As many of you may have heard Nissan 350Z have a huge aftermarket now.

Twin Turbo kits make huge performance over the entire powerband alas a few have been breaking rods.

Sometimes ( not usually, but sometimes) these were cars running "stock" boost , for that kit, with supposedly good tunes.

Now I wonder when the torque peak comes on at higher rpm, like on a single turbo kit ( a couple xist now for 350Z) would that be easier on the rods?

Fred..

I wouldn't think so. I'm not a Guru or anything- but I would think that the force being applied to the engine would be the same if the boost was the same at a given RPM, regardless of torque peak. If you get more boost sooner, the stress across the powerband would be more with twin turbos....

*shrug*

I woult think more boost at higher RPMs would be more detrimental than less boost across all RPMs....

Just my thoughts...I don't really know enough to be posting, but what the hell...

(I'm a suspension guy..leave me alone!)-Chet

I was thinking if the say 300 crank lbsft of torque at 5000 rpm might be easier on the rods than 300 lbft at 3000 rpm as the force gets spread out more per stroke?

There is a sense on another forum that the single turbo 350z applications might be safer for the rods despite making nearly as much peak power as the twin turbo kits..

I dunno...

Fred..

I think that it would be worse at higher RPMs... High RPM always causes more stress on the engine, because the stroke is a lot more violent..... Adding more power to higher RPM will only increase stress.....

Another issue that I feel may play a role is the lower quality wire for the CAS.

Some say a dangerous false signal can interpreted by the ecu from the CAs causing detonation in some cases.

I wonder if this plays a role in these failures.APS includes a high quality shielded CAS wire for their (expensive but high end) twin turbo kits for this reason.

On this note, I have a less than perfect idle from day one.

Dealer refuses it acknowledge it as a problem as no codes are thrown.

Also I wonder how consistent the Z's are tuned from the factory.

As some have this uneven idle which has been cause by (on different cars), faulty coil packs, faulty ECU wiring, poor factory grounds.

If you put on a pre-tuned emnaged forced induction kit and it asumes exact stock behaviour on the part of your car but the cars runs stock all over the map maybe this is a contributing reason to these occaisional failures?

These failures arent real common but you couldnt call 'em rare either.

Fred..

PS: I am moving this to Z forum

As soon as you get settled in, you might see if you can find another dealer that will be more willing to help...

I will ask, is the fuel management a piggy back ECU?

As many VQ engines as there are, you cant assume that all of them will be the same.....

Fred wrote:If you put on a pre-tuned emnaged forced induction kit and it asumes exact stock behaviour on the part of your car but the cars runs stock all over the map maybe this is a contributing reason to these occaisional failures?

I think more or less it would contribute to certian things on the engine (meaning internals).. Its possible that some engines arent torqued right, or there are certain other things that cause it to fail... Obviously, throwing on a turbo is gonna make these defects more apparent...

I assume your running under 10 PSI, yes? Also, the fuel management systems have to have some built in range of safety, to prevent such things.. A lot of the really good piggy bcak ECU (at least the JWT one for the Q's supercharger) base the ignition open time upon the MAF voltage.. I dont really see how sudden changes in the CAS could be blamed on the harness, unless it is split somewhere and grounds itself...

The bottom line is, by adding any sort of boost, your taking a risk.. its possible that youll occur no hardaches, or you could blow the motor after 2 runs..... But the answer to the question, will it cause more stress on the engine at lower RPM or higher RPM, i definitely say at higher RPM

the greatest stress to the connecting rod occurs at the end of the exhaust stroke. when the piston is pushing the last of the spent gases, there's no cushion (intake charge) in the combustion chamber. the piston violently yanks on the connecting rod when it reaches tdc. to add to the rods' misery, the crankshaft now begins to snatch it downward. it is now forced to fight against the drag and friction caused by the weight of the piston and piston rings. and the final kill is during this stroke it also has to deal with the tensile load of sucking in air and fuel through the intake valves.

the engine that produces the broader powerband puts stress on the rods for a longer duration since the engine is spinning slower, but the engine that makes the same power with higher rpms is more violent.

the way i see it, the 350Z just has some questionable rods.

-demetrius

"Stock boost" with these applications ranges from 5.6 psi ( TT) to 7 psi (most SC's and one TT) to 8 psi (Vortech) to 9 psi (Vortech w/ pully)

Boost pressure means nothing in total cylinder pressure. You need to basically consider mass flow at the point of peak torque production and deduce from that to obtain the cylinders dynamic CR at that point.

The problem with those kits is that you have total engine meltdown at a stones throw away. They are all chasing each other in power numbers to sell their kits which has led to pushing the engine further. I suggest the APS kit, running about 6-7 PSI tops and make sure you get your gas from a reputable, high volume gas station. You should also be very conscious of your base timing with that motor. Verify your static timing before the kit goes on.

If I were in your shoes, I would completely rebuild a motor on the side with forged internals to boost. I wouldn't even consider junking your only mode of transportation with a what if situation. It's cheaper to build the motor now, before you call Nissan for a $6000 shortblock cause you punched a hole in it.

