Turbo max HP figures ?

[kalium99]

Hi,

 

Just wondering how most Turbo's perform relative to their Advetised HP rate. I see some turbo's which are 'rated' at say 600HP...but people who are using them may only be getting around say 400HP out of them. Is it a matter of just turning up the boost (only if the engine can handle it of course) to obtain that advertised power?

 

Also....if I was only getting 400HP out of my 600HP turbo....would I get more HP out of say a 700HP rated Turbo, or would it stay about the same?

 

Its just that I see people who look at a HKS turbo which is rated at a certain HP, and they go "That turbo will give me xxx HP"....but I have never seen it work liek that.

 

Cheers

[Tony240ZT]

As you've found out making horse power isn't simply about bolting on a super big turbo and praying to the turbo gods that it makes as much horse power as the sticker says it will make.

The best way to get the most out of a turbo is to properly pick out the size that is right for your engine. It may be true that the properly sized turbo will have a higher potential than your engine is capable of, but if it is by a large amount (like 200hp ) then you are probably not utilizing the turbo in the best way possible.

 

It is also possible to have a turbo too small in which case you end up creating too much back presure in the exhaust manifold, and a lot of heat is created. As we know heat is bad.. Lag is bad too, it's that sweet spot in between that you should be looking for.

[Guest Anonymous]

Those ***(*?)hp figures they gather from flow capabilities. Flow a certain amount of air, add the appropriate fuel, and in a perfect system (VE 100%) that's what you could make (at maximum flow). Well, back to real world.. our sohc systems & turbo systems wouldn't exactly dream of 100% vol efficiency... more like 85 or so at WOT around 4000 rpms or so, and that's where/how most people optimize their systems. The stock turbo cam and turbo is optimized for that quick boost, but not for a constant torque rise through 6000 rpms.. You could do things like getting a better optimized cam (search the recent thread), port matching and polish (even a home job), a max efficiency (compressor, turbine, intercooler) turbo system. I think you'd find 400 hp wouldn't be all that hard. Just keep in mind everything that goes with it, upgraded fuel, controlling that fuel, exhaust, etc etc.

I am shooting for 300rwhp out of my l28et, and I plan on using either a 60-1 turbo or a t04e-57 trim. I've figured this out with much assurance, because I've researched and gotten help from others

I think both would probably support 500+ hp, but I'm not making near that. Also note that the max comp. flow lies in the far right of the map, at a certain boost rate, and usually will be less than 70% efficiency (just the way things work out), now you've got a bunch of hot air on your hands. This is why most size larger than they need, and leave room for expansion. Kind of a two steps forward, one step back kinda deal.

a good place to start would be www.turbofast.com.au

my favorite turbo site, they have easy java input, you don't really have to know much about air characteristics to test compressor maps. Figure out your goals and I'm sure many on this forum can help you achieve them.

good luck with whatever your project may be

-980mak

[Lockjaw]

These guys are on the money about the turbo deal. I have an H3 hybrid, and the H3 is supposed to support lots more HP than my car dyno's.

 

The best thing you can do is research the turbo's you are interested in, and see which one best suits your needs.

 

For example, a t3/t4 hybrid, with a stage III turbine wheel will make varying amounts of hp, depending one what compressor wheel you put in it. However, lets say you put a 60-1 compressor wheel in it. If you have the .48 AR turbine, you will be hard pressed to get much over 300 RWHP, even though the compressor is good to 500 or so. Change to a .63 AR turbine housing, and you are likely to see 400 at the wheels, and go to the .82, and you could get 475 or maybe a little more, provided you had the fuel to feed it.

 

Same turbine wheel, same compressor wheel, three different turbine housings. What are your trade offs? When you get boost and boost response versus top end hp. A fast spooling turbo is very responsive on the street, and slower spooling one is incredible once it gets spooled, and something in the middle of the road is where most people go.

 

Check the flow rates and efficiecies at the boost levels you want to run, and leave yourself some growing room. I haven't met a turbo person yet who has not ended up "upgrading" to a larger turbo. I am going to upgrade myself very soon to a 60-1. Just make sure you can supply the extra fuel needed to grow, or you will have one nice boat anchor.

 

Good luck.

[pparaska]

Lockjaw, thanks for that explanation. But it brings a question to my beginner-turbo mind (I just drive my Eclipse GSX, not much else):

 

Since a smaller turbine housing to wheel size ratio gives better low rpm spoolup response, but the top end suffers (probably due to not being able to move enough flow through it), wouldn't two smaller turbos give you the best of both worlds if properly sized (great low end and top end)? I'm talking about parallel, not sequential setups. And probably with a balance tube between the exhaust feeds too.

[SleeperZ]

Pete - the problem with going to two small turbos is you divide the exhaust flow between the two. I believe the way the math works on this is the turbine acceleration is proportional to the square of the exhaust flow. By cutting the exhaust flow in half, you may actually increase the spool time, unless your turbines have less than half the mass of the original one. I'm not sure I completely understand this relationship, but most of high power folks go with one big turbo without seriously compromising spoolup.

[Lockjaw]

Pete we have a guy on the board that has adapted his 3 liter engine to run twin 16 g's, which are pretty good sized. They are an upgrade for a GSX.

 

Without getting into real specific detail, generally two turbo's on an engine will be more responsive than one big one, however the one big one will make more power, but will have more lag. As your engine size increases, then going to two turbo's is a much better idea. (V-8's in particular)

 

With today's technology, some of the small t25 or t28 wheels flow as much as some t3 and small t4 wheels due to improvements using cnc machining, computer modeling, and use of diff materials, and aerodynamic improvements.

 

Extrude honing the housings is also said to make a huge difference. It all boils down to a compromise. You have to be willing to accept some sort of tradeoff somewhere, it just depends what you like.

 

My personal opinion is to really do your homework on set-up and research, talk to some people who know there stuff, and go from there. I hybrid turbo is a great way to go on the inline 6, and I would not get the .48 ar housing, unless I was autocrossing. Stock is a .63 and it works well for me, I get full boost by 2800rpms. A.82 is probably better suited for someone who plans on doing alot of drag racing. I am not to concerned with the compressor wheel, and would be happy with any T4 wheel up to the 60-1 on a hybrid with a stage III turbine wheel, depending on your power requirements. I would stay V trim or higher, again unless you are auto crossing.

 

The TO4E housing and wheels are a different story and I would go 50 trim or higher. I don't know much about the E wheels, but computing some flow points on each compressor map should help. Shoot for the most efficient one for your application, again giving yourself some growing room.

 

Going from a stock turbo to a hybrid can give you a scary power increase, but in short order you will get used to it and want more. Be ashame to be topped out that soon, which is why I like a turbo that gives you growing room.

 

I could write a book about turbo's and probably leave something out. My best advice is get the most efficient stuff you can, and leave growing room, and you should be happy.