Moles Dad

Cant do that with me bl00dy boost controller

Andy.F

Er, em, yes. Just beware that your 0.5 bar increase will be a diminishing %age as the boost rises. ie 1 bar boost was 4 bar fuel, now 4.5bar so sq root of 4.5/4.0 x etc etc.
A further variable is that the fuel pump, even the uprated one (which we share ) is unable to maintain the increasing pressure requirement at full power type flow rate.

I would think the fuel map should be reduced on a sliding scale from atmo upwards

I run approx 5.2 bar fuel pressure at 1.7 bar boost with no injector problems. Your injectors are 15% bigger than mine so I don't see 350 bhp being a problem.

R19KET

Andy,

Given your power figures, I assume that your 5th injector must be working ? so 15% difference, is, or could be a little deceptive.

It's surprising how little more fuel flow you get, from increasing the fuel pressure. Like you say, a .5bar increase, only gives about 6% more at the top end.

Mark.

john banks

Thanks gents. The rising rate regulators would end up demanding really high fuel pressure at high boost then and the pump would not cope?

The odd thing with a static increase is that the effect wears off as you increase boost and hence pressure - thanks for pointing that out Andy. With a rising rate FPR then the greatest addition would to fuelling would be in the midrange fuel pressure, and since my map is MAF not MAP based I think it would be a real headache to correct, so I am better sticking with a static increase. How much static increase do you think I could run for up to 1.4 bar boost with the Walbro pump? If I go for 5 bar then that would be a +0.6 bar static increase - which is just a 6.6% increase in injector delivery and barely much more if I drop the boost, but presumably I would find a boost pressure that would keep the IDC at 85%-90% max? Depends on how rich I run it too

Does manifold vacuum (say -0.6 bar at idle) drop the fuel pressure with our cars? What is the standard cars offset from manifold absolute pressure to get fuel pressure - Is it + 3.0 bar?

Thanks for all the help guys.

Thanks for the link Stevie - I have joined Autospeed already but hadn't found that one. Cheers.

[Edited by john banks - 7/13/2002 11:56:25 AM]

R19KET

John,

I've just checked the pump flow map, and at 6bar/90psi fuel pressure, the pump will still flow 190 lph..... (42 gallons) based on a battery voltage of 13.5.

These pumps are good for 450bhp +.

Mark.

john banks

What is a sensible maximum pressure for the injectors though? 5.0, 5.5 bar? In an Autospeed article they were tested to 5.5 bar without event and a good spray pattern. That should be enough

[Edited by john banks - 7/13/2002 2:10:55 PM]

Andy.F

Interesting spec on the pump Mark. I must try winding the pressure reg up more I thought mine was starting to peak at around 5.5 bar, maybe need a stronger spring

John, the fuel press reduces with vacuum, usually about 2.4 bar at idle. The best way to set it is with the signal line disconnected and the engine running. You can set it with the engine off and just turning the key off and on but your battery voltage will be higher with the eng running, that may change it 'slightly'

Of course you could just settle for an AFR of 12.5 It's good enough for 517 bhp on the reyland cossie !

Andy

R19KET

Andy,

"Of course you could just settle for an AFR of 12.5 It's good enough for 517 bhp on the reyland cossie !"

Interesting, so are you saying that if I run an AFR of 12.5:1, I will also get 517bhp ?

Mark.

john banks

+- 50 BHP

Pavlo

doesn't the adjustable non rising rate regulator maintain a fixed pressure relative to manifold?

Would this be the same increase over standard throughout boost range?

Just curious about the "%age increase diminishes with boost" statement.

I had some thoughts, but will wait for response.

Paul

ustolemyname??stevieturbo

iTrader: (1)

Something to consider about increasing the fuel pressure, is that the temperature of the fuel will rise. If pushing the pump to its limit, then if the fuel gets too hot, then it can also cause det. I am not sure what temperature is actually critical, but something to take note of.
I have noticed, in my rover V8, with a big pump setup ( low press pump, feeding 2 ltr tank, feeding high press HUGE efi pump ),
that the fuel is actually getting warm, both in the swirl tank, and the main fuel tank. Not good. Might have to introduce a fuel cooler somewhere

Andy.F

"Interesting, so are you saying that if I run an AFR of 12.5:1, I will also get 517bhp ? "

Mark - Stop taking the p1ss I mean that there is no need to go as rich as many tuners do for 'cooling' purposes

Steve - If you recirc round the main tank, you will not build heat. Continual pumping of a small volume at high pressure will eventually heat up. I suggest your 2 litre tank should have a spill back to the main tank to overcome this.

