PCM-VEC question

[belgiumbarry]

i was again brainstorming on my :toilet: and came up with a idea.

now basic for my invention is the working of our PCM ...wether coupled with VEC3 or others.....

Does this clever boy a constant metering of the A/F to command the spraytimes of the injectors ? :dontknow: or are spraytimes just pre-programmed and adjusted within a range from A/F data ? Or no A/F data used in the PCM ?

I wanted to place it here before i go to ROE with my stupid question....

 

[mauiSRT/10]

Sorry I cant help ya.

patrick

 

[belgiumbarry]

oeps, is my question that difficult ? :dontknow: ......

at least 1 who admits not to know the matter...

BRAVE PATRICK :congrats: :congrats: :congrats:

50 peeps... :hmmmm2: arty:

 

[Marc T]

I can't answer that question, but you may want to wait on the VEC install.

I heard rumours that the Roe SC may eventually come with the SCT. I am currently working on getting my truck tuned with the SCT just got to figure the best method to control the Meth!!

 

[ZCx]

yep. spam spam spam spam spam spam spam spam spam spam spam spam spam spam spam baked beans spam spam spam spam spam

 

[Marc T]

yep. spam spam spam spam spam spam spam spam spam spam spam spam spam spam spam baked beans spam spam spam spam spam

:dontknow: :dontknow:

 

[FSTJACK]

Thumbnail, quick, oversimplified explination.

The "spray times" ie; pulse width of the injectors are controled by the PCM.

The PCM is a very powerful computer that takes into account;

Air inlet temperature

Coolant temperature, Ie; Engine temperature

Crankshaft position

Camshaft position

O2 sensor readings

RPM

Gear selection, (on automatics, and wheather torque converter is locked or unlocked)

Vehicle speed

Knock sensors, 05 and above on the SRT-10 trucks

Manifold pressure/vacuum readings

These inputs give the PCM the information it needs to run a program, ie; spreadsheet (oversimplified) that controls pulsewidth/spraytimes and timing.

That is in closed loop where a 14.7 air fuel ratio is desirable and ignition timing is advanced to the point of not causing excessive NOX emissions, or detonation.

In open loop, when cold or under wide open throttle, the PCM outputs are fixed with regard to timing and pulse width ie; spray times. This is good for power but does not allow for very good fuel economy.

There are different ways to change what the computer/PCM tells the injectors and timing events to do.

1) Reprogram/rewrite to the PCM/computer programmong itself as with the SCT.

2) Modify the signal from the sensors to the PCM so that the computer thinks it is seeing something else and makes adjustments based on semiprogrammable input from the various sensors by passing the signal through a device like the VEC.

Both of these methods allow you to gain a little more power on a stock motor or allow you to "dial in/tune" a modified motor.

Both work well and allow you to keep reasonable economy and driveability with out damaging a modified motor, due to being too lean or having too much timing at a certain set of conditions.

 

[Marc T]

Great explanation!!:rock:

 

[Prof]

Very nice Jack...good lecture...lots of meat and clarity there!

 

[belgiumbarry]

Thanks Jack :rock: :rock:

Now this was my idea , just have to inform me much better.....

There exists a LPG system which add's pump gas in case of shortness LPG, so to avoid the dangerous lean condition....

i turned it the other way around...would our PCM decrease pump gas spray, if i injected a small amount LPG ,to avoid a to rich condition ? :dontknow:

 

[pokeytemplar]

Not at wide open throttle because the computer ignores the A/F ratio and just uses its tables. That is when you are the most concerned of your too lean condition correct?

 

[ZCx]

yep. very well presented. spam spam spam spam. no beans

 

[FSTJACK]

Thanks Jack :rock: :rock:

Now this was my idea , just have to inform me much better.....

There exists a LPG system which add's pump gas in case of shortness LPG, so to avoid the dangerous lean condition....

i turned it the other way around...would our PCM decrease pump gas spray, if i injected a small amount LPG ,to avoid a to rich condition ? :dontknow:

The way O2 sensors read is different and they are calibrated differently, I think.

It would probably not work as there is a different stiochiometric (ideal air fuel ratio) requirement for different fuels.

To do what you are trying to do would only be possible at wide open throttle, and it would be quite a electronic engineering feat.

Get a programmer like a VEC and set your air fuels correctly, and smile all the way down the road...............



LPG runs at 15.8 to 1 air fuel ratio (stiochiometric). If you are calibrated for LPG, switching to gas would upset the balance to the lean side. Gasoline stiochiometric is 14.7 to 1. This would mean that you would need to run 2 separate O2 sensor systems.

 

[belgiumbarry]

it's not that easy i see.... my idea was to inject a little liquid LPG as with Meth injection to obtain a cooling effect. Evaporating LPG would take alot of heat away and makes a combustion mixture with the pump gas ....

I tought to inject it at TB so evaporation and air-mixing would be good pushing this trough the ROE blower before the inlets and pumpgas injection...

As i have the installation in the truck , but is proven to be not big enough for 500 HP , so sure not for a blown engine ( bigger LPG equipment doesn't even exist on our market ) , i could rather "cheap" try this out ....

Now the LPG was first evaporated by hot water from the engine and injected as a gas... so there's no more profit from the cooling heat it takes to evaporate...

Problems could be :

to rich as i inject a combustion fluid in addition to the pump gas....
Backfire ? as i have a "explosif" mixture already in the inlet - blower.....?

Further i think it can only help to raise the octane from the mixture as LPG has higher octane .

.... things to meditate between christmas and newyear...

 

[Prof]

Suggest you contact Joe at PBJ...he has built some viper engines using co2 as the coolant he might have some ideas for you...

He is on central time his phone: (314) 781-3135

 

[belgiumbarry]

i make tomorrow a calculation of how much LPG i need to evaporate in the inlet in relation with the inlet air fow to obtain a certain cooling effect.
This quantity can be regarded in relation to the approx pump gas needed at that time .....if this is only a little quantity , it can be done ... i think... just need a solenoid , injector connection and a window switch for experimenting in which rev's range i need the LPG injection... hehe.

So i can avoid injecting LPG at starting , idle ... also the amount LPG wil be fixed so cooling effect wil be max at "starting" rev ( let's say 2000 ? ) and decreasing with the revs...( more and more air , same LPG amount ) , but as i understood , the heating up by the ROE decreases also with revs , the more air "blown" , the less heat input....
On the other hand the warmer it is ( summer-winter) the more pressure the LPG tank is giving ( vaporpressure ) , so again when i need more cooling effect , there will be more LPG injected as the pressure is higher at the solenoid-injector.... yep.

I only hope i don't need much LPG , so the engine will only be runnig a little bit "richer" with the final mixture pumpgas+LPG , as far as the PCM doesn't decrease pumpgas spraytimes measuring a sudden richer filling ... which would be ideal ofcourse

A little to rich mixture can't do much harm i suppose.... but fouling plugs...

The only minor point is that the liquid LPG evaporates in the line , certainly in the hose in the warm engine bay... but that may not be a problem i think, when driving from parking or after cruising beyond the window switch lower revs i will inject vapor LPG for awhile up till the liquid has reached again the injector...but this will be minor as the content of the hose tank-engine bay is rather small.... ( small diameter will be sufficient i think.... )


please shoot comments for the ones still following :dontknow: