ECU requiring 100 RON Octane

[FlopShot]

I just acquired a Mine's Racing ECU for my JDM NA1, it's currently being shipped to the U.S. In reading thru the Mine's website, it seems that they tune their ECU for the 100 Octane fuel readily available in Japan. However, that would mean 100 RON octane, which is equivalent to about 95.5 AKI here in the U.S. I can get 93 everywhere, but 100 AKI is nearly impossible to find. I can add octane booster additive into the 93, but how much octane increase would that really get me, maybe 1-2 pts higher? How else can I easily get close to 95/96 AKI if I can't source any 100 octane fuel to mix together? And for those with experience running ECU's tuned for Japanese 100 RON octane premium fuels, will running straight 93 AKI be too lean? My NA1 3.0L is stock. Thanks for any wisdom that anyone can pass on!

 

[RYU]

In the documented cases i've seen on "tuned" NSX ECUs, this included JDM (Spoon, Greddy) and USDM (Dinan, Dali, Comptech) they mostly just up the timing by a few degrees. Doesn't amount to much in terms of power and might not be worth the hassle of having to run octane booster all the time. @MotorMouth93 is VERY familiar with hacking the OEM ECU (91-94) and can shed some light to your questions.

Not to be a Debbie Downer, but i'd rather have a tuned ECU from Motormouth93 that is configured to run aftermarket ignition coils, new injectors, and a safe AFR.

 

[Honcho]

@RYU beat me to it, but it's really just bumped timing in those JDM maps (including NSX-R).

 

[FlopShot]

In the documented cases i've seen on "tuned" NSX ECUs, this included JDM (Spoon, Greddy) and USDM (Dinan, Dali, Comptech) they mostly just up the timing by a few degrees. Doesn't amount to much in terms of power and might not be worth the hassle of having to run octane booster all the time. @MotorMouth93 is VERY familiar with hacking the OEM ECU (91-94) and can shed some light to your questions.

Not to be a Debbie Downer, but i'd rather have a tuned ECU from Motormouth93 that is configured to run aftermarket ignition coils, new injectors, and a safe AFR.

Thanks for the info. I don't think Mine's advertises increased power as their ECU is designed for the stock engine. Increased throttle response is their goal (along with removing the speed Limiter) which is achieved with "better" timing. But my question is really about whether I can get away with 93 + booster and not be too lean for the ECU expecting 100 RON?

 

[Honcho]

Thanks for the info. I don't think Mine's advertises increased power as their ECU is designed for the stock engine. Increased throttle response is their goal (along with removing the speed Limiter) which is achieved with "better" timing. But my question is really about whether I can get away with 93 + booster and not be too lean for the ECU expecting 100 RON?

Hard to know. It depends on the amount of extra timing. The other JDM chips run fine on 93, including the NSX-R. Honda built a lot of safety into the maps, but who knows what Mine's took out? Is it possible to contact Mine's and ask them?

 

[nigel]

Some smaller regional airports will sell their 100 LL fuel, it is 100 octane. It isn't cheap, down here in southern Fl. it's $6 50 a gal or so, to people with drive up fuel containers. Keep in mind it has lead in it but small amounts should be ok, shouldn't burn the valves, Or screw up the O2 sensors but I just wouldn't run it all the time to be safe.

nigel

 

[FlopShot]

Hard to know. It depends on the amount of extra timing. The other JDM chips run fine on 93, including the NSX-R. Honda built a lot of safety into the maps, but who knows what Mine's took out? Is it possible to contact Mine's and ask them?

Yes, I will be doing that. On their website they request the actual serial number of the ECU, so they can see specifically how that unit is programmed. So I need for the ECU to arrive before I can contact them. But the website also says they design the ECU specifically for JDM market because of the readily available 100 fuel, and thus they don't have any plans to design ECU's for other markets that have different octane ratings.

 

[FlopShot]

Some smaller regional airports will sell their 100 LL fuel, it is 100 octane. It isn't cheap, down here in southern Fl. it's $6 50 a gal or so, to people with drive up fuel containers. Keep in mind it has lead in it but small amounts should be ok, shouldn't burn the valves, Or screw up the O2 sensors but I just wouldn't run it all the time to be safe.

nigel

I did read that in an older thread about high-octane fuels. The trip to the small regional airport is about the same distance as to my nearest 100 octane pump (about 45 min) so this wouldn't really be a solution for me. But thanks for the suggestion!

