darrenjlobb's Adaptronic Managed Compound Blown Derv Bus Build

[bashbarnard]

that's not high tbh, I'm sure Darren revved one of his old engines further, fairly commonplace for engines with more valves to rev higher, though the old M51 BMW inline 6 goes to 4800 and that's just a 12 valve.

its usually more a function of bore vs stroke plus rod lengths.

Airflow through the engine is a tiny portion of the story... Valves do help move more air at high RPM, but you'll tend to always limited by the injection system rather simply by airflow - which can usually be upgraded more than enough by fitting decent turbos.

Usual limit is simply the time you have to start the injection, get the quantity of fuel you need in and finish the injection, ensuring it's all in before the compression is fading away - there's a limit to how much timing you can give it... There's also a fixed amount of time that it takes from the point of fuel going in until the first sign of combustion (ignition delay) which has to be factored in...

At 1400uS duration (yes, 0.0014 seconds...) at 4000rpm - it'll take 33 crank degrees to get the fuel in... Move that to 5000rpm and that's now taking 42 crank degrees... At 5800rpm you're up to 49 crank degrees... That's just to get the fuel in, ignoring the fact that 50 degrees ago the first of the fuel went in and is now starting to combust - the last of the fuel still has some time to go before it even begins to combust! To make that power up high you need insanely short injections and quite a bit of timing, even to ensure that the fuel is in early enough to compensate for the ignition delay and ensure the fuel is combusting at the right time.

Joy of commonrail is that you can have those huge injectors that inject a huge amount of fuel in a very short time at high pressure... However even at lower pressure - you can get an acceptable idle and midrange and ensure you're getting good spray patterns for decent combustion, but crank the pressure and you've got craploads of fuel going in a short period. Just need some bigger nozzles!

repped for this. Really good explanation

[Rippthrough]

Can you get away with a small pre-injection to get some fuel in early before the main injection/combustion event, or are you running too much pressure to get away with it without pre-ignition?

[Pugmarshall]

Can you get away with a small pre-injection to get some fuel in early before the main injection/combustion event, or are you running too much pressure to get away with it without pre-ignition?

Pre injection is more for noise, reduces the jump in injection pressure when the main injection happens. Increasing this will more than likely have next to no gain when you consider effect on propulsion and the potential risks regarding the reduction in mechanical and thermal efficiency.. Pretty sure Darren runs a pilot on this, which won't be at high rpms anyway, which is where he has 'issues'... Not to mention you probably won't have enough timing to fit a pilot in considering the amount of work needed to be done in such a small window.

Bottom line he needs bigger nozzles, as he and Ruan have said.. I'm probably 100% wrong and I'm sure one of them will be along soon to confirm  

I have so much respect for you Darren and Ruan... This is perfect in every way, and the way it's been executed is mind blowing. Watching this with more anticipation than ever lately!

[Piggy]

Here here

[Ruan]

Can you get away with a small pre-injection to get some fuel in early before the main injection/combustion event, or are you running too much pressure to get away with it without pre-ignition?

Yeah, it does help massively at lower engine speeds to keep combustion stable, shorten the ignition delay and keep a smooth pressure rise in the cylinder:



That spike in the red line without pilot is the classic diesel "CLANK" you always hear - it's the rapid pressure rise in the cylinder from the fuel all combusting very quickly - rather than a stable burn.

However at higher RPM (>~3500rpm) you're fighting the ignition delay... There's not the compression/heat at the angle you'd need to get the fuel in early enough to have it help the main combustion - by the time the compression comes, it's already too late and the main injection needs to start going in to allow for the ignition delay. This is why almost all OEM engines will shut the pilot off at high RPM/quantity.

Any small improvements in shortening the ignition delay from the pilot injection pre-heating the combustion chamber will instantly be wiped out by the fact that solenoid injectors aren't quite fast enough at very high RPMs to do two injection cycles without negatively affecting the main injection profile - that is time between the current hitting the coil, the needle lifting and fuel starting to flow. Again at high RPM, the time is so short, you can't do anything about it.

Simply getting the fuel in within a decent window is the key to getting good quality combustion at high RPM, rather than it going out the exhaust as noise and heat.

You can't/won't get "pre-ignition" based upon changes in pressure, because the injection angle (+ duration of the ignition delay) is the angle at which combustion starts... You're waiting for combustion to start, rather than preventing it from starting too early from external influences (pressure, heat, cylinder hot spots etc). If it's starting too early (pressure rise is too fast, loud dieselly rattle) then you need to back off the timing.

Large, well controlled nozzles FTW basically!

[Rippthrough]

Yes, I guess the nozzle/seat delay/hysterisis becomes a large portion of your injection time up top?

What you need is to get the dremel out and fit 2 more injectors per cylinder...

[Dave]

Yes, I guess the nozzle/seat delay/hysterisis becomes a large portion of your injection time up top?

What you need is to get the dremel out and fit 2 more injectors per cylinder...

I am with this man. Please get the dremel out 

[darrenjlobb]

Sadly got a bit of a crappy / annoying update on this project and others I guess, but have sadly recently lost my workshop as it is, which is going to obviously hugely effect the progress of this bus!

As anyone who has been here will know, my "workshop" is really nothing more than an old calve shed which I took over many years ago, but as much of a bodge the shed is, it has grown into a pretty busy and kitted out workshop over the years, with the pit / dyno etcetc. We have recently converted the barns opposite the "workshop" and let them out, which I have obviously known about for a long while, but sadly the time has now finally come where tenants are moving in so I have had to make a fairly sharpish exit. As you can imagine, people living in the country are not going to be massively impressed at high output diesels at 7krpm WOT at 9pm in the evening, or as there sitting down for there sunday roast. So this is really the reason behind having to get out!

Sadly though I don't have anywhere to go in the immediate future that allows space for the dyno / lift etc. So I have downsized rather majorly to a corner of a building up on the farm. Its going to be a case of saving money to put up another building in the future to give me space to get my kit all back where I need it etc. This wont be possible anytime soon, so in the meantime I am at a bit of a major disadvantage compared to my "normal" setup I have built up over the last 10 years! 

If nothing else, I have decided its a good excuse to try and get the rest of the car back together, and fit for an MOT, to try and make FCS 2017 happen, which will be the first time for this car in 4-5 years at least now I think!

Current project is sorting injectors, which is also something I should be able to continue with once I get all my tools moved / power sorted out in the new area.

Cheers for reading.

p.s. if anyone wins the lottery, donations are kindly received!!

[Piggy]

I spotted the conversion across the yard....in hope of epic LobbLand workshop with vip section and hot tub.

I am dissapointed.

[Eeyore]

Bad luck Darren. Hope you get it sorted out sooner than you currently think!

[bashbarnard]

Well silver lining, if youre building your own workshop this time , although costs are more, you can design it around yourself. Also be nice to finally meet if you make it to fcs this year.


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[Matt-Rallye]

To echo what bash has said it s crappy situation but at least when you do finally build your own workshop you can make it exactly how you need it rather than alot of 'lash up' and 'make do'

[zx_volcane]

Just a hiatus hopefully, onwards and upwards Darren.

End of an era for sure though, be a sad day when you have a workshop that allows you to open the bonnet full on all cars :p

[Dum-Dum]

Gutted for you mate. Id be gutted if I had to downsize from my 100sqft and plenty of parking back to a corner of my parents garage and single parking space so I can only imagine how you feel loosing your frankly awesome setup.

Hopefully the new build stretches to a decent space with room for plenty of storage and a proper ramp for you.

[Mattcheese31]

that's a real shame for you mate, bet it feels a bit like losing a limb, nothing stays the same though, guess you'll just have to make a better bespoke area for yourself and take advantage of starting from scratch, all the best fella, be great to see you at FCS anyway x

[darrenjlobb]

Still a bit quiet in here,

Have taken on a new corner of the tractor shed, its far from ideal, but its a space in the dry, but obviously without lift/pit and the dyno, development on the car has pretty much slumped to a standstill!

However! I have taken full advantage, and spent some time putting the rest of the car back together, so have now got the front end back on, lights working front and rear other than a fog light wiring issue, and horn etc connected up. Basically taking some time to make all the other things work in prep for an MOT at some point pre pugfest / FCS!

[Eeyore]

Yaaaassss. Sounds like its going to make it!

[MY95]

Getton Darren, sure everyome will agree it would be ace to see it at Pugfest/FCS this year!

