placed after the pipes merge into one in the exhaust ? Or do I have to fit 17 or so like Nige did ?

Do they have to be the heated jobbies or can I be a cheapskate and go for the simple single wire version?

One after the Y will be fine, that's what I've done. You only need them per-bank if you're going to be tuning per-bank which is more involved than I can be bothered with quite frankly - it's a slippery slope to trying to trim each cylinder

I would go for heated (3-wire or 4-wire) in a narrowband one, just take the heater feed form the fuel pump feed, they don't draw much.

All wideband ones are heated anyway so there's no getting away from that, you need the sensor & controller to run wideband. Innovate & TechEdge are good VFM.

[V8 Freak]

Ok.. Wideband and will be heated.... No probs so far.

Why do I need a controller ? Do these thnigs not just get attached to the ECU ? (Sorry but new territory here..)

Neil

[FridgeFreezer]

Please note this is the mickey-mouse version and the real explanation is far more complicated and accurate: Wideband sensors are much cleverer than narrow-band, they are actually sort of two narrowbands in one - one in the exhaust and one exposed to air. The controller pumps current about the place to balance the readings of the two, the amount of current it's pumping to keep the thing in balance tells it what the AFR is, which it then outputs as a voltage for the ECU to read.

I'm sure the MegaManual / Wikipedia / Innovate website will tell you more.

[V8 Freak]

Becoming clearer.... Would I have to slap in a separate air sensor / air temp sensor? or do these have separate sensors built in and sample from within the exhaust gasses and externally all in one unit ?

Looks like me got loads more reading to do yet..... Tackle the basic timing concerns first I think !

[FridgeFreezer]

No you just need the wideband sensor & controller although many controllers also have other optional inputs for data-logging other sensors, however it's usually easier to log the AFR as a parameter from the engine ECU than the other way round.

[Bull Bar Cowboy]

Fridge....

Does MS have voltage compensations for the injectors, or does anyone have a voltage compensation table or details on the injectors used int he RV8? I've got the green striped variant.

Now starting much easier when cold, needs nursing for a few seconds but then looks after itself quite well. So would like to check that I'm getting enough fuel in there while cranking and low voltages etc.

Does MS have a set of cranking settings ?

Also... (I know this is starting to ramble...) The fuel (VE) maps in MS.. Are these actual time the injectors are firing fuel in milliseconds or do they relate to another injector setting in any way ?

All this comparing systems is a big learning curve but keeping the old grey matter strirring....

Neil

MS does not have any means to voltage compensate the injectors .................. in 99% of applications that is not normally a requirement as the voltage will generally be considered to be 13.8volts..............

Yes MS has cranking settings ........... it works like this............the start / warmup is a 3 stage process

As soon as the ignition is turned on, it fires a priming pulse........... there are a couple of options............

1. Fire one pulse at power up (Ign) and another pulse 1 second later .

2. Fire just one pulse at power up (Ign)

The pulse width is entered in mS .............. I have mine set to fire twice @ 4mS

Earlier versions (very early) of MS used to use a priming table that was based upon coolant temp................ this is unnecessary.

Next come the cranking pulses............ cranking is considered to be below 300rpm..........

MS uses a 10 site table to set the cranking pulse widths against coolant temperature in the range from -40C to 71C. These values are entered as mS pulse widths................. I have 10mS @ 4C dropping to 3mS @ 71C

Once the engine is started, it then needs settle time.............. this is referred to in MS as the ASE (After Start Enrichment) settings..........

This is an enrichment for a fixed period to 'settle' the initial start ............. mine is 12 seconds. The values are again coolant table based. The table is 10 sites from -40C to 71C ..........the table values are a percentage that is added to the fuel values in the VE table. There are option to fix this for a duration and then decay out to the timer period................... or just do a straight decay on the timer period. I have mine set to hold the valuers for 8 seconds if the coolant is below 25C and then decay for the remaining 4 seconds..........

After the engine has settled during ASE .................... MS then goes into the warmup phase...........

Warmup again is a table of 10 sites from coolant values of -40C to 71C ............... the value against each coolant temperature site is a % based on the VE (Fuel) table........................ the % is the increase in fuel required...............if you do some calcs the increase in fuel during warm up at cooler temperatures is very significant.

Warmup interpolates the % from -40C to 71C and then returns to direct readings from the VE (Fuel Table)........

