LETHAL / PRC LS7 heads / boltons / nitrous dyno numbers (Help)
06-07-2010, 04:48 PM
#21
a Mechanical did the install this is the 15+ C6 ZO6 he install cam.
I agree the owner is pissed.
True but still even with that the numbers are low this is not the 1st car we build for nitrous.
The car dynoed 525rwhp or something like that with the nitrous tune.
Thanks .
Thanks and nice setup.
Talked to the tuner and your right it did had some KR at 4800rpm..
Thanks for the help..
I can't remember the Specs of the QM500 but I remember it was really small
Under 230 duration (Int/ext) under 620 lift (int/ext) 117lsa..
Lethal cam is a lot bigger 232/250 660/660 113lsa..
I really thought the Lethal will peak at 6500-6700rpm
Thanks
I agree the owner is pissed.
True but still even with that the numbers are low this is not the 1st car we build for nitrous.
The car dynoed 525rwhp or something like that with the nitrous tune.
Thanks .
Thanks and nice setup.
Talked to the tuner and your right it did had some KR at 4800rpm..
Thanks for the help..
I can't remember the Specs of the QM500 but I remember it was really small
Under 230 duration (Int/ext) under 620 lift (int/ext) 117lsa..
Lethal cam is a lot bigger 232/250 660/660 113lsa..
I really thought the Lethal will peak at 6500-6700rpm
Thanks
06-08-2010, 07:15 PM
#23
8 Sec Tuner
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Graphs look pretty rough.. Id get the tune looked at. I feel that the LS7's like a little more fuel N/A then 13.0-13.30 area. But I use a AFM1000 wideband and it reads correct.
Here is a properly tuned LS7 with almost the same mods. But a much much smaller camshaft.
Here is a properly tuned LS7 with almost the same mods. But a much much smaller camshaft.
Last edited by Mike TexaSS; 06-08-2010 at 07:21 PM.
06-08-2010, 09:25 PM
#26
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Well , from my point of view I don't think the first dyno numbers are low , because as you know not all the dynos are the same so a loss of 20rwhp or less is normal from dyno to another and don't forget, the cam was small, I bet it was acting great on the street , don't give numbers big attention".
The problem that you are facing is the drop of power when you got new mods and that may caused by lot of things, Tune "maybe" bigger cam are hard to tune and need lot of dyno run's and street tuning , installing " the cam and the stroker" just make sure if everything is okay and there's no leaking aslo check the compression .
Here is a dyno graph for Z with lethal cam:
See with the lethal cam the number are close to your old number .
If I were you , I would change the lethal cam , believe me with those heads need much bigger cam and Texas-speed have some great cams .
The problem that you are facing is the drop of power when you got new mods and that may caused by lot of things, Tune "maybe" bigger cam are hard to tune and need lot of dyno run's and street tuning , installing " the cam and the stroker" just make sure if everything is okay and there's no leaking aslo check the compression .
Here is a dyno graph for Z with lethal cam:
See with the lethal cam the number are close to your old number .
If I were you , I would change the lethal cam , believe me with those heads need much bigger cam and Texas-speed have some great cams .
06-09-2010, 09:49 AM
#27
I personally like the 117 lsa better than the 113 lsa. For every 1 degree that the lsa is more narrow, that adds 2 degrees of overlap, and LS7 heads don't like overlap.
A ported LS7 head is probably going to be more sensitive to overlap than a stock LS7 head.
If you put the QM cam back in, you will know if it's the cam or the shortblock, and I have seen shortblocks that don't make as much power as the stock block. GM spent a lot of time on the skirt shape and ring seal.
I have a friend with an engine dyno who lost about 20 hp with an aftermarket forged piston, he didn't know what was going on, changed everything, went back to the stock piston and the power came back. Something to think about, I hope this helps.
A ported LS7 head is probably going to be more sensitive to overlap than a stock LS7 head.
If you put the QM cam back in, you will know if it's the cam or the shortblock, and I have seen shortblocks that don't make as much power as the stock block. GM spent a lot of time on the skirt shape and ring seal.
I have a friend with an engine dyno who lost about 20 hp with an aftermarket forged piston, he didn't know what was going on, changed everything, went back to the stock piston and the power came back. Something to think about, I hope this helps.
06-09-2010, 10:32 AM
#28
Well , from my point of view I don't think the first dyno numbers are low , because as you know not all the dynos are the same so a loss of 20rwhp or less is normal from dyno to another and don't forget, the cam was small, I bet it was acting great on the street , don't give numbers big attention".
