5.3L build 862 vs 317 heads (compression)??
11-22-2011, 01:10 AM
#21
Who builds a turbo car to take advantage of the low compression out of boost power by running a tiny cam and small intake, low gears???? No one.
Drivability of my car I couldnt have cared less because of low compression when it was a 5.3 w/ 317s, its a turbo car and I want it to work in its entirety. low compression = slower spool time.
You want to run 20psi through a low compression setup w/ E85? With more compression, a larger turbo, you'd spool it up, make the same power with less boost.
And E85 you shouldnt need the low compression....thats the wonder of it.
N/A Dyno graphs dont mean ****... go drive a car with a 8.6:1 compression turbo 5.3L in it and see.
Drivability of my car I couldnt have cared less because of low compression when it was a 5.3 w/ 317s, its a turbo car and I want it to work in its entirety. low compression = slower spool time.
You want to run 20psi through a low compression setup w/ E85? With more compression, a larger turbo, you'd spool it up, make the same power with less boost.
And E85 you shouldnt need the low compression....thats the wonder of it.
N/A Dyno graphs dont mean ****... go drive a car with a 8.6:1 compression turbo 5.3L in it and see.
11-22-2011, 06:10 AM
#22
I think you've mis-interpretted the intent of my post.
Why would an NA graph not mean anything when the topic it was addressing was off-boost torque? As you'll see, most comments in this thread are just saying that they felt the 8.6:1 CR had poor off-boost (NA) performance. My point was that it would still be terrible even if the CR was 9.5:1. A 5.3L out of boost is just not going to knock your socks off.
As for 'in boost' performance, I'm still doing some analysis to see which route I will go. I'm mostly looking at simulated piston surface temps at a given power level (900 crank hp)- with varying combinations of compression ratio, boost, and the 3 cams I have in my garage. What I'm hoping to see is that more boost, lower CR yields lower combustion temperatures than less boost, higher CR. I could be completely wrong though - or it may be a wash.
I have not finished my analysis, but I have a feeling I will likely run the 317's on my 5.3. Partly because the car has an F1A Procharger and thus I have to make up the 90-110 hp required to drive the blower. i.e. making 700 rwhp will stress the motor like it's making near 800 rwhp. I would like to do everything I can to keep the motor together for a little while at the 700 rwhp level and I'm thinking the low CR will aid this.
Secondly, the car has a 4400 stall and a TH400 so, any pedal is going to negate any concerns of off-boost performance anyways.
As for spool time vs. CR. I have always been a bit suspect that it's as much of a driver as people believe. What drives a turbine is mass flow and temperature extraction accross the turbine. Mass flow is not going to be affected at all by changes to CR. A higher CR will result in a higher inlet temp to the turbine however. So, I could see this having some impact - I had just assumed this would be pretty negligible. When i finish my procharger analysis, I will have to build a turbocharged engine model and do some transient analysis of turbine acceleration as a function of CR.
Why would an NA graph not mean anything when the topic it was addressing was off-boost torque? As you'll see, most comments in this thread are just saying that they felt the 8.6:1 CR had poor off-boost (NA) performance. My point was that it would still be terrible even if the CR was 9.5:1. A 5.3L out of boost is just not going to knock your socks off.
As for 'in boost' performance, I'm still doing some analysis to see which route I will go. I'm mostly looking at simulated piston surface temps at a given power level (900 crank hp)- with varying combinations of compression ratio, boost, and the 3 cams I have in my garage. What I'm hoping to see is that more boost, lower CR yields lower combustion temperatures than less boost, higher CR. I could be completely wrong though - or it may be a wash.
I have not finished my analysis, but I have a feeling I will likely run the 317's on my 5.3. Partly because the car has an F1A Procharger and thus I have to make up the 90-110 hp required to drive the blower. i.e. making 700 rwhp will stress the motor like it's making near 800 rwhp. I would like to do everything I can to keep the motor together for a little while at the 700 rwhp level and I'm thinking the low CR will aid this.
Secondly, the car has a 4400 stall and a TH400 so, any pedal is going to negate any concerns of off-boost performance anyways.
