Built engine. How hard is it?

[Tcoat]

Originally Posted by mrspindlelegs

Because rod failure has not been a problem with the naturally aspirated engine that they install from the factory. We are on our own when it comes to the engine being reliable under boost.

Keeping in mind that many of the FI failures were more related to improper tuning than actual parts failure.

Originally Posted by 15limited

It would seem from the two pictures given this was only from an OEM NA perspective, and I believe gtengr was talking from a FI standpoint.

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Any durability improvement that impacts NA will increase the reliability of FI as well.

[Jo0]

True, I'm still in the line of thinking of "why not both" when it came to the decision of improving the rods/pistons.

Either way any improvement is welcome.

[x808drifter]

Originally Posted by Tcoat

The rods may have been the failure point but that does not mean they were the root cause. The piston heads may have been warping causing the rods to fail or even the block may have been letting the crank twist under power which again could cause the rods to fail. (these are just examples of what COULD have been the root cause I am not saying either is remotely true since I am not privy to their FMEA engineering reports). The parts that fail in a mechanical system are not always the ones at fault. In fact, it has been my experience, that the parts that fail are very rarely the cause.

Case in point: Piston rings that haven't been filed to allow for expansion from the added heat introduced with FI/Nitrious.

Ring gap isn't big enough, ring expands and buckles against itself, excess pressure pushes on ring land cracking the piston.

[Tcoat]

Originally Posted by Jo0

True, I'm still in the line of thinking of "why not both" when it came to the decision of improving the rods/pistons.

Either way any improvement is welcome.

Every change costs money. They don't change what ain't broke. They obviously determined the rods were fine so no change was made.

[Darth Khan]

Originally Posted by Tcoat

Don't have the document available here but when home tonight I will pull up what was done and why. The pictures are very informative.


Edit:
I found a work around!
The critical high stress sections of the block were reinforced a the pistons hardened. I would say that in tock form the 17 engine will take moderate FI much better that the old ones. Doubt there would need to be much building required for a street car.

Interesting it seems the changes were done to support the huge 5 hp gained in the manual engine. (Which I believe comes from some basic intake/exhaust upgrades)

I'm surprised the heat, stress and load tolerances were that close. Makes me think that even basic F.I. boosts without appropriate piston and rod upgrades are not such a good idea.

[15limited]

Originally Posted by Darth Khan

Interesting it seems the changes were done to support the huge 5 hp gained in the manual engine. (Which I believe comes from some basic intake/exhaust upgrades)

I'm surprised the heat, stress and load tolerances were that close. Makes me think that even basic F.I. boosts without appropriate piston and rod upgrades are not such a good idea.

I think despite manufactures claims there was much more than 5 whp gained in 17' MY, and I believe the increased output was almost entirely from the intake mani and tuning.

Well, the FI section has dozens upon dozens of people reliably running every type of FI kit out there on stock engines so...

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[Darth Khan]

Originally Posted by 15limited

I think despite manufactures claims there was much more than 5 whp gained in 17' MY, and I believe the increased output was almost entirely from the intake mani and tuning.

Well, the FI section has dozens upon dozens of people reliably running every type of FI kit out there on stock engines so...

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True and of all the cars we can choose to boost a Twin seems to be designed for it. However the money and effort for the upgrades to the block with such a small HP increase does make me wonder.

I have always tried to stick with facts. The fact that this forum has a few dozen F.I. upgrades which on the surface has no problems is not an ideal baseline, there are too many variables for such a small data set. There is also a number of F.I. installs on here that has caused major engine failures. But again the data set is too small to draw any real conclusions. (Plus there is also the obvious racer driver/owner factor).

Having said all of this i am currently not in the market for a F.I. upgrade and in no way think individuals should not upgrade. I am simply curios about the thought processes and facts when deciding to go F.I. Never know in a few years when my warranty has expired I may get another D.D. and try it for fun.

[Tcoat]

Originally Posted by Darth Khan

Interesting it seems the changes were done to support the huge 5 hp gained in the manual engine. (Which I believe comes from some basic intake/exhaust upgrades)

I'm surprised the heat, stress and load tolerances were that close. Makes me think that even basic F.I. boosts without appropriate piston and rod upgrades are not such a good idea.

