Weak Bottom End???????
- Thread starter PRpimp3o3
- Start date
I've heard just the opposite.
Some here and on SF beleive that the bottom-end can hold upwards of 400 hp, maybe not reliably, but still.
Some here and on SF beleive that the bottom-end can hold upwards of 400 hp, maybe not reliably, but still.
:umno:
I've yet to hear of a high horsepower 7M fragging the stock rods or the crank.
The stock pistons seem to do OK in high output engines but should be replaced if you're looking for over 400 whp. I personally believe they will work past that point with proper engine management. The folks who push the stock pistons that hard and get them to fail typically don't have any kind of spark control. Detonation will kill even the most robust piston.
The 7M bottom end usually fails due to rod knock caused by low oil or poor machine work. That has nothing to do with those parts and uber rods and a custom forged crank can't save an engine from owner and/or machinist negligence. My $.02
I've yet to hear of a high horsepower 7M fragging the stock rods or the crank.
The stock pistons seem to do OK in high output engines but should be replaced if you're looking for over 400 whp. I personally believe they will work past that point with proper engine management. The folks who push the stock pistons that hard and get them to fail typically don't have any kind of spark control. Detonation will kill even the most robust piston.
The 7M bottom end usually fails due to rod knock caused by low oil or poor machine work. That has nothing to do with those parts and uber rods and a custom forged crank can't save an engine from owner and/or machinist negligence. My $.02
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I've seen stock rods run well over 600 whp reliably, and the only person who has ever managed to twist a stock crank is the fellow who built that rail dragster, IIRC he is pushing out over 1200 hp.
Check out Will Neely's writeup on how to build a high horsepower 7M over on http://www.7mpower.com and I think you'll have a really good idea of what needs to be replaced at what power levels.
Check out Will Neely's writeup on how to build a high horsepower 7M over on http://www.7mpower.com and I think you'll have a really good idea of what needs to be replaced at what power levels.
CTsupra
Supramania Contributor
A few CT Supra's have held 600rwhp+ on stock internals for quite a while, and these we're daily driven cars, dynoed often and tracked.
With that said, a few CT Supra guys have been through 5+ motors getting the tuning right to hold the power. It's all about the tuning.
With that said, a few CT Supra guys have been through 5+ motors getting the tuning right to hold the power. It's all about the tuning.
Problem no one mentioned is these engines are all over 12 years old and most over 100k miles. Of course you can't expect something to be reliable with big numbers after that much wear and more then likely not as well taken care of as it should have been.
7MGTEJoe said:
http://www.supraforums.com/forum/showthread.php?t=279816&highlight=death+spin
It happens. I'm not saying they're weak by any means, but If you're planning on 450rwhp or higher go with forged pistons. 600rwhp or higher and I'd strongly suggest aftermarket rods.
Again, people have and do go higher on stock components, but why risk it?
7MGTEJoe said:
Dr. Jonez has been making over 400whp for quite some time, and he's on a stock bottom end.
if dr. jonez taught me nothing else, he taught me that it's all in the tuning. if you can tune, your motor will last. (assuming everything was built correctly)
i believe he's around 450hp or so...
-shaeff
GrimJack said:
a bunch of those guys on the site making just over the required hp(450) are running stock bottom end...
do yourself a favor and give that guy a quick slap across the face for talking shit without doing the proper research... as gentle as possible while still taking away his dignity.
It is all in the tune, but there's not much room for error at that power level on the stock pistons. John Lunsford is making over 400 hp at the wheels on stock injectors and only using a Lexus AFM and an AFPR for tuning, but I wouldn't recommend that other people emulate him. John and Dr. Jones both know what they're doing, the average guy just getting into this stuff is learning as he goes. Forged pistons won't make a poor tune work well but it'll give your engine a better chance of surviving an error so you can correct it.
Thankfully, I am not so limted.IJ. said:Damn good post Joe!
You must spread some Reputation around before giving it to 7MGTEJoe again.
LOL no need to gloatGrimJack said:Thankfully, I am not so limted.
! You must spread some Reputation around before giving it to GrimJack again
I have been making well over 400rwhp for about 1.5 years. When I blew my metal headgasket running 24psi, I got a chance to inspect the top of my pistons and cylinder walls, and everything looked brand new still. 7M's are strong engines. The key is running plenty of race gas when pushing the engine with high boost. This will avoid killer detonation and compensate for tuning errors.
On my next turbo setup, I plan on running mid 500whp and have no intentions of getting aftermarket pistons and rods. Of course that will be acheived with a good concentration of C16 in the tank.