As for spool time vs. CR. I have always been a bit suspect that it's as much of a driver as people believe. What drives a turbine is mass flow and temperature extraction accross the turbine. Mass flow is not going to be affected at all by changes to CR. A higher CR will result in a higher inlet temp to the turbine however. So, I could see this having some impact - I had just assumed this would be pretty negligible. When i finish my procharger analysis, I will have to build a turbocharged engine model and do some transient analysis of turbine acceleration as a function of CR.
11-22-2011, 09:24 AM
#24
As for spool time vs. CR. I have always been a bit suspect that it's as much of a driver as people believe. What drives a turbine is mass flow and temperature extraction accross the turbine. Mass flow is not going to be affected at all by changes to CR. A higher CR will result in a higher inlet temp to the turbine however. So, I could see this having some impact - I had just assumed this would be pretty negligible. When i finish my procharger analysis, I will have to build a turbocharged engine model and do some transient analysis of turbine acceleration as a function of CR.
11-22-2011, 03:45 PM
#25
No one in this thread has said that they have actually swapped heads and compared (just that they are going to, or that they think the stock heads wouldbe better). Everyone says the 8.6:1 CR 5.3 is a dog out of boost. I'm just saying it will still be a dog at 9.5:1 CR as it's not going to pick up a lot of torque - I don't think anyone would disagree with that.
And I think we all agree that more CR will make more power under boost - just at some expense of 'reliability'.
71 Chevy did make the point that part throttle performance is a factor though (and this might be more so what people are referring to). He's correct in that you won't really be able to get a feel for that from a WOT dyno graph.
Good point. I was incorrect in my assertion. Stupid thermodynamic efficiency...
11-22-2011, 06:34 PM
#26
Test vehicles ive done
My car. 5.3L w/ 317 heads GT45 turbo. Vic jr intake, TH350, 224/224 cam 4000 stall, Dog off boost
Friends car. Daily driver- 5.3L w/ 317 heads, Stock cam, stock intake, MPT70, T56, dog off boost. Changed to .68 hot side, still a pooch off boost but spooled a little faster.
Another friends vehicle. 5.3L STOCK HEADS, MPT70 /.68 housing, stock cam, stock intake, TH400, Behaved more like a factory vehicle... no sluggishness like the low compression setups.
With the stock 5.3 heads its just like driving a chevy truck with a 5.3 in it, with the 317 heads on them it was like driving the same truck pulling a trailer with a car on it.. Thats about all i can think of to compare it to. Response is just slower and sluggish.
I will say I did like the people laughing at my car because it sounded like it had 200hp and they didnt know it was turbocharged.
You can see in this video how weak my car was..... Look at it trying to do a burn out in the at 3:30 in this video is a perfect example... trying to get the tires to initially start spinning in the burn out box...lol. It was such a dog.
http://www.streetfire.net/video/72-n...-il_187976.htm
My car. 5.3L w/ 317 heads GT45 turbo. Vic jr intake, TH350, 224/224 cam 4000 stall, Dog off boost
Friends car. Daily driver- 5.3L w/ 317 heads, Stock cam, stock intake, MPT70, T56, dog off boost. Changed to .68 hot side, still a pooch off boost but spooled a little faster.
Another friends vehicle. 5.3L STOCK HEADS, MPT70 /.68 housing, stock cam, stock intake, TH400, Behaved more like a factory vehicle... no sluggishness like the low compression setups.
With the stock 5.3 heads its just like driving a chevy truck with a 5.3 in it, with the 317 heads on them it was like driving the same truck pulling a trailer with a car on it.. Thats about all i can think of to compare it to. Response is just slower and sluggish.
I will say I did like the people laughing at my car because it sounded like it had 200hp and they didnt know it was turbocharged.
You can see in this video how weak my car was..... Look at it trying to do a burn out in the at 3:30 in this video is a perfect example... trying to get the tires to initially start spinning in the burn out box...lol. It was such a dog.
http://www.streetfire.net/video/72-n...-il_187976.htm
11-22-2011, 08:38 PM
#27
some reason your link doesnt work for me,it tries to go to the site but then stops...really like to see the response dif between the heads,i like how my dads tahoe feels NA,would love to keep that feel and boost.. would a T6 turbo flange help any.