 

[Old Guy]

And for those with experience running ECU's tuned for Japanese 100 RON octane premium fuels, will running straight 93 AKI be too lean? My NA1 3.0L is stock. Thanks for any wisdom that anyone can pass on!

Octane does not directly enter into considerations of, or affect the optimum air/fuel ratio. Octane determines the resistance to detonation and detonation is determined by combustion pressures and temperatures. The factor which usually drives the need for a higher octane is an increase in peak combustion pressure typically associated with increasing the compression ratio. Camshaft selection can also clearly influence the peak combustion pressure.

Some individuals may reduce the air/fuel ratio to reduce combustion temperatures to reduce the risk of detonation in the absence of sufficiently / impossibly high octane fuel. Dropping peak cylinder pressures and temperatures by over fueling is usually a counter productive bodge to fix a problem with getting over enthusiastic with setting the compression ratio.

If you trust in the knock sensors the ECU will retard the ignition timing if it senses detonation with the 93 R+M/2. That should leave you safe. Of course, if the ECU is retarding the ignition timing (potentially back to the OEM settings?) then you have to ask 'why bother with the ignition remapping in the ECU'. The reason that individuals do not report problems running 93 R+M/2 on remapped ECUs may be that the knock sensors are retarding timing to avoid problems. Personally, I think running an engine using the knock sensors to set advance limits is a bad idea. I favor running a safe no detonation ignition map with the knock sensors as back up. If you are going to operate using the knock sensors to set the timing limits then you would want to make sure that your 1991 knock sensors are in good condition and that the ECU memory remap didn't accidentally mess up the knock control algorithm.

If you want to achieve whatever hypothetical improvements are associated with the ignition remap, you are going to have to run higher octane fuel. I am sure that the fuel chemists have their empirical models; but, in general all octane ratings used to be confirmed by testing in a designated test engine. If it detonated, they would fiddle with the fuel components to eliminate detonation. So, I am not aware of a well defined empirical method for forecasting how an octane booster will affect a fuel's octane rating. Also, to complicate things, vendors may sell 93 R+M/2; but, those fuels may use different fuel blends to achieve the target octane rating in the test engine. Because of the different fuel blends, adding octane booster to give you 95 in one vendors fuel may not give you 95 in a different vendors fuel.

If you want to experiment with octane enhancers, I suggest Toluene. Toluene is already in the fuel because most refiners already use it as an octane enhancer. It has an R+M/2 value of 114. Its best feature is that it is generally much much cheaper than octane enhancers that you can purchase from auto supply stores. You should be able to source it from industrial or paint vendors in 1 or 4 gallon cans for less than $40 per gallon. You used to be able to find sources on the internet which purport to have an empirical guide to predict octane boost versus the amount of toluene added.

Toluene or other octane enhancers may work. However, from my perspective having to add a dose of octane enhancer every time I fueled up would get old pretty quickly. As a final note, my recollection is that toluene (and I expect the other octane enhancers) are not clear coat friendly. The clear coat 'safer' way to fuel is you dilute the toluene in a couple of gallons of fuel and then add that to the tank. Way too much work.

 

[FlopShot]

A friend told me to look up VP Racing Octanium Unleaded. Per their website, adding 2.6oz to 10g of fuel will boost the octane number by almost 2, which is pretty close to what I am looking for, yet remain safe for O2 sensors and cats (which I've removed anyway). It is just $21 for 32oz so very cost effective if using just 2.6oz each fill-up, way cheaper than sourcing 100 octane fuel at $11/g. So might give that a try.

 

[RYU]

If you're set on using that ECU might I suggest going one step colder plugs. I recently have experience with the factory knock sensors vs. a new set of Bosch units in my NSX with a standalone. The difference in noise was huge. Makes me wonder if those OEM knock sensors are doing anything at all and if so, it might only pick up the worse of the worse knock events.

 

[FlopShot]

If you're set on using that ECU might I suggest going one step colder plugs. I recently have experience with the factory knock sensors vs. a new set of Bosch units in my NSX with a standalone. The difference in noise was huge. Makes me wonder if those OEM knock sensors are doing anything at all and if so, it might only pick up the worse of the worse knock events.

Thanks. Any particular make/model of one step colder plugs that you recommend for the NA1? Did you go with Iridium? SOS has the NSX-R spec NGK plugs which are one step colder.

