Is my exhaust system too restrictive for my 6.0L? :TECH ONLY:
11-07-2008, 05:34 PM
#81
You're not hijacking, I am curious as well. I am not so sure though that it contributes to the problem though. It seems to me that as long as the AFR is proper and the throttle plate is opening all the way (which I confirmed mine is) and the spark advance is on, I don't see why the OS would have anything to do with peak HP.
11-07-2008, 08:46 PM
#87
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I know that guys have gotten by with the stock truck intake to about 5800-6k, but that was mostly 5.3's, and at least one 5.7 that I'm aware of. Not sure if their heads flow as well as yours though, but I'm sure that there are more agressive cams in the batch that I'm thinking of.
In fact i peak at 5800 hold a flat line til 6200 and only drop 11hp at my shift point of 6800rpms.
I'm not saying there isn't more power left in the exhaust i'm CERTAIN there is but it woudn't cause such a drastic drop off like Hirdlej is seeing on his setup.
Just something to think about for comparable combos.
Last edited by TouchOfEvil04; 11-08-2008 at 10:53 AM.
11-07-2008, 09:10 PM
#88
What do you think it is by the way? Do you think it's in the camshaft? Let's see your dyno chart. If I recall your truck laid down 350 RWHP and 350RWTQ. Am I right? I remember seeing your dyno runs on video.performancetrucks.net. I'm not trying to start a pissing match but if I have 50 more RWTQ than you, where is my HP to match? For anyone else interested, I have a TBSS intake on order along with an X-link. I'm hoping this all makes it in time before the salt hits the road. I will take a day off work, tune it and try to hit the dyno late afternoon. Once this occurs, we'll take another look at the chart. This winter I'll do a cam swap if I don't like the results I get from the intake swap.
11-07-2008, 09:44 PM
#89
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What do you think it is by the way? Do you think it's in the camshaft? Let's see your dyno chart. If I recall your truck laid down 350 RWHP and 350RWTQ. Am I right? I remember seeing your dyno runs on video.performancetrucks.net. I'm not trying to start a pissing match but if I have 50 more RWTQ than you, where is my HP to match?
Your a 5 speed i'm a auto.
That means i have roughly 10%more loss than you do which in dyno numbers would put your numbers alot lower. Figure you put out what 397 tq? I forget the exact number but goin thru my auto that would turn into 358ish to the wheels. So don't forget your numbers SHOULD be higher from the stick vs auto.
Also those numbers were on a STOCK tune from a 6.0l only things changed were 0 tq mang. shift points moved up.
Everything else stock fuel timing you name it.
I didn't have the injector to tune the truck for max hp at the time. Even with it stock the truck got up there in a/f into the 14.1 area and still held the powerband that well.
As for what i think the problem is on your truck of course the exhaust is holding you back. 2.5 is not big enough just that simple.
Your fueling could be better of course and maybe it's the bad o2 and boom you can fix it?
But the biggest is i'd say the instal of 2 degrees advanced. This almost always gives quick rpm numbers and they drop hard and fast.
Am i right....not sure but those are my guesses.
Also i didn't take your post as a pissing match man. Ask questions learn from each other i'm here just like you.
I don't know everything nobody does otherwise iw oudn't need the board lol.
I hope you get it figured out cause that motor should pull well into the 6000 range if my close to similar setup can.
11-08-2008, 09:35 AM
#90
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Your exhaust is fine. your intake should be fine, as the only thing that would cause the intake to be a restriction would be some sort of reverb. or ressonance effect in the intake at that rpm range. however, others do not seem to have that problem with the same size engine and intake. Remember, the engine is nothing more than an air pump. The intake has already proven to flow enough air for your peak power, the only thing that you wuld see on the dyno if the intake was maxed out was a flattening of the power, not a drop (all assuming that the remainder of the combo dictates higher rpm power). Same as above for the exhaust, untill you reach very high rpms, say over 7k. The ONLY thing that dictates power RANGE are the valve events. I would suspect too low of an actual LSA for the small duration of the cam, or excessive advance, either ground or installed. These things will cause very quick torque production, with poor over rev.
Also, the accepted differance w/ auto vs. manual is only max 5% (15% man. 20% auto) and it is usally closer to 2.5% unless we are talking about an old granny box and an 80e, as these are power saps.
Borrow a degree wheel and a piston stop, if you have e-fans, it should be easy and take less than an hour. Then you will KNOW what your valve timing events are.
Also, the accepted differance w/ auto vs. manual is only max 5% (15% man. 20% auto) and it is usally closer to 2.5% unless we are talking about an old granny box and an 80e, as these are power saps.
Borrow a degree wheel and a piston stop, if you have e-fans, it should be easy and take less than an hour. Then you will KNOW what your valve timing events are.