Do it right the first time.

true words Alan:

You know the $$ in those VQ35 build ups I am sure..

Maybe I'll just leave it bone stock and do only cosmetic Mods..

Or I'll take a gamble with one of those single kits from Turbonetics (5k installe) turn the boost low and should be ok for a couple years, when used engine become cheaper I turn it up a bit..Or not as Many Sc's have ben blowing as TT kits, go one of those and run 1 psi less than what they are meant to rin, I am sure there can be pully's had for that.

One good thing about the Vortech and the single turbo is the install/uninstall is eaSY. So if I blow the engine installing a new (used) one doent mean so much extra labor..

Fred..

PalmerWMD wrote:true words Alan:

You know the $$ in those VQ35 build ups I am sure..

Maybe I'll just leave it bone stock and do only cosmetic Mods..

Or I'll take a gamble with one of those single kits from Turbonetics (5k installe) turn the boost low and should be ok for a couple years, when used engine become cheaper I turn it up a bit..Or not as Many Sc's have ben blowing as TT kits, go one of those and run 1 psi less than what they are meant to rin, I am sure there can be pully's had for that.

One good thing about the Vortech and the single turbo is the install/uninstall is eaSY. So if I blow the engine installing a new (used) one doent mean so much extra labor..

Fred..

A single turbo isn't going to be any softer on the rods than twins. Neither are the S/c's.

If you want longevity out of this engine just put some n/a bolt ons on it and call it a day.

Empirically almost all rod failures have been from twin trubo kits above 400 whp.SC's not a single rod failure yet that I read about except they seem to be hard on the rings.

A good NA set-up will be 5000-7000 and give less power than a single SC bolt on..

But I definetly hear you on the longevity am just concerned I might spend a lot of dough and have little to show for it. there is a guy on another site that put $7000 in NA mods on his 350 and gained less than 30 hp at the wheels..

Fred..:

ah, the problems with buying a car thats so darned good stock!

the rods are so light with very little cushion give the most output that could safely be achievedditto for the pistonsi have seen both firsthand and they look pretty wussy(think non-vtech civic)the ign is optimised for na and wants to ping on boost(esp sc cars)

my freind, if you want to pull hard then i think you need internals. i have seen the factory that the vq's are built in(at least they were) and its amazing. i dont think they have very many imperfections due to improper assembly/machining.

if you just want to go fast...slap on some konis, sway bars, and so3's. that should be worth a few seconds when road racing.

still, i would want mine to pull hard soooooooo...rods, pistons, and a single turbo setup with something garrett(gt and bb) is where i would go. while your in there get some cams and just be faster than anyone else.

Ahhhh get the S/C and you will love it!



j/k Fred.

I can't wait to see what you get next and what numbers you get out of it.

personally guys tuning is alot of itthe rods are weak, 400 and up is really pusing it.

but heres the blown motors

+damn near every ATI procharger has blown, but similar designed kits like vortech dont, ati has ****ty engine management so id guess thats a big part of it.+alot of greddy TTs have blown, im guessing bad fuel management is too much punishment on the rods.+no Power enterprise 350z have blown, and ive seen a few under heavy track abuse, running either the technosquare flash, or FCON V pro. +APS only has a couple in the country, ive met one of the guys, and he drives his car extremely hard so it seems like its not gonna have any problems. just a warning though with APS: if something breaks, say a IC pipe cracks, it will take months upon months to get the part replaced, they have no US office and the guy incharge of dealing with us, peter, is an idiot.+neither turbonetics or APS have their single turbo in full production yet, i dont think they will have problems though.+impul just released their single turbo kit(Saw it in person at tokyo autosalon, this is me bragging) it looks really nice, but its $12k so i dont think anyone here will buy it.

this is all the stuff in my head about turboing my Zim going with power enterprise because i trust its turbos, it includes a good fuel system, they just came out with cast manifolds to reduce the price, and the intercooler is an ARC and very nice.

forgot to mentionone g35 sedan has had alot of problems with his car after the PE kit, and eventually blew his motor, hes the only person to have problems with the kit and they didnt know the cause last time i checked.

PalmerWMD wrote:Empirically almost all rod failures have been from twin trubo kits above 400 whp.SC's not a single rod failure yet that I read about except they seem to be hard on the rings.

A good NA set-up will be 5000-7000 and give less power than a single SC bolt on..

But I definetly hear you on the longevity am just concerned I might spend a lot of dough and have little to show for it. there is a guy on another site that put $7000 in NA mods on his 350 and gained less than 30 hp at the wheels..

Fred..:

We went 12.98 on N/a mods maybe totalling about $3500

If you wanted bang for the buck you should have kept the S13 honestly, but that is in the past.

I think you should keep the 350Z stock and build yourself an S13/14 on the side. With $6000 you can buy and S13 and build a KA-T running about 300rwhp. You don't want your daily driver to be the hotrod either.

im selling my s13sr to fund my TT kit for my Z