injector cc = what potential power?
 

right bit of a difficult one this probably one for the formula / maths wizards (raunch). 98bhp VTR picco (blue) what cc do they run at and what power (max before over doing the cuty cycle) can they cope with n/a and turbo?

also got some mi16 injectors which I know are 167bhp n/a standard form will cope fine for what I am after but I am thinking more ahead to mapping and how resolution will be like

I've got a formula in a book here - I'll post it up tomorrow morning when I've not had beers.

If you google it there's a few formulas knocking about.

I have it in a book somewhere in my room. I'll have a rumage around for it

I've got the formula in one of my progress threads as I worked out the max bhp for the 65lb injectors.

cheers guys ross, best you work it for me as my maths at the best of times aint that great

http://www.saxperience.com/forum/sho...&postcount=144

Pow :)

I'll do some maths tomorrow - slouching in bed with a cup of tea, The Rock on BBC1 after a few beers isn't best time to be whipping out your calculator and having a play with numbers ;) will pm you some workings 2mo

Happy Birthday btw :y:

I'll do it for you now if you like.
give me a min

Just a thought but if the mi16 injectors cope with 167bhp, then what duty are they running at?

If it's 100%, then they sound a slightly larger cc that the oem Vts injectors (225cc@3Bar) so they will be fine resolution wise easily for around 120bhp? What sort of bhp you hoping for? As ideally you don't want to run them over 80%duty.

As for the vtr injectors, not sure what cc they are, but I think they are around the 180ccmark? I'll have to try and find out before working out their rough max bhp@ 80% duty @ 3Bar on a boosted car

Quick bit of research, the mi16 injectors are 214cc@3Bar.

Making them well past their limit at a true 167bhp@3Bar. Just trying to find the cc of vtr injectors

yeah go for it guys any help you guys give me much appreciated

btw work it out at 3.5bar power wise was thinking 130-150 ish

check the saxo 106 turbo thread you posted mate, someone posted alot of injector info in there, model numbers and duty cycles etc, should have the info you need in there for 98bhp injectors

Right, I thought I'd post it in here so that if anyone else wants to insert some figures for themselves, they can do.

You can work out the injector size needed to hit a certain bhp figure:

Needed Fuel flow (cc per minute) = (Maximum BHP) x (A constant (roughly 5.6 for boost, 4.6 for NA)) / (Number of Cylinders)

So for say 160bhp with boost, you'll need (160 x 5.6)/(4) = 225cc injectors

To work out the size of injectors you'll need to keep a nice duty cycle, it is as follows:

Injector Static Flow = ((theoretical flow (from above formula)) x 100) / (Number of injectors per cylinder x Desired Duty Cycle)

So sticking with the 160bhp boost example, (225 x 100) / (1 x 80) = 281cc/min

Roughly speaking, with a 160bhp target in a turbo engine, you'll need injectors around the 280cc mark to keep a nice duty cycle at the max bhp point.

These are only rough calculations, and have been taken straight from a forced induction and performance tuning book.

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On a side note, you can work out the cc increase you'd get from upping the fuel pressure.

The formula is as follows:

Revised Static Flow = (Injector Static Flow (from formula above)) x (New Fuel Pressure / Old Fuel pressure)^0.5

So for example,

vts injectors at 3Bar are known to be around 225cc@3Bar, but what if we were to increase the fuel pressure to 4Bar?

Well, 225 x (4.0 / 3.0)^0.5 = 260cc.

So by upping the fuel pressure to 4Bar, you're effectively increasing the max bhp of the injectors at a nice duty - you can only up the fuel pressure a certain amount though - I personally wouldn't go above 4Bar.

If you put the above formulas into an excel spreadsheet then you can play about with figures and try and gauge the rough size of injectors you'll be needing.

Going back to the mi16 injectors, from looking online they look to be 214cc@3Bar so,

215 x (3.5 / 3.0)^0.5 = 232cc

Boost
232cc = (Max BHP x 5.6) / 4
which gives Max bhp = 165bhp

BUT ideally at that BHP, you'd have 290cc injectors at 80%duty cycle

NA
232cc = (Max BHP x 4.6) / 4
which gives max bhp = 201bhp

BUT at that bhp, you'd have 290cc injectors at 80%duty cycle

REMEMBER THESE ARE ONLY GUIDES AS TO THE INJECTOR SIZE YOU'LL NEED

legend thanks Ross :) so

140bhp x 9psi / 4 cyl = 280? either way I know I will have a decent safety margin on specs I wanna run

Going off this (http://mrinjectoruk.auctivacommerce....7-P598732.aspx) the vtr injectors are 154cc@3Bar (not sure if these are the 90bhp or 98bhp ones) , therefore:

Change the cc to a 3.5Bar FP:
154 x (3.5 / 3.0)^0.5 = 166cc

Boost
166cc = (Max BHP x 5.6) / 4
which gives Max bhp = 118hp

BUT ideally at that BHP, you'd have 147cc injectors at 80%duty cycle

NA
166cc = (Max BHP x 4.6) / 4
which gives max bhp = 144bhp

BUT ideally at that BHP, you'd have 147cc injectors at 80%duty cycle

you looking to run around 140bhp, but leave scope for future 'improvements' ;) ?

Also, I've updated the calc for the mi16 injectors for rough figures at 3.5Bar as opposed to 3Bar.

They are only meant to be used to spec up injectors that'll get you in the ballpark region size wise - the mi16 injectors look to be fine for boost upto around 150bhpish before the duty will get high.

It might be worth trying to check the spray pattern of the injector too - as the vtr injectors look to have a single spray pattern for a single port on an 8v head - whereas say vts injectors have more of conical spray pattern which I assume is for the 16v port setup in the head. Not sure how much difference it would make but every little helps, and it's worth considering before buying injectors

yeah 140 as solid and more for future :) I think mi16 ones will do for now and then I will use either clio 182 ones in the future if it gets spicey

I like the sound of spicey ;) pics or gtfo :cool:

Yeh the mi16 look like they'll be fine for now, but try and get a god spray pattern depending on what engine they are going on. 8v vs 16v

would you be able to do it for gti-6 injectors?