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  1. #1
    Non-member Adey aka Ewok's Avatar
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    how much pressure can stock internals take?

    right so ive knocked up a manifold for my 172 and have spoken to a company who can map the car with a few other bits, just looking to find out how much boost can be run on a t28 with a good intercooler on stock internals? there are a few tuning companys that sell off the shelf kits tho they dont seem to give much away on turbo setup and pressures. tech heads out there shed some light
    Last edited by Adey aka Ewok; 15-10-2010 at 19:24.

  2. #2
    Non-member Matt@CodeRedMotorsports's Avatar
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    Re: how much pressure can stock internals take?

    Stock internals???
    C1J......F7R......F4R???
    F7R and F4R have a relatively high compression ratio anyway so at a guess 6-7psi and reliable....

  3. #3
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    cheeky edit

  4. #4
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    ktec site say that it runs 9psi and during testing they ran 12, that seems mighty high for a high comp engine?

  5. #5
    Non-member Spooky's Avatar
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    Re: how much pressure can stock internals take?

    Wasn't the old CTM F4R turbo GTT originally a low pressure conversion? I swear that ran low low boost for a while...

  6. #6
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    the one owned by the chap in weston?

  7. #7
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    Re: how much pressure can stock internals take?

    It doesn't have a lot to do with boost bud. If you go overly safe on the c/r and make sure it's tuned properly then it'll be OK to 300hp I'd say. As you prob know I pushed standard pistons a lot further, only swapping them for forged because I got paranoid they'd let go. they came out looking like new. Rods on the other hand are crap. Invest in some steel rods and bolts, if nothing else

  8. #8
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Scoff View Post
    It doesn't have a lot to do with boost bud. If you go overly safe on the c/r and make sure it's tuned properly then it'll be OK to 300hp I'd say. As you prob know I pushed standard pistons a lot further, only swapping them for forged because I got paranoid they'd let go. they came out looking like new. Rods on the other hand are crap. Invest in some steel rods and bolts, if nothing else
    how safe is overly safe? not looking for huge power out of it, hope to go for more than the itb car made but on a budget, ive got a set of pistons tho i cut one in half to see how much meat was there to see how much i could shave off tho there quite thin to start with. trying to keep all the costs down, thus doing any fab work myself, not done anything like this before

  9. #9
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    are there any shorter rods that are shorter than can be thrown in to lower it and make it safer?

  10. #10
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    Re: how much pressure can stock internals take?

    No shorter rods, all 144mm from memory.

    I don't know how much power you want, but if 250hp will do then I'd go to 9.5:1 and run 8 or 9psi boost. That'll be safe as houses. T28 will be too small to ask any more of it I'd say.

  11. #11
    Non-member Markey Mark (BD)'s Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    are there any shorter rods that are shorter than can be thrown in to lower it and make it safer?
    Volvo 480 Turbo rods are 10mm shorter then Clio F7P and F7R rods i believe, i remember measuring them up to see if some Clio rods would fit my Volvo lump. Also think they are abit thicker then the Clio 172 rods from as standard so would be little bit stronger.

    Sure they would lower the comp abit for you although not too sure how much by.

  12. #12
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Markey Mark (BD) View Post
    Volvo 480 Turbo rods are 10mm shorter then Clio F7P and F7R rods i believe, i remember measuring them up to see if some Clio rods would fit my Volvo lump. Also think they are abit thicker then the Clio 172 rods from as standard so would be little bit stronger.

    Sure they would lower the comp abit for you although not too sure how much by.
    would be good if anyone has a set to measure up

  13. #13
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Scoff View Post
    No shorter rods, all 144mm from memory.

    I don't know how much power you want, but if 250hp will do then I'd go to 9.5:1 and run 8 or 9psi boost. That'll be safe as houses. T28 will be too small to ask any more of it I'd say.
    250 would defo be enough im sure for the track whore, much more and im in to the relms and cost of just chucking a 225 lump in with a remap

  14. #14
    Non-member Markey Mark (BD)'s Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    would be good if anyone has a set to measure up
    I got a spare Volvo con-rod here, if you can measure the Clio one i'll measure the Volvo one and we'll compare them mate.

    As Scoff says Clio are 144mm from centre of big end to centre of gudgen pin and Volvo was about 10mm shorter from memory

  15. #15
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    ill see what i can dig out if you can get a measurement up for that one

  16. #16
    Non-member Markey Mark (BD)'s Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    ill see what i can dig out if you can get a measurement up for that one
    Will do mate

  17. #17
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    ill see what i can dig out if you can get a measurement up for that one
    133mm from memory Way too short to go in an F block though.

  18. #18
    Non-member Markey Mark (BD)'s Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Scoff View Post
    133mm from memory Way too short to go in an F block though.
    That does ring a bell mate, i remember measuring them up in my engine to see if they were same as Clio rods but couldn't remember exactly.

