HOW TO: PICK THE RIGHT TURBO!

okay guys let's talk too much today we're going to take a look at a test between two very popular Turtles we've got a BorgWarner s4 75 and a BorgWarner s4 8 the reality is this video is less about the comparison between those two turbos than it is about picking the right turbo for your application we're going to show you the big things you should worry about and the little things you shouldn't in this video we ran a comparison between two very popular turbos we started off with a BorgWarner s4 75 and then followed that up with a BorgWarner s4 8 here's what the comments will get going these two were not the same configuration as a matter of fact they were dramatically different even more so I didn't run them at the same boost level and here's why first of all if you take two turbos that are sized to run in the power output that we tested in this case between 850 and 900 horsepower if both of those turbos will support that power level if we run them both at the same boost air/fuel timing and temperature guess what's going to happen they're gonna make the same power the only change will be a difference in hot side like we saw here if one turbo has a higher back pressure than the other there could be a difference in power otherwise the power output would be the same and if it's not the same if there is a difference in the wheels it's gonna be like this much and the problem is I don't want to do a test that shows this much of a different now I know that there are class guys out there using a specific turbo I can only run a 76 millimeter and they're trying to get the most power out of that combination that they can and that's great I love that kind of testing for them but for the five or ten guys that are actually doing that doing a test it's going to give information for five or ten guys isn't a great video I want to provide information for five or ten thousand guys that can really use that information and that's why I ran this test so when we ran the test I use a manual wastegate controller and I ran the tests I ran it at 10 pounds or so with a s 475 left the control are the same and then ran the S 480 to find out what what as it turned out the booze pressure was higher on the s 480 and for good reason it's a function of back pressure but that's a good test it shows when we changed the turbo a change happened it also shows that the S 480 could support more power than the s 475 which we already know but more than that it shows the importance of choosing the right turbo for your application and that's what this video is all about we're gonna talk about the big stuff that really has a big effect we'll work our way down to the little stuff like like a billet wheel versus a cast wheel or a divided housing versus a non divided housing or equal length runners versus non equal lengths all the stuff that makes this much difference is not as important as the stuff that makes this much different so let's get started with the stuff that makes this much difference before we get to the results of our tests we need to understand something very important how to choose the right turbo for our application when you're choosing the right turbo the first thing you need to think about is how much power do I want to make look think we use an example here let's take a thousand horsepower turbo like rs4 75 rs4 80s 78-75 that's kind of the normal go-to thing for most v8 LS applications there are smaller ones there are bigger ones we use that as an example so if we take our thousand horsepower s for 75 s for eighty seventy eight seventy five and apply it to eight let's say a cam 5.30 let's say our cam 5.3 liter makes 450 horsepower so if we apply 14.7 pounds of boost from our thousand horsepower turbo to our 450 horsepower 5.3 liter guess what happens we applied one atmosphere in addition to the atmosphere that's already there basically we're gonna double the power up fourteen point seven pounds on a 450 horsepower motor we get 900 horsepower that assumes a couple of things are right you have to have the right amount of cooling with an intercooler you have to have the right octane you have to have the right timing air fuel but it's a pretty good gauge sometimes it's a little more sometimes it's a little less but it gives you a good idea so 14.7 pounds of boost from our turbo on a 450 horsepower motor gets us 900 horsepower now that equates to rider 30 horsepower per pound of boost so we know the turbo will do that here's why the turbo won't always supply 30 horsepower per pound of boost let's say we take that same turbo our thousand horsepower turbo apply the same amount of boost 14.7 pounds but we supply it to a stock 4.8 liter that makes 300 horsepower will it supply 30 horsepower per pound of boost now no it won't not because I can't we already know it can because it did on the 450 horsepower motor but if we supply 14.7 pounds of boost from our turbo to a 300 horsepower motor we get 600 horsepower which equates to about 20 horsepower per pound aloose now is it because the turbo can't do it because it's not efficient it doesn't have the right wheel it doesn't have the magic billet wheel or the stage 7 turbine housing no the turbo can do that but what dictates how much power that turbo supplies