bruschijr

ENGINE GREMLINS.....


But seriously.... does anyone know anyone who blew thier stock engine? I want to see if the crank sensors are causing the same problems as stock.

spazpilot

iTrader: (2)

Two words. BAD TUNING !!!!!!. I really honestly believe that on a car like ours there will never really be a plug and play. I think a lot of the people are blowing up there motors because of no or bad timing retard and fuel adjustment. Some do better then others but make sure that the application your running mates well with your setup. I have been running my car at 9.5psi daily for about a year now and still no problems. Tuning tuning tuning!!!!.

bruschijr

im sure thats over 90% of the problem...

I was just thinking if anyone knows of a stock engine blown.. then maybe it was just the engineering... If stock engines are failing then it could be more of a rod issue/crank sensor issue than timing and fuel...

I know the latter of the two are definatley culprits... but it could be possible that even with the correct tuning they are just bound to fail..... did you see the post on the stock tolerance levels... some engines could just be built to the limit from the getgo...

schweatty

iTrader: (2)

by stock engine do you mean NO FI or just not a built engine? anytime you add FI to an engine not designed for FI combined with **** poor tuning and a heavy foot there is always going to be something. right now it seems like connecting rods can go, but if it wasnt throwing a rod it would be something else that will fail based on the previously mentioned reasons. just my $.02

Aloharacing

iTrader: (1)

Approx. how many miles have you put on your car in the past year? Mostly city or highway?

bruschijr

sorry, what i was trying to find out was..

Were there any Z's... lets say straight from the dealer.. no mods to the drivetrain/engine/electronics... etc..

Has anyone heard of someone blowing thier engine under any circumstances like mentioned above?

I was just really trying to figure out how essential the rod replacement was.. (I'm definatley doing that) but... are factory rod tolerances so far in range that they could be damaged in a completely stock motor? Someone brought this subject up a while ago refering that some engines might be built stonger than others from the factory due to the tolerances... and thats why some engines with proper tuning were dying and some weren't.. If this can happen on a bare stock (NO Mod) engine... then there should be no reason why anyone should get any FI mod at all, even on low boost settings, without building the bottom. In other words.... Is it possible that you are taking a chance by guessing on the tolerance that your specific engine was built to...?

Thats what I was trying to get at.. with so many blown engines who knows.

Should you even go FI at all with this engine without building it up?

spazpilot

iTrader: (2)

12k both city and highway with a few passes at the strip and top speeds in the 180's. I beat the living sh@t out of this thing and works great. The three ploblem I have had were the greddy oil pan leak so I had to re weld one of the return tube. I had the power steering issue and the stupid paper gasket wastegate flang leak. All of them have been fixed and it runs just great. I few thing other then the TS ecu I have done that may help in longivity was I use denso IKH22 2 step colder plugs, a nismo 170 thermostat and the koyo radiator. I pretty sure these items help especially the plugs.

spazpilot

iTrader: (2)

The way these engines are build today i am pretty sure tolerances could be way out there, but in the same note I have not heard of one just blowing or falling apart stock.

350zDCalb

iTrader: (21)

my engine was tuned well and i was pulling timing... and it blew up...i don't think blaming it on fue;/tuning paints the picture.....my little theory (kind of more like just accepting everyone elses' imput and picturing what happens)...the rods are stressed beyond belief with FI and then they finally take a dump and break...plain and simple, they can't tolerate anymore and they give up!!!
those who still have FI on a stock motor and have not blown yet, i don't want to be negative, but the time bomb is ticking...the timing/fuel/tune definately helps...i agree with gq's theory of different stock rods being a little stronger than others

my $0.03

zbicklin

My $0.04... If you look at what F/I does whether TT or S/C you are effectively doing one major thing: Increasing cylinder presure. On the front end (compression stroke) you have much more air and fuel to compress which basically raises the "effective compression ratio" of each cylinder. On the combustion stroke there is a much bigger explosion so that creates more stress on the piston and rods to handle.
With perfect air/fuel and timing you are making the best of a tough situation for your engine so you can go much longer without any major problems (in theory).
TT cars cause greater stress on the engines compared to centrifugal blowers because they build boost earlier. With more effective compression and combustion to overcome at a lower engine speed, the fuel and timing factor becomes much more important.
I guess bottom line is good a/f and timing throughout the power band certainly will help keep your engine happier longer with F/I but ultimately there's alot more stress for the pistons, rings and rods to take.

7 eleven

load on the con-rod:

Tensile, which is a stretching load

Compressive, which as it is sounds, is the load from the rod being compressed.

Tensile is far more damaging because a tensile load is fatigue inducing. This means over time the same level of force if high enough will cause failure even if it does not cause an immediate failure.

Tensile loads are what con-rods are designed for at the factory due to the higher loads that they cause. Tensile loads are the highest at the end of the exhaust stroke due to no cylinder pressure to push down and reduce the load, and the load increase with rpms is squared, so going from 2000 to 8000rpms will increase it by a factor of 4.

The compressive load is less because of several reasons; there is tensile load working against it at high cylinder pressure thus canceling out some of the load. When you double the amount of air and fuel in the camber the peak pressure only increases about 20%. This is due to the fact that power is a result of effective pressure over the whole power stroke thus your increase in power comes mainly from the higher average pressure not solely from the increase in peak pressure. Also your compressive load decreases after peak torque due to less complete filling of the cylinder because of a shorter amount of time to fill it.

So with this knowledge you can see that a con-rod failure at higher than peak torque with no detonation is mostly due to a failure due to tensile loads and has nothing to do with the amount of power generated.

But if the failure occurs before or at peak torques it is most likely a compressive failure of the con-rod and can happen due to detonation or a really high power load.

For example G35cTT's recent loss was more than likely a tensile failure due to the high rpms and had little to due with the power load, except it was probably the power that allowed him to spin that high before the rev limiter cut in.

Of course all of this assumes a good tune.
All this information is in,
Maximum Boost, by Corky Bell (very clearly written)
Engineering Fundamentals of the Internal Combustion Engine by Willard Pulkrabek (allot more details)
The Internal Combustion Engine in Theory and Practice by Charles Fayette Taylor (Very heavy in the mathematics side of things)
Gary

350zDCalb

iTrader: (21)

that was at least $0.12...well written

zbicklin

Hey 350zDCalb,

How do you like your AAM fuel system? I live not to far from them and they do my dyno tuning. I was planning on getting the kit and installing with 255lph pump and 440cc injectors. I heard from a couple threads however that they don't address the siphon from the driver's side of the tank and you shouldn't go below 1/4 tank. Is this an issue with you?
Sorry to hi-jack the thread... Feel free to PM me if you like.

Steve

Sharif@Forged

iTrader: (92)

7Eleven hit it on the head. Essentially, when you double the power output of a motor through F.I...you are not putting double the amount of load on the rods. Inertial loads on the rod are highest at peak trq and when the piston is at TDC or BDC...the point when it changes direction. Youll notice that many people snapped rods in the middle of the power band...peak trq...not near redline.

Also note that peak combustion occurs at around 20 degrees after TDC...not at the TDC, when loads would be highest. So you sorta get a free lunch in a sense...with F.I.

All that said...I think we are up to a $1.50 at this point...it would be wise to have a 11.0:1 A.F ratio very early in the power band...around 2800rpm or even slightly less at WOT...since the TT¨s are generating massive trq...even at 3000rpm. Also get aggresive with timing retard at this point as well.

350zDCalb

iTrader: (21)

i have the aam system in my room...not yet installed..sorry, can't provide any feedbacl for at least another month

-TODD