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those running 10.5 wiseco hds

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9412tsi

Proven Member
53
2
Dec 1, 2014
pittsburgh, Pennsylvania
So my machine shop called me telling they are almost done with all machine work. I had him figure out the compression ratio so we can figure out what size gasket to use. Im gonna be running o-ring setup with copper hg. He said he did the math its coming out with a 11.5 compression ratio. He took .004" of block and same of the head. being this engine only had 35k miles and it never looked like it was apart, im assuming this is the first time it was machined.Why is the ratio so high?you would think wiseco would be a lot closer?Also he said the pistons will be sticking out .010" over the deck. He said we are gonna have to use a .085" ish gasket to get 10.5:1.

so my questions:

is this normal for them to be off by a whole point?i was expecting .2-.3 over or under.

can I get away with 11.0:-11.5:1 on e85? I know tuning will be the key here.basicly, will that high of compression limit me?

I m just wondering what the mls guys are doing when using these pistons.

thanks in advance...
 
Right but is there a point e85 will detonate?im sure there are many variables, just don't wanna push my luck here.maybe most people don't calculate compression?
 
hmmm....really need to look into this more...last time I was modding cars was like 10 years ago where 10.0:1 compression on a b series Honda meant you had to run low boost.of course no e85 back then.hell I never ran meth either...

maybe I should just shoot for 11.0:1
 
Something in the math is wrong.

If the pistons are .010 above the deck, the block has been decked more than .004 or the wrist pin height is wrong in the piston or the center to center is off on the rod.

If the head was milled .004 head thickness should be 5.196-5.198 and around a 46.5cc
 
Yes there are a lot of variables here. Will this be for E85 only? If so, 11:1 will be just fine. What turbo & fmic and what is your boost target (psi)? E85 quality can vary from pump to pump and time of year but it's generally very detonation resistant. Make sure you have a good tune and a fuel sys to get you to your goal.
 
He cc'd the head at 43cc's.he did say the specs he saw for this head should of been 46-47 cc's.makes no sense the head limit pads had plenty of depth to them like its never been cut before.i do have new super tech valves.clearly my head is giving me this high comp.this is strictly e85 build, will be running 10.5 inch ets IC with FIC2150's and flex fuel sensor.will "break it in" with an fp black and eventualy move on to 6466 or similar sized turbo.hoping to eventualy achive 750awhp.
 
looks like I have to call wiseco tomorrow, to find out if these pistons should stick out or not...
 
Hope you get the machining issue sorted.

From my past reading on the subject your compression ratio is considered mild by most reputable builders so there shouldn’t be anything to worry about if you end up in that range. My understanding is that 750hp is the limit on those pistons due to lack of skirt area/ring support. E85 is pretty amazing and allows for a lot of boost and timing but this greatly increases cylinder pressure, some have reported accelerated wear and blowby when pushing the HDs. Sounds like you have a solid setup and remember it’s all in the tune…some people get too aggressive with the timing they can get away with on E85 trying to hit a certain number and this is really hard on parts, really in any case.
 
He cc'd the head at 43cc's.he did say the specs he saw for this head should of been 46-47 cc's.makes no sense the head limit pads had plenty of depth to them like its never been cut before.i do have new super tech valves.clearly my head is giving me this high comp.this is strictly e85 build, will be running 10.5 inch ets IC with FIC2150's and flex fuel sensor.will "break it in" with an fp black and eventualy move on to 6466 or similar sized turbo.hoping to eventualy achive 750awhp.
Nice man, I'll ne moving on to e85 when i move to arizona, ive got 6466 it's a nice turbo.
 
If your going to be only on e85, higher compression is actually preferred, youll have trouble on pump, but e85 only your just fine.

Its a colder burn thats why the higher compression helps, i can't reallu speak to your setup specifically. But i am in regard to higher compression around 12:1+ helps for a more efficient burn of the ethanol.
OT, but no, thats not how any of this works. The flame temperature of Ethanol isn't that much different than gasoline, furthermore the flame temperature in an engine is more effected by the equivalency ratio, residual gas fraction, and about 9 million other things, than the fuel type.

All fuels make more power with more compression, to the point of detonation. There isn't a fuel that likes more compression than others, all fuels respond the same way, more compression = faster flame speed = increased thermal efficiency. The ethanol works with higher compression ratio because of it's greater heat of vaporization, and its higher flashpoint, means it fights pre-ignition and detonation better.

On a 4g, all your doing with higher compression is compromising head gasket life for a small increase is power.

Anyway op, it sounds like something is super janky with your parts and or your builder. Never compromise your quench to lower your compression.
 
Great points. You don't want to use a thicker headgasket for what was taken off (block or head) doing so increases the quench volume. Make sure nothing has exceeded its service limit. Most of the time with a 4g you end up with negative deck height...with zero being ideal. The machine shop may deck the block or machine the pistons to achieve zero. They also take into account piston to valve clearance with your combination of parts. Let us know what you find and double check/inspect what they do.
 
