Here's my dilemma. I'm looking to build up my D16Y8 in the future to support 300whp on the Greddy 19T SOHC turbo. It's told by greddy to support at least 300whp. here's how I plan to get there:

-Greddy 19T kit
-Greddy Type 31 intercooler
-Greddy Type-S BOV
-RC 440cc or 550cc injectors, saturated (probably 550's for 300whp)
-AEM EMS system, dyno tuned (I'd do serious shopping for a good tuner first)
-NGK BKR7E's, gapped at .030"
-Apexi AVC-R boost controller
-Open 2.5" or probably 3" downpipe (for 300whp @ 15 psi) - either Super-T or Autologic
-3" test pipe -> 3" piping
-ACT XTSS clutch kit w/XACT flywheel (not sure whether to stick w/stock or lightened)
-Quaife LSD (not relevant to HP, but for the 1/4 mile time)
-JE pistons/Crower rods/GE blockguard (Can't decide what comp. ratio, see my other thread regarding compression vs. boost level in a minute)

Now the only issue I foresee is the compression ratio. I see most guys on H-T pushing the 9:1 comp. ratio so you can run more boost. Okay that's fine, but this turbo maxes out at 300whp@ 15 psi, just like the 15G that I already have maxes out at 250-260whp @ 15 psi. So what I'm wondering is why don't I run stock compression (9.6:1) with forged internals or even 10:1 compression to build more horsepower at the same boost level? I guess it's really confusing to me (the concept of HP vs. boost level vs. comp. ratio).

For example, some of the race guys are running 8.5:1 comp. and pushing 30+ psi. Now what I'm wondering is why can't (assuming the motors are fully built) these guys, or why wouldn't they want to run a higher comp. ratio (i.e. 9.5:1 or even more) to make more HP at the same boost level. Is it done (running lower comp.) to actually have lag off the line so that they can hook with FWD?

Educate me, because this topic is Greek to me.

 

Search

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bryson &raquo;</TD></TR><TR><TD CLASS="quote">Search</TD></TR></TABLE>

Oh Lord, thanks for the help!!! Now I know exactly what setup to run!!! You're the best!!!

*Back to reality* I did search, but couldn't find anything helpful.

Thanks

 

im sorta in the same situation.
But my main reason to choose a 10:1 ratio is because i daily drive my car and with very lil lo end i have already id like to keep it. Plus with a standalone and conservative t00ning i would be able to be safe.

i guess its all your preference, but like u said since the greddy turbos max out around 1 bar if you start with a low compression motor 8:1 or 9:1 then turning it up wont grant you the HP you need to reach your goals.

 

at a local nhra sport compact i went to the past year i asked pretty much the same question, "whats better, high comp+low boost or low comp+high boost?" i asked a dodge guy and he said low comp+ high boost=more hp. thats all he told me and i know nothing else.

 

higher compression yeilds more low end power, but you can't run as high of boost due to detionation. Lower compression yields the oppisite

 

low vs high compression

 

This is a constant arguement around the shop..... basically, here's my position, think of the combustion chamber as a box, the higher the CR gets, the smaller the box, the lower the CR teh bigger the box. SO, with a large box, you can cram a lot more crap into it right, the smaller box, not so much, same goes with fuel and air, the larger the "box" the more air/fuel you can shove in there (turbos are designed to do this) the smaller the box, the less air/fuel you can put in there..... air/fuel make combustion which makes power, so in the end, you can make more power if you can combust more fuel, with more air........ the only downside to this.... going back to the box, is that the smaller box gets going a lil faster, so you would loose a small amount of low end....... they fixed that problem too however....... its called nitrous...... spoolin turbo's faster since... whenever someone tried......

hope this helps

 

that is a great way of putting it.

 

We are happy running 10:1 and 28psi on a built B18C. Good power on the street before boost and awesome power when the turbo spools.

 

I dont agree with the box theory. high or low compression pistons, the displacement is still the same therefore the box (combustion chamber) is the same size.

My theory uses cylinder psi, which is a result of volume of air * compression. cylinder pressure is directly proportional to power output. high boost * low compression = x cylinder psi and low boost * high compression could also = x cylinder psi. I think somewhere there is a magical equation that could prove my theory but I dont know of it. Of course Im talking out my *** too.

 

well i dont know.
i think if its a daily driver and thats all its going to be. If your not looking for HIGH HP. run high compression with low boost i think it would be great daily driver. im running 10.4:1 compression with my setup.
If you trying to be a good GO HAPPY BOOSTING kinda guy, then go for 9.5:1 and boost that ****** til it blows. i use the same mind set when lifting weights to get big or to CUT.
High compression=low boost
Heavy weight=less reps
Low compression=high boost
Less weight=more reps.

 

I agree its a trade off but I think a mix of either one can yield you the same results. I wish I had a way to prove/disprove this.