[darrenjlobb]

Does anyone on here work in the shed construction industry, or even dismantling used sheds?

Don't realise how much you rely on what you have until its gone, a right nightmare here at the moment.

Next job is to sort out the farce that is the wheels that arnt round, leak, and are rusting out....Once thats sorted, its not far off from being ready to MOT. Working on the floor with jacks is like going back 10 years in time! Things have suddenly become 10x more effort / time consuming sadly

[darrenjlobb]

12 Months MOT, and the cars first official outing today after 5 years off the road!!

[Danny Wideboy]

Haha, fair play that man.
Bet it feels good.

[Mattcheese31]

wow that long, how's she going mate? . . .

[bashbarnard]

Nice one man. Bet youre well chuffed


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[Piggy]

Like a rebirth, the 306 scene is back to normal

[Matt-Rallye]

Actually really liking the stickers on the rear

Kudos on the MOT fella always feels like an accomplished milestone

[Eeyore]

Stickers look good Can you get me a shot of the back of the car?

[C2K]

Good result Darren, the culmination of an incredible amount of work and self-teaching. Tremendous respect for the end product achieved, even if you feel derailed somewhat by logistical hurdles right at the end.

[Frosty]

Great news Darren, a big step in the right direction!

[darrenjlobb]

Thanks guys, feels great having it on the road, certainly a big moment for me and the car!

Now begins the tuning of another variety, due to limited workshop facilities / time and money at the moment, the engine tuning is somewhat on hold, although I am working on a new flow bench to enable me to calibrate and flow test CR injectors, so I am able to build my own injectors and get accurate calibration data, as I have given up trying to get any other company to do this for me now and no more money is being thrown at people wasting my time....

So now its time to get the car setup a bit, and dial the engine in to the chassis somewhat.

First big project has been getting the low / mid range fuel control more useable. The dyno makes tuning WOT very easy, but there is still alot of work to be done in the midrange, not so much in terms of fuel tuning, as this has already been setup on the dyno, but actually at logic level to make the car drivable.

Because I have re-wrote the ECU logic / software from scratch, it has started in a very basic form, and has become more and more advanced over time (13 ECU pages so far!). But now its on the road, it has instantly became clear I needed more logic to give some form of governor / engine stability control. In basic terms, the way it was setup, was largely as I call "direct rack control" where I am referring to the throttle cable being directly connected to the fuel rack in a P pump, or if you like, directly to the control collar in a VE rotary pump. Altho this is great for WOT etc, the second you try to "drive" the car, it becomes extremely hard, as soon as the engine gets unloaded / at light load, you will find it wants to "hunt" / "judder" like crazy as its coming on / off the fuel demand. A simple spring in the VE governor is all thats required to smooth this out in a mech pump, but its quite amazing how hard it is to replicate this simple spring in software / logic. However after quite alot of work, I am now getting somewhere, and the car is now largely drivable across most of the useable rev range, really just needing some extra dampening / control logic at very specific conditions where there are still issues, but we are making good progress and its already 10 x better than it was a week ago.

Another thing that has also become noticeable is the need for VSS / vehicle speed input into the ECU to allow me to create some tables for speed vs mm3. Predictably, it is impossible to put this much power down in first, and second gear at times even with the LSD an dry weather. I have got some basic control to get it away from a dig now using a button I have mounted on the gearstick connected to an aux input, which then switches some logic I have wrote for some basic launch control, which basically brings in an secondary 2 step at x RPM where I find it launches best with most traction. it also adds a late post injection to build EGT and spool the turbos, which is working very well, and will really get up and move now, but the problem is the second you let go of the button, it just tears the front end loose and wraps around to the 6k hard cut. So plan is going to be get some vehicle speed sensors hooked up on back wheels, so that I can limit torque / mm3 based on speed, then should be able to get the car dialed in to come off the line hard every time... In theory anyway! Have toyed with connecting all four VSS inputs and actually implementing traction control, but think this is likely to be a project for the future!

Bit of a boring update, but there isn't really alot to show for the recent work, but it has made some big leaps forward. And I am learning all the time!!!

Thanks for reading and supporting as always

[MY95]

Very clever stuff Darren, great news it has an MOT, have enjoyed watching all the videos, hope to see you/this at Pugfest/FCS this year, im sure we would all agree this would be epic!