 

[RYU]

Iridiums are my choice. I'm sure the SOS ones will be fine if you ask me but if you wanted to get them locally it's BKR7eix. Those are one step colder than stock. Same one for the NSX-R and what I run on my high compression 3.6L ITB. Same as what I and many have run on mild boost. Some high HP guys go with the Iridium 8s

 

[Old Guy]

If you're set on using that ECU might I suggest going one step colder plugs. I recently have experience with the factory knock sensors vs. a new set of Bosch units in my NSX with a standalone. The difference in noise was huge. Makes me wonder if those OEM knock sensors are doing anything at all and if so, it might only pick up the worse of the worse knock events.

You need to be careful when comparing knock sensors. Some are tuned to a specific frequency that is centered on the dominant drum frequency of the cylinder (and some of the lower harmonics) and others have a flat frequency response. I used a Bosch knock sensor on another car. I think it was the KS4-P which has a nominal flat response from 5 - 15 kHz and an overall range range of 3 - 25 kHz. The Bosch picks up every bit of crap noise that is present in that range so the ECU must be equipped with input filtering tuned to the dominant knock frequency of the engine to remove the crap. If the NSX OEM sensors are a tuned sensor then if you are looking at the raw output of the sensor the OEM sensor may show little or no output until the engine is actually detonating.

 

[RYU]

You need to be careful when comparing knock sensors. Some are tuned to a specific frequency that is centered on the dominant drum frequency of the cylinder (and some of the lower harmonics) and others have a flat frequency response. I used a Bosch knock sensor on another car. I think it was the KS4-P which has a nominal flat response from 5 - 15 kHz and an overall range range of 3 - 25 kHz. The Bosch picks up every bit of crap noise that is present in that range so the ECU must be equipped with input filtering tuned to the dominant knock frequency of the engine to remove the crap. If the NSX OEM sensors are a tuned sensor then if you are looking at the raw output of the sensor the OEM sensor may show little or no output until the engine is actually detonating.

I don't disagree at all. While i'm not a huge fan of the AEM Infinity I'm using it does have a knock based configuration wizard to account for such things like bore size. I've got a dyno session on Tuesday and i'll be confirming the knock tuning range as per a knock sensor from Link that's been calibrated to my motor prior.

 

[Old Guy]

A friend told me to look up VP Racing Octanium Unleaded. Per their website, adding 2.6oz to 10g of fuel will boost the octane number by almost 2, which is pretty close to what I am looking for, yet remain safe for O2 sensors and cats (which I've removed anyway). It is just $21 for 32oz so very cost effective if using just 2.6oz each fill-up, way cheaper than sourcing 100 octane fuel at $11/g. So might give that a try.

Be careful with that! VP is a little bit underwhelming in their test information. That two point boost may apply to 87 R+M/2 gas. You may or may not get that two point boost if you are starting with 91 R+M/2.

Fuel chemistry as it applies to detonation resistance is a bit of a dark art. I am old enough to remember the phenomena of octane bump in the late seventies / early eighties when leaded gas was still available. With certain brands of gasoline, if you mixed unleaded regular with leaded regular, both with a nominal R+M/2 of around 87 you ended up with a blended fuel that had an R+M/2 around 90 or higher. It all depended on what the refinery was using to get the octane rating in the unleaded gas. Sometimes the chemistries were different and you got an additive octane effect. Sometimes you just had more expensive 87 R+M/2.

 

[FlopShot]

So just an update on this project. Got the Mine's ECU installed on Saturday. Added a few ounces (not an exact measurement) of VP Racing Octanium to an almost full tank of 93 fuel, and went for a test drive. Instantly felt the better throttle response, the car definitely reacts much quicker to throttle input. Revs higher before shifting (remember this is an automatic), not quite into VTEC mode but definitely lets it pull harder before shifting. Exhaust note seems to be better but that might be a placebo effect, although dumping more fuel could definitely have an impact on sound. Now for the interesting part. First time I put it into 2nd gear and did a hard pull all way up to about 6500 rpm, I caused a CEL. Immediately pulled over. Nothing sounded weird. Turned off engine and then restarted it. No CEL. Let it sit for a while with engine running to make sure CEL did not return, which it didn't. Drove cautiously for 5 minutes with no CEL. So proceeded to make a full more pulls to 6500-7000 rpm and never got the CEL again. My only guess is the octane booster had not yet fully mixed with the tank of gas, so the engine ran a little lean on that first pull? But after driving for 5 minutes the booster had mixed its way in? I have no other explanation. Second test drive on Sunday morning and no CEL after 40 minutes of driving. Overall impression is that the ECU is doing exactly what it is advertised, and I enjoy the increased performance of the car. Will need to make sure I allow the octane booster to mix sufficiently after I add it.