The problem that you are facing is the drop of power when you got new mods and that may caused by lot of things, Tune "maybe" bigger cam are hard to tune and need lot of dyno run's and street tuning , installing " the cam and the stroker" just make sure if everything is okay and there's no leaking aslo check the compression .
Here is a dyno graph for Z with lethal cam:
See with the lethal cam the number are close to your old number .
If I were you , I would change the lethal cam , believe me with those heads need much bigger cam and Texas-speed have some great cams .
The problem that you are facing is the drop of power when you got new mods and that may caused by lot of things, Tune "maybe" bigger cam are hard to tune and need lot of dyno run's and street tuning , installing " the cam and the stroker" just make sure if everything is okay and there's no leaking aslo check the compression .
Here is a dyno graph for Z with lethal cam:
See with the lethal cam the number are close to your old number .
If I were you , I would change the lethal cam , believe me with those heads need much bigger cam and Texas-speed have some great cams .
06-10-2010, 11:22 PM
#29
I personally like the 117 lsa better than the 113 lsa. For every 1 degree that the lsa is more narrow, that adds 2 degrees of overlap, and LS7 heads don't like overlap.
A ported LS7 head is probably going to be more sensitive to overlap than a stock LS7 head.
If you put the QM cam back in, you will know if it's the cam or the shortblock, and I have seen shortblocks that don't make as much power as the stock block. GM spent a lot of time on the skirt shape and ring seal.
I have a friend with an engine dyno who lost about 20 hp with an aftermarket forged piston, he didn't know what was going on, changed everything, went back to the stock piston and the power came back. Something to think about, I hope this helps.
A ported LS7 head is probably going to be more sensitive to overlap than a stock LS7 head.
If you put the QM cam back in, you will know if it's the cam or the shortblock, and I have seen shortblocks that don't make as much power as the stock block. GM spent a lot of time on the skirt shape and ring seal.
I have a friend with an engine dyno who lost about 20 hp with an aftermarket forged piston, he didn't know what was going on, changed everything, went back to the stock piston and the power came back. Something to think about, I hope this helps.
Thanks Brian.
06-11-2010, 12:31 AM
#38
2618 forging pistons (wiseco, diamond etc.) run more skirt clearance vs a factory cast LS7 piston. I'm sure the rings are gapped for heavy nitrous?
Also figure the weight of whats used, you had Titanium rods that was 480 grams and replaced them with 650 gram forged H beam rods?
LS7 pistons are designed to be lightweight, due to a pre production incident. Forged shelf pistons generally are on the heavier side, more machining, more money goes into them, leaving metal on the shelf pistons should increase strength and keep piston price reasonable.
The extra weight, more PTW clearance, larger ring gaps will take up some power, but will result in a more reliable combination with a power adder.
Also figure the weight of whats used, you had Titanium rods that was 480 grams and replaced them with 650 gram forged H beam rods?
LS7 pistons are designed to be lightweight, due to a pre production incident. Forged shelf pistons generally are on the heavier side, more machining, more money goes into them, leaving metal on the shelf pistons should increase strength and keep piston price reasonable.
The extra weight, more PTW clearance, larger ring gaps will take up some power, but will result in a more reliable combination with a power adder.
10-09-2010, 11:02 AM
#40
2618 forging pistons (wiseco, diamond etc.) run more skirt clearance vs a factory cast LS7 piston. I'm sure the rings are gapped for heavy nitrous?
Also figure the weight of whats used, you had Titanium rods that was 480 grams and replaced them with 650 gram forged H beam rods?
LS7 pistons are designed to be lightweight, due to a pre production incident. Forged shelf pistons generally are on the heavier side
Also figure the weight of whats used, you had Titanium rods that was 480 grams and replaced them with 650 gram forged H beam rods?
LS7 pistons are designed to be lightweight, due to a pre production incident. Forged shelf pistons generally are on the heavier side
I have been noticing this for years looking at reported dyno numbers. I think we underestimate the importance of lightwt rotating assemblies. Most of our rods are overkill in wt and strength. The titanium are super light but the stock powdered rods are also lighter than most the rods we use. Gm did not use such an expensive part just for bragging rights. I also think the factory(in general) does a better job with cylinder wall finish(rings seat better) than a lot of shops do. Stock blocks are always well broken in versus a fresh engine having more friction.