When is it at its max?

Peak torque or peak revs?

Alex

 

torque

 

The correct answer is neither of those.... !!!

Just writing out a long answer in a minute.....

 

depends what is meant really!

the period of each injector opening would be higher at the point of max torque but the total duration of injector open time per second of engine running would be higher at peak power

 

ah should have waited for a guru..

 

I know its a loaded question but I dont want to color anyones answer!

 

Peak torque will not always occur at max fuel flow rate !

It all depends on what size your injectors are compared to how much fuel you need to deliver, along with the compromise of how much additional fuel for transients and cylinder cooling etc...

It is maxed when the injection pulse time is greater than the time available between the points at which one pulse starts to when the next pulse starts.
This is quantified by a term called "duty ratio".

Any more than 100% and the injectors are continuously open and we CANNOT give any more fuel !

Different duty values can occur at different RPMs/Boosts etc depending on the mapping.

Injectors ideally should never go above 80% but this rarely happens ...LOL
(Stage 1 and Stage 3 conversions offten max out 100% )

Manufacturers tend to aim for 80% which is why basic remaps can increase power nicely


Duty ratio is calculated..... (for fully sequential injection 4 cylinders)


DUTY_RATIO % = (INJECTION_TIME / RPM_TIME ) * 100

Where RPM_TIME= (1 / (RPM / 60)) * 2000

[RPM_TIME and INJECTION_TIME are expressed as milliseconds]


An example.... (rough values)

803's at normal fuel pressure deliver around 360 bhp at 20 milliseconds pulse duration.
(This is a higher BHP than you though but as you have less RPM time the BHP will be less)

At 6000 rpm there is ONLY 20 milliseconds available maximum
Any more boost or RPM will lean off the mixture no matter what !

At 5000 rpm, we have more time to deliver fuel (24 milliseconds)

At 7000 rpm, we have less time to deliver fuel (17 milliseconds)

So on a normal stage 3 conversion, running more boost or higher RPMS will lean out the engine !

I hope this explains it ...LOL


SOMEONE PLEASE GIVE ME A JOB..... LOL

 

clear as mud lol, god i wish i understood these sorts of things

 

joffy,

Absolutely PMSL @ your signature

 

In terms of duration IN SECONDS on a PER CYCLE basis, at peak torque is where it will be longest (assuming you dont run massively rich AFRs just to one side of peak torque for some reason).

In terms of duty cycle as a percentage of elapsed time, it will be nominally at peak BHP

This is because although the fuel requirement drops off after peak torque, so to does the induction stroke timebase.


So basically, the injectors are flowing most at peak power, but open for longest each time they open and close at peak torque.
(assuming you dont max them of course!)

 

Chip,

The induction time base and fuel pulse rates will not both follow the same linear curve after peak torque !

Dont forget transient corrections can affect all results !

I guess it does depend in which terms thr original question is loaded ! LOL

 

you like the sig!!! 10 points for being the first person to comment (and i guess understand it)

 

Its loaded towards Chips answer...!

 

Im not forgetting that, hence my comment that you missed about afrs

What we are both missing is that efficenciey varies at different rpms, and 40lbs of air at 5000rpm may give more bhp slightly than at 7000rpm with the same airflow even for the same AFR, due to increased parasytic losses and also of course the fact that you might be hitting PCP too late in the cycle at lower rpm if its a high comp engine.

But the moment you take things like that into account, you simply can NOT give a generic answer at all

 

Most people think its to simple

 

indeed, everyone knows 1 + 1 is 10 surely?

 

is it not??

 

Chip,

I see where you are coming from and agree with you as you are viewing it purely as a normalised duration from a mappers point of view.

As I have experience in ecu hardware and software design (not just my own products)
I tend to view stuff as it really is in the "real world" and as in what is actually needed.

In total simplistic terms I guess that makes Gareths original reply correct...LOL

I guess too much info can be bad...

 

Only 10 points ??? I would have thought it was worth 1010 points !!!

 

i cant work that high,

 

1010 = 10??

Surly thats too logical!

 

Yes 1010 (in binary) = TEN

 

jesus alex it was a joke

 

1010bin out of 10dec for effort there simon

 

0 * 1 +
1 * 2 +
0 * 4 +
1 * 8

= 2 + 8 = 10


Clearly of the 10 types of people, you are the 1 that DOESNT understand binary

 

01000011 01110101 01101110 01110100

 

as quoted above, it was a joke chip

 

Actually, you are the Cunt

 

geeks

 

and proud of it

 

i seen that binary quote on a Tshirt years ago, and wanted one ever since LOL

 

dear god I teach Binary

I think I get the joke

 

that must be a lesson full of highs and lows LOL

 

Gareth....

 

it was bad i agree simon LOL