Im trying to decide on a turbo, looking at a T04b or e
I have 9.4 rotors and a half bridge, just broke in with no turbo (S4 block)
only shootin for 10-13 psi,
and limiting the engine to 7800- 8000rpm

not sure if i should use a .96 undivided or 1.12 divided, any input?

Im planning on autoxing and tracking, maybe a drift event or two.
So i would like good midrange and quick spool, not focused on top end too much.
I just dont want to choke it if i need to stay in gear
can i get away with a single 46mm waste gate at that low of boost?

I'ill be running either a MS3x or Haltec
with an areomotive steath 340 pump
fuel lab digital pressure reg
720 (or 680s) mains and 2000id (or 1680s) secondaries
short charge pipe v mount
pre and post turbo water injection with about 200cc injectors
ok so far?

Im shooting for mid 300's at the wheels

 

I'm a little confused. You did a half bridge, so presumably long duration on the secondary ports. That hurts your low end volumetric efficiency. It's like putting a big cam on a pushrod V8 and wanting low end torque. Your goal is an autox or road racing kind of car. A bolt on hybrid (BNR stage 1 maybe) or small single turbo with stock or mild street ports are going to be best for that application.

Then again, things happen. Plans change, and maybe you decided this low end torque thing late int he game. That being said, go for the divided hotside if you have an actual divided manifold. The pulsation effects are well proven to greatly help spool the turbo.

 

Ptrim or Qtrim divided exhaust housing with a 1.15 AR but limiting the motor 2 8k will affect performance.Bridgeports wont stop pulling at high rpms if everything is set correctly!

 

Is the single 46mm enough to keep it under 13 psi?
I'm going to run the 1.12 divided if it will spool faster than a .96 undivided
Also I'm using the stock turbo intake for now, with plans of an itb set up down the road sometime

yea im planning on autoxing and all that but this is still a street car, for fun no other point than that.. and hooning
dont hate.. peace an junk

 

Bueler?

 

if you are referring to the HKS style 46mm with the 4 bolt flange on an HKS style manifold, I'd say probably not. Not unless you had a cat.

 

Is the manifold divided or undivided? You'll want to match the manifold. Since you're going for an autox specific setup, some of the conventional wisdom can be thrown out. If it's a divided manifold, I would look at an .84 or 1.0 housing. A 57 or 60 trim TO4E will net you mid 300 whp at the boost level you're wanting to run. With the .84 housing on a street port the 57 trim spools like a stock FC turbo. With the bridge port it should be no worse, if not better. Since you're wanting responsiveness over ultimate power and you're looking to limit top end revs anyway, there is no reason to go very big on the exhaust side.

I've run the FD HKS cast manifold with a Tial 44 on a half bridge and had no issues keeping boost at 13 psi. That combo made 430 whp @ 13 psi with a, iirc, 62mm Precision and a 1.0 housing. Full boost around 3500 rpm.

 

Hmmmm. Now I'm a little confused. So you're saying a smaller turbine housing could be better for quick spool, which for a street or stock port makes sense.

But won't the timing overlap and the increased back pressure from the .84 cause more dilution and less torque?

Or will the quicker spool negate the dilution from overlap?

I was planning on a 60 trim TO4B
I haven't looked at maps but I hear they flow more at lower pressure than the E

And I was looking at the two previously mentioned turbine housings because I can get those for about $400 for the complete turbo

Thanks for the help, keep it comin.
All the motors I have built including piston engines have all been high revving, long duration, lots of over lap, NA fun stuff, still a boost newb

 

Oh btw can't edit from phone but I was going to try to use a FD divided manifold.
If that wont fit I'll make one with a bigger waste gate, but I'd prefer not to build my own as I don't have my own shop or a TIG

 

Well in this case less is more. What you want is a turbine wheel exducer around 55mm in a 1.0 a/r housing, or alternatively around 0.8A/R with a 62mm turbine wheel exducer and a standard port engine.

PT5862CEA with a T4 Divided 0.84 A/R would make a lot of sense.

T04B is Offered in a 60 trim wheel but that is called a T04B V-trim, are you sure you're not talking about a T04E 60 trim?

I think you'd be faster with a standard port engine and a standard 89-91 turbo on 0.9 bar internally gated.

You'd also be faster with a V-trim s5 turbo.

Bridge porting with a small turbo is a downright stupid idea.

 

"Torque", with a turbo engine, is all about getting it into boost. A bridge-port is going to make more torque throughout the RPM range relative to a street-port (NA). But, as you are aware, you run into issues dealing with the overlap. You've created a situation where you need to make compromises.