per pound a boost is a function of the flow rate of the turbo obviously but more importantly it's the function of the power output of the naturally aspirated motor that you're applying it to if we take it to an extreme we've got our thousand horsepower turbo and we put it on a 100 horsepower 1 liter motor it's going to make 200 horsepower at 14.7 pounds of boost and then each pound of boost is gonna be worth what's that six or seven horsepower and that's how it works as long as the flow rate of the turbo can support that power output you add 14.7 pounds of boost you double the power output of the NA power and it works at any boost and any power levels as long as a turbo can support them so now that we've taken a look at that let's figure out what we need to do now if you've got a combination if you've got the power output you want if you got the turbo now it's time to choose the hot side ok we've taken a look at the big picture stuff you've got an engine you want to add whose to it and make more power you've chosen the size of your turbo based on the required power output now it's time to look at the smaller stuff we're gonna look in detail now at the hot side of the turbo we've got the cold side that's the power output now we need to look at the hot side so if we have our thousand horsepower turbo and we use that thousand horsepower turbo on let's say a 4.8 liter and a sleep okay that combination on a 6-litre if we have the same size hot side is it going to produce more back pressure on the six liter than it is on the 4.8 liter and the reason for that is the sixth leader is going to make more power at than the 4.8 especially down low it's going to have more torque more response more exhaust though so more exhaust flow more back pressure that's why we would size the turbo differently on the hot side for a 6 liter than we would on a 4.8 liter so let's say we want to make a thousand horsepower with each one of those combinations on a 4.8 liter not going to be that hard the back pressure is going to be low on our thousand horsepower turbo but on a 6 liter we're going to have to deal with back pressure and the way that we get around that is put a larger hot side on that same turbo to try to get it to make a thousand horsepower on the bigger motor so remember bigger motor more power bigger hot side smaller motor smaller hot side easy-to-remember they go together now let's take a look at the results of the comparison between our s 475 and our s 4 8 [Music] the comparison between the s 475 and the s 480 turbos were run on our six litre test motor this is the same as the BIGBANG combination that we ran for that made fifteen hundred and forty horsepower it was a six litre ly6 with ring gap had Trick Flow 225 heads on it and Brian to a racing stage three turbo cam and a doorman ls6 intake manifold our turbo kit consisted of truck manifolds feeding a custom white pipe with two turbo smart waste gates we had pro charger air to water inner core and then we ran both the turbos now we ran these on a combination of 91 and race gas so we could put timing in this thing and try to maximize the power output we ran first the s 475 and this is run at a peak boost of about eleven and a half pounds I'll show you the boost curves on both of these so run this power level on the S 475 at this boost level it made 879 horsepower and 803 foot-pounds of torque and we were controlling we had seven pound springs in our turbo smart wastegates and we were controlling the boost with a manual wastegate control or bleed valve so now let's take a look and see what happens all we did was replace the s 475 with the larger s 480 and I'll go ahead and put the specs for both turbos up here so you guys can see what the difference is between the two so as we can see and maybe kind of this is what we would expect the in red here the s 480 was less responsive down low and part of that obviously it had a bigger hot side the s4 75 was actually designed to be run as part of a twin setup that we ran on that BIGBANG motor and had run on other twin combinations so it had tighter hot sides for that because it was designed as a twin so it we wanted to be a little bit more responsive and the S variety was more designed as a single so this s 480 had was less responsive down low but really came on at the top so run with the s 480 and our manual wastegate controller set the same as it was for the s 475 the s 480 produced 977 horsepower although P torque was very comparable at 807 foot-pounds of torque it basically just shifted the curve now let's take a look and see why why these things produce the power curve that they did obviously it's a function of boost let's check that out in our comparison between the s horse 75 and the s 480 turbo on our six liter test motor if we take a look at the difference on the power curve obviously there was a reason for that and the best way to take a look at that is take a look at the boost curve now this is the boost curve of our s for 75 turbo start that out down here below nine pounds at around 3,600 rpm and rose up to around 11 and then you know was kind of hovering in the eleven and between eleven and eleven half range and that was with our we were adjusting that with our manual wastegate controller so here's what