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Old 01-28-2006, 08:32 PM   #1
powerlabs
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Default Its official: We lose power with low octane gas.

OK, so we've all heard about how JDM engines are designed to run 96 octane, and how they make less power on anything other than that, and how JDM engines in the UK make less power and occasionally blow up because they don't have 96 octane there and so forth...
Well I thought my V5 WRX Type RA was running decent now that I swapped my plugs... But it just didn't feel *that* fast... I remember it being incredibly fast before, and now it just felt pretty quick...
So I did some testing; same road, same road conditions, etc etc... Chronographed (By Apexi Rev/Speed Meter) 60 - 100km/h run (notice this does not involve launching or shifting, so it eliminates uncertainties provied I always do it in the same spot on the road):
2.26 seconds BEST, 113mV of knock.
Then add 2 gallons of Turbo Blue 110 Leaded to the tank:
2.11 seconds right away (first try), 12mV knock. The car feels *MUCH* faster.
So I have been able to RECORD that, yes, the engine IS seeing knock on 93 octane (albeit mild; I've seen 220mV on a warm day and even that was inaudible), and that this is having a SIGNIFICANT effect on power. Race gas dropped knock 10 fold and allowed the engine to accelerate the car significantly faster. It would have been about 1/2 a second quicker on the 1/4 mile, possibly more.
The result? Your 280HP JDM engine DOES NOT MAKE 280 HORSEPOWER ON 93 OCTANE. No way. Absolutely not. Modded engines are probably taking an even bigger hit. The engine is knocking and the knock is causing the ECU to pull timing, or boost, or both and reduce horsepower as well as run the engine less efficiently. The scary part? Your engine HAS to knock before the ECU will do anything about it.
More importantly... If you have a swapped car and haven't tried putting at least some race gas on it (2.5gallons of 110 on an otherwise full tank of 93 will net you over 96 octane) you don't know what you're missing out on; the difference is HUGE!

Disclaimer: This only happens because JDM engines are DESIGNED to utilize higher octane. Putting race gas on your WRX/RS/Whatever else with bolt ons will do nothing more than cost you extra money; an engine designed to run on 91 octane will not see gains from any higher octane than that.

Disclaimer 2; leaded gas will harm catalytic converters and O2 sensors. I have a resonably expensive Bosh Wideband O2 used by my PLX Devices M-300 Wideband Air/Fuel Ratio monitor (which, incidentally, also outputs a narrowband signal so my ECU can run closed loop) and running lead will cost me a replacement of that sensor. I expect the sensor to clog between 30 and 60K miles of use. Normal replacement intervals are 60 - 100K miles.

I'll post some test results with octane boosters. From my preliminary analysis I can say that they work to some extent but don't compare with race gas.
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Old 01-29-2006, 12:04 AM   #2
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good info! keep testing, and maybe better stuff will be available for us!

I'm glad i did a usdm swap
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Old 01-29-2006, 01:50 AM   #3
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uh, japanese "96" or "100" octane gas is measured in RON. ours is the average of RON and MON if you believe the pumps, or anti-knock index if you believe other sources. http://www.kingshosting.com/~bmaddre...sue6/p12.shtml in any case the nominally higher octane fuels in japan should be more or less equivalent to stateside 93 octane.
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Old 01-29-2006, 03:57 AM   #4
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^^^^^^^^^^^^^^^^^^^^^^
yeah, they run 100 RON + over there.


powerlabs is correct
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Old 01-29-2006, 06:02 AM   #5
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you are correct on the loose power, however you are incorrect.


my JDM "280" hp engine does NOT make "280" hp.

it makes ~310 at the crank..... on 91 octane.

238 at the wheels stock untuned with poop gas on FLi's mustang dyno. charts are posted on this forum somwhere.

i wonder what it does on race gas.....
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Old 01-29-2006, 12:06 PM   #6
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Quote:
Originally Posted by swapstar
you are correct on the loose power, however you are incorrect.


my JDM "280" hp engine does NOT make "280" hp.

it makes ~310 at the crank..... on 91 octane.