- You have an engine that is bridge-ported
- You say you only want 300-350 whp
- You say you want quick spool (who doesn't?)

And all of that leads to this...


You've chosen very poorly to begin with. The engine is poorly matched to your stated goals. The smallest turbo I'd go with personally is the 62mm I mentioned. With a p-trim and 1.0 hotside it will spool very nicely and will work well. However, it's going to make way more than 350 whp at "reasonable" boost levels. If you have to limit the turbo to less than 10 psi you've put together a poorly mixed bag of parts. Anything smaller turbo-wise than that and it's, as Jobro says, a stupid idea.

If you really only want 350 whp. Start over with a mild street port and a TO4E 60 trim with a p-trim hotside and an .84 housing.

 

What if you want the off-boost response of a bridge port but only want to run 6-7psi boost,preferably with a turbo that comes on fairly "soft"?

 

Build a p-port.

 

I had one. I'm far happier with the bridge engines.

Or are you suggesting peripheral port and no turbo? My question was not facetious, I really would like to bolster the 3000-6000rpm range even more. The bridge is way better than any street port but want more, MORE!

Hmm... building another peripheral port WOULD allow me to use up all of these 6-port parts that I'll never ever use. As well as these 52mm throttle bodies that I seem to be collecting. But my last p-port did NOT like the exhaust system I used to have, and I have to have a quiet exhaust. For reference, I put my current engine in the car in late September '12, the engine currently has 20k on it, and I don't drive it in the winter.

 

I will spell this out.

Power is created by chamber pressure pushing on the rotor. To get chamber pressure you need clean (not recycled overlap exhaust stroke turd contamination) correctly stratified air fuel mix in your chamber and the greatest mass possible.

You port your intake port up, BMEP is effected in a negative way until you're above about 5000rpm.

You port wide, your airflow might go up, but you are carrying **** straight out your butt back into your mouth, sounds like an efficient way to eat huh

You port your exhaust port down, you're letting the combustion stroke pressure out before its done all its work.

Your port your exhaust up, you're doing the same as taking your intake port wide.

You port your exhaust wide, you're causing abnormal wear and supporting your apex seal less.

Combining all these downsides with a small turbo. The intake exhaust overlap (porting inside wider, or porting exhaust upwards) is the worst thing you can do for a turbine that is going to increase the exhaust manifold pressure. That is exactly what a bridge port gets.

I know Americans always think that 3 is better than 2, but really 3 is not always better than 2. I'd rather have been stabbed twice than 3 times. I'd rather have $20000 debt rather than $30000 debt.

 

^ Yeah, if you port intake down or exhaust up you get higher overlap. It's like a later closing exhaust valve and earlier opening intake valve on a piston engine.

If high overlap exists, and intake pressure exceeds exhaust pressure, you will blow extra air out the exhaust port (like on a piston engine in overlap condition). That will actually cause scavenging. This can mean higher VE but it also means the compressor needs to be able to flow enough because it requires more lb/min at a given boost pressure. You'll see on modern boosted piston engines with variable intake and exhaust valve timing that they use a ton of overlap at low speed to spool the turbo, but they build a lot of boost at the same time so that scavenging can occur.

One of the reasons why pre-Rx8 rotaries need such big turbos to make power is because so much fresh air is blown out the exhaust port during overlap under boost.

If high overlap exists and intake pressure is lower than exhaust pressure, you dilute the intake charge with hot exhaust, especially if you don't have a fully divided turbo manifold and twin scroll turbo. That can increase knock and reduce output. So when you have high overlap and a slow spooling turbo, it hurts your low end even more (because of the intake dilution and lack of scavenging).

 

on an NA engine this almost never happens, the intake is never in pressure, and the rotor is always moving exhaust gasses from the exhaust port in the direction of the intake port.

its kind of why overlap is good on a cross flow piston engine, ie the gasses are all moving, and in a good direction, in a rotary this isn't the case, and as such overlap is bad, although a necessary byproduct sometims

 

Exhaust tuning will have the exhaust under a vacuum during the overlap period. NASCAR engines will have the intake port moving 80mph before the piston even hits TDC...

Plus, if you look at the way everything is shaped when the apex seal is straddling the exhaust port, it's a great example of a venturi. Maybe not a perfectly shaped one, but the exhaust gases are moving very fast nearly perpendicular to the preceding chamber.

I have a tool at work that moves 120psi shop air past a hole. It's used to pull cooling systems down to ~26 inches of vacuum.

 

Forgot the important part about that tool. Don't restrict the flow path's exit, or the air velocity drops and the venturi effect goes away and you end up pressurizing the cooling system instead.

There's