I have a built b16 turbo a clutch away from being dropped into the car, its a 81.5 bore with 9:0 compression CP's.. .Should i stick to that compression, or go up to 10 or 11:0 ... alot of people say high compression an boost dont go good together.. i believe its fine depending mainly on tune, but also high how your talking... oh yea, also will be on 93 octane gas, i know that means alot too.. i have heard peole having trouble with over 12.5 compression on all motor pump what is your take on this...

is it worth upgrading the pistons this far along? ... is 9:0 perfect and have risks with higher compression? or should i just leave it since im this far along, and save it for when/if it blows up.?

 

who said high compression and boost dont go together? muckman is like our poster boy here as to how far high compression engines can go with boost, and beyond. I would say you would be fine up to 11:1 on 93 pump gas. Anything beyond that and you will have to compromise by retarding the ignition timing alot more. But if you have the 9.0 pistons and the motor is assembled and ready to roll, no reason to change them.

 

Under boost, I wouldn't go 11:1 without methanol injection, dynamic compression is just way too high with any reasonable boost levels.

For straight 93 with no other power adders, 10:1 is the limit


But if your motor is already built why take it apart. 9:1 will work just fine

And you haven't even given a power goal

 

yea, i thought 11:0 would be the MAX but i dont want to retard my timing alot of people say low compression and at the time of building motor i was doing research and 9 seemed to be about right, its stock sleeves, my tuner dont want to go past 450 with stock sleeves, in your opinion what do you think stock sleeves will hold reliably on 93? .. and also about compression, i was thinking if i were to switch out, or rebuild, i was thinking like 10.0 compression, right now like i said its 9 compression, but i have a gsr head on it, i believe it bumps it up a few point, and both the head an block are resurfaced i doubt that matters how little gets taken off in the process... how much comp does the gsr head bump it up? .. and if i want to add a few points to get it closer to 10, or even at or beyond, what kind of thoughts do you have on chaning to flat valves, thinner head gasket or both? .. thats easier process, headgasket being the easiest, as i plan on pulling of the valve cover and cams out to make sure there is enough assembly lube on it, an either way add more to be safe.. i may keep it the same, but i may consider a thinner head gasket, im thinking with a 2 or 1 layer and the gsr head, it should be at least 9.6 or even closer if not 10..

 

with 10.1, thats what i run on 30lbs with meth, never had problem. All in the tune.

 

There is no need for all this speculation on what could be better.

9:1 on a turbo motor is great, dont waste your time or money trying to change things now, its already done.

Do not try to bump compression by using a thinner headgasket, this is pointless and will cause nothing but HG troubles, use an oem honda HG.

Your motor will handle 450 whp on 93 pump with forged internals, as long as you have the right turbo/fuel/tune setup.

450whp is pushing the limits of 93 pump gas and the stock sleeves though, will it work? yes, would 400whp be safer? yes.

 

11:1 is no problem but it depends on more than just fuel. Cams, piston, and the tune play a significant role.

Higher compression will make engine more responsive at virtually any level of boost.

 

Like I said, in general 10:1 is the rough limit for a setup using straight 93... anything above that and you ave issues.... such as flame front travel across the domes, which can cause detonation.

Not to mention you need a pretty healthy ignition system to deal with spark on a high compression motor... you can't simply gap the plugs down. It takes a lot of energy to ignite a mixture under that much pressure without blowing the spark out.

 

See link below

https://honda-tech.com/forums/forced-induction-16/high-compression-low-boost-2999654/

This topic has been discussed many times. 11:1 is not a problem with the right setup. Also, I made 425 whp with a Holset turbo, 14 lbs of boost 93 octane. Natural Aspirations made 475 whp with a 5858 on 93 octane. You can check those builds for more details. They were b18c1 builds.

 

Good info in here. Kind of helps me as well as next winter i will be doing a full build but im getting the b16 block sleeved. Right now im on a completely stock motor, head, tb i do how ever have itr cams. Makes 315whp on 8lbs. As soon as i finish swapping the motor into the da shell im going to get retuned up to 14lbs. Looking to get as close as i csn to 400whp on completely stock motor minus itr cams and srp headstuds..im also running a 50trim turbonetics with rc440's and wapbro 255 on 93oct.

 

^^^rc440 will not make it to 400 whp safely.

 

I know thats what im running currently. Getting new ones to bring down to the tuner. Will get installed there and retuned

 

They won't even make it near 350, much less 400

 

Well im only at 315 now with them. And they were on the last motor that made 328

 

if im not mistaken i would uprade the injectors cause your about to max them out. go with some bosch ids they are very consistent and dont need a resistor

 

Anything above 80% duty cycle is bad for an injector... and you're right at that line

 

while you can absolutely go into the 10's static compression, for pump gas 93 octane id keep it between 9 and 10. my car for example is about 10:1 (9.7:1 cp plus head and block resurfaced). it is fine but i wouldnt want more than that. you gotta trade longevity and reliability for a bit of responsiveness. you have to take other factors into consideration, bad gas, increased heat during hot days etc, you really just want a slight buffer for peace of mind.

 

if i was to buy rc 1000's that would be good? i plan on going bigger during next winter (sleeved block bigger turbo) so would the 1000's be ok for me now and just tune them down?

 

As someone else said, ID 1000s are the way to go.

 

thanks will be ordering them soon.

 

AGAIN.... because the motor is already done, you are wasting time and money for no reason.

If you want 400-450 whp 9:1 will get you there just the same as 10:1 or 11:1

If the motor wasnt already built with 9:1 it would be worth thinking about, but its already done.

The only feasable way to make it higher c/r is to pull it back apart and swap to higher c/r pistons.

So your going to spend how much time, and the cost of a new HG, and new pistons for what? Its a waste.

 

^^^WTH are you posting about? Read the thread, seriously.

 

Some people dont read all the way through but anyway good choice with taking our advice with the bosch injectors you will be very pleased with the consistancy they provide for tuning.