4.8 turbo choice.....
Already started...lol.. Only have had the truck 3 weeks...already tinted, lowered, debadged and wheels on the way.
Have the pump and injectors from other project that were not used. Also, already have the 2.25" v-banded 6.0 manifolds.
Need to buy the turbo, wastegate, T4 flange, BOV, a2a, cam & springs. Will have Ralstons or Gray fab up the hot side and I'll run the cold side and mount everything.
And about the turbo....the impeller will be on par for anything the sbe 4.8 can handle. It's the hot side that will make or break the combo. Impeller is only efficent as the hot side allows.
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Have the pump and injectors from other project that were not used. Also, already have the 2.25" v-banded 6.0 manifolds.
Need to buy the turbo, wastegate, T4 flange, BOV, a2a, cam & springs. Will have Ralstons or Gray fab up the hot side and I'll run the cold side and mount everything.
And about the turbo....the impeller will be on par for anything the sbe 4.8 can handle. It's the hot side that will make or break the combo. Impeller is only efficent as the hot side allows.
.
I've had Ralstons do all sorts of oddball projects....just have to be a little patient.
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Imagine you installed an injector to the exhaust system. Spraying it when the engine was hot, would generate a nice loud backfire, a burst of pressure and temperature would blast through the exhaust system at high speed. This is typically considered performance boosting, i.e. you are pushing energy into the exhaust system.
As a down side, you now have this extra explosion for your parts to deal with on that side. Temperatures may get higher than they would normally, gaskets see more fire and pressure than they normally would, and of course the valves have to deal with it as well.
Daily driver (longevity) applications should avoid this extra explosive character, but for racing/performance some folks "need" it.
So let's look at it strictly from a turbine discussion.
What is the correct AR and turbine wheel size for a 4.8 on E only turning 6500rpm (X amount of exhaust gas at X rpm) ??
8.8 SCR
8.2 DCR (roughly)
Events
-4
36
43
-5
Here is an example of exact same turbine sections with different impellers.
- 4" Air Inlet
- 2.5" Compressed Air Outlet
- 72mm Wheel Compressor
- P Trim .96 A/R Turbine
- 102.4mm/72.1mm Compressor Wheel
- 74.1mm/64.6mm Turbine Wheel
- 3" V-band Hot Side
VS
- 4" Air Inlet
- 2.5" Compressed Air Outlet
- 76mm Wheel Compressor
- P Trim .96 A/R Turbine
- 102.4mm/76.7 Compressor Wheel
- 74.1mm/64.6mm
- 3" V-band Hot Side
What does the wisdom say ??
.
What is the correct AR and turbine wheel size for a 4.8 on E only turning 6500rpm (X amount of exhaust gas at X rpm) ??
8.8 SCR
8.2 DCR (roughly)
Events
-4
36
43
-5
Here is an example of exact same turbine sections with different impellers.
- 4" Air Inlet
- 2.5" Compressed Air Outlet
- 72mm Wheel Compressor
- P Trim .96 A/R Turbine
- 102.4mm/72.1mm Compressor Wheel
- 74.1mm/64.6mm Turbine Wheel
- 3" V-band Hot Side
VS
- 4" Air Inlet
- 2.5" Compressed Air Outlet
- 76mm Wheel Compressor
- P Trim .96 A/R Turbine
- 102.4mm/76.7 Compressor Wheel
- 74.1mm/64.6mm
- 3" V-band Hot Side
What does the wisdom say ??
.
Last edited by LSOHOLIC; Apr 24, 2016 at 01:01 AM.
Is that a stock48 cam?
I don't know anything about how the 4.8s do turbine and cam wise. But 5.3-6.0 and 75/75 combos can go 5s at a decent weight. Those turbos "on3" are so cheap just try one and if it don't work get a turbonetics hurricane series "68 turbine" or anything a on3, turbonetics or prescion 75 turbine wheels.
The 68mm wheels seem to sputter out at 5500 rpm with the bigger motors so a 65-68 turbine may be perfect with the small cam and stroke.
