4a block strength

[myne]

He is just a freak isnt he...He reminds me of the magic 8 ball -- You ask a question and always get an answer..

Top stuff stu.... Cant rep ya anymore though.


One thing im yet to find out is... If the bore was std on that block or not. If it was bored out that would make it a bit weaker to start with and more prone to splitting too.


The king of the 4a's Mr norwood never split a block in a 10,000 rpm, 40+ psi boost destroked 4agte. He was making something like 600+hp from 1.5L.
i have always wondered why he never split one and people running far less boost do ???

When i spoke to wil ( guy who's block that is) awhile back....I asked was it detonation that was killing the bore ?
He assured me the A/F was fine and it was just excessive cylinder pressure that did it.

So what are the general thoughts on this anyhow.... Worth it or stick with a std bore ?

Im skeptical...... and not sure if i like the idea yet. Unless there is something there that i cant see and dont know about holding the thing together....... Hmmmmmmmm

It's rather simple

He destroked it.
This makes the rod to stroke ratio of the 4a much more favourable and reduces sidewall loading significantly.
In essence, the longer the rod in relation to the stroke, the less angle the rod will lean on as it goes up and down, the less force will be applied sideways on the wall of the bore, the less likely you are to crank piston out the side.

I did some musing on this ages ago - perhaps you want to look into a 7A block
http://www.toymods.net/forums/showthread.php?t=3654

I have to laugh at my final comment in the post - suits you to a tee 30psi 4agte ;D

"If you want to build an 11,000rpm screamer without going Formula atlantic or a mad 1.6 turbo with stupid boost, I guess that's the only time you might need this."

[30psi 4agte]

Lol /\/\/\/\ :d

[jeffro ra28]

This is the result of a split bore. Obviously it doesnt always happen like this, but under extreme conditions it may just end up this way. Sorta has the same affect as an oxy cutter. But its actually caused by a fine spray of water on a hot part. Maybe stu or someone will be able to explain how this happens. I know nowa days they are using fine spray jets of water to cut stuff. But yeah thats sorta what has happened here.

[fixeruperer]

ive seen worse without spitting a bore, even started to melt the rod 10:1 comp and 34psi and a bad tuner = meltage.

[Talasas]

Guys, this thread is one of the best reads I've had here in a long time. Some really good thinking going on here and so far every time I've said "what about x to get y?" someone has already gone through the discussion. This is fantastic.

I do have one question myself though, if one were to machine a new deck as mentioned, how would you fit it to the block? Would there still need to be some meat left around the edges so that the new deck is pressed in?

Also, without trying to stray off on a tangent, are these VW engine blocks that are CNC machined from a massive block of solid steel really strong then?

[jeffro ra28]

VW engine blocks?
We have one at work. but there cylinder bores are completely seperate to the case. The main part of the "block" houses the camshaft, lifters and crank. The cylinder bores are actually fitted, just like fitting a piston.

[rms]

This is the result of a split bore. Obviously it doesnt always happen like this, but under extreme conditions it may just end up this way. Sorta has the same affect as an oxy cutter. But its actually caused by a fine spray of water on a hot part. Maybe stu or someone will be able to explain how this happens. I know nowa days they are using fine spray jets of water to cut stuff. But yeah thats sorta what has happened here.

Classic overheating and detonation !

Nothing to do with water, only the lack of.

[terryo]

you can only deck a 4A or 7A block by about 1.5mm. scrap after that. de-stroking is only useful if you have a bottom end that can handle a lot of extra revs. that is certainly not a 7A. the billet 4A/7A cranks dont seem to be a problem but I've seen a few conventional ones fall apart with constant high revs. the lighter 86kw ones seem less of a problem

[DX20VT]

i want to know how hes splitting blocks!
i have NEVER heard of anyone doing that.
even on 400hp+ engines running 25+ psi.

Not sure if you remember the but was taliking to you ages ago about the Silver AE86 Enduro car.
They have split two block now at about 350hp @ 19 psi.
Have given up on the 4A now and gone turbo Altezza power.