    Worth the thought though, thinking of it that extra 11mm depth the piston would sit at would bring the comp down a serious amount.

  19. #19
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    ok so how much height needs to come off for a ratio of 9.5-1?

  20. #20
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    ok so how much height needs to come off for a ratio of 9.5-1?
    well, we know we have 499.5cc of swept volume per cyl. IE, 1998cc in total.

    standard CR is 11:1 so from that we can calc how much volume is in the standard combuistion chamber (including gasket, valve depressions in piston, etc etc):

    swept vol
    ------------
    cr-1


    499.5
    -------
    11-1
    = 49.95cc

    If we want to get to 9.5:1 we need to calculate the new combustion chamber volume:

    499.5
    -------
    9.5-1
    = 58.76cc

    That tells us we need to add 8.81cc's to each chamber (58.76 - 49.95).

    using pi x r2 we can work out that 1mm of piston height is worth 5.37cc's of volume, so you need to remove (8.81/5.37) = 1.64mm

  21. #21
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Scoff View Post
    well, we know we have 499.5cc of swept volume per cyl. IE, 1998cc in total.

    standard CR is 11:1 so from that we can calc how much volume is in the standard combuistion chamber (including gasket, valve depressions in piston, etc etc):

    swept vol
    ------------
    cr-1


    499.5
    -------
    11-1
    = 49.95cc

    If we want to get to 9.5:1 we need to calculate the new combustion chamber volume:

    499.5
    -------
    9.5-1
    = 58.76cc

    That tells us we need to add 8.81cc's to each chamber (58.76 - 49.95).

    using pi x r2 we can work out that 1mm of piston height is worth 5.37cc's of volume, so you need to remove (8.81/5.37) = 1.64mm
    ahhh math! any one used a decompresion plate? would save me time and money if i could whip the head off and slap one of those in?

  22. #22
    Non-member Andrew Cooke's Avatar
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    Re: how much pressure can stock internals take?

    how about opening up the combustion chamber, deshroud those valves a bit.

  23. #23
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Andrew Cooke View Post
    how about opening up the combustion chamber, deshroud those valves a bit.
    Erm can I do it with a socket set a hacksaw and a screwdriver?

  24. #24
    Non-member Andrew Cooke's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    Erm can I do it with a socket set a hacksaw and a screwdriver?
    sure, but it'll take you a while

  25. #25
    Non-member allanr5gtt's Avatar
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    Re: how much pressure can stock internals take?

    stock piston dished to 9.5-1


  26. #26
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    172 pistons? how have they lasted?

  27. #27
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Scoff View Post
    It doesn't have a lot to do with boost bud. If you go overly safe on the c/r and make sure it's tuned properly then it'll be OK to 300hp I'd say. As you prob know I pushed standard pistons a lot further, only swapping them for forged because I got paranoid they'd let go. they came out looking like new. Rods on the other hand are crap. Invest in some steel rods and bolts, if nothing else
    F7R rods are much stronger, aren't they?

  28. #28
    Motech Tony Walker's Avatar
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    Re: how much pressure can stock internals take?

    Have you tried to make the valve clearance larger on those pistons allanr5gtt?

  29. #29
    Motech Tony Walker's Avatar
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    Re: how much pressure can stock internals take?

    Or did the valves try to do it themselves? lol

  30. #30
    Non-member J$£5GTT's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    Erm can I do it with a socket set a hacksaw and a screwdriver?
    pmt the winning team!!!!!

  31. #31
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    so could i go pikey, and fit f7r rods with arp botom end bolt with dished pistons? and maybe a thicker head gasket or uber pikey 2 headgaskets and get a half about setup?

  32. #32
    Non-member allanr5gtt's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Tony Walker View Post
    Or did the valves try to do it themselves? lol

  33. #33
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    how thin can you actually go on pistons before they become weak? the 172 piston is the only one ive ever cut in half but they really do seem to be thin to start with, isnt shaving them going to make them lots weaker?

  34. #34
    Non-member Andrew Cooke's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    how thin can you actually go on pistons before they become weak? the 172 piston is the only one ive ever cut in half but they really do seem to be thin to start with, isnt shaving them going to make them lots weaker?
    ooh, share the pics, how much meat is there around the valve cutouts? Inquiring minds need to know

  35. #35
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    it measures 8mm (or there abouts) at the center and tapers outm wider towards the edges

    Last edited by Adey aka Ewok; 22-10-2010 at 21:45.

  36. #36
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    Re: how much pressure can stock internals take?

    8mm thats plenty, I didn't think they'd be that thick!!

