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View Full Version : Power Mods what causes the most stress on an engine?



tony
08-06-2005, 10:24 PM
I've been doing a lot of reading lately.. trying to get a handle on what direction to go in as far as hp goes. I'm still learning a lot but I cannot seem to get a final answer to this question.. what causes the most stress on an engine? is it horsepower, torque, boost level?

From the opinions I've received its torque.. just wanted to know what you guys think.

THEONE
08-06-2005, 11:14 PM
i would have to say its abuse that puts stress on most motors or neglect.running a turbo when set up properly is pretty reliable as long as the person driving the car uses thier head and doesnt get crazy,and that goes for all motor and high compression too. just dont go crazy with your boost and get the proper tuning and fuel system to support your boost level and your golden.and be sure that you know what your motors limits are and keep it real.i would rather have a stock block whatever with a 6psi of boost than a stock block whatever with 15psi and a hole in the piston or bent rod;)

sebastianHoff
08-08-2005, 10:06 PM
detonation causes stress on an engine. if you tune the motor properly then the 3 things you mentioned arent really a problem.

topsecret2JZ
08-08-2005, 10:17 PM
driving like a dick all day

BTEC
08-09-2005, 08:44 AM
I would say torque at low rpm and inertia at high rpm. Yeah, that sounds good.

Vteckidd
08-09-2005, 11:27 AM
Detonation=#1 cause of engine failure.

Boost levels can cause extreme wear too cause of the cylinder pressure and temperature it creates. EGT gauges are a good thing.

Its kind of and open ended question, cause WHP and TQ is all dependent on what boost level you run.

But a car UNTUNED on 10psi that spikes a/f to 15:1 at some points on the map, is in much greater danger than say Peters car which has 30psi running through it , and its built and tuned out.

Detonation is worse than taking a .40 rifle and shooting the top of the piston. watch the Omniman Video

tony
08-09-2005, 12:05 PM
I'm just trying to kick around some ideas. I have no problems with detonation at all, EGT's are relatively low..

Heres my dilema, untuned my car hits 10psi on a regular basis sometimes 11psi. The car is making 406whp at 9psi and with a proper tune I should get around 430-450whp @ 9psi. 470whp is possible at 10psi but I'm not sure if I want to push the engine like that just yet, the rods are the weak link in the VQ motor so I'm wondering if torque is the number I should be concerned about rather than boost or horsepower.

Vteckidd
08-09-2005, 03:04 PM
I'm just trying to kick around some ideas. I have no problems with detonation at all, EGT's are relatively low..

Heres my dilema, untuned my car hits 10psi on a regular basis sometimes 11psi. The car is making 406whp at 9psi and with a proper tune I should get around 430-450whp @ 9psi. 470whp is possible at 10psi but I'm not sure if I want to push the engine like that just yet, the rods are the weak link in the VQ motor so I'm wondering if torque is the number I should be concerned about rather than boost or horsepower.
heres my .02:
all motor are different. if you have to run MORE boost to get the SAME power, its a flow problem. what size exhaust do you have? what size DP? i would look to getting a 3in exhaust to see how much you numbers would increase, Dyno open downpipe too and see what happens.

In your case i would be worried about Boost levels, those rods will buckle, we all know it. is it worth it for a few extra whp?

tony
08-09-2005, 03:37 PM
That is what I'm wondering.. if its even worth it. 450whp safe or take the chance of going higher... I'll probably go the safe route for now. I currently have a 3in exhaust.. the next best thing is a 2.5in true dual exhaust but those are $1400 shipped, I cant justify paying that much for a couple of extra horses.

Spyder
08-09-2005, 04:27 PM
That is what I'm wondering.. if its even worth it. 450whp safe or take the chance of going higher... I'll probably go the safe route for now. I currently have a 3in exhaust.. the next best thing is a 2.5in true dual exhaust but those are $1400 shipped, I cant justify paying that much for a couple of extra horses.

People that pay 1400 bucks for some exhaust are crazy as hell, the 2.5 inch they sell doesnt flow any better then the 2.5 inch custom mandril bent and installed exhaust you can get from a local shop for 400-600 bucks. 3 inch is normally plenty good, do like vteckidd said and dyno it with open DP if it makes that much of a difference then you need bigger exhaust, if not don't worry about it. there is always the option of running electronically controlled actuator that will basically dump the exhaust when you want that extra power and let you ride somewhat quiet when you don't.

To awnser you inital question , what causes the most stress on your motor belive it or not it is cold starts followed by detonation. I dont know what you are building your car for but if you want to get to a certain mark just to say you did (say 500 whp) and you are already at 450, then it isnt hard to to. just add some water injection or another power adder. Is it worth it when the rods are the weakest link? imo.. no. some people feel differently, but for me it isn't worth making an extra couple whp to take a motor that may last for 60k miles in its current tune state and blow it up just to say you are in the 500 whp club.. for a week. On turbo cars remember when you are even semi close to pushing the limits that keeping fresh plugs in the motor is a MUST.

Also remember when having it tuned there is reliable and then there is aggressive, know the tuner you are using and what style tuner they are.

tony
08-09-2005, 04:46 PM
You know why people pay $1400? MSRP is actuall $1800 or so but its because of the titanium tips and the exhaust note. It doesnt give any more real gains than the other exhausts.. not to say I wouldnt mind having one though. With the 350Z and G35 all of the modifications are expensive as hell.. Nismo headers cost $1000 plus installation is usually $500. Cams expect to pay $2000 installed.. The clutch and flywheel I had was $1500 installed.. and those N/A mods give you modest gains at best.

Spyder
08-09-2005, 04:53 PM
You know why people pay $1400? MSRP is actuall $1800 or so but its because of the titanium tips and the exhaust note. It doesnt give any more real gains than the other exhausts.. not to say I wouldnt mind having one though. With the 350Z and G35 all of the modifications are expensive as hell.. Nismo headers cost $1000 plus installation is usually $500. Cams expect to pay $2000 installed.. The clutch and flywheel I had was $1500 installed.. and those N/A mods give you modest gains at best.

exactly my point, so get a cut out and ride in a car that isnt loud as hell then when you are doing whatever that you need to make power press a button and in 10 seconds you suddenly have the equvalent of a DP for exhaust.

I have a friend with a bimmer, it seems they are about on the same level in terms of cost to modify.. some of the bimmer guys have a short ram carbonfiber intake that cost about 800 bucks, and they think it was worth it. :rolleyes:

Vteckidd
08-09-2005, 10:38 PM
I wold play it safe and be happy where you are at. im sure its FAST AS HELL with 400whp on tap. I would be happy knowing its semi relaible. i mean, if you want to just say it made "XXX whp" then run race gas and turn the timing up. but be prepared, detonation at 400whp is a bitch ;)

civic95
08-19-2005, 11:01 AM
I would say your problem here is that your not tuned at all.

400WHP untuned at 10PSI is potentially more dangerous than 450WHP tuned at 10PSI. With that said I don't care how good it's tuned boost is boost. Boost puts a lot of pressure on the bearings, and if your lucky and tuned right they will be the first thing to fail.

HiPSI
08-19-2005, 12:51 PM
pistons move in a straight line motion, rods move in an up/down and circular motion. the forces affecting these parts are not torque as torque is purely a twisting motion.

if you want to break it down to the basics the main thing here is cylinder pressures, the amount of force placed on a piston causing it to move through it's travel. good tuning keeps the pressures fairly even between cylinders, but as you increase HP, you're increasing the amount of pressure in the cylinders (more air/fuel=stronger burn=more pressure). the piston is pushing down on the rod when the cylinder fires and then the rod translates that motion into the crank to create torque. at a certain level, the force placed upon the rod will cause it to bend/break or you can shatter/blow a hole in a piston. in a perfect world these consistant pressures would make the engine more reliable as long as they are kept below the breaking point of the parts in the engine, but this is never the case.