I doubt the tolerances were that close to start with. There would have been a considerable safety margin. The new changes just increase that safety margin even more to account for the increases in power and torque.

Originally Posted by 15limited

I think despite manufactures claims there was much more than 5 whp gained in 17' MY, and I believe the increased output was almost entirely from the intake mani and tuning.

Well, the FI section has dozens upon dozens of people reliably running every type of FI kit out there on stock engines so...

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Yes there are many more people running moderate boost with no issues than those that blew things up. If you look closely at the ones that did have issues more of them were related to over boost or tuning than any other cause. You can safely boost with stock parts but you tune the fuel mix or timing wrong and things are going to break. Making the parts that broke stronger doesn't fix the problem it just moves it to the next link.

[mrg666]

Originally Posted by 15limited

I think despite manufactures claims there was much more than 5 whp gained in 17' MY, and I believe the increased output was almost entirely from the intake mani and tuning.

Well, the FI section has dozens upon dozens of people reliably running every type of FI kit out there on stock engines so...

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Why would they specify 5hp gain if it is more than that? Some (if not most) of the perceived performance gain in '17 models is not really power increase but an effect of change in final drive ratio. But this has its shortcoming, they will probably be faster on the start but fall short at the end of stretch.

I agree. My impression is that most of the FI fails are due to random mods stacked on top of each other, such as flex fuel, replaced injectors, aftermarket headers (increased heat), high boost pulley on stock engine, etc. or improperly rebuilt engines. I am knocking on wood for my JRSC engine, but this is my impression.

[86 South Africa]

Originally Posted by gtengr

Depends on the hp goals. I would do pistons, rods, and all bearings at a minimum. Buying the hardware is the easy part, who will be putting it together and checking all clearances is the most important question.

Just thinking about it... and learning in the process...

Could I simply change the rods?
Those are widely considered to be the weakest part of the engine and my thinking is with a modest FI setup I don’t need a huge amount of extras.
I’m just wondering about say a 300hp car (give or take).

[86 South Africa]

Originally Posted by mrg666

Why would they specify 5hp gain if it is more than that? Some (if not most) of the perceived performance gain in '17 models is not really power increase but an effect of change in final drive ratio. But this has its shortcoming, they will probably be faster on the start but fall short at the end of stretch.

I agree. My impression is that most of the FI fails are due to random mods stacked on top of each other, such as flex fuel, replaced injectors, aftermarket headers (increased heat), high boost pulley on stock engine, etc. or improperly rebuilt engines. I am knocking on wood for my JRSC engine, but this is my impression.

Big part of my FI was using Delicious for the tune and my local guy has done a few cars with the same headers and sprintex 210 kit I’m getting... so he’s seen the common issues already and knows how to avoid them or fix them if they do happen.

[Deep Six]

Ok, I'm a car company selling a sports car that has been dogged by the general population because it's perceived to be underpowered. Now I modify the motor to gain 25 more crank horsepower and I choose to keep it a secret???? Not exactly marketing genius.


I would bet that the revisions to the block design resulted from the data they had servicing 13-16 models, a 5hp bump does not warrant the change on its own.

[steve99]

Post here from moto mike (mote east tuning)


fuel in south Africa (petrol ) will be an issue 95 ron is best you have ?? , your probably best sticking to E85 if available with boost


http://www.ft86club.com/forums/showt...=98839&page=21

[gtengr]

Originally Posted by 86 South Africa

Could I simply change the rods?
Those are widely considered to be the weakest part of the engine and my thinking is with a modest FI setup I don’t need a huge amount of extras.
I’m just wondering about say a 300hp car (give or take).

I haven't built an engine yet, but I don't see why not. You'll still probably want to re-ring and hone the cylinder, and will need to meticulously measure all clearances related to the aftermarket rod's connection to the the stock piston. Then there is balancing everything for the new aftermarket rod's weight. But that is all happening with stock or aftermarket pistons so I wouldn't say any of that is "extra" labor. Assuming no big surprises when putting it together, the $ savings should be the cost of aftermarket pistons minus the cost to re-ring the stock piston.