Why does it take so long to rev down!?!?
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From: detroit
Dude most of your high hp engines are 12 to 13:1 compression. That has a huge effect on a de-rev.
Wow, do you know anything about how an engine works? Thats all I can really say to you.
ls1 is 10.5:1 But that is still not enough to make the de rev more aggressive. When I had the stock engine in my camaro I would rev it and it is a slow de-rev. My race engine that I built is 11.8:1 compression and has a decent cam derevs pretty good.
All I am saying is that it is basic engine design. That is why such the long de-rev. Simple mechanics and math.
BTW 9.5:1 is when the car is makine hp. I would bet at an idle it is in the 7.5 to 8 range.
All compressed engines are low compression.
ls1 is 10.5:1 But that is still not enough to make the de rev more aggressive. When I had the stock engine in my camaro I would rev it and it is a slow de-rev. My race engine that I built is 11.8:1 compression and has a decent cam derevs pretty good.
All I am saying is that it is basic engine design. That is why such the long de-rev. Simple mechanics and math.
BTW 9.5:1 is when the car is makine hp. I would bet at an idle it is in the 7.5 to 8 range.
All compressed engines are low compression.
Last edited by sscrazy; Jul 4, 2007 at 07:29 PM. Reason: Automerged Doublepost
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From: detroit
compression and lsa does have effect on de-rev.... his statement about muscle cars is true also.. my first reaction to this post was compression and what not... however i know we run 9.5:1 so its more of a tb/electric issue for us....
no need to flame the guy b/c he is old school thinking... doesnt make him less knowledgeable.. just in a different field.. hell im still learning this new tech stuff
no need to flame the guy b/c he is old school thinking... doesnt make him less knowledgeable.. just in a different field.. hell im still learning this new tech stuff
The guy that sais that it is only because of the electronics is partly right. But it has to do with both. But I would say more the "old school" lol.
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From: Houston, Tx
Dude most of your high hp engines are 12 to 13:1 compression. That has a huge effect on a de-rev.
Wow, do you know anything about how an engine works? Thats all I can really say to you.
ls1 is 10.5:1 But that is still not enough to make the de rev more aggressive. When I had the stock engine in my camaro I would rev it and it is a slow de-rev. My race engine that I built is 11.8:1 compression and has a decent cam derevs pretty good.
All I am saying is that it is basic engine design. That is why such the long de-rev. Simple mechanics and math.
BTW 9.5:1 is when the car is makine hp. I would bet at an idle it is in the 7.5 to 8 range.
All compressed engines are low compression.
Wow, do you know anything about how an engine works? Thats all I can really say to you.
ls1 is 10.5:1 But that is still not enough to make the de rev more aggressive. When I had the stock engine in my camaro I would rev it and it is a slow de-rev. My race engine that I built is 11.8:1 compression and has a decent cam derevs pretty good.
All I am saying is that it is basic engine design. That is why such the long de-rev. Simple mechanics and math.
BTW 9.5:1 is when the car is makine hp. I would bet at an idle it is in the 7.5 to 8 range.
All compressed engines are low compression.
You really shouldn't make comments to people about not knowing something if you have NO clue. NJHK probably knows a million times more about engines than you do.
The LSJ has a 9.5:1 static compression ratio. Yes there are supercharged cars with higher compression ratios, even some over 10.5:1, it all depends on the setup and fuel being run.
Edit: Like I said, I know a higher compression engine will decel faster than a lower one, but that's not the point of this thread. No one is trying to compare our 9.5:1 engine against a 12:1 engine. They were trying to compare our 9.5:1 engine against an older 9.5:1 engine that does NOT hold the throttle plate open on decel.
If you have driven this car then you should know what we are talking about. Rev the engine up, and watch how slowly it takes it to settle down; then go get into another car with similar compression ratio and a regular spring loaded throttle plate and you will see the difference.
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From: Vancouver B.C.
It takes a fair amount of horsepower to turn the blower as it is, conversly it would take energy to force it to stop more quickly. It's not practical or efficient to do so.
You can't have it both ways..........unless you have a turbocharger, but that's another issue.
A good metaphor for this scenario would be the way we drive: we could floor-it from every stoplight (inducing huge energy into the car), and then slam on the brakes at the next.....screeching to the line- but it's hard on the internals (you being one of them).
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From: Houston, Tx
It's PHYSICS 101. Between the INERTIA of the blower and the flywheel, the engine management system has to be tuned in such a way that RPM's drop smoothly amongst the mechanicaly fused components. In other words, there's a boat anchor worth of crap hanging off this engine (for it's size) and once it's spinning fast, you can't simply "turn the switch off" without stressing the internals.
It takes a fair amount of horsepower to turn the blower as it is, conversly it would take energy to force it to stop more quickly. It's not practical or efficient to do so.
You can't have it both ways..........unless you have a turbocharger, but that's another issue.
