Why is my powerband dropping off early?
Thread Starter
Launching!
Joined: May 2004
Posts: 231
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From: Philly
Why is my powerband dropping off early? In my car, I have the TR230/224 reverse split cam with these specs:
230/224 .575/.563 111 LSA
I also have hooker LT and ORY, dynomouth exhaust, ASP underdrive pulley, mezziere elec. water pump, ported/polished TB and harland sharp 1.8 rockers, comp cams 918 springs (blue strip), Ti retainers, TR hardened pushrods. Using stock heads and 3.42 gears.
Why does my dyno look like this:
Dyno with tuning
My power is dropping off around 5K RPM, when it should be pulling up and beyond that point. I also think those numbers are pretty low for this cam, since most guys are putting close to 400 RWHP. Close being within 10 HP of 400. Any ideas of what could be causing this problem? Is it the tune I have? Is there something else I should look at?
The dyno is right, because my car stops pulling after 5K...I need some help.
230/224 .575/.563 111 LSA
I also have hooker LT and ORY, dynomouth exhaust, ASP underdrive pulley, mezziere elec. water pump, ported/polished TB and harland sharp 1.8 rockers, comp cams 918 springs (blue strip), Ti retainers, TR hardened pushrods. Using stock heads and 3.42 gears.
Why does my dyno look like this:
Dyno with tuning
My power is dropping off around 5K RPM, when it should be pulling up and beyond that point. I also think those numbers are pretty low for this cam, since most guys are putting close to 400 RWHP. Close being within 10 HP of 400. Any ideas of what could be causing this problem? Is it the tune I have? Is there something else I should look at?
The dyno is right, because my car stops pulling after 5K...I need some help.
Looks like you are getting some valve float above 5500 rpms. I would almost bet that it's because of the 1.8 rockers, hence the reason we do not recommend use of 1.8s with our cams. The lobes are very aggressive and do not need a more aggressive rocker. The combination of the 2 will be more then the springs can handle, unless you are running some serious spring pressure. I would slap your stock rockers back on and redyno and I bet your problem would go away.
Hope this helps...
Hope this helps...
What you are seeing drop is your torque curve. By the theory of horsepower calculation the torque of the motor is supposed to drop at 5252 rpms anyways unless you are just making crazy crazy hp at a high rpm. Basically this is the simple way it works. (X * RPM) = 5252 * HP
Basically if you make 375 ft/lbs at 5000 rpm this is how it would work
(375 * 5000) = 5252 * HP
1875000 = 5252 * HP
Now to get rid of the 5252 on the HP side you have to divide both sides of the equasion by 5252 like this
1875000.............5252 * HP
_______ = _________ It ends up like this 357 = 1 * HP
5252................5252
Well, if you remember from High school a variable like HP is always considered (1*whatever the variable is) so 1 * 1 is always 1 so that means that 357 = HP so if your torque is 375 ft lbs at 5000 rpms your HP should be about 357. Here is a good link to give you an even better idea of what I'm talking about http://www.car-videos.com/articles/h...wer_torque.asp
Basically if you make 375 ft/lbs at 5000 rpm this is how it would work
(375 * 5000) = 5252 * HP
1875000 = 5252 * HP
Now to get rid of the 5252 on the HP side you have to divide both sides of the equasion by 5252 like this
1875000.............5252 * HP
_______ = _________ It ends up like this 357 = 1 * HP
5252................5252
Well, if you remember from High school a variable like HP is always considered (1*whatever the variable is) so 1 * 1 is always 1 so that means that 357 = HP so if your torque is 375 ft lbs at 5000 rpms your HP should be about 357. Here is a good link to give you an even better idea of what I'm talking about http://www.car-videos.com/articles/h...wer_torque.asp
Thread Starter
Launching!
Joined: May 2004
Posts: 231
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From: Philly
Yeah, it looks like I was mixing up the TQ and HP curves...
...so the power curve is fine, but both HP/TQ are still on the low side. I would expect more than 370/357 corrected with that cam and my mods, even on ESP's dyno, which is reputed to be conservative with the numbers.
The place that did the work on my car sucks when it comes to providing correct information as to the specs of what is actually in my car.
...so the power curve is fine, but both HP/TQ are still on the low side. I would expect more than 370/357 corrected with that cam and my mods, even on ESP's dyno, which is reputed to be conservative with the numbers.
The place that did the work on my car sucks when it comes to providing correct information as to the specs of what is actually in my car.
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Those ripples on the hp curve at 5500 likely indicate what Paul said, and it's his cam so I'd do what he said. (or you have bent pushrods) I have 1.8s on my Hot Cam & my HP ramps up fast like yours does at 4500, only mine continues that fast up to about 6k, where it slows & levels off at 6300 (@391+hp). You should be getting around 400 out of your setup too.
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Originally Posted by SsZERO
So you're saying if I go back to stock 1.6 rockers, I'll pick up an extra 20-30 HP at the wheels? How would valve float feel when I am driving? Would I be able to detect it any way?
Stock rocker are 1.7s. It's hard to say what you'll pick, depending on how bad you are floating the valves it could be a little or it could be a lot. Valve float would feel just like a drop in power while driving and it could be audible.
Paul
Thread Starter
Launching!
Joined: May 2004
Posts: 231
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From: Philly
OK, I do have 1.7 rockers in there. I double checked, the Harlan rockers I have are 1.7. So I guess the rockers are not the issue. What else could be causing me to give up so much HP/TQ? Shouldn't my corrected HP be like 380-390?
Thread Starter
Launching!
Joined: May 2004
Posts: 231
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From: Philly
Originally Posted by jrp
ok, dont believe what i already told you yesterday in your dyno thread 
. and stock rockers are 1.7.
. and stock rockers are 1.7.Last edited by SsZERO; Sep 7, 2004 at 07:53 PM.
Originally Posted by MyLS1Hauls
I'd still try the stock rockers. How many miles on those 918 springs?
also...how can you not know what you have in your valvetrain? unless you didn't install it yourself...in which case thats still a lame-*** exscuse...
Originally Posted by jrp
ok, dont believe what i already told you yesterday in your dyno thread . and stock rockers are 1.7.
. and stock rockers are 1.7.
Originally Posted by SsZERO
Is there a difference between the stock 1.7 rockers and the HS 1.7 rockers, because changing them is a somewhat involved process.
Less than 1500 miles on the 918 springs.
Less than 1500 miles on the 918 springs.
Thread Starter
Launching!
Joined: May 2004
Posts: 231
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From: Philly
What difference does it make to you? You sound like someone who rides around on a short yellow bus.
also...how can you not know what you have in your valvetrain? unless you didn't install it yourself...in which case thats still a lame-*** exscuse...
blowin off jrp are we? bad idea buddy....
Originally Posted by cyphur_traq
also...how can you not know what you have in your valvetrain? unless you didn't install it yourself...in which case thats still a lame-*** exscuse...
blowin off jrp are we? bad idea buddy....
Thread Starter
Launching!
Joined: May 2004
Posts: 231
Likes: 0
From: Philly
Originally Posted by MyLS1Hauls
Shoot, rocker arms could be changed in 1hr easily.
dude, stop being a ******* dousch. you asked a question and all these people are trying to help you, stop being a dick, most of these people know 100 to 200 times more than you about cars, which is made more obvious when you say you dont even know what type of valve train the shop put in your car. if your gonna ask a question, and everyone is telling you the same thing, chances are there right.