408 Dyno = Low Numbers
May 11, 2008 | 11:38 PM
#31
See, in your last paragraph lies the correct term. Efficientcy. Does not mean the motor should be efficient off boost, but only under the case it is being truley used for.
I do not disagree that his motor does sound alittle fishy with the numbers, but I would just not go around being mad about it. Thats the point I am making.
Marks truck on 12psi right now is a 438 making about 750hp. I guess it would be making only about 375-400 all motor then? So that would be about .9hp per CID then. And on boost its making about 1.7 HP per CID now. So I am not sure if I would follow that too well since too many factors go into a turbo motors design. Like TQ and HP could be totally different in every setup. As you come into the Turbos efficientcy window, it only gets better, not worse.
R
I do not disagree that his motor does sound alittle fishy with the numbers, but I would just not go around being mad about it. Thats the point I am making.
Marks truck on 12psi right now is a 438 making about 750hp. I guess it would be making only about 375-400 all motor then? So that would be about .9hp per CID then. And on boost its making about 1.7 HP per CID now. So I am not sure if I would follow that too well since too many factors go into a turbo motors design. Like TQ and HP could be totally different in every setup. As you come into the Turbos efficientcy window, it only gets better, not worse.
R
the theory of what a motor makes at 1 bar NA and then add boost at 2 bar works pretty well but yes there are exceptions where this theory doesnt work as well.
marks 438 should see nothing less then 1100 BHP
May 11, 2008 | 11:47 PM
#32
yes there are lots of things that play role in numbers. mark's truck is also AWD? or just 4wd? it also has quadsteer which im sure that rear eats more drivetrain loss then a typical 2wd truck would.
the theory of what a motor makes at 1 bar NA and then add boost at 2 bar works pretty well but yes there are exceptions where this theory doesnt work as well.
marks 438 should see nothing less then 1100 BHP
the theory of what a motor makes at 1 bar NA and then add boost at 2 bar works pretty well but yes there are exceptions where this theory doesnt work as well.
marks 438 should see nothing less then 1100 BHP
Yup, its almost there now as it sits. Its AWD, plus a Dana 60 out back. Custom 4" Steel driveshaft, everything. IF it makes about 750ish now, take into account all the lose and thats about 900+ Right now. And thats only 12psi.
R
May 19, 2008 | 11:32 AM
#33
Update:
I was just informed by the engine builder that the cr is actually 8.2 not 8.7 so I am thinking of changing to AFR 225 heads from the 6.0 truck heads to increase the cr to 9.2 instead. They flow better any ways and have a thicker deck so they can handle higher boost better.
How much cr can I get away with using 91 oct pump gas and still run 15 PSI? I can always run race (110 oct) gas and turn up the boost for the track.
I was just informed by the engine builder that the cr is actually 8.2 not 8.7 so I am thinking of changing to AFR 225 heads from the 6.0 truck heads to increase the cr to 9.2 instead. They flow better any ways and have a thicker deck so they can handle higher boost better.
How much cr can I get away with using 91 oct pump gas and still run 15 PSI? I can always run race (110 oct) gas and turn up the boost for the track.
May 19, 2008 | 11:54 AM
#34
Are you running methanol as well? I'm running a 9.4:1 motor with meth and 15psi is no problem on pump gas.
If you don't already have a meth kit I would get one for sure. It will allow you to run your higher octane only under boosted conditions, which will let you get away with a little higher CR for better off-boost driveability.
If you don't already have a meth kit I would get one for sure. It will allow you to run your higher octane only under boosted conditions, which will let you get away with a little higher CR for better off-boost driveability.
May 20, 2008 | 04:20 PM
#35
I recently had the 408 installed in my Silverado and this weekend I had it tuned and dynoed. I was disappointed to see that it only made 250 HP and 280 TQ.
The specs are as follows:
408 ci w/8.7 cr
P&P 6.0(317) heads
224/231 .595 .595 114 cam
Stock exhaust manifold
Stock intake
Stock exhaust(cats, pipes, muffler)
2800 stall converter
The specs are as follows:
408 ci w/8.7 cr
P&P 6.0(317) heads
224/231 .595 .595 114 cam
Stock exhaust manifold
Stock intake
Stock exhaust(cats, pipes, muffler)
2800 stall converter
How do your heads flow?
Your stock exhaust and intake are really hurting that big motor. It really wants to breathe. Shorty headers and a LS6 intake should work with the STS kit and will help you make more power with less boost.
Maybe consider changing to L92 heads and L76 intake?
