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Old 09-11-2021, 04:36 PM   #1
speedgod^s13
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Precision 6262 or G-Series

A little background on my build. I bought my 6262 shortly after they were released, and got the billet dual ball bearing .82 a/r version, with the anti-surge housing. Obviously, turbos have come a long way since then, and the G-series have really caught my attention, so I'm undecided on what I should do. My goals are to have great boost response, and getting the most power I can, off of 91 pump gas. Sadly, we don't have any E85 stations here, so unless I buy it @ $10 a gallon, that isn't an option. We do have a few stations that sell 100 octane, but it's right around the cost of the E85, but easier to find. SR is pretty much built from top to bottom, except for the valves, running HKS 272 step 2 cams. So, my options are to run my 6262 as is, or to get a small a/r turbine housing, which should decrease the spool time, while sacrificing the top end a bit, right? Or, sell my 6262, and pick up a G-series, but which? I'm torn between the G25 or G30, and the pros and cons of each, so here I am. Appreciate any input or personal experiences you may have had.
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Old 09-11-2021, 04:38 PM   #2
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Have you considered Borg Warner EFR
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Old 09-11-2021, 04:39 PM   #3
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91 octane fuel calls for a stock engine w/ JWT S3 cam and a 380rwhp max turbo.

Your setup is wrong for the fuel. I would fix that first. If you want to use a built engine and HKS 272 cams you would want alcohol fuel and 550rwhp target setting. No point in having a 550rwhp capable engine when you can only support 400~ or less which is stock engine territory on 91 or 93 gasoline.

The ideal turbo for non-nitrous and non-drag racing application for 91 octane gasoline is approx 42 to 48lb/min flow rate at 2L displacement.

272 is a large cam and it will bleed low rpm cylinder pressure which causes lost torque at low rpm. Thus a 272 cam is best served with 5000-8500rpm rpm range which is typical for drag racing but not so useful in a street car or any vehicle where shift points are inconsistently set (manual transmission + random streets). In other words, a turbo which can spool early say 4000rpm or even 3500rpm is less useful due to the large cam and the engine would be better served with a much smaller cam if spool is a priority (response and drivability for non-drag racing applications)
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Old 09-11-2021, 05:06 PM   #4
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Quote:
Originally Posted by Kingtal0n View Post
91 octane fuel calls for a stock engine w/ JWT S3 cam and a 380rwhp max turbo.

Your setup is wrong for the fuel. I would fix that first. If you want to use a built engine and HKS 272 cams you would want alcohol fuel and 550rwhp target setting. No point in having a 550rwhp capable engine when you can only support 400~ or less which is stock engine territory on 91 or 93 gasoline.

The ideal turbo for non-nitrous and non-drag racing application for 91 octane gasoline is approx 42 to 48lb/min flow rate at 2L displacement.

272 is a large cam and it will bleed low rpm cylinder pressure which causes lost torque at low rpm. Thus a 272 cam is best served with 5000-8500rpm rpm range which is typical for drag racing but not so useful in a street car or any vehicle where shift points are inconsistently set (manual transmission + random streets). In other words, a turbo which can spool early say 4000rpm or even 3500rpm is less useful due to the large cam and the engine would be better served with a much smaller cam if spool is a priority (response and drivability for non-drag racing applications)
Thanks, I also forgot to mention that I will be running a meth injection kit. I also have an HKS 264 intake cam that is brand new in the box, that I could install.
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Old 09-11-2021, 05:14 PM   #5
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meth injection over gasoline can bridge the gap to alcohol and allows 450-500rwhp minimum (25-35psi boost ranges)

However the pump is a wear item and will eventually quit, often causing engine failure. This is a known and guaranteed outcome unless routine maintenance is performed (warning).

To answer your question fully about which turbo what, you would look at the compressor map and choose a turbo which can supply approx 52-58lb/min airflow (450-500rwhp) minimum

Example, meth injected sr @ 450rwhp using one of those newer style gtx turbos approx 25psi of boost



