VQ35 and boost
02-10-2005, 07:40 AM
#1
VQ35 and boost
I read a while back in my350z.com about problems people were having with boosted VQ35's resulting in thrown rods. The theory at the time was that detonation was to blame, along with maybe a weak rod design.
Anybody have any more up-to-date information?
Anybody have any more up-to-date information?
02-10-2005, 08:47 AM
#4
Two issues:
1)They lightened the whole assembly and the rods can only handle 450-500whp with EXTREMELY careful tuning/timing. People have bent rods much lower with just okay tuning.
2)Timing. The VQ35s use heavily advanced timing, so if not retarded aggressively, you can get some detonation that will easily bend rods.
There is a THIRD suspect, which is the crank position sensor wire supposedly picking up interference on the way to the ECU and causing a catostrophic failue due to wrong firing time. Anyways, they are selling a shielded cable or something to combat this and rumor had a TSB coming out, but nothing so far.
Anyways, you'll be fine up to 400-450whp with a hell lot more torque StephenMax, so do it~!
1)They lightened the whole assembly and the rods can only handle 450-500whp with EXTREMELY careful tuning/timing. People have bent rods much lower with just okay tuning.
2)Timing. The VQ35s use heavily advanced timing, so if not retarded aggressively, you can get some detonation that will easily bend rods.
There is a THIRD suspect, which is the crank position sensor wire supposedly picking up interference on the way to the ECU and causing a catostrophic failue due to wrong firing time. Anyways, they are selling a shielded cable or something to combat this and rumor had a TSB coming out, but nothing so far.
Anyways, you'll be fine up to 400-450whp with a hell lot more torque StephenMax, so do it~!
02-10-2005, 09:12 AM
#6
Thanks for the good info, Icey.
The reason I ask is that I may be able to get a VQ35 crank and rods pretty cheaply, which would allow me to do the VQ33 stroker mod. I will have to get aftermarket pistons to drop the CR back down, though, and I'm wondering what CR to settle on. I don't intend to boost any higher than what my 2.87" pulley will produce. I would prefer not any lower than 9.5:1, if the rods can handle it. Sounds like they will, since I am aiming for 400 whp.
I know people are going to say just drop in a VQ35, but I am not ready to do that yet.
The reason I ask is that I may be able to get a VQ35 crank and rods pretty cheaply, which would allow me to do the VQ33 stroker mod. I will have to get aftermarket pistons to drop the CR back down, though, and I'm wondering what CR to settle on. I don't intend to boost any higher than what my 2.87" pulley will produce. I would prefer not any lower than 9.5:1, if the rods can handle it. Sounds like they will, since I am aiming for 400 whp.
I know people are going to say just drop in a VQ35, but I am not ready to do that yet.
02-10-2005, 09:31 AM
#8
I would keep the compression and use antidetonation measures like SwainTech coating, alchohol/water injection, INTERCOOLER, and if necessary drop the dynamic compression with some bigger overlap cams.
If you used the DET pistons, you'd probably end up with around the same 10.3:1 compression as a stock VQ35, guessing though.
If you used the DET pistons, you'd probably end up with around the same 10.3:1 compression as a stock VQ35, guessing though.
02-10-2005, 09:39 AM
#9
I've read some claims that point to the block design, being an open deck. Some people claim that under high power the open deck design allows the cylinders to kind of shift causing the major damage which why those companies have created the sleaving kits or whatever.
That was my take on everything...
That was my take on everything...
02-10-2005, 09:42 AM
#10
I've read that too, however that is truely false...guys are running 700whp on the block without issues and the damage occuring on stock blocks is detonation or preignition related. The sleeves are for the nutzos wanting 1000+whp.
02-10-2005, 10:52 AM
#13
Can't you get 400 whp with the 3.0 Stephen??? Arn't you like at 350 whp or something??? Maybe ported heads and a 3 angle valve job??? You could also take out on of the layers on the head gasket to increase the compression ratio a little.
Or you could go 3.5 with ported 3.0 heads and timing chain cover, and the 3.5 cams. I think you would reach 400 whp real quick with the blower. Also you could switch out the rod bolts with the 2005 track model rod bolts that are suppossed to be stronger. they are only like $2.50 each instead of like $150 set of ARP ones. With an intercooler and water/methanol and probally lower boost you might be fine with the higher compression.