My 05 5.3L truck made 255rwhp and 274rwtq with a K&N filter, muffler, and 87 octane Wheatley tune on sunday.
May 20, 2008 | 08:09 PM
#37
Can you post your dyno graph?
How do your heads flow?
Your stock exhaust and intake are really hurting that big motor. It really wants to breathe. Shorty headers and a LS6 intake should work with the STS kit and will help you make more power with less boost.
Maybe consider changing to L92 heads and L76 intake?
My 05 5.3L truck made 255rwhp and 274rwtq with a K&N filter, muffler, and 87 octane Wheatley tune on sunday.
How do your heads flow?
Your stock exhaust and intake are really hurting that big motor. It really wants to breathe. Shorty headers and a LS6 intake should work with the STS kit and will help you make more power with less boost.
Maybe consider changing to L92 heads and L76 intake?
My 05 5.3L truck made 255rwhp and 274rwtq with a K&N filter, muffler, and 87 octane Wheatley tune on sunday.
Hopefully I can pick up a bit by going to the AFR heads and higher cr.
I am in southern Cali in Riverside county.
May 21, 2008 | 04:25 PM
#38
I can install headers, exhaust and a Fast intake but under boost it would not make a difference so I opted not to go that route. If I can make 600rwhp on 18PSI with the stock intake or the same hp with only 15PSI using the Fast it is all the same.
Hopefully I can pick up a bit by going to the AFR heads and higher cr.
Hopefully I can pick up a bit by going to the AFR heads and higher cr.
Why spend another couple thousand bucks on heads when you already have decent heads that are being choked up? But then you won't spend maybe half that on the stuff to unchoke them? You want the entire system to flow well, not just the heads! WHy did you even buy ported heads in the first place? Your intake and exhaust are killing your numbers!
If you can make 600rwhp on 18psi with the stock intake or @15psi with al LS2/6 intake, then think about how much you'll be able to make at 18psi with a good intake!
I'd still like to see your dyno numbers through the RPM range.
May 21, 2008 | 04:42 PM
#39
Peak torque occurred at 3900rpm and was right at 290ft-lbs. Torque was above 250ft-lbs from 2700rpm to 5200rpm. Above 275ft-lbs from 3700rpm to 4700rpm. Torque had fallen to 225ft-lbs at 5600rpm.
Peak hp occurred right around 5000rpm.
Peak hp occurred right around 5000rpm.
May 21, 2008 | 05:43 PM
#40
Have you had them indepedantantly flowed? According to their site they flow over 300 on the intake and 230 on the exhaust. But what size valves are they talking about?
I just don't understand your thought process.
Why spend another couple thousand bucks on heads when you already have decent heads that are being choked up? But then you won't spend maybe half that on the stuff to unchoke them? You want the entire system to flow well, not just the heads! WHy did you even buy ported heads in the first place? Your intake and exhaust are killing your numbers!
If you can make 600rwhp on 18psi with the stock intake or @15psi with al LS2/6 intake, then think about how much you'll be able to make at 18psi with a good intake!
I'd still like to see your dyno numbers through the RPM range.
I just don't understand your thought process.
Why spend another couple thousand bucks on heads when you already have decent heads that are being choked up? But then you won't spend maybe half that on the stuff to unchoke them? You want the entire system to flow well, not just the heads! WHy did you even buy ported heads in the first place? Your intake and exhaust are killing your numbers!
If you can make 600rwhp on 18psi with the stock intake or @15psi with al LS2/6 intake, then think about how much you'll be able to make at 18psi with a good intake!
I'd still like to see your dyno numbers through the RPM range.
As far as the intake/exhaust goes. If my engine can take 800 crank hp total then it does not matter if I get that with 18PSI and a stock intake or with 15 PSI and an LS2/6, Fast, Vic Jr. etc. I actually have an intake from a SSR in the trunk of my Honda but after reading some posts on LS1tech I decided against it. Here is the thread: https://ls1tech.com/forums/showthread.php?t=815286
I will open up the exhaust but not until I install the turbo since I don't know exactly how I am going to install it yet. I have a STS but am thinking of installing it further up like the Trick mid/low mount. Once I do that then I will get a new exhaust put in from the turbo all the way to the tips.
As far as headers STS does not recommend them as they feel the turbo is the biggest restriction and the stock logs seem to do well keeping the heat in. Even though I will be moving the turbo further forward than the standard STS kit I don't know if headers would actually help me under boost. I will read up on it some more. Maybe others that have ventured this way can help me along.