How ICL effects power on cams
Teching In
Joined: Oct 2005
Posts: 2
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From: West Grove, PA
Noob Alright, i have a WRX, but any day now it is going to be an 04 GTO. And with that GTO i am going to put APS twin turbos on it. For now i am going to leave the internals stock because I do not know enough about them yet. Someone told me to not put on a cam unless it is specifacally designed for a turbo. So what would be a turbo cam, and what about the intake manifold, and when i get the new internals, should be the same as stock but forged. And can someone please explain what numbers are which with the type of cam. Thank you so much
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Joined: Aug 2003
Posts: 960
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From: Central, FL
Originally Posted by DAPSUPRSLO
What you are doing by moving the icl to the straight up position is opening and closing everything later. This is good in the sense that the intake valve will be open a little longer; however, bad in the sense that the exhaust valve will open later. In my opinion this makes your exhaust system become even more important in the performance of this cam. Remember, when I dynoed this cam on a 106 icl on the xe lobes I had approximately 36" long collector extensions (open headers), and my cam open the exhaust valve 4 degrees sooner. Morel of the story is do not run this cam with a restrictive exhaust. Good luck and like I said feel free to call, there are many variable that will result in better or worse performance out of this or any other cam.
you think that is enough exhaust???
Originally Posted by Ben R
PTV is always an issue when you start moving the cam around in the engine, and it's just another reason why it's sometimes better to leave the enigne specing and building to somebody with expernience. Might cost you a little extra but it will be worth it when you don't run into all of these little problems.
Originally Posted by DAPSUPRSLO
Generally a earlier opening of the exhaust valve .... also reduces power in the mid range cause it allows the energy created by the power stroke to escape earlier during the downward motion of the piston.
No it wont. Not in the midrange anyway. Will hurt on the very low end. (1500-3300 maybe) On a lower compression motor it may be more pronounced, but on these it generally not going to mess with it much unless you go overboard.
Granny,
I was going to get into that earlier but ughhhh...... time, there aint enough.
The exahust valve opening event happens as the piston is going down the bore. So before bottom dead center (BBDC) The later that happens the more midrange TQ on a street motor you can develop.
The issue of hurting the very low end TQ comes in to play on the exhaust valve closing event, (not opening) if you have the same duration and open the exhaust valve later (hence a lower ECL) you will also have more overlap, which is what is going to kill the low end power you are talking about.
Your on the right track.... just need to look at the events seperately. It's hard to do that when you talk about things in durations and centerlines. Think in terms of valve events, it takes a lot of time to do this and you will be golden.
You should have jumped on his nuts about this statement:
The last sentence is the only part of that I agree with. The EVO makes you work harder when you tune your cam to your headers. Because most times you setup the cam to the rest of the parts. Only when you desing a motor from the ground up do you get to work it all as a system.
My version of what he said (which BTW I know/think is right):
How about them apples?
Bret
I was going to get into that earlier but ughhhh...... time, there aint enough.
The exahust valve opening event happens as the piston is going down the bore. So before bottom dead center (BBDC) The later that happens the more midrange TQ on a street motor you can develop.
The issue of hurting the very low end TQ comes in to play on the exhaust valve closing event, (not opening) if you have the same duration and open the exhaust valve later (hence a lower ECL) you will also have more overlap, which is what is going to kill the low end power you are talking about.
Your on the right track.... just need to look at the events seperately. It's hard to do that when you talk about things in durations and centerlines. Think in terms of valve events, it takes a lot of time to do this and you will be golden.
You should have jumped on his nuts about this statement:
Originally Posted by dasupraslo
What you are doing by moving the icl to the straight up position is opening and closing everything later. This is good in the sense that the intake valve will be open a little longer; however, bad in the sense that the exhaust valve will open later. In my opinion this makes your exhaust system become even more important in the performance of this cam.
My version of what he said (which BTW I know/think is right):
Originally Posted by daSSisFASTlol
What you are doing by moving the ICL to the straight up position is opening and closing everything later. This is good for HP in the sense that the intake valve will be close a later helping the higher RPM power; and good in the sense that the exhaust valve will open later helping midrange TQ. In my opinion this makes your exhaust system specs even more important in the design of the cam.
Bret
Originally Posted by GrannySShifting
No it wont. Not in the midrange anyway. Will hurt on the very low end. (1500-3300 maybe) On a lower compression motor it may be more pronounced, but on these it generally not going to mess with it much unless you go overboard.
Well according to very knowledgeable sources a certain nascar team picked up quite a bit of MIDRANGE by increasing the flow capabilities of their exhaust port and reducing exhaust timing (opening the exhaust valve later). I see what you are saying about as the compression increases the lower part of the blow down period is not as important but what do you consider high compression and low compression. 12 to 1 is kind of middle of the road, all combonations being considered in the world of street to race engines.
