396ci LT4, YSI and 15lb of boost dyno result :(
03-16-2010, 09:13 PM
#41
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I e-mailed Lloyd Elliott www.Elliottsportworks.com asking for advice and this is his replay:
"Big thing that sticks out to me is the cam (248/254 is TOO MUCH duration). Something in the 223/234 duration range would be MUCH better at trapping cylinder pressure (and making more power) and having less overlap. Overlap allows exhaust to go up intake port and contaminate the mixture (before TDC) and also allows boost to right out the tail pipe (after TDC).
With all that boost and the size of the SC, you do not need the intake open that long to fill the cylinders well.
I would also make sure the springs have about 165-170 lbs of seat pressure for that much boost and aggressive lobes. I would use a lobe with a slower ramp speed and make sure it remains stable under high boost.
I would rather see around 9.25 compression and if we have less than 8.0 compression, that could be killing us.
Do the math for chamber size, -37 cc pistons, head gasket thickness and piston deck ht to see what the compression really is. "
"boost is just the pressure in the intake but that doesn't tell you how much fresh air is in the cylinder during combustion or how much exhaust pulse is mixed in contaminating the mixture. It just shows pressure and that is it.
Smaller duration cams will work MUCH better for you at the compression level you are talking about and a wide LSA to cut down even more overlap will make it even better.
Have you checked the cylinder pressure on that set up? it is probably about 100-110 lbs of cranking pressure and will NEVER make any power. You want it to be in the 140-150 psi range to actually work well with that amount of boost.
Might be lots of things to cause the low #'s but a cam swap would be my first step. I prefer my Bullet/Ultradyne asymmetrical lobes and can get you 223/234 .565/.592 115 LSA billet cam for $320 for a standard base or $340 for a small base cam. These asymmetrical lobes open the valves almost like a solid roller and fill the cylinders MUCH better than similar duration lobes from other companies. They make power like a lobe that is 5-6 degrees larger than there @ .050 duration #'s. The closing ramp speed on the lobe is a lot slower and allows the valve trane to be stable at high RPM like the Comp Magnum lobes while packing more in/out of the cylinders. These lobes are the reason I chose Bullet/Ultradyne to make my cams for me.
If you chose to use Comp, get a 224/236 .560/.608 (3119/3122 lobes) on a 115 LSA plus 7 (108 ICL) and see how it does. This will need 155 lbs or more seat pressure and 350+ open pressure to remain stable at high RPM. Comp only makes lobes every 6 degrees of duration so you have to go a lil different on the specs than what I would like but it will still be TONS better than what you have.
A cam swap would be my first swap and then go from there. Other than tearing the engine down and shoving more compression in there, this is the easiest (and cheapest) thing to change."
"The cam specs will be the same up to 9.25-9.5 compression.
If we actually have 8.00 or less compression, the thing may run even better with a 211/223 .565/.565 114 LSA cam just to keep as much cylinder pressure as we can but it will run out of steam up top trying to feed all those cubes. kind of a give./take thing and I would prefer not to "band-aid up" the cam specs for the compression and then require a different cam later when you get the right compression. Once you get 9.0-9.25 compression, the cam will be perfect.
Definitely get a 1.6 rocker."
"Big thing that sticks out to me is the cam (248/254 is TOO MUCH duration). Something in the 223/234 duration range would be MUCH better at trapping cylinder pressure (and making more power) and having less overlap. Overlap allows exhaust to go up intake port and contaminate the mixture (before TDC) and also allows boost to right out the tail pipe (after TDC).
With all that boost and the size of the SC, you do not need the intake open that long to fill the cylinders well.
I would also make sure the springs have about 165-170 lbs of seat pressure for that much boost and aggressive lobes. I would use a lobe with a slower ramp speed and make sure it remains stable under high boost.
I would rather see around 9.25 compression and if we have less than 8.0 compression, that could be killing us.
Do the math for chamber size, -37 cc pistons, head gasket thickness and piston deck ht to see what the compression really is. "
"boost is just the pressure in the intake but that doesn't tell you how much fresh air is in the cylinder during combustion or how much exhaust pulse is mixed in contaminating the mixture. It just shows pressure and that is it.
Smaller duration cams will work MUCH better for you at the compression level you are talking about and a wide LSA to cut down even more overlap will make it even better.
