how much pressure can stock internals take?

[Adey aka Ewok]

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 :agree::)

[Matt@CodeRedMotorsports]

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

[Adey aka Ewok]

cheeky edit;)

[Adey aka Ewok]

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

[Spooky]

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

[Adey aka Ewok]

the one owned by the chap in weston?

[Scoff]

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 :)

[Adey aka Ewok]

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

[Adey aka Ewok]

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

[Scoff]

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.

[Markey Mark (BD)]

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.

[Adey aka Ewok]

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

[Adey aka Ewok]

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

[Markey Mark (BD)]

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

[Adey aka Ewok]

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

[Markey Mark (BD)]

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

Will do mate

[Scoff]

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

133mm from memory :) Way too short to go in an F block though.

[Markey Mark (BD)]

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.

[Adey aka Ewok]

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

[Scoff]

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

[Adey aka Ewok]

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?

[Andrew Cooke]

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

[Adey aka Ewok]

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?

[Andrew Cooke]

Erm can I do it with a socket set a hacksaw and a screwdriver?

sure, but it'll take you a while

[allanr5gtt]

stock piston dished to 9.5-1

http://www.rtoc.org/files/Technical%20Files/Allanr5gtt/allans%20file%20206.jpg

[Adey aka Ewok]

172 pistons? how have they lasted?

[Jimmy_GTT]

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?

[Tony Walker]

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

[Tony Walker]

Or did the valves try to do it themselves? lol

[J$£5GTT]

Erm can I do it with a socket set a hacksaw and a screwdriver?

pmt the winning team!!!!!

[Adey aka Ewok]

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?

[allanr5gtt]

Or did the valves try to do it themselves? lol

:agree::wasntme::laugh:

[Adey aka Ewok]

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?

[Andrew Cooke]

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 :scared:

[Adey aka Ewok]

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

http://www.rtoc.org/files/Technical%20Files/adeys%20useless%20stuff/IMG_0494.JPG

[Ashy]

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

Good pic :agree:

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

[Adey aka Ewok]

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

[Andrew Cooke]

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

[Adey aka Ewok]

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

[Ashy]

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

heres a pic of my old ones with 1.6mm skimmed off

http://www.rtoc.org/boards/picture.php?albumid=344&pictureid=3269

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

[Andrew Cooke]

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...

[Adey aka Ewok]

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?

[Ashy]

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 :confused: :laugh:

[Andrew Cooke]

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 :confused: :laugh:

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

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 :laugh:

[Andrew Cooke]

you going for some really fruity cams?

skimmed head old bean ;)

oh, and maybe some big cams :D

[Brigsy]

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

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 :laugh:

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:D

[Adey aka Ewok]

skimmed head old bean ;)

oh, and maybe some big cams :D

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?

[Ashy]

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.

[Adey aka Ewok]

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

[Rob@Backyardracing]

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...

[GARY GRWTURBO]

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 :)

have to agree with you there
ive bent 2 rods in a month

first one went so i stripped the block i had spare second hand rods laying around so i re-gride the crank at my mates workshop fitted new shells
3 weeks later bent a different rod

good job a have 4 engines on the shelf:santa: