Twin turbos or supercharger?

[andrew k.]

A question was PM'ed to me about the Garrett turbos that I decided to use. I will answer the PM. The turbos are Garrett GT25R with comp. A/R .71 and turbine A/R .68.

 

[Toysrme]

awwwwah little GT25's! They'll do really well if you're looking to stay under 500bhp.

 

[andrew k.]

I am not staying under 500 hp and these are not off the shelf turbos. There are custom cut wheels. Let's just wait and see what these "little turbos" do in the real world.

 

[Toysrme]

Slow ya roll chief. Just going by what your run of the mill GT25 does.




If you got the -40 then it's alittle different










Anywaaaaays. It'll be nice seeing the powerband of your engine on those GT25's.

 

[andrew k.]

Toys,I respect the information in your posts. I would like to get your ideas in one of my other posts (drivetrains). It is about how a Toyota 8 inch rear end can be beefed up and if it would be good for 500 rwhp after modification or should I just bite the bullet one time and change to a Ford 9 inch, please check this post and comment if you would please.Now back to the Garrett 25's. These are in fact hybrid 25's with .71 comp. A/R and .68 turbine A/R. The engine exhaust maifolds are tubular equal distance single chamber (each) to the turbines. The inducer and exducer dimensions for the wheels are cut and sized to support air flow that should produce more than enough air flow for 500+ rwhp. Maps for these turbos do not exist yet. I am working on getting them to post here. The engine will be 8.5 static compression and the boost will be whatever it takes to get my hp goal, hopefully. 550 cc low impedance injectors and an Autronics SM4 should help. Please check and comment on my post for the rear end. You are right, the power band will tell everything. I hope the calculations to acheive this are correct and I get what I am shooting for. Even if I fall short it is going to be fun to drive this truck everyday to work.

 

[JustenGT8]

No mods needed for 500rwhp Andrew. I assume some type of Hilux variant? so a G series center. I run a G series center in my IRS..admittedly a TRD one...on the track and drags with over 500rwhp and no hint of trouble yet. I know of cars running more hp than me and sub 10 sec 1/4's that use a G series also with no probs in 1500kg cars. An LSD will help and you want a clutch pack type not a torsen but the ring and pinion will take heaps.

You turbo selection should provide a good balance of bottom end response and top end flow.

 

[4000GT]

On the T28 theme, I have gone for GTI-R T28's. Slightly bigger turbine A/R, but suits my goals. I have one, looking for another at the moment. I also went for 510cc EVO injectors. Got 8 last week.

 

[Toysrme]

I've not driven, but encountered many Tacoma (hilux) and 4runner's here in the states pushing 450-550bhp (not whp) on entirely stock drivetrains front to back. I don't think you'll have any problems. Just be mindful of what it was originally designed to do. So... You know when you launch on a drag-strip with slicks. A little pre-loading will take some shock out of the drivetrain.
Turbo's sound responcive & powerful. That's my cup of tea!

*edit*
^^^ And they stop because of the stock engine pistons. Not because they think the drivetrain will be destroyed.

 

[andrew k.]

Toys,
Thanks for that. The input I have received so far also indicates the rear should hold up. It is a G series "G375 (axle code)" Toyota which looks like it is a 4 pinion LSD.
The Garrett turbos will run in the 2.0 pressure ratio range with about 30 lbs/min air flow each it looks like. Time will tell and the proof will be in the torque curve. I do have 8.5 pistons so I think that will help a lot. My ambient conditions here are in the 85-100 degree F. and 60%-100% humidity all the time. Nice dense air but always hot.