Exhaust Manifold.

[Jonny81191]

I've got hold of a spare one so I can start getting my turbo fitted, and it looks very restrictive to me. I'm just wondering if I should put any effort into it, or is it less restrictive than I think?

[Poodle]

Be rude to not gasket match it while youre there.

[Jonny81191]

I was thinking more along the lines of getting a quote/having a go myself for a custom built jobby. Or is that just overkill?

[Mr Whippy]

The ports in the head are small too though, so having fatter manifold tubes to then constrict before the collector won't do much for you.

I think it's important to keep the flow smooth so constant cross-section sounds good, and as Poodle said, just taking time on details is probably gonna get you more benefit, so gasket matching would be a good step.

Also consider the thermal mass in the manifold. Make it lighter and heat soaked off into the manifold will end up in the turbine/turbine housing instead... which might not be ideal.



PS, I was trying to check on parts box earlier, but are all HDi90/110 manifolds the same. Ie, any old k03/GT15 will swap (physically speaking) with any other hdi90/110?

I was certain they were from checking years back but I really can't remember now. I was pretty sure they were the same but can't remember now if the manifold was different too at the turbo end...

Dave

[Jonny81191]

How much meat is in the head? I'm looking at having some work done to one.

[Ruan]

Put it this way, IMHO, versus a XUD9, the ports are fecking TINY...

Mainly exhaust ports... But there's no point in working on exhaust ports if you're going to keep the stock elbow etc... It needs to be 2.5+" all the way back - stock exhaust parts have no place on over double stock power cars...

Sorting the flow past the turbo is the biggest priority, then concentrate on the head... Hate to say it, look to what the TDi guys do, they're getting places with headwork...

[Jonny81191]

TBH i'd like to do the whole thing properly, get the flow right for the turbo all the way through from the cylinders, and get the inlet side of things as efficient as I can.

The downside is the budget though, but i'm getting better at welding so that saves me a fair bit

[Mr Whippy]

You really need to CHECK that things are limiting you first, rather than assuming they are.

Exhaust ports might be small but that doesn't mean they are costing you any significant power till much further up the flow range.

This is exactly where doing just a few things well for your budget, that you know will give gains, is loads better than doing pointless things at high cost that might even cost you power.

All I'll say is do a lot of reading and getting advice, and then testing where limits are to assure any changes you make will be value for money and not just money down the drain!

Dave

[darrenjlobb]

Altho i do agree with that you say ^^ Sometimes you just have to be a man imo, and spend some money, take a risk....yeh it might not work out, but who cares, you tried, calculators and textbooks can only do so much...ive wasted loads of money on things before that have turned out not to work how i wanted / no good...and 60% of them could probs have been avoided with weeks of research / calculations...but time is also money, and sometimes things have just gotta be done....

Id be fairly confident in saying that serious headwork / manifold work WOULD show BIG gains,m but not until you were pushing the motor with a larger turbo....as anything under 200hp is still fairly easy going on the motor / head in stock form id say.

[Dum-Dum]

I have some amazing pics of how much can be ported from a HDi both head and manifolds. Ill put the pics up tomorrow (or go and find them yourself, theyer in the project of my first black HDi that is on here in compressed form)

[Mr Whippy]

I'm not saying don't do it, but there is NO harm at all in doing it later when you realise you have to, then doing it first and guessing you need to do it.



Going slowly and methodically is a great way to tune cars. Make a change, assess the change, if it's good move on, if not work out why it wasn't good, revert. Move forward with the next idea/change.
I'm sure that is exactly how you got where you got with your XUD Darren
Now you know what works and what doesn't you can advise, and over time you improve the knowledge too.


Best to spend more time/money going slower and make sure you have all the best mods and none of the crap ones, and have more power, than do a combo of good and crap mods and end up with something that was cheaper but is crapper because of it!


