Fuel questions

[samlloyd]

Whats the story with adjustable fuel pressure regulators and do i need one?

Currently just have a walbro pump with evo 510cc injectors in my RB, what sort of pressure do these pumps put out, and if theres more pressure in the fuel rail I imagine that theres going to be more fuel in the cylinder when the chamber opens?

Im not having any fueling issues at the moment, but looking at areas to upgrade.

And how do i find out how much KW 6x510cc injectors will support?

[Adydas]

510cc wont go a million miles to far, If you were having issues with fueling i think youd know by now =D

Take your tuners advice, My tuner knew hed need it and just installed it.. If he didnt he wouldnt..

Used this post to move this tech question to a more suitable area

[Akane]

Adjustable FPR is one way of getting more out of your injectors. you'll also need it if you run crazy PSI as there is a SLIGHT effect of the boost pushing / working against the fuel coming out of the injectors.

550cc x 4 = 2200cc makes 320hp @ ~40psi, so 510 x 6 = 3060, my wild guesstimate will say it's good for 450+ at around 40psi.

Or you could just use this injector calculator as Akane is famous for talking trash http://www.rceng.com/technical.aspx

[samlloyd]

Wont need to go a million miles, fuel isnt whats halting power. Its the turbo at this stage.

Would one day like to get 300rwkw, just wondering if 510s would do it?

[escortman]

510s should give plenty in a rb20 stil gota member theyr only 2lt, mates rb30det with t3t4, 7m 440ccs on 12psi got 280kw injectors didnt have heaps left but turbo ran out f puff at 4500 rpm ha

[samlloyd]

(it is a rb30det)

[postfach]

I think for a safe margin you would want to use 650cc+ injectors for that much power.

[escortman]

(it is a rb30det)

ahh then u maybe want a little bigger, he was going to run i think sard 650s or so with t70 turbo,

[matt dunn]

approximate rule for a 6 cyl is inj size = hp,

so 510cc injectors are good for 510hp on std pressure.

[postfach]

approximate rule for a 6 cyl is inj size = hp,

so 510cc injectors are good for 510hp on std pressure.

At the flywheel yes? That means they would reach 100% duty cycle at 320ishrwkw assuming 15% loss through the transmission+diff, and that would be best case scenario IMO.

If it were my car I would want a bigger "buffer"

[tsoob]

I think for a safe margin you would want to use 650cc+ injectors for that much power.

+1

510 will be ok up till about 280KW

[MAGN1T]

Me, I'd never take any tuners advice.

If you turn up the fuel pressure, it gives you more fuel at the top end.

It also gives you too much fuel at the bottom end and the ECU can't compensate properly..

Then people start threads like "why does my car use too much fuel".

The less you change, the less chance you've got of screwing everything up.

Steve

[escortman]

why wouldnt u take a tuners advice?

and im running slightly higher fuel press and my cars fine

fuel compsumption depends more on tune plus if he was worried about using heaps of gas hed prbly be driving a starlet

[MAGN1T]

why wouldnt u take a tuners advice?

From a total pricks point of view,
I've ben playing wit turbos for well over 25 years, modding cars for over 30 years.......... every "tuner " out there is only concerned with what's in my wallet..... they want it.........They think they know more than me....... just because to me it's only a hobby and I don't usually get my hands dirty.

My business is electronics.... going back....... building custom electronics for cars. Before computers existed.

Go figure?

Steve

[matt dunn]

Me, I'd never take any tuners advice.

If you turn up the fuel pressure, it gives you more fuel at the top end.

It also gives you too much fuel at the bottom end and the ECU can't compensate properly..

If you are trying to tune a car only by using the adjustable pressure reg,
which is a dumb idea.

An adjustable FPR is only any good in conjunction with a tuneable ECU,

and then they can help if your injectors are close to max,
or it can give you a slightly better safety margin for injector duty cycle.

and depends on who your tuner is and how well you know them.

If you dont trust your tuner you may as well DIY.

I trust the guys who tune my car,
but when they tell me it would be better with this or that they also explain why,

[MAGN1T]

I trust the guys who tune my car,
,

I tune my own cars.

On the road.

With NB oxy sensor.

And custom knock detector.



A lot easier than using the likes of a Gunsons colourtune (for multiple carbs) and a lot easer than doing plug cuts after a top end shut off.(did someone say "turbotimer?)

Once you "hear " knock, it's too late.

Really the V8 guys are still way ahead on tuning, in a lot of ways, they don't rely on computers.
Dynos only exist to rape your wallet and produce a fancy printout.

Steve

[4agtepwr]

How do you get a correct a/f reading with a narrow band o2 sensor because correct me if im wrong but an nb o2 sensor is very accurate
at 14.7 or stoich but not very good above or below that hence narrow band not wide band. How do you know when the engine is developing peak torque and your actully getting gains from the igniton timing your putting in? Dynos are a very useful tuning tool, not just for a fancy print out. And safer than road tuning to say the least.

Sorry to go off topic

[matt dunn]

I too have tuned cars,

also with a narrow nand O2 sensor,
and on the road, (race track actually but same stuff)

was about 5 years ago, and the car still runs great,
compete's in a lot of events, and they guy is quite happy with it.


but I have no doubt if it went to a better tuner with a dyno,
it would come back with more power, use less fuel ,
and do quicker lap times.

you must have a very sensitive butt to be able to get the best out of a car on a road tune.

[MAGN1T]

The best dyno tune is never the best track tune.

The best track tune is never the best dyno tune.

That's because the conditions are never the same.

Just think about it.

All the drag cars would go out on the track after a dyno and do their PBs.


It never happens.

The butt doesn't come into it ....about .86v on a good NB...... not a cheap charlie crap NB but a proper factory one...... they're not the same.

Steve

[mister2]

Rough rule of thumb for injector sizing:

200hp per L/min of flow, so 6x510cc = 3L/min = roughly 600hp.

Your Walbro will flow around about 3.2L/min on boost so these injectors will be pretty good for that (from memory, check the flow maps of the pump), so going for more flow from a adjustable FPR may be a waste of time anyway.

Flow goes up with the square root of the pressure too (eg, double the pressure and you only get sqrt(2)=1.4x the flow) so only really worthwhile if you were right at the limit of your injectors and wanted a touch more.

Also, we get a lot of people to remove their adjustable FPR's and go back to their factory one which works a lot better in most cases (cheap FPR's are terrible).

The best dyno tune is never the best track tune

Haha righto. Partly agree though that you may see differences in tune (ram air effects etc) which is why we will go out and check at the track if required. However there is absolutely no substitute for the flexibility or repeatability of a top dyno with excellent datalogging equipment.

If you want to be measuring AFR, NB is a waste of time. With how cheap Innovate Wideband gear is, it staggers me when people don't use it.