It takes a fair amount of horsepower to turn the blower as it is, conversly it would take energy to force it to stop more quickly. It's not practical or efficient to do so.
You can't have it both ways..........unless you have a turbocharger, but that's another issue.
As I said in a few posts above, Mercedes does this on their cars and their diesels for emission purposes, and on the diesel so you do not hit your head on the dash
.NJHK doesn't know anything about engines
Last edited by Mikey851; Jul 4, 2007 at 08:24 PM. Reason: Automerged Doublepost
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From: Vancouver B.C.
Imagine tuning for a 2.0L engine that you just stuck a roots blower on from scratch lol. It would definately be a challenge, and you're right that they do have to use little tricks to make it emission friendly and maintain good driveability.
As I said in a few posts above, Mercedes does this on their cars and their diesels for emission purposes, and on the diesel so you do not hit your head on the dash.
NJHK doesn't know anything about engines
As I said in a few posts above, Mercedes does this on their cars and their diesels for emission purposes, and on the diesel so you do not hit your head on the dash
.NJHK doesn't know anything about engines
Germans......there's always one eh?
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Joined: 01-05-06
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From: East Brunswick, NJ
Wow man, that's all I can say.
You really shouldn't make comments to people about not knowing something if you have NO clue. NJHK probably knows a million times more about engines than you do.
mpression ratio and a regular spring loaded throttle plate and you will see the difference.
You really shouldn't make comments to people about not knowing something if you have NO clue. NJHK probably knows a million times more about engines than you do.
mpression ratio and a regular spring loaded throttle plate and you will see the difference.
I'm not even going to comment to sscrazy because it's not worth my time.
Last edited by NJHK; Jul 4, 2007 at 08:34 PM. Reason: Automerged Doublepost
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Joined: 11-05-06
Posts: 259
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From: Vancouver B.C.
Dude most of your high hp engines are 12 to 13:1 compression. That has a huge effect on a de-rev.
Wow, do you know anything about how an engine works? Thats all I can really say to you.
ls1 is 10.5:1 But that is still not enough to make the de rev more aggressive. When I had the stock engine in my camaro I would rev it and it is a slow de-rev. My race engine that I built is 11.8:1 compression and has a decent cam derevs pretty good.
All I am saying is that it is basic engine design. That is why such the long de-rev. Simple mechanics and math.
BTW 9.5:1 is when the car is makine hp. I would bet at an idle it is in the 7.5 to 8 range.
All compressed engines are low compression.
Wow, do you know anything about how an engine works? Thats all I can really say to you.
ls1 is 10.5:1 But that is still not enough to make the de rev more aggressive. When I had the stock engine in my camaro I would rev it and it is a slow de-rev. My race engine that I built is 11.8:1 compression and has a decent cam derevs pretty good.
All I am saying is that it is basic engine design. That is why such the long de-rev. Simple mechanics and math.
BTW 9.5:1 is when the car is makine hp. I would bet at an idle it is in the 7.5 to 8 range.
All compressed engines are low compression.
Compression changes with RPM'S! No wonder my truck has two tanks ! Ones for REGULAR and ones for PREMIUM! HOLY SHIIIT! I guess it just eats what it needs and when it wants to? I've been abusing my baby all this time!
BRILLIANT!:
Last edited by JMH; Jul 4, 2007 at 08:47 PM. Reason: Automerged Doublepost
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From: detroit
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From: East Brunswick, NJ
I didn't even notice that!
I love it how the guy who says that compression ratio changes in different engine operations says I don't know anything about how a engine works
ROFLTACO!
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From: Houston, Tx
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From: East Brunswick, NJ
Thank You...
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From: Vancouver B.C.
As a result, mean state compression ratio must fall in order to compensate unless you have accsess to grades of fuel that are not commonly available at the pump. Hence "Blown Engines" have a lower C- ratio and yet require Premium Fuel. My issue was concerning static ratios relative to RPM. This doesn't change .....because it can't. The C-ratio is calibrated relative to the intended use of the vehicle and doesn't jump from lows to highs..........IT IS a constant.
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Joined: 01-05-06
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From: East Brunswick, NJ
Yes...... adding additional pressure to the cylinder bumps pressure. As a result, mean state compression ratio must fall in order to compensate unless you have accsess to grades of fuel that are not commonly available at the pump. Hence "Blown Engines" have a lower C- ratio and yet require Premium Fuel.
My issue was concerning static ratios relative to RPM. This doesn't change .....because it can't. The C-ratio is calibrated relative to the intended use of the vehicle and doesn't jump from lows to highs..........IT IS a constant.
As a result, mean state compression ratio must fall in order to compensate unless you have accsess to grades of fuel that are not commonly available at the pump. Hence "Blown Engines" have a lower C- ratio and yet require Premium Fuel. My issue was concerning static ratios relative to RPM. This doesn't change .....because it can't. The C-ratio is calibrated relative to the intended use of the vehicle and doesn't jump from lows to highs..........IT IS a constant.
lol