He cc'd the head at 43cc's.he did say the specs he saw for this head should of been 46-47 cc's.makes no sense the head limit pads had plenty of depth to them like its never been cut before.i do have new super tech valves.clearly my head is giving me this high comp.this is strictly e85 build, will be running 10.5 inch ets IC with FIC2150's and flex fuel sensor.will "break it in" with an fp black and eventualy move on to 6466 or similar sized turbo.hoping to eventualy achive 750awhp.

First, there is no such thing as head limit pads, That is just some urban legend or wives tail. That is just BS spread by those who do not know.

They are injection points from when the head was cast.

Now measure the head,
http://www.dsmtuners.com/threads/how-to-measure-a-4g63-for-cylinder-head-for-thickness.413757/

From what he CC'ed Ill guess the head is about 5.170

I will also guess that you are running Wiseco Pistons K662M85XXAP for the 10.5:1 CR
With a 1.378 compression height

So if the pistons were miss machined, the compression height would be around 1.388 to get the pistons .010 out the hole.

If only .004 was ever milled off the block, the pistons would be .001-.002 out of the hole.

Wiseco claims a "0" deck on the pistons.

Block deck height is 9.015 tall.

If you measure from the main cap mating surface to the HG surface, I will guess yet again, that your block height is about 9.005

I do not know what brand of rods you have, but I would have to say some sort of aftermarket with a 5.906 (150 mm) C2C

I can understand if things were off a .001 here or there, wrist pin bore or rod C2C

Or if the rod throws were even off set ground by .010

Overall the aftermarket has decent quality control, and doubt a part making it out the factory that was off by .010

I think your assumption that your virgin, never machined block and head is not correct.

The fit is just simpler that the block and head have been machined before.

Another bit of reading for you.
http://www.dsmtuners.com/threads/how-to-figure-compression-ratio.468895/
 
Very strong info in this thread, I really appreciate it. I will do all of my own measuring, as I will be putting this thing together. He said he is estimating the pistons would stick out .010", but with out assembly we will not know for sure.i am running manley turbo tuff rods.i forgot to mention I have 1mm oversized valves.is that good for 3cc?wouldnt think so. i know the "limit pads" are not really limit pads but its a good indication. That head had plenty left.


At this point im kicking my ass for not measuring head thickness and deck height. I went through this trouble when I built my 7mgte, i couldnt find a virgin head to save my life (imagine that).

im hoping its just a miscalculation on his part.he builds race engines for a living, i wasn't gonna question it.if its a mistake it is what it is, we are all human.


either way if 11.5 is ok and my piston to valve clears out, ill run it as that.i found other info when i ran the piston number and they spec them at closer to 10.7:1.
 
he did mention cutting he pistons down if I absolutely wanted 10.5:1. best thing to do like mentioned is assemble an verify measurements.again, thanks for the awesome info.
 
will have to read that whole thread after work, thanks.

he did say he said the new valves in at stock height.
 
Since there are so many of the smart guys that answered my questions back in September, I figured I will post back in here.

I finally got some of the tools in order to help me blueprint this bottom end. I bought a fowler dial bore gauge , a micrometer set and 0-1" ball end micrometer for the bearings. All micrometers calibrated. Comparing measurements I took with measurements on service info and from other people online they do seem accurate to .0001" .I was pretty happy considering what I spent. here are my measurements for my main bearing clearances:

mains: 2.2435-2.2433-2.2435-2.2433-2.2434

acl tri metal bearings, "H" std all measured to .0782"

so I took .0782 x 2 then added my smallest main 2.2433 and set my micrometer to that . I then zeroed out the dial bore gauge and measured my mains (with kiggly griddle torqued down, mains where line honed).

I ended up with .0036" main bearing clearance .I was hoping to be closer to .0025"

So my question is, is this acceptable clearance? I know the book says .004" max.

These acl's are thinner than my original bearings. I measured the originals at .0004" thicker per half. the crank did get polished.im assuming polishing could possibly take .0001-2" of the crank, so I possibly have .001" extra clearance with these acl's. I would expect that from the hx's but no the H.

any suggestions? run as is or pick up a set of oem?just run 20w40? I suspect going oem will put me in the .0026-8 " range.

Also, is this an acceptable way to measure? I didn't wanna risk of installing bearing and scratching them with my bore gauge.

I will end up running a 6466 im pretty sure, so this engine could possibly see 750-800awhp a couple years from now....

I measured out my ptw clearance at .0045-7" so im pretty happy with that.
 
ok I feel pretty stupid but after some searching around it seemed that .0036" was excessive so I decided to plastigauge the mains and make sure I was close to what I was measuring.it ended up showing under .003" which made me realize I fudged up the bore gauge reading.long story short I must of set up the micrometer .001" off because I re did everything and ended up with .0024 -.0026" which agrees with most results ive seen people get. I should of double checked yesterday but we live and we learn.
 
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