happened after we left the wastegate controller in the same position basically the same bleed rate and here's what happened after we installed the S 480 turbo so as as you might expect after looking at the bet the power curve the s 480 here in red the boost response was less down low it was a bigger turbine housing in a bigger AR so it made less boost down low down around seven pounds here at thirty five hundred and thirty six hundred but made more boost at the top it was twelve point nine PSI whereas the s 475 was closer to 11 for 11 three he's a crossover point here was about fifty nine hundred rpm so bigger turbo bigger hot side especially so this thing was less responsive and ultimately could make more boosts and more power now a lot of that is the function of what's happening with the wastegate because the how the waste gate opens is a function of the back pressure versus the boost pressure so if we have less back pressure from the bigger turbo then we have a change in opening of the waste gate so basically a lot of things are happening here but we know that the s 480 is definitely capable of making more power and more boost in the 475 now we could go up in boost from the s 475 but as we'll see when we take a look at the back pressure curve there is definitely going to be an increase in back pressure to go along with that increase in boost pressure let's check out the back pressure curve if we take a look at a comparison between the back pressure curves produced by the two turbos in our tests this is the s 475 and this is the s 480 so as you can see the s 475 in blue had more back pressure through the whole curve you know by a couple of pounds six eight point six to two point five two point six pounds so it started higher and ended higher because of the smaller turbine side on that so if we take a look at see here's a good comparison so obviously smaller turbo more back pressure kind of standard so now let's take a look and see let's see the boost pressure versus the back pressure here so this is the back pressure on the S 475 and here's the boost pressure versus the back pressure so you can see even down low even starting at 36 or 37 hundred rpm the S 475 was making more back pressure than it was loose pressure so that tells you that it's going to be fairly responsive and that the back pressure is probably going to be very high now let's take a look and see what happens well let's swap this out to the S 480 and as you can see similar thing on the S 480 although the crossover was much higher than the 3500 rpm range it didn't happen till out at 4200 rpm range so the s 480 had less back pressure than boost pressure down low they crossed over and then it had more back pressure than moose pressure so at twelve point nine pounds it had 20 pounds of back pressure and on the s4 75 we had eleven point four pounds of lose pressure and twenty three and a half pounds of back pressure so kind of more than a two-to-one back pressure to lose pressure relationship on the s4 seventy five so we're getting up to the point with that s 475 that we're starting to worry about back back pressure on this combination so this size hot side on on using an S 475 on a sixth year probably not a good idea that's why our discussion and comparing it between a 6 liter and a 4.8 liter shows that you need to size the back you need to size the hot side of the turbo appropriately for the power output and the size of your testimony let's get to our conclusion guys okay guys what'd you think about the test our comparison between the s 475 and the s 480 there we'd totally blow up by not running them at the same boost level let me know in the comments but here's my take if you have a turbo let's say a thousand horsepower turbo like either one of these and you're running it at 700 horsepower and you want more power upgrading the turbo to a more super efficient billet compressor wheel or stage 27 exhaust wheel isn't really gonna do much where a turbo upgrade really comes into play it's like this s 475 vs. the S 480 test if you have a victor bold that will support more power that's where it's going to be beneficial we know an S 480 will make more power than an S 475 it flows more air it will make more power that's where it should be run does that make the S 480 a better turbo than the S 475 no in fact if we ran it down at 6 or 700 horsepower the opposite would be true the S 475 would probably be a better choice it's more responsive it's in its efficiency range and it's going to work much better so it's very important to choose the turbo for what you want to do if you have a 4.8 and you want to make a thousand horsepower with an S 480 and you're running from 8 5,000 to 8,000 rpm that might be a good choice on the other hand if you're choosing a turbo for a 4.8 liter that's in your pick up that you're using for towing you're going to want more response so you've got to choose 2 turbo according to the power output and the intended usage I'm richer holder guys thanks for watching make sure to comment let me know what you think I'll keep testing

Channel: Richard Holdener

Views: 71,663

Keywords: turbo, boost, s475, s480, intercooler, dyno, tune, borg warner, psi

Id: nOU9uqWuYQg

Length: 17min 0sec (1020 seconds)

Published: Wed May 20 2020