turbo

-
SRT_DSTRHOLC

SRT_DSTRHOLC

Well-Known Member
Joined
Mar 20, 2008
Messages
6,468
Reaction score
203
Location
USA
Whats needed to run 7psi max 5psi of boost on a 11.0 compression 360? less compression or lots of octane?
 
In terms of turbo sizing? Not sure what you're asking... Static compression has little to do with boost pressure.
 
jw, why would i need WAY less...if theres other cars running it with 10.5-12..Hondas can do it...drag cars...I need a real answer not way less because I can get info to show you that it can be done but i want to know how

Moper its not a big turbo its the STS turbo
 
Boost is only one part of the equation. Static compression is another. You can put 20psi to an 8 to 1 motor or 5 psi to a 11 to 1 motor. Both are the same right? No not really. the motor with more static ratio will be easier to get on boost and will make more power. When you compress air it heats up, turbos do low boost more efficiently and make less heat. Some folks run a high static ratio and low boost to get around intercooling it. To run a turbo on your current combo on the street you will need some high octane. No big deal if its a street strip, cruise night car where you can fill it up at home and return home without a fill up. Thats what I do. For the cars that are distance runners such as my buddys GN he uses an alcohol injection kit. It only comes on under boost and a 1 gallon tank can last a long time. You will need some dyno time to get it right without killing the motor with a bad tune up. Sometimes the motor can feel okay by the seat of the pants but is really too lean and detonating. Dyno time is a must. Good luck with it and if you need more info just let me know. Obviously there is more to this than a few lines in this paragraph.
 
my dynamic compression is 8.5 and i believe my effective with 5psi of boost is 11-14 to 1 is that do able? We have 110 leaded that i already use to mix with 91 to make 95
 
You using standard felpro head gaskets?They want handle that much compresion and boost without popping.You can do it,but you'll have to run high oct race gas and keep the boost low,dunno how you would add up what oct you would need but theres prolly a calc somewere that'll tell ya what ya need.And you'll need cometic gaskets at the least,they will handle a good bit of presure.STS does make kits for the newer vets and stuff and i know they have a good bit of compresion to start with.Migtht could get a thicker gasket to lower the compresion a bit if ya have to.11.0 is alot of compression with boost,you'd b ok if ya can keep from popping gaskets and keep detnation in check and your block can handle the power.
 
74Burntorange said:
my dynamic compression is 8.5 and i believe my effective with 5psi of boost is 11-14 to 1 is that do able? We have 110 leaded that i already use to mix with 91 to make 95
Click to expand...

Hey Burnt. I'm not really one to add 2 cents to a turbo question. I'm really unqualified, but I do beileve that math above is off on compression and octane need.

I did have a book on turbo charging. I got about half way through it and never opened it back up. I don't think it's for me due to cost and tube set up, dyno time and etc...... issues that come with it.
 
Your CR seemes to have changed since you first asked the question. You can boost almost any CR, but you have to have the equipment that will survive the pressure. Clearly one can cram 25PSI to a 17:1 CR, almost any diesel will do that. However, the variables you don't account for in your OP is cam duration, and actual components in the build.

You should take the advice of the person who told you to contact him with details, AND read up on turbocharging so you can understand and ask good questions. part of your problems may be solved by FI, since this seems to be the way to go. I have a friend with an Andy Jensen twin turbo set up under the hood, and the hp that can be made is insane. However, boost is a big factor in how long the engine lives.
 
how has my CR changed? i have 11.0 compression static and 8.5 dynamic
the cam I have is a 306s magnum solid cam...306 advertised duration and 260 at 50
 
74Burntorange said:
how has my CR changed? i have 11.0 compression static and 8.5 dynamic
the cam I have is a 306s magnum solid cam...306 advertised duration and 260 at 50
Click to expand...
I think you have it backwards, your static compression is your piston configured compression and your dynamic or theoretical compression is with your boost figured in. With an 8.5-1 piston you can easily run 5lbs boost. I have a smallblock all forged internals static comp 9-1 and run 14lbs boost full 35degrees timing. Before I ran an intercooler I also ran water/alky injection no ping on 93 octane, now with the intercooler I don't use the water/alky except in the summer
 
im sorry im trying to listen, but its hard i cant when info is being feed to be thats not true about my setup...Ill just put the turbo on hold...I have to get this motor working first
 
I think you've got the info right. Dynamic is always less than static ratios.

