the other day filled up on 89 octain rather than 87, I got way better gas millage with this gas compared to normal. I've got a D15B vtec engine from japan and i'm wondering if it is in fact completely different than its D16Z6 counterpart. Any one know if the engine should actually be running on super or atleast mid grade? cdm owners manual calls for only 87 oct and 16 degrees of advance on the ignition timing, but this is for the z6. Are these #'s actually incorect for this motor?
thanks in advance.

 

??

 

no not really, I don't see the point of putting higher then 87. The only reason I would put higher would be if the engine is knocking or Honda says so.

Dave

 

Anyone else? I have heard that this engine has slightly higher compression than the z6 but havent found any specs to back it up.

 

98.9% the same motor.

 

seeing as they sell higher octane fuel in japan than the states, my guess is they dont even have 87 octane in japan. the computer can retard the timing to compensate for quicker burning gas. if you got better mileage on 89 stick with that, i think 89 is regular gas in japan anyway.

edit: as for the timing, my guess is if it was different it wouldn't be different by more than a degree or 2 advanced or retarded which will make barely any difference.

 

I currently have the same motor in my 94 Si. I use 93 octane and a socketed ecu with a stock jdm d15b bin file burned on the chip. The car runs really well and my tuner bf is happy with it. By next year, I'm hoping to be back with my original engine rebuilt and using 87 octane again. lol

The Japanese use higher octane gas.

 

all of you are wrong, well, most of you. japans has 90octane fuel which is there low grade. the z6 and D15b are nothing alike besides the head, rods, and HP numbers. compression is 9.3:1 which is fine on 87 octane. the computer doesnt compensate for quick burning fuel. if there where a knock sensor the ECU might read knock and retard the timing a bit, but there isnt a knock sensor used in the 92-95vti D15b. EVERYONE NEEDS TO REALIZE THAT JDM ISNT SOME CRAZY OFF THE WALL CRAP. ITS THE SAME THINGS WE GET W/OUT THE EMISSIONS SYSTEMS. the higher HP ratings are still yet to be confirmed, and never will be cuz all the motors tested arent new, so theres no constant. just use whatever gas you want.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schardbody &raquo;</TD></TR><TR><TD CLASS="quote">all of you are wrong, well, most of you. japans has 90octane fuel which is there low grade. the z6 and D15b are nothing alike besides the head, rods, and HP numbers.</TD></TR></TABLE>
what else is left? the manifold is the same, valve cover, TB, sensors, can run on a p28 which is usdm. there are many things that the z6 and the d15b share.

 

well, lets see, pistons, block, cam, crank. the list goes on, the only reason the P28 can be used is because the motor flows the same as the z6, but the p08 is the better choice of ECU's. they are very similar, but not 98%. anyhow, any grade of gasoline will work fine as long as the proper ecu is used and everything else is in good working order.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schardbody &raquo;</TD></TR><TR><TD CLASS="quote">well, lets see, pistons, block, cam, crank. the list goes on, the only reason the P28 can be used is because the motor flows the same as the z6, but the p08 is the better choice of ECU's. they are very similar, but not 98%. anyhow, any grade of gasoline will work fine as long as the proper ecu is used and everything else is in good working order.</TD></TR></TABLE>
do you not relize we you are contridicting yourself? you said that they are the same in all these ways, and even list things. but then say that they are not the same..

 

NO, the head casting, rods, and dyno numbers are the same, thats where the list ends. the other list is the differances. people say they are identical because they use the same head casting, and similar performance wise. they are nothing alike in terms of internals. r/s ratio, deck height, pistons, camshaft, crankshaft, or anything else.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EH339 &raquo;</TD></TR><TR><TD CLASS="quote">I currently have the same motor in my 94 Si. I use 93 octane and a socketed ecu with a stock jdm d15b bin file burned on the chip. The car runs really well and my tuner bf is happy with it. By next year, I'm hoping to be back with my original engine rebuilt and using 87 octane again. lol

The Japanese use higher octane gas.</TD></TR></TABLE>

One of my JDM homeboyz corrected this issue for me, answer is yes.. D15B should be ran on high octane than the USDM Z6 because yes, in japan 93 octane is about as common as our unleaded.. 118 octane leaded fuel, in japan is what they use on built motors an highly tuned cars.. So ever since I found out those facts "with quite coherent searching" i've stuck to 93 ever since.. 2yrs later, still runnin hard.... ;-)

 

point is theres no need to use anything other than 87-89octane. if you can think of a reason why i would like to know it. if the head is the same as the z6, and compression is only .1:1 more, why is 93octane needed???? ITS NOT.

and the timing maps in the p08 are a little more aggressive than a p28, thus the reason people think it needs high octane, but if its not spark knocking due to the low octane, you are wasting money and losing power using higher octane.

 

thanks for all your answers guys