Right now no one that I know of has done head work AND has any results to show it was worth doing at all... Ie, car is at 220bhp, they can't seem to tune beyond it, turbine intake pressure isn't going up despite more fuelling, maybe it's bad flowing ports? Open up ports and suddenly they see 235bhp. Great. Tune more, 250bhp. Wow, glad I ported the head!

Until you see that kinda thing happening, or work through methodically like that, then you may as well just burn a wad of £20 notes.



I fully support jumping in and doing it yourself. I was fed up of crap remaps for HDi's hence doing my own... but I didn't just crank all the values up to 11 and hope and pray, I iteratively learnt and improved to get the perfect balance I could!

My 2p, invest in a manifold temp probe and pressure gauge. Start looking at the pressure at the head end of the manifold if you can, and also the temp at the turbo end.

Do some porting work on the manifold, see if the reduced thermal mass means more heat is seen at the turbine (meaning less thermal mass in the manifold simply means a hotter running turbo)... see if the pressure drops across the manifold (basically if it goes down at the engine end of the manifold)... if it doesn't then the porting has done nothing for you on your current turbo.

No one has done this testing, no one knows if it's just wasted time/money or not.

Dave

[darrenjlobb]

Right now no one that I know of has done head work AND has any results to show it was worth doing at all... Ie, car is at 220bhp, they can't seem to tune beyond it, turbine intake pressure isn't going up despite more fuelling, maybe it's bad flowing ports? Open up ports and suddenly they see 235bhp. Great. Tune more, 250bhp. Wow, glad I ported the head!

Until you see that kinda thing happening, or work through methodically like that, then you may as well just burn a wad of £20 notes.

But until someone has tried it, how are you going to know.....someones gotta man up first.... I know you can go so far with calculations...but meh...maths / calculations say that 90% of the things I do are wrong...but if i crank things back to where there "meant to be" it looses power...its just swings and roundabouts

[Jonny81191]

TBH I see a middle ground right between what you are saying guys

I want to get this right, but at the same time I don't have the time/money to invest heavily in it. I can pretty much guarantee that improved flow will not be a hindrance to performance, and as such, see no reason to not try it.

I'll go and have a good think and and maybe find a HDi head to play with.

In the meantime, I'll just get a clutch fitted so I can enjoy what I currently have

[darrenjlobb]

You need to be cery carefull with the ports on a di motors head, espically with an 8v, as the ports, well mainly valve area, is designed to swirl the air in such way for the combusion, if you mess it up, you will end up doing ALOT more harm than good...thats in the head itself, so not the manifold...

[Mr Whippy]

Right now no one that I know of has done head work AND has any results to show it was worth doing at all... Ie, car is at 220bhp, they can't seem to tune beyond it, turbine intake pressure isn't going up despite more fuelling, maybe it's bad flowing ports? Open up ports and suddenly they see 235bhp. Great. Tune more, 250bhp. Wow, glad I ported the head!

Until you see that kinda thing happening, or work through methodically like that, then you may as well just burn a wad of £20 notes.

But until someone has tried it, how are you going to know.....someones gotta man up first.... I know you can go so far with calculations...but meh...maths / calculations say that 90% of the things I do are wrong...but if i crank things back to where there "meant to be" it looses power...its just swings and roundabouts

Indeed, I'm all for supporting people trying it... 100%

But don't just do it alongside some other mods while your at it. Do it scientifically. Do a before/after check on pressure/temps and leave everything else the same.

Find out the actual difference it makes and then you can quantify the benefits of the mod for your needs.

But to be honest there is a list of other stuff that is important to get done first for even getting to 200bhp, so I'd be wanting to get a solid performing 200bhp car first before looking at doing anything with the manifold.

If you just do a mod that no one else does but can't attribute any specific benefits to it then how do you know it was a mod worth doing? Magic? Guessing?



Porting MIGHT be a hindrance to performance, that is the problem. Exhaust gas velocity down the ports will decrease and that might impact all manner of turbo performance variables for your needs... ie, under 200bhp of exhaust flow the turbo might be less responsive, and generally you might find yourself optimising for over 3000rpm+ power.
Considering diesels have a limited power band any way, over-sizing ports might be a *bad* thing depending on the other things you want to do.

