HOHN

That isn't in the Garrett catalog, it's a one-off hybrid.

Since my scenario has the primary operating at low pressures and not doing much work, we don't need lightning fast primary spoolup. It will be loafing. A larger turbine is always more efficient at extracting work. That means the 4508 will have a lower drive pressure for the same coldside flow.

A GT45 fits well in my concept of a compound setup. A GT47 would be even better, but it's too big to fit without hacking. Maybe a S488 would fit better will still providing a nice big and slow-spinning turbo.

jmo

Mike Holmen

Justin, how would you get that big turbo to lite without throwing some fuel at it. I would stick with the GT42 or you want more ump on the top end go GT45. The GT47 will work, but man it would take for ever for a VP truck to throw enough fuel at it to get it to start spooling. A big P pump or twin CP truck it would work, but us VP boys only have so much fuel. That turbo would only come to life at half track, unless you pre-load it on the lite, doing a 20+psi boost launch. You could just open the secondary wastegate and just stage with the primary. Other than at, it would be a beast on the street. A big turbo would just choke off your streetablity but once it lights up - HANG on. That sounds like fun.

HOHN

You're right, Mike. I my scenario, the primary takes forever to light. The GT47 is too big to work with the stock charger unless you use the tightest housing, and it will still be lazy.

The idea is that the primary only kicks in at the very edges of the secondary's performance. For example, you wouldn't see any cold pipe boost until 20psi or so-- not the 6-10psi the guys in some threads are reporting.

This means it will be somewhat laggy. It means it wouldn't perform well for racing. It *would* be superb for a puller though, where the load comes in more gradually and the RPM is high.

ON the street, you wouldn't see any coldpipe pressure in the first 3 gears of a 6 speed, and it won't really come to life until you're in the high side of the trans.

But this setup offers 1) efficiency 2) fast *secondary* spoolup for a DD 3) tons of growth potential. 4) Excellent EGT reduction on extended pulls.

This setup with a large primary operating at low pressure would be a killer setup for a heavy hauler.

If lag is a major concern, then the secondary is too small. The "large primary" theory increases primary lag that's caused by rotational inertia, but it reduces "system" lag by letting the secondary have better delta P to get going.

Spooling this big primary isn't so much a function of fueling. Not in the sense of whether or not it will work. Fueling determined more how fast it will spool and how far.

If I wanted to build a set that compromised efficiency to get killer spoolup response, then I'd do a tiny GT30 on top of 4202 or 4294 with the biggest housing for each. You'd have cold pipe boost at 1600 rpm with this setup!

jmo

Mountaineer

Why would I go to a larger secondary if lag is major concern ?

HOHN

That is a typo-- it should read "too big". I'm sorry for the error. I'm typing so fast, that you'll notice my spelling and such is pretty careless lately. I'm not even proofing my posts.

A long post like the one above can take me 30min to write (and I'm a slow typist), so proofing it takes even more time.

I'll be more careful next time--sorry about that.

JH

Mike Holmen

Hohn, we all need some grammar lessons from a cute teacher once in while. I just find the bigger primary you go, the more you get that stall out/bogging from your turbo(s). The bigger you go on the bottom, the worse it seems to get. Of course you could go like Hohn said with a smaller housing on the turbine. I wonder how drive pressure would respond with a big GT47 and the smallest turbine housing. I like the bench racing, it saves me from making mistakes. The more I do, the more I realize the less that I know. It’s a viscous circle. Thankfully, I'm young at heart and in the learning mode.

HOHN

Indeed

Mountaineer

No big deal, I just thought that I was missing something



X3, That's why I'm here, although the longer I'm here the more I think I know

powermad

so i just put down 400hp yesterday and im not pleased by any means were can i get more power without putting 3000 bucks into my truck???

Mountaineer

Well either something isn't right with your current setup, or you ran on the wrong dyno with the wrong dyno operator. With what is in your sig, you should be at least be at 450+ easily. There are a lot of variables. IP weak ? Map sensor ok ? What dyno was it ? What settings did you run your comp at ?
I also will have to question your trans. Is it slipping any ? How well did the jammer clean up? A video would help somewhat.
Your truck already has what it needs to be making more power, its just there may be something that needs attention.

powermad

its a stock converter and the only time it slips is a little in 2nd. stupid me didnt plug the map sensor in but i didnt know it would effect my number. everything sounded good it fueled good and with the water meth and turbo it cleaned up realy good i am working on getting the video to show u but untill the i have some on youtube my account name is powermad2001 and i have a coupld dyno and burnout videos there maybe that could help. i put down 360hp before i had the injectors and had the w/m off, this time i had big injectors and water on with the biggest nozzle. with my set up i was guessing i would put down 475 and maybe more with a good converter. thanks!!!

RonA

If you were at LCD yesterday with the black truck and the BB jammer, a bit more air would help you. Your turbo is spooling quick but there is only so much you can do with a tiny charger like that.

powermad

yea i realy want to turn this setup into twins. or get a bigger turbo what would you recommend ron? do you know if les got your truck on the dyno? i was looking for you yesterday im thinking about p-pumping my truck.

RonA

I can't help you with the BB Jammer in twins. I have no experience with it. If it comes on early and pulls well by the time you see 10psi it may work. If it doesn't pull well till you get to 20 psi, it may not work. What it does at 30-50psi doesn't matter.

Mike Holmen

Your auto may not like the P pump. There are a few engine sensors that are needed to get the auto to work. I would just put a S400 series under your turbo. You would have tons of turbo(s) then. If you need more ponies just spray in some nos to increase your power, and you wont need twins. Thats what most dyno queen rides do anyways. Any of the the top hp trucks are running spray and you have to do that if you want to win at most dyno events today. No too many trucks will push the 1000 hp barrier just on #2, on spray there is tons of rides.