Shado

Hi people of scoobynet I just thought id ask the question what cc injectors would you fit to run say 400-500bhp. I've seen people using 650cc 750cc 800cc and 1000cc to achieve this power but why such a huge difference in cc. Is this down to mapper preference brand or just simply I need 1000cc because that's wot matey boys got.

Thanks in advance

stonejedi

iTrader: (51)

I'm tired so I cant be bothered to explain fully myself as it can be a long subject with all different variables but have a l@@k herehttp://www.onallcylinders.com/2012/0...injector-size/.SJ.

Shado

I'm not asking how to calculate flow rates. I'm asking why is there such a wide cc range to achieve the same power.

Let's say 05 sti wants to run 400-450 no internal work just turbo,exhaust,injectors,intercooler etc etc. some use 650cc some use 800cc etc why ?

Don't worry if you can't be bothered I understand

stonejedi

iTrader: (51)

If you read it it's the same principle to why people use different injector sizes,fuel pressure set up,injector duty etc... what I'm trying to say is you can have different headroom on different size injectors for say if you want to increase power more later on,you have the extra capacity to do so 650cc injectors will do 450+ but so will 1000cc injectors but at a different fuel pressure and injector duty cycle but have the headroom for 600 bhp where as the 650cc injectors would run out.SJ.

just me

iTrader: (3)

If you are going for that kind of power as far as I'm aware you will need a fuel pressure regulator for 650's but not with 800's (I have 800s no fpr).

Shado

So would a 1000cc drive fine at 450 with a low duty or would the 650 drive better as it's at a higher duty where it's meant to be surely the 1000s would be to big or not a optimum duty for the power bearing in mind that most sti's won't get treated to forge builds but will Remain at a safe ish level

Shado

so going off the fact of 2 replys is it correct to assume people don't know ie all we think is biggest is best ?

Linksfahrer

No in this case its not , For Headroom yes , but for spray pattern not always.

Best atomisation = best burn , So for efficiency a fine mist spray is preferable to a gush.

So it follows To flow the same volume of fuel :

Either gushing through a huge hole for a short space of time

Or a smaller hole pattern with a finer spray and or slightly longer period you will get a better air mix which ultimately should give you a better burn.

This situation is interesting at tick over , I have heard for example 650cc Detsch running better than cut off 440cc ( appx 800 ) even though the map was keenly adjusted for a good tick over.

I saw a video of this on a test rig for injector flow balance and the chopped ones spray pattern looks very pissy to say the least.

IMO Good even fuel atomisation always gives the best pickup.

Shaun

Could be.

Shaun

There is more than one way to skin a cat.

Some choose bigger for headroom, what they could get hold of (price etc), what the mapper has advised etc.

Shaun

A 1000cc can drive fine at 450 - although it depends upon on the injector (latency & spray pattern) and mapper.

Shaun

Some people may not know and some people may think biggest is best.

What other questions you got?

Linksfahrer

I think the best explaination is one in words and pictures

This link does it really well : Page 6 but its a great read.
http://www.enginemapper.co.uk/Engine...Guide_V1.1.pdf
hope Graham does another one of these his explanations are top class.