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Old 08-09-2018, 06:38 AM   #1
tehnation
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Default Manley PTW?

I just got my manley pistons, turbo tuff heavy duty 99.5 std, I also have a bnr billet 20g, and bc stage 3 cams, aiming for 400-500awhp @ 8krpm. I was going to get a .003 ptw, but I was reading this post where this guy aims for 0.0025-0.0027. So I was just looking for some second opinions, or any info on the subject. Also trying to figure out which category of gapping I fall into with a 20g turbo!

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Last edited by tehnation; 08-09-2018 at 06:46 AM.
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Old 08-09-2018, 12:11 PM   #2
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Quote:
Originally Posted by tehnation View Post
I just got my manley pistons, turbo tuff heavy duty 99.5 std, I also have a bnr billet 20g, and bc stage 3 cams, aiming for 400-500awhp @ 8krpm. I was going to get a .003 ptw, but I was reading this post where this guy aims for 0.0025-0.0027. So I was just looking for some second opinions, or any info on the subject. Also trying to figure out which category of gapping I fall into with a 20g turbo!

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with a 20g?
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Old 08-09-2018, 01:04 PM   #3
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I think medium boost.
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Old 08-09-2018, 01:05 PM   #4
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u've never seen a 20g make hp?
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Old 08-09-2018, 06:12 PM   #5
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not 400-500
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Old 08-09-2018, 06:42 PM   #6
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theres a bunch of people on this forum who have done it and show dyno sheet numbers saying that a 20g can put out between 400-500awhp. don't know what to tell you, its been done...
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Old 08-09-2018, 09:24 PM   #7
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I would ask the tuner and machinist their opinion. Also, unless people are getting their bros to tweak the dyno readings, I really don't see any 20g making more than 350-ish at the wheels. My previous setup was a billet ball bearing 20g turbo and it made about 340whp, may have made a bit more if we could have ran more than 21psi but that's getting out of it's efficiency range from what I've read. Usually that size turbo is capable of about 400-425 horsepower at the crankshaft, by the time it gets sapped by the awd components, it's a good bit less.
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Old 08-09-2018, 09:48 PM   #8
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theres a bunch of people on this forum who have done it and show dyno sheet numbers saying that a 20g can put out between 400-500awhp. don't know what to tell you, its been done...
Are you on E85? Aftermarket cams?

Blouches 20G-XT boasts 470hp, but that's at the crank. Factor in a 20% (at best) drivetrain loss in a Subaru, you're looking at ~375whp.

JRTuned did a 2011 STi that made 495whp with a Cobb 20G....but that car had a set of GSC S2 cams...and was running E98 (476whp on E85) and obviously had the intake, injectors and heads to support that kind of airflow. If that car lost 20hp with a 13% decrease in ethanol, it's gonna be hard to make 400whp on 93 pump gas with best E10. Crank, yes, I can see those being crank numbers, but not wheel.
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Old 08-09-2018, 10:13 PM   #9
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I'm going with bigger cams, bc stage 3. I have 1000cc injectors atm, but injectors are easy to upgrade. I'm going to see what 93 gets me, and then try e85 if it's not enough.
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Old 08-09-2018, 10:16 PM   #10
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Quote:
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theres a bunch of people on this forum who have done it and show dyno sheet numbers saying that a 20g can put out between 400-500awhp. don't know what to tell you, its been done...
So your saying a 20g will make the same power as a gtx3076? Some how dont think so. You have to be careful about numbers they can be manufactured and can be flasified. Honestly I dont think you will be even close on e85 with a built heads, and btw I think your cams are goinf to be too big for that turbo unless you're thinking of reving it out to 9000 but your turbo wont make power is say past 7500
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Old 08-09-2018, 10:21 PM   #11
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I'm going to run it to 8k rpm.
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Old 08-09-2018, 10:37 PM   #12
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I have a 20g, and my block is in the shop, heads are already done... it's what I got, when I start tuning the car we will see where the cards fall and I'll upgrade whatever accordingly but for now this is it. Dropping off the pistons tomorrow and the longblock will be done by next week.

My end goal is 400-500awhp and I want to be able to hit 8krpm, it can flatten out after 7500 as long as its flat that's fine. So regardless of what I have atm or if you feel it's not enough, let's just assume they are!

I was originally just wanting to know more about ptw and gapping for manley pistons, sure I can just ask the machine shop but I still want to do my due diligence and research beforehand, and know why is all. I was planning for .003 but I read someone doing .0025-.0027.

If a 20g can't do it, juuuusst get a bigger turbo lol! It's not that serious of an issue! The issue is the ptw, and gapping!!! Lets focus people!
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Old 08-09-2018, 10:50 PM   #13
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Ptw and ring gaps need to be wider as you run at higher power levels, to prevent cylinder galling and worse as piston and ring temperatures rise and they expand. A natural result is slightly more blow by and a little more noise when they aren't completely warmed up and operating near their designed power range.

Another thing to consider is if you're running oem cylinder liners, at higher power levels there are a couple of weak spots around the liner than can crack. All it takes is a few hard detonations to push them to crack, be sure to keep knock to a minimum.
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Old 08-09-2018, 11:09 PM   #14
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Quote:
Originally Posted by tehnation View Post
I'm going with bigger cams, bc stage 3. I have 1000cc injectors atm, but injectors are easy to upgrade. I'm going to see what 93 gets me, and then try e85 if it's not enough.
Low 400's is possible in that case. My money would be on E85 to get them though. I'm interested to see the results with pump vs E85 with your setup.