But I'm not sure this is right "my dynamic compression is 8.5 and i believe my effective with 5psi of boost is 11-14 to 1 is that do able? We have 110 leaded that i already use to mix with 91 to make 95"

Dynamic compression is the actual amount of sealed cylinder being squeezed. Dynamic compression will not change until you change something mechanical.. The piston, the cam, the heads, etc. It doesnt care what air pressure (atmosphereic or boost) is acting on things. What you are calling "effective compression" is the cylinder pressure. Not compression. Cylinder pressure takes into account air pressure too. that's why the same engine, when checked at 5K feet will have say 180psi, but at sea level will have 200psi. There's more pressure (atmospheric) pressing the mixture in the hole. But the mechanically compressed volume has not changed. The dynamic will always be calculated to the same thing. IMO, you should be developing an engine for use with boost, or to run NA. There's enough of a difference in parts choices and prep that it makes it rather important to build with boost in mind. Remeber, mild boost on a turbo setup has no parasitic loss like a supercharger. So very low boost yields big results.
 
74Burntorange said:
ya if i have to get new head gaskets again...ill get better one and thicker to lower compression at least to 10...the calculation on the octane isnt wrong from the calculator i used....12.6 gallons of 91 and 3.4 gallons of 110 is 95 http://www.bazellracefuels.com/Calcs/OC1.htm
Click to expand...

It wasn't the octane so much I was thinking about, but more so the ratio's. And then the octane with the numbers. I think them off. I could be wrong, like I said, I'm not really qualified to add 2 cents.

As far as mixing fuels, good link by the way, I myself really haven't had to mix up a brew for a street engine.

Good luck with this project.
 
Boost is neat, but expensive..

BOOST.jpg
 
All this trouble, get a 4bta, put an HX35 on it, big injectors, and have a 30MPG, 350HP, 600 pounds TQ car that runs off of stove oil, veggie oil, drain oil.....

Not to mention you will die waiting for it to wear out.
 
74Burntorange said:
how has my CR changed? i have 11.0 compression static and 8.5 dynamic
the cam I have is a 306s magnum solid cam...306 advertised duration and 260 at 50
Click to expand...

You originally stated 11:1, with no description of static or dynamic, nor any cam specs. Since you gave us the very basics, most of us jumped to the obvious conclusion. Since you then changed the given information, it would be hard to tell you what to do. Which is why I advised you to work with someone who had done it before, AND read up on what you are trying to do.
 
74Burntorange said:
Whats needed to run 7psi max 5psi of boost on a 11.0 compression 360? less compression or lots of octane?
Click to expand...

You don't want to run too much boost on an engine that has a 11:1 compression ratio. If you're running a supercharger you'll want to under drive it, if you're running a turbo you'll want to adjust the wast gate to keep the boost down. I replaced my 10.5: 1 pistons with 8.5:1 pistons when I rebuilt the engine in my car. The supercharger in my car hits about 6 pounds of boost (down from 9 since I changed to a roller cam). Running to much boost on a small block Mopar can cause head gasket failure (don't ask how I know this)LOL
 
I am sure everyone has been waiting to see what I have to say on the subject.....and here it is:

Yes you CAN run a turbocharger or two, or three or four on a engine with 10:1 and above Compression Ratio.

You can run whatever compression ratio you want up to 14:1 on Gasoline.

What you cant do is expect to bolt a turbo system on a 11:1 CR SBM, and ever run pump gas....even on 5-7 psi.....well I guess your could but I dont recommend it.

I understand Water Injection, and believe it to be a viable way of reducing intake temps, detonation AND providing a way of utilizing forced induction on a "higher" than recommended compression engine......But I do not condone the recommendation to anyone who does not fully know what they are getting into.

When talking about turbochargers, and increasing performance while wanting some lifetime out of it.....I highly recommend a 7.5-9:1 CR for longevity, performance, and tuneability.

A MLS (multi-layer steel) head gaskets Such as this:
http://www.cometic.com/da_viewimage.aspx?da=297

&

ARP Head Studs

Should be considered a requirement when considering forced induction.

Find a Bone Stock 360 Longblock to pop and try out while you go through your built 360 block......my .02
 
You must log in or register to reply here.
-

Back
Top