this is where detonation comes in, because it causes huge spikes in the force upon the internals. preignition/detonation causes the air/fuel to burn while the piston is still traveling upward being pushed by the rest of the engine, so it's kind of like the difference between running your car into a stopped semi truck at 30mph or hitting the same semi truck head on when they're coming at you at 60mph. the forces placed on the parts are multiplied, and then suddenly your nicely tuned engine becomes shrapnel. the counterpart to this is heat, because as pressure increases so does the temperature (why tune by the EGT gauge ;)). extreme pressure causes extreme heat, which compounds the problem of bad tuning causing burned pistons/valves if you're lucky enough not to throw a rod through the block.

Jaimecbr900
08-19-2005, 02:00 PM
Very good informative thread.

I have a friend that had a 5th Gen Max. He was going to build a stroker motor and had the parts laying there to do it. He was already running boost on his VQ motor. I was told that he wanted to find out how much the engine would take before messing up, since he already had another engine waiting in the wings. I was told that he turned up the boost (obviously he was upping everything else he could to keep up) and from what I heard it held. He was somewhere up there in the power levels you're talking about, 450-500hp. Again, this was heresay although I could make a phone call to find out for sure.

Point is that the VQ motor may have some issues with the rods, but I have a sneaky hunch that may be more related to tuning than inherently weak parts. Again, this is only my opinion, but I did do a ton of nitrous squeezing into my 95 Max with a VQ30 motor in it and the motor is still perfectly fine. I think that tuning properly with a good eye on the a/f is the key.

tony
08-19-2005, 03:53 PM
Very good informative thread.

I have a friend that had a 5th Gen Max. He was going to build a stroker motor and had the parts laying there to do it. He was already running boost on his VQ motor. I was told that he wanted to find out how much the engine would take before messing up, since he already had another engine waiting in the wings. I was told that he turned up the boost (obviously he was upping everything else he could to keep up) and from what I heard it held. He was somewhere up there in the power levels you're talking about, 450-500hp. Again, this was heresay although I could make a phone call to find out for sure.

Point is that the VQ motor may have some issues with the rods, but I have a sneaky hunch that may be more related to tuning than inherently weak parts. Again, this is only my opinion, but I did do a ton of nitrous squeezing into my 95 Max with a VQ30 motor in it and the motor is still perfectly fine. I think that tuning properly with a good eye on the a/f is the key.

You are absolutely correct, there are some guys blowing their engine on the dyno at 5psi then there are others with 10k+ miles pushing 11-12psi and its all due to tuning.

tony
08-19-2005, 03:56 PM
I would say your problem here is that your not tuned at all.

400WHP untuned at 10PSI is potentially more dangerous than 450WHP tuned at 10PSI. With that said I don't care how good it's tuned boost is boost. Boost puts a lot of pressure on the bearings, and if your lucky and tuned right they will be the first thing to fail.

Its tuned for 91 octane.. but that is a base map, I'm talking about raising the boost a little and getting a custom tune.

tony
08-19-2005, 03:58 PM
pistons move in a straight line motion, rods move in an up/down and circular motion. the forces affecting these parts are not torque as torque is purely a twisting motion.

if you want to break it down to the basics the main thing here is cylinder pressures, the amount of force placed on a piston causing it to move through it's travel. good tuning keeps the pressures fairly even between cylinders, but as you increase HP, you're increasing the amount of pressure in the cylinders (more air/fuel=stronger burn=more pressure). the piston is pushing down on the rod when the cylinder fires and then the rod translates that motion into the crank to create torque. at a certain level, the force placed upon the rod will cause it to bend/break or you can shatter/blow a hole in a piston. in a perfect world these consistant pressures would make the engine more reliable as long as they are kept below the breaking point of the parts in the engine, but this is never the case.

