Well well, Fuel Pressure
Discussion
Finally got my sticky paws on a fuel pressure meter so I can see what fuel pressure my injectors are getting.
Standard Griff fuel pressure regulator is 2.5bar.
Standard injectors are 189ccm. (At 2.5bar). (14.5ohms resistance).
My fuel rail measured at 3.4bar at idle and 3.5bar on revving.
I was told my original pressure regulator had been modified to a higher pressure but I wasn't told what pressure.
Injector calculator says... 189ccm at 3.5bar equals actual output at 223ccm.
I've now got a 3bar fuel pressure regulator and a set of Bosch injectors that at 3bar will give 220ccm.
Bosch injectors are also 14.5ohms resistance.
I'm going to swap the regulator and injectors very soon.
Mates and Mrs always comments the car smells rich. Just 3ccm less fuel is very much close enough for me.
Straight swap it is.
Standard Griff fuel pressure regulator is 2.5bar.
Standard injectors are 189ccm. (At 2.5bar). (14.5ohms resistance).
My fuel rail measured at 3.4bar at idle and 3.5bar on revving.
I was told my original pressure regulator had been modified to a higher pressure but I wasn't told what pressure.
Injector calculator says... 189ccm at 3.5bar equals actual output at 223ccm.
I've now got a 3bar fuel pressure regulator and a set of Bosch injectors that at 3bar will give 220ccm.
Bosch injectors are also 14.5ohms resistance.
I'm going to swap the regulator and injectors very soon.
Mates and Mrs always comments the car smells rich. Just 3ccm less fuel is very much close enough for me.
Straight swap it is.
Just out of interest don’t you ideally require a re map to re scale the fuel tables to reduce your over fuelling mainly at lower revs or won’t this change just result in the same over rich mixture you talk about.
I’m thinking about the duty cycle and injector opening times but I’m a complete layman and just remembering snippets from things I’ve read in the past.
And do keep us informed as I’ve often thought about slightly bigger injectors but never been brave or enlightened enough to pursue it.
I’m thinking about the duty cycle and injector opening times but I’m a complete layman and just remembering snippets from things I’ve read in the past.
And do keep us informed as I’ve often thought about slightly bigger injectors but never been brave or enlightened enough to pursue it.
I'm told they should be a straight swap.
Having virtually identical flow rates and the same 14.5ohms resistance they will be fine.
It's the ECU that controls the opening time so the same duty cycle on the same flow rate means same amount of fuel.
Injectors are basically an on off switch. Dumb component really.
When I've swapped them I will recheck the pressure and also have the exhaust gasses sniffed to ensure it's all good.
Having virtually identical flow rates and the same 14.5ohms resistance they will be fine.
It's the ECU that controls the opening time so the same duty cycle on the same flow rate means same amount of fuel.
Injectors are basically an on off switch. Dumb component really.
When I've swapped them I will recheck the pressure and also have the exhaust gasses sniffed to ensure it's all good.
Harvy500 said:
I'm told they should be a straight swap.
Having virtually identical flow rates and the same 14.5ohms resistance they will be fine.
It's the ECU that controls the opening time so the same duty cycle on the same flow rate means same amount of fuel.
Injectors are basically an on off switch. Dumb component really.
When I've swapped them I will recheck the pressure and also have the exhaust gasses sniffed to ensure it's all good.
Thanks Having virtually identical flow rates and the same 14.5ohms resistance they will be fine.
It's the ECU that controls the opening time so the same duty cycle on the same flow rate means same amount of fuel.
Injectors are basically an on off switch. Dumb component really.
When I've swapped them I will recheck the pressure and also have the exhaust gasses sniffed to ensure it's all good.
Yeah I get all that.
Hopefully you also get a better spray and atomisation.
Good luck with it and do keep us informed.
The original injectors are a single hole kind of conical spray where as the new Bosch ones are 4 hole with a finer mist pattern.
I can't imagine what the spray looked like coming out of the in place injectors bearing in mind they're designed to work at 2.5bar and suddenly 3.5bar is being shoved through them. Can't see it being ideal.
The new Bosch ones should atomise the fuel better and theory says (not mine) smoother running, better mpg and perhaps a few extra horses.
Just smoother would be nice.
I will update this when it's done and let you know the results/feel etc etc.
I can't imagine what the spray looked like coming out of the in place injectors bearing in mind they're designed to work at 2.5bar and suddenly 3.5bar is being shoved through them. Can't see it being ideal.
The new Bosch ones should atomise the fuel better and theory says (not mine) smoother running, better mpg and perhaps a few extra horses.
Just smoother would be nice.
I will update this when it's done and let you know the results/feel etc etc.
