[judec]

Originally Posted by midlife

thanks for your input, but i am a little confused as to why you refer to RON. in the u.s., your octane rating is actually the average of ron + mon or (ron + mon divided by 2).

but if your calculations/formula is correct for RON, i can use it.
note that gas here is 89 RON which is equal to approx 85 u.s. octane.
using your calculations, (and assuming the "RON" you refer to is actually u.s. octane), then i have 89.5 octane which is still below the bmw recommended min 91 octane. but i am at least getting close.

i am just hoping this rumor about 93/95 octane is true, then i have one of my limiting factors taken out

Originally Posted by Calgary Agent

The member who quoted you the RON octane numbers is from Slovakia, where octane is measured using RON. A few countries, including the USA and Canada, use the avg (RON+MON)/2

I'd hold off tuning your vehicle until you can source fuel with a min (RON+MON)/2 of at least 89

Sorry to confuse U, guys. I just used RON instead of "octane" as I'm used to here in EU. But the calculation applies anyway. So - yes. U're getting close with effective octane of 89.5. If U happen to get 87 or 89, U're done. Just be sure when U go downside to sea level, count with the altitude compensation I mentioned. Better plan your route accordingly and if U can't get more then 85 octane gas, go with "empty tank" and get higher octane ASAP. with 85 octane closer to sea level your engine will start to knock.

[midlife]

Originally Posted by judec

Sorry to confuse U, guys. I just used RON instead of "octane" as I'm used to here in EU. But the calculation applies anyway. So - yes. U're getting close with effective octane of 89.5. If U happen to get 87 or 89, U're done. Just be sure when U go downside to sea level, count with the altitude compensation I mentioned. Better plan your route accordingly and if U can't get more then 85 octane gas, go with "empty tank" and get higher octane ASAP. with 85 octane closer to sea level your engine will start to knock.

1/thanks for your comments. by the way, are u sure about your formula: "for every 1,000 feet higher altitude, u need .5 less octane"??
i have heard that the formula was that for every 1,000 feet in increased altitude, you need ONE point of octane less.

2/ re engine knocking, i believe the 335 ecu is quite protective of any engine problems....if and when it senses any problem such as some knock, it will immediately pull (retard) your engine timing to eliminate knock problem.
if the problem is so big it cannot fully fix/compensate, it will put you into LIMP mode, and engine will basically run like on 30% power so you "limp" home.

3/ by the way, did u order a bmw and am waiting for it? or are you just a big bmw fan and r still saving up?

[leftcoastman]

The altitude = less octane formula doesn't work as well for turbocharged cars.

The theory with NA is that you are getting less cylinder pressure because the intake charge is less dense as you go up.

With the 335i, the turbos can overspin to compensate. Therefore the intake charge is just as dense. And in fact, being that the turbo is operating at a higher pressure ratio, you're likely to get higher temps, so it makes you need MORE octane.

[midlife]

Originally Posted by leftcoastman

The altitude = less octane formula doesn't work as well for turbocharged cars.

The theory with NA is that you are getting less cylinder pressure because the intake charge is less dense as you go up.

With the 335i, the turbos can overspin to compensate. Therefore the intake charge is just as dense. And in fact, being that the turbo is operating at a higher pressure ratio, you're likely to get higher temps, so it makes you need MORE octane.

i am not a motorhead, but i think you raised some excellent points... so i think i am really lucky to have the RPi intercooler sitting in my garage right now waiting for next week's install.

my limited engine knowledge (alot of forum reading, and some guessing) led me to buy an intercooler for:
more air, cooler air, lower temps, and if even 50% of what RPi claims is true
(25 -30 rwh) i will be a very happy guy. all this for approx $1300.

please comment and tell me if am my IC assumptions are corrrect for my 9,000 ft altitude and sh*tty 85 octane gas!

[Terry335]

Originally Posted by midlife

3/ i am not very technical, so i trusted terrry at juicebox who indicated that JB1 better for my situation. JB1 has lower boost than JB2 which both have lower boost than proceed. JB1 is probably similar to other tuner's LBT (for altitude) maps.

I always suggest JB1 for customers above 6000', as at that altitude with the ECU boost correction the JB1 and JB2 performance becomes very similar.

My concern with your particular setup was the low octane (I believe the equivalent of 87 US?), but I think you'll be OK.

[midlife]

Originally Posted by Terry335

I always suggest JB1 for customers above 6000', as at that altitude with the ECU boost correction the JB1 and JB2 performance becomes very similar.

My concern with your particular setup was the low octane (I believe the equivalent of 87 US?), but I think you'll be OK.

good to hear from u terry.
i believe my my 89 RON here is equivalant to about 84 - 85 u.s. octane... but because of my 9,000 ft altitude this may be equivalant to a few octane more (i do not know the actually "conversion" formula, but note that leftcoastman stated that with turbo motors, you need more octane at altitude than N/A engines).

terry, if u could tell me what my 89 RON at 9,000 feet is equivalant to (with a FI motor) if i was at sea level that would certainly make me feel better before my scheduled JB1 install and trial next week. note that my RPi intercooler is going in first.

lastly, i do not remember what the max ecu STOCK boost is for higest ecu altitude correction. please advise what this is and also tell me what the JB1 max boost at highest elevation is. very curious.

thanks

[Terry335]

Originally Posted by midlife

good to hear from u terry.
i believe my my 89 RON here is equivalant to about 84 - 85 u.s. octane... but because of my 9,000 ft altitude this may be equivalant to a few octane more (i do not know the actually "conversion" formula, but note that leftcoastman stated that with turbo motors, you need more octane at altitude than N/A engines).

terry, if u could tell me what my 89 RON at 9,000 feet is equivalant to (with a FI motor) if i was at sea level that would certainly make me feel better before my scheduled JB1 install and trial next week. note that my RPi intercooler is going in first.

lastly, i do not remember what the max ecu STOCK boost is for higest ecu altitude correction. please advise what this is and also tell me what the JB1 max boost at highest elevation is. very curious.

thanks

My pleasure Keith!

Honestly I'm not sure on altitude and octane. There are formulas floating around, but its not an exact science. I think the poster that suggested you'd be effectively on 89-90 octane is pretty close.

On the ECU it will adjust up to around 3psi, so say you're at 8psi stock, up there you'll see 11psi. The JB1 will add around 2.5psi on top of that, so you'll be at 13.5psi. But the actual PSI isn't that important as its the oxygen density that really matters... And the intercooler will help. I still think you'll be OK.

[midlife]

Originally Posted by Terry335

My pleasure Keith!

Honestly I'm not sure on altitude and octane. There are formulas floating around, but its not an exact science. I think the poster that suggested you'd be effectively on 89-90 octane is pretty close.

On the ECU it will adjust up to around 3psi, so say you're at 8psi stock, up there you'll see 11psi. The JB1 will add around 2.5psi on top of that, so you'll be at 13.5psi. But the actual PSI isn't that important as its the oxygen density that really matters... And the intercooler will help. I still think you'll be OK.

thanks terry... whether the JB1 is effective for me at my
9,000 ft with sh*tty octane remains to be seen. but whether it is effective or not, most appreciate your comments, concern and support...

i plan on installing JB1 next week (after my dealer visit for M sways install, hehe), so i will let u know then how everything works out.

regards