I've been running a Gen 4 aluminum 5.3/243 heads with an S475 with typical goodies - Elgin SS2 and PAC1218's. I have a Gen 3 4.8 with the same cam and springs with 706 heads that I've run the same exact hotside/turbo with. I spent the summer chasing a couple of issues, but have been running boost in the 20-22lb range. I've just completed adding a CO2 system with the idea that I should be able to put this thing to 28-35psi on either C16 or E85/98. That was my plan and I thought it ws a good one.

Just fininshed watching a Holdener chat in which he indicated that a 4.8 will be out of turbo before 35psi with an S475 or S480. Which implies that the 5.3 will be out of turbo before that. That is contrary to my thinking presently. I was thinking that the low backpressure build is going to help the top end, but perhaps I'm wrong (don't tell my wife.)


What is the limit of an S475 or S480 on a 4.8/5.3 combo? Am I going to need twins or a much larger single to make an honest 1000-1100whp?

 

A quick look at the batchbot suggests he is right. I didn't go through and get specific with your numbers, but it looks like it will will out of steam before 1000. Plug your numbers in there and see what you get.

 

I battle with Matchbot - and usually lose.

Why is the compressor map in Matchbot different from the map in the catalog. The catalog map works better form me lol.

 

I've wondered about that too, it seems that the map on Matchbot is off for the 80mm. I personally think you could run 30 psi on a 4.8/5.3 with a 475, but na performance mods would need to be kept to a minimum, and you'll want some good charge cooling, and fuel. A 480 would give you a little more room for mods, and some better efficiency. But, none of that matters if you can't keep the heads sealed, and pistons in one piece.

 

So it's not just me lol.

Once track season gets here, I'm going to give the 5.3 a whack into the high 20's. Obviously I'll keep track of the plugs and speed. I'd like to think that I can get it into the 30+ psi range, but I probably won't need it to get where I want to go in terms of times. I think I can make more gains by getting it off the line better than I am now.

Interested in the matchbot thing. It's been a while since I used it, so I have to do some re-reading and re-learning about it.

 

One other thing I noticed about a couple of the maps in matchbot was that the wheel name didn't actually follow the wheel dimensions. Like it would list it as 80×110 which would seem to coincide with inducer/exducer, but the map would be for a 75mm. It didn't seem uniform across many of the wheels so I started to question it.

 

I missed the last sentence in your post earlier (hehe). I've been OK so far at low 20's on either pump E85 (E70 according to my test tube) and C16. I'm pretty careful and never in a hurry, hence it took me about 8 hits before I was able to start doing anything remotely respectable for a 60'. My thought process has been to keep the RPM's in 6600-6900 range until I can get it off the line. I was running the C16 timing at the pump 93 timing +5 degrees. Basically 16-17 degrees over 6000 RPM's on straight C16. From what I've been told that is conservative by at least 6 degrees and maybe 10. But I've been interested in being able to drive it home and not being that guy that oils down the track every weekend. I was able to get two runs with a 1.6_ 60' at 10.2 and 137 and 139 with the conservative big end tune. Both of those runs were my 'booted' runs that were the 2nd run of the day at 2 different tracks.

I wish I had gotten it running earlier in the year, but.........I didn't. I'm thinking that if can see a low 1.5 or high 1.4 60' and put another4-6 psi to be at 25-28psi, then I should be able to see the target of sub 9.5 seconds and drive it home. I just need some seat time and consecutive runs on the same surface - 4-6 maybe in the same day over two weekends. Then I can start trying to break stuff

 

There are just to many variables to say X turbo is good for Y hp.

Look at the total lbs per minute on flow rate between the two. Assuming no race covers etc.. its around 200hp worth of airflow difference. This also assumes you can run them on a great spot on the compressor map. Which is rarely the case. So what the turbo peaks out at on each setup will differ. The smaller motor will usually put it in a happier place, so the 4.8 is a great candidate to lean on.

The issue is over speeding the turbo and/or getting off the efficiency island. This is easily seen by the amount of power made per pound suddenly dropping off.

Basically run the thing as is and bump it a pound at a time. You should continue to see healthy repeatable gains in MPH each bump. If not, it's done. No reason to add more dome pressure/boost.

What is the race weight?

In my experience a mild 5.3 will not continue to make much power past 24-25lbs on an S475. A healthy 5.3 that's actually revving out will run out of turbo even earlier.

Holdners dyno numbers are bunk IMO. Great show, but his dyno numbers are VERY deceiving in terms of actual HP put to the ground once in a chassis and running. He has the masses thinking they are going to make "1000hp" on baby boost. For reference their big $ Nelson built "1500HP" motor in the "F-bomb Camaro" trapped 154. At 3400lbs 1000 whp should trap 154+. So they lost 500hp going from their crank numbers to WHP?

 

3600lbs with me in it give or take 50lbs.

And I agree about adding it in small increments. Also I agree about some of Holdener’s stuff. I’m not keeping the control of intake and coolant temps the way he is with dyno water. I’m running accessories just like everyone else. Engine stand dyno runs are not the same as chassis dyno runs and chassis dyno runs are not the same as a 1/4 mile run. A lot happens in the last 1/8, at least it does for me. I gain 10 degrees of coolant temp in the 1st 1/8 and 20-25 more in the last 1/8th in my less than ideal cooling package. The same for my intake temps with my China $90 A2A cooler. The 1st time I made a full pass my intake temp went from 100ish after the burnout to 205 - fortunately I was on C16. Holdener never sees any of that because he’s running 80 degree water for all of the cooling needs.

