Nubaroo - Fuel system upgrade? - can only run 1.1bar/14pSI

Nubaroo · Post by **Nubaroo** » Sun Jul 13, 2008 5:39 pm

Hi guys. With my current setup of 4 x 500CC injectors and standard fuell pump I can onlyt boost safely up to 1.1bar/14PSI - quite a dissapointment I must say. I believe a Wallbro external fuel pump will help - the question is - what size injectors do I need for round 1.6bar?????

Herewith some vids of the car @ 1.1bar

http://www.youtube.com/watch?v=3I5eBTZlZtM

http://www.youtube.com/watch?v=YBPlWUng1ds

Nubaroo · Post by **Nubaroo** » Sun Jul 13, 2008 5:41 pm

PS - It made 232KW and 386NM on the wheels

exist3nce · Post by **exist3nce** » Sun Jul 13, 2008 8:53 pm

hahahaha nice videos!! Not sure about the injectors tho.

Nubira2.2 · Post by **Nubira2.2** » Tue Jul 15, 2008 3:25 am

it all depends on the horse power u r looking for not the boost
get a walbro 255lph intank fuel pump
that should help a lot with the 500cc injectors

Post by **PrecisionBoost** » Tue Jul 15, 2008 6:06 am

Personally..... I think it might be hard to get to 1.6 BAR without adding injectors.

If you go larger than 500CC you will probably have a hard time getting the car to idle properly ( I have slightly larger than 500CC injectors and the duty cycle often goes to zero to compensate for richness at idle... which causes the engine to stumble )

I plan on using 8 injectors..... the stock 4 Nubira injectors for idle and for anything under 0psi boost.... then as the car approaches 0psi the 500CC injectors start to kick in as well.

So effectivly I will be running 220 cc/min from vacuum to 0psi and then up to 725cc/min as the car moves into boost.

Additionally this is at 3bar of fuel pressure.... so if I rise the fuel pressure as the car goes into boost (RRFPR) then I can push that 725cc/min up into the range of roughly 895 cc/min at 4.5 Bar of fuel pressure

The cool thing about the 8 injector idea is that the car will get decent gas mileage when I'm not under boost and it should idle very nicely and stop fouling my plugs.

The Greddy Emanage has an option for another set of injectors.... so it should be fairly easy.... I'm making a new intake manifold with the Nubira injectors up near the cylinder head and the aftermarket 504cc injectors a little further back in order to take advantage of the fuel vaporizing and decreasing the intake charge temp.

So.... generally speaking here is the formula for injector sizing that I use.......

( Horsepower X BSFC ) / ( 4 X 0.80 ) = injector size in lbs per hour

BSFC should be around 60% to 65% for a decently built turbo engine

So..... lets guess that at 1.6 Bar your going to be around 400hp

(400hp)(0.65) / ( 4)(0.

= 81.25 lb/hr = 853 cc/min @ 3bar fuel pressure

(400hp)(0.60 ) / (4)(0.

= 75 lb/hr = 788 cc/min @ 3bar fuel pressure

So..... 850CC injectors if you plan to run safe and rich.... 790CC injectors if you tune it a little tighter.

Of course this is at 3 bar of fuel pressure so if you up the pressure you can decrease the size of injector required.

So... if you moved from 500CC injectors to say 675CC injectors and pushed the fuel pressure to 4.5Bar you should manage around 830CC/min from those injectors.

One popular option is to have just one single "big" injector mounted in the intake just after the throttle plate..... it works quite well.... but it doesn't guarantee a perfect A/F to each and every cylinder.

It is however the easiest way to get more fuel in there.

Another option is to add Methanol/Water injection.... that would help your Octane requirements while keeping temperatures down.

What Octane of fuel were you planning to use at 1.6 Bar???

I hope your aiming for something up in the 100+ Octane level..... if you don't have water/methanol injection and your not using race gas you might run into trouble.

