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So, I'm doing research for a centrifugal SC, to do a more or less custom setup. I believe this is the right choice for my preferences and compromises. My intention is to charge at around 8PSI and get whatever power I can at that pressure. Liquid IC, possible oil cooler for SC, and more or less whatever is needed of supporting mods to improve reliability and power at modest pressure.
I've been around and done a fair amount of research, but any constructive input is highly welcome.
Vortech states their excellence, Procharger claims that Vortech is not. I guess both brands are usable, but Vortechs smallest SC, V-5, looks larger than needed(got map on email, asked to publish, but did not get a clear yes), with a max flow of approx. 65lb/min, and a minimum approx. 5lb/min. DNA Motorsports delivers with a large Procharger, and seems to have quite limited low end. They stated that the smaller SC had reliability issues, I do not know the reason at current time.
But when looking at the Highest horsepower thread, I noticed that Knightsports looked to have a well performing setup for the 4 port. Looks like they are using a Rotrex C30-94. Flow chart for this indicates that it can support a good top end. Does anyone disagree?
You have to subtract the power required to drive it, which us a bigger number than most people realize and has a big impact on a small engine's output. So the flow chart is only one chapter of a more comprehensive story. Also, since it's rpm is directly related to engine rpm then an engine with a wide rpm range can usually only optimize it in part of that range. Bottom line, the power you make at 8 psig is probably the same stress engine load a turbo makes at 12 psig with much less power at the wheels overall. Using serpentine or v-belt is also not optimal on an engine with only two main shaft bearings. Not knocking your choice, just making sure you undrstand the realities of going that route.
Thanks for the input. I was doing some estimates using this, http://www.scubaengineer.com/program...calculator.xls, 45lb/min is around 18000liter/min. At 1,55Bar and 50% efficiency(efficiency drops closer to the edge of chart), it requires 38hp of drive power. Say 40Hp with some more losses. 240Hp x 1,55 = 372FWHp. 372-40Hp = 332FWHp. So I was hoping for close to 300RWHp. Does this sound plausible?
Some points that is important to me:
- A SC is easier to take away if I get in problems with the "government"
- A SC is less complex. Just like my brain and mech skills(will have assistance)
- A SC has better throttle response.
- I do not like the sound from a screw compressor, makes it less stealth, see first point
You make some valid points, but as said above, the SC route doesn't have the best track record around here (literally and figuratively).
I would do some more research on a turbo kit and it may surprise you that it really isn't any more complicated of an install than a SC would be. One of the big reasons I say this is that, yeah getting at the manifold and squeezing a turbo in there is a pain the anus (for low mount); but other than that you don't necessarily "need" to screw around with any other major areas of your engine. The reason I say this is that if you go with a low mount set up and an upgraded (from the GReddy) turbo than there is no requirement to pull apart your UIM; which is typically where I notice a lot of people having issues (boost leaks, etc). Even on the stock GReddy, if you were to go that route it is not a necessity to install the blocking plate meaning you never have to remove your UIM. Not only that but you have tremendous amounts of resources from this forum alone if and when you run into any issues.
Anyways, just food for thought.... I'm obviously quite biased when comparing the two
if you want throttle response I'd highly recommend a BorgWarner EFR 7163 turbo.
Pardon for the ignorance, but why? To me, it does not look like compressor has slightly less than desirable capacity at low pressures? Am I looking at the wrong map? Or are you thinking that this would be operating at 12-14PSI range maybe?
Another thing that is (absolutely)not my field of expertise is what criterias do need to be fulfilled to make it fit into a greddy/low mount setup?
I would do some more research on a turbo kit and it may surprise you that it really isn't any more complicated of an install than a SC would be.
Thanks, I have not thought of it this way, but absolutely a valid argument. Even if I have been keeping close attention to this part of forum for several(5!) years, my detail knowledge is obvious not good enough. Maybe I have focused too much at the engineering/understanding part. My blessing and curse in many ways.
