Arrow PCM question re: 91 octane and OEM PCM swapping for emissions testing in Canada

[Bruce H.]

Dick and Ralph both said the Arrow PCM was calibrated for 93 octane, and that "should" be used. The highest grade readily available around my home and home track is 91. My concern is running the car on a road course with 91, particularly in cooler weather, and avoiding pre-detonation with its more advanced timing. Anyone have knowledge or related experience with it under those fuel and operating conditions? Does the PCM have broad enough knock response to deal with lower octane and varying conditions?

We have emissions testing every two years in Ontario. My understanding was that you just need to swap in the OEM PCM a short while prior to smog testing, test, then swap back in the Arrow PCM. Is that it, and is it just plug and play or is dealer re-programming involved each time?

I suspect these may have been discussed eons ago when it was first released, but also interested in actual feedback with the combination of 91, cool temps and track use. Considering picking one up at NVE2. Thank you.

Bruce

[Stealth]

I am located in CA and we have 91 octane. I have the Arrow PCM, Corsa Cat-Back Exhaust and no other mods and a HPDE at a high speed track in 85F plus heat and had no problems--meaning I did not hear any detonation, did not go into limp mode, did not receive any error messages and did not notice any loss of power. However, it is certainly possible that the computer pulled some timing on heavy load, heavy heat situations.

My understanding from Mark J. is that it is fine to run 91 oct.; you will just not get quite as much power. As I have noted in different threads, I do not notice a night-and-day difference in power with the Arrow PCM, just better drivability.

[supersnake]

Bruce, Have you checked any Petro Canada stations? Out west last year they introduced 94 Octane here. Just run mine with the Arrow controller on 94 Octane. I think the power on a Stock Car is quite noticeable. And yes it is a plug and play. Un hook battery and change out, 5 minutes

[Dave1968]

Yah, Husky and Petro Canada have the 94 out here. I would say just add some octane boost when you fill up and you won't have to worry - problem solved.

[Canadian venom]

I'm using Petro Canada 94 and no problem at all with my Arrow pcm. In fact 94 is the only fuel I use in all my Vipers.:drive:

[Jabba954]

Since I don't want to add an additive to my fuel every time I fuel up in California (91 octane) - can anyone from Arrow or Viper Exchange respond to this thread?

[kblake905]

In Ontario you do not have to worry until your vehicle is 7 years old, and as long as there is no engine light it will pass.
They actually plug it into the obdb port, so removing the engine light wont work :t0135:
In Canada as I understand it; there is no ethanol in the high test (91 octane) unlike the states, not sure if that is a factor regarding engine codes?

[Rapidrezults]

I've run and tracked my TA with 91 (Arrow PCM) and now have also run and tracked my ACR with Heads & Cam package with 91. No noticeable side effects on either. I do, however, occasionally run Torco octane boost if the weather is exceptionally hot. (90+)

[Jack B]

Sort of a sidebar, does your car's acceleration surprise some of the track rats.



I've run and tracked my TA with 91 (Arrow PCM) and now have also run and tracked my ACR with Heads & Cam package with 91. No noticeable side effects on either. I do, however, occasionally run Torco octane boost if the weather is exceptionally hot. (90+)

[Dman]

I can confirm that a simple 5 min swap back to the stock PCM passes Maryland OBD2 plug in emissions test and I have Belanger headers and high flow cats with the Arrow. I just passed emissions with my 2013 about a month ago.

[Bruce H.]

Thanks guys. There's 94 at the track, but those pumps are only open for some events. I checked Petro Canada and really no stations in my area, but with some planning ahead, a couple of gas cans, and maybe some octane booster I can probably get by for the coolest and hottest days. Thanks for the emissions info, Kim, that makes me feel better. And good to hear you've track tested yours on 91 Chris.

[Arizona Vipers]

I run 100 octane at all track events, but it's hot here in Arizona. Order some Torco octane booster and be done with it...

