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It doesn't make sense you have such bad leakdown but the car drives fine. When I lost compression on both my OEM and built motor it was definitely noticeable and the drive ability was poor.
It also doesn't make sense for all cylinders to compression test within 10psi of each other and to burn zero oil... Something still just doesn't add up to me.
 

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Did we ever find out the cause of this? I literally just went through the something very similar yesterday on another 4 cyl car. The car had a dead cyl 4. Misfires all kinds of ways on that cylinder. So much that the ecu would just shut that cylinder down after the first fire up. The engine had ok compression of 190-180psi all around cold. Cylinder 4 had terrible leak down of 30%. After scoping the cylinders, I found cracks in the cylinder walls at the bottom of both 1 and 4.
 

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Given the block is bored to 99.75mm, should I be looking to bore the block to 100mm get new pistons and build my heads? That is what it is sounding like.
Bore out to 100mm, new pistons, get gas ported piston rings (JE and Total Seal), new valves, springs, retainers ... proper tune and go. You'll need to ensure those heads aren't damaged though. Should make your car "new" after that. Any of that gunk in your turbo? Check the exhaust side of the turbo.

Is this a daily or a hard weekend beater or racer? Boring out is fine, but it's non-standard. Other option just put sleeves in it and go back to 99.5 with new 99.5 pistons.
 

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<snipped>... get gas ported piston rings (JE and Total Seal)...<snipped>
Total Seal ring set
Gas ported AP top ring
Ductile napier gapless second
Standard tension (tension is dependent upon axial dimension) oil ring
 
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Total Seal ring set
Gas ported AP top ring
Ductile napier gapless second
Standard tension (tension is dependent upon axial dimension) oil ring
I don't run the gapless on my 2nd, but I will the next time I pull the motor -- good point. That combo done right along with a good tune will make the car run forever basically if you use the right oil ...
 

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I don't run the gapless on my 2nd, but I will the next time I pull the motor -- good point. That combo done right along with a good tune will make the car run forever basically if you use the right oil ...
...and use torque plates along with the correct bore surface roughness parameters for the bore/hone operation.
 
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...and use torque plates along with the correct bore surface roughness parameters for the bore/hone operation.
You've been listening to "Hidden Horsepower" too much -- ha ha! (100% true what you said). Don't forget the 65 degree cross hatch for our engines too ... ha ha!
 

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You've been listening to "Hidden Horsepower" too much -- ha ha! (100% true what you said). Don't forget the 65 degree cross hatch for our engines too ... ha ha!
I was advised to use a 45 degree included cross hatch angle over the factory 60 by Total Seal. Less ring rotation, less oil migration from the bottom end, and reduced blow by.

The profilometer does not lie!
 
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I was advised to use a 45 degree included cross hatch angle over the factory 60 by Total Seal. Less ring rotation, less oil migration from the bottom end, and reduced blow by.

The profilometer does not lie!
I will do a video on that when I get time ... get some pipes, cross hatch them at different angles, dab oil on them, and see which holds the oil the longest ... I'd like to get a profilometer as well from TS ... I will eventually. If you have one, sweeeeeeeeeet! I'm jealous ....
 

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I will do a video on that when I get time ... get some pipes, cross hatch them at different angles, dab oil on them, and see which holds the oil the longest ... I'd like to get a profilometer as well from TS ... I will eventually. If you have one, sweeeeeeeeeet! I'm jealous ....
A 45-degree cross-hatch offers less oil migration from the bottom of the cylinder to the top. The flatter cross-hatch angle reduces oil migration speed and piston ring rotation speed.

I have the Mitutoyo SJ-210 profilometer. It's a very helpful tool.
 

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A 45-degree cross-hatch offers less oil migration from the bottom of the cylinder to the top. The flatter cross-hatch angle reduces oil migration speed and piston ring rotation speed.

I have the Mitutoyo SJ-210 profilometer. It's a very helpful tool.
Well, 45 is the standard on inlines, Vs ... seems strange on a horizontal ... Total Seal says 65 because I believe it's standard on Porsches ... I've never seen anything written for Subis. I need your SJ-210 ... don't leave it laying around :)
 

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Well, 45 is the standard on inlines, Vs ... seems strange on a horizontal ... Total Seal says 65 because I believe it's standard on Porsches ... I've never seen anything written for Subis. I need your SJ-210 ... don't leave it laying around :)
Porsche Nikasil bores use a 10-15 degree cross-hatch included angle. I'm not sure about Lokasil or Alusil bores.
BMW uses 5-10 degrees on Lokasil and Alusil.
 
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Discussion Starter · #56 ·
Haha, you guys bantering is making my day.
Anyways as far as an update goes. I really don’t have time with work at the moment to do this myself. I’m having a local performance shop that has good rep pull the block and let me know what to do. They were really straight with a buddy of mine who had blown rings. So I will most likely go with what they say. I’m fine with putting in a new long block. This is my fun car. I have a Q50 as my daily. I wanted built heads anyway so it’s either.
1. Fix my bottom end, build the heads
2. Replace short block, build heads
3. Long block.
Let me know what y’all think. Ty in advance. Money isn’t necessarily the biggest issue. I just can’t go crazy!
 

