It's official - N/A 3L cracks 12's
10-03-2007, 12:04 PM
#81
3.5 in the works
Thread Starter
iTrader: (7)
Join Date: Jun 2004
Location: Ontario, Canada
Posts: 2,477
Although I laugh when I see this it's not true of course, at least not for me. Here in Southern Ontario the air/climate is no better than half of the northern States, we're actually further south...
I was never worried about piston speeds. I knew the VQ30 would be fine with respect to that. The oil pump and valve train were the 2 areas to address for high revs, and so I've done that. But note that I didn't rev to 8200 for those races, I was having problems up top with the tune, most of the time I couldn't get past 7000 or so. I did hit 8k a couple times but certainly was way too lean (= knock and power loss). And no I didn't tune it that way, it was unexpected - the ECU changed something from one day to the next... 
I have a couple things planned yet for the 3.0. It should go quicker and faster than it did on Sat yet for sure, for starters just by getting the tune right and driving better. 
Edited. hehe. I'll get on a dyno eventually and then we'll have some numbers/curves to look at.
Ridiculous timeslip. 8200 on stock rods!? I'm beginning to think VQ30DE and VQ30DET rods are the same or very close!
I just pulled out a stock VQ30 crankshaft yesterday and the thing looks INDESTRUCTIBLE. It must weight 25 pounds. We kept the crank, rods and retainers from a junker 3.0.
The 3.5 is NOT the way to go. The reason is piston speeds;
http://www.csgnetwork.com/pistonspeedcalc.html
At 7500 RPM the 3.5 reaches the critical speed of 4000 feet per minute. This is pretty much the limit on stock 35 rods. Piston speeds is what dictates how much stress the bottom end is put through.
What makes the VQ30 such an incredible motor is the extremely oversquare design. It has a super small 73.3 mm stroke VS 81.4 mm for the 3.5. What this means is that at 7500 the VQ30 is only doing 3600 feet per minute, so it strains as much at 7500 as the VQ35 at 6750.
In order to reach 4000 feet per minute, the 73.3 mm crank has to reach a mind boggling 8325 RPMs! That's why Dandy can get away with 8200 on stock rods. And to think Nissan imposes a 6550 rev limiter on that bottom end.
The best NA setup for a maxima is not the 3.5, it is the 3.2! Buy a junkyard VQ35 for 600, a junkyard VQ30 for 300, VQ35HR pistons for 300, ARP rod bolts, cams and valve springs and you have an 8000 RPM monster that still displaces only 3160 cc or so. But it would have the better VQ35 heads and the lighter VQ35HR pistons. Plus oil squirters and the fact that the 3.5 is 35 pounds lighter.
I'm beginning to think VQ30DE and VQ30DET rods are the same or very close! I just pulled out a stock VQ30 crankshaft yesterday and the thing looks INDESTRUCTIBLE. It must weight 25 pounds. We kept the crank, rods and retainers from a junker 3.0.
The 3.5 is NOT the way to go. The reason is piston speeds;
http://www.csgnetwork.com/pistonspeedcalc.html
At 7500 RPM the 3.5 reaches the critical speed of 4000 feet per minute. This is pretty much the limit on stock 35 rods. Piston speeds is what dictates how much stress the bottom end is put through.
What makes the VQ30 such an incredible motor is the extremely oversquare design. It has a super small 73.3 mm stroke VS 81.4 mm for the 3.5. What this means is that at 7500 the VQ30 is only doing 3600 feet per minute, so it strains as much at 7500 as the VQ35 at 6750.
In order to reach 4000 feet per minute, the 73.3 mm crank has to reach a mind boggling 8325 RPMs! That's why Dandy can get away with 8200 on stock rods. And to think Nissan imposes a 6550 rev limiter on that bottom end.
The best NA setup for a maxima is not the 3.5, it is the 3.2! Buy a junkyard VQ35 for 600, a junkyard VQ30 for 300, VQ35HR pistons for 300, ARP rod bolts, cams and valve springs and you have an 8000 RPM monster that still displaces only 3160 cc or so. But it would have the better VQ35 heads and the lighter VQ35HR pistons. Plus oil squirters and the fact that the 3.5 is 35 pounds lighter.
Edited. hehe. I'll get on a dyno eventually and then we'll have some numbers/curves to look at.
Last edited by DandyMax; 10-03-2007 at 12:08 PM.
10-03-2007, 04:21 PM
#83
Debateable. Piston speeds alone is not a valid or complete basis to make this assumption. The VQ35 has a considerably shorter stroke than the S54, F20C, K20, etc. 81.4mm isn't much when you compare it to MANY other motors.
Let's just enjoy this accomplishment and not turn this into a VQ vs. VQ contest.
Let's just enjoy this accomplishment and not turn this into a VQ vs. VQ contest.
Last edited by nismology; 10-04-2007 at 12:47 AM.
10-09-2007, 10:08 AM
#86
3.5 in the works
Thread Starter
iTrader: (7)
Join Date: Jun 2004
Location: Ontario, Canada
Posts: 2,477
Well I fixed my lean out problem, next time at the track I should be able to actually get up to 8k. Still have to tune it up there, timing especially, but now it's safely rich at least.
10-09-2007, 10:53 AM
#88
3.5 in the works
Thread Starter
iTrader: (7)
Join Date: Jun 2004
Location: Ontario, Canada
Posts: 2,477
I believe it was 2 things: my stock ECU had been running in a kind of safe mode for days and was WAY rich (like low 10's, some 9's) but then suddenly decided to switch back to normal on the track day, so all of a sudden my AFR's changed from the tuning runs I had done the night before, and that was compounded by the fact my fuel pump started losing pressure going down to around 20+ psi. (It used to be able to hold 46psi up at 7500 rpm but no more). I've had a Walbro kicking around for over a year though so I just installed that. Pressure holds fine now, although I still need to readjust the EU fuel and timing maps to compensate for the ECU change.
I'm hoping to get back to the track at least once more this season (though it's almost over). When exactly I'm not sure yet, have to check the calendar/weather, play it by ear etc.
I'm hoping to get back to the track at least once more this season (though it's almost over). When exactly I'm not sure yet, have to check the calendar/weather, play it by ear etc.
10-09-2007, 03:30 PM
#90
I believe it was 2 things: my stock ECU had been running in a kind of safe mode for days and was WAY rich (like low 10's, some 9's) but then suddenly decided to switch back to normal on the track day, so all of a sudden my AFR's changed from the tuning runs I had done the night before, and that was compounded by the fact my fuel pump started losing pressure going down to around 20+ psi. (It used to be able to hold 46psi up at 7500 rpm but no more). I've had a Walbro kicking around for over a year though so I just installed that. Pressure holds fine now, although I still need to readjust the EU fuel and timing maps to compensate for the ECU change.
I'm hoping to get back to the track at least once more this season (though it's almost over). When exactly I'm not sure yet, have to check the calendar/weather, play it by ear etc.
I'm hoping to get back to the track at least once more this season (though it's almost over). When exactly I'm not sure yet, have to check the calendar/weather, play it by ear etc.
10-09-2007, 04:04 PM
#91
3.5 in the works
Thread Starter
iTrader: (7)
Join Date: Jun 2004
Location: Ontario, Canada
Posts: 2,477
I'm not 100% sure what caused this, the ECU was unplugged for a year, so it obviously reset but I'm thinking maybe it had something to do with OBD2 protocol, needs to have readiness tests go OK, or certain #/type of driving patterns fulfilled etc before it goes into normal operating mode etc. I should research OBD standards more I suppose.
The idle control also seemed awful in the "safe" mode, but has since cleared up and functioning almost normally now (of course I've still had to adjust some things to counteract the overlap on the cams though).
The funny thing is it just switched on the morning of the track day, I had tuned up everything based on the safe/rich mode as I wasn't sure it was going to adjust back properly, but then it went and adjusted all of a sudden on the track day itself, as I said, which then threw my tune off. Who knows, if it was some OBD thing, maybe it just happened to fulfill what it needed to by the time I got to the track. So during the track day I tried to adjust fueling with the EU, but got hampered by the fuel pump dropping pressure then..
Thread
Thread Starter
Forum
Replies
Last Post
James92SE
3rd Generation Maxima (1989-1994)
142
01-02-2024 09:23 AM
Andy29
5th Generation Maxima (2000-2003)
8
09-29-2015 05:32 AM