Paul - The %age of additional flow will decrease with pressure. With a fixed pressure rise, the %age above standard reduces as the base pressure increases. 1 bar + 0.5 = 50% increase. 2 bar + 0.5 = 25% increase. 4 bar + 0.5 bar = 12.5% increase and on and on.
The new flow rate is increased in proportion to the sq root of the differential pressure.
I'm sure you already know this, I probably didn't explain it very well first time

Andy

Pavlo

Andy, that's what I though, but:

The fuel pressure is raised inline with the boost yes? So nominally 3bar at atomospheric.

If you rais by 1 bar, so 4 bar at atmospheric, that's a 33.33% rise. But you say only a 25% increase when at 1bar boost (was 4 bar, now 5).

However, the fuel flow is determined by pressure differential accross the injector is it not (fuel pressure - manifold pressure)? So nominally you are alway 3bar above manifold pressure, so if you raise to 4 bar, you will always be 4 bar above manifold pressure.

So i would have thought that an increase in pressure using a non rising rate regulator creates the same increase accross the manifold pressure range. This ties in with the ECU mapping, which doesn't know about boost pressure or fuel pressure, and assumes that the flow is always the same.

Paul

john banks

I see what you are saying Paul, and it is also more optimistic about how much more you can get out of the injectors if I am not mistaken.

Andy.F

You're absolutely right Paul I'm talking fuel pressure not fuel/boost differential pressure

So there IS a linear rise in fuel flow (%) proportional to the sq root of the pressure difference.

I get even more confused when I try to work out what's happening with my 'rising rate' regulator

Andy.

Pavlo

John, I would talk to Stephen if I were you, I think he should have found the fuelling constant by now. You should be able to adjust that and compensate for larger injectors or higher fuel pressure. That way the map stays unaltered.

Paul

john banks

Thanks all, think I got my head around it all now, and the extra I can get out is more optimistic than we thought.

R19KET

What it boils down to, is if you're looking for an extra 5~10% of fuel, you can get away with upping the fuel pressure, but any more, bite the bullit, and get the right size injectors for the job.

Mark.

john banks

OK Mark, so 8% increase is 0.5 bar static. Will see how I get on.

dowser

John,

Can I assume that DeltaECU doesn't offer an automatic option to redo the map to cater for different fuel-flow (injectors/pressure) then?

Thanks
Richard

Pavlo

You can do it on the older ECUs, so I don't see why it can't be done. Just a case of knowing where the constant is to change it.

Paul

Bob Rawle

Map scaling can be done to accomodate injector/fuel pump/fuel pressure changes just like any other ecu, Don't forget Jecs is maf based and the load points are Calculated Load Values relating to rpm, tps and maf. Compensation factors apply according to air and coolant temp and battery volts for starters.

Pavlo

Are you sure about that? I am pretty sure the fuel and ignition maps are purely airflow based, although there may be further compensation in a different process.

The boost and duty cycle maps seem to be purely TP based, as you can be at the max load point at <1000rpm if you floor it.

The 94-96 ecu I am working on has a 16bit value used to set the fuelling for a given airflow, so you can change this to make the 80h on the map be stoch for a different injector.

I don't yet know if the constant is inverted, so you might have to move it either way. I will confirm shortly when i have the goodies to poke the ecu from laptop.

Paul

Bob Rawle

Absolutely certain .... the maps are not air flow based but CLV based ... calculated load value but that only picks the point, what is at the point is entirely adjustable.

john banks

On the Phase II ECUs (you are talking Phase I Paul), agree the boost and duty cycle maps seem to be directly off the TPS from what I can see - the values seem to be directly off the TPS sensor voltage through an 8 bit ADC. The load values have no direct resemblance to the MAF sensor values that I can discern - a 16 bit MAF value is established from the MAF voltage from a table. What it does with that to get a load value from 0 to $28 or $30 or more (depending on how quick your car is) must be the CLV stuff which remains obscure to me, and Bob suggests it is multivariable. Given that you can go lean on part throttle with a Dawes it cannot be purely MAF certainly, but also not purely TPS. As Bob has said there are a lot of secrets for JECS still to give up and the Denso ECUs sound rather interesting too.

Pavlo

I was talking generally, as the maps are scaled the same on phase 1 as phase 2.

Paul

john banks

If I increase fuel pressure by a static 0.5 bar at idle I will increase to 3.5 bar so the fuel flow for a given IPW will be 100(((3.5/3)^0.5)-1)= 8 % higher making my 440s like 475s. Do you think I should go across the map and multiply by 100/108= knock off 7.5% from the cruise and lambda areas to avoid seeing lots of negative air fuel correction? Since the values in the map are AFR targets with a base of $80 for 14.7:1 then I presume that a map ratio of 15.9:1 would suit the 8% higher flow for the same IPW to get a genuine 14.7:1? Presumably you can adjust for larger injectors in a similar fashion? How far is sensible to crank up the fuel pressure? Any other tips? Thanks all.

[Edited by john banks - 7/12/2002 10:40:24 PM]