I was more shocked at his comment that an S475 would be done well before 30 psi on a 4.8. Seems like it wouldn’t in his dyno cell of ideal conditions, but he acted as if he wouldn’t entertain trying it. How do you know the limit of the turbo if you don’t push it until it stops making more?

Definitely food for thought and thanks

 

You have to look at the range the turbo runs on the compressor map. The LS stuff all runs on the far right/ Closer you get to the center island the better. The compressor and turbine are way too small for that. You'd need something ridiculous like a 98/103 to put you right in the happy place on a 5.3. Or a nice big set of twins. The S475 is just too small. Anything much over 20lbs on a healthy 5.3 and you start losing your gains per lb of boost. IE the turbo is done. It's easily seen on a dyno. Also your back pressure VS boost gets ridiculous. Thats why Holdner never pushes them IMO. He sees this and stops. IMO he stops WAY too soon in most cases.

I continued to make power past 20lbs but I wasn't seeing my usual 30hp per pound gains. By the time I got past 23 I saw almost no gains . By 25 to 26lbs, it didn't go any quicker. By then, back pressure was 2.8:1 and i wasn't going any faster.

 

I have one input left and I presently don’t log back pressure. I probably should use my last input for that just to see what it is.
I’d expect your correct.

Im probably doing a little too much bench racing at the moment. I have oodles of other things to work on before I turn the boost up much beyond 22-24lbs. I really want the motor to live. And trying to cut time at the end of the run is definitely the wrong place for me start.

Do you believe that it was backpressure that stopped you from making more? Or was compressor size? Perhaps a combination of both?

 

I had -21* of overlap @.050 with that cam. Was a 211/230 @122 LSA. I think that's one of the reasons I could push it so far boost wise and keep making power. Hard to say I never ran a small wheel or a T4 turbo again.

Back pressure is good data, my gripe is that it uses up an input and it basically never changes. Once you know what it is, you know! I actually just rigged up a temporary BP setup on my fuel pressure transducer. Logged my BP data, then switched it back once I knew.

IMO the best/cheapest way to keep them alive over 25lbs is to bump the RPM up and put midsize set of twins on them. The next step up over the S400 frame isn't worth the $ IMO. (many of the fancy S400 turbos aren't either) You're talking $2-4k for the GT55 stuff. When you can run a pair of smaller quality turbo for less than half that. The 78/75's as twins are down in the low 7's on a manual trans 5.3 now. They are $500 each. Or $270 each if you buy the ebay units. Pretty hard to argue with that price VS performance. I threw a pair of the ebay $270 units on my latest 5.3 project to play with. I'm curious if the 5.3 will be able to spool them.

The S366's are a no brainer as well. Proven to make 1300+ on 5.3/4.8 platform many many times and are great quality turbos.

 

What turbine wheel/flange/ar on the 475? I'll agree that the 475 would not be a great choice for the application, but didn't expect to see the big drive pressure numbers at 25 psi.

 

Wow, that's a great idea. Easier, quicker and more sensible.

 

Now I'm thinking that swapping on the S480 is going to happen once I can get some time into tuning the S475 tune (I just have to convince my son that I need his turbo for a weekend for science .)

 

That was the 1.10 T4 with the smaller 83/75 exh wheel. Also had the junk ebay 12x3x32 IC everyone used back in 2013. I've seen some high pressure drops across those cores. So not sure how much pressure the turbo was actually putting out. But yea, backpressure was up there!

 

The 83/74 is not a good turbine for that application, there's no reason not to go T6 96mm 1.32, or possibly the 1.58 with what the goals are. With all the options in the S400 frame, the turbine section info definitely needs to be included in the discussion.

 

I Agree should have mentioned that. I'm not use to seeing the T6 S400 turbos on any small bore motors, guess I just assumed. My S480 1.32 T6 was 1.4:1 on my 4.8 around 7k and 20lbs. I still don't see a T6 S475 making much past 25lbs. Though when the BP starts to take of on the T4 the T6 will def shine.

Holdners latest T4 vs t6 S475 video shows the power was pretty much identical when BP was the same between the two up to 12lbs, where he stopped... Then claimed the T4 is a better "1000HP turbo" and that T6's didn't belong on small bore motors.

 

That's exactly what I thought - why not push it another 3-5 psi and see what happens? Nah, let's make some generalization without figuring out which one gives up 1st. SMH

I took just the opposite out of his generalization - why mess around with the smaller T4 when the T6 performs just the same?? It would seem obvious to the layman (me) that a T6 1.32 would have more potential than a 1.10 T4 if turbine sizing was the problem. But what do I know? I couldn't figure out why he stopped.

I guess if you're talking only to the street car/cruise in crowd, then the T4 packages better.

 

He always talks down my comments when I call him out. Says I'm talking "race cars" and he isn't. Yet he is throwing aftermarket heads on a JY short block so he can say he makes 1000HP on baby boost. Makes no sense. The guys buying JY engines for $500 aren't gonna go blow $2500 on heads. Buuut what ever. His show is interesting, I subscribe and thumbs up all his stuff. Good for him making a living off something fun!