stock 5.3 vs stock LQ4, which is better for high boost?
10-25-2012, 01:20 AM
#62
That was once my entire thinking as well. But now it seems there is more to it than that.
If I end up running the PT7675, it seems (via skinnies) that the 5.3 will be the better suited engine as it will make more power on it than the larger 41 cubic inch LQ4.
Now, my next question is; what about the S475? Would the S475 have any advantage on the LQ4 vs the PT7675 on the 5.3? I may be splitting atoms on this one.
The extra deck thickness on the 5.3 also seems to have its appeal.
If I end up running the PT7675, it seems (via skinnies) that the 5.3 will be the better suited engine as it will make more power on it than the larger 41 cubic inch LQ4.
Now, my next question is; what about the S475? Would the S475 have any advantage on the LQ4 vs the PT7675 on the 5.3? I may be splitting atoms on this one.
The extra deck thickness on the 5.3 also seems to have its appeal.
pound of boost per pound of boost, the 6.0 will make more than the 5.3.
at 15psi, the 6.0 is up more than 100hp over the 5.3
either one will be limited to a certain hp, due to lifting heads, powder metal rods,etc. but,the 6.0 will give you the advantage of faster spool,and better throttle response.
10-25-2012, 01:25 AM
#64
About a week and a half ago I burnt a piston in my JY 6.0. The fastest it went was 10.75 @ 131 in my 3600# cutlass. I'm gonna swap to a JY 5.3 with the same exact setup and compare the two.
Mods:
LS6 cam
Springs & pushrods to match
Victor Jr intake
750 blow thru carb
Garrett GT42-94R
Open 4" downpipe about 5 feet long.
It went 10.75 with a powerglide, car now has a th400
Anyone care to venture a guess of if I will gain or lose ET?
Mods:
LS6 cam
Springs & pushrods to match
Victor Jr intake
750 blow thru carb
Garrett GT42-94R
Open 4" downpipe about 5 feet long.
It went 10.75 with a powerglide, car now has a th400
Anyone care to venture a guess of if I will gain or lose ET?
at the same psi, you will go slower. add a few pounds of boost and it will e.t the same.
i have the 99-03 6.0 rod piston combos if your buyer needs one or more.$15 plus shipping
10-25-2012, 07:50 AM
#65
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Wouldn't a 4.8 be an even better platform than a 5.3 as far as longevity? It has the same benefits of the 5.3's bore thickness/ head seating surface with a shorter stroke to boot. Plus its that much cheaper. Just thinking out loud here. Pretty educational thread 
10-25-2012, 08:48 AM
#66
I contacted ERL and they are building me a sleeved down 6.0 with 1" bores, its going to have mad thick cylinder walls and the heads hold crazy pressure with the insane sealing surface. Its so much sealing surface that I only have to use one head bolt per side. I'll be able to run 100psi on 87 octane its such a genius idea, only 37 cubic inches but its going to be totally optimal for a street car. Who cares about part throttle torque or anything like that, I drive on the street at full throttle all the time like most of you. 
10-25-2012, 09:20 AM
#67
Look at the lsx block with the larger bore they went to the 6 bolt per cylinder to allow additional strength with the larger bore.. More surface area to mate will yield increased strength. Cylinder pressure is cylinder pressure. A 6.0 making 1000 hp is doing the same 125 hp per cylinder as a 5.3 making 1000 hp (and similar cylinder pressure) but with less mating surface. Ideally you would build a sleeved motor but we are talking stock vs stock.
10-25-2012, 09:45 AM
#68
that said, the 4.8 is a nice platform. you can rev the snot out of it, and I dont think it really gives up anything to the 5.3 since you can rev it higher to compensate for the lower cubic inches
10-25-2012, 10:07 AM
#69
Look at the lsx block with the larger bore they went to the 6 bolt per cylinder to allow additional strength with the larger bore.. More surface area to mate will yield increased strength. Cylinder pressure is cylinder pressure. A 6.0 making 1000 hp is doing the same 125 hp per cylinder as a 5.3 making 1000 hp (and similar cylinder pressure) but with less mating surface. Ideally you would build a sleeved motor but we are talking stock vs stock.
Im looking for examples of where the 6.0 sealing has been inadequate, where the 5.3 would have been adequate.
Im not knocking the 5.3. it is amazing. but the 6.0 is better imo. if it takes a 5.3 20 psi to make 1000, but the 6.0 only needs 15 psi, you are putting less heat in the motor, can run more optimal timing, less bore shrouding, working the turbo(s) less, etc etc.