Pardon for the ignorance, but why? To me, it does not look like compressor has slightly less than desirable capacity at low pressures? Am I looking at the wrong map? Or are you thinking that this would be operating at 12-14PSI range maybe?
Another thing that is (absolutely)not my field of expertise is what criterias do need to be fulfilled to make it fit into a greddy/low mount setup?
It would be an absolute nightmare to fit that B/W turbo in a low mount setup ........ just too long and too much junk hanging off it . Plus it's the same flow as a stock greddy which we know is only good to around 250whp.
I've tuned a number of Sc'd RX8s . Sure throttle response is instant and you can make a reasonable amount of top end . But there is so much more fun to be had with a well set up turbo system . There is just no comparison IMO.
It's rated up into the high 500 hp range on a piston engine, it will damn sure out spool a Greddy low and high.
ps, the 1980's called and said they want their lil' POS turbo back
Alex Maximov - Cornfed Racing Subaru WRX STi
Red line = EFR7163 0.85 a/r, tuned on E85 by Moore Automotive
Green line = Stock turbo, Methanol Injection
2L Piston engine Tuned on E85 .... apples and oranges team ?
Now lets get real shall we ?
Ok it does better than a stock Greddy but check the flow chart below . It's actually between a Greddy and an upgraded greddy (To4e 57 or 20g ) up to about 14psi . Those turbos , as we know, will run to about 290-300whp happily. The 7163 obviously does way better as boost gets higher , but at that point it's already a hair drier trying to keep up with a Renesis. Trying to guess how much power it might make is actually quite hard , because it keeps making more when the others are done with , but it's not hard to see that it's going to be making a lot of hot air which is the last thing we want on a high compression rotary.
Not to put too fine a point on it - it's a great choice for a 2L 4cyl but a shitty one for a Renesis running at pretty much any boost level ........... unless you want to block off the Aux ports like the greddy guys do , or maybe limit rpm to about 6000 ?
Get real? You mean like attributing turbo selection and placement on me when I made no such comment. There are several BW EFR turbos that can play into the generic reference. The topic is a centrifugal SC and I think the OP is mistaken in thinking that a bunch of generic centfifugal SC marketing BS is instead factual.
There's more to the hair dryer than you think, but it was my mistake to let myself be baited in the first place. I agree to disagree.
Get real? You mean like attributing turbo selection and placement on me when I made no such comment. .
Originally Posted by TeamRX8
if you want throttle response I'd highly recommend a BorgWarner EFR 7163 turbo.
This is an Rx8 forum............. last time I looked
Re the placement .............. I just made a bad assumption . I mean , if you were going to go to the trouble of fitting a top mount turbo you would have to have rocks in your head to then go and fit one that was too small .
The flow numbers you are using for those pressure ratios seem high by at least 10%. Unless you are assuming a heavily ported engine. We are more likely to top out around 50lbm/min and at a pressure ratio of 2 at the engine inlet not turbo outlet. Turbo outlet pressure will be higher with IC and piping losses which will be significant at 50lbm/min.
The flow numbers you are using for those pressure ratios seem high by at least 10%. Unless you are assuming a heavily ported engine. We are more likely to top out around 50lbm/min and at a pressure ratio of 2 at the engine inlet not turbo outlet. Turbo outlet pressure will be higher with IC and piping losses which will be significant at 50lbm/min.
Those were as measured numbers consistent with a number of Renesis . The numbers are about right for a setup running a compressor large enough to support that flow without running into choke and the boost was measured at the turbo , not the throttle.
If you had an undersized turbo ( like all of those shown above) ,yes ,the numbers would be less .
my bad memory about specifically calling out the 7163 then so you/I got me ... completely an honest mistake so please accept my apology.
I don't agree with your numbers either, but don't wish to debate it. Everybody will say it won't work, but my basis is real world results from similarly sized turbos where the same was said and dis-proven.
Would I recommend if for a 24 hr endruance or similar track car; no.
Street/autocross/track days properly configured; yes. Certainly over a centrifugal SC setup any day ...
