Rogeyboy

iTrader: (2)

Ive been using the following formula to figure out what injectors i want to run on my ms... Altho for the time being im going to stick with beiges.
Im somewhat confused...
Injector Size = (HorsePower * BSFC) / (#Injectors * DutyCycle) = flow rate of injectors in lbs/hr x 10.5 gives you the cc/min flow rate - correct?

According to this formula to get 130bhp from a cvh (standard power) you need 250ish cc/min injectors. Thats beige injectors (240cc/min) for standard power...?
You get cars running beiges at 180-200bhp, which according to the formula you need 380-400cc injectors...

Im confused, can anyone help?

Chip

iTrader: (3)

What values did you put into the equation when you calculated that? For bsfc etc?

Rogeyboy

iTrader: (2)

Sorry,
bsfc = 6
Duty cycle = 80

Can't get it to add up!

Rob_DOHC

iTrader: (4)

Your formula seems correct, your value should be 0.6 and 0.8 for bsfc and duty however that works its self out in your formula to give the same value of 250.

I seem to remember a calculator somewhere.....

Rob,

Rob_DOHC

iTrader: (4)

Here you go mate:

http://injector.com/injectorselection.php

I agree, it doesn't really add up. Running at 100% duty still only gives a power potential of 150(ish).

But, if you reduce the BSFC to 0.5 you get a power potential closer to 200bhp with 100% duty and 240(ish)cc injectors....

So in theory, a higher fuel pressure, better BSFC and a duty of over 90% maybe how people get close to 200bhp... plus some pub figure talk and a gammy dyno and their laughing!

In reality, a large injector is no problem. As long as its spray pattern is still good at small openings. The common problem with large injectors has always been a rough, rich idle...

Rob,

Chip

iTrader: (3)

On sequential I find 1000cc will still idle mint on a 2 litre, so equiv to 800cc on a 1.6, obviously on semi seqential like most MS users run though you'd want smaller by approx half.

So you may as well just whack a set of 400cc or so in there and have loads of headroom, it will still idle perfectly if mapped right and its not like you are trying to get through a cat test anyway.

Going back to the numbers I agree that 0.6 is probably a bit high, unless you are running very rich.

Rob_DOHC

iTrader: (4)

Hiya Chip! I owe you a txt mate sorry I didn't reply dude.

Which injectors do you use? I've been told that large modern injectors like Deka's or Bosch EV14's are still very good at low PW's but i havent put that into practice yet! Most MS users i know are still using batch fire, im yet to experiment with semi-sequential but will be on fully sequential next year. Need to have a catch up mate, maybe next time your lot are having ribs? I've got a few mapping questions I want to bug you with before i rent out a RR!

Rob,

Chip

iTrader: (3)

I like the siemens range of high impedance injectors, although I had 96lb low impedance rochesters in the nova when it was running a big power vauxhall engine.

Yeah would be good to catch up mate.

Mapping on the rollers is quite different. Matt @ Mtech is a bit of a drive from you but does some good deals on renting out his 2wd rollers and is very familiar with tuner studio if you get stuck, so might be worth giving him a call. Feel free to say I sent you.

Canada1

The formula works just fine.
The problem is that people with 130 hp cars are telling everyone that they have 200 HP.
240cc/min injectors will not make 200 HP - not even close. Especially on a cvh.

CasperR

Sorry to bum into this thread, but if im reading this right, my beige's wont get me my 200hp on MS, but i cant go big injectors, cause i still need to pas a cat test?
So how about rover 440 injectors.. or would i need some new ones?

Got a chance to buy some used ones.. what would be the best?
Bosch EV14 550cc
Bosch 444cc dyser
Siemens 630cc DEKA
Sorry for all the questions :S

Rob_DOHC

iTrader: (4)

I've heard nothing but good things about the Bosch EV14's and Deka 630's .

