phillyb

iTrader: (8)

whew...trying to wrap my head around all this...
mine are wiseco 83.5mm 8.5-8.8:1 forged pistons.
i didn't see a sheet with tolerances in the box.

dgmorr

iTrader: (4)

Smooth right?

Just wondering for the DIY types. You see a lot of DIY budget builds with no mention of matching them.

BogusSVO

iTrader: (1)

Phillb From all the forged pistons I have seen, over 90% fall in the .003-.004, that includes Diamond, Wiseco, CP, JE.

Measure your skirt 90* to the wrist pin and see where they mic out. That will tell the tail.

Std bore + over bore - Piston measurement = PTW

dgmorr... the reason the DIY types do not weight match for the most part is they do not know that they should.

That is why I do these How tos/write ups, so the guys wanting to build an engine can do a bit better.

NiklasFalk

iTrader: (1)

Good to know when the crowns look like this...

Btw, any "smart" reason ST have lowered the outer edge 0.15mm?
For boosted apps trying to save the head gasket maybe...
In my 11:1 N/A application is just make the squish worse.
The compression height was also a good 0.5mm lower than stock (block decked 0.7mm to get the squish flush (and the lowered edge 0.15mm lower).

BogusSVO

iTrader: (1)

Niklas... so on yor dome piston the outer edge was dropped .006

The only reason I can think of to do that would be to give the flame front a path around the dome to help with air/fuel ignition.

Why the wrist pin was moved, I honestly can not say.

What part number are you working with?

NiklasFalk

iTrader: (1)

"P4-M84-P10" according to their catalogue (84mm 11:1).

BogusSVO

iTrader: (1)

Well from what I can see posted on the website your compression height should be 1.201, the same as most of the others except PN# P4-MA84-CR9

And looks like a slight adjustment to increase the compression of the 8.6:1 piston

If the center line of the wrist pin to the crown flat does not measure out at that number, then they were machined wrong and should be sent back.

So if they are .50mm/.020 shorter then you shold see, 1.201 - .020 = 1.181

Savington

iTrader: (31)

I am the proud owner of that piston. In addition to the rather obvious ringland damage, the center of that piston is dented straight down, presumably from preignition. (The root cause was determined to be inadequate intercooling.)

Here's what a normal 8.6:1 Supertech looks like:



Here's that one:



Complaining about how that piston failed at the sharp edges near the valve reliefs is like regretting the flammability of your polyester shirt while standing a few feet from the center of a military nuclear strike.

BogusSVO

iTrader: (1)

Sav... What were your AFRs when you did that?

I am impressed!

I would have said the dent in the crown came from high cylinder temps, for the simple reason that there is no splatter that is normaly seen with pre det. Like burning a hole in the center of the piston.

But no doubt you were getting ready to melt the center out of that slug.

A failed piston is a failed piston.

And for those who do not know, for every 1* drop in air inlet temps you drop 3* on the EGT

Savington

iTrader: (31)

AFRs were ~11.5 give or take a couple of tenths. 100 octane. The failure happened at ACS Roval, so we were doing ~1:47 laps with about 35 continuous seconds of WOT in 5th and 6th per lap. Too much boost (21-22psi), too little intercooler for the conditions.

That was 2+ years ago as well. Lots has changed about the car since then (more injector, E85, different intake manifold/head, WAY more intercooler, less boost, more power).

BogusSVO

iTrader: (1)

I bet the move from gas to E85 gave the power curve a good raise.

Also you would have to about double the size of the injectors with the E85 set up

Did you ever take readings of the temp drop with the old IC and the new?

Savington

iTrader: (31)

10% gain going from gas to E85 at the same boost level with no timing changes - 300whp at 14psi to 330whp at 14psi. All I did was add 20% to the fuel map and turn up the base pressure. Small timing/fuel changes were worth another 5whp, and the car ended up making 351whp at 17psi. That's all on an 8.6:1 motor - the next motor will get 11:1 pistons and a pile of boost.

The fuel setup is a Bosch 255HP, ID1000s@70psi of base pressure and a 1:1 boost reference. It's not quite as bad as double - the stoich ratio is 47% richer than gas, so I typically say gas x 1.5 for E85 fuel requirements to be on the safe side. Based on my math, this pump/injector setup will get me to ~425whp, and then I'll need to knock the base pressure up to ~90psi and run a dual-pump setup (likely a DW300 in the tank acting as a lift pump with a Bosch 044 in-line for pressure).

I never did get readings from the old (ebay core) to the new (Precision 600hp). With the new, in 100*F ambient temps, the IATs will fluctuate between 120*F and 130*F depending on the amount of time spent on throttle in 5th/6th. That's good enough for me.

BogusSVO

iTrader: (1)

Damn, The Id1000 are some nice injectors, I just read up on them a bit.

Flow 1015cc @43 psi

so you should be pushing them just around 1300 cc @ 70 psi
at 90psi that works out to almost 1500cc

I wonder what the fuel temps are at when racing.
How much head is being transfred to the fuel, and the heat from running thu the fuel lines.

Seems to me this would "thin out" the fuel being used

I can see a set up like that for drag, but not road racing.

What duty cycle are you sitting at?

Why not get some injectors in the 1500cc range and back down the fuel pressure?

BogusSVO

iTrader: (1)

Savington

iTrader: (31)

I lost all my logs long ago (haven't touched the tune on that car in ~2 years) but based on the map it's about 11ms actual PW (calc+dead) at redline, which works out to ~70% duty cycle at 7400rpm.

ID doesn't make an injector between 1000 and 2000cc, and the 2000cc/min units are close to $1000 for a set of 4. I don't need much more than what I have now - the boost levels to make 500whp on this motor will be close to 30psi so all I really need is a pump set that can move 1100-1200cc/min at ~100psi of rail pressure - no big deal

BogusSVO

iTrader: (1)

Savington, I will admit you knowlage of fuel systems is beyond me.

elesjuan

iTrader: (11)

Wouldn't it be fairly easy to add a second set of injectors on the bottom of your IM? If you're running 1kcc/min primary add a secondary 440cc? Not really sure what ECU you're running so that could be a roadblock..

falcon

iTrader: (13)

Sav's our local guru. Tends to know pretty much everything about everything. And he has the most badass turbo'd BP here.

Savington

iTrader: (31)

The series 1 AEM has enough spare injector drivers to do that, and the software will blend them properly, but that's a lot of extra failure points and similar cost (the injectors, plus the rail, plus fittings, etc) to adding an inline 044 to my current setup and spinning the FPR screw in a bit more.

Just don't ask me to bore my own engine block

elesjuan

iTrader: (11)

See, that's why I'm not an engineer- I tend to forget looking at ALL aspects of doing something. Adding more points of failure was never something I would've considered. Sounds like you've got a much more reliable plan!