compression ratio vs forced induction

[tortzorz]

lets say u have a car with compression ratio 10;1, running 1bar
does that make the effective compression ratio 20:1? (obviously a little less due to heat etc) but is that what happens?

how come turbos can run such high boost?
if running 1 bar = doubling the compression ratio, wouldnt they detonate?
or that what an intercooler does, essentially bring the heat down to a level comparable to say 11:1 or whatever compression ratio would correspond to no detonation

and lastly, on old turbo cars with no intercooler, arent u just effectively trading off CR for boost?

e.g if u had 2 models of car, one turbo and one n/a
the turbo had CR of 8.5:1, the n/a 10.5:1
since theres no intercooler, wouldnt the amount of boost u can run depend directly on heat/compression?
so if u culd run a maximum of 10.5:1 on the n/a before detonation, wouldnt the amount of boost u can run develop 10.5:1 dynamic compression before detonation?

i understand that forcing air into an engine is better than drawing it in becoz of decrease of fuel:air ratio and stuff
but is that the only advantage? i would think turbo lag would b a big enuff disadvantage to offset that forced air advantage

EDIT:
{
e.g u have a 10.5:1 CR n/a 300zx, 168kW
u have a 8.5:1 CR TT 300zx (lets say uve removed the intercoolers) running X boost
wot would the X be before u get detonation? like 7psi? the power for an n/a Z with 8.5:1 CR would b a fair bit lower than 168kW
if running X boost brings the power up over 168kW but doesnt cause detonation, y doesnt the n/a just run higher compression?
}
plz feel free to elaborate on ur explanation if ive left anything out or u just want to speak ur mind, were all here to learn

btw this is a repost, i posted this in 'cars in general' too

[Zgringo]

Originally Posted by tortzorz

lets say u have a car with compression ratio 10;1, running 1bar
does that make the effective compression ratio 20:1? (obviously a little less due to heat etc) but is that what happens?

how come turbos can run such high boost?
if running 1 bar = doubling the compression ratio, wouldnt they detonate?
or that what an intercooler does, essentially bring the heat down to a level comparable to say 11:1 or whatever compression ratio would correspond to no detonation

and lastly, on old turbo cars with no intercooler, arent u just effectively trading off CR for boost?

e.g if u had 2 models of car, one turbo and one n/a
the turbo had CR of 8.5:1, the n/a 10.5:1
since theres no intercooler, wouldnt the amount of boost u can run depend directly on heat/compression?
so if u culd run a maximum of 10.5:1 on the n/a before detonation, wouldnt the amount of boost u can run develop 10.5:1 dynamic compression before detonation?

i understand that forcing air into an engine is better than drawing it in becoz of decrease of fuel:air ratio and stuff
but is that the only advantage? i would think turbo lag would b a big enuff disadvantage to offset that forced air advantage

EDIT:
{
e.g u have a 10.5:1 CR n/a 300zx, 168kW
u have a 8.5:1 CR TT 300zx (lets say uve removed the intercoolers) running X boost
wot would the X be before u get detonation? like 7psi? the power for an n/a Z with 8.5:1 CR would b a fair bit lower than 168kW
if running X boost brings the power up over 168kW but doesnt cause detonation, y doesnt the n/a just run higher compression?
}
plz feel free to elaborate on ur explanation if ive left anything out or u just want to speak ur mind, were all here to learn

btw this is a repost, i posted this in 'cars in general' too

First off compression is how a engine makes power. Without compression it's like pouring gas on the ground, it just sit's there and burns.The higher the compression the higher the power. Cams, porting, tuned exhaust, bigger throttle body's, turbo's, superchargers ect.ect. all these tools assist in putting more air into the engine. Now we come to the compression ratio. The compression ratio is the multiplacation factor burning gas makes under pressure on the top of the piston.
Here's a example. You have 3 engines:
#1 N/A with 16:1 compression ratio
#2 supercharged with 10:1 compression ratio and 10# boost
#3 supergharged with 6:1 compression ratio and 16# boost
All things being equal what's the difference in these 3 engines and power out-put? Nothing, nada, zip. There all the same.