Oh, and Bret, those apple look delicious, ha ha. Thanks for the explanation I think it can be considered both ways though. Would you not agree that at some point we are opening the exhaust valve to late and causing pumping losses. I think in general the later you open the exhaust valve the better your exhaust system (from the exhaust valve of the head all the way to the end of your tail pipe) better flow and be in tune with your rpm range.
I think it can be considered both ways though. Would you not agree that at some point we are opening the exhaust valve to late and causing pumping losses. I think in general the later you open the exhaust valve the better your exhaust system (from the exhaust valve of the head all the way to the end of your tail pipe) better flow and be in tune with your rpm range.
Originally Posted by seadoo
the headers will be 1.75" 32" long with HVMC, and 3" X-pipe over axle (79 Camaro)
you think that is enough exhaust???
you think that is enough exhaust???
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Originally Posted by SStrokerAce
Granny,
I was going to get into that earlier but ughhhh...... time, there aint enough.
You should have jumped on his nuts about this statement:
I was going to get into that earlier but ughhhh...... time, there aint enough.
You should have jumped on his nuts about this statement:
Originally Posted by DAPSUPRSLO
What you are doing by moving the icl to the straight up position is opening and closing everything later. This is good in the sense that the intake valve will be open a little longer; however, bad in the sense that the exhaust valve will open later. In my opinion this makes your exhaust system become even more important in the performance of this cam. Remember, when I dynoed this cam on a 106 icl on the xe lobes I had approximately 36" long collector extensions (open headers), and my cam open the exhaust valve 4 degrees sooner. Morel of the story is do not run this cam with a restrictive exhaust. Good luck and like I said feel free to call, there are many variable that will result in better or worse performance out of this or any other cam.
A month ago he was recommending a 236/236 cam on a 108 LSA to a guy with cats and Y pipe type exhaust, some peoples children
Nick you done putting your tank together yet? Stop posting on the interweb and get to work.
As per dynotesting weve done, opening the exhaust valve 8 degrees later all other the valve events same, on a 11-12:0 compression LS1 does what I was saying.
Jeff, I don't think that was the cam I was recommending to him at all. I've given you a hard time about misconstruing facts before and this is another time fooo, but then again I've got my stuff wrong to. I will admit I have learned quite a bit since then though and would not have made the recommendation I made back then today given Kevin's exhaust system.
As for my tank see my comment on EFA, you'd be better to ask Erik over at HPE Looks like we will be, actually he will be doing some custom lifters form my junk that are a one off design he came up with. They are going in someone elses motor first however. After that it's just getting it back from them and putting it in the car and hopefully rolln' out.
Now stop typing on here yourself and bust into the 11s :-p
As for my tank see my comment on EFA, you'd be better to ask Erik over at HPE
Looks like we will be, actually he will be doing some custom lifters form my junk that are a one off design he came up with. They are going in someone elses motor first however. After that it's just getting it back from them and putting it in the car and hopefully rolln' out. Now stop typing on here yourself and bust into the 11s :-p
Originally Posted by DASUPRASLO
Well according to very knowledgeable sources a certain nascar team picked up quite a bit of MIDRANGE by increasing the flow capabilities of their exhaust port and reducing exhaust timing (opening the exhaust valve later).
Originally Posted by DAPSUPRSLO
Oh, and Bret, those apple look delicious, ha ha. Thanks for the explanation I think it can be considered both ways though. Would you not agree that at some point we are opening the exhaust valve to late and causing pumping losses. I think in general the later you open the exhaust valve the better your exhaust system (from the exhaust valve of the head all the way to the end of your tail pipe) better flow and be in tune with your rpm range.
I think it can be considered both ways though. Would you not agree that at some point we are opening the exhaust valve to late and causing pumping losses. I think in general the later you open the exhaust valve the better your exhaust system (from the exhaust valve of the head all the way to the end of your tail pipe) better flow and be in tune with your rpm range.Opening the exhaust valve earlier helps in higher RPMs and situations when there is a ton of cylinder pressure... N2O comes to mind.
Bret
Originally Posted by SStrokerAce
Sounds about right to me... this is why you work on exhaust ports to make them better.
Opening the exhaust valve earlier helps in higher RPMs and situations when there is a ton of cylinder pressure... N2O comes to mind.
Opening the exhaust valve earlier helps in higher RPMs and situations when there is a ton of cylinder pressure... N2O comes to mind.
The cam I just had ground for Waynes car picked up 30 across the board on the 225 hit. This is over the cam he had that went 10.0 with on a 150 shot/heads/cam 3600 lb. Tryed some different stuff with the lobes etc that seems to work
but Comp grew them slightly funny. The exhaust valve actually opens 2 degrees LATER then before, so next round Im going to try and lose 20 down low for as much as we can get up top. 