Or you could go 3.5 with ported 3.0 heads and timing chain cover, and the 3.5 cams. I think you would reach 400 whp real quick with the blower. Also you could switch out the rod bolts with the 2005 track model rod bolts that are suppossed to be stronger. they are only like $2.50 each instead of like $150 set of ARP ones. With an intercooler and water/methanol and probally lower boost you might be fine with the higher compression.
02-10-2005, 11:22 AM
#14
Yes, he can hit 400whp with the VQ30, however he won't have the TORQUE of the VQ35s unless he uses a small N20 shot.
I'd see how far I could push the VQ30 for reasonable costs and then drop $400 or so for a NX kit.
I'd see how far I could push the VQ30 for reasonable costs and then drop $400 or so for a NX kit.
02-10-2005, 11:29 AM
#15
Originally Posted by spanishrice
Can't you get 400 whp with the 3.0 Stephen??? Arn't you like at 350 whp or something??? Maybe ported heads and a 3 angle valve job??? You could also take out on of the layers on the head gasket to increase the compression ratio a little.
I've got some spare 3.0 heads I'm playing with. They are very good right from the factory, with 3 angle valve jobs and valves that are about as big as you can get in there.
I think I could get to 400 hp with the VQ35 cams I have ready for install and a better flowing exhaust, maybe an electric cutout.
02-10-2005, 11:30 AM
#16
Originally Posted by IceY2K1
Yes, he can hit 400whp with the VQ30, however he won't have the TORQUE of the VQ35s unless he uses a small N20 shot.
I'd see how far I could push the VQ30 for reasonable costs and then drop $400 or so for a NX kit.
I'd see how far I could push the VQ30 for reasonable costs and then drop $400 or so for a NX kit.
02-10-2005, 11:43 AM
#19
Originally Posted by IceY2K1
Yes, he can hit 400whp with the VQ30, however he won't have the TORQUE of the VQ35s unless he uses a small N20 shot.
I'd see how far I could push the VQ30 for reasonable costs and then drop $400 or so for a NX kit.
I'd see how far I could push the VQ30 for reasonable costs and then drop $400 or so for a NX kit.
Or change his hairdryer
02-10-2005, 11:44 AM
#20
Originally Posted by Stephen Max
I've got some spare 3.0 heads I'm playing with. They are very good right from the factory, with 3 angle valve jobs and valves that are about as big as you can get in there.
02-10-2005, 11:53 AM
#21
Baah...show me where 13whp/psi non-intercooled is inefficient or the VE isn't adequate.
Yes, VQ35 heads are superior and AMAZING(105% VE on 350Z even), however with Mardi, Hal, etc. pushing that much air through stock heads/cams, they ARE NOT the bottle-neck.
Buy Tomei 268 cams and we'll see what these heads can flow: http://www.z1auto.com/prodmore.asp?m...ine&prodid=521
http://www.tomei-p.co.jp/_2003web-ca..._camshaft.html
Yes, VQ35 heads are superior and AMAZING(105% VE on 350Z even), however with Mardi, Hal, etc. pushing that much air through stock heads/cams, they ARE NOT the bottle-neck.
Buy Tomei 268 cams and we'll see what these heads can flow: http://www.z1auto.com/prodmore.asp?m...ine&prodid=521
http://www.tomei-p.co.jp/_2003web-ca..._camshaft.html
Originally Posted by Stephen Max
I need to qualify this by saying that the VQ35 heads are a big improvement in flow, nevertheless.
02-10-2005, 02:47 PM
#24
Senior Member
Join Date: Aug 2000
Posts: 2,151
You guys are all wrong
It's something really simple.
http://www.airpowersystems.com.au/35...ank_signal.htm
It's something really simple. http://www.airpowersystems.com.au/35...ank_signal.htm
02-10-2005, 02:57 PM
#25
Say again?
Originally Posted by IceY2K1
....There is a THIRD suspect, which is the crank position sensor wire supposedly picking up interference on the way to the ECU and causing a catostrophic failue due to wrong firing time. Anyways, they are selling a shielded cable or something to combat this and rumor had a TSB coming out, but nothing so far.
