Supercharge or twin turbo ? on my 305

[frank280zx]

Since now i have the car running I’m wondering a couple of things..

I need more power (doh) somewhere in the next year i want to go to a 383 but this is a great test mule to get all the parts mounted and working the way i want. next to that it is what i had so saying: 'if you want more power get more displacement'

 

http://www.youtube.com/user/frank280zx#p/a/u/0/R9uo9Pku82E

 

Scenario 1:

 

I have the SS autochrome Twin turbo headers and i have twin KKK 16 ( t28's), Or I could upgrade for bigger el cheapo Ebay specials..

Now this ads complexity in plumbing exhaust tubing, oil feeds and drains etc. But the upside is cost.. this could be done for around 1500.

 

Scenario 2:

 

Supercharger! I have non of this .. but it is tempting, I can buy em without any oil lines.. it is bracket mounted and driven by a pulley.. I can leave my exhaust system alone! and it kind of goes with the American engines temperament of low end grunt..

It is by far the most simple route but it wil cost about 3000....

 

 

So your opinions please! the car is mainly a track day/ ring tool not daily driven. And maybe someone has a set up for sale

[Tony D]

Wait for Pomona, and get with 'supercharger guy' -- you know the one! Right at the end of the row...

[355Z]

I'd go with the twins, but I'm partial to turbos.

[ModernS30]

both! BOTH!

[Xander]

How about getting it tuned NA first you slacker

[Xander]

and get some pictures of the car and post theme here.

[dustin280zx]

Supercharger. You will have one less thing to worry about which is under hood temps and it would be better suited for a track car due to the linear power curve. My other reasoning is that the displacement of your 305 and 383 is too great to use the same turbos that would be optimal for your 383. So you would have to buy another set of turbos when you install your 383. Also if you are running a blowthru the transition from a 305 to 383 on a properly set up carb (this means it has dual BRPVS of some sort) is BASICALLY a jet change, cam adjustments and setting idle mixture with a supercharger. With turbos you start from scratch again. If you were drag racing I would go with a twin setup.

Edited July 29, 2010 by dustin280zx

[frank280zx]

How about getting it tuned NA first you slacker

 

Haha well you have to keep making plans! Tuning is one... but what do i do when im on ebay when i cant try to source a deal on a charger?

[frank280zx]

Supercharger. You will have one less thing to worry about which is under hood temps and it would be better suited for a track car due to the linear power curve. My other reasoning is that the displacement of your 305 and 383 is too great to use the same turbos that would be optimal for your 383. So you would have to buy another set of turbos when you install your 383. Also if you are running a blowthru the transition from a 305 to 383 on a properly set up carb (this means it has dual BRPVS of some sort) is BASICALLY a jet change, cam adjustments and setting idle mixture with a supercharger. With turbos you start from scratch again. If you were drag racing I would go with a twin setup.

 

Dustin,

I have a MsS fuel injected set up so it takes tuning, and maybe bigger injectors ( but seeing how pig rich it runs now i doubt they are not sufficient)

But thanks for the pointer to the supercharger, i am leaning that way to (apart from the cost) Mainly because i don’t need 600HP.. I need power on demand and a linear curve so i don’t need to change gear sets for every track (not that i could do much more than changing the diff)

 

Maybe it is good to point out that im looking for 400 to 450 to the wheels in this car.

BTW i love your ride

[Tony D]

and get some pictures of the car and post theme here.

 

 

[Tony D]

RE: Turbos for a 305 wrong for a 350.

 

If you size the compressors for optimal horsepower of 450, and the A/R on the exhaust side to be optimized for higher rpm operation on the 305, the result will be supercharger response on a 383.

 

A turbocharged 400hp 383 is childs play, under 10psi. Especially if you have a decent cam that lets you get some useable rpm from the engine. Keep it below 6500 for longevity, run it at 5-7 psi of boost, and you're going to be amazed at what you can get from an SBC and a couple of small hairdryers.

 

Actually, technically, for a 305 OR a 383 you could use twin stock Datsun Turbos with internal wastegates (one on each bank) to suppor 400HP relatively easily. You got the manifolds, you got loads of turbos with .82A/R hot side housings. Just some tubing to equalize turbo wastegate signals and you're set. No intercooler, no rpms over 5500rpms, 400HP and low cost. All with crap you already have in the barn.

 

"Pleased to introduce myself, I'm a man of wealth and taste..."

[frank280zx]

 

 

 

there is a vid of the car in the first post guys

[Tony D]

But it's lame.