Anyways... enough rambling... hopefully this helps you make some decisions as to where to go next

MMamdouh · Post by **MMamdouh** » Tue Jul 15, 2008 7:29 am

will the transition moment from the OEM injectors to the 500cc injectors cause a momentary "jerk" or something?? will it be smooth enough that you won't notice the switch process??

MMamdouh

Nubaroo · Post by **Nubaroo** » Tue Jul 15, 2008 3:42 pm

Thanks for the info Precisionboost - I am looking at definitally upgrading to a 255l/h fuel pump. My tuner says it is not advisable to up the fuel pressure as then the injectors take stain opening with the higher pressure??? I am planning on running AFGAS at high boost - 102 octane minumim, but the water meth idea souns good - no need to then swop fuel everytime |I want to run at high boost??? I have a 550cc 5th injector in my boost line which became obsolete when I upgraded to 500cc injectors - will it be OK to connect this and fuel with it just as an extra prcaution on high boost???

Pir0 · Post by **Pir0** » Tue Jul 15, 2008 5:37 pm

Why do you need 100+ octane fuel if you're running 1.6 bar?

I think i know a few people with cars like supras, and evos, running up over a bar on 96 octane fuel. Aka, super unleaded over here.

Not saying you don't need too, just want to know why? Don't know much about this subject.

Post by **PrecisionBoost** » Tue Jul 15, 2008 11:14 pm

One bar is just 14.7 PSI but 1.6 Bar is 23.5 PSI of boost...thats a very big difference.... I doubt you will find many guys pushing 24PSI and running 96 Octane.

If they are.... then they probably have a water/meth injection system.... or they are dumping in massive amounts of fuel ( 10:1 A/F ).... or retarding their ignition quite a bit.

Basicly as you add boost your Air/Fuel will ignite quicker.... so you either have to retard the ignition a bit or do something (such as running it rich or using meth/water ) to slow down the burn just a tiny bit so as to avoid spark knock.

So think of it this way.... as you increase your boost your "effective Octane" level drops.

So running 96 Octane at 15psi might be the equivilent of running 91 Octane once you add another 10 PSI of boost.

Post by **PrecisionBoost** » Tue Jul 15, 2008 11:17 pm

MMamdouh wrote:will the transition moment from the OEM injectors to the 500cc injectors cause a momentary "jerk" or something?? will it be smooth enough that you won't notice the switch process??

MMamdouh

No.... you can bring on the extra injectors fairly smoothly.... since the turbo takes time to spool up.

I'm not really transitioning.... the factory injectors will allways be running even under boost..... it's just that the larger 504CC injectors will start pushing in fuel as boost starts to rise.

Post by **PrecisionBoost** » Tue Jul 15, 2008 11:33 pm

Nubaroo wrote:Thanks for the info Precisionboost - I am looking at definitally upgrading to a 255l/h fuel pump. My tuner says it is not advisable to up the fuel pressure as then the injectors take stain opening with the higher pressure??? I am planning on running AFGAS at high boost - 102 octane minumim, but the water meth idea souns good - no need to then swop fuel everytime |I want to run at high boost??? I have a 550cc 5th injector in my boost line which became obsolete when I upgraded to 500cc injectors - will it be OK to connect this and fuel with it just as an extra prcaution on high boost???

I also have a Walbro 255LPH fuel pump ( the GMC Cyclone pump works perfect for an Astra MKII )

As far as the fuel pressure..... 3 bar is standard 4.5 bar won't hurt... as many injectors are actually rated that high.... but above 4.5 Bar can definitly cause problems.

The extra 550CC injectors effectivly is only adding 138CC to each of your 500CC injectors.... giving you 638CC.... which may still be a little on the low side based upon the calculations I gave you.

However....... your running 101 Octane.... so that makes a significant difference on the fuel requirements.

To be honest, I'm not sure what correction factor to use in order to accomidate the change in Octane

The water/meth mixture can also be mixed to help accomidate your fuel issues..... there are a few companies that make progressive controllers that will increase the flow of Water/Methanol as boost increases.