238 at the wheels stock untuned with poop gas on FLi's mustang dyno. charts are posted on this forum somwhere.

i wonder what it does on race gas.....
Yeah, and my "280" hp JDM engine does a 12.9 1/4 mile on 93 octane and a 12.6s 1/4 mile on 96 octane with a passenger. Both on snow tires and full interior and gas tank... Either way, under rated HP or not, this post was to make the point that there is a difference, and its a pretty big one.

Oh, and Subbyspeed:

"I'm glad i did a usdm swap ";

You're forgetting that even after losing a ton of power to crap gas my JDM swap is still probably making 60HP over your USDM swap
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Old 01-29-2006, 12:27 PM   #7
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Quote:
Originally Posted by powerlabs
Oh, and Subbyspeed:

"I'm glad i did a usdm swap ";

You're forgetting that even after losing a ton of power to crap gas my JDM swap is still probably making 60HP over your USDM swap
your right, i just don't want to have to worry about running an engine on crappy gas it wasn't designed for, for a long time.
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Old 01-29-2006, 01:43 PM   #8
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funny you say an engine designed to run on 96 oct doesn't make the same power on 93...kinda like saying a stock WRX doesn't make the same power running on regular 88 octane...it's a given that you need to give up some power by means of boost or timing...
edit and about the STI swap over a USDM swap...how much does a WRX motor go for versus a VER5 STI RA swap...um, a lot less...
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Old 01-29-2006, 02:07 PM   #9
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Quote:
Originally Posted by Homemade WRX
funny you say an engine designed to run on 96 oct doesn't make the same power on 93...kinda like saying a stock WRX doesn't make the same power running on regular 88 octane...it's a given that you need to give up some power by means of boost or timing...
edit and about the STI swap over a USDM swap...how much does a WRX motor go for versus a VER5 STI RA swap...um, a lot less...
Actually, when I was pricing out my swap JDM motors cost LESS than USDM WRX motors... I understand that USDM motors have come down a bit, but even if the USDM WRX was marginally cheaper you'd still have to spend a lot of money on it to get JDM performance, so no matter how you look at it, the *only* reason to go USDM would be to pass emissions, in my opinion.
As far as the octane issue being "funny"; its been a debate here for a while. You might think it is obvious but look up a coupe posts; I just presented DATA specifiying how there IS knock and there IS power loss and "shikataganai" goes and tells me that the motor is designed for 93 octane . I myself *suspected* that there was power loss but I hadn't been able to quantify it untill now. Data>Hearsay every time.
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Old 01-29-2006, 02:40 PM   #10
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Yes , JDM ecu's have aggressive ignition timing . So its a no brainer that with lower octane available here that its going to suffer. But there is no reason why you can't tune what you have. I have ran my stock V3 ecu for about 6yrs now with no problems aside from premium gas prices.

Last edited by Ver.III; 01-29-2006 at 03:21 PM.
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Old 01-29-2006, 03:11 PM   #11
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Quote:
Originally Posted by Ver.III
Yes , JDM ecu's have aggressive ignition timing . So its a no brainer that will lower octane available here that its going to suffer. But there is no reason why you can't tune what you have. I have ran my stock V3 ecu for about 6yrs now with no problems aside from premium gas prices.
You can DETUNE a jdm engine to run on 93. But what fun is that.

This is gonna turn into another USDM(junk) VS JDM thead
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Old 01-29-2006, 04:02 PM   #12
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Default Here are my observations

I have a Ver.5 on RS and we have 91 octane gas in California.

here are some of my observation since I had the swap last year.
With 91 octane the motor doesn't really like to pull to 8000+ redline, especially after 6800rpm or so. The power level is definitely less.

I have tried mixing 100 octane race gas and difference is imminent. The engine revs much quicker, less lag, more power and response down below 3krpm. Power delivery is so smooth to the redline. The powerband in comparison to USDM STi is very different.
'
Now here is something i'm always careful on. As for me when the car gets use to higher octane it is very important to not to put straight 91 without resetting the ECU. I did it once and the thermostat started going up north as I started the car and touch throttle little bit. ECU re-adjusts after sometime and it gets use to 91.