I'm not 100% on that, but until you are I wouldn't waste time modding something when you have a PROVEN list of mods you should make right now that you can be getting on with and perfecting before messing with unknowns


By all means DO do the mod, but check what changes before/after... only then will you know if it's a mod worth keeping on the car!

Even if the only test you do is a dyno run... it's at least something.

The amount of people I have seen make mods (good on them for trying) but failing to test before/after is the number one reason why a lot of cars fail to make the power the owners expect on a dyno!


You don't have to be clever or do maths/sums/calculations, I rarely do it beyond fag packet maths as there are so many variables at play.
All I'm saying is do some testing to isolate that mod as the single variable and then see what it's like before/after

Dave

[Ruan]

All I can say is, take ALL advice on the interbobs with a very large helping of salt... The amount of times I've assumed "It won't be that because x on y website says it's good for z" and then to realise infact it's all a pile of shit and they were merely speculating from very limited knowledge and understanding...

IMHO don't get too hung up on worrying whether you're going to affect the drive-ability and keeping things within stock limits... Just because a Diesel is rapidly dropping it's efficiency past 3500rpm, doesn't mean to say it's not good to rev it up to there with injection quantities still high... Every engine has an efficiency band, pushing outside of that for PERFORMANCE I don't think is a bad thing...



That above is how graphs SHOULD be looking... None of this power peaking at 3500rpm - that's what gives Diesels their crap reputation for "dying off" and "you're better off changing up a gear"....

Dave just out of interest - are you happy to map in bigger nozzles if you have calibration/flow data for the nozzles? Because as I see things - HDis seem to be in a constant battle between RP vs Durations... Because the nozzles really are so small as stock, the RP is through the ROOF trying to get the durations down, which equals more heat into the Diesel, running the HP pump VERY hard to achieve the pressure required... Bigger nozzles would equal shorter durations, less pressure required to achieve the short duration, therefore less power consumed to pressurize the fuel, therefore less heat in the fuel? VP pumped TDis have been running 220bar injection for years and are happily making 250+hp on simply upgraded nozzles whilst still returning 50+MPG...

But yeah - monitoring is one the most important tools in engine tuning - get a laptop running ELM327 and log your railpressure, get airflow logged... Also Johnny as said on the phone - upgraded air mass meter, then you can monitor your air intake, exhaust gas temp, exhaust pressure... Then you have a GOOD idea of what's going on

[Ruan]

This is how 2.0 16v CR engines should be looking...

[Birk]

Would adding a tubular exhaust manifold to an xud have any benefits, with a td04 and a full 2.5" downpipe.

[Ruan]

You might see small gains if it genuinely flows better than the stock one - post turbine is where you'll see good improvements - the stock elbow is crap for starters, but there's far greater problems to overcome than the exhaust manifold after you've sorted post turbine...

If you can fit the manifold down the back of the engine and keep the turbo as close to the head as possible, you'll probably do some good, but sadly, putting it over the gearbox is never the BEST thing you can do due to the length, the gas has cooled by the time it gets there, more volume to fill etc...

[Jonny81191]

I think I'll just gasket match the head and mani for now, and concentrate on a good exhaust system, do away with the standard downpipe altogether.

Then see what she runs like

[Birk]

I was thinking of trying to make on so it sits in the same place-ish.
But if it's not going to give me a great gain, then there's no point.

Only reason I ask, i fancy a 1.9 dturbo with a big turbo and 170bhp+ I'm just not familiar with messing around with them.

[Ruan]

Piss around with the inlet manifold, get it out the way - the stock inlet on them is a shit design, then put the turbo in the same place as before, but tighter into the engine, with short, equal lengths and you'd be laughing... Keep the heat out the engine bay with good wrapping, and it'll be good...

None needs to be done for 170hp, but it's definitely a nice thing to do... You can then guarantee you're getting the gasses out the head fast enough - although I've personally seen 175hp dyno'd on a stock manifold, and it's definitely made more than 175hp in the past also...

[Birk]

How could that be improved though? I was going to get a xantia inlet, for ease of pipe fitting.

[Ruan]

Xantia Lunchbox manifold, because it's designed seemingly upon a tupperware lunchbox and flows about as well as one, with a ham sandwich in the middle of it... The EGR shit is everywhere inside... They're just a bit pants...

Take a look at Performance diesels - they're all using proper plenum style inlets...

[Birk]

As much as i woukd like to, it means building an alloy inlet, which would blow the budget.

I could td04 it for less than £100 and make a manifold for about the same, it's just the inlet that's the problem.

I can assume you don't like the xantia/405 inlet ? Lol

[Mr Whippy]

All I can say is, take ALL advice on the interbobs with a very large helping of salt... The amount of times I've assumed "It won't be that because x on y website says it's good for z" and then to realise infact it's all a pile of shit and they were merely speculating from very limited knowledge and understanding...

IMHO don't get too hung up on worrying whether you're going to affect the drive-ability and keeping things within stock limits... Just because a Diesel is rapidly dropping it's efficiency past 3500rpm, doesn't mean to say it's not good to rev it up to there with injection quantities still high... Every engine has an efficiency band, pushing outside of that for PERFORMANCE I don't think is a bad thing...



That above is how graphs SHOULD be looking... None of this power peaking at 3500rpm - that's what gives Diesels their crap reputation for "dying off" and "you're better off changing up a gear"....

Dave just out of interest - are you happy to map in bigger nozzles if you have calibration/flow data for the nozzles? Because as I see things - HDis seem to be in a constant battle between RP vs Durations... Because the nozzles really are so small as stock, the RP is through the ROOF trying to get the durations down, which equals more heat into the Diesel, running the HP pump VERY hard to achieve the pressure required... Bigger nozzles would equal shorter durations, less pressure required to achieve the short duration, therefore less power consumed to pressurize the fuel, therefore less heat in the fuel? VP pumped TDis have been running 220bar injection for years and are happily making 250+hp on simply upgraded nozzles whilst still returning 50+MPG...

But yeah - monitoring is one the most important tools in engine tuning - get a laptop running ELM327 and log your railpressure, get airflow logged... Also Johnny as said on the phone - upgraded air mass meter, then you can monitor your air intake, exhaust gas temp, exhaust pressure... Then you have a GOOD idea of what's going on

Again, don't want to repeat myself, but I agree with your angle.

Mod and learn, ignore the 'rules' on the internet because many are written/perpetuated by people who are basically wrong

BUT, when you do do something, make sure you can attribute any success or failure to that specific thing... and then do the community a favour by sharing that knowledge so they can avoid stupid crappy mods.

Ie, the whole cam thing for HDi's... that cam was never a good idea, even before I knew it's supposed origins I told people to check it's impact independently of any other mod, but no one did. They just threw it in with everything else and the net result of their work was impossible to guess at. Useless for them and everyone else. In most cases it was just £200 spent for no benefit at their intended power output. £200 that would have been there to recon the injectors when they failed and made the project have to be aborted perhaps... I dunno.

You only need to see that Pete has had 205bhp from a VNT HDi on a simple manifold and cam to know that you can do well without touching either cam/manifold to at least 200bhp.




Totally agree on the diesel tuning too. Just go look at a tractor pulling competition. They use thermal inertia in the turbo to run them hot as hell for the small window they run in. They run waaayyy beyond stoich. Stupidly inefficient BUT they still make more power, so in the fuel goes!
Revs, well, to a certain point yes, rev to 5000rpm. If your turbo delivery means you have a power band that means revving to 5000rpm makes sense, then do it. That is a diesel engine fully optimised for peak power if that is your goal (I'd take the 1.8T petrol tuned in that car personally but hey)

Obviously everything depends on the customers needs and you need to use your knowledge to provide them with the best compromise to fit that.