Rick on here uses the EV14's I believe? Karlos and a quite a few other use the Deka's

Rob,

Chip

iTrader: (3)

CasperR, for 200bhp, there is no need to go as big as a 630, that'll do 400bhp+

clarke5700

im running a set of 650cc loads of scail left im selling a set off 440 cc injectors and a set od saab 365cc's as well

Rogeyboy

iTrader: (2)

The beiges come as part of a "195bhp stage 2" upgrade for a fiesta rst, giving an estimated 180-200bhp, ive also seen rst's on the rollers running beiges at upto 210bhp! Ford also produced the fiesta rst with 180cc injectors making 133bhp, which doesnt work according to the formula
So what bhp are 440cc's good for? Karlos topped out at 230bhp with these - i find it hard to believe that you need an extra 200cc's of fuel to run an extra 20bhp!
Can i use MS to run my beiges for the time being?

Rob_DOHC

iTrader: (4)

Hello mate, MS will run any injectors you want, just stick with high impedance injectors and you'll be fine, the size won't effect you much.

Rob,

Canada1

Sorry mate, rollers are notoriously optimistic. Customers like BIG numbers.
The ratings given for "chip upgrades" are also very optimistic. Again BIG numbers make more sales - this is just sales and marketing tactics used almost everywhere.

The 240cc/min can be increased by increasing fuel pressure. Also upping the duty cycle over 80% can provide more potential power - although a reduction of injector life.

bomsch

iTrader: (1)

Canada1

lets take a look at your chart at 200 hp.
100 Lbs/hr = 1050cc/min
With 4 injectors at 100% duty cycle = 1050/4 or 262cc/minute.
This also assumes maximum efficiency - which a cvh engine does not have.

Kinda shows that a 240cc/min injector will never make 200+ hp in a cvh.

Take a look:
http://www.rceng.com/technical.aspx

This company knows what they are talking about.
By the way a cvh is very inefficient and the BSFC number is at least 0.6

bomsch

iTrader: (1)

Your calculations are correct, but it`s not injector size chart as you can read. Its gasoline chart. You may run 300cc with 500cc size injectors. But you only need that much gasoline to gain specific amount hp.

Canada1

Your are also correct, but the gasoline chart tells us how much fuel it takes to make a specific HP level (for a max efficiency engine).
Just shows a 240cc/min injector cannot make 200 HP (with 4 injectors) even on a theoretical basis.

Sure a 500cc injector can inject less than 500cc/min.

Rick

It's because beige's flow more than they are rated, the old Bosch injectors all do.

Rick

Rogeyboy

iTrader: (2)

Rick, that goes some way to explaining it.
I don't know how this fits the formula, but E16RST produced around 320bhp on 525cc cossie dark grey injectors....?
Perry i understand what you are saying but the figures just don't work - well i can't get them to anyway. A standard frst produces 133bhp which according to formula needs 250cc injectors, they only had 180cc injectors as standard so they mustve be around 90-100bhp? Im not trying to row with anyone, just trying to get my head around this.

bomsch

iTrader: (1)

Fiesta blues should be Weber 190cc as XR3i has.
Look my chart 4x190cc= 760cc/h 720-~15% (85% injector duty)= 646cc/h.
646:10,5 (lbs/h)=61,52lbs/h
Injectors duty % may be closer to 100%, so stock 130 hp in Frst case is possible.

Rob_DOHC

iTrader: (4)

Stock injectors won't be run any where near 100% duty, the only two things that could explain it are over zealous dyno figures or as Rick says, they flow more than they quote for. I'm not sure but the quoted flow figures of 180cc injectors maybe be at 2.5 bar? When stock fuel rail pressure is 3...?

Rob,

Rogeyboy

iTrader: (2)

It also gets more complicated lol, the stock injectors and power is based at 7psi, you can run upto 12psi on stock injectors (150-165bhp) and people regularly do with no probs, so that must be 100% duty!

Rogeyboy

iTrader: (2)

Perrys link
http://www.rceng.com/technical.aspx
Makes interesting reading but also works out, using the calculator that is on the page that to make 133bhp, you need 264cc/min fuel injectors - surely its not just me thinking thats well off the mark?

Canada1

It is not off the mark at all. I believe you have been believing very optimistic dyno tests or guys bragging how "big" their HP numbers are. The cvh engine is very inefficient and requires far more fuel to make the same HP as a 4 valve zetec for example. The cvh BSFC numbers are very poor.

Another possibility for extracting a bit more power is to raise fuel pressure. At 60 psi the 240cc/min becomes a 282cc/min injector. Even at a 100% duty cycle and 60 psi fuel pressure the max power is 180 hp.

Chip

iTrader: (3)

Ive only ever maxed a few set of injectors, but when I have done so on a 4 cylinder engine they have been at just under 80% of their CC rating in bhp.

So for 282 I would epxect to see under 226bhp
And for 240 I would expect to see under 192bhp

But thats on modern multivalve engines, so if the CVH is less efficient like you say (I dont know if that is the case or not, never tested it) then it would be less.

Rogeyboy

iTrader: (2)

Im just gonna throw the towel in and settle on the fact i can't get my head round this...
I find it hard to beleive that ford would quote the frst as 133bhp when in reality its sub 100bhp according to that equation... The only way i can think to explain this is that the equation is missing something or isn't linear!

Canada1

What are you talking about?
The formula does work for the frst.
I entered:
133 HP
4 injectors
BSFC 0.6
85% duty cycle

Result = 248cc/min injector

I think that's almost perfect?? What is the issue here?

Rob_DOHC

iTrader: (4)

The factory car only had 180cc injectors NOT 248cc injectors for 133bhp

Canada1

Well I think the 133 hp rating for a fiesta turbo is highly over rated.
180cc/min will not support 133 hp even at 100% duty cycle.

Anyhow, who cares - believe what you want to believe - I can't convince you.
The world is round not flat

Cheers

Rob_DOHC

iTrader: (4)

What? Why are you trying to convince me I'm not disagreeing.

I stand by my origional statements of over zealous dyno's and pub figure talk. However I don't think I would argue With the origional figures too much, they have been tested many times. So I would think ricks suggestion of higher than quoted flow figures may explain it.

Canada1

That might explain things.
Has anyone ever tested the factory frst injectors to determine if they are only 180cc/min?

Canada1

I found that the Fiesta RST was equipped with 197cc/min injectors - information given by a fellow on RS Turbomania forum.

Here is a good table for HP per injector at different flow rates and different BSFC numbers.
http://users.erols.com/srweiss/tableifc.htm#ITABLE

133 hp is very possible with 197cc/min injectors
Using BSFC # of .55
I am thinking for low boost pressures the BSFC #s are closer to NA BSFC #'s

The generic BSFC of .6 to .65 that some efi injector calculators use is to be safe and very conservative.
I must remember that these formulas work when the correct numbers are input.
The injector manufacturers (and speed shops) would rather err on the big side than small.
An injector a bit too large will not melt a piston, however an injector a bit too small certainly will.

For the high boost engines when we richen the mixture to prevent detonation the BSFC numbers do get into the .6+ range.

I think we have got it Watson.

Cheers

Rogeyboy

iTrader: (2)

Now it makes sense that the bsfc increases with boost...
Esp if the standard injectors are closer to 200cc/min!

Cheers Rob and Perry!

Chip

iTrader: (3)

Yes of course the BSFC increases as you go richer, it also increases even more if you end up with no ignition.

So a "safe" map will not be fuel efficient.

crazycage

when we had a set of cossie grey's cleand and flow tested they were over 600cc.
the same set of injectors are doing over 300hp on a 1600cvh

Rob_DOHC

iTrader: (4)

Good stuff, thank you Perry.