Stock B20VTEC, danger inTorquing ARP ROD BOLTS and Revving to 8000rpm on stok block

**JS2k** · 23-08-2010 10:53 PM

Originally Posted by tinkerbell

well, right here:

got a dictionary handy?

A S S U R E

http://dictionary.reference.com/browse/assure

T E S T

http://dictionary.reference.com/browse/test

E X T R E M E

http://dictionary.reference.com/browse/extreme

so yeah, whatever, and particularly in the context of a B20/VTEC hybrid engine - maybe you just need to keep in check your use of words? which might be easily misinterpreted?

Mate please, were talking engines here

if you want to give english lessons do it elsewhere

After all this is a forum , people can voice there opinions and experiences to help others if possible

We all build engines differently thats will always be the case, if ARP rod bolts will keep you happy and give you the peace of mind you need then have them fitted

Best of luck

**tinkerbell** · 23-08-2010 10:56 PM

Originally Posted by JS2k

Mate please, were talking engines here

so what did the last B20/VTEC you built get used for? drag racing or circuit racing?

**JS2k** · 23-08-2010 11:11 PM

Originally Posted by Chr1s

Well, this is a forum and everybody is open to an opinion, so here's mine.

In a forced induction motor, you have a condition where the engine is always under positive pressure. In a naturally aspirated engine, we often find a vacuum or an atmospheric condition present depending on how efficient the motor is.

So what? Well think of the process the rods and rod bolts see, the changing ingress of stresses is what i'm talking about in particular; Tension and compression.

Compression occurs when the piston is "pushing" down on the rod, this induces stress in the rod near the wrist pin, this kind of stress will lead to a bending type of failure. There is no stress on the rod bolts at this point, if anything, this is where the importance of oil pressure between the bearing and journal is needed to avoid contact. For an increase in BMEP (power) there is the requirement for an increase in oil pressure. But this is another story.

Tension occurs as the piston is "pulling" on the rod and peaks in stress when the crank changes direction, imagine sprinting as fast as you can and then stopping and trying to change direction as fast as you can, the inertia would be huge. As mentioned earlier, a failure at this point would typically yield a rod split in two. What has rod bolts got to do with this stress? Well when the rod is under tensile stress, the bottom half of the rod cap is resisting this force due to the oil pressure again between the bearing and the journal. This resistant force is transmitted to the rod bolts which results in, you guessed it, tensile stress. Now we've realised that this kind of motion isn't present on the compression stroke, hence the term compression, the rod is subject to compressive stress, when the power stroke is occuring, the compressive stress is releived and the rod is in a happy state, so this rules HP out of the equation for stresses implied on rod bolts. Obviously the rod has to have a suitable second moment of inertia to sustain large compressive stresses. Although I will guarantee you that the tensile stress acting on the rod is much greater than the compressive.

It should be common sense now to see how a rod is affected now by the greater pressure differential as it sweeps from TDC on the intake stroke (overlap, MAP, tensile) in a naturally aspirated motor.

Why HP has nothing to do with how strong a rod bolt is? Because the tensile stress present on the rod bolt is what kills them, and the faster you spin the engine, the greater this becomes. THIS is why I say, RPM kills rod bolts.

Generally speaking, higher HP engines require a greater RPM to make this higher HP, this is why items fail in this manner and people just resort to "oh it's because of the power" mentality. Remember your simple Physics.

Oh by the way, you may have been building engines for the past 15 years, which no offense, means jack all to most educated people, although keep in mind you might be talking to an ex F1 engine developer one day.

Chris

You make some good points there, let me add some

There is large amounts of torsional forces on the connecting rod , the con rod itself would be safe unless were talking about forced induction

The conrod bolts and cap will have most pressure, although the concern i would have is stretching of the bolts rather than the bolts snapping

Stress fractures can also be a concern, if the engine was not assembled correctly and torque specs and procedures were not followed you could induce a problem early on in the assembly process

As i mentioned earlier we all have different opinions and ways we build our engines, FYI i have used ARP rod bolts, stud kits and gurdle kits before with great success

Well i guess we cant argue with an EX Formula 1 engine developer either, although that also means jack to most people

Best of luck to all, i have added my opinions

Lets move on gents

**TODA AU** · 23-08-2010 11:38 PM

Originally Posted by Chr1s

Well, this is a forum and everybody is open to an opinion, so here's mine.

Originally Posted by Chr1s

if anything, this is where the importance of oil pressure between the bearing and journal is needed to avoid contact. For an increase in BMEP (power) there is the requirement for an increase in oil pressure. But this is another story.

Oh by the way, you may have been building engines for the past 15 years, which no offense, means jack all to most educated people, although keep in mind you might be talking to an ex F1 engine developer one day.

So do I get you call you an Ex F1 engine developer when you work for a team for 1 week & get fired? LOL…

Also, bearings are filled by oil pressure on the unloaded side…
That is oil is pumped where the load was…
Anyway… I’ll leave it as this could digress so quickly…