Originally Posted by MAX2000JP
You guys are all wrong It's something really simple.
http://www.airpowersystems.com.au/35...ank_signal.htm
It's something really simple. http://www.airpowersystems.com.au/35...ank_signal.htm
02-10-2005, 04:03 PM
#28
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Join Date: Aug 2000
Posts: 2,151
Originally Posted by IceY2K1
Hahaha....you don't really think that's the cause of them all, do you?
I've seen the damage in the pictures, MOST were detonation caused...not ECU firing at the wrong time.
I've seen the damage in the pictures, MOST were detonation caused...not ECU firing at the wrong time.
"When the signal from the crank angle sensor becomes erratic, so does the ignition timing (in addition to other functions). Ignition timing is a vital tuning parameter particularly in forced induction applications. If the ignition timing becomes retarded from the optimum point, the engine will produce less power and torque. However, and most alarming is when the ignition timing becomes advanced from the optimum point, pre-ignition and detonation may occur. Detonation places extremely high loads upon a variety of engine components such as pistons, conrods, bearings etc and the chance of failure of each or all of those components becomes very high."
02-10-2005, 04:08 PM
#29
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Just buy a VQ30DE, put that bottom end in under your VQ35DE heads and intake manifold. It drops the compression down to 8.9:1 and you have a much better/higher flowing upper end, the more agressive VQ35 cams and the VQ30's boost proven bottom end. You can pick up a used VQ30 for like 400$. It'd be cheaper than buying aftermarket internals.
Doing the opposite (VQ35 bottom/VQ30 upper), as someone suggested, would bring the comp up to 11.5:1. Horrible for boost.
Doing the opposite (VQ35 bottom/VQ30 upper), as someone suggested, would bring the comp up to 11.5:1. Horrible for boost.
02-10-2005, 04:39 PM
#31
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Originally Posted by JClaw
Just buy a VQ30DE, put that bottom end in under your VQ35DE heads and intake manifold. It drops the compression down to 8.9:1 and you have a much better/higher flowing upper end, the more agressive VQ35 cams and the VQ30's boost proven bottom end. You can pick up a used VQ30 for like 400$. It'd be cheaper than buying aftermarket internals.
Doing the opposite (VQ35 bottom/VQ30 upper), as someone suggested, would bring the comp up to 11.5:1. Horrible for boost.
Doing the opposite (VQ35 bottom/VQ30 upper), as someone suggested, would bring the comp up to 11.5:1. Horrible for boost.
02-10-2005, 11:32 PM
#32
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No. Just do like Tilley. Use the entire 3.5 upper end (heads AND intake manifold) and put a 2001 pathfinder 70mm throttle body. Cable driven, but the same size as all other VQ35DE throttle bodies.
You can also mod the VQ35DE electronically controlled throttle body to be cable driven, that's what Tilley did when he swapped his 3.5 in his girl's '97. Both ways will work fine.
For example, here are his dyno results:
VQ35DE bottom end w/VQ30DE heads & 00-01 VI and super high 11.5:1 compression= 226whp and 205wtq
full VQ35DE (still off his 4th gen ECU) and normal 10.3:1 compression: 233whp and 230wtq.
So, the comp dropped 1.2:1, and he still got a gain, up 7whp peak, but it's a torque monster: up 25wtq thanks to better flowing upper end. Imagine the same % of gains on a boosted max!
You can also mod the VQ35DE electronically controlled throttle body to be cable driven, that's what Tilley did when he swapped his 3.5 in his girl's '97. Both ways will work fine.
For example, here are his dyno results:
VQ35DE bottom end w/VQ30DE heads & 00-01 VI and super high 11.5:1 compression= 226whp and 205wtq
full VQ35DE (still off his 4th gen ECU) and normal 10.3:1 compression: 233whp and 230wtq.
So, the comp dropped 1.2:1, and he still got a gain, up 7whp peak, but it's a torque monster: up 25wtq thanks to better flowing upper end. Imagine the same % of gains on a boosted max!
02-11-2005, 07:55 AM
#34
Out of 15-20 blown motors on the 350Z board I read, there are A LOT more, 1-2 are suspect of this issue.