I don't know anything about how the 4.8s do turbine and cam wise. But 5.3-6.0 and 75/75 combos can go 5s at a decent weight. Those turbos "on3" are so cheap just try one and if it don't work get a turbonetics hurricane series "68 turbine" or anything a on3, turbonetics or prescion 75 turbine wheels.
The 68mm wheels seem to sputter out at 5500 rpm with the bigger motors so a 65-68 turbine may be perfect with the small cam and stroke.
the design of the exhaust system will have a large impact on which turbo will work best. So will the converter/clutch, weight of the wheels/tires/driveshaft/flywheel, the type of fuel quality 93/E85( and spraying meth or not), whether using nitrous or not, weight of the vehicle, types of temp control you are using (blankets, shields, reflections, coatings) the big list is big
If you are using junk turbos then forget about calculations. Junk is junk, just try it, it will probably only last a few weeks then you get to try another one
If you are using junk turbos then forget about calculations. Junk is junk, just try it, it will probably only last a few weeks then you get to try another one
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Verdad Gallardo Is that a stock48 cam?
I don't know anything about how the 4.8s do turbine and cam wise. But 5.3-6.0 and 75/75 combos can go 5s at a decent weight. Those turbos "on3" are so cheap just try one and if it don't work get a turbonetics hurricane series "68 turbine" or anything a on3, turbonetics or prescion 75 turbine wheels.
The 68mm wheels seem to sputter out at 5500 rpm with the bigger motors so a 65-68 turbine may be perfect with the small cam and stroke.
I don't know anything about how the 4.8s do turbine and cam wise. But 5.3-6.0 and 75/75 combos can go 5s at a decent weight. Those turbos "on3" are so cheap just try one and if it don't work get a turbonetics hurricane series "68 turbine" or anything a on3, turbonetics or prescion 75 turbine wheels.
The 68mm wheels seem to sputter out at 5500 rpm with the bigger motors so a 65-68 turbine may be perfect with the small cam and stroke.
212/218 112+2
212* @ 0.050 and a 36* IVC is plenty for 293" cubes @ 6500rpm.
Jarrett will spec you what ever you want. Don't think he has "a cam". He made the Isky triple 12 popular with the results from his builds but....it's whatever the combo wants IMO.
With this combo.....it's a balancing act. Don't want to load the motor to early in the rpm (mechanically limited) and don't want to spin it to high (for many reasons).
So, in saying all of that.....70mm or 72 or 76...etc. They all will feed the 293" cube motor all it wants. It's matching the exhaust characteristics that will allow the impeller to do its job efficiently.
.
Last edited by LSOHOLIC; Apr 24, 2016 at 02:13 PM.
the design of the exhaust system will have a large impact on which turbo will work best. So will the converter/clutch, weight of the wheels/tires/driveshaft/flywheel, the type of fuel quality 93/E85( and spraying meth or not), whether using nitrous or not, weight of the vehicle, types of temp control you are using (blankets, shields, reflections, coatings) the big list is big
If you are using junk turbos then forget about calculations. Junk is junk, just try it, it will probably only last a few weeks then you get to try another one
If you are using junk turbos then forget about calculations. Junk is junk, just try it, it will probably only last a few weeks then you get to try another one
The "cheap" turbos have proven themselves time and time again. A well designed oil feed and drain back as well as possibly a turbo timer should go a long way as far a dependably and durability are concerned.
But....I appreciate all the detailed talk but I'm really only seeking input for a properly sized AR and turbine wheel for a 4.8 with the details I've previously stated. I have a very strong handle on the rest of the project.
Thanks...
.
Last edited by LSOHOLIC; Apr 24, 2016 at 02:47 PM.
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From: Ohio
I'm OCD when it comes to attention to detail. So yes....I will obsess with all the little things (number of bends, bend radius, thermal efficiency, a2a shrouding, priority wastegate location, large down pipe, minimizing all restrictions especially pre-turbo...etc).
The "cheap" turbos have proven themselves time and time again. A well designed oil feed and drain back as well as possibly a turbo timer should go a long way as far a dependably and durability are concerned.
But....I appreciate all the detailed talk but I'm really only seeking input for a properly sized AR and turbine wheel for a 4.8 with the details I've previously stated. I have a very strong handle on the rest of the project.