With the small turbine selection, input boost pressure has to be much higher. For example there are many large turbine, old school turbos which can provide 500rwhp with less than 25psi of boost but they spool much slower. Thus the idea behind many new technology turbo seems they can use a small turbine and high boost pressure to gain both fast spool and high peak power output. This wasn't possible on old-school turbos because high pressure ratio at flow rates near 50lb/min and higher required larger or heavier compressor wheels and exhaust wheels. As new material science and engineering were applied the turbo designers figure out how to flow high mass rates and support high pressure ratios with better seal leakage and fewer parts imbalance, lighter parts, superior surface finish and understanding of 3D stress tensor applied mechanical principles for resisting stress and developing a yield expectation and parts application, etc... it may have only improved adiabatic efficiency a percent or two but overall the reliability and seal quality improved dramatically making them more tolerable of high pressure ratio used in a daily application. It is really an overhaul of small properties throughout the turbo which makes them more reliable as years progress and we have come to the point where a modern turbo sitting at 40psi isn't an issue anymore, with everything so tight and reliable these days coming together. And because intake manifold pressure in PSI has no bearing on performance or danger, consider that combustion pressure can be 1000psi. In comparison 50psi is really negligible in the scope of what combustion entails. Intake pressure being 15psi or 50psi makes no difference unless the intake is made of plastic or something like that it might explode the intake into pieces. So there are times when maintaining a lower boost pressure may be more ideal or necessary- even if just to minimize the potential for leaks, but, we should not let it hold us back from making whatever power is available. Older turbos generally do not so well at high pressure ratios unless they have big heavy compressor wheels which spooled more slowly. We just have to be careful about what we are calling efficiency. The main one we are concerned with is the adiabatic efficiency of compressor wheel and pump profile which is fairly hard limited by nature. In other words no matter who makes a turbo or how far technology comes there will never be a more efficient adiabatic compression rate than say 77% or less. Because of a hard limit in nature which prevents from surpassing 79%+ due to rules about friction when compressing air molecules closer together rapidly you can mathematically assure that some temperature raise of compressor outlet will always occur and this will further increase pressure above what it would have been creating additional hydraulic gradeline energy potential or pump head as related in PV=nrT equation. To put it another way, high pressure is good because it is energy in the form of pressure instead of velocity, its like opening a section of pipe up wider. Since the plumbing volume is constant we can relate pressure directly to temperature P = T and anytime a temperature raise occurs we can see that pressure must also increase. But pressure has no direction, the pressure as in a tire as measured is a scalar unit and contains no vector information. This is because to exert some pressure the air molecules must collide continuously, elastically with some surface in all random directions for which a statistical distribution results with the pressure noted on a gauge. So where then does the direction come from? In a tire there is no direction, no flow. But in a turbo obviously there is some flow rate and some direction of flow and this is known as velocity gradeline energy potential and it is a measurable quantity

Besides the hydraulic (pressure) gradeline energy potential, there is the velocity gradeline energy potential where energy is stored in the form of velocity. It can be transferred back and forth from velocity to pressure by changing the diameter of a pipe through which there is some fluid flow. For example a narrow section causes a drop in pressure and increase in velocity. The velocity gradeline grows and the hydraulic gradeline diminishes in a narrowing section of pipe and the pressure can even drop below the boiling/vapor (the liquid boils at low pressure) point of the liquid and cause cavitation and bubbles to form.

To evaluate turbo fluids we must keep track of kinetic energy & momentum (velocity, mass) as well as the pressure, temperature, volume relationships of fluid within each tube, plumbing often contains corners, bends, intercoolers, throttle plates, sections with welds, couplers, intake runners, etc... Any disturbance to some smooth flowing same diameter tube must be considered and is generally a head loss from the pump. Intercoolers cost pump head and that will reduce pump flow so it will also reduce engine power. The turbo flow rate sets the power and flow rate is set by velocity/density which is mass rate. In other words the mass of molecules to pass a certain point per unit time requires a specific velocity at a specific density and constant volume if needed. Thus, an intercooler is a power sponge, because it soaks up the temperature component AND velocity (kinetic energy) by imposing metal material mountain ranges that cost kinetic energy of airflow thus an intercooler creates a pressure drop even if it does not absorb any heat from air passing through some power is going to be lost. A pressure drop is a pump head loss (pump head is just a fancy word for pressure) but when temperature drops, pressure drops and is this still considered a head loss?
Yes. Temperature is energy and energy is energy. haha this is so hard for so many people to see it, but the heat you throw away with an intercooler and the heat you trash by using alcohol fuel is costing efficiency, it is costing extra fuel, the brake specific fuel consumption is getting worse whenever you throw away some heat. The factory goes to great lengths to insulate the engine compartment, they use all kinds of plastics and carpets and shields to reflect and maintain the heat inside the engine bay and inside the power plant. And they run the coolant temps as high as possible- all of this, high temperature and heavily insulated is IMPROVING economy and efficiency. Saving the heat is saving you money in fuel.

Thus, there is a pretty clear line between economy and power in terms of efficiency.
When we want power, we shall trash efficiency, mostly in the name of safety but also partly because some combustion reactions simply react too quickly at high temperature to be useful in a piston engine (fuel behavior is temperature dependent). By switching to a fuel like alcohol or using intercoolers we are throwing away a LOT of heat energy when the alcohol evaporates and this is killing economy but making combustion safer and less likely to spike in pressure and create a hole in the engine. The heat thrown away could have participated in combustion and created a higher pressure on the piston- it would have created more torque in theory, but heat has the unwanted side effect of also speeding up a reaction, not just enhancing it with more pressure. Heat everyone knows is molecular motion but what you might not see is how the jostling rotating energetic behaviors of hot molecules are more likely to find partners and collide with the correct orientations which will speed up the energy release rate from any fuel in a combustion reaction- it may begin to outpace the piston speed and this results with immediate catastrophic failure if it gets far enough ahead just once is all it takes.
Spark timing is the point of initiation but it does not control propagation speed.

