Thinking out loud: 3.6L V6DI - Page 2 - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

*TAG UR IT* · 05-17-2008, 02:53 AM

Quote:

Originally Posted by AirGoya

O ok, thanks both of you.
Dragon, you could be right about the forced induction idea. In the other engine thread about Gen V engines, asrapid mentioned rumors of GM making a turbo V6 with over 400hp. EXCITING!

As long as my turbo 6 has pull all through the power band, I'll take it any day. No lag....no time to spool up...I'll take it. 400hp?? Hell yeah...from a 6??

LS9CamaroSS · 05-17-2008, 02:59 PM

Quote:

Originally Posted by TAG UR IT

As long as my turbo 6 has pull all through the power band, I'll take it any day. No lag....no time to spool up...I'll take it. 400hp?? Hell yeah...from a 6??

Imagine what you could do with some major modding... Remember the Supra? Can you say 900+ HP out of a low displacement V6?!?!?!?!?!?!

*Mr. Wyndham* · 05-17-2008, 04:10 PM

Thanks for all the input guys.

There stands a good chance I get the V6 model over the V8. Not positive, yet - but the chance is there. So: I hope the aftermarket embraces this engine just as much as they do the V8.

aldaron327 · 05-17-2008, 04:21 PM

Quote:

Originally Posted by LS9CamaroSS

i'm hearing about how all this injection correlates to the compression ratios being so high, but the 1970's SS engine the L-78 and it had a carb on it... this engine achieved a compression ratio of 11.0:1 so what does the better atomization of the fuel have to do with the compression ratio?

I think it's mostly to do with the internals, but I haven't researched it much. Let me get back from Leave and finish my annual checkride studying and I'll do some research and get you a good answer. Until then, I can only give you the Joe Dirt Answer: "How's a rainbow made? How's the positrack on a Plymouth work?! IT JUST DOES!!!!" Hehe.

27 and a wake-up!

-Tim

frankfan42 · 05-17-2008, 10:50 PM

Some of your thoughts on direct injection show good analysis- compression ratio is a volume related measurement, it is the ratio of volume remaining in the cylinder between when the piston is at the top of the stroke compared to the bottom of the stroke. In simple terms: If a cylinder contains 11 cubic inches at bottom dead center (the bottom of piston travel) and compresses it to one cubic inch at top dead center ( top of piston travel) then compression ratio is 11:1
All other things being equal then an engine with higher compression will yield more power and efficiency than one with lower compression. Several factors restrict higher compression ratios- primarily "Knocking" which can destroy an engine if not controlled. Higher octane fuel does not have more BTU energy per unit volume, but a higher quantity of antiknock additives which will control this damaging phenomenon. In the 60s some street strip engines had compression ratios up to 14:1. Ratios were lowered starting with the 71's as most of the early emission systems could not cope with the higher levels of oxides of nitrogen which tend to form when combustion temperatures are higher, as with a higher compression ratio. Modern combustion controls and catalysts have allowed compression ratios to be increased again.
Direct injection helps to control "knock" by being a finer mist which cools the intake charge significantly. Hope this helps- sorry about being so wordy.

*TAG UR IT* · 05-18-2008, 12:36 AM

Quote:

sorry about being so wordy

No! Thanks! Good information, there!

*CamaroSpike23* · 05-18-2008, 07:02 AM

just to bump on what frank said about the 60s and high CR's, dont forget leaded gasoline allowing higher CR's during that time.
but back to the main point of putting FI on a high CR motor is not safe or reliable on a regular production vehicle. now if you wanted to spend the money that goes into pro dragsters that run nitromethane and whatnot, thats a whole other story.

but for gasoline engines with a FI application, running anything over 7 psi on more than 10:1 (roughly) CR motor is asking for trouble.

however, diesel engines (semi's and large machinery) will run anywhere from 14-30:1 CR with FI with no problem, but thats also due in part to the setup of the motor itself, larger/stronger rotating assy with more cyl rings and the fact that the fuel is ignited thru self ignition due to the high CR and cyl temps. commonly referred to as "dieseling"

crazz28 · 05-22-2008, 06:33 PM

Quote:

Originally Posted by aldaron327

CR=Compression Ratio. A Compression Ratio of 11.7:1 means that the volume in the cylinder at the time when the piston goes from the bottom of it's cycle to the top gets compressed 11.7 times it's normal pressure while being ignited by a spark. A higher compression ratio means that more fuel/air are being compressed in a given volume and thus the resultant "bang" is bigger and more power is generated.

At least I'm pretty sure that's a simplified version of how to explain it. If anyone knows better, please educate me.

-Tim

Dragoneye beat me to the punch... sorry for the double-tap!

Almost right, except for that line.
I know I'll sound like a nerd here, but Dragoneye is correct, it's the volume change that Compression Ratio refers to which DOES NOT equal an equivalent pressure change, temperature changes need to be taken into account as well.

Sorry about this, but thermodynamics says:
(p1)(v1)/(T1)=(p2)(v2)/(T2)
p=pressure, v=volume, t=temp, 1 is the state at bottom of piston stroke, 2 is state at top of piston stroke

therefor:
p2=p1*(v1/v2)*(t2/t1)
At an 11.3:1 compression ratio, that means p2=11.3*p1*(t2/t1)
and since t2 will be greater than t1(in compression), the final pressure multiplier will be more than just the compression ratio. I'm not too sure what kinds of temperature the air/fuel mixture would reach in the short time it's being compressed, but it will have some influence on the final pressure.

Again, sorry for doing this, but I just saw something that I figured should be explained, if for no other reason than so I can sleep better tonight

Have a good one.

05-17-2008, 04:10 PM	#17
Mr. Wyndham I used to be Dragoneye... Drives: 2018 ZL1 1LE Join Date: Jan 2007 Location: Buffalo, NY Posts: 31,876 View My Garage	Thanks for all the input guys. There stands a good chance I get the V6 model over the V8. Not positive, yet - but the chance is there. So: I hope the aftermarket embraces this engine just as much as they do the V8. __________________ *"Keep the faith."* - Fbodfather

05-17-2008, 10:50 PM	#19
frankfan42 Drives: 94 Caprice Join Date: May 2008 Location: Dayton, Ohio Posts: 2	Some of your thoughts on direct injection show good analysis- compression ratio is a volume related measurement, it is the ratio of volume remaining in the cylinder between when the piston is at the top of the stroke compared to the bottom of the stroke. In simple terms: If a cylinder contains 11 cubic inches at bottom dead center (the bottom of piston travel) and compresses it to one cubic inch at top dead center ( top of piston travel) then compression ratio is 11:1 All other things being equal then an engine with higher compression will yield more power and efficiency than one with lower compression. Several factors restrict higher compression ratios- primarily "Knocking" which can destroy an engine if not controlled. Higher octane fuel does not have more BTU energy per unit volume, but a higher quantity of antiknock additives which will control this damaging phenomenon. In the 60s some street strip engines had compression ratios up to 14:1. Ratios were lowered starting with the 71's as most of the early emission systems could not cope with the higher levels of oxides of nitrogen which tend to form when combustion temperatures are higher, as with a higher compression ratio. Modern combustion controls and catalysts have allowed compression ratios to be increased again. Direct injection helps to control "knock" by being a finer mist which cools the intake charge significantly. Hope this helps- sorry about being so wordy.