Im half inclined to build my motor with 10:1 CR and shoot for 400whp with my SC34-E

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rickyh93 &raquo;</TD></TR><TR><TD CLASS="quote">We are happy running 10:1 and 28psi on a built B18C. Good power on the street before boost and awesome power when the turbo spools. </TD></TR></TABLE>

what octane?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boostincoupe &raquo;</TD></TR><TR><TD CLASS="quote">

Oh Lord, thanks for the help!!! Now I know exactly what setup to run!!! You're the best!!!

*Back to reality* I did search, but couldn't find anything helpful.

Thanks </TD></TR></TABLE>

Your welcome

 

get higher compression, 9.0.1 - 10.0.1, you wont be disapointed. if you having it tunned i would go with the 10.0.1.

i run 8.5.1 and gotta keep my **** a 4000rpm or my car blows. the next engine i build will not be this low.

platinum.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by platinum00 &raquo;</TD></TR><TR><TD CLASS="quote">i run 8.5.1 and gotta keep my **** a 4000rpm or my car blows. platinum.</TD></TR></TABLE>

huh? Why would your car blow? are u saying you can't go above 4000 or what? Why would it blow?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Cyphear &raquo;</TD></TR><TR><TD CLASS="quote">

huh? Why would your car blow? are u saying you can't go above 4000 or what? Why would it blow?</TD></TR></TABLE>

my guess is he means the power is so shitty, it "blows" to have the rpm's under 4k. (due to the low compression)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">I dont agree with the box theory. high or low compression pistons, the displacement is still the same therefore the box (combustion chamber) is the same size..</TD></TR></TABLE>

I have to somewhat dissagree there. In my case i had my JDM ITR pistons in my motor for like 4 months, then removed and got a bore and hone and **** done and installed my CP OS 9:1 pistons, and ill tell ya that the combustion chamber is definetly larger now than it was before, the ITRs had a large dome as now there is none, and the slight overbore achieved more area also. I know the bore is not everyones case but lowering the compression ratio does also increase the size of the "box".

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by spoolinlude &raquo;</TD></TR><TR><TD CLASS="quote">This is a constant arguement around the shop..... basically, here's my position, think of the combustion chamber as a box, the higher the CR gets, the smaller the box, the lower the CR teh bigger the box. SO, with a large box, you can cram a lot more crap into it right, the smaller box, not so much, same goes with fuel and air, the larger the "box" the more air/fuel you can shove in there (turbos are designed to do this) the smaller the box, the less air/fuel you can put in there..... air/fuel make combustion which makes power, so in the end, you can make more power if you can combust more fuel, with more air........ the only downside to this.... going back to the box, is that the smaller box gets going a lil faster, so you would loose a small amount of low end....... they fixed that problem too however....... its called nitrous...... spoolin turbo's faster since... whenever someone tried......

hope this helps</TD></TR></TABLE>


exactly..... boost pressure is irrevelant, its all about volume.. the more air you can get into and out of an engine the more power you're gona have. its all about flow..

the reason evo's take so much boost to make the **** for power they do is mainly b/c of the head and the cams. with just a couple of boltons and tuning with the aem ems we got the last eveo we did up to 303hp and 315tq.. could be more, but we ran out of time on the dyno... there are people with the same setup but with hks 272 cams.. (around 11ishmm lift and 240ish duration at 1mm) they make in the area of 400 on a wheel dynos at 21psi... thats gettin there. it has also been found that the exhaust ports on evos are trash, they suck compared to older 4g63's. get the head fixed and your gona be at 450hp with 20-23psi on the stock turbo. thats right in line with what most big turbo hondas do... and its a shitty little 16g.

you have to remember.. all engines do is move air.. the more air you can cram into an engine and effectivly get out of the engine the more power its gona make. lower compression allows you to do this. also rember its power that stresses an engine, not boost pressure. 300hp is 300hp be it at 3psi or 50psi.

 

I plan on running 10:1 C/R and boost. My tuner feels confident we will get at least 300whp on pump gas, but we are going to try for 350whp.

 

wat boost levels u planning on running?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bryson &raquo;</TD></TR><TR><TD CLASS="quote">Search</TD></TR></TABLE>

It would be great if people like you actually helped, instead of being a ***** about everything. Seriously, your post didn't help him at all, so why even bother commenting other then to be an ***?

 

You guys are arguing the wrong points...What we really are talking about is dynamic compression ratio and cylinder pressure. The main thing that keeps us from running 10:1 and big boost is 91-93 Octane. If everyone ran race gas this wouldnt even be a debate. But alot of you are cheapasses and will spend $10,000 on your motor\turbo setup, but will wanna tune it with AFC\FMU and run 87 Octane. For this type of person, I recommend 8.5-9:1 Compression for the simple fact that the tuning window is larger and you can run more boost\timing on pump gas.

 

Oh yea, for your setup I would run 9:1...Its all about dimishing returns.

What you gain power\response wise from 9 to 10:1, wont outweigh the difference in say going from 10 to 15 PSI. Those numbers are examples.

Suprdave