[30psi 4agte]

[QUOTE=jeffro ra28]This is the result of a split bore. Obviously it doesnt always happen like this, but under extreme conditions it may just end up this way. Sorta has the same affect as an oxy cutter. But its actually caused by a fine spray of water on a hot part. Maybe stu or someone will be able to explain how this happens. I know nowa days they are using fine spray jets of water to cut stuff. But yeah thats sorta what has happened here.



[Quote]

Been there done that......... Except my STD GZE pistons survived.

[jeffro ra28]

Classic overheating and detonation !

Nothing to do with water, only the lack of.

Wrong, This is caused by water. Perhaps the photo's do not show enough detail.

The engine was actually on the dyno, with all EGT's and lambda being recorded. Im telling you. its caused by a fine spray of water. Neither the the chamber, valves or any other part of the cylinder showed any signs of detonation or heat. Only a split bore. If i could show you some better detailed photo's im sure you would agree.

[jeffro ra28]

Yeah thats looks nasty, however it also looks like that was in detonation. I just noticed the pitted metal around the valves. Does the missing metal look like the finish of an oxy cutter?

[30psi 4agte]

Yeah id say oxy for sure !! Its been torched .

Nasty stuff hey

[rms]

Wrong, This is caused by water. Perhaps the photo's do not show enough detail.

The engine was actually on the dyno, with all EGT's and lambda being recorded. Im telling you. its caused by a fine spray of water. Neither the the chamber, valves or any other part of the cylinder showed any signs of detonation or heat. Only a split bore. If i could show you some better detailed photo's im sure you would agree.

Can you answer a couple of questions?

Did water cause the scuffing on the skirt thrust or the top lands ?

What caused the scuffing ?

How do you get water at low pressure to enter the cyl with sufficient velocity, against combustion pressure ?

[jeffro ra28]

Way off topic now i know but wat the heck

No matter how much boost you can supply an engine, there is always going to be negative pressure in the cylinder at any one stage during its cycle. This is when the water at low pressure enters the cylinder. Why else would a BHG leave water in there?

I do beleive the water causes this scuffing. A combination of things can occur. Large amounts of water constantly cooling the piston not alowing it to expand to its operating temperature and desired piston-bore clearance, causing it to violently rock in the bore causing this scuffing on the skirts and the top ring lands, this is a common fact and something to look for when an engine is never allowd to reach full operating temprature. OR the fact that water has no lubrication properties and washes any oil from the bore, or diluting it causing it to lose its lubricating affect.

My main point is that the particular engine with the example piston was in did this whilst on the dyno. Every single cylinder EGT was constantly under watch and being recorded, non of which showed any signs of high temperatures, nor low temperatures(leanness can actually cause lower EGT's) .
Lambda readings were at a constant of 0.72 (wats this in A/F? i couldnt be bothered converting it).
Now if you actually got to see the result in fine detail in person, i think you would agree that it was actually a cutting affect it had. Not a lean, or detonation condition. Melting a piston tends to crack it, or melt it away.

I have also seen this happen to an exhaust valve. What caused it? I hairline crack forming in the exhaust port which sprayed water down ontop of the exhaust valve. Instantly cutting literally half the diameter of the head of the valve straight off. It had the same affect, look like you took to it with an oxy cutter. This is now twice i have seen this occur, both times what do you think was the ONLY primary variant? A water crack!

Now, look at the kerf on anything steel that has been cut with an oxy torch. Its not hard to realise the cutting finish that it leaves. I dare you to try and acheive this finish cutting aluminium. Its not possible, why? Because aluminium has an ignition temperature that is higher then its melting temperature. All you will acheive is a blob.


Which is why i suggest that this water cutting affect i am trying to explain gave it this look asif it had been cut with an oxy torch (if it were steel).

Combine this with the fact that the "CUT" part of the piston was directly in contact with the origin of the crack. If anything, the water spraying the piston would have helped prevent melting/detonation or leanliness.

Have i answered your questions???