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Haha, you guys bantering is making my day.
Anyways as far as an update goes. I really don’t have time with work at the moment to do this myself. I’m having a local performance shop that has good rep pull the block and let me know what to do. They were really straight with a buddy of mine who had blown rings. So I will most likely go with what they say. I’m fine with putting in a new long block. This is my fun car. I have a Q50 as my daily. I wanted built heads anyway so it’s either.
1. Fix my bottom end, build the heads
2. Replace short block, build heads
3. Long block.
Let me know what y’all think. Ty in advance. Money isn’t necessarily the biggest issue. I just can’t go crazy!
what's your budget? and what are your goals for the car?

if you can swing it, go with an IAG block, be it a longblock or shortblock. make sure it's closed deck, and get the 14mm headstuds, of course if it fits the budget/goals of the car.
 

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Discussion Starter · #58 ·
what's your budget? and what are your goals for the car?

if you can swing it, go with an IAG block, be it a longblock or shortblock. make sure it's closed deck, and get the 14mm headstuds, of course if it fits the budget/goals of the car.
My max Budget is 40k for this entire build. I can't be spending that all now. But realistic, I want to make about 600 WHP. Is the IAG 700 Long block a good choice for this application. Down the road. I am going to re-do the fuel system with bigger injectors, fuel rails, front mount intercooler, and rotated turbo.
 

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My max Budget is 40k for this entire build. I can't be spending that all now. But realistic, I want to make about 600 WHP. Is the IAG 700 Long block a good choice for this application. Down the road. I am going to re-do the fuel system with bigger injectors, fuel rails, front mount intercooler, and rotated turbo.
i'd talk to IAG directly,

but based on my knowledge, if you want 600whp, you dont want the IAG700. The 700 is rated for 700BHP, not 700WHP. if my math is correct, that would be safe for about 550whp. which honestly is quite a bit. If you have never driven/ridden in a 500+whp STi, you'd be surprised at how fast is actually is. my guess is that when you talk directly to IAG, they will likely say the IAG900 long block would be better suited to your 600whp goal.

i should also note, that i have seen multiple IAG blocks people push slightly past what is suggested on power with good long term success, take that with a grain of salt, as getting to whp the same car can read drastically different whp numbers pending the dyno type/correction factor/altitude/ambient temp etc.

also keep in mind, that to make 600whp, you will be in the turbo range of likely laggy. the garrett gtx3576r gen2 can get you there (as with other brands in similar sized setups) and still be streetable, but going bigger will have mixed reviews on the laggyness of the turbo itself. some dont mind the additional lag of a bigger turbo, some hate it and prefer a smaller turbo even with less power as it's typically more fun on the street (if you plan on racing in competition, check the rules for whatever class you want to run in and mod according to those).

for a story/reference, even though it's a smaller power setup. my roomate had an 05 STi with an fp black or red (cant remember which). he and i raced, and his car was making approx 425whp, he outran me pretty easily. but both of us agreed for a street setup, my 370whp 20g xtr setup was more fun, because the turbo was alot faster to come into boost. so even though his 05 was faster than my 06, both of us agreed mine was more fun. just something to think about as bigger/more power doesnt always mean more fun.
 

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Discussion Starter · #60 ·
i'd talk to IAG directly,

but based on my knowledge, if you want 600whp, you dont want the IAG700. The 700 is rated for 700BHP, not 700WHP. if my math is correct, that would be safe for about 550whp. which honestly is quite a bit. If you have never driven/ridden in a 500+whp STi, you'd be surprised at how fast is actually is. my guess is that when you talk directly to IAG, they will likely say the IAG900 long block would be better suited to your 600whp goal.

i should also note, that i have seen multiple IAG blocks people push slightly past what is suggested on power with good long term success, take that with a grain of salt, as getting to whp the same car can read drastically different whp numbers pending the dyno type/correction factor/altitude/ambient temp etc.

also keep in mind, that to make 600whp, you will be in the turbo range of likely laggy. the garrett gtx3576r gen2 can get you there (as with other brands in similar sized setups) and still be streetable, but going bigger will have mixed reviews on the laggyness of the turbo itself. some dont mind the additional lag of a bigger turbo, some hate it and prefer a smaller turbo even with less power as it's typically more fun on the street (if you plan on racing in competition, check the rules for whatever class you want to run in and mod according to those).

for a story/reference, even though it's a smaller power setup. my roomate had an 05 STi with an fp black or red (cant remember which). he and i raced, and his car was making approx 425whp, he outran me pretty easily. but both of us agreed for a street setup, my 370whp 20g xtr setup was more fun, because the turbo was alot faster to come into boost. so even though his 05 was faster than my 06, both of us agreed mine was more fun. just something to think about as bigger/more power doesnt always mean more fun.
This is very true, its my street car. And most of the roads by me are long and straight. I personally don't mind the lag. And do not plan to race this on a track. I may do the drag strip one day. And I would be happy with 550 WHP but I will give a shout to IAG to see what they think I should do. Thanks!
 
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