10-25-2012, 10:12 AM
#70
Kinda hard to say isn't it as you would have to have 2 exact motor combos both making the same hp and see which one pops a head gasket first. I have seen numerous threads with lifted heads on both 6.0 and 5.3 but I would guess the tune was more the issue or the fuel than the mating surface. *shrug*
Personally I like that little extra safety margin and a little lighter rotating mass of the 5.3
Personally I like that little extra safety margin and a little lighter rotating mass of the 5.3
10-25-2012, 01:38 PM
#71
If they will make similar power, then it seems more cost efficient, more factory deck surface, and less weight to go with the 5.3 combo.
The one thing I would also like to know between combos at that point is drivability. Spool time. If the 5.3 and 7675 combo will not have as much lag, it might also help dictate what would be better. Unfortunately for this, I would have to essentially find both combos and see them (or at least WOT vids) next to each other to really see the difference. Unless anyone happens to know what the characteristics would be vs each other.
i have heard it said, "you dont build the combo around the turbo, but the turbo around the combo". the exception of course is if you are class racing and limited to a specific size.
pound of boost per pound of boost, the 6.0 will make more than the 5.3.
at 15psi, the 6.0 is up more than 100hp over the 5.3
either one will be limited to a certain hp, due to lifting heads, powder metal rods,etc. but,the 6.0 will give you the advantage of faster spool,and better throttle response.
pound of boost per pound of boost, the 6.0 will make more than the 5.3.
at 15psi, the 6.0 is up more than 100hp over the 5.3
either one will be limited to a certain hp, due to lifting heads, powder metal rods,etc. but,the 6.0 will give you the advantage of faster spool,and better throttle response.
I would like to see the two stacked up to each other dyno sheet to dyno sheet for comparison if you would happen to be able to post that.
10-25-2012, 03:17 PM
#72
say a good cammed 5.3 makes 450 na. 450/323 is 1.393 hp per CI
transfer that to a 6.0 (1.393 *364) is 507hp.
NA, thats a difference of about 57hp. now double that for 15psi(15 psi is about double atmospheric pressure) and you get about a 114 hp advantage that the 6.0 will have over the 5.3
there are many 5.3 and 6.0 dyno sheets you can find but they wont tell you a lot about part throttle driveability, or about getting up on the converter etc
10-25-2012, 04:14 PM
#75
I contacted ERL and they are building me a sleeved down 6.0 with 1" bores, its going to have mad thick cylinder walls and the heads hold crazy pressure with the insane sealing surface. Its so much sealing surface that I only have to use one head bolt per side. I'll be able to run 100psi on 87 octane its such a genius idea, only 37 cubic inches but its going to be totally optimal for a street car. Who cares about part throttle torque or anything like that, I drive on the street at full throttle all the time like most of you.
Just remember folks, nobody cares about part throttle and spool it's all about the WOT. Oh yeah, everybody runs E85 or Q16 too so go as small as possible and hit that 6.0 PR it'll take it!
10-25-2012, 04:46 PM
#76
say a good cammed 5.3 makes 450 na. 450/323 is 1.393 hp per CI
transfer that to a 6.0 (1.393 *364) is 507hp.
NA, thats a difference of about 57hp. now double that for 15psi(15 psi is about double atmospheric pressure) and you get about a 114 hp advantage that the 6.0 will have over the 5.3
transfer that to a 6.0 (1.393 *364) is 507hp.
NA, thats a difference of about 57hp. now double that for 15psi(15 psi is about double atmospheric pressure) and you get about a 114 hp advantage that the 6.0 will have over the 5.3
Can someone explain how some turbo setups make more power on smaller displacement engines? My friend had mentioned that the same turbo on a 3.0 2JZ (Supra motor) can make quite a bit more power than on a larger displacement motor (like a 5.3 or 6.0 for that matter). This almost makes sense to me as after looking a bit more on here on some similar turbo and boost #'s but 6.0 vs 5.3 I am definately NOT seeing the extra 100+ HP numbers on the LQ4's over the 5.3's.
If that is the case, wouldn't the same hold true for making more power on the 5.3 than the 6.0? I do understand more CI = more power N/A at least. Just trying to figure the logic on the boost.
10-25-2012, 05:07 PM
#79
I understand the math you posted. What I don't understand is why you think a 6.0 will make more hp than a 5.3 if the only difference is bore size. Sure, less valve shrouding will make a little more power but certainly not almost a 60hp difference. They will make about the same power, albeit with different curves.
10-25-2012, 05:35 PM
#80
a turbo will flow its maximum at a specific pressure ratio. IF, the turbo is too small for the engine, then you will run out of flow before you ever get to that pressure ratio. thus you are flow limited. if the turbo is correctly sized, the bigger engine will make more power. remember, turbo around combo, not the other way round.