Have you checked the cylinder pressure on that set up? it is probably about 100-110 lbs of cranking pressure and will NEVER make any power. You want it to be in the 140-150 psi range to actually work well with that amount of boost.
Might be lots of things to cause the low #'s but a cam swap would be my first step. I prefer my Bullet/Ultradyne asymmetrical lobes and can get you 223/234 .565/.592 115 LSA billet cam for $320 for a standard base or $340 for a small base cam. These asymmetrical lobes open the valves almost like a solid roller and fill the cylinders MUCH better than similar duration lobes from other companies. They make power like a lobe that is 5-6 degrees larger than there @ .050 duration #'s. The closing ramp speed on the lobe is a lot slower and allows the valve trane to be stable at high RPM like the Comp Magnum lobes while packing more in/out of the cylinders. These lobes are the reason I chose Bullet/Ultradyne to make my cams for me.
If you chose to use Comp, get a 224/236 .560/.608 (3119/3122 lobes) on a 115 LSA plus 7 (108 ICL) and see how it does. This will need 155 lbs or more seat pressure and 350+ open pressure to remain stable at high RPM. Comp only makes lobes every 6 degrees of duration so you have to go a lil different on the specs than what I would like but it will still be TONS better than what you have.
A cam swap would be my first swap and then go from there. Other than tearing the engine down and shoving more compression in there, this is the easiest (and cheapest) thing to change."
"The cam specs will be the same up to 9.25-9.5 compression.
If we actually have 8.00 or less compression, the thing may run even better with a 211/223 .565/.565 114 LSA cam just to keep as much cylinder pressure as we can but it will run out of steam up top trying to feed all those cubes. kind of a give./take thing and I would prefer not to "band-aid up" the cam specs for the compression and then require a different cam later when you get the right compression. Once you get 9.0-9.25 compression, the cam will be perfect.
Definitely get a 1.6 rocker."
Last edited by kazdevil; 03-19-2010 at 05:44 AM.
03-16-2010, 09:18 PM
#42
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03-17-2010, 05:28 AM
#43
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Cam swap is defo an option.
Although I dont really see that guys logic about exhaust contaminating intake charge when there is a blower constantly pumping air in the correct direction through the engine.
Out the exhaust, yes...but back into the intake, perhaps less likely.
Easiest and cheapest thing to try. Spin that damn blower harder !
Although I dont really see that guys logic about exhaust contaminating intake charge when there is a blower constantly pumping air in the correct direction through the engine.
Out the exhaust, yes...but back into the intake, perhaps less likely.
Easiest and cheapest thing to try. Spin that damn blower harder !
03-17-2010, 12:43 PM
#44
You NEED to take pressure readings before and after the intercooler. When I switched from a T-trim @ 13 psi to a turbo at 21 psi, my vortech aftercoler became a restriction. I was losing around 4 psi through the intercooler alone.
Jim
03-17-2010, 02:40 PM
#45
I was actually thinking you're making great power for your setup...everything I've seen of the boosted LT1's I've tuned, says those numbers are great for what you've got.
I agree the CR is low...but I also feel that means that it will probably LOVE more boost...which makes me then agree with the guys saying spin the blower harder...however, before you do that, check with Vortech about the RPM ratings of the blower, and then see what kind of RPM you're already turning it to at your rev limiter...and then make sure your pulley change won't go too high and blow it up...and I also agree on taking some inlet pressure readings before and after the cooler...I don't think you'll see too much pressure differential...but it's good to know before you start pushing the blower harder...just how much harder you might HAVE to push it to get something meaningful from it.
I agree the CR is low...but I also feel that means that it will probably LOVE more boost...which makes me then agree with the guys saying spin the blower harder...however, before you do that, check with Vortech about the RPM ratings of the blower, and then see what kind of RPM you're already turning it to at your rev limiter...and then make sure your pulley change won't go too high and blow it up...and I also agree on taking some inlet pressure readings before and after the cooler...I don't think you'll see too much pressure differential...but it's good to know before you start pushing the blower harder...just how much harder you might HAVE to push it to get something meaningful from it.
03-17-2010, 05:20 PM
#49
Thanks, DeltaT.
Measuring intercooler dP is way cheaper and easier than swapping cams or pistons.
People have made ridiculous power with the YSi in race classes, and they all use positively monstrous camshafts. You're probably missing some low-end and driveability, but not horsepower.