Distinguishing pressure as pump head is essential because the pump has a different efficiency of energy to work conversion for each individual pressure value and it does NOT tell us anything about the velocity or kinetic energy component, that is why the pump will have some kind of map to help the consumer understand where flow rate intersects with pump head in an efficient range for their application. Pumps that flow water for myriad systems are designed by fluid engineers (there are people that do this for a living) and they use these pressure and flow rate values to estimate equipment needs accurately, consistently (How large of a pump to buy) so we can do the same exact thing with turbochargers which are also fluid pumps and frequently come with their own map to follow as a guideline but I digress...

I take these basic thermodynamics and make some blatant statements which seem crazy or wrong at first but eventually you will realize are completely true.

"An engine will make the most power with the highest mass of hot as possible air"
This one is absolutely true because the pressure will be highest with some maximum mass and temp. However it could be unsafe and unreliable, as high enough temp would cause problems no matter what fuel is used. Although, with a good enough fuel (such as Alcohol and methanol) the temperature can be quite high IAT 280*F sometimes without issue, and many racers choose not to intercool their Alcohol fueled 2000hp drag racing setups because intercoolers are unwanted energy sponges if the fuel and engine will tolerate the high temperature as I Just finished explaining. The best path from turbo is a straight short tube because it will maximum pump head and flow into the engine. As noted in OEM applications where heavy insulation is used to increase efficiency the same thing can be done for power in terms of insulation and heat retention if the fuel quality is dialed up and engine parts are up to the challenge (forged pistons are much more heat friendly than cast) therefore a mixed crowd of intercool vs non-intercooler 1000-2000hp setups is observed to this day.

For cast piston applications (OEM engines) stock bottom end stuff, temperature is absolutely a killer and should be minimized completely. I want to see ambient air temp going into an engine when tuning. I don't care if its running 40psi of boost the IAT needs to be near 110*F or less to keep combustion safe and reliable at high output. Even though it is killing efficiency and reducing power, we always account for this when choosing a turbocharger in the first place so there is some additional headroom to turn up the unit and get back any lost power. In other words, if you need 49lb/min you would buy a 54lb/min because you know ~5lb/min is going to be lost going through the intercooler and nearby associated plumbing, so called head losses. Doesn't seem like such a big deal but remember the exhaust is going to raise in pressure and temperature because now the compressor has to flow 50hp extra (5lb/min = 50hp) worth of mass flow and at 77% efficiency locked in its more like 7lb/min or 70hp just to make 50, see what I am saying? Now this 70hp isn't actually going into the engine though- its ONLY going into the compressor wheel to make up for the pressure drop of losses in plumbing which means by the end of the plumbing its all been used up and the engine gets none of it. So where does the turbine get the energy from then? That is why exhaust pressure and temp are raising up, the wastegate will demand more from the turbine to hit the new mark 70lb/min higher than would be necessary if there wasn't any intercooler in the way so more exhaust gas will go through the turbine (more mass flow rate through the turbine) at higher temp and pressure.
High EGT is not good for parts. If I could I would flow water through my exhaust tubes to keep them cool but that is just crazy talk and it would kill any fuel economy as discussed. High EGT can melt or warp parts and high EGT can foretell broken pistons and issues with piston ring tension.
You must control the EGT of a performance engine somehow. EGT can be life or death of the engine in a dramatic fashion.

Summary
-keep IAT low, near ambient, regardless of boost pressure used. Do it by any intercooling means necessary.
-Use alcohol fuel when economy isn't needed, it will clean the engine up and tolerate higher pressure and temperature than gasoline
-control EGT by spraying 100% distilled water if necessary (water puts out fires it will reduce EGT)
(methanol is a fuel and burns and does not help reduce the EGT significantly)
-insulate the engine and turbocharger to maintain economy for when using gasoline in daily driver situations

Last edited by Kingtal0n; 09-11-2021 at 08:55 PM..
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Old 09-11-2021, 05:36 PM   #6
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Have a dyno clip for that one also
https://www.youtube.com/watch?v=yu7XteLyuVA

https://www.youtube.com/watch?v=yu7XteLyuVA&fs=1" width="644" height="390">https://www.youtube.com/watch?v=yu7XteLyuVA&fs=1" />https://www.youtube.com/watch?v=yu7XteLyuVA">http://www.youtube.com/watch?v=https://www.youtube.com/watch?v=yu7XteLyuVA

Start posting compressor maps if you want a more in depth analysis of what turbo is going to do what or be good for what
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