I dynoed the car with maha dyno and i got 267hp at the crank with 91 octane. Car is stock and only mod would be catless downpipe and WRX midpipe (which i don't have anymore)I'm not quite sure how it would turn out on mustang dyno.

Gas is expensive and 100 octane costs 2x as much so...
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Old 01-29-2006, 04:43 PM   #13
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I pay $4.299 per gallon for 110 octane. It works out cheaper than an octane booster to put 2 gallons of that in a tankfull of 93 octane, and the octane boost is greater.
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Old 01-29-2006, 04:52 PM   #14
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Quote:
Originally Posted by powerlabs
Actually, when I was pricing out my swap JDM motors cost LESS than USDM WRX motors... I understand that USDM motors have come down a bit, but even if the USDM WRX was marginally cheaper you'd still have to spend a lot of money on it to get JDM performance, so no matter how you look at it, the *only* reason to go USDM would be to pass emissions, in my opinion.
As far as the octane issue being "funny"; its been a debate here for a while. You might think it is obvious but look up a coupe posts; I just presented DATA specifiying how there IS knock and there IS power loss and "shikataganai" goes and tells me that the motor is designed for 93 octane . I myself *suspected* that there was power loss but I hadn't been able to quantify it untill now. Data>Hearsay every time.
funny because when I was shopping 3 years ago I got my USDM with 11k miles and everything I need for $2k...at the same time a ver5 sti was about 4-4.5k and the ver 6 was about 5k...the ver 3 and older were about 2-3k...and about the data presented...good, finally some people will shut up...I thought you had been a doubter of power loss...

and don't get me wrong, I wish I had-had the money to buy an STI RA swap...but it was at least 2 times the cost at the time
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Old 01-29-2006, 06:53 PM   #15
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Quote:
Originally Posted by Homemade WRX
funny because when I was shopping 3 years ago I got my USDM with 11k miles and everything I need for $2k...at the same time a ver5 sti was about 4-4.5k and the ver 6 was about 5k...the ver 3 and older were about 2-3k...and about the data presented...good, finally some people will shut up...I thought you had been a doubter of power loss...

and don't get me wrong, I wish I had-had the money to buy an STI RA swap...but it was at least 2 times the cost at the time
Yes, I was a doubter too... See, I assumed that just because the car ran fine and I couldn't hear any knock that there wasn't any... Plus I am very much against any kind of "butt dyno" comparison, so I refuse to make any conclusions based on that... Well, nothing like a little bit of data to enlighten me
I paid $3000 shipped for my engine, ecu, front crossmember, fuel pump, turbo, downpipe, full wiring harness, rear brakes and intercooler... When I was looking for an engine the USDMs were around 3K as well...
Either way, as long as you've got a turbo under the hood or you want one you're cool in my book
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Old 01-29-2006, 06:55 PM   #16
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Quote:
Originally Posted by powerlabs
Yes, I was a doubter too... See, I assumed that just because the car ran fine and I couldn't hear any knock that there wasn't any... Plus I am very much against any kind of "butt dyno" comparison, so I refuse to make any conclusions based on that... Well, nothing like a little bit of data to enlighten me
I paid $3000 shipped for my engine, ecu, front crossmember, fuel pump, turbo, downpipe, full wiring harness, rear brakes and intercooler... When I was looking for an engine the USDMs were around 3K as well...
Either way, as long as you've got a turbo under the hood or you want one you're cool in my book
wow, you got a steal on your engine...oh and for not taking anything word of mouth without proof, I'm a senior ME student...so I know what you mean
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Old 01-29-2006, 07:26 PM   #17
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Quote:
Originally Posted by Homemade WRX
wow, you got a steal on your engine...oh and for not taking anything word of mouth without proof, I'm a senior ME student...so I know what you mean
Me too! (graduating Dec. 2006 from Michigan Tech). Yeah, I got a killer deal, but its not a JDM STI, and FLI didn't know it was a Type RA either when they sold it to me. Either way, with its high octane guzzling habits aside, I'm happy!
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Old 01-29-2006, 08:44 PM   #18
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hmm. thats a good price? anyone want a good price on a v4 sti-RA?.......its so pretty i almost want to put it in my car, pulled the valvecoverlast nite and almost freaked out bc the head was like new
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Old 01-29-2006, 09:11 PM   #19
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Originally Posted by swapstar
hmm. thats a good price? anyone want a good price on a v4 sti-RA?.......its so pretty i almost want to put it in my car, pulled the valvecoverlast nite and almost freaked out bc the head was like new
Absolutely... Show me any place that sells a complete engine shipped, with ECU, turbo, complete wiring harness, fuel pump, intercooler, and throw in some JDM vented rear brakes for less than that.
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Old 01-29-2006, 09:24 PM   #20
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Quote:
Originally Posted by Homemade WRX
funny because when I was shopping 3 years ago I got my USDM with 11k miles and everything I need for $2k...at the same time a ver5 sti was about 4-4.5k and the ver 6 was about 5k...the ver 3 and older were about 2-3k...and about the data presented...good, finally some people will shut up...I thought you had been a doubter of power loss...

