ISC + Piggyback + 800cc injectors?

[gixxer750]

Ok, say in theory, I was running way to large of injectors(800cc or so) and a piggyback. And I was still using the ISC on the bottom of my FFIM.

What if, instead of hooking the ISC to an intake pipe on the other side of the TB to pull metered air, I didn't.

What if I just stuck a filter on the end of it? The injector duty cycle will be below 1 percent pulling all the fuel I can at idle with an emanage. So, if I introduce an amount of unmetered air at idle, that would help to lean it out.... correct? If it leaned it to much, I could always add fuel.

But, would the car run correctly, or is this just wishful thinking?

 

[gixxer750]

Thing is, I think the vac leak would lean it out at idle, not make it run richer....

The idle is what I'm shooting to solve here.

 

[starscream5000]

When you boost, isn't that air filter gonna blow apart?

 

[tissimo]

time for a real managment system

 

[cjsupra90]

with any type of air flow meter i think it will make you run rich, with speed density it will make you leaner.... i think it will be harder to tune with this leak than it will without... will the emanage not lean out enough for 800cc's? the ISC adjusts itself and so you will not always have a steady leak, and your afr's will be all over the place. the smallest leak affects afr's to an extreme I had a crack in one of my injector seals and you could not tell that it was leaking until you listened while the car shut off and it made my 14.7 idle jump up to 17-17.5

Other way around (sort-of).
AFM's = lean with less airflow thru them
Speed Density = no change.

Yes, it would infact cause a lean condition but I dont think that the car would even run cause there would be almost no (if any at all) AFM signal.

Pretty much 100% (maybe 98 to 99%) of the airflow into the motor at idle is thru the ISC valve, so chances are that there would be no airflow through the AFM and with no AFM signal, then the computer will never generate a injection event.

If I am understanding correctly what you are trying to do, (pull more fuel at idle then what the piggy back can do) then the way to do it is to do sort-of what you were thinking, but insted of just running the ISC on its own air supply, split the supply between its own filter and the original intake track ( i.e. post AFM but pre TB.) and use an adjustable valve in the NON AFM line after the split (see sketch below). This will allow you to bybass an amount of air around the AFM

 

[QWIKSTRIKE]

running e-manage? ultimate or no? you will just be creating a large vaccum leak and you will run rich at idle. when the throttle is open the isc will shut and you will be just as normal

you need to get engine management for injectors so large to run properly.Thats no tricking the ecu and other things to run flawlessly!

 

[KevinM]

I run a VPC and do just that. I can do this because I'm not metering the air, but rather measuring temp and MAP. Yeah for no AFM

 

[gixxer750]

I think I'm just going to buy an aem....

 

[cjsupra90]

I think I'm just going to buy an aem....

Probably your best bet, or any stand alone for that matter.

 

[TurboStreetCar]

WRONG! the isc is is BEHIND the throttle body. my previous statement stands, but yeah AEM is definatly the way to go.

WRONG! The isc is post AFM. the only way to make a mass air system run leaner is to have a air flow slgnal with less then original. only way to richen it is to have a higher reading the origional. If the ISC was open the AFM would count less air and the TCCS would put in less fuel to try to keep the right ratio based on the airflow tables.

look at the ISC as a second throttle body. putting a breather on the ISC will lean out the idle but like stated, 95% or more of the engine air flow at idle is threw the ISC.

If the ISC was PRE throttle body it wouldnt be able to controll airflow into the engine.

if your at the point where u need 800cc injectors, the stock ECU should not be controlling the engine anymore.

could also try lowering base fuel pressure.

 

[Doward]

I wonder if the MAFT-Pro, in SD mode, could handle it...

Not sure who is arguing what, but with a MAF based system, if you introduce any vacuum leak, you will run lean.

You have air coming in, that the MAF doesn't know about, and will not add fuel for = lean.

It's also why a boost leak makes you run so damn rich - air is being pulled into the engine, but part of it is leaking out - the MAF sees more air than is actually entering the chambers!

 

[cjsupra90]

.......Right soooo what was i wrong about? :dunno: like i said if it leans you out the leak will still be unsteady and a slight leak has large effects it will be amazingly hard to tune let alone with a piggyback, also when let off the gas and return to idle it will open to let air in causing yet another large tunning problem.