Power peaking at 3500rpm is simply a function of torque though isn't it. If it made the same power at 4500rpm, or 5000rpm, it'd be no faster at all. It'd just cost you more money and be less efficient.
I agree it's not ideal, you make your gearing shorter in real terms which is the biggest cost.

Really the turbo is the limit, it's small and flows well to a point. If you could make enough flow to make 150bhp at 4000rpm you would, but you can't. So you make a curve with as much area under it so a customer can go as fast as possible.

Curve shaping is important but many customers like the punch of near 300lbft, so even though it makes the delivery odd, it's what they want. Personally I prefer the cars with less torque to artificially shape the curve more flat and peaky revvy feeling.




The HP vs RP thing is kinda an issue. People chase RP to compensate for long durations because of small nozzles, but that is only half the issue.

The way I see it.

I've seen 300lbft of fuelling on a standard pump/injectors at 2000rpm. Ample for most users needs.
I've seen about 175bhp at 4000rpm (on non-ideal mapping) with standard pump/injectors.

Having bigger nozzles won't remove the flow issue though. In the end to get power you need fuel. Throw it in a 1000000bar or 1bar, the issue is getting in the desired amount in a useful time.

So really the issue is pump flow and as above, it's flow probably runs out of juice around 180bhp at 4000rpm, or 300lbft at 2000rpm.

At a certain point adding more RP to get IQ up is just the same to the pump as opening the injector for the same time with bigger tips. The rail pressure drops, and if it drops too far then the pump can't flow enough and the injector isn't injecting the desired IQ in the opening time given.

Not sure if I've explained it really well but basically when the pump is at it's limit the injectors are irrelevant.

But then we need to consider what you mentioned. Efficiency. If we make efficiency better we can make more power per unit fuel. So we can boost power other ways for the same injection. Ie, less back pressure, manifold porting etc. If they make sense to do that is
Of course you know all this already. But it makes sense to re-iterate that there is no point moving up until we sensibly address issues at each step. Going right for a ported manifold or head ports when we have a crappy exhaust or little turbo, or a limited HP pump, are all just pointless.





I've done a few HDi's with bigger nozzles, but, sorry to say it, they all failed to work well.
In almost all cases a combo of too many mods all at once, or dodgy components, made them impossible to tune properly with. Ie, in one case I spent a few weeks of solid tweaks despite Pete telling me I was within the right ball park with my initial calibration map to start with. Issue, some washers on the injectors were the wrong ones when they were rebuilt by the owner.
In another case, the HP pump wasn't any good, it was uprated but buggered. The customer just sold up and moved back to stage 2/standard injectors as a recon upgraded pump was beyond their budget.

The few projects that succeed are highlighted by the fact they take a long time to achieve and cost a lot of money to get everything working 100%

Usually the customer/tuner work up in steps and get each thing perfect before moving on to the next.

I don't charge customers per visit or per map, I charge for the project usually, or stage it to make sense for the mods they want to do. I try encourage people to work sensibly and logically through their projects to make it easier for them and me!

But clearly it still goes wrong due to big ambitions and a lack of funds and patience.

You can immediately see why the only place that ever packaged mods for these cars (Derv Doctor) didn't go buying used bits off eBay, just like every other big tuner out there they buy new/recon bits and put them on knowing it'll work right away and if it doesn't they just take bits back for a new one.

Obviously it's hugely expensive, so doing it DIY can save a lot of money, BUT, you have to take all those risks of bits not working as intended and sometimes it can cost a lot of money to get some of these exotic parts working right...!





If I were to build a HDi tomorrow to make 200bhp, I'd buy a HDi.

First step full service, cambelt, fuel filters, clean lines, RP relief valve, get everything running as perfect as I can standard.
Stage 1, full fancy exhaust. Run it for 3 months, let the car settle in and see how it goes. Fix ANY issue if it shows up.
Stage 2, standard clutch. Run for 3 months, fix any problems that arise.
Clutch, then push torque as far as it'll go, run for 3 months, fix any issues that arise.
Upgraded pump, fit and run for a month to make sure everything is fine.
Injector tips. Fit and spend as long as is needed recalibrating the maps to suit them.