    Good pic

    I took 1.6mm off my old pistons, for the old 9.5:1 ratio, worked well making 260hp at 10psi

  37. #37
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    now thats figures im liking the sound of whats the difference between flatting them off or dishing, will it make a difference atall?

  38. #38
    Non-member Andrew Cooke's Avatar
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    Re: how much pressure can stock internals take?

    how much deeper do you think one could cut the valve pockets?

  39. #39
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    ive got 3 more spare pistons if your intrested and want to chop em up, tho i think youve got shed loads of meat to do the valve pockets alot deeper, i know one of the tuning companys would recess them deaper for use with high lift cams in the 172 engine

  40. #40
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Andrew Cooke View Post
    how much deeper do you think one could cut the valve pockets?
    heres a pic of my old ones with 1.6mm skimmed off



    not much of the valve indents left... i guess they're only 2mm deep

  41. #41
    Non-member Andrew Cooke's Avatar
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    Re: how much pressure can stock internals take?

    wrong end of the stick there Ashy, I'm talking about leaving the piston tops standard, but cutting the valve pockets deeper. I have a feeling that I'm going to get pistons and valves kissing...

  42. #42
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Andrew Cooke View Post
    wrong end of the stick there Ashy, I'm talking about leaving the piston tops standard, but cutting the valve pockets deeper. I have a feeling that I'm going to get pistons and valves kissing...
    you going for some really fruity cams?

  43. #43
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Andrew Cooke View Post
    wrong end of the stick there Ashy, I'm talking about leaving the piston tops standard, but cutting the valve pockets deeper. I have a feeling that I'm going to get pistons and valves kissing...
    I knew what you meant marrow, what I was meaning was...

    I took 1.6mm off mine, they look like they go 2 - 2.5mm deep judging by that photo and the piston is 8mm thick ish. So depending on how much metal you need to leave you can work out a rough depth.

    I think

  44. #44
    Non-member Andrew Cooke's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Ashy View Post
    I knew what you meant marrow, what I was meaning was...

    I took 1.6mm off mine, they look like they go 2 - 2.5mm deep judging by that photo and the piston is 8mm thick ish. So depending on how much metal you need to leave you can work out a rough depth.

    I think
    sounds like I don't need to worry, and just cut away

    btw, if I do it I'll do them in situ with a modified valve and a drill... saw a pic of it being done years ago on a Cossy engine, just been needing a reason to do it myself

  45. #45
    Non-member Andrew Cooke's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Adey aka Ewok View Post
    you going for some really fruity cams?
    skimmed head old bean

    oh, and maybe some big cams

  46. #46
    Non-member Brigsy's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Andrew Cooke View Post
    sounds like I don't need to worry, and just cut away

    btw, if I do it I'll do them in situ with a modified valve and a drill... saw a pic of it being done years ago on a Cossy engine, just been needing a reason to do it myself
    I heard a tale of somebody making valve pockets on rover v8 pistons with an angle grinder years ago after a hot cam caused a bit of contact, last min bit of pmt to get the car to a drag event at york raceway, ran mint too

  47. #47
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    Quote Originally Posted by Andrew Cooke View Post
    skimmed head old bean

    oh, and maybe some big cams
    Good good, so flat topping the pistons is fine yeah? Are u pushing yours ashy or is it a safe map with not much abuse?

  48. #48
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    Re: how much pressure can stock internals take?

    i was pushing them towards the end but the clutch started slipping at 16psi so gave up then did the bottom end... It'll be interesting to see what condition they're in once I get the old block pulled appart.

  49. #49
    Non-member Adey aka Ewok's Avatar
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    Re: how much pressure can stock internals take?

    Sweet, would be good to see, 16psi woulda been seeing you close to 300bhp wouldn't it?

  50. #50
    Non-member Rob@Backyardracing's Avatar
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    Re: how much pressure can stock internals take?

    Bit of subject here, but still may interest regards comp.. or its just me been in a dream all day..

    Ok, why is it we run a slower burning fuel (high oct) with higher comp motors or high boost, and add so much advance in some cases... ok the slower fuel to stop det, but why cant we find a fuel that burns faster than normal 95 petrol and let the burn start direct at tdc.. In this case the motor will not see any initial pressure build up of such from the burn before tdc and then all lets loose...ok i know this initial pressure build up helps with the total cyl pressure.. (we all know this ****) anyway......

    Ok so why not run like 15.0:1 comp + and plus your boost? and use a fast burning fuel and start the burn at around tdc, but as the piston drops the pressure stays constant throughout that duration as a result to its style of burn, giving a smoother, less strain, and longer push...

    Am i just waffling a load of ****e here.. prob the case..

    What the hell do F1 cars do reving to 18k rpm? what fliping fuel do they use? surely its a fast burning fuel.. Disscuss...

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