12-12-2012, 04:22 PM
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
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