Fuel Pressure...
Discussion
OK - so the next stage of the 'build' is in place ...
Injectors have arrived ... 45mm inlet manifold, trumpet base and trumpets and 72mm plenum have been ordered (they'll be a couple of weeks apparently) ... spare fuel rail has been procured ...
I'm going to keep the current 4.0 inlet hardware and injectors until she's run in - no more than 3,500 rpm for 500 miles so she'll be running closed loop so the ECU will be handling the fueling using the lambdas so no worries of running too lean.
After that - before she's mapped - I'll swap over the new bits as a complete assembly ... changing those notorious flexible fuel lines at the same time as well.
Question is, is it worth upping the fuel pressure to 3.0 bar at the same time too - the Vectra injectors are rated at 3.0 bar anyway - and I was thinking of getting a new fuel pressure regulator anyway (in for a penny and all that b*ll*cks) - it's 'only' another £80 on the parts spend!
What does the assembled wisdom reckon?
Phil
Injectors have arrived ... 45mm inlet manifold, trumpet base and trumpets and 72mm plenum have been ordered (they'll be a couple of weeks apparently) ... spare fuel rail has been procured ...
I'm going to keep the current 4.0 inlet hardware and injectors until she's run in - no more than 3,500 rpm for 500 miles so she'll be running closed loop so the ECU will be handling the fueling using the lambdas so no worries of running too lean.
After that - before she's mapped - I'll swap over the new bits as a complete assembly ... changing those notorious flexible fuel lines at the same time as well.
Question is, is it worth upping the fuel pressure to 3.0 bar at the same time too - the Vectra injectors are rated at 3.0 bar anyway - and I was thinking of getting a new fuel pressure regulator anyway (in for a penny and all that b*ll*cks) - it's 'only' another £80 on the parts spend!
What does the assembled wisdom reckon?
Phil
You will get a number of opinions - here's mine.
When my car was upgraded like yours - 5 litres, shortened crumpets, steath cam, Bosch red top injectors, 20AM, 72mm, etc etc I had major problems with lean running over 4600 rpm. We tried increasing the fuel pressure, but in the end I took it to Mark Adams for a proper rolling road remap, as I use the 14CUX, and the first thing he did was change the fuel regulator back to the standard, (which I think is 2.5 bar?).
When my car was upgraded like yours - 5 litres, shortened crumpets, steath cam, Bosch red top injectors, 20AM, 72mm, etc etc I had major problems with lean running over 4600 rpm. We tried increasing the fuel pressure, but in the end I took it to Mark Adams for a proper rolling road remap, as I use the 14CUX, and the first thing he did was change the fuel regulator back to the standard, (which I think is 2.5 bar?).
If its going to be mapped with an aftermarket ECU I would say it not a bad idea but not essential. I would expect the Vectra that they came off of would have been 3 bar, so running them at 2.5 means the spray pattern might not be as good. If you up it to 3 bar I would expect a bit cleaner idle due to the improved spray pattern/better fuel atomisation which will help with emissions and of course more head room for further mods.
When I took on a few more cc I already had the vectra injectors. I knew they didn't have much left on my old engine so I went for a 3.5 bar reg off a cerbera or speed 6 engine. Straight swap and injectors are no longer stressing out over 80%
Secret is not to go too big otherwise you can struggle at low rpm.
Secret is not to go too big otherwise you can struggle at low rpm.
I`ve been told over sizing injectors can make controlling the fuel less accurate because of a very short pulse width.
Thats why fitting 40lb injectors on a 300bhp is not a good idea .
I have the Bosch gen 111`s which are 30lb which at 346hp are under 80% duty.
Thats why fitting 40lb injectors on a 300bhp is not a good idea .
I have the Bosch gen 111`s which are 30lb which at 346hp are under 80% duty.
Edited by SILICONEKID345HP on Tuesday 21st July 10:59
SILICONEKID345HP said:
I`ve been told over sizing injectors can make controlling the fuel less accurate because of a very short pulse width.
Thats why fitting 40lb injectors on a 300bhp is not a good idea .
I have the Bosch gen 111`s which are 30lb which at 346hp are under 80% duty.
You are absolutely right ... going excessively oversize on injectors can cause issues with fuel trim at idle - and I've already gone for the Vectra injectors (approx 25% increase - 250cc as opposed to 215cc @ 3bar). Thats why fitting 40lb injectors on a 300bhp is not a good idea .
I have the Bosch gen 111`s which are 30lb which at 346hp are under 80% duty.