As for the compression, everyone is jumping on that because it's a tad lower than normal. I've run several motors in the 8.3 - 8.5 range and they ran well. Someone stated a 3% power loss from every full point of compression, which is pretty accurate from what I've seen. That said, you're only missing 1.5 - 2% power vs someone running 8.5 (like the vast majority of OEM FI cars). That's in the neighborhood of 15 hp. If you bump it all the way up to 9/1, you'd gain about 30 hp, but might have to dial back timing. That YSi was meant to make more boost, so I'd vote for that route.
Mike
Measuring intercooler dP is way cheaper and easier than swapping cams or pistons.
People have made ridiculous power with the YSi in race classes, and they all use positively monstrous camshafts. You're probably missing some low-end and driveability, but not horsepower.
As for the compression, everyone is jumping on that because it's a tad lower than normal. I've run several motors in the 8.3 - 8.5 range and they ran well. Someone stated a 3% power loss from every full point of compression, which is pretty accurate from what I've seen. That said, you're only missing 1.5 - 2% power vs someone running 8.5 (like the vast majority of OEM FI cars). That's in the neighborhood of 15 hp. If you bump it all the way up to 9/1, you'd gain about 30 hp, but might have to dial back timing. That YSi was meant to make more boost, so I'd vote for that route.
Mike
03-18-2010, 12:57 AM
#52
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I was thinking that right off the bat.For sure run some tests before you spend money.Not saying anyones wrong here jus start with the cheaper stuff like get all the data you can bout the way its runnin then throw some common sense in the mix cause there is probably more then one issue that could be improved upon.
03-18-2010, 04:28 AM
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the title is misleading this is what I think
I'm not an expert and I'll start talking $h!t using some calculationand hints and see if anybody agrees with me
671rwhp@6500 @ 12 Psi (from log file) means 671 @ 12 psi + 14.7psi atmosphere = 26.7 psi
that's 396ci made about (370 rwhp @ 14.7 psi atmosphere @ 8.0:1 CR even if it was 9.0:1 CR they are still not so far numbers on)
FI motor
396ci @8.0:1 + 14.7 atmosphere + 18 psi YSI - restriction of the small after cooler = 820+ rwhp that is at least 900 fwhp on a manual car with a heavy clutch
from log file I think there is little belt slippage at this boost and I think you should consider cog belt set up
if the boost readings before and after the cooler is almost identical your are running a restriction. there must be a pressure drop of at least 2 psi after the cooler no matter how good they say the design is
thinking of 1000 cfm @ 18 psi and 600 cfm @ 18 psi
I am start even thinking of compressor surge and boost just starting building up and leaking back to compressor
If it was me:
I think I will run my motor without the cooler at 12 psi with no cooler and see what I got since the motor CR is in the low and safe area to run 95 gas and see if I pick any numbers
pump the boost to 18 - 20 psi using cog belt set up + water injection
and I think you will see around 900 rwhp with the unit you have
AmjadZ28SS
I've just started to learn the stuff
I'm not an expert and I'll start talking $h!t using some calculationand hints and see if anybody agrees with me
671rwhp@6500 @ 12 Psi (from log file) means 671 @ 12 psi + 14.7psi atmosphere = 26.7 psi
that's 396ci made about (370 rwhp @ 14.7 psi atmosphere @ 8.0:1 CR even if it was 9.0:1 CR they are still not so far numbers on)
FI motor
396ci @8.0:1 + 14.7 atmosphere + 18 psi YSI - restriction of the small after cooler = 820+ rwhp that is at least 900 fwhp on a manual car with a heavy clutch
from log file I think there is little belt slippage at this boost and I think you should consider cog belt set up
if the boost readings before and after the cooler is almost identical your are running a restriction. there must be a pressure drop of at least 2 psi after the cooler no matter how good they say the design is
thinking of 1000 cfm @ 18 psi and 600 cfm @ 18 psi
I am start even thinking of compressor surge and boost just starting building up and leaking back to compressor
If it was me:
I think I will run my motor without the cooler at 12 psi with no cooler and see what I got since the motor CR is in the low and safe area to run 95 gas and see if I pick any numbers
pump the boost to 18 - 20 psi using cog belt set up + water injection
and I think you will see around 900 rwhp with the unit you have
AmjadZ28SS
I've just started to learn the stuff
03-19-2010, 05:42 AM
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I,ve got some e-mail replies:
www.golenengineservice.com
"Is this an LT1?If so the compression is way too low, we normally run 9.5:1 compression and the total timing is way to high we normally run it at 26degrees with 15 psi of boost. But 671 RWHP is pretty big power.Yes the cam is way too big to say the least, you would never want to use a cam with that big of a duration. I did not look up the grind # until now so I would install a much smaller cam like a 224/230 or so."