Anyways, that's another thread....
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Old 08-09-2018, 11:27 PM   #15
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bigger cams are going to give me horsepower regardless of turbo. the valves are open longer and more air is getting in. Granted the cams are not reaching their full potential but it will make the engine more efficient, so the engine will not need the same amount of boost from the turbo to make the same power as a smaller cam.

Last edited by tehnation; 08-09-2018 at 11:37 PM.
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Old 08-09-2018, 11:39 PM   #16
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I want my cake and want to eat it as well! From what I know a ptw of .003 will give you little to no piston slap, and at the same time I'm wondering why it wouldn't be able to handle high hp when the stock setup can do it....
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Old 08-10-2018, 09:54 AM   #17
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"This Guy" checking in... haha I dont come on here as much as I used to. Building engines for teams under contract these days. Soaks up most of my time. What conclusions have we come to?

Ian,

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Old 08-10-2018, 11:29 AM   #18
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I think u were the one that said u set them to .0025-.00275? I am going with .003.
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Old 08-10-2018, 04:20 PM   #19
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Yes that was me. 0.003" is a safe spot to be.
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Old 08-10-2018, 07:23 PM   #20
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tri state? Where are you? Do you know charlies machine shop in pearl river?
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Old 08-11-2018, 07:50 AM   #21
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you realize that asking for .0025 to .0027 means you are asking for .0026 plus/minus ONE TENTH?

That is an extremely tight tolerance and depending what shop borderline unrealistic and you most likely won't get that regardless of whether they 'agree' to do that.
And frankly, if piston to wall clearances needed to be within a tenth of spec there wouldn't be a car on the road.
You are over thinking this.
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Old 08-11-2018, 08:39 AM   #22
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??? i think you missed something! rexworx does this for a living and he had posted that he does .0025-.0027 which made me curious is all! I already said I went with .003. What i'm trying to avoid is piston slap, and I don't see the point of having a looser ptw because for my hp level it should be able to handle it as well as avoid excessive oil usage from blow by. And why is it unrealistic? A machine shop is all about precision, if it wasn't i would be doing it in my garage! You think precision to the ten thousandth is unrealistic? Engineers would tell you otherwise!
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Old 08-11-2018, 09:36 AM   #23
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Just be glad you didn't go with Carrillo pistons.....I didn't find out until after they are called the "slap happy" piston...noisy as hell, but I make sure to filter the engine oil to look for any big flakes that might indicate a spun rod bearing. Nothing yet after 10,000 miles. Definitely going with an IAG Stage 2 Tuff or even a Stage 2.5 if/when my homebrew shortblock fails...
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Old 08-11-2018, 01:35 PM   #24
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I agree that you dont have to hold one tenth to have a good build. I also agree that most machine shops most likely wont be within the range that some might ask for.

What I meant was I ask for a 0.0025-0.0027. Most end users fall within the range that I personally like with a 2818 forging. Sure their are some builds that I would choose to run looser range one the piston to wall and ring gap clearance. Staged rally, or a car that will see a lot of sustained load and driven hard for a long period of time. The engines never get much chance or combustion chamber temps to cool much. Also cars that are going to run bigger boost. Say 35-40+psi would be a low boost setting just to get things moving. Or that client that has to have 550-600whp and only want to run pumpgas with obviously creates some heat. Those are the times I would choose to run a piston to wall clearance that is 0.003-0.0035 for the most part, if I have a choice in the matter.

Of course the use of Torque Plates is absolutely a must. Ive actually brought blocks to the machine shop after assembling the case, then installing two torque plates. Then all they have to do is measure the pistons I also brought them.

It is rather hard to find a machinist that is willing to put in the time to get things that close and has a controlled environment. That soaks up a lot of time. Most would rather bring things a acceptable point which is good enough. Im not faulting them for that.

rtv is right though. Most places dont have the required measuring equipment to consistently read to 0.0001" Its also not easy to just accurately read consistently done to that kind of resolution. Folks also might not be zeroing their Mics and indicators everyday or through out the day.

The time of constantly checking and measuring really adds up. The cost of good equipment can really add up as well. I personally use Starrett, Sunnen, and Mitutoyo measuring equipment.

Again, Im not saying you have to try and ask for these kind of tolerances. The folks that are aiming for that are not concerned to being competitively priced with all the other local machine shops. The issue is, you generally never know till its too late with that build. Or never at all as the people putting thing together dont have the equipment themselves to measure in a controlled environment.

Their are a few shops through out the east coast that specifically work on subaru engines. I send stuff to a shop in Ohio I used to do a lot of Pro Stock drag engine building for. So maybe needing good ring seal running 80-100psi in a 2800HP V8." Regular refreshes or not haha" Seams like I just go over kill on things.

It doesnt guarantee you will have a oil burner if you shop doesnt hold these tolerances. Most dont. It alot easier said then done. Even harder on a cylinder bore. Trying to get the bore perfectly round and no taper etc from the top to the bottom of the cylinder is no easy task.

RTV is right though. Out of 10 good machine shops. Maybe two do that kind of work. You will also pay for that kind of work. Ive measured quite a few "Blueprinted" Builds from other big name shops. The specs werent close to what the spec sheet says it is. Its rather common.
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Old 08-11-2018, 03:09 PM   #25
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My machine shop does excellent work! I'm not worried.
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