11-22-2011, 09:53 PM
#28
11-22-2011, 10:08 PM
#29
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im running my ported ls6 heads (factory cc's). curious to see how it reacts out of boost. was going to run the stock 5.3 heads but figured may as well use the ported ls6's. its the least amount of compression drop available in a stock head. think it puts it around 9.1
11-23-2011, 07:38 AM
#31
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Larger combustion chambers are always a welcomed enhancement for a boosted motor, which is why I bought a pair of 317's. I will also be picking up a set of Wiseco 5.3 (3.800") pistons which will drop my CR to 9.3:1.
8.6:1 is entirely too low and would negate any of your efforts to gain performance while not on boost. Honestly, that low of a CR should be reserved for those who want to run 40+ psi up to 7500rpm.
8.6:1 is entirely too low and would negate any of your efforts to gain performance while not on boost. Honestly, that low of a CR should be reserved for those who want to run 40+ psi up to 7500rpm.
11-23-2011, 11:42 AM
#35
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I feel like I am qualified to respond as I ran an 8:1 348 cid with a super charger (YSi) and then swapped the cam out and moved to a turbo setup (GT47-88, 88mm T6).
My 348 cid combo used mildly ported 317's. With my TH400 and transbrake, the car came up on boost quickly. I personally believe that a supercharger combo will not be the same as the turbo combo.
I then swapped cam and converter and went with an 88mm combo. If you look around the 47-88 and YSi both are capable of low 8's so they are somewhat comparable.
The turbo combo was a total dog. Took me a long time to get up on boost on the 'brake. Car was a turd from a roll unless I raced someone while I was around 4000 rpms in 2nd gear...
Now if you ask me, I would not reccomend going below 9:1 with smaller cubes. Now if you had a 427 cid engine and wanted to do 8.5:1 that's a different story. But for a 5.3 or 5.7, for sure a 4.8, I would stay between 9:1 and 10:1. If you go 8:1 like me, the engine struggles to get up on power and you'll have to run 1-3 more lbs of boost just to make the same power as you would at 10:1.
a stock 5.3 is 9.5:1 I believe, I would leave it. If you are going to run say up to 15 psi, you can get there with pump gas9 and meth/alky. A stock 5.3 makes 300-350rwhp with boltons, so figure at 10 psi you could be making 575rwhp, and 15 psi you could be making 650-700rwhp.
Remember in the older days of forced induction, folks ran lower compression because the heads and block were iron, and retained heat. We now have engine technology that is far superior.
For most of the 5.3 builds I see folks talking about, they'd be happy with 600rwhp for a long time. Heck I went 9.40@143 @ 3500, 680rwhp, blower, 18 psi, 1.35 on a 28x10.5. With the turbo I went 10.00@139 on a 1.5 at 16 psi on a license pass. Had I left harder I would have went 9.8@142 I think.
For these 5.3 builds, do a set of ARP head studs, consider doing a cam, look into whether the LS9 style head gaskets would work and are better than MLS, and don't dick around with the compression too much. You need it. Look at that other Hot Rod article, where he tests how much value he gets from running more camshaft. More cam = more power with the power adder combo too.
If anyone is really curious here is some more data:
YSi:
236/246/113
LS6 intake
21 psi 754rwhp
18 psi 680rwhp
680rwhp = 9.4@143, 5.9x, 116mph, 3500, 1.35 (had belt issues I had a custom setup)
88MM T6:
235/235/113
LS2 intake
Made 867rwhp, I dont' recall boost, 25 I think? Jim Moran (intmd8)might remember
9.44@144, 1.35, 3450, boost level not sure broke stuff
10.0@139, 1.57, 3450, 16 psi on controller
Also Jim told me not to do 8:1, and he was right. I'm not sure if I ever told him he was right, I'm doing it now.
My 348 cid combo used mildly ported 317's. With my TH400 and transbrake, the car came up on boost quickly. I personally believe that a supercharger combo will not be the same as the turbo combo.
I then swapped cam and converter and went with an 88mm combo. If you look around the 47-88 and YSi both are capable of low 8's so they are somewhat comparable.
The turbo combo was a total dog. Took me a long time to get up on boost on the 'brake. Car was a turd from a roll unless I raced someone while I was around 4000 rpms in 2nd gear...