www.guerragroup.com
"The cam looks like it has too much overlap for a blower motor. The timing seems too high for a boost application (even with race fuel). I would have expected to see a duration closer to the low to mid 230s on intake and high 240s or low 250s on exhaust with an LSA around 115"
Patrick Guerra
www.golenengineservice.com
"Is this an LT1?If so the compression is way too low, we normally run 9.5:1 compression and the total timing is way to high we normally run it at 26degrees with 15 psi of boost. But 671 RWHP is pretty big power.Yes the cam is way too big to say the least, you would never want to use a cam with that big of a duration. I did not look up the grind # until now so I would install a much smaller cam like a 224/230 or so."
www.guerragroup.com
"The cam looks like it has too much overlap for a blower motor. The timing seems too high for a boost application (even with race fuel). I would have expected to see a duration closer to the low to mid 230s on intake and high 240s or low 250s on exhaust with an LSA around 115"
Patrick Guerra
03-21-2010, 12:34 PM
#56
If you want to lose hp, then go ahead and put in a smaller camshaft.
As for the compression, your cylinder pressure is quite low right now. You have 2 options to raise it: raise boost, or raise compression. Boost will always make more power than compression, which is why you are in this forum to begin with. It's your choice.
Or, just check intercooler dP.
I'm honestly surprised that a) you haven't attacked the intercooler, which was never meant for that flow rate, b) people actually thing putting in a smaller camshaft will gain power, and c) people are recommending raising compression rather than boost.
As for the compression, your cylinder pressure is quite low right now. You have 2 options to raise it: raise boost, or raise compression. Boost will always make more power than compression, which is why you are in this forum to begin with. It's your choice.
Or, just check intercooler dP.
I'm honestly surprised that a) you haven't attacked the intercooler, which was never meant for that flow rate, b) people actually thing putting in a smaller camshaft will gain power, and c) people are recommending raising compression rather than boost.
03-21-2010, 09:11 PM
#57
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Did few check and here is what I found so far:
1- sprark plug for cyl# 6 was lose..not even hand tight.
2- Cylindrs pressure was 135 psi.
3- I think that my y-pipe is restrictive,the vrtex inserts I've put in there to reduce the noise was a bad idea.they where welded inplace and the came off just after two puls on the dyno. So, they are coming out and the y pipe is going to be altered.
4- the cooler is definitaly going to be changed.But before that I am going to do a dyno run with the new y-pipe and i will check the pressure before and after the cooler.I have this cooler fitted because- I alredy have it, bought it years ago for different setup- I want to see how much is it realy capable of cooling discharge air.and it did realy well- temp drop from 44 deg C to 24 deg - that with ice in the tank.soon we will fine out how restrictive it is. Vortech aftercooler pdf file says it for vehicle making approximately 580hp!
1- sprark plug for cyl# 6 was lose..not even hand tight.
2- Cylindrs pressure was 135 psi.
3- I think that my y-pipe is restrictive,the vrtex inserts I've put in there to reduce the noise was a bad idea.they where welded inplace and the came off just after two puls on the dyno. So, they are coming out and the y pipe is going to be altered.
4- the cooler is definitaly going to be changed.But before that I am going to do a dyno run with the new y-pipe and i will check the pressure before and after the cooler.I have this cooler fitted because- I alredy have it, bought it years ago for different setup- I want to see how much is it realy capable of cooling discharge air.and it did realy well- temp drop from 44 deg C to 24 deg - that with ice in the tank.soon we will fine out how restrictive it is. Vortech aftercooler pdf file says it for vehicle making approximately 580hp!
Last edited by kazdevil; 03-22-2010 at 08:06 AM.
03-22-2010, 10:35 AM
#58
Damn Kaz. You've got two professionals that both said your cam is TOO ******* BIG. You can waste your time monkeying around with all the other parts in the system, but if your cam ain't right you're motor's never going to reach it's true potential no matter what improvements you make.
