10 replies to this topic

[smiley]

Just thought i would mention it, as not many experence near this power levels yet.

Peter (obdtuner) with his turbo setup on 430bhp/550nm cracked one of his oem liners.

 

[oakmere]

So 400 looks to be the safe limit. Are the SC conversion more sympathetic due to the smooth delivery and lower torque?

[smiley]

That is the million dollar question.

 

[FLD]

I imagine it's down to cylinder pressures hence the first build book using bates liners with additional head sealing. It'd need someone to work out the pressures to say if sc is easier on the bottom end than a turbo. Did this engine have any overbore? A plus size piston won't help the liners at all

[slindborg]

yer parasitic loads are higher on the S/C'd engines due to the way the boost is created, so when one looks at the wheel powers, then a like for like turbo vs S/C would see higher BMEP's in the S/C.

 

But I'd imagine pressure isnt the only part in the puzzle. And I honestly thinkg the first build book was pretty conservative for some parts, as we all know how badly liners can move, so they probalby went with a sensible approach of at double OEM figures, peg the block etc. Plus iirc they were testing with Nitrous to find the breaking point, which is a total bellend to components

[vocky]

I have seen a Harrop SC with a cracked liner and he (Evocarlos) used a new b207 block too. 

[Nev]

I would imagine Peter has mapped his very well, so peak torque is not a peak.

 

Perhaps what you chaps need to use is a nice sturdy Z20LET block!

 

Or better still a B204 or B234 engine, one of the strongest mass produced doner 4 pots I've heard of, and really really cheap.

Edited by Nev, 12 September 2017 - 04:18 PM.

[CHILL Gone DUTCH]

I'm glad I keep mine nice and conservative at 350 whp Never felt the need for more Big 3.1 pulley FTW on harrop How ever I do have a map which is over 425 but leave that on the laptop

[FLD]

I suspect the top of the cylinder is the issue, high pressures, head lifts enough to leave cylinder unsupported but not enough for hgf and it breaks out. This is likely why a deck plate, gen 3 block or location ring (darton) are often used. Better head studs are often neglected and I'm meaning better than the arp replacement for oem. I'm meaning the 1/2 in version. Just my opinion of course.

[Exmantaa]

I suspect the top of the cylinder is the issue, high pressures, head lifts enough to leave cylinder unsupported but not enough for hgf and it breaks out. This is likely why a deck plate, gen 3 block or location ring (darton) are often used. Better head studs are often neglected and I'm meaning better than the arp replacement for oem. I'm meaning the 1/2 in version. Just my opinion of course.

 

Think you're on the money there. Have to read that back, but GM racing used metal O-rings between the head/cilinders + stronger studs...

[Mattyboi]

I suspect the top of the cylinder is the issue, high pressures, head lifts enough to leave cylinder unsupported but not enough for hgf and it breaks out.

This makes sense but i'd expect to see some signs of fretting on the top face of the HG or some sign of combustion leak on the head. A dark mark on the head thats extended from the main combustion markings, it would be tiny though.