SteVTEC

The J30A4 uses a 10.0:1 compression ratio vs the previous engine at 9.4:1. The engine is fully equipped with a knock sensor and feedback timing control to take advantage of higher octane fuel. It was de-rated to 240/212 on 87 octane likely for marketing purposes, since people buying Accords typically wouldn't want to be "required" to pay for higher octane fuel. A Honda engineer interviewed by USA Today during the late-02 unveiling said that the engine would pickup another 10hp and 10+ tq on higher octane fuel (since it would allow more timing advance before detonation.)

You should sign in at www.v6performance.net (where all the Accord V6 guys are these days)

Nobody has done a direct dyno comparison of 87 vs 91-93 with the car, but people have been able to get 0.2-0.3s better ETs at the track along with a 1-2 mph improvement in traps by switching up to higher octane under similar track conditions and weather/launch, etc.

SteVTEC

That's the 98-02 J30A1 engine which is a completely different beast. Yes, that engine will lose power on higher octane (proven by a dyno analysis in Car & Driver, Nov 01), but the J30A4 in the 03+ is the opposite.

Covered in the 6th Generation Accord V6 FAQ.

VQuick

iTrader: (17)

Thanks for the info, SteVTEC. Not to turn this into an Accord thread , but would it be safe to assume noticeably better gas mileage with the J30A4 on premium fuel? Improved to the point where it's as cheap or cheaper to fill up with premium as with regular?

SteVTEC

dunno. maybe

It probably depends on your driving style and the type of driving that you do, and the same goes for the Maxima. If you cruise easy and do lots of highway you might actually get better mileage on 87. But if you do a lot of cut-n-thrust urban driving, or have a more aggressive driving style then 91 might give you better mileage.

If you're curious, go search at V6P.net in the 7th generation AV6 forum for "mileage" and you'll probably find some good threads to read up on.

Eric425

Where did I say performance won't drop? I never said that performance won't drop. I'm saying that you have no proof that it will drop by 20 hp. And you don't. The dyno you produced has nothing to do with anything. Just because 2 different cars, which would naturally have discrepencies anyways, and have a higher compression ratio/need for higher octane, showed a hp difference doesn't mean the maxima running reg and premium will show the same amount of difference. Prove that a MAXIMA will drop by that much. The VR6 in the dyno have a higher compression ratio than the 10:1 in the max, and it's more crucial to use a higher octane fuel. My post count isn't as high as your because I don't usually like to shoot my mouth off when I don't know WTF I'm talking about. You've accuse me of saying things that I didn't, you post a unrelated dyno as proof, and then call names. Real mature.

BlueC

iTrader: (5)

Calm down junior, the whole reason why you got owned was you didnt read up on the FAQs, which is a typical problem with newbies these days. Yea the dyno isnt the same, but ive read many times before, when the timing is retarded on the maxima specifically, you can lose nearly 20hp. I dont have time to search cause search is semi-broken, but FAQs provide plenty info on this subject. So instead of asking Qs and being all tough, read the FAQs, it'll make everyones life easier.

You're done.

ohannon7

iTrader: (5)

Plus I think you get better gas mileage w/ premium gas, or did someone already say that???

SteVTEC

VeeTec just dynoed his stock 4g and had some fuel issues.

http://forums.maxima.org/showthread.php?t=282593

Looks like about 6hp and 10tq (at the crank) by dropping to 87 octane. He had "premium" in it, but apparently it might not have been premium after all.


BTW, the VR6 in those particular cars have the same 10.0:1 CR as the VQ30 does, but there's more to knock sensitivity than just compression ratio. Combustion chamber design and shape have a say, as does the ignition timing the car "wants" to run along with the cooling system. The VQ happens to have a top-notch cooling system which helps to reduce knock sensitivity. The VR6 is an extremely compact engine design and I wouldn't be surprised if it was more knock sensitive due to cooling issues than a VQ is. The VR6 has nearly as much motor but in a much smaller area, so that would make keeping it cool more of a challenge. So you may see a bigger difference on some engines than others. The dynospotracing.com chart was just used as an example of what happens to an engine when you put lower than the required octane level in it, though.

BTW, our Highlander's 1MZ-FE 3.0 has a 10.5:1 CR and it definitely has a good 10-15 lb-ft more torque on premium fuel (butt dyno) and also gets slightly better mileage on premium as well. We run nothing but premium in it.