Now if you ask me, I would not reccomend going below 9:1 with smaller cubes. Now if you had a 427 cid engine and wanted to do 8.5:1 that's a different story. But for a 5.3 or 5.7, for sure a 4.8, I would stay between 9:1 and 10:1. If you go 8:1 like me, the engine struggles to get up on power and you'll have to run 1-3 more lbs of boost just to make the same power as you would at 10:1.
a stock 5.3 is 9.5:1 I believe, I would leave it. If you are going to run say up to 15 psi, you can get there with pump gas9 and meth/alky. A stock 5.3 makes 300-350rwhp with boltons, so figure at 10 psi you could be making 575rwhp, and 15 psi you could be making 650-700rwhp.
Remember in the older days of forced induction, folks ran lower compression because the heads and block were iron, and retained heat. We now have engine technology that is far superior.
For most of the 5.3 builds I see folks talking about, they'd be happy with 600rwhp for a long time. Heck I went 9.40@143 @ 3500, 680rwhp, blower, 18 psi, 1.35 on a 28x10.5. With the turbo I went 10.00@139 on a 1.5 at 16 psi on a license pass. Had I left harder I would have went 9.8@142 I think.
For these 5.3 builds, do a set of ARP head studs, consider doing a cam, look into whether the LS9 style head gaskets would work and are better than MLS, and don't dick around with the compression too much. You need it. Look at that other Hot Rod article, where he tests how much value he gets from running more camshaft. More cam = more power with the power adder combo too.
If anyone is really curious here is some more data:
YSi:
236/246/113
LS6 intake
21 psi 754rwhp
18 psi 680rwhp
680rwhp = 9.4@143, 5.9x, 116mph, 3500, 1.35 (had belt issues I had a custom setup)
88MM T6:
235/235/113
LS2 intake
Made 867rwhp, I dont' recall boost, 25 I think? Jim Moran (intmd8)might remember
9.44@144, 1.35, 3450, boost level not sure broke stuff
10.0@139, 1.57, 3450, 16 psi on controller
Also Jim told me not to do 8:1, and he was right. I'm not sure if I ever told him he was right, I'm doing it now.
Last edited by Pro Stock John; 11-23-2011 at 11:54 AM.
11-23-2011, 12:29 PM
#37
TECH Senior Member
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I feel like I am qualified to respond as I ran an 8:1 348 cid with a super charger (YSi) and then swapped the cam out and moved to a turbo setup (GT47-88, 88mm T6).
My 348 cid combo used mildly ported 317's. With my TH400 and transbrake, the car came up on boost quickly. I personally believe that a supercharger combo will not be the same as the turbo combo.
I then swapped cam and converter and went with an 88mm combo. If you look around the 47-88 and YSi both are capable of low 8's so they are somewhat comparable.
The turbo combo was a total dog. Took me a long time to get up on boost on the 'brake. Car was a turd from a roll unless I raced someone while I was around 4000 rpms in 2nd gear...
Now if you ask me, I would not reccomend going below 9:1 with smaller cubes. Now if you had a 427 cid engine and wanted to do 8.5:1 that's a different story. But for a 5.3 or 5.7, for sure a 4.8, I would stay between 9:1 and 10:1. If you go 8:1 like me, the engine struggles to get up on power and you'll have to run 1-3 more lbs of boost just to make the same power as you would at 10:1.
a stock 5.3 is 9.5:1 I believe, I would leave it. If you are going to run say up to 15 psi, you can get there with pump gas9 and meth/alky. A stock 5.3 makes 300-350rwhp with boltons, so figure at 10 psi you could be making 575rwhp, and 15 psi you could be making 650-700rwhp.
Remember in the older days of forced induction, folks ran lower compression because the heads and block were iron, and retained heat. We now have engine technology that is far superior.
For most of the 5.3 builds I see folks talking about, they'd be happy with 600rwhp for a long time. Heck I went 9.40@143 @ 3500, 680rwhp, blower, 18 psi, 1.35 on a 28x10.5. With the turbo I went 10.00@139 on a 1.5 at 16 psi on a license pass. Had I left harder I would have went 9.8@142 I think.
For these 5.3 builds, do a set of ARP head studs, consider doing a cam, look into whether the LS9 style head gaskets would work and are better than MLS, and don't dick around with the compression too much. You need it. Look at that other Hot Rod article, where he tests how much value he gets from running more camshaft. More cam = more power with the power adder combo too.
