i dont really know where to post this so i thought this might be a place where i would get a solid answer. I just rebuilt my b18b with 9.8-1 compression pistons, do i need to tune for the compression change? or will stock ecu be alright? Everything else is stock with the motor.

-thanks, nick

 

Yes you will need a new tune doing something that drastic to the engine.

So replace the ecu with a tunable one.

 

can i just get chipped ecu for the change and be ok?

 

Yes.

 

chipped ecu with a basemap does not equal a tune.
________
Tdm850

 

so do i actually hae to take it to a shop and have it retuned for just a change in compression? and what would be a good tune-able ecu?

 

well,
To answer your first question yes, anytime you make a change that drastic you have to have it tuned again, cams, compression ratio, cam timing "with adjustable cam gears".

Generally on cars with a MAF "not hondas" like suburu's changing the intake you need to retune... but that's another topic/story.

well I would recommend getting a full NeptuneRTP package, you could probably get away with using an s100.


Honestly I would get a ECU with the ability to Real Time Program it such as Neptune.

www.Hrtuning.com read there its around $400 well worth it.. just do yourself a favor and do not invest in an SAFC.

 

if everything else is exactly the same as before no you do not need a tune simply for a compression change. Is it a good idea? Yes. however the compression ratio has very little to do with the fuel curve and also little with the ignition mapping. More power will be made with a tune, which is always the case even bone stock, so i would highly recommend it.

a 0.5 bump in compression is not a "drastic" change. Something like cams or stroke play a large role in the characteristics of the motor but compression is happening only when the valves are closed and the only difference in any other part of operation will be a slight difference in cylinder filling and clearing due to the different shape of the top of the piston. Even bolt ons like an intake or exhaust will effect the characteristics of the engine more than a slight change in compression ratio.

that being said, for a couple hundred bucks you can easily find a stand alone unit for engine management or do what I did and chip the ecu and then get an Ostrich real time programmer and tune the car yourself. IMO the tune is the most important aspect of performance and engine lifespan and its very easy to get good results.

lastly, like likwidchz (liquid cheese?) said, avoid the SAFCs they are complete garbage, but you dont need to spend 400$ on a mostly stock motor for something that I will guess you aren't using for any sort of competition purposes. for 200$ you can chip your ecu and get an ostrich then you just need to worry about some way to read air/fuel ratios which you would need to consider no matter which tuning route you take. or if you dont feel like doing things yourself then just chip the ecu and bring it to someone to tune, it will be very easy for a pro since little has changed with the motor.

hope this helps

 

thanks for all the responses. i plan on going turbo within the next few months, and was going to buy neptune rtp, but was unsure if i need to tune it since it was a slight change in compression. could i possibly start it on stock ecu just to make sure everything was ok with the motor?

 

Well it looks like Usuall71 knows a bit more about tuning then I do.. "Cool" I'm still learning although that is one thing I have always wanted to know was to see a fuel/ignition map change between a car with upgraded pistons and or serious set of cams what the ignition and fuel maps look like.

from what it sounds like you could probably use the stock ecu and it would compensate slightly for it... probably be fine for a bit...


Either way I like Neptune, but I'm sure if you get good at other tuning applications you would like it the same.

Good luck!


--Aaron

 

if you go turbo down the road then something like Neptune or eCtune is a very wise investment and you may as well get it now.

people run stock b20b (8.8:1) engines on stock b18b, P74/P75 ecus fairly commonly without serious issues.

you can usually find collections of bins on different tuning forums but I guess you wouldn't know for sure how good of a tune it is lol

 

for those that were interested i decided to start the car and run it with the stock ecu for now. it runs great and havent had any problems yet. i do however plan on getting a tuning system soon