this is where detonation comes in, because it causes huge spikes in the force upon the internals. preignition/detonation causes the air/fuel to burn while the piston is still traveling upward being pushed by the rest of the engine, so it's kind of like the difference between running your car into a stopped semi truck at 30mph or hitting the same semi truck head on when they're coming at you at 60mph. the forces placed on the parts are multiplied, and then suddenly your nicely tuned engine becomes shrapnel. the counterpart to this is heat, because as pressure increases so does the temperature (why tune by the EGT gauge ;)). extreme pressure causes extreme heat, which compounds the problem of bad tuning causing burned pistons/valves if you're lucky enough not to throw a rod through the block.

This had to be the most helpful post I've seen yet, I appreciate the knowledge.

Vteckidd
08-19-2005, 05:39 PM
this is where detonation comes in, because it causes huge spikes in the force upon the internals. preignition/detonation causes the air/fuel to burn while the piston is still traveling upward being pushed by the rest of the engine, so it's kind of like the difference between running your car into a stopped semi truck at 30mph or hitting the same semi truck head on when they're coming at you at 60mph. the forces placed on the parts are multiplied, and then suddenly your nicely tuned engine becomes shrapnel. the counterpart to this is heat, because as pressure increases so does the temperature (why tune by the EGT gauge ;)). extreme pressure causes extreme heat, which compounds the problem of bad tuning causing burned pistons/valves if you're lucky enough not to throw a rod through the block.
hence why most high horsepower turbo cars melt down on 4th gear pulls or pull on the highway cause the EGTs go through the roof. at least from whati have seen. lots of long pulls can blow shit up and melt pistons QUICK.

also, its a known fact the 350z motors have weak rods. yes you can get away with 10-12psi, for how long though? i mean, its possible, hell i have seen 450whp stock sleeves and rods in a honda motor, but if you are boosting ALL THE TIME EVERY DAY, it aint gonna last. not IMO

HiPSI
08-19-2005, 05:55 PM
hence why most high horsepower turbo cars melt down on 4th gear pulls or pull on the highway cause the EGTs go through the roof. at least from whati have seen. lots of long pulls can blow shit up and melt pistons QUICK.

that is pretty true overall. long highway pulls, for example, will send me into the red (1600+ degrees) but bursts of WOT for a half mile or so at a time won't get it much over 1400 degrees (measured about 1" from the head flange in the exhaust manifold). it just goes back to square one, it's creating more pressure and more heat. if you stay in it for a long distance the pistons/cylinder walls will eventually soak up that heat and reach their melting point or at least a temp where they will be able to stretch/bend under the loads in the cylinders, then mr. engine goes bye bye :D.

and then again, a bunch of kids with stock SR's will slap on a T28 and turn up the boost well beyond what the stock computer/maf/injectors can handle and do the same thing in about 1/8 mile of jumping on the gas ;).

Vteckidd
08-19-2005, 06:15 PM
that is pretty true overall. long highway pulls, for example, will send me into the red (1600+ degrees) but bursts of WOT for a half mile or so at a time won't get it much over 1400 degrees (measured about 1" from the head flange in the exhaust manifold). it just goes back to square one, it's creating more pressure and more heat. if you stay in it for a long distance the pistons/cylinder walls will eventually soak up that heat and reach their melting point or at least a temp where they will be able to stretch/bend under the loads in the cylinders, then mr. engine goes bye bye :D.

and then again, a bunch of kids with stock SR's will slap on a T28 and turn up the boost well beyond what the stock computer/maf/injectors can handle and do the same thing in about 1/8 mile of jumping on the gas ;).
i agree 100%. in turbo cars its critical to watch EGTs as it really coincides much more with detonation than a NA car.

Its funny to see guys shootign for 400whp but dont even have a EGT gauge