turboman1

Does anybody have some good sites about this. I would like to be able to read the map and make the calculations so i can figure out the right turbo.

i know someone posted about turbo maps and i would like to read up more because eventually i am going to replace my turbo, but i also want to build up a V8 turbo gas motor (455 olds)

Can anybody give some examples of how they plugged in numbers into the equations and how they worked through the whole process to size the right turbo for their application?

Just trying to soak up all the information i can

Thanks Adam

C2O

that would be alot of figures. and it would work good if you would have a dedicated plan for the engine you were applying it to.

XLR8R

We're building up a twin-turbo V-10 Ram as our winter project... couple of HE351s off of 3rd Gens.

HOHN

There's all you need to know about this for free at the Garrett site: www.turbobygarrett.com It's a great free education. Here's a synopsis:

1) Pick how much HP you need the turbo(s) to support.
2) Calculate how much fuel it takes to make that much HP (BSFC)
3) Calculate air requirement based on air:fuel ratio
4) Select turbo based on air requirement.

Say you wanted to build a twin-turbo 455 Olds and have it put out around 1000hp at 6000rpm. We know experiencially that the 455 Olds is going to have about .55 for a BSFC on gasoline. Thus, for 1000hp, it's going to need 550# of gasoline per hour. That's about 9.2# per min. Since we're running an air:fuel ratio of about 12.5:1, we multiply to get about 115# air per minute.

Since we're running two turbo (one for each bank), we cut this in half to find each turbo's flow. So we need two turbos of ~ 60# per minute each.

But how much pressure will it take to flow 60# per min to each bank of ~228 Cubic inches? The math isn't that hard, but it ends up that you need a pressure ratio of about 2.5.

So two turbos that flow 60#/min at around 2.5PR.

The Garrett GT4088R looks like a good fit:


See how our reference point is near the farther right of the map? This means the turbo is optimized for spoolup and that surge shouldn't be an issue.


Read up more at the Garrett site and you'll have this all down in no time.

Justin

turboman1

Thanks Justin for the write up i really appreciate it

Thanks Adam

Mike Holmen

How are you planning on driving the 455? Street car or drag vehicle? How is the 455in motor being built? Whats the cr ratio of the motor? I would get the motor to around 8:1 cr and run lots of boost with methanol injection. The 3586R turbo work well in twin application and your not buying a turbo to run to 40psi of boost. You need flow capacity not boost. 10 to 12psi of boost max for the street, on methanol. Run around 30 deg's of advance and run the methanol off a hoobs switch set to discharge at around 6 to 8 psi of boost. Helps with detonation issue that occurs in a gasser. You diesel guys forgot that not too many gaser run boost over 10psi on pump gas.

HOHN

2.5 PR is right around 20psi. That a LOT of boost for a gasser. But this assumes a low .95 VE. With a big cam, a hi-po V-8 can exceed 1.05, and boost requirement goes down for a given flow. It's like having a bigger engine.

I'd personally love to build a twin turbo Big Block Mopar using the new Dart CGI block designed with Ray Barton's input. I think a turbo charged 572 could easily make 4-digit hp on pump gas at only 6-8psi of boost.

Set it up for straight methanol, kick up the boost to 20psi, and you'd have closer to 2 grand. That's a lot of HP!!

justin

turboman1

I am just trying to understand right know how to read turbo maps so as to pick the right turbo. The 455 will be in the future. I have a friend with a 97 VR6 Jetta thats running a Garret turbo (not sure which one) but it is faster at 10psi than it was with an HKS turbo at 21 psi and the garret is supposed to go up to around 30 psi. Its close to one of the highest hp jetta's in Arizona. He has water meth injection that comes on at 6psi. Its pretty quick, and it looks stock except for the big intercooler in front. Sorry to get off topic but thanks for all the help guys i really appreciate it.

Adam

turbos10

You need to plot several points of the RPM range of the engine over the turbo map. You can have a situation where at full power or part power it looks good, but you can be way over the surge limit in the opposite situation.

www.turbofast.com.au has a good calculator that allows you to plot points over different compressor maps. When you find one close, you can then play with it to see if there are any potential problems. One thing you need to understand is engine VE because it will have a big effect on the maps. Just remember that peak VE and peak torque are the same point in the power cure, and everything above and below that will decline in VE. The calculator is looking for the N/A VE of the engine, not the total VE as calculated with boost. Most engines will not get much over 90% VE unless they are very well planned out. A turbo engine would usually not get to that point due to the low CR you should have if you are planning for boost. However, the low CR will actually enhance power output since you can run more boost and fuel.

I have two turbo gassers, one racer and one pulling tractor. They are fun when they work, but tune has to be really good.....both of mine are down right now for head gaskets . I run 22psi with two stages of water and C112 on my tractor, and 12psi with 93 pump gas on the race truck. If you have any questions on the gassers I have been there and done that.

turboman1

Alright thanks for the information turbos10, i am sure i will have some questions in the future. Thanks for all the help, I have learned a lot on the last week

Adam