I need to know a good compression ratio to let my engine live a reliable life I was thinking 8.2:1?? or is that too low?
BTW this is with a 3 core intercooler if it makes a diff.
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aka:15 year old camaro freak
owner of a 91 z28 5.7l camaro
Cross Drilled Brakes, KYB's,AFPR, 3.73 Gears, Trans Go Shift Kit, 2k Stall, B&M Rachet Shifter, Borla Adjustable Cat Back, Hypertech Chip, Hooker Headers.
more to come....
My 91 Z28

[This message has been edited by Chris Etemadi (edited October 05, 2000).]

 

Chris,

I wish I had a definitive answer for you, but I don't know either. I can tell you that I will be running a D1SC with 15 psig boost at 6,000 rpm with an 8.8:1 compression ratio on aluminum heads. I will have the three-core IC and in addition, I plan on using water injection. I will be using stock 19# injectors without an FMU. Instead of the FMU, I will use the Carroll Superfueler system, but only if needed. Imperical data will tell me if the Superfueler is needed once I have this compressor installed (December).

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Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous).
http://www.ozemail.com/au/jca69/mods/williesz/willie.html

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

[This message has been edited by Willie (edited October 06, 2000).]

 

8.5 to 1 is fine for intercooled chargers/turbos to about 20psi. So 8.5 for 16 would be great because if something bad happens, you have a slight tolerance for mistakes if they occur.

More motor, less boost. that is what i say.

 

thanks guys

 

Most of the import racers are running 10:1 or greater compression and mondo boost. How? It's all in the tuning, air charge temp and combustion chamber design. Every engine will be different, even 2 engines that are "identical".

Just be sure to use the biggest intercooler you can fit, make sure the fuel system is up to snuff for the HP levels you're producing and have some sort and use a knock detection device like the J&S Safeguard. Crank up the boost and watch the timing, when you start to get signs of knock back it down.

Rob_O

 

Sorry, not possible. Unless they are running race gas and a big water-to-air intercooler. Doesn't matter how rich you would run the motor, you'd detonate. Ask the guy who is selling his lt1 procharged z. he is running 11.0 to 1 and 20psi. He HAS to run VP116 AT ALL TIMES and is extremely hard to tune.

 

Can't be done...

Then go down to your local NHRA national event and tell them there's no way they can run over 200 MPH in the 1/4 mile... or tell them there's no way to build an engine that will handle 100% nitromethane

Then go down to the local Nascar track and tell them they'll never make as much HP or run as fast as the old, big inch engines could.

Be sure to hit the track at indy... Tell them that track will never see a car go around it at 200 MPH... or 210... or 220...

Also, be sure to tell all those guys building and testing engines that there's just no more horsepower to be found. We've reached the end of the development cycle and they're just wasting time and money.

You are exactly right in that you can't just throw a blower on any old engine and expect to be able to run unlimited boost with no problems. It's all in the combination and that combination includes internals as well as tuning. But don't say it can't be done

Rob_O

 

Well this guy isnt going to be able to run 10:1 compression with 16psi and live. At least not without a DFI or someting to back the timing way down when it hits higher boots levels.

 

Hell anything can be done,but is is practical?Running 116 on the street will eat up your whole paycheck.I think the main question here to answer is why do you want to run 16lbs on what motor and what combo?What are you trying to acomplish?Running the 1/4?Top speed trials?Corner carving?Rob O you can jump out of a plane without a parachute,but is it practical?No,it isnt.Either is running 10.1 on the street with 16lbs of boost.Those import guys run race gas,thats what that combo calls for.And those motors are high matience items.To run that much boost for talking purposes the limit on pump gas with some kind of intercooler would be no more then 9.5 to 1,with conservative timing.
And something about the tuning,at 16lbs of boost,when you get knock its ususlly too late to back it down,you will have to replace head gaskets and or repair the motor.Use race gas to tune at all times.

Rob O,I find your references amusing,yes drag cars can handle 100% nitro,but you failed to mention the motors are rebuilt after ever run,a ****load of spare motors and parts are always kept handy,because these motors quite frequently **** their pants down the strip.I was talking to a crew member of one top fuel team at World of Wheels in Boston this year,I asked about the cost of a motor if it does ****,and they ususally do,cost is a staggering $60,000 a motor,he told me they once went through 6 in a weekend,do the math,if you aint got the cash you wont be playing anymore.Same goes for this setup,not everyone is made of money to do one offs to see if you can do it,its too dam expensive to experiment if something goes wrong,but go ahead if you have sponsers to back you Anything can be done,the limiting factor isnt knowledge or expertise,or the strenght of availible parts,the limiting factor that restrains us all is the greenbacks.No one works for free,time is money,motors cost big amounts of $$$.That is what limits us all.Imagine where we would be in this sport if money was not a big factor.I can only dream

 

Well the 16 PSI Is for a 355 4 bolt main AFR 190 64cc heads and superram. so I guess I will go for around 8.5:1
thanks for all the input!!

------------------
aka:15 year old camaro freak
owner of a 91 z28 5.7l camaro
Cross Drilled Brakes, KYB's,AFPR, 3.73 Gears, Trans Go Shift Kit, 2k Stall, B&M Rachet Shifter, Borla Adjustable Cat Back, Hypertech Chip, Hooker Headers.
more to come....
My 91 Z28

 

Notice how i never said IT CANT BE DONE. there is an unless in there. almost anything is possible i am not disputing that. i am not trying to brag but i know a lot about blowers and have done the reasearch to prove it. All that i meant is that you cant just go and make any combo you want. Sure you could and have it tuned right, but that doesn't mean that it is the right combo or even the correct thing to do. 10:1 compression and lots of boost (over i would say 12psi is too much) You would have to run race gas, a huge intercooler, and back off the timing. Now let me ask you a question, what is the sense of having an intercooler if you are going to back off timing? Sure you can quell detonation by race gas and piston coatings and the like, but it will never actually stop it. Also combustion chamber does not have as much to do with it as you think. A good combustion chamber is made to develop complete combustion quickly for maximun hp. No head manufactuer i know of specifically makes heads for blowers. Sure they put big fat decks on them and say they are blower heads, but that is all. i am not trying to offend or flame you, i am just stating facts.

Also, to 89PROCHARGEDZ, thanks for adding some insight to this topic. It was you who got me involved all of this blower stuff in the first place. One great example that i can give that makes tremendous horse and has the right tune are top fuel cars. Did you know that they run ONLY 4:1 OR 4.5:1 COMPRESSION AND 40-44LBS OF BOOST? AND THAT THEY TEFLON COAT THE BLADES ON THE ROOTS FOR MAXIMUN EFFICIENCY? They too stick by the chart for compression vs boost allowance. but since they run on nitromethane, they can strecth it a little bit.