and don't get me wrong, I wish I had-had the money to buy an STI RA swap...but it was at least 2 times the cost at the time
Thats funny the Ver 6 was selling for a grand more when its the exact same thing as a Ver 5. Buyer beware
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Old 01-29-2006, 09:52 PM   #21
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Quote:
Originally Posted by powerlabs
Me too! (graduating Dec. 2006 from Michigan Tech). Yeah, I got a killer deal, but its not a JDM STI, and FLI didn't know it was a Type RA either when they sold it to me. Either way, with its high octane guzzling habits aside, I'm happy!
Me too...with a minor in motorsports (aerospace)...I may just go ahead and take the fall light and stay for the spring for one more year of FSAE...that way I go into grad school on schedule too
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Old 01-29-2006, 09:53 PM   #22
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Quote:
Originally Posted by swapstar
hmm. thats a good price? anyone want a good price on a v4 sti-RA?.......its so pretty i almost want to put it in my car, pulled the valvecoverlast nite and almost freaked out bc the head was like new
yes please let me know...time to swap it into a wagon...or a coupe...not sure which
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Old 01-30-2006, 12:53 PM   #23
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Quote:
Originally Posted by Ver.III
Yes , JDM ecu's have aggressive ignition timing . So its a no brainer that with lower octane available here that its going to suffer. But there is no reason why you can't tune what you have. I have ran my stock V3 ecu for about 6yrs now with no problems aside from premium gas prices.
Isn't this the real root of the "power loss"? It's not so much the engine itself....but the ECU programming.

Quote:
Originally Posted by powerlabs
I pay $4.299 per gallon for 110 octane. It works out cheaper than an octane booster to put 2 gallons of that in a tankfull of 93 octane, and the octane boost is greater.
You gotta pay tax on race gas? In OH. we don't pay tax cuz' the fuel is not "legal for highway use".


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Old 01-30-2006, 01:08 PM   #24
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ok, i started my jdm sti on 110 and it deffenetly made a difference in power as well as no knocking, but the only way of course to get it is in a can. but, 110 is so much hevier than 93octane, wouldnt it just sink to the bottem of the tank if you mixed it???
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Old 01-30-2006, 02:06 PM   #25
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I am glad to finally see some empirical evidence to back this up. I have been telling people this for years and generally been blown off. Mike Shields at SPD also has spoken about this, and generally he is dead on with his tech.

As Storm said, it's not a difference in the engine that makes this, it is the tuning. This is why the Ej205 is rated at 250hp in Japan while it is 227 here. This is why Cobb can get so much power out of their reflashes. The ECU's come to us really conservatively tuned in USDM trim.

As for the whole pricing debate, I have long asserted that teh best deal going is the '97-98 plain jane WRX swaps. Those longblocks are very similar to their STI counterparts for far less than the STI premium pricetag. I would jump on a v3 or v4 non-Sti swap in a minute over a USDM swap. I can easily get 100 octane gas here in Colorado...
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