If anyone is really curious here is some more data:
YSi:
236/246/113
LS6 intake
21 psi 754rwhp
18 psi 680rwhp
680rwhp = 9.4@143, 5.9x, 116mph, 3500, 1.35 (had belt issues I had a custom setup)
88MM T6:
235/235/113
LS2 intake
Made 867rwhp, I dont' recall boost, 25 I think? Jim Moran (intmd8)might remember
9.44@144, 1.35, 3450, boost level not sure broke stuff
10.0@139, 1.57, 3450, 16 psi on controller
Also Jim told me not to do 8:1, and he was right. I'm not sure if I ever told him he was right, I'm doing it now.
My 348 cid combo used mildly ported 317's. With my TH400 and transbrake, the car came up on boost quickly. I personally believe that a supercharger combo will not be the same as the turbo combo.
I then swapped cam and converter and went with an 88mm combo. If you look around the 47-88 and YSi both are capable of low 8's so they are somewhat comparable.
The turbo combo was a total dog. Took me a long time to get up on boost on the 'brake. Car was a turd from a roll unless I raced someone while I was around 4000 rpms in 2nd gear...
Now if you ask me, I would not reccomend going below 9:1 with smaller cubes. Now if you had a 427 cid engine and wanted to do 8.5:1 that's a different story. But for a 5.3 or 5.7, for sure a 4.8, I would stay between 9:1 and 10:1. If you go 8:1 like me, the engine struggles to get up on power and you'll have to run 1-3 more lbs of boost just to make the same power as you would at 10:1.
a stock 5.3 is 9.5:1 I believe, I would leave it. If you are going to run say up to 15 psi, you can get there with pump gas9 and meth/alky. A stock 5.3 makes 300-350rwhp with boltons, so figure at 10 psi you could be making 575rwhp, and 15 psi you could be making 650-700rwhp.
Remember in the older days of forced induction, folks ran lower compression because the heads and block were iron, and retained heat. We now have engine technology that is far superior.
For most of the 5.3 builds I see folks talking about, they'd be happy with 600rwhp for a long time. Heck I went 9.40@143 @ 3500, 680rwhp, blower, 18 psi, 1.35 on a 28x10.5. With the turbo I went 10.00@139 on a 1.5 at 16 psi on a license pass. Had I left harder I would have went 9.8@142 I think.
For these 5.3 builds, do a set of ARP head studs, consider doing a cam, look into whether the LS9 style head gaskets would work and are better than MLS, and don't dick around with the compression too much. You need it. Look at that other Hot Rod article, where he tests how much value he gets from running more camshaft. More cam = more power with the power adder combo too.
If anyone is really curious here is some more data:
YSi:
236/246/113
LS6 intake
21 psi 754rwhp
18 psi 680rwhp
680rwhp = 9.4@143, 5.9x, 116mph, 3500, 1.35 (had belt issues I had a custom setup)
88MM T6:
235/235/113
LS2 intake
Made 867rwhp, I dont' recall boost, 25 I think? Jim Moran (intmd8)might remember
9.44@144, 1.35, 3450, boost level not sure broke stuff
10.0@139, 1.57, 3450, 16 psi on controller
Also Jim told me not to do 8:1, and he was right. I'm not sure if I ever told him he was right, I'm doing it now.
I wonder why the turbo combo didn't pick up much over the blower. I guess it picked up a little, since it made the same power with less boost?
My 70 GTO used to have a 502 with 8.75:1 compression, NA. I know it's not exactly apples to apples but take it for what it is. That engine wasn't a dog at all. It made 600HP and trapped 116 mph in a 4200 pounds car.
Andrew
11-23-2011, 01:00 PM
#38
LS1Tech Co-Founder
iTrader: (34)
I can't really make too many comparisons from a performance standpoint. Had I run a gear drive setup like the ones available now, it would have been possible to see what 25 psi would have yielded with both combos. Ultimately I think the blower combo used more power but it was easier to stage and launch. The blower combo came up really fast on power and launched hard. My turbo combo took 10 times longer to stage was also a lot less fun on the street. But I'm certainly not saying all turbo combos are like that, many are not.
11-23-2011, 01:17 PM
#39
Not sure you want to take off that much material off the deck of the head
You might end up weakening the head and blowing gaskets.
Plus, the machine shop is going to charge you $100 per head to wack off that much.
Cheaper and safer to get some stock 5.3/4.8 heads....
Just my .02 cents