I owned a All trac celica with a map ecu and filtered isc. i recieved it in non running state, and fiddled with it for a few days WITH THESE EXACT PROBLEMS, it was rich one second and lean the next and when i tried to tune it out the idle would jump all over and i would start over, the car pulled hard, and i got the idle tuned out pretty well but it never met my standards. i ended up parting out the car because the body was shit and i was sick of it.

You are wrong cause you said that A leak would cause it to run rich where as it will actually cause it to run lean cause there is air entering the motor that has not been metered by the AFM. This is why AFM's typically have a bypass screw in them. This allows them be adjusted to correct for idle fuel mixtures to a small degree.

MAP (Speed Density) system will only increase engine speed if a leak is created if all manifold pressure ranges are tuned accuratly. The AFR will not chance and less the tuning tells it to do so based on the RPM and Manifold Pressure.

Idle quality will always degrade the moment that the injectors become larger then the cylinder displacement. Typically though, it is not noticable and or does not create tuning issues until the injectors get closer to 1.5 times the cylinder displacement. The problem is that injectors have a very hard time accuratly and consistantly metering fuel a very low flow rates or better stated, pulse widths. This is why there we have the option (with some system) of staged injection.

 

[starscream5000]

Boostadikt and nosechunks, it looks like you both are talking about the same thing what one of you says, "the isc is behind the throttle body" (in the intake manifold), and the other says, "the isc is post AFM". Post means "after" so that means the isc is after the AFM, and the intake mani is also post AFM... You two are talking about the same thing here, but you are not comunicating.

The AFM will not know what the hell the isc is doing because it only meters one way, and that's everything in front of it (air filter and adjusting screw) .

 

[TurboStreetCar]

star scream: no, theres no miscomunication, boostadikt said having a filter on the ISC or a vacumm leak will make the engine run rich, i corrected his statement.

noone said pre or post AFM, only the throttle body was mentioned.

Boostadikt: thats not what u were saying, u were saying a vacumm leak on a mass air system makes the engine run richer.

"a leak in the charge piping will cause you to go pig rich even at idle becuase it never sees much vacuum, and i am talking strait from experience and a wideband."
Again wrong, how can u have a huge boost leak at idle? wouldnt it make more sence that the engine will pull IN air threw the small hole because of the restriction of the turbo/AFM/filter?

heres the deal. AFM counts air, then tells computer how much fuel to put in. if u have a leak after the AFM, its either leaking in....vacumm leak.... or out...boost leak. if its leaking out itll cause a rich condition, alot of air bieng counted alot of fuel bieng added, but counted air is escaping. if its leaking in because of a vacumm leak or the ISC bieng open, itll count less air and put in less fuel.

your correct it would prolly be hard to tune, but u were wrong about how it will effect air/fuel.

 

[RacerXJ220]

Standalone.

 

[TurboStreetCar]

first of all, im not arguing, im correcting misinformation. its what this place is about, information and wrong information doesnt help anyone.

i didnt quote the second part because thats not what i was addressing.

i was addressing the fact that u claimed a divorced ISC would cause a rich condition.

starscream: i now see what u ment about the post afm and throttle body now, what i was saying about it bieng post AFM was that it wouldnt matter what side of the throttle body it was on. though it would only work on one side, since its post afm whereever the position, it would let in unmetered air.

also, on a speed density system, i dont believe a vaccum leak would cause a lean condition either. the vacuum leak would cause a slight rise in idle speed, witch would also be seen by the map sensor. together te rise in rpm and drop in vaccum seen by the map sensor would add in more fuel as if the throttle plate was slightly opend. the only problem i could see is the TPS still reading closed. anyone got any experiance with MAP systems and vaccum leaks?

 

[Justin]

I am kinda jumping in the middle here, but I thought the ISC was closed unless the TB was closed, then the ISC opened... am I totally off base here?

 

[Justin]

I am kinda jumping in the middle here, but I thought the ISC was closed unless the TB was closed, then the ISC opened... am I totally off base here?

Am I totally off base here?

 

[TurboStreetCar]

i believe you are correct.

 

[joliroger4]

Yeah! What jerk would go and run an ISC with big injectors and a vpc afc?!