On my next turbo setup, I plan on running mid 500whp and have no intentions of getting aftermarket pistons and rods. Of course that will be acheived with a good concentration of C16 in the tank.
Adjuster
Supramania Contributor
Detonation and/or pre-ignition kills the motors.
Tuning is the key as noted by many.
Stronger forged stuff just gives you a wider margin for error, and can hold up to higher ultimate power levels when your state of tune is correct. (But will fail just as easy if your tune is wrong at those higher levels of power.)
Last night, a local stock block 7MGTE failed at the track. He has a larger T4 on a log manifold, external WG, and the 550/Lexus combo. Spiked boost to 23psi, and boom went his motor. I'm not sure what gas he was running, but he talked about getting some 100 octane before the race, so I'm assuming he had that in there.
AF's were 11.8:1. He's not sure why it died, but now is blowing oil out the tail pipe bigtime.
My guess is the stock pistons failed, a ring land is either broken or melted, and possibly a top ring cracked or missing. (Think out the exhaust at high speed, into a spinning turbo... Ouch.)
I fried a #6 piston ring land at about 28psi of boost, also at AF's in the 11's. Simple formula appears here.
Too much boost, not enough fuel, and too much spark advance on stock pistons and they die. I'm starting to think AF's in the 10 or richer range for high boost is a good idea. Also pulling 5 degrees of advance from your base setup so it's not there at high boost is a good idea too. (I can add it back with the Emanage everywhere the engine is not under pressure.)
So, in response to your question about the engine being strong. Sure it's stronger than most, but nothing is "bulletproof".
BTW, I've had a crank twisted. Fully built stroker motor, was not hooked up right, and the guy at the shop took it out for a ride. (No boost controller hooked up, no fuel pressure regulator hooked up.) He tells me "your car is damn fast, runs like a raped ape." I start the car, and it's knocking already, shop says that's piston slap... Also the state of tune is totally wrong. TPS is out of adjustment, most of my gauges don't work. Boost spikes past 20. After 4 hours of chasing down problems, I get it to hold steady boost at 20, but 350 miles later, it dies of a twisted crank, and the subsuqent wiped out bearings. 2100.00 later, the motor is running again. (New block this time with 4k clearance on the pistons v/s the 6k that ROSS says is right.) Shop is not allowed to test drive the car, and the guy who did, is no longer at that shop.
If your going for ultimate power, be carefull, or be prepared to spend.
Tuning is the key as noted by many.
Stronger forged stuff just gives you a wider margin for error, and can hold up to higher ultimate power levels when your state of tune is correct. (But will fail just as easy if your tune is wrong at those higher levels of power.)
Last night, a local stock block 7MGTE failed at the track. He has a larger T4 on a log manifold, external WG, and the 550/Lexus combo. Spiked boost to 23psi, and boom went his motor. I'm not sure what gas he was running, but he talked about getting some 100 octane before the race, so I'm assuming he had that in there.
AF's were 11.8:1. He's not sure why it died, but now is blowing oil out the tail pipe bigtime.
My guess is the stock pistons failed, a ring land is either broken or melted, and possibly a top ring cracked or missing. (Think out the exhaust at high speed, into a spinning turbo... Ouch.)
I fried a #6 piston ring land at about 28psi of boost, also at AF's in the 11's. Simple formula appears here.
Too much boost, not enough fuel, and too much spark advance on stock pistons and they die. I'm starting to think AF's in the 10 or richer range for high boost is a good idea. Also pulling 5 degrees of advance from your base setup so it's not there at high boost is a good idea too. (I can add it back with the Emanage everywhere the engine is not under pressure.)
So, in response to your question about the engine being strong. Sure it's stronger than most, but nothing is "bulletproof".
BTW, I've had a crank twisted. Fully built stroker motor, was not hooked up right, and the guy at the shop took it out for a ride. (No boost controller hooked up, no fuel pressure regulator hooked up.) He tells me "your car is damn fast, runs like a raped ape." I start the car, and it's knocking already, shop says that's piston slap... Also the state of tune is totally wrong. TPS is out of adjustment, most of my gauges don't work. Boost spikes past 20. After 4 hours of chasing down problems, I get it to hold steady boost at 20, but 350 miles later, it dies of a twisted crank, and the subsuqent wiped out bearings. 2100.00 later, the motor is running again. (New block this time with 4k clearance on the pistons v/s the 6k that ROSS says is right.) Shop is not allowed to test drive the car, and the guy who did, is no longer at that shop.
If your going for ultimate power, be carefull, or be prepared to spend.