im going turbo soon and am going to be buying my pistons/rods soon....so what do you guys suggest for a good all around compression ration...so far i have a 14b, 30# injectors, 255 fuel pump, SFMU....what do you think would be the best compression ratio to run around 15 pounds?? maybe 18-20 at the track?
im thinking 8.5-8.8..but not sure what to go with....also, do you think id be allright with stock rods for 15-18psi....ive heard of people going to 19 pounds...but id would be doing 15 daily
doug

first thing.. do it complete and correct or dont do it at all. change out bearings, rods and pistons. 8.6 compression will be good. another thing, don't bother with the 14b.. i beg you. 15lbs of boost on a 14b is like 5lbs of boost with a 16g..

james

I am with him on this, do it right from the begining or you'll regret it, but stock rods will hold to somewhere around 15-18 psi, 8.6 will work good, or you can go with even a little lower if you wanted.

you shouldn't have mentioned that they will do (rods).. replace them.

8.6 oh i fear for you with reg driving.. outta boost bleh life might suck
well maybe not im speaking my car here.. so never mind

umm i read somewhere about the 14b vs 16g and a common misconception
they pretty much flow the same the 16g is just less.. oh fuck whats the word

like it puts less strain on the turbo.. i could be wrong.. but a ported 14b is a great turbo.. might not be the best but for the price it can do wonders

can get a 1g into the 12s..

Originally posted by evan2
8.6 oh i fear for you with reg driving.. outta boost bleh life might suck well maybe not im speaking my car here.. so never mind umm i read somewhere about the 14b vs 16g and a common misconception they pretty much flow the same the 16g is just less.. oh fuck whats the word like it puts less strain on the turbo.. i could be wrong.. but a ported 14b is a great turbo.. might not be the best but for the price it can do wonders can get a 1g into the 12s..

Oh my god dude, take that integra off your signature!!bLAH!

well im starting with the 14b for now....maybe later down the line ill upgrade....but i didnt see any reason to upgrade the rods if i didnt need to.... ill probably end up getting some eagle rods just so i dont have to do it again....but i found a 420a with only 25k miles on it....so i wasnt planning on touching the bedplate/crankshaft....i thought i could just change pistons/rods and rod bearings and leave the rest alone
doug

If any machinging needs to be done to the block, and getting forged piston you should make sure the piston to bore clearance is what's recommended by the manufacturer of the pistons. The engines going to have to be tore down.

I would never drop below stock compression. If I boosted it would be on 10.5:1.



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Originally posted by Michael_97RS
I would never drop below stock compression. If I boosted it would be on 10.5:1.

Oooohhhh boy....here we go! LOL :rolleyes

Originally posted by lickscissors
well im starting with the 14b for now....maybe later down the line ill upgrade....but i didnt see any reason to upgrade the rods if i didnt need to.... ill probably end up getting some eagle rods just so i dont have to do it again....but i found a 420a with only 25k miles on it....so i wasnt planning on touching the bedplate/crankshaft....i thought i could just change pistons/rods and rod bearings and leave the rest alone doug

Yes I would say update everything from the start should be upgraded but that YES you rods will work. I've never used stock rods on boost from experience, but there have been enough members to prove they can take a solid 15 pounds. I know Stan used his rods with 75 shot on some ROSS pistons for years then boosted with 10.5:1 compression, there was Tommyboy who has gone through more blocks than anyone on the board. Anyway I wouldn't trust stock pistons, period, they will go eventually, since almost know one can seem to keep their pressure down on stock internals.

Also I agree with evan on the 14B, there is no way a 16G outperforms that much. To the T to small (T25) maybe that's a different story but the 14B I've seen at 22lbs and I ran my 14G at 16 pounds and at 7.8:1C it was mroe than enough to fuckup some stock "sportscar"

8.5:1 to 9:1 is great for daily driving and using premium pump gas.

so how about 8.8:1? what kind of problems do i face with detonation.... i will be using premium pump gas....and about the piston bore clearance issue....i was planning on taking the block...with the crank still installed, and having a machine shop check the bore....do i need to have the crank off? i was really hoping not to touch it
doug

Originally posted by lickscissors
so how about 8.8:1? what kind of problems do i face with detonation.... i will be using premium pump gas....and about the piston bore clearance issue....i was planning on taking the block...with the crank still installed, and having a machine shop check the bore....do i need to have the crank off? i was really hoping not to touch it doug

I have 8.8:1. No problems with detonation using 93 octane up to 20 psi.

No, you can leave the crank in the block. A machine shop should hardly sweat that.


What clearance-to-bore issue?

well ill let the machine shop check my bore...but i dont think its going to need to be touched.... id like to get 8.8:1...it sounds like a good inbetween compression...im hoping to just get some new rods, but its really tempting to use the stockers
doug

I think he's refering to my post. Forged pistons require different clearances than stock. I would never just drop a set in without having a machine shop check it out. Also, I'd be worried about metal shavings from boring getting around the bearings, I feel much safer doing it with the crank out.



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yes, if i did need them bored id take the crank out...i just thought for them to check it id leave it in....it saves me a hassle.... do you think an engine with 25k miles on it would really need bored? i was hoping it wouldnt
doug

Originally posted by lickscissors
yes, if i did need them bored id take the crank out...i just thought for them to check it id leave it in....it saves me a hassle.... do you think an engine with 25k miles on it would really need bored? i was hoping it wouldnt doug

You never know, I'm usually a bit pesemistic and assume things will be bad. You might get away with it. It depends on the dimensions of the pistons and the dimension and roundess of your bore. You might get lucky and a hone is all your need and they hapen to be in spec.