However the question was actually whether it would be worthwhile upping the fuel pressure at the same time - there are some valid reason why doing so might be useful / appropriate ... as has been suggested above, running an injector at lower than its rated pressure could affect the spray pattern for example.
... or to put it in plumberspeak - could be the equivalent of buying a nice Hansgrohe Rain-Air shower head that works beautifully on - say - 6 litres per minute flow and then running it at 4 litres per minute and wondering why you don't get a nice invogorating shower, yes?
Phil
Bassfiend229hp said:
You are absolutely right ... going excessively oversize on injectors can cause issues with fuel trim at idle - and I've already gone for the Vectra injectors (approx 25% increase - 250cc as opposed to 215cc @ 3bar).
However the question was actually whether it would be worthwhile upping the fuel pressure at the same time - there are some valid reason why doing so might be useful / appropriate ... as has been suggested above, running an injector at lower than its rated pressure could affect the spray pattern for example.
... or to put it in plumberspeak - could be the equivalent of buying a nice Hansgrohe Rain-Air shower head that works beautifully on - say - 6 litres per minute flow and then running it at 4 litres per minute and wondering why you don't get a nice invogorating shower, yes?
Phil
I recently went from 2.5 bar to 3 bar ,other than coping with more hp it did not give me one extra mpg or bhp ..However the question was actually whether it would be worthwhile upping the fuel pressure at the same time - there are some valid reason why doing so might be useful / appropriate ... as has been suggested above, running an injector at lower than its rated pressure could affect the spray pattern for example.
... or to put it in plumberspeak - could be the equivalent of buying a nice Hansgrohe Rain-Air shower head that works beautifully on - say - 6 litres per minute flow and then running it at 4 litres per minute and wondering why you don't get a nice invogorating shower, yes?
Phil
If your injectors are less than 80% fuel duty at max bhp I can`t see you gaining a lot unless the injectors are designed to run on more pressure .
SILICONEKID345HP said:
I recently went from 2.5 bar to 3 bar ,other than coping with more hp it did not give me one extra mpg or bhp ..
Cool as I wasn't asking the question for more MPG or BHP...SILICONEKID345HP said:
If your injectors are less than 80% fuel duty at max bhp I can`t see you gaining a lot unless the injectors are designed to run on more pressure.
Exactly ... my current injectors are 86% at 2.5bar on a 4.0 and I've gone to a 5.0 *AND* the Vectra injectors are spec'd at 3bar ... hence my question. 
Bassfiend229hp said:
Exactly ... my current injectors are 86% at 2.5bar on a 4.0 and I've gone to a 5.0 *AND* the Vectra injectors are spec'd at 3bar ... hence my question.
I don`t know what ECU have ! not a problem with the aftermarket stuff .I went for the BMW Bosch 3 bar regulator recommended by Simon ,got rid of the adjustable one .
Edited by SILICONEKID345HP on Tuesday 21st July 21:09
SILICONEKID345HP said:
I don`t know what ECU have ! not a problem with the aftermarket stuff .
I went for the BMW Bosch 3 bar regulator recommended by Simon ,got rid of the adjustable one .
Do you no the partsnymber of the BMW bosch regulator?I went for the BMW Bosch 3 bar regulator recommended by Simon ,got rid of the adjustable one .
Edited by SILICONEKID345HP on Tuesday 21st July 21:09
There are various part numbers for the same part - one of the Bosch ones is 0280 160 249
If the Vectra injectors are specced to run at 3 bar, then run them at 3 bar. Simples
And just for Daz's benefit, I'm running 440cc Bosch injectors at 'only' 2.5 bar with absolutely no resolution issues at idle at all. Don't believe everything you hoover up on the net
If the Vectra injectors are specced to run at 3 bar, then run them at 3 bar. Simples
And just for Daz's benefit, I'm running 440cc Bosch injectors at 'only' 2.5 bar with absolutely no resolution issues at idle at all. Don't believe everything you hoover up on the net
SILICONEKID345HP said:
Bassfiend229hp said:
Exactly ... my current injectors are 86% at 2.5bar on a 4.0 and I've gone to a 5.0 *AND* the Vectra injectors are spec'd at 3bar ... hence my question.
I don`t know what ECU have ! not a problem with the aftermarket stuff.I'm running a CANEMS and have been doing so for several years...
SILICONEKID345HP said:
I went for the BMW Bosch 3 bar regulator recommended by Simon ,got rid of the adjustable one.
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