Edited by Harvy500 on Wednesday 23 October 18:27
Stands to reason 4 smaller spray holes should provide a finer mist but the same amount of fuel.
Why would they make them otherwise.
Hopefully they correlate to better performance.
Having read quite a bit about porting it’s always been a problem with fuel running and pooling as it inevitably hits the inlet ports on the way to the combustion chambers.
Some inlets have a dimpled effect to avoid this and why it’s generally accepted rough porting works better than polished porting.
Even air can grab on smooth ports where as rough ports break up the area of grab and create a smaller wall of resistance which allows a channel of smooth air to run through the middle at higher speed.
Sounds counterintuitive but generally accepted as better than making ports very smooth.
Years ago these pages were full of this techi stuff and I used to enjoy reading and learning so hopefully you get good results and we can all take notice.
Funnily enough my car when fitted with an MBE Ecu at Powers had speed six injectors fitted.
I’ve never took much notice of them or even looked at the numbers on them but they have always given what feels like a very clean spray and fine combustion even on very light throttle openings, emissions are also very very low out of the exhausts but I’m not really sure if that’s just because it’s been mapped very well or the injectors have something to do with it or both.
This thread has reminded me and spiked my interest. I’ll take a closer look at them
Why would they make them otherwise.
Hopefully they correlate to better performance.
Having read quite a bit about porting it’s always been a problem with fuel running and pooling as it inevitably hits the inlet ports on the way to the combustion chambers.
Some inlets have a dimpled effect to avoid this and why it’s generally accepted rough porting works better than polished porting.
Even air can grab on smooth ports where as rough ports break up the area of grab and create a smaller wall of resistance which allows a channel of smooth air to run through the middle at higher speed.
Sounds counterintuitive but generally accepted as better than making ports very smooth.
Years ago these pages were full of this techi stuff and I used to enjoy reading and learning so hopefully you get good results and we can all take notice.
Funnily enough my car when fitted with an MBE Ecu at Powers had speed six injectors fitted.
I’ve never took much notice of them or even looked at the numbers on them but they have always given what feels like a very clean spray and fine combustion even on very light throttle openings, emissions are also very very low out of the exhausts but I’m not really sure if that’s just because it’s been mapped very well or the injectors have something to do with it or both.
This thread has reminded me and spiked my interest. I’ll take a closer look at them
Edited by BritishTvr450 on Wednesday 23 October 19:53
I'm not really sure I understand the logic of what you're attempting...
Is the idea to get rid of the fuel smell? Or to improve efficiency/performance?
You’re changing a regulator and injectors that will maybe be capable of a 1.3% reduction in flow rate. But it's the ECU really controlling how much fuel the engine gets (within the bounds of what the fuelling system is capable of).
If it's the fuel smell, where is it really coming from? There was a thread on here that suggested a couple of scoops under the boot floor are a possible solution (there were pictures and diagrams of them).
If it's efficiency/performance, I don't think you'll get anything without a remap, and with such a small change, I doubt you'll see any gains that a remap alone wouldn't have given...
?
Is the idea to get rid of the fuel smell? Or to improve efficiency/performance?
You’re changing a regulator and injectors that will maybe be capable of a 1.3% reduction in flow rate. But it's the ECU really controlling how much fuel the engine gets (within the bounds of what the fuelling system is capable of).
If it's the fuel smell, where is it really coming from? There was a thread on here that suggested a couple of scoops under the boot floor are a possible solution (there were pictures and diagrams of them).
If it's efficiency/performance, I don't think you'll get anything without a remap, and with such a small change, I doubt you'll see any gains that a remap alone wouldn't have given...
?
That’s been my understanding too but as Harvey points out he’ll check regulator performance and have a sniff test.
That sniff test might well suggest tweaking the map would then maximise the set up.
Higher fuel rail pressure and multi port injectors might add to better atomisation and fuel delivery which can’t be a bad thing.
Before I went to a later Ecu and bespoke map to my car I tried a number of different chips trying to remove smell and over-fuelling which didn’t achieve any real change at lower revs and general driving.
No other changes were made to my car when going to MBE other than the injectors and removal of the AFM which I’ve always felt removed an air pressure restriction and definitely resulted in a louder intake sound and my car has performed more efficiently at lower revs ever since.
Probably more advanced ignition and fine tuning the map.
This resulted in virtually no smell and low emissions.
As much as any power gains at high revs which are minimal on my set up my car has vastly improved in power delivery from tickover to about 4500 revs and economy improved.
This was exactly what I hoped for.
If Joolz is still mapping the CUX I’m sure he could improve this situation on that system too.
That sniff test might well suggest tweaking the map would then maximise the set up.
Higher fuel rail pressure and multi port injectors might add to better atomisation and fuel delivery which can’t be a bad thing.