Thanks...
.
The "cheap" turbos have proven themselves time and time again. A well designed oil feed and drain back as well as possibly a turbo timer should go a long way as far a dependably and durability are concerned.
But....I appreciate all the detailed talk but I'm really only seeking input for a properly sized AR and turbine wheel for a 4.8 with the details I've previously stated. I have a very strong handle on the rest of the project.
Thanks...
.
Jarrett's triple 12 cam and the On3 7665 are a solid combo for a 4.8. Lots of low-mid range, and extremely fast spool. If you want more power, spend a few extra bucks for the On3 7875. You'll trade a little low end for top end, and still have tons of mid-range power.
Typically, nobody listens to him anyway.
Jarrett's triple 12 cam and the On3 7665 are a solid combo for a 4.8. Lots of low-mid range, and extremely fast spool. If you want more power, spend a few extra bucks for the On3 7875. You'll trade a little low end for top end, and still have tons of mid-range power.
Jarrett's triple 12 cam and the On3 7665 are a solid combo for a 4.8. Lots of low-mid range, and extremely fast spool. If you want more power, spend a few extra bucks for the On3 7875. You'll trade a little low end for top end, and still have tons of mid-range power.
Thanks for the turbo recommendations....
Not to derail my own thread.....but looking at the trans situation, dollar for dollar....I'm considering just doing a 80E swap vs dumping $$ into a limited life 60E.
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I'm basing my judgement on the few turbo builds (rock crawler/ TEO4H) I did, which were not performance based. And N/A, n2o stuff that I currently tinker with.....
More duration and an earlier evo "should" help...
The blow down cycle, pumping losses and...what I've seen is, as compression becomes higher the peak cylinder pressure tends to drop off more quickly. So there is no need to hold the valve closed longer, it only hurts the other cycles. And IMO, this is how you start increasing your VE & BSFC ( by helping other cycles, it's all about managing compromises)
So....8.8 scr & 8.2 dcr...with 15 to 20 psi on top = effective compression ratio. Gunna guess and say with my local elevation and average d/a that the effective compression is in the high teens or low twenties.
I would not be surprised to see the cylinder pressure completely fallen away 25* ATDC
Also....I can find several quote's from Urban & Duttweiler stating early evo reduces back pressure and helps with spooling (two guys who know their craft).
.
More duration and an earlier evo "should" help...
The blow down cycle, pumping losses and...what I've seen is, as compression becomes higher the peak cylinder pressure tends to drop off more quickly. So there is no need to hold the valve closed longer, it only hurts the other cycles. And IMO, this is how you start increasing your VE & BSFC ( by helping other cycles, it's all about managing compromises)
So....8.8 scr & 8.2 dcr...with 15 to 20 psi on top = effective compression ratio. Gunna guess and say with my local elevation and average d/a that the effective compression is in the high teens or low twenties.
I would not be surprised to see the cylinder pressure completely fallen away 25* ATDC
Also....I can find several quote's from Urban & Duttweiler stating early evo reduces back pressure and helps with spooling (two guys who know their craft).
.
Last edited by LSOHOLIC; Apr 25, 2016 at 03:05 PM.
What's your guys thoughts on a T4 1.10 AR with the 212/218 112+2, 4500lb truck and a 3000-is convertor ??
My initial thoughts are....the convertor better be perfect...lol.
Probably run very well once in boost but.....that 4.8 will be hating life trying to get up on the convertor (to bad it's a 99% street deal, dump valve would shine in a situation like this).
Because if I don't go cheap on the turbo.....I'm leaning towards a cast 475 (t4, 1.10, 83 wheel).
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My initial thoughts are....the convertor better be perfect...lol.
Probably run very well once in boost but.....that 4.8 will be hating life trying to get up on the convertor (to bad it's a 99% street deal, dump valve would shine in a situation like this).
Because if I don't go cheap on the turbo.....I'm leaning towards a cast 475 (t4, 1.10, 83 wheel).
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Last edited by LSOHOLIC; Apr 26, 2016 at 09:37 AM.