Auto 3.5 Swap Dyno
10-16-2009, 06:03 PM
#1
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Auto 3.5 Swap Dyno
We got the car dynoed last friday and today I finally made it back down to the shop to pickup the runfiles. The results were 210whp and 213tq. The mods are NWP blockoff plate, ebay headers and y-pipe, and PFTB. We are running a short ram intake which is just a coupler to the MAF and a Filter. One known issue is that there is an exhaust leak at the headers since we forgot to put the gaskets back in lol. But we are happy with the numbers especially since it still has the stock cat and catback on the car. Im guessing the large drop in power is because of the exhaust leak but Im not sure. SAE numbers were 203hp 206tq. Here is the graph.
Last edited by ajcool2; 10-16-2009 at 06:05 PM.
10-17-2009, 08:54 AM
#7
My 3.5 did something like that on the first NA dyno, using the 3.0 timing, stock ECU and stock MAF. The MAF sees more air flow at any RPM because of the larger engine, so more fuel is sprayed thru the injectors. That's why I fixed it with a piece of tape across the back of the sensor tunnel in the MAF. It blocked just a little of what the MAF sees and leans up the engine.
Worked for me....
10-17-2009, 09:01 AM
#8
ISP has seen a lotta maximas, man i need a 3.5 swap, help me....do you have a fuel converter to lean it out a bit?, at 4k that thing dumping a lotta gas, but seem like it leaned out higher in the revs. if im not mistaken shouldnt it be the other way around, leaner down low, and richer as the rpms get higher?
Last edited by JAMAICANLOVRBOY; 10-17-2009 at 09:07 AM.
10-17-2009, 12:25 PM
#9
My 3.5 did something like that on the first NA dyno, using the 3.0 timing, stock ECU and stock MAF. The MAF sees more air flow at any RPM because of the larger engine, so more fuel is sprayed thru the injectors. That's why I fixed it with a piece of tape across the back of the sensor tunnel in the MAF. It blocked just a little of what the MAF sees and leans up the engine.
Last edited by nismology; 10-17-2009 at 12:43 PM.
10-17-2009, 07:17 PM
#11
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Tune-by-Tape.
My 3.5 did something like that on the first NA dyno, using the 3.0 timing, stock ECU and stock MAF. The MAF sees more air flow at any RPM because of the larger engine, so more fuel is sprayed thru the injectors. That's why I fixed it with a piece of tape across the back of the sensor tunnel in the MAF. It blocked just a little of what the MAF sees and leans up the engine.
Worked for me....
My 3.5 did something like that on the first NA dyno, using the 3.0 timing, stock ECU and stock MAF. The MAF sees more air flow at any RPM because of the larger engine, so more fuel is sprayed thru the injectors. That's why I fixed it with a piece of tape across the back of the sensor tunnel in the MAF. It blocked just a little of what the MAF sees and leans up the engine.
Worked for me....
10-17-2009, 07:38 PM
#12
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ISP has seen a lotta maximas, man i need a 3.5 swap, help me....do you have a fuel converter to lean it out a bit?, at 4k that thing dumping a lotta gas, but seem like it leaned out higher in the revs. if im not mistaken shouldnt it be the other way around, leaner down low, and richer as the rpms get higher?
10-17-2009, 07:39 PM
#13
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Well it's been proven that the 3.5 doesn't swallow THAT much more air than a 3.0 (especially without VTC) throughout much of the rev-range; certainly not enough to account for such a rich a/f even at lower RPM's. Most of the HP/torque increase comes from the geometry. The richness is likely due simply to larger injectors and a higher-than-stock base fuel pressure that most swappers run. If the stock injectors (somehow) and FPR were run I'd reckon the a/f wouldn't change all that much.
10-18-2009, 09:42 AM
#16
Well it's been proven that the 3.5 doesn't swallow THAT much more air than a 3.0 (especially without VTC) throughout much of the rev-range; certainly not enough to account for such a rich a/f even at lower RPM's. Most of the HP/torque increase comes from the geometry. The richness is likely due simply to larger injectors and a higher-than-stock base fuel pressure that most swappers run. If the stock injectors (somehow) and FPR were run I'd reckon the a/f wouldn't change all that much.