Before I went to a later Ecu and bespoke map to my car I tried a number of different chips trying to remove smell and over-fuelling which didn’t achieve any real change at lower revs and general driving.
No other changes were made to my car when going to MBE other than the injectors and removal of the AFM which I’ve always felt removed an air pressure restriction and definitely resulted in a louder intake sound and my car has performed more efficiently at lower revs ever since.
Probably more advanced ignition and fine tuning the map.
This resulted in virtually no smell and low emissions.
As much as any power gains at high revs which are minimal on my set up my car has vastly improved in power delivery from tickover to about 4500 revs and economy improved.
This was exactly what I hoped for.
If Joolz is still mapping the CUX I’m sure he could improve this situation on that system too.
Firstly, my car has an MBE 9a8 ecu.
One of the reasons I'm changing the injectors is a simple 'because I can'.
2, removing a 3.5 bar regulator that's pushing the original injectors to 223ccm and fitting a 3bar regulator and 220ccm injectors will make near identical fuel delivery but in a more efficient way.
3, I've spoken to (due diligence) a mapper who specializes in MBE ECUs and fully explained what I wanted to do and gave him the various pressures and flow rates etc. he agrees, the car will be absolutely fine and probably a little better just by swapping the injectors and regulator.
I agree with him that in the future (not needed right now) the map is fine.
A look see at the map later may show improvements.
A very good friend of mine is an MOT tester. Couple of months ago we sniffed my car. It was running a little rich as sniffed directly out of the exhaust using a fully calibrated MOT test system.
When the injectors are changed I'll have it sniffed again. I very much doubt it will change to the point it's a problem.
I think it's going to be fine.
Powers performance think it's going to be fine.
Steve (can't remember his surname) MBE mapper thinks it'll be fine.
That's good enough for me.
Unnecessary explanation/justification over.
One of the reasons I'm changing the injectors is a simple 'because I can'.
2, removing a 3.5 bar regulator that's pushing the original injectors to 223ccm and fitting a 3bar regulator and 220ccm injectors will make near identical fuel delivery but in a more efficient way.
3, I've spoken to (due diligence) a mapper who specializes in MBE ECUs and fully explained what I wanted to do and gave him the various pressures and flow rates etc. he agrees, the car will be absolutely fine and probably a little better just by swapping the injectors and regulator.
I agree with him that in the future (not needed right now) the map is fine.
A look see at the map later may show improvements.
A very good friend of mine is an MOT tester. Couple of months ago we sniffed my car. It was running a little rich as sniffed directly out of the exhaust using a fully calibrated MOT test system.
When the injectors are changed I'll have it sniffed again. I very much doubt it will change to the point it's a problem.
I think it's going to be fine.
Powers performance think it's going to be fine.
Steve (can't remember his surname) MBE mapper thinks it'll be fine.
That's good enough for me.
Unnecessary explanation/justification over.
Edited by Harvy500 on Thursday 24th October 11:03
Edited by Harvy500 on Thursday 24th October 11:04
I’m not familiar with the MBE ECU and set up of your car, so bear with me, just some thoughts/questions
1 - do you run narrow or wide band sensors and if you do, are they trimming the fuelling?
2 - I can’t challenge your maths, I’d guess it’s near enough and when mapping once you’ve got a basic idle then you go from there. Changing injectors can be as easy using a scaling table for the revised figures for the ECU to operate them. So your logic/maths holds. Longer term though I’d absolutely want to change the set up in the ECU and remap.
3 - 3.5 bar on original injectors would I’d guess produce an absolute jet of fuel and the new injectors with 4 hole disc style will produce a greater atomisation conical pattern. I’d think the timing in the map can be optimised for the difference here and the amount of burn (efficiency) would change/improve.
4 - same amount of fuel without changing the timing, may not reduce the overfuelling you’re experiencing even if the fuel is more atomised.
1 - do you run narrow or wide band sensors and if you do, are they trimming the fuelling?
2 - I can’t challenge your maths, I’d guess it’s near enough and when mapping once you’ve got a basic idle then you go from there. Changing injectors can be as easy using a scaling table for the revised figures for the ECU to operate them. So your logic/maths holds. Longer term though I’d absolutely want to change the set up in the ECU and remap.
3 - 3.5 bar on original injectors would I’d guess produce an absolute jet of fuel and the new injectors with 4 hole disc style will produce a greater atomisation conical pattern. I’d think the timing in the map can be optimised for the difference here and the amount of burn (efficiency) would change/improve.
4 - same amount of fuel without changing the timing, may not reduce the overfuelling you’re experiencing even if the fuel is more atomised.