[Coder]

Chevron in Western Canada runs 94 octane as their premium. I've used it in Alberta and BC.

[Canadian venom]

Bruce, I don't know exactly where you live but 94 is easy to find.... Try. With this link:

http://www.petro-canada.ca/en/locations/4085.aspx?MODE=RES&A=&C=&P=ON&PC=+&R=10&B=UL

[Garron]

Hi Bruce

Once programmed you can switch the OEM PCM back in, in less than 5 min if you were stuck.

My own viper has a 93 oct tune and no knock sensors. I have had to fill up with 91 if no 93 was available. I can confirm for a slow cruse home I had no issues.

You have knock sensors, if you fill with 91 the car would just back the timeing off.

[FLATOUT]

Bruce hopefully everyone here answered your question already. Yes 91 is ok to use, and the ECU can be easily swapped back and forth.

Andy

[Andi]

Attn AndyW or MarkJ - could one of you please pose the following technical question to Dick Winkles for us so that we can get a definitive answer on this issue. Thanks. Question below:

Do we understand correctly that the Arrow ECU is tuned for 93 octane (AKI)? If so, how much lower AKI than 93 can you safely go and still have protection via the knock sensor activated timing retard function? As some of our members live in regions where 91 AKI is all that is available, would that basically mean they'll be reliant on knock sensor activated timing retard all the time? Would you recommend this ECU for those members using 91 octane year round, and would it still be safe for a car that sees high-heat, high duty-cycle events such as track days on 91 octane?

[mjorgensen]

Attn AndyW or MarkJ - could one of you please pose the following technical question to Dick Winkles for us so that we can get a definitive answer on this issue. Thanks. Question below:

Do we understand correctly that the Arrow ECU is tuned for 93 octane (AKI)? If so, how much lower AKI than 93 can you safely go and still have protection via the knock sensor activated timing retard function? As some of our members live in regions where 91 AKI is all that is available, would that basically mean they'll be reliant on knock sensor activated timing retard all the time? Would you recommend this ECU for those members using 91 octane year round, and would it still be safe for a car that sees high-heat, high duty-cycle events such as track days on 91 octane?

The knock sensors will retard for the 91 octane as needed for normal use, but Dick would not approve of using 91 at the track or even in very high temp areas. We only have 91 here unless you buy race fuel and all of the cars we build and test are running 91 so with a good 93-94 they will run even better. I would not run a 91 fuel at the track either. with 93+ if you get a bad batch of fuel you still have cushion, if you are on 91 and get a bad batch you could have very expensive trip to the track.

[Stealth]

Mark: The OEM knock sensors should just retard timing wouldn't they? I have never heard any pings, etc. on 91 even running fast in the heat.

[mjorgensen]

Mark: The OEM knock sensors should just retard timing wouldn't they? I have never heard any pings, etc. on 91 even running fast in the heat. Yes but they are less aggressive than stock so it is possible to damage something with the right conditions and the wrong fuel.

[Steve M]

Mark: The OEM knock sensors should just retard timing wouldn't they? I have never heard any pings, etc. on 91 even running fast in the heat.

The problem with relying on the knock sensors to retard timing is that they have to detect knock before they pull timing, so the damage is already occurring. There's also a decay rate, so if it doesn't detect knock, it ramps the timing back in, starting the process all over again.

With the Gen 5, the forged pistons should provide some added protection, but it obviously wouldn't be ideal.

[Bruce H.]

Excellent information. Relying on a knock response system to compensate for low octane under extreme conditions does seem like rolling the dice. Although my access to 94 is a 45 min round trip from my home track, I can make it work with some gas cans and a full refill on lunch breaks on days when the track pumps aren't open. Carrying octane booster is also an option, as is swapping in the stock PCM if I'm in a bind or it's just too much of a nuisance. Other tracks I run always have 93 or 94 available.

So I can deal with it, and thanks again for all the replies!

Bruce