Buy a real camera, and get some decent pictures.

[frank280zx]

But it's lame.

Buy a real camera, and get some decent pictures.

 

i'll leave that for you i rather spend it on parts

Edited July 30, 2010 by frank280zx

[dustin280zx]

If you do go with two small turbos with a t3 housing don't forget about back pressure as that can decrease the longevity of your engine. For a track car, I would have to disagree with tony D based on my experience that you should run some type of inter cooling. A cheap a/a or a water/meth setup, not so much for detonation, but to help keep engine temps in optimal range as you know to hot will decrease performance and longevity. Just one less thing to worry about while your at the track.

 

You may want to look into weight added as part of your deciding factor as well.

[Tony D]

Intercooling a 5psi turbosystem is nice....but I doubt it's in any way 'mandatory'. 280ZX's will run all day long at track events without an issue.

 

Seriously, he will not need more than 5 psi to get the HP he desires. 7 at the max. At those levels intercooling is nice, but not mandatory.

 

As for 'backpressure' that's something that has to be measured. The turbos he has available in Europe were .82 A/R on the hot side, not .63 like the USA. With twin 3" exhausts off the turbos and a SBC that will likely peak at 5800rpms, each bank pumping 2.5 to 3.0L of exhaust gasses this is like two four cylinder stock Z engines.

 

There's a lot of tendency to overthink this stuff and overdesign it 'because that's what's right'---but those turbo cars lasted 300K miles, without an intercooler, so I'm thinking longevity should be fair in this application.

 

I would agree this would be a fail on a 383 with a US Spec Turbo (0.63 Hot Side A/R), it would likely work fine for a 305 streeter. But anything larger than that would likely be restricted bigtime. But with that 0.82 it's opened up enough. In any case it's like Frank said: getting it set up and then putting in a 383 will be later. At that time he can get a larger A/R (say 1.06) set of turbos.

 

But for trial fittment, and running around cheaply, a couple of ZX turbos will give him that power level, no doubt about it. They will flow 200bhp and still be in the sweet spot of the compressor end of the turbo. If he was trying to go to 600hp, then yeah...no way will the ZX stuff handle that reliably. But for only 400 (or 200HP per turbo) that's child's play! Hell, that's the RATING of the ZXT in Europe (200HP).

 

I'm not sure what the T28's came off of, but they are likely far smaller in A/R than the stock ZX units. I have seen a 'Twin Datsun Turbo' ghetto rigged onto a SBC before, which is why I mentioned it. The performance was surprising for the money expended. Very stout! And with EFI that can adapt to the lower temps of a non-I/C setup at 5-7psi, it should be far more reliable than a carb in that instance.

Edited July 31, 2010 by Tony D

[Xander]

Hey Frank,

 

This is the only decent picture I got.

[Pyro]

to make 400hp at the wheels then the engine will need to make 480 at the crank.

 

to make 480 hp with 10 psi of boost then the engine will need to make 285 hp before turbo charging. (1.68 x 285 = 480), 10 psi pressure ratio = 1.68

 

to make 285hp with a 305 will take a little head work or a "good "set of heads and a small cam (not a stock cam)

 

if you run a set of L28 T3's then you can't use any valve overlap due to restrictive exhaust turbines causing lot of back pressure.

 

So a cam with around 260 degree on the intake, 250 on the exhaust with 114 lsa, then a maybe set of vortec heads will get you to 285hp. (maybe)

 

then add 10 psi to get to your 400hp at the wheels goal.

 

a stock L28 T3 will "max out" between 200 and 250 wheel hp, depending how you define "maxed out". so that is 400 to 500hp with a twin setup.

 

if you just add 7.5 psi of boost on a stock 200hp engine then it will only make 300hp (1.5 x 200 =300), 7.5 psi pressure ratio = 1.5

 

hard to make a lot of power with a 305 due to the small bores which restrict the flow from the heads (small valves and small ports). better to use a 350 (big bore).

[frank280zx]

I decided to run it as is forn now and make sure all other litlle things are adressed first, then ill swap in a 383 or even a 400 with some brutal NA power!

I have seen crate engens for between 5.5k and 10k dollars that produce over 500 HP so i guess that is my ticket!

Edited August 10, 2010 by frank280zx

[Pyro]

here you go.

 

490hp, 525ftlbs with a 400 sbc on 87 octane.

 

http://www.chevyhiperformance.com/techarticles/148_0401_chevrolet_406_ci_engine_build/index.html