http://www.goodvibesracing.com/Compression%20Ratio.htm

Now we all know you can't run 16:1 compression ratio with the gas we have at the pumps, so in order to run this we have to use racing gas, alky or retard the timing or other steps to prevent detonation.
Engineer's knowing the importance of compression ratio and knowing if you put more air into the combustion chamber of a engine you raise the compression ratio and increase the power. Now we have the age of the turbo's and superchargers, plus computers and aftercoolers to control the boost. timing and to keep the inlet air cool and keep the engine alive.
One problem with Turbo's is the 8:1 compression ratio designed into the engines. Till the turbo makes enough boost to raise the compression ratio you have no power. It's called turbo lag. You can put smaller turbo's that spool-up faster but lose top end power, or use larger ones and lose the bottom end. Your choice.
One way to overcome this is to run higher static compression ratio, say 10:1 and less boost. The problem doing it this way is you need to know what your doing so you don't turn your engine into a bomb.
If you run ADI or water/alky injection you can run unGodly amounts of boost. With this and Toluene you can run 5 bars boost and make 1000HP per liter if the engine internals are strong enough.

http://performanceolds307.tripod.com/id9.html

The reason engineers installed intercoolers which are not the best but kinda do the job is they knew people are lazy and wouldn't keep there water/alky bottle full and they'ed have a problem with blown engines. Water/alky is 10 times better than a intercooler ever dreamed of.

http://www.geocities.com/rad87gn/tech/alcohol.html

Drawing air into a engine ISNT any better than blowing it in, it just allows you to make more compression than one not blown.
There's lot's of old belief's that are just that, old belief's. They have no merit and don't apply to the engineering knowledge we have today.

If it wasn't for insurance companys and the NTSB we'd have cars in the 300MPH range by now running on panther piss.
There looking out in our best interest and protecting us from the evils of a modern high performance car. Go to Europe and look at the toys driven everyday not allowed in the USA. Thanks to our great leaders they let us have a choice of what they choose and direct the auto mfg. on what they can build.

[JCCR]

The reason engineers installed intercoolers which are not the best but kinda do the job is they knew people are lazy and wouldn't keep there water/alky bottle full and they'ed have a problem with blown engines. Water/alky is 10 times better than a intercooler ever dreamed of.

SO INSTEAD OF UPGRADING MY INTERCOOLERS I SHOULD JUST BUY A WATER INJECTION. WHATS MY HP GAIN ON THIS UPGRADE?

[Zgringo]

Originally Posted by JCCR

SO INSTEAD OF UPGRADING MY INTERCOOLERS I SHOULD JUST BUY A WATER INJECTION. WHATS MY HP GAIN ON THIS UPGRADE?

It's not what's the HP gain with a water/alky is, but what your able to gain with a water/alky upgrade. You'll be able to go to boost's beyond any (within reason) intercooler ever dreamed of.
In a street car 99% of the time is spent normal driving. It's that 1% time were interested in. You could setup your car to handle 1000HP but drive it normally with say 400HP, flip a switch (for that special time) and have 1000HP. Why strain your engine all the time, plus it well last longer.

[tortzorz]

wow excellent post Zgringo heh *bow*

one question that u missed was
if u have an n/a car with 10.5:1
and a turbo car without intercoolers are 8.5:1 but ur able to get higher power than the 10.5:1 engine because of higher boost
why not just run a higher compression ratio in the 10.5:1 car?
if its exactly the same thing then u wont get detonation right

[Zgringo]

Originally Posted by tortzorz

wow excellent post Zgringo heh *bow*

one question that u missed was
if u have an n/a car with 10.5:1
and a turbo car without intercoolers are 8.5:1 but ur able to get higher power than the 10.5:1 engine because of higher boost
why not just run a higher compression ratio in the 10.5:1 car?
if its exactly the same thing then u wont get detonation right

With a race only engine not a problem, but with a street engine you want the best of both worlds. A mellow hi-performance engine, but when the green flag drops, flip a switch, and the bull shit stops. Full blown racer.

[tortzorz]

hrm
how bout the cordia right
the stock n/a 1984 leaded cordia was 90kW
the stock turbo 1984 leaded cordia was 110kW

it had no intercooler, and u culd usually turn the boost up a little more without changing anything (just fitting a boost controller)

so is there any reason the n/a is so gutless compared to the turbo? if the turbo was 110kW with room to spare, is there any reason they didnt tune the n/a for 110kW?

and how come dyno tuners tweak CR and boost levels to make an optimum combination
if CR and boost essentially create the same thing, wouldnt there be a certain temperature, X, where detonation happens?
so if u lower CR and increase boost and reach temperature X, wouldnt it create identical power than if u increase CR and decrease boost and reach temp X?

[Zgringo]

Originally Posted by tortzorz

hrm
how bout the cordia right
the stock n/a 1984 leaded cordia was 90kW
the stock turbo 1984 leaded cordia was 110kW

it had no intercooler, and u culd usually turn the boost up a little more without changing anything (just fitting a boost controller)

so is there any reason the n/a is so gutless compared to the turbo? if the turbo was 110kW with room to spare, is there any reason they didnt tune the n/a for 110kW?

and how come dyno tuners tweak CR and boost levels to make an optimum combination
if CR and boost essentially create the same thing, wouldnt there be a certain temperature, X, where detonation happens?
so if u lower CR and increase boost and reach temperature X, wouldnt it create identical power than if u increase CR and decrease boost and reach temp X?

I wasn't confused till I read your post, but I think I kinda know what your trying to say.
When you compress air it makes heat. Boost only create's heat and raises the compression ratio. You have two things working for and against you. Heat and compression. Both can be overcome with proper cooling of the inlet air temp. fuel octane and proper timing. Put everything in it's proper place and good things happen, fuck-up and guess what? Your fucked.

[Turbo711]

Compression ratio is how much your engine squeezes the air and fuel when the engine is on it's compression stroke, just before the spark plugs fire. Boost is the pressure that the turbo makes to force air into the cylinders. they are way different, and no the engines would not make the same power, but would have totally different power bands, as more coompresssion less boost = more low end power, and less compresssion more boost= more boost lag and high end power.

[Zgringo]

Originally Posted by Turbo711

Compression ratio is how much your engine squeezes the air and fuel when the engine is on it's compression stroke, just before the spark plugs fire. Boost is the pressure that the turbo makes to force air into the cylinders. they are way different, and no the engines would not make the same power, but would have totally different power bands, as more coompresssion less boost = more low end power, and less compresssion more boost= more boost lag and high end power.

Everything in this statement is false,, unbelievable the garbage that comes out peoples mouth's.
#1 if you didn't even have a fuel/air mixture or spark plug in a engine it's called a compressor and it does have a compression ratio. Compression ratio is the area left by the head with the piston at TDC.
#2 Boost is the amount of air forced in the engine above 14.7lbs or 0 bar. without any boost (pressure) it's nothing more than a fancy fan moving air. The compression ratio is the determining factor of a engines performance. Low CR low performance, high CR high performance. By forcing air into a engine under pressure you've increased the CR.
Now I don't care if you have 30# boost, 5# boost or no boost, the compression ratio (multiplication factor) of a engine is amount of energy placed on top of the piston creating power (energy).
A engine with 8:1 pistons and 14.7lbs boost will have a final compression ratio, FCR, of 16:1
A engine with 12:1 pistons and 7.3lbs boost will have a FCR of 16:1
And a engine with 16:1 pistons will have a FCR of 16:1
Now if you use a 13:1 fuel/air mixture and place it in a combustion chamber with a 16:1 compression ratio and fire that mixture, you'll have a 16:1 multiplication factor to figure the amount of energy developed. and I don't care how you arrived at the CR it's 16:1 and thats it.
Now the 16:1 piston engine would be great for racing, but for normal drivers totally uncontrollable.
The 12:1 piston engine boosted to 16:1 would have great low and mid range with the added benifit lots of power at top end, but border line for most drivers.
Now comes our normal everyday 8:1 engine boosted to 16:1. Bottom and mid range power lacking but topend equal to the above engines, one that grandma could drive.
Because Turbo's don't start building pressure to increase the CR till the engine reaches approx. 3,000RPM we have what's called turbo lag. In realitity the poor engine with 8:1 pistons with no boost just doesn't make much power without the boost to increase the CR. For Grandma this is OK cause we don't to scare the shit out of her, but to some, they, we want better, so we play the turbo game to get them to produce boost at a lower RPM, or inject nitrous in the low RPM ranges in attempts to get rid of this so called turbo lag.
With the introduction of computers in cars great things have happened, and a computer controlled car in the right hands were looking at a car with 1,000+HP per liter with just a flip of a switch, and could still be driven on the street. Why and how would this be possible, well with proper timing, the right fuel and 73.5# or 5 bars boost fact, and all with just a flip of a switch and a little black box under the seat.

Someone came across a web page that described various DIY home brew octane booster formulas. One of which used toluene as its main ingredient. As a Formula 1 racing fan of many years, I recalled that toluene was used extensively in the turbo era in the 1980s by all the Formula 1 teams. The 1.5 liter turbocharged engines ran as much as 5 bars of boost (73 psi) in qualifying and 4 bars (59 psi) in the actual race. Power output exceeded 1500bhp, which translates into 1000bhp/liter, an astronomical figure.

A motorsports journalist, Ian Bamsey, was able to obtain Honda's cooperation for his book "McLaren Honda Turbo, a Technical Appraisal". The book documents the key role that the toluene fuel played in allowing these tiny engines to run so much turbo boost without detonation. The term "rocket fuel" originated from the Formula 1 fraternity as an affectionate nickname to describe its devastating potency. Thus I concluded that I should focus my research on using toluene for my octane boosting project.

In closing Turbi711 please come here and learn and provide feed back on what works and how you apply it and who's ass you smoked, but don't come here with BS and provide false crap.

Albert

[Hodo]

Compression Ratio= Stroke X Bore X diameter. Although its been forever since I tried to remember that, I am probly wrong on the equasion but thats about how it sums up. There is a further calculation for adding boost and figuring in the boost pressure in Bar or Pounds, I perfer Bar, but I cant remember it knore am I going to try, I know it was a good sized chart for it.

Or its Bore X Diameter / Stroke........ or something like that. Man I am having a brain fart today.

And as far as Zgringo dont worry about him he's old and sometimes he gets off his meds and gets kinda mean. LOL But he is right careful what you say here becuase we will come down on you hard if you are wrong. More so with Zgringo (AKA George)

Most of the time in day to day activity I am the ass, but on here I let George do it for me.

[Zgringo]

Originally Posted by Hodo

Compression Ratio= Stroke X Bore X diameter. Although its been forever since I tried to remember that, I am probly wrong on the equasion but thats about how it sums up. There is a further calculation for adding boost and figuring in the boost pressure in Bar or Pounds, I perfer Bar, but I cant remember it knore am I going to try, I know it was a good sized chart for it.

Or its Bore X Diameter / Stroke........ or something like that. Man I am having a brain fart today.

And as far as Zgringo dont worry about him he's old and sometimes he gets off his meds and gets kinda mean. LOL But he is right careful what you say here becuase we will come down on you hard if you are wrong. More so with Zgringo (AKA George)

Most of the time in day to day activity I am the ass, but on here I let George do it for me.

Hodo it's Albert and when I'm off my med's I'm a MOFO. As for your math close for the kinda gals we go with. Your fomual is great for figuring the cubic inch displacment of a engine. For compression ratio use the following:

http://e30m3performance.com/myths/mo...comp_ratio.htm

This is much easier to use, less strain on the fuckin brain matter.

http://www.goodvibesracing.com/Compression%20Ratio.htm

Your right Hodo, When someone makes a statement and gives facts to back it up, then another comes along and says it's crap, I'll hand them their lunch. If you or anyone is right I'll back them to the end, and if their wrong I'll correct them.
I figure this is a place to learn and share experiances and pass along information to people with the same interests, But when shit is being passed on I'll do my best to correct it so those who don't have the knowledge don't get cluttered brains.
Besides picking on you is more fun than smashing my thumb with a hammer. Any Black guy that own's a 300ZX that lives in Mooresville, N.C. can't be all bad, but you get my name wrong again, I'll burn your barn down, paint your car green and hide it in the grass so you can't find it.

Albert

[Hodo]

LOL, sorry it was like 4AM and I was about to sleep.... Yea his name is Albert.... BTW my car is already green and hard enough to find if I park in the yard. :P

I was giving Cubic displacement..... wow no more posting before bed time!

Alberts right though, he is a stickler about being right and wrong, and I agree with him most of the time. Except on the meds part.....I like no meds, life is too much fun to not piss someone off a day.

[Zgringo]

Originally Posted by Hodo

LOL, sorry it was like 4AM and I was about to sleep.... Yea his name is Albert.... BTW my car is already green and hard enough to find if I park in the yard. :P

I was giving Cubic displacement..... wow no more posting before bed time!

Alberts right though, he is a stickler about being right and wrong, and I agree with him most of the time. Except on the meds part.....I like no meds, life is too much fun to not piss someone off a day.

What about your barn? And what the hell you doing up at 4AM anyways? You don't have to agree with me about the best car, or or it's color or what music you like, that's personal and open for debate, but when it comes to technical shit better have your ducks in a row.
I don't do med's myself, if they depended on me for support, they'ed all go broke.
I piss people off without trying, but that's life.

Albert