jvelos3

So I got a Turbonetics ST @ 5psi currently with a nismo exhaust. I got tuned at Sound Performance using UpRev and put down 330whp. I've already purchased the Agency Power single exhaust (coming in next week) and I was wondering if I need a re-tune. The nismo exhaust is already 3" but it's not as free flowing as the Agency Power. Will this affect my tune? I have a wideband so I can check the before and after AF ratios.

Blu_Blur

iTrader: (1)

Only if you don't want your headlight fluid to boil under boost.

jvelos3

Thanks man. Good to know

str8dum1

iTrader: (11)

there is more than enough closed loop correction with the stock ecu to compensate

djamps

iTrader: (1)

Boost is not closed loop unless you drive a GTR.

jvelos3

Yeah WOT goes open loop. Plus I have an 03 so no stock widebands for the ecu to read from.

I'll just double check the AF ratios after the install. It shouldn't make that big of a difference, especially since I'm only at 5psi and 330whp, but I just wanted to check on here.

djamps

iTrader: (1)

As long as the boost level doesn't change you shouldn't need a retune

taywan

iTrader: (53)

That shouldnt need it. I was at 5psi (same tn kit) and upped the boost(w some washers) to about 8-8.5psi now (well last yr) and no re-tune. Afr is still mid 10-low 11s. I def wouldn't sweat it.

2004Black350z

iTrader: (37)

do you get free retunes? Like my uprev i got 3 retunes with it. If so i would def get it retuned

jvelos3

No free re-tunes unfortunately. I did tell my tuner to make it a super conservative tune. Afterwards he told me that he could've made like 350whp but he stopped increasing the timing to keep it super safe.

Thanks guys for the input!

str8dum1

iTrader: (11)

how does uprev know you are boosting when there is no map sensor?



when does the stock ecu go to open loop, ie not use a target table?

djamps

iTrader: (1)

It doesn't know. Unless it's a GTR which also uses MAP.


Somewhere around 50% load it'll switch to open loop.. you can see it in the logs as correction % going to 100.

It always uses all the tables though; it just fuels blindly without o2 feedback in open loop.

str8dum1

iTrader: (11)

Ah, i didnt realize that the stock ecu went to open loop. My 1993 Geo does that so I figured newer cars would run entirely closed loop. My Proefi runs 100% closed loop.

rcdash

iTrader: (18)

Well it kind of does know it's boosting cause the BFS will exceed whatever corresponds to the 0 psi point... Haltech can be set to go to open loop at a set load (psi) setting to preclude slow compensations during rapid load transitions (i.e. taking away fuel during tip in). Closed loop usually isn't needed under heavy load. Ideally it would be nice if one could limit the closed loop feedback when under heavier load rather than applying the compensations available during low load to heavy load or just not having any compensation at all. As a compromise, I set my O2 compensation to range from -5% to +15%. That way, most of the time it runs on the rich side if the tune is off (vs the lean side).

psychoballistic

iTrader: (8)

I personally would get a re-tune regardless. Your changing airflow and back pressure, regardless of how slight, I am a firm believer that anytime something changes it is best to have it re-tuned to run optimal. Uprev is powerful stuff, but if changing an exhaust was all it took to gain power, then companies wouldn't offer flashes for intakes and exhausts. That is my $.02

Vivid Racing

iTrader: (67)

Going from the Nismo exhaust to an Agency Power single shouldn't make enough difference to require a retune. The computer has enough correction leeway available to compensate.

OP: Keep an eye on your boost levels and AFRs after the new exhaust goes on. If it doesn't change, you're good to go.

phunk

iTrader: (21)

just watch the AFs after the install. there is no definite answer to this question until you see the results.

psychoballistic

iTrader: (8)

I agree with what your saying, however as Charles mentioned, there is no clear answer. I am just a firm believer in constantly making sure everything is adjusted to run the car optimal all the time.

I had a friend with a turbonetics on his G and when he went to a turbo Ti-c from the stock (much more restrictive yes) he was leaning out tremendously. I would hate to ever see someone have something go terribly wrong because it slipped their mind to look at the afr while making a pull or something of the sort. Again, personal preference varies for everyone, that is just me.

jvelos3

Now I'm confused, when WOT the ecu goes into open loop so it dumps a preset amount of fuel depending on how much air the MAF sees while the timing is RPM dependent. A more free flowing exhaust allows more air to pass the MAF, confuse the tune, and possibly run lean? But shouldn't the tune be able to see more air, dump more fuel, and correct for this? I live in Chicago and I've done a few pulls at 20-30F and my AFRs were exactly the same as during 90+F heat. I'd imagine that 20-30F vs 90+F ambient temp would make a much larger difference for the MAF than an exhaust change, right?

psychoballistic, did your friend have the older version of the turbonetics with the 380cc injectors? My tuner was surprised that I only have 380cc injectors. According to him I was already running ~85% duty cycle at my power levels. He did tune me a bit on the rich side (11.2ish) but he told me if I wanted to run more than 5psi I should get a return fuel system and get bigger injectors cuz I was "maxed out" if we were keeping things on the safe side. Maybe the injectors just weren't flowing enough to allow the ecu to compensate.

rcdash

iTrader: (18)

I'm not certain if short and long term trims are active even under open loop fueling, but I think so. Anyway, if your AF ratio is under 12 you will be fine. You will make more power in the high 11s anyway. If you get into the low 12s, get a retune.