I used to use a pen and paper, now I just use Garrett boost adviser. Garrett Boost Adviser | Turbobygarrett
Put in a 2.6 litre engine, 8000rpm peak power, and 100% very then play around. You won't get 55lbm/min with reasonable numbers at a pressure ratio of 2. Even if you did it the hard way the math still doesn't work out. I'd put a direct link, but my comp is having issues logging in so I'm typing on my phone.
I do believe that people have been reading air flow at around 55lbm/min, but I don't believe the numbers. When you scale a MAF based on assumptions and not facts it's easy to be a bit off especially where the assumptions get wonky. (the top end)
My point is that 50lbm/min should be a optimistic guess for a pressure ratio of 2, and it makes the supercharger the OP suggested a reasonable, but slightly undersized option. The BW turbo mentioned looks pretty darn good compared to other options. Actual performance for the turbo depends on the exhaust housing, and the supercharger depends on the pulley ratio.
You are never going to push 55 lb/min through at 8 psig as the OP requested
Otherwise you're right. I don't understand that a turbo is more than a compressor housing/wheel.
I don't understand that a BW EFR is not a Garrett, Mistubishi, etc.
I don't understand how the IC, exhaust system, etc. all play into the equation.
I don't understand that you don't need 55 lb/min to run a BW EFR 7163 at the HP levels I have recommended it for
In summary, I don't understand or appreciate 1-dimensional turbo theory. I do understand real world results on similar turbos, but recognize this does not compute in 1-D world ..
Again, I fully admit that traditional thinking says not to do it, we don't live in the stone age or follow their traditional way of thinking any more ...
I used to use a pen and paper, now I just use Garrett boost adviser. Garrett Boost Adviser | Turbobygarrett
Put in a 2.6 litre engine, 8000rpm peak power, and 100% very then play around. You won't get 55lbm/min with reasonable numbers at a pressure ratio of 2. .
I had a bit of a play with the calculator and i see where you are coming from . But the numbers don't match real life even in the lower hp ranges.... Something aint right .
Tried to take it down to basics, that can be fun(Well, sometimes not) I'm assuming 100% Volumetric efficiency and 9000RPM flywheel speed for easy math.
1. We have 6 chambers of 0.654 liter.
2. At 9000RPM flywheel speed, rotor has 3000RPM
This gives 0.654 x 6 x 3000 = 11772 liter/minute. Weight of air at 40°C is 1.127kg/1000l. This gives 13,28kg of air a minute. This is 29.28lb/min at atmospheric pressure.
At a pressure of 2, you get close to 60lb/min, so the dots marked in the wrongside driving kiwi's post, does not look to be too far off. But I do not have any clue how Ve changes with pressure tough. Since pressure is increased, volume is decreased at the same weight, increasing capacity of air molecules through the pipes/ports before turbulent flows get a restriction. But you are injecting into a chamber with low pressure, and i do not know how the air will behave when it transits through the port, with a high pressure at one side, and low pressure at the other side. Anyone who has done some digging into that area?
Checked you math, not even close to the way I would have done it, but you came out with semi reasonable numbers. The problem is the VE drops at 9000rpm. Otherwise the HP curve would keep going up.
Use 8000 rpm and you get right at 25lbm/min.
But, that doesn't answer the second part of the problem. The intercooler and piping losses. You will lose a couple pounds in the process of getting to the combustion chamber from the turbo. So that will raise the pressure ratio the turbo has to provide from 2 to 2.13 to get a pressure ratio of 2 at the engine. Plus you will also have hotter air going into the engine, so the lbm will go down slightly from the density change.
A turbo can't operate at the flows and pressures we claim they operate at on our engines. You can't get that inefficient without heating up the air, and as you do density goes down and the amount of air the engine can actually consume goes down too.
The reason why people see higher flow rates is that the MAF isn't calibrated against a known standard, it's calibrated against what you expect fueling to be.
03-29-2015, 05:37 PM
but I didn't specify any particular model or location in my earlier reply. 