Edited by Johno on Thursday 24th October 21:09
Johno said:
I’m not familiar with the MBE ECU and set up of your car, so bear with me, just some thoughts/questions
1 - do you run narrow or wide band sensors and if you do, are they trimming the fuelling?
2 - I can’t challenge your maths, I’d guess it’s near enough and when mapping once you’ve got a basic idle then you go from there. Changing injectors can be as easy using a scaling table for the revised figures for the ECU to operate them. So your logic/maths holds. Longer term though I’d absolutely want to change the set up in the ECU and remap.
3 - 3.5 bar on original injectors would I’d guess produce an absolute jet of fuel and the new injectors with 4 hole disc style will produce a greater atomisation conical pattern. I’d think the timing in the map can be optimised for the difference here and the amount of burn (efficiency) would change/improve.
4 - same amount of fuel without changing the timing, may not reduce the overfuelling you’re experiencing even if the fuel is more atomised.
You can run with either narrow or wide band lambda. 1 - do you run narrow or wide band sensors and if you do, are they trimming the fuelling?
2 - I can’t challenge your maths, I’d guess it’s near enough and when mapping once you’ve got a basic idle then you go from there. Changing injectors can be as easy using a scaling table for the revised figures for the ECU to operate them. So your logic/maths holds. Longer term though I’d absolutely want to change the set up in the ECU and remap.
3 - 3.5 bar on original injectors would I’d guess produce an absolute jet of fuel and the new injectors with 4 hole disc style will produce a greater atomisation conical pattern. I’d think the timing in the map can be optimised for the difference here and the amount of burn (efficiency) would change/improve.
4 - same amount of fuel without changing the timing, may not reduce the overfuelling you’re experiencing even if the fuel is more atomised.
Edited by Johno on Thursday 24th October 21:09
Wide band requires welding a new boss in and then using blanking plugs in place of the narrow band lambda’s and yes trims fuelling up the complete rev scale as where low band trim until 3000 revs but it might be 3500 then becomes fixed.
Wide band allows you to intall an AFR gauge and read the performance where as low band doesn’t support the use of the gauge.
ETA this information is for the benefit of others.
Edited by BritishTvr450 on Friday 25th October 08:58
BritishTvr450 said:
Johno said:
I’m not familiar with the MBE ECU and set up of your car, so bear with me, just some thoughts/questions
1 - do you run narrow or wide band sensors and if you do, are they trimming the fuelling?
2 - I can’t challenge your maths, I’d guess it’s near enough and when mapping once you’ve got a basic idle then you go from there. Changing injectors can be as easy using a scaling table for the revised figures for the ECU to operate them. So your logic/maths holds. Longer term though I’d absolutely want to change the set up in the ECU and remap.
3 - 3.5 bar on original injectors would I’d guess produce an absolute jet of fuel and the new injectors with 4 hole disc style will produce a greater atomisation conical pattern. I’d think the timing in the map can be optimised for the difference here and the amount of burn (efficiency) would change/improve.
4 - same amount of fuel without changing the timing, may not reduce the overfuelling you’re experiencing even if the fuel is more atomised.
You can run with either narrow or wide band lambda. 1 - do you run narrow or wide band sensors and if you do, are they trimming the fuelling?
2 - I can’t challenge your maths, I’d guess it’s near enough and when mapping once you’ve got a basic idle then you go from there. Changing injectors can be as easy using a scaling table for the revised figures for the ECU to operate them. So your logic/maths holds. Longer term though I’d absolutely want to change the set up in the ECU and remap.
3 - 3.5 bar on original injectors would I’d guess produce an absolute jet of fuel and the new injectors with 4 hole disc style will produce a greater atomisation conical pattern. I’d think the timing in the map can be optimised for the difference here and the amount of burn (efficiency) would change/improve.
4 - same amount of fuel without changing the timing, may not reduce the overfuelling you’re experiencing even if the fuel is more atomised.
Edited by Johno on Thursday 24th October 21:09
Wide band requires welding a new boss in and then using blanking plugs in place of the narrow band lambda’s and yes trims fuelling up the complete rev scale as where low band trim until 3000 revs but it might be 3500 then becomes fixed.
Wide band allows you to intall an AFR gauge and read the performance where as low band doesn’t support the use of the gauge.
ETA this information is for the benefit of others.
Edited by BritishTvr450 on Friday 25th October 08:58
I run wideband on Emerald K3 and have done for 15yrs+, calibrated against Emeralds RR last year to check it's still accurate enough. My AFM gauge is installed in the glovebox so I can view if and when I need too.
I run open loop to make trim changes, but not adaptive so the changes aren't permanent to the map.
The reason I asked is that with the MBE as an aftermarket ECU I'm guessing you can view live data through some form of interface and check what the AFR is doing, if H500 is running a WB sensor then easy enough to check?
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