Steven280zx Posted September 26, 2006 Share Posted September 26, 2006 well guys i'm really confused now and lets see if we can get a bit of a debate going here. i'm told that dished pistons decrease c/r and therefore allow us to run more boost from the turbo. this is older thinging. nowadays there are not dished pistons in turbo charged cars. so why would someone whos doin a turbo conversion get dished if they could get flat tops that would survive the heat at a c/r of 9.5. i was talkin to brian from wiseco pistons and he said most ppl are running flat tops at a 9.5 c/r. so here's the question. to dish or not to dish? Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 27, 2006 Share Posted September 27, 2006 Something you might want to consider is that you are not using a modern head that is designed to work with a flat top piston under boost. Nissan decided to use a dished piston on their turbo blocks, possibly because they had them laying around and needed to put them somewhere, but probably not. Modern combustion chambers are designed to a level that was not possible even 20 years ago, so it's not really fair to look at say a Subaru STI engine and ask why my L28 isn't built like that. I have heard a theory that using a dish piston concentrates the force of the combustion on the piston and not the head, supposedly better for power production and not so hard on head gaskets and fasteners, but I don't remember the specifics well enough to relay it properly. www.theoldone.com has some interesting discussion about chamber design and matching pistons. Quote Link to comment Share on other sites More sharing options...
nismopick Posted September 27, 2006 Share Posted September 27, 2006 Here's the 4 page discussion from ZDriver: http://zdriver.com/forums/showthread.php?t=20171 Question all cleared up. Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 27, 2006 Share Posted September 27, 2006 Okay so I read through all that and it just made my head hurt. What exactly did that clear up for you? Quote Link to comment Share on other sites More sharing options...
Steven280zx Posted September 28, 2006 Author Share Posted September 28, 2006 wow hey nismopick i didnt no u wer on here to yeah i use zdriver.com more so i posted that one bfor here lol im that same guy problem solved thanks for replying tho guys Quote Link to comment Share on other sites More sharing options...
johnc Posted September 28, 2006 Share Posted September 28, 2006 wow hey nismopick i didnt no u wer on here to yeah i use zdriver.com more so i posted that one bfor here lol im that same guy problem solved thanks for replying tho guys Please use punctuation, spelling, and grammer. Quote Link to comment Share on other sites More sharing options...
nismopick Posted September 28, 2006 Share Posted September 28, 2006 and grammer. Grammer? Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 28, 2006 Share Posted September 28, 2006 Grammer? That one gets a lot of people. At least John didn't spell it grmr. The annoying text messaging grammar was only part of what made my head hurt, though. I saw that Steven apparently decided to go with dished pistons, but the reasons for the decision seemed pretty sketchy to me. Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 28, 2006 Share Posted September 28, 2006 I like this post from shady280: i think any turbo motor needs premium fuel, now what if say, you turn it up to impress a buddy or chick, and you got the cheap gas in? kaa boooooom. Speaks volumes about that other forum, at least to me. Quote Link to comment Share on other sites More sharing options...
johnc Posted September 28, 2006 Share Posted September 28, 2006 Grammar... http://www.grammarbook.com/ Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 28, 2006 Share Posted September 28, 2006 Grammar... http://www.grammarbook.com/ blu bk o grmr n pnctn Quote Link to comment Share on other sites More sharing options...
Steven280zx Posted September 29, 2006 Author Share Posted September 29, 2006 Ok ok i shall pay attention to spelling and grammer for this point forward. Thank you for bringing this to my attention. god thats hard! Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted September 30, 2006 Share Posted September 30, 2006 Im going with 8.6:1 CR when I build my turbo engine. that should give me a "snappy" off turbo engine. I don't plan on running huge boost thought, about 12-15 psi. I think 7.4 CR is better for a bigger turbos and higher boost... but im still learning. If I could get one of thoes Giken twin cam heads ... now that could be fun to turbo Quote Link to comment Share on other sites More sharing options...
nismopick Posted September 30, 2006 Share Posted September 30, 2006 Im going with 8.6:1 CR when I build my turbo engine. that should give me a "snappy" off turbo engine. I don't plan on running huge boost thought, about 12-15 psi. 12-15 psi is pretty high on an L28 w/ 8.6 CR. You going studs all around, & MLS headgasket? Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 30, 2006 Share Posted September 30, 2006 Zeiss, what are you doing for fuel management? Quote Link to comment Share on other sites More sharing options...
PETEW Posted September 30, 2006 Share Posted September 30, 2006 12-15 psi is pretty high on an L28 w/ 8.6 CR. You going studs all around, & MLS headgasket? If you build up a L28T motor, you can go with a higher compression ratio. There are plenty of guys on this forum that are running 8:1 compression ratio and putting 400+ to the rear wheels. It is all a matter of building the motor for it, fuel and spark control and a good intercooler. I plan on increasing the compression ratio on my car to kill the of the line dogginess when your not flooring it. Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted September 30, 2006 Share Posted September 30, 2006 15lbs from a t3 is a lot of boost but not compaired to a t4's 15 or 20lbs. I plan on running megasquirt with 440cc injectors and a super efficiant IC I'll start with 7 psi on my my nissan Z31 t3 turbo and see how that go's then i'll slooooooooowly bring up the boost. I have an HKS steel head gasket but If I use it my CR will drop to 8.1:1 so instead of using the steel head gasket I think I will go with studs. I supose that if I go with the 8.1:1 CR I can alway upgrade to the t3/t4 hybrid turbo and get over 350 to the wheels. am I being niev? am I missing something? My goal is 300 to the wheels so once I reach that ill stop raising the boost. Thanks, Matt- Quote Link to comment Share on other sites More sharing options...
LineC Posted October 1, 2006 Share Posted October 1, 2006 I have an HKS steel head gasket but If I use it my CR will drop to 8.1:1 so instead of using the steel head gasket I think I will go with studs. Thanks, Matt- Metal head gasket or studs really isn't a trade off. If I was going all out on studs I would still use the metal HG. Hell I would probaly o-ring the thing honestly. I know bolt stretch might blow out a stock gasket but once there is a real high compression inside the CC it's gonna ruin the stock HG even with studs. Quote Link to comment Share on other sites More sharing options...
TimZ Posted October 1, 2006 Share Posted October 1, 2006 15lbs from a t3 is a lot of boost but not compaired to a t4's 15 or 20lbs. I plan on running megasquirt with 440cc injectors and a super efficiant IC I'll start with 7 psi on my my nissan Z31 t3 turbo and see how that go's then i'll slooooooooowly bring up the boost. I have an HKS steel head gasket but If I use it my CR will drop to 8.1:1 so instead of using the steel head gasket I think I will go with studs. I supose that if I go with the 8.1:1 CR I can alway upgrade to the t3/t4 hybrid turbo and get over 350 to the wheels. am I being niev? am I missing something? My goal is 300 to the wheels so once I reach that ill stop raising the boost. Thanks, Matt- Seems to me that you'd be more likely to be able to live with the higher compression ratio if you went to a t3/t4. Not sure why you'd want to run a higher CR with a less efficient turbo. Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted October 1, 2006 Share Posted October 1, 2006 good point about the gasket... I'm just trying to find that perfect ballance of a snappy off boost engine that will scare the $hit out of people with 12 psi Im guessing that is a magic # of between 8-8.5 CR. Right now I'm driving a 9.2:1 N/A Z and it is quick. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.