Eric425

Hey, looks like we finally got some actual numbers from a maxima by VeeTec. And look, the 20 hp figure you pulled from your @ss is way, way off. More than 3 times the actual number. I guess you're owned now? I've read the faq, it's you who needs to read it right. I've read that section, but because it's a different graph of different cars, I could tell the subject at hand is going to be different. You just misinterpret and overexaggerate the information info you get. It's obvious to anybody who's run less than 91 that the difference is not 20 hp. Yeah, I don't pretend to know all about the cars. Just reading the posts, I can tell that Stevtec's got twenty times the knowledge I have on the subject. He's right, it'd make sense for factors like cylinder design to have an effect. Heat causes detonation, and compression of gas's causes heat, but so would the design of combustion chamber have on retaining that heat. Thin heats up more quickly, and to a hotter temp. Like a needle tip would heat up red in a candle flame, but a big iron skillet won't. But I can still smell the BS from a dumba$s's bench dyno. I believe that you've read that you'll lose 20 hp. But do you believe everything you read? It's a open forum, anybody can write anything they want, and not everybody always bothers to correct the morons who write a little too optimistically. You might have been on the board for longer, but if you don't know how to filter out the guesstimated, biased crap from the good stuff, then even with years on the boards, you're not going to understand much more than a 1st time poster. Now shut it , NOOB.

Dave Holmes

Back to the reply about Nissan saying our Maxima's hold 8.625 quarts of oil (with filter). Guess I'm 4.375 quarts low.

I run premium in my Maxima. One concern with this is something I'd read on Bobistheoilguy.com concerning premium fuels. Seems there's a theory about "premium" fuels having more additives (detergents), which makes sense. In this theory, using the same premium gas (read same higher doses of detergents) can cause deposits in the engine (much like always running injector cleaner). A recommendation on that site is to periodically switch manufacturers of premium gas to get different additive packages, instead of "OD'ing" on one additive package. Does this make sense?

Dave

Spaniard

iTrader: (1)

That is very interesting... I could see doing that as a precaution but I would be suprised and a bit disappointed if the very additives that were supposed to clean engine deposits turned out to be causing a different batch of them. That would be some poorly designed / tested shiite IMO.

BlueC

iTrader: (5)

Haha, wow, looks like this is the focused subject of the day for you. Guess what, I got back from having fun evening OUTSIDE of my house, what did you do? Sit at home and find a way to make yourself tough and try to make me look bad? Sound like fun. Have fun with your little argument there. Cause I could care less. Moron.

Dave Holmes

Using too much fuel injector cleaner causes deposits on plugs (and I would assume on other engine components), so I could see why using the same gas additive package repeatedly would cause the same. Just something to think about.

Back to using premium vs regular.... Are our ECU's programmed for maximum timing advance on 91? There has to be a limit to how far it can be advanced. After that, using higher octane may hurt performance because higher octane fuel contains less energy than lower grades (higher octane doesn't "make" more power, only allows for more timing advance which makes the power). So I guess the optimum grade would be where the ECU has the timing advanced to its maximum (and without detecting knock). More octane than that would be counter-productive.

Dave

SteVTEC

91 should be enough under most conditions. However, in heat soaked 90*F/extremely humid conditions this past summer, I did get some knocking and resulting timing retard even with 93 octane fuel. On moderately hard acceleration and about 23 degrees of timing (as indicated on my OBD-II scanner), at about 3400 rpm (peak torque) the timing would suddenly jump down to 18 degrees and then recover back up to the low-20 range. After my knock sensor blew, I bypassed it with the resistor temporarily which takes the KS out of play and now the ECU is running all the timing it wants regardless of if there's knocking or not. Under the same conditions and acceleration, now I noticed some mild knocking at 3400 rpm and the timing still stayed in the low-20 degree range. What happened was that the KS was working before, sensing the knock, and retarding the timing by 5 degrees. With the KS out of the loop, it just ran full timing and knocked a little, so I still had to be careful. And again that was on 93 octane fuel, but heat soaked conditions. With the Intake Air temp reading 15 degrees lower in the morning, no knocking occured.

Fortunately the 99's with auto climate control have an outside temperature display feature, and I put it to good use. Whenever the temp hit above 90F it would knock a little. 1 degree less and it was okay. It was very repeatable.