I'd guesstimate this is a 10% or less occurance and people are using it as an escape goat to sell their "solution to the problem". Problem really is that Nissan weakened the internals by reducing weight and when people throw TT kits that produce healthy amounts of torque at low RPM, rods bend/snap. Even Nissan knows the rod bolts can't sustain 7200+rpm, so Nismo sells rod bolts, and even after those they don't specify any higher. Then for the 2005 "300hp" Z and "290hp" G, they redesigned the COMPLETE rotating assembly. So, apparently Nissan has something in mind for the future or the 3rd gen VQ35s were near their limit at 287hp to cause a complete redesign for a minor 13hp increase.
Anyways, the CPS->ECU shielded cable is not just a "simple" black/white here is the answer to your bending rods as you made it sound.
I'd guesstimate this is a 10% or less occurance and people are using it as an escape goat to sell their "solution to the problem". Problem really is that Nissan weakened the internals by reducing weight and when people throw TT kits that produce healthy amounts of torque at low RPM, rods bend/snap. Even Nissan knows the rod bolts can't sustain 7200+rpm, so Nismo sells rod bolts, and even after those they don't specify any higher. Then for the 2005 "300hp" Z and "290hp" G, they redesigned the COMPLETE rotating assembly. So, apparently Nissan has something in mind for the future or the 3rd gen VQ35s were near their limit at 287hp to cause a complete redesign for a minor 13hp increase.
Anyways, the CPS->ECU shielded cable is not just a "simple" black/white here is the answer to your bending rods as you made it sound.
Originally Posted by MAX2000JP
I am sure poor tuning, bad gas, etc. could also be the cause. My friend Brian just ordered a APS TT kit and was told by one of the nation's best 350Z tuners that this was the problem. Detonation is what kills an engine and APS's explanation seems to hold true.
"When the signal from the crank angle sensor becomes erratic, so does the ignition timing (in addition to other functions). Ignition timing is a vital tuning parameter particularly in forced induction applications. If the ignition timing becomes retarded from the optimum point, the engine will produce less power and torque. However, and most alarming is when the ignition timing becomes advanced from the optimum point, pre-ignition and detonation may occur. Detonation places extremely high loads upon a variety of engine components such as pistons, conrods, bearings etc and the chance of failure of each or all of those components becomes very high."
"When the signal from the crank angle sensor becomes erratic, so does the ignition timing (in addition to other functions). Ignition timing is a vital tuning parameter particularly in forced induction applications. If the ignition timing becomes retarded from the optimum point, the engine will produce less power and torque. However, and most alarming is when the ignition timing becomes advanced from the optimum point, pre-ignition and detonation may occur. Detonation places extremely high loads upon a variety of engine components such as pistons, conrods, bearings etc and the chance of failure of each or all of those components becomes very high."
02-11-2005, 07:59 AM
#35
What I've heard is the crank signal issue as well. I've heard that the 350z ECU is screwy in that it does not respond well AT ALL to piggyback management. Supposedly it tries to thwart the efforts of piggyback ecus and revert to less FI friendly parameters. I know a guy (same guy Jason knows) who put almost 500 to the ground on stock internals, and there are others too. Most of these folks are running standalone to my knowledge, which takes the quirkiness of the 350z ecu out of the equation.
02-11-2005, 08:12 AM
#37
Originally Posted by IceY2K1
BS....tons of guys running Greddy kits in 400+whp for over a year now and even more ATI Procharger guys.
It's a witch hunt.
It's a witch hunt.
02-11-2005, 08:13 AM
#38
Yes, it would drop compression.
The intake ports on the newer VQ35 heads are angled different and require a VQ35 manifold. However, you could use the 2001-2004 Pathfinder VQ35 heads maybe, since they used a similar type port.
You're SC'd, so you don't need/want to drop compression, just buy cams and you're going to flow plenty of air.
The intake ports on the newer VQ35 heads are angled different and require a VQ35 manifold. However, you could use the 2001-2004 Pathfinder VQ35 heads maybe, since they used a similar type port.
You're SC'd, so you don't need/want to drop compression, just buy cams and you're going to flow plenty of air.
Originally Posted by chris'smax
So using the 3.5 heads brings down the compression right? Also would you want to use the 3.5 intake manifold or just keep the 2000 vi