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well, ill take it to the machine shop and see what they say.... another question....do you guys see any problem with buying used pistons?? i really think i should just start fresh...but i can get 3 weisico pistons 8.5:1 for 150....so it would be a hell of a deal, but i just dont feel to confident
doug

yea but i speak honda now, and i never had a 5spd 420a...
but with lack of lowend tq my boy paul who is also my tuner.. ran 8 7 1 comp on his turbo gsr.. though at 22psi he made 450whp and ran 11s he said for the daily grind it sucked..

so he went to 9 7 1 new rods n some cams.. that was during his winter break, hope too see what it doesnow

i like high comp with some decent boost.. with a strong bottom end and great tune i could prob stay at 10 or just go to 9 5 1, and boost a lot

though i have a lil advantage in the tunning area becuase of whats offered..

and for the 14b vs 16g guys.. there a page somewhere that goes into big detail on it..
read it..i did years ago

You should REALLY expect your block to need some boring. Michael's right. There is a great deal of difference in your cylinder to piston clearances when talking about forged pistons as opposed to cast ones. It's not that expensive to bore anyways (maybe $50-$75), don't sweat it!

i know its not that expensive...but this is my first rebuild, and i thought if i didnt have to touch the crank, thats another seal i dont have to replace and more bearings i wouldnt have to touch
doug

You might also want to check on how much it will cost to get the stock rods put onto the forged pistons. I heard they have to be pressed in or something because they don't except a floating pin, I wouldn't buy used pistons because you never know what they have been through, even if they look good.

thats what i thought about the used pistons....i talked to my local machine shop, and they said there should be no problem in matching up the pistons to the stock rods....and if they needed machined, he could do it pretty cheap.... is anyone running the stock rods currently or know of anyone that is, has anyone actually bent them due to boost?...id just hate to spend $300 on rods if all im going to be doing is 15psi...that money can go into some cams
doug

what i would suggest and as with the previous replys. go with what you think you can handle at the time till you're experienced. you seem like you're a beginner of all this tunning stuff. so i would say 8:6:1 to 8:8:1. you have to familiarize yourself in tunning before you take a step towars higher compression and turbo. you constantly have to keep tunning and using race gas so you can avoid blowing up. many people think that going lower compression loses power. but then why do Supras, turbo DSM's, Skylines all have 8:6:1 compression? less room for error from blowing up.i feel now that i have a grasp of how tunning works and what to adjust to according to EGT, A/f mixture, timing, fuel pressure adjusting, size injectors, and many dyno runs. i think i'm ready to maybe go the most 9:1 comp...no more than that. many turbo GSR's take that route and make nice ass numbers on low boost. but if i were you, go low and learn. high compression is a risk. someone on this board took that route and regrets it. 10:6:1 or something. that's my suggestion.

Originally posted by lickscissors
thats what i thought about the used pistons....i talked to my local machine shop, and they said there should be no problem in matching up the pistons to the stock rods....and if they needed machined, he could do it pretty cheap.... is anyone running the stock rods currently or know of anyone that is, has anyone actually bent them due to boost?...id just hate to spend $300 on rods if all im going to be doing is 15psi...that money can go into some cams doug

I've got over 14,000 miles now on my stock rods.... and I'm up at 19psi...
:thumbsup

But I'm not sure if I'd recommend it... haha ;)

Originally posted by lickscissors
i know its not that expensive...but this is my first rebuild, and i thought if i didnt have to touch the crank, thats another seal i dont have to replace and more bearings i wouldnt have to touch doug

okay so let me gets this straight you want to try and slap some forged pistons on stock rods with boring and without remving the crank because your worried about the 100$ it would take to get new bearings and seals

okay so say your clearances are inspec for the cylinders unlikly but okay, so you cruising around and your get the car dynoed and your feeling good about things so your boosting around 11-15 psi
and you get a bad batch of gas meaning its lost its octane a bit, you detonate and shatter those weak arse stock rods now your out
500$ for pistons gonna have to get stronger rods this time, so 350$ for eagles, crank need machining, if you dont need a new one that atleast 50-75$ new bearings and seals anotehr 100$ plus the money to bore the block, another 75$ or so
this time you'll probably have to deck the block so another 50$
now usually when you throw a rod you take the cylinder head and valves with it, that can rack up 300-500$ easy if you damaged or cracked the head.

and all this was to save at the most 400$ in the begining.....

people have bent the stock rods on 11psi and some have held to 18psi,

its like upgrading have of a aluminum chain to steel and then stress testing and abusing it like its a steel chain.

only as strong as the weakest link.

well i think ill get some rods while im in there.... but i dont see the need to touch the crank if the cylindar walls dont need bored.... if they are in spec, im going to get some new rod bearings, rods, pistons, piston rings and call it a day..... there is no way i was running higher than 8.8-1 pistons...i fear the almighty detonation.... i just see the whole crank bearings and bedplate as being a bitch to seal and its a whole nother batch of bearings that could go bad.... if they are fine right now, i dont see the need to mess with them.... am i way off here?
doug

main bearings rarely go bad unless starved for oil. but you ahve the motor out why not ahve the clearances checked at the machien shop and see if you can polish the crank for 20$ and toss in the new bearings.

the bed plate is not very hard to work with the only even challenging part is getting it off and thats not even very hard a rubber hammer does most the work.

if the clearances are off on your bearings just on the rods when you put it back together it might have too much oil clearance and you could spin a bearing.

the crank clearances are one of the most important aspects of a motor as import or more then the clearances on the rings(ie compression)