The 10:1 A/F at WOT made tuning with nitrous harder, because the NX jets were app. 12:1 A/F and as you change the jets, the WOT A/F would still vary. When I got the NA A/F set to 12:1, then changing the NX jet pairs for different HP did not change the A/F. Tune-by-Tape worked for me...
Last edited by grey99max; 10-18-2009 at 09:50 AM.
10-18-2009, 11:57 PM
#18
My injectors and fuel pressure were stock - still are......... my A/F at WOT when NA was about 10:1. Just going by displacement, when WOT, the 3.5 pulls 16.6% more air into every cylinder at any RPM. That's approximately 583cc/cylinder for the 3.5 compared to 500cc/cylinder for the 3.0. The MAF sees the extra air flow at all RPMS. I suspect that the stock ECU map is happier with the 3.0 injectors, the injector pulse-width map is set for those injectors, and the larger 3.5 injectors may be the real problem. Still, the bit of tape worked by slightly reducing the measured air flow through the MAF sensor tunnel.
And there's quite a bit more to how much air an engine will swallow at a given RPM than its displacement. 
14.6% larger displacement doesn't necessarily = 14.6% increase in mass airflow at every RPM. Intake/exhaust port flow, intake manifold design, cam specs/timing et al. all have some affect on volumetric efficiency throughout the powerband.http://img.photobucket.com/albums/v2...sRPM060518.jpg
Keep in mind that's comparing a VQ35 with operating VTC vs. a USIM-equipped 3.0.
10-19-2009, 12:01 AM
#19
You will have to pull some fuel, but not necessarily as much as the OP does. We don't know what his base fuel pressure is set to.
10-19-2009, 12:04 AM
#20
Regardless of the ultra-lean a/f's some like to run here, the best range for consistent power is 12.7-13.2. Real n/a power is made through timing, not running lean. The best case scenario is using the fueling to keep things relatively cool and advancing the heck out of the timing. This assumes you have seperate a/f and timing control however..
Last edited by nismology; 10-19-2009 at 12:09 AM.
10-19-2009, 12:11 AM
#21
10-19-2009, 06:28 AM
#22
You ran A32 259cc injectors with your 3.5 swap? And there's quite a bit more to how much air an engine will swallow at a given RPM than its displacement. 14.6% larger displacement doesn't necessarily = 14.6% increase in mass airflow at every RPM. Intake/exhaust port flow, intake manifold design, cam specs/timing et al. all have some affect on volumetric efficiency throughout the powerband.
And there's quite a bit more to how much air an engine will swallow at a given RPM than its displacement. 14.6% larger displacement doesn't necessarily = 14.6% increase in mass airflow at every RPM. Intake/exhaust port flow, intake manifold design, cam specs/timing et al. all have some affect on volumetric efficiency throughout the powerband.
And yes, my engine installation was optimized for airflow - long-tube headers, 3" collector to the tailpipe, SSIM intake and a real cold-air intake under the lip of the hood, eBay S1 cams. It responds very well to spray. On my PLX logs, the A/F was consistently around 10:1 at WOT up to fuel cut. With the tape mod, once I set it, A/F was consistently 12:1. Works for me...
10-21-2009, 10:43 AM
#24
yo Mike, so since I have an SAFC2, what fuel pressure do you recommend so I can take advantage of the safc timing pull while leaning out the system side effect? i belive the pressure is at 36 psi right now.
Any Idea how many degrees it pulls out at say 10%, vs 5% etc?
Any Idea how many degrees it pulls out at say 10%, vs 5% etc?
10-21-2009, 11:39 AM
#26
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Here your go. http://forums.maxima.org/all-motor/3...g-advance.html
10-21-2009, 12:19 PM
#27
You wont be able to retard much timing to be honest. Although timing is affected by the MAF corrections, it is not as drastic as you think, it took me near 60psi of fuel pressure or more, to get 10degree advance on my NA 3.0. To pull timing, I dont think it will work, considering you will have to go so low in fuel pressure it will give you issues. email me.
05-20-2010, 11:09 AM
#39
LEAN. Remember?