Fuel Maps in MS represent the volumetric efficiency and air/fuel ratio at each rpm and kpa site in a 12 x 12 table.........MegaSquirt specifies VE relative to the MAP and includes the AFR in the VE table.

It is based on the following equation: VE = (actual air mass)/(theoretical air mass)*AFRstoich/AFRactual. There fore entering a larger VE in the table makes that site/bin richer, and a smaller number makes that site/bin leaner.

The actual calculation that turn the %VE (volumetric efficiency) into a mS pulse is..........PW = REQ_FUEL * VE * MAP * E + accel + Injector_open_time

Where 'E' is defined as ..................E = gamma_Enrich = (Warmup/100) * (O2_Closed Loop/100) * (AirCorr/100) * (BaroCorr/100)

and 'Warmup' is the warm-up enrichment value from the above mentioned table. 'O2_Closed Loop' is the EGO adjustment based on the oxygen sensor feedback. 'AirCorr' is the adjustment for air density (based on the intake air temperature), and 'BaroCorr' is the barometric correction based on the ambient air pressure .

For those with MS the above goes a long way to explain why heatsoak on the IAT (intake Air Temp) sensor gives rise to a slightly leaner mixtures under heatsoak conditions .............

HTH

Ian

[Bull Bar Cowboy]

Does MS have voltage compensations for the injectors, or does anyone have a voltage compensation table or details on the injectors used int he RV8? I've got the green striped variant.

The older flapper injectors are Bosch 0-208-150-105 .........those are low impedance.......

The High impedance Green banded injectors are 0-208-150-556........ all the info is here http://users.erols.com/srweiss/tableifc.htm#BOSCH

Ian

[FridgeFreezer]

MS does have voltage compensation:

Note "battery voltage correction" below:

Although I don't know anyone who's ever had to alter it from the default.

[Bull Bar Cowboy]

I stand corrected Jon ............ I have never noticed that in there before, and certainly i have never needed to alter it

I have just been out and played around with the setting ............... it makes next to FA difference is you play around with real world values.......

Ian

[istruggle2gate11]

Although I don't know anyone who's ever had to alter it from the default.

I will be soon, it will allow to build my own loom and lose the injector pack - infact I will be asking the opinions of BBC and FF before i do it.

[FridgeFreezer]

You mean lose the resistor pack? That's PWM not battery voltage correction. I'd just find a 3.9 fuel rail & injectors and use that as they don't need a resistor pack.

[istruggle2gate11]

You mean lose the resistor pack? That's PWM not battery voltage correction. I'd just find a 3.9 fuel rail & injectors and use that as they don't need a resistor pack.

Nah, just £120 on injector cleaning!

Yes Resistor pack - typo.

Battery voltage does come into it for my 2.4 ohms low impedance injectors:

Setting the PWM Criteria

To tune the PWM [pulse width modulation] values for your engine, you need to know what kind of injectors you have: low impedance or high impedance.

If you are running high-impedance injectors (greater than 10 Ohms), then set the:

PWM Time Threshold to 25.4 msec, and the

PWM Current Limit (%) to 100%.

In essence you are disabling the PWM mode. This allows full voltage to the injectors throughout the pulse widths.

For low-impedance injectors (less than 3 Ohms), you need to limit the current to avoid over heating the injectors. To do this, there is a period of time that you apply full battery voltage [peak] current, then switch over to a lower current-averaged [hold] current, i.e. peak and hold. Alternatively, you can add resistors in series with the injectors. See the Injectors and Fuel Supply section of this manual for more details.

To run low-impedance injectors with the PWM current limit mode, you need to set two parameters - the "PWM Current Limit (%)" and the "PWM Time Threshold (ms)" - both are on the “Constants” page. The current limit % is the percent duty cycle when the current limit is invoked. The time threshold is the amount of time from when the injector is first opened until the current limit is activated.

1. Start with:

PWM Time Threshold = 1.0 millisecond, and

PWM Current Limit (%) = 75% (30% if you have the flyback board installed). NOTE: the V3.0 pcb should already have the relavent flyback components fitted, the flyback board is only for the V2.2 or V1.0 boards.

2. Once you get your engine idling, then first adjust the PWM duty cycle down in 1% increments until you notice a change in idle quality (be sure to hit the "send to ECU" button each time you change the value). This is the point where the current limit is too much and the injectors are not being held fully open.

