i have a b18b and i want to throw on a ported head with crane cams and a bigger TB and IM of course. well my question is... if i do this, can i leave my ecu stock? i want facts please, not opinions .... thanks

 

yea u can leave your stock ecu but it will not benefit what you have put into the motor with a stock ecu.

 

That's not entirely true. You will see gains, but not nearly as much as you would see with a proper tune.

 

FACT:

Stock head/parts/engine = stock ecu

performance head/parts/engine = programable ecu


It's like saying, "is it ok to show up for the 100m sprint wearing my racing socks but wearing my everyday flip flops? I guess it is, but let's see how far you get with that combination.

 

not ok and dangerous, will likely run lean and hurt the motor if you push it.

 

It is definitely dangerous, especially if you go with aggressive cams.

 

i like that analogy. but im only planning to run a mild street build as to where i can still pass smog. the cams i have arent agressive and are suppose to be good for street.

but i thought the ecu will tune itself out as far as running too rich or lean, or no?

 

you can probably use a stock ecu to pass smog but it has very limited abilities to tune the fuel maps. Adding performance parts usually requires more tuning than the stock ecu can compensate for.

 

so then what are the max amount of mods i can do before the stock ecu becomes useless?

 

The basemap ecu is never useless... It depends on what you throw in that would then require some tuning. Tuning on all oem will still give you gains over the original basemap for the motor. Your question is to broad and it all depends on if you rebuild your internal with more aggressive parts.

 

i just want to be able to pass smog on these upgrades

 

In most cases, simple bolt ons are as far as you can go (Intake,exhaust) Once you get into cams, changing pistons, increasing compression etc, you need a tuning solution.

 

I think the stock ECU will just adjust to the lean condition by retarding timing, sacrificing performance and fuel economy for a safety margin. But close to WOT the ECU loses it's ability to make on-the-fly adjustments to respond to engine conditions, and it just runs straight off the fuel and ignition maps that are programmed in. If it's programmed lean it'll just run lean. If you do mods that lean out the engine you might be OK at partial throttles and low engine speeds, but it's definitely not safe to run large throttle openings.

 

Cams tend to change the MAP values causing the car to run rich. This will cause poor idle quality, poor emissions and tend to melt a cat fairly quiclky. Civics and Integras tended to be run off of what they called a "speed density" system where the computer used MAP and IAT values to calculate how much fuel should be injected. This was not a very forgiving system when upgrading parts. Mass Air Flow sensor systems can compensate much more accurately and tend to adapt better to performance changes on a stock ECU.

 

I guess I just assumed that cams leaned out the engine by increasing air flow. Thanks for correcting me.

 

Well you're not entirely wrong. At idle, the car runs rich but as rpm go up and the airflow is increased, the engine will tend to run lean as the stock ecu was never programed to adjust to that level of airflow.

 

so the answer is yes, i do need to chip my ecu and do tuning. thanks for all the info and help guys. anymore is welcome

 

The ecu will compensate for the increased airflow at part throttle,cruising conditions, and in closed loop status to a point...Once this "long term fuel trim" or LTFT reaches its limit,you will throw an o2 sensor fault. But thats not what you have to worry about..
Its the stock ecus lack of additional fuel at WOT that can hurt your engine...

 

so if i tune the ecu to run more fuel at WOT , can the stock injectors deliver the higher amount of fuel that is needed?

 

To a point yes.
Theres a formula at RC engineerings website that will help you determine what size injectors are needed with with X amount of HP..
http://rceng.com/technical.aspx?User...Pw2acz55SdwO9x

 

when do upgrades start to alter emissions so badly as to where i wouldnt be able to pass emissions testing ? anything that a good running engine and good tune cant help?

 

vtec killer camshafts, maybe ITB's...
I think a good tune and a functioning catalytic converter can make your honda run clean like it does stock...
It would have to be a really well tuned car probably with a 5 gas analyzer to get everything just right...
What type of testing do they do there? Idle/partial load testing?

 

im not sure what the exact kind of testing is done, but its done on the dyno.

 

anyone?