Just installed 315cc injectors, stock ECU, now not running right

[hungryforinfo]

Underpowered, rough as at idle, and wont accelerate, may also have a knock..

All brand new injectors, all plug and play.

I just remembered that I did not disconnect the battery when I did the installation, but I dont think that would necessarily make it idle funny, perhaps I should disconnect, to try and reset ECU??

 

[ruishy1]

is your engine standard or modified ?

 

[V8Datto]

I thought stock ecu and bigger injectors = more fuel

No wonder it doesn't run right, unless you've changed/modified something else?

 

[stevieg]

An ecu doesn't automatically know what injectors it's controlling, it's programmer to open an injector for a certain amount of time in milliseconds (pulsewidth) and different injectors have differing amounts of flow (ie flows 315cc of fuel per minute) if you pop in 25% bigger injectors they will flow 25% more fuel in the given pulsewidth ie running very rich, unless you have a standalone computer and you can scale your fuel map to compensate for the larger injectors

 

[Lextreme II]

You might be running little rich...

 

[hungryforinfo]

Figured it would run rich as..... LOL... Will try a reset, and swap my 02 sensors out, if that doesnt work then I will just swap back to the 251cc injectors until I go aftermarket ECU.

So there is no way a stock computer with a stock motor can handle 315cc injectors?

 

[zen]

why would you want to?
thers no point on a stock motor,it dont need more fuel...

and as far as i know there is no way the stock ecu on its own will ever run anything other than standard injectors..i dont think it will learn, espically in warm up/on power etc when runing open loop and hense from pre programmed maps bases on standard injectors.

now changing the fuel reg with a tuned engine will work, up to a point anyway..(ie one that ups the pressure when it sees boost on a turbo/sc engine)

 

[hungryforinfo]

I am putting a turbo on next weekend. Been planning it for months, but didnt want to do it all on one weekend, so just gradually doing it all. Standalone management to come soon too.

 

[hungryforinfo]

I must look a bit of a n00b here, but in the higher revs it goes okay.

Anyways, I was wondering if I got some Ethanol (E85 for example) and ran that, it might go alright, because, while it is a higher fuel volume, its probably on par with high octane normal fuel. Or am I just tuggin it.

Its only an hour to put all the 251cc injectors back in.

 

[4U2QUIK]

rofl, before you go slapping injectors in and turbos on you need some basic instruments before you do some serious damage. before doing any mods that involve fuel and air you have to have a wideband. Then move foreward from there.

 

[v8soarer_1991]

Does your plans include some form of fuel correction computer.

A basic SAFC 2 etc would do to lean the % fuel trim back to standard and the car will run as it did standard until you tune it with the turbo.

 

[v8soarer_1991]

missed the stand alone management part

 

[hungryforinfo]

rofl, before you go slapping injectors in and turbos on you need some basic instruments before you do some serious damage. before doing any mods that involve fuel and air you have to have a wideband. Then move foreward from there.

With the stock ECU I dont think a wide band or other sensor would be any help. Mine is a 4 wire oxygen sensor.

Anyways, it was just a test. Will drop stock 251cc back in and then get the turbo running sweet on them, while I research what ECU and tuner to use. Maybe I should look to piggy back or something in the interim.

 

[4U2QUIK]

your completely not getting the point. the wideband does nothing for your ECU. it's so you can use a tuner like a safc (piggyback) to lean out your mixture without messing up your engine. Don't even bother trying to tune your engine without one. you "WILL" Screw something up if you don't.

 

[hungryforinfo]

Well, injectors changed in 45 mins, driving to driving. Very cool, and easy enough to do.

 

[stevechumo]

315 cc injectors are way too much for stock ECU to compensate. It's about 26% larger than OEM injectors. As a rule of thumb on some stock ECU, it can only compensate for less than 20% of larger injectors than OEM injectors. You're definitely running too rich and you'll foul up sparkplugs, O2 sensors, and burn the cats. The car may seem to run fine at high RPM, although it has bad idle, starting engine, and accelleration, it actually doesn't run fine.

You'll need to have a piggyback ECU to trim down the fuel. And if you're not boosting, there's no need to run bigger injectors. Actually, when a stock car is tuned with a piggyback ECU, the fuel is normally taken out so the car just run better when running a little lean (less fuel) while still being safe.

A wideband O2 sensor is only used as part of tuning the engine. It can let the tuner monitor the condition of either being rich or lean of the engine. Other than that, it's no use at all.

 

[4U2QUIK]

well said.
But let's not downplay the need for a wideband if you're going to be doing any tuning.

 

[hungryforinfo]

315 cc injectors are way too much for stock ECU to compensate. It's about 26% larger than OEM injectors. As a rule of thumb on some stock ECU, it can only compensate for less than 20% of larger injectors than OEM injectors. You're definitely running too rich and you'll foul up sparkplugs, O2 sensors, and burn the cats. The car may seem to run fine at high RPM, although it has bad idle, starting engine, and accelleration, it actually doesn't run fine.

You'll need to have a piggyback ECU to trim down the fuel. And if you're not boosting, there's no need to run bigger injectors. Actually, when a stock car is tuned with a piggyback ECU, the fuel is normally taken out so the car just run better when running a little lean (less fuel) while still being safe.

A wideband O2 sensor is only used as part of tuning the engine. It can let the tuner monitor the condition of either being rich or lean of the engine. Other than that, it's no use at all.

Good info, thank you

 

[LP1]

I'm running 320 cc injectors with the stock ecu on a '95 SC400 to provide fuel for a M112 supercharger. The stock ecu has no problem adjusting the idle pulse width for the larger injectors. Idle quality is excellent and there was no noticeable change in the AFR.

 

[hungryforinfo]

If I ran E15 (15% Ethanol) So less "Fuel" being injected, plus had the injectors and the turbos, I am thinking I will be fine.???

What do you reckon?