broken turbo

[West, David]

Greg,

Just thinking,

Maybe I am confused about the definition of duty cycle (%)

My duty cycle meter is a simple multimeter jobby that I think relates 
on time to off time as a %.

I thought that duty cycle is the % of time the injector is open 
compare to the time is can be open until it has to open again.

So as rpm increases the available open time decreases.

Therefore at 6000 rpm,

Assuming the injectors fire once every cycle (these actually fire 
twice on this motor) that gives 3000 pulses every minute.

Which equals 50 pulses per second
Which gives a maximum open time of 20 msec
Therefore 80% = 16 msec

Now at 1000 rpm - 8.33 pulses per second
Which gives a maximum open time of 120 msec
Therefore 2% = 2.4 msec

So from this I get 15% total power which equates to 30 hp (different 
from my other figure)

Now there could be any number of reasons why all this is total garbage 
and I sure, and hope, that someone will set me straight.

Kind Regards,

David West






-----Original Message-----
From:	bearbvd at sni.net [SMTP:bearbvd at sni.net]
Sent:	Monday, 21 December 1998 11:18
To:	diy_efi at efi332.eng.ohio-state.edu
Subject:	Re: broken turbo

>In a message dated 12/20/98 9:01:59 PM Eastern Standard Time,
>djwest at subcorp.com.au writes:
>
><< I am getting injector pulse width of 2.4 msec at 1000 rpm. This 
is
> more than 1/5 total width. Based on an engine that produces 200 bhp 
at
> around 6000 rpm this means that I am injecting enough fuel for 
about
> 40 hp. This can't be right.
>
No , it is not. At 1000 rpm, you are only getting an injector squirt 
every
120 ms --- so at 2.4 ms. PW, your injector duty cycle at idle is only 
2% or
so. If you have an injector duty cycle of 80% at 200 HP @ 6000 rpm, 
that
means that your idle HP is more like 5 HP, which is about right.

Regards, Greg