Hybrid turbo, something that on a remapped road car runs about 200bhp with a good exhaust etc... maybe a GT17 type front end on a back end optimised for about 4500rpm peak engine speed.

Fit and push fuellings iteratively in 10bhp increments every week or so until I hit around 200bhp at 4250rpm or so. Check/fix anything that is a problem along the way.

I bet I'd be about 6 months in the making, and I'd probably have spent about £2000 by the end too... if not £2500.

Eeek. But I know I'd reach that target, and reach it well, and it'd work reliably without smoke, start perfectly in winter, my mum could jump in and drive it etc etc...



Big power HDi's are possible. There is no reason they are not. But not much knowledge exists beyond 200bhp.

The way to get 200bhp+ is to get everything that is known to work well done first, do it all well and make sure it all runs perfectly. Then work up in steps and tick off every mod along the way as a mod having been worth doing.

Manifold porting, before/after dyno, maybe some pressure checks. Tick. It works, if not fix it/revert.

De-MAF, or double MAF (parallel) for more flow, check it all works ok, tick. It works, if not, fix it/revert.

And so on. No need for doing maths/sums, just good old before/after and sensible logging to see if you are wasting time/money or doing something useful


Just throwing a massive combo of unknown quantity parts/mods at an engine and expecting amazing results is just not gonna work




There is no real answer in there I don't think, just my perspective on things.

I'm all for modding basically, and all for 'test and see' vs theory and maths. Just check before/after otherwise you may just be pissing into the wind!


Dave

[darrenjlobb]

Ive rush readed that...but did notice a post regarding not upgrading nozzles..

Tbh, i honestly cant believe that not upgrading them is a good idea....the nozzles and turbo is nie on the most important two things of any DI derv motor, the stock ones a f*cking TINY.... who cares about 10 million bar injection, we dont need that much pressure, i can make mine clean on boost at 200hp with just 200bar injection and nozzles the size of hose pipes...

Yes you can make 200 hp on a stock hdi, but i bet to god it would make it easier with bigger nozzles / better turbo...id have thought the rail pressure / hp pumps would be raping making 200+ on stock parts...it just makes no sence to me....why try to tune a derv with such limited components just because it "can" work...to be it should be chronic nozzles, big vnt / compound setup, basic exhaust / inlet work and a chronic remap....sadly its always the latter which seems to be the issue..

Once aftermarket diesel management systems start getting more and more affordable, i think we will see a huge change in HDI tuning, as finally the TUNERS will be able to TUNE there diesel.....

[Mr Whippy]

Ive rush readed that...but did notice a post regarding not upgrading nozzles..

Tbh, i honestly cant believe that not upgrading them is a good idea....the nozzles and turbo is nie on the most important two things of any DI derv motor, the stock ones a f*cking TINY.... who cares about 10 million bar injection, we dont need that much pressure, i can make mine clean on boost at 200hp with just 200bar injection and nozzles the size of hose pipes...

Yes you can make 200 hp on a stock hdi, but i bet to god it would make it easier with bigger nozzles / better turbo...id have thought the rail pressure / hp pumps would be raping making 200+ on stock parts...it just makes no sence to me....why try to tune a derv with such limited components just because it "can" work...to be it should be chronic nozzles, big vnt / compound setup, basic exhaust / inlet work and a chronic remap....sadly its always the latter which seems to be the issue..

Once aftermarket diesel management systems start getting more and more affordable, i think we will see a huge change in HDI tuning, as finally the TUNERS will be able to TUNE there diesel.....

The nozzles are good to 200bhp on an appropriate pump.

Yes RP is high, but that is irrelevant.

RP is a function of how much flow you want to get into the engine and how big the nozzle is.

You could run huge nozzles and low RP, or high RP and small nozzles.

But you can't get BOTH without a BIG pump... and that is the problem, the pump.


The standard HDi pump is good to maybe 180bhp assuming all else is good, at about 4000rpm.