3. Then move the value back up 3 - 5% (for example, if the idle falters at 45%, then put in a number of 48% to 50%).

4. Move on to adjusting the time threshold. Lower the time threshold by 0.1 milliseconds at a time until the idle quality deteriorates.

5. Then increase it 0.3 ms.

6. Now, repeat these steps (starting at #2). Adjust the duty cycle and time threshold alternately to get the optimum values for your set-up. You will converge on a set of numbers that work well for your set-up.

The injector opening time and PWM time threshold should be set to the same value. So adjust the PWM time threshold, and the opening time together. However, once you start to tune the 'fine tune' the idle, if you have to revisit the PWM parameters, change the PWM time threshold, not the opening time.

The reason for this is that changing the opening time also changes the AFR, especially at low rpms, so it forces you to also retune the VE table. So unless they get to be different by more than about 0.5 milliseconds, leave the opening time alone after tuning the idle and cruise VEs (unless your are willing to retune those areas).

On the car, setting the PWM parameters is very easy to do and only takes a few minutes. At idle the overall injector pulse widths are small compared to their close time, so this will allow you to adjust the values. In other words, adjust the PWM current limit before taking the car out on the street where injector pulse widths become high, increasing the possibility of overheating your injectors.

You may find that you can idle at a very low PWM%, but the engine will stumble or cough if given any throttle. This can be due to a too low PWM% especially if your injectors are large and the idle pulse width is approximately equal to the PWM Time Threshold. In that case you may be idling almost entirely on the PWM Time Threshold. So rev the engine occasionally as you are tuning the PWM parameters, to ensure that you haven't gone too low.

Also, for some setups, an initial PWM Current Limit of 75% may be too low, so they will need to increase this value - same for the time threshold. Use PWM time threshold values greater than about 1.5 to 1.7 milliseconds only with great caution – it is possible to burn out your injectors!

Note that if you are running the flyback board and need PWM% of 70% or more to run properly, your flyback board isn't working properly! Troubleshoot it carefully to find out why.

The relevance of the above PWM setting to voltage correction? Ive read on a number of occasions, some who have had trouble getting the low impedance injectors to run correctly have found success when adjusting voltage correction with the PWM settings.

This is where i want FF input:

PWM Current Limit (%) = 75% (30% if you have the flyback board installed). NOTE: the V3.0 pcb should already have the relavent flyback components fitted, the flyback board is only for the V2.2 or V1.0 boards.

Does my V3 have the flyback components fitted matey?

[Bull Bar Cowboy]

Yes your V3 is flyback ready .............. but ..........PWM works well on some and not others ..........its implementation is OK, but from what I read and hear its a little finicky with those Bosch injectors. PWM mode has nothing to with Voltage compensation ........... that is tied up with the injector parameters.

Just bin the flapper Low Z injectors and get a set of 3.9/4.6 High Z injectors .............. then you just feed these with 12V and forget all about PWM mode. You will need to replace the fuel rail as well. Matched delivery volume is important, but spray pattern is not .................. think about how the engine works in relation to when the injectors dump.

Ian

[istruggle2gate11]

Yes your V3 is flyback ready .............. but ..........PWM works well on some and not others ..........its implementation is OK, but from what I read and hear its a little finicky with those Bosch injectors. PWM mode has nothing to with Voltage compensation ........... that is tied up with the injector parameters.

Just bin the flapper Low Z injectors and get a set of 3.9/4.6 High Z injectors .............. then you just feed these with 12V and forget all about PWM mode. You will need to replace the fuel rail as well. Matched delivery volume is important, but spray pattern is not .................. think about how the engine works in relation to when the injectors dump.

Ian

Sorry for the Hijack V8freak.......

In that case I shall stick with the resistor pack inline, it works fine and I have a few spares (well lots of flapper stuff), the injectors were cleaned last week, all now flow circa 191cc/min with the largest variation being 1.5%

I wont see any gain (save losing a resistor pack) for a reasonable amount of disruption IMHO.

[Hybrid_From_Hell]

Sorry for the Hijack V8freak.......

In that case I shall stick with the resistor pack inline, it works fine and I have a few spares (well lots of flapper stuff), the injectors were cleaned last week, all now flow circa 191cc/min with the largest variation being 1.5%

I wont see any gain (save losing a resistor pack) for a reasonable amount of disruption IMHO.

If you want more flow / bigger injector rates - straight fits are Jag 4.2 Bosch units from circa 1986 XJ Straight 6s

Have a part no somewhere if yer need it

Nige