Big injectors, small ones, twice as many, it won't make any difference. No combo of rail pressure and tip size will get around the fact the pump just can't flow enough fuel for more power, no matter how it's injected.


So injectors, yes upgrade them, but only when you have a better pump too.


The old XUD pump is different. They can flow LOADS of fuel. The issue is they probably have higher parasitic losses due to being over-specced a lot of the time.
To a certain extent bigger nozzles are less precise, so over-sizing won't give exact injections at low IQ's, so idle and cold-starting and precise emissions control are less feasible.

Not saying that is bad, if power is what you want great, I personally live the XUD9 when tuned up!

But the HDi is different in a lot of ways, and beyond the small turbine on the stock turbos causing torque curves like mountains and peak power at ~ 3500rpm or below, the next problem is the HP pump!

Dave

[darrenjlobb]

Yes RP is high, but that is irrelevant.

I dissagree with that...

No pump is going to hold CHRONIC flow AND CHRONIC pressure like that...not without having multiple HP pumps hooked up, and i just dont see the need, if you just ran bigger nozzles and dropped the pressure down, everything would be happy, HP pumps wouyldnt be getting RAPED, fuel wouldnt be being superheated, just less to go wrong, and less upgrades needed for big power....yes 200 hp is possible, but your pushing everything to sky limits on the fuel system, im sure if you just put big nozzles in and dropped the pressure, you could happily run the same 200hp, with way less pressure, and have TONNES of flow overhead for future tuning....

Bear in mind I dont run an XUD, i run a dw10 with a ve on it...hence im comparing the same motor here, 200 bar vs 04309584957834bar CR...dont get me wrong, of course the high pressure will help, it can only make it better...but with the levels your talking, its just insane / pointless IMO from a tuning perspective....

Dont like to mension it...but cough TDI boys cough...pretty much the FIRST thing you do, is change out the nozzles....cummins boys....first thing you do nozzles... I know this isnt always common rail, but its DI, and cr or not, the nozzles are ALWAYS restriction in there stock form as there designed to be as clean as physically possible / most MPG strict at X hp....

[Mr Whippy]

What is chronic pressure?

The end result is a given volume of fuel ends up in the cylinder to burn. Multiply the volumes by the number of injections and in a given time the pump has to move that much fuel. That is all it has to do.

So fire it through a big hole at lower pressure, or a small hole at higher pressure, in the same time, and that is what you need to do. The thing that does that job is the pump. Even at sensible rail pressures of say 1000bar you can request too much IQ at reasonable injector opening times that the pump can't provide it. You need to lower the rail pressure but then opening time might get too long, so the end result is you need to ask for less fuel. That is purely a failure on the pump.
Having a big injector tip that could flow more wouldn't allow a better end result by a large margin in those cases.

Pressurising the fuel too highly is obviously going to have an impact of fuel temp, and thus calibrations may go out of range and become inaccurate, the parasitic losses to pressurise fuel get high, BUT, just as you said earlier:

"IMHO don't get too hung up on worrying whether you're going to affect the drive-ability and keeping things within stock limits... Just because a Diesel is rapidly dropping it's efficiency past 3500rpm, doesn't mean to say it's not good to rev it up to there with injection quantities still high... Every engine has an efficiency band, pushing outside of that for PERFORMANCE I don't think is a bad thing... "

Efficiency is dropping off by going hard on the standard pump/injectors, BUT, you can still get performance going there!




I'd happily upgrade nozzles and remap for them, but as with anything on a HDi, if it's not right, it won't run right, and since professionally made/warrantied injectors are not cheap, it's near impossible to get people willing to spend £400-500 for injectors that will 100% work, when they can go from 90bhp > 150bhp on standard components bar the FMIC they fit, for about £500!

Yes, if you are going to go for 200bhp+ go straight for the nozzles. You'll probably need them. Thing is, not everyone is going for 200bhp. Most people are happy getting to 125bhp for about £150 for a remap! Or £500 for 150bhp FMIC.

Asking them to pay £400-500 for guaranteed upgraded injectors built to the tuners spec (so they can make sure they calibrate well), just so they can do the same thing isn't viable.

Just look at the HDi's bottle necks/restrictions on each component. If you can kinda hit them all nicely at 150bhp, why upgrade something to offer even more potential if you can't really use it till higher output?
Turbo, to really make use of it you need new injectors/hp pump/exhaust.
Pump, to really make use of it you need the turbo and injectors.
Injectors, to really make use you need new HP pump and turbo.



Yes if you go for 200bhp, then get new injector tips, but you'll also need a new pump too. Possible cost for good versions of both, assuming you need them reconditioned to assure they deliver? £800?

It's starting to get big money and many HDi owners, with all due respect to them, don't have budgets that big. Those who do are very thin on the ground.



I've only seen one car that really did 200bhp+ well and that was Pete's car. All the rest usually blow up or fail to get there because of budget issues when they find their new parts didn't work right and would be expensive to recondition. Others are over-rated when you look at the real performance, or have been unreliable... ie, skimping in one area results in failures elsewhere.


IF people were willing to spend money then I'd have specced and would retail (at cost price only) upgraded injectors, but no one wants to spend that. They want to buy them cheap and try fitting new tips to possibly old worn bodies and do it for half the cost and make them impossible to guarantee when doing the arduous recalibration task!
Even back when we did FMIC/remap/de-cat specials owners didn't have that deep pockets. Even those with deep pockets gasp at the cost of injectors done properly and warrantied. If the don't then the re-calibration task can be a complete nightmare (read 6 weeks of going round in circles when the issue all along was the wrong washers used haha!)




Just to clarify, I do agree with what you are saying. I just remap cars for customers in the end and very few see doing injectors as good value for money.

I've not mentioned any RP values on this thread, so I have no idea what chronic RP is.

I generally don't recommend upgrading pressure sensors (unless they just want a cheap 2nd hand one as the 1800bar sensor is cheaper), because I know the standard pump is already on it's arse to about 1350-1450bar at 150bhp injections for a standard turbo. Upping the pressure to get shorter injections to burn more fuel just means a hotter turbine and no more power.
Upping the pressure in the mid-range just means pump can't deliver the pressure and quantity so you get no gain there. BUT, all those 150bhp tunes run fine and cheaply for the customer.

The only viable move at that point is to decide what you want. In theory with a better turbo with less back pressure you can rev harder, make power further up, and since your revving harder your pump spins faster, and you can make your same 'safe' injections at higher engine speeds and make more power that way.

You don't even need to make big injections at high RP if you just do more injections per unit time (higher rpm)

That is how you can get a bit more from the standard system while still using ~ 1450bar injections...



Beyond the ~ 300lbft @ 2000rpm > 180bhp @ 4250rpm kinda bracket, the standard HP pump can't do anything more, high RP or not, it just can't flow enough.

Upgrade it and the injectors is the next step.


In an ideal world where all mods are free, maybe not, but in a world with prudent customers who want cheap upgrades for their 10yr+ old HDi cars just for a bit more power, then that is what happens. Injectors/HP pumps come a long way down the list.



Yes, injectors are a good upgrade for the XUD Bosch pumps, because the injector embodies a lot of what you edit in the 'map' of a HDi anyway. So in upgrading your injectors (which is also cheaper and less fraught with calibration issues) you can fix the fundamental problem areas right away (ie, break pressure, volume, reconditioned an new, nozzles etc)


Now, if I said to every customer, I can remap your car, but you'll need to add £400 for upgraded injectors for stage 1 or stage 2 tunes, they'd all laugh at me.




Sorry if I've repeated myself there again. Just not sure what I'm meant to do. I'm a re-mapper, but the customer chooses their route irrespective of the advice I might offer to the contrary.

I tend to generally agree with your view, but until I have a customer turn up with a car and £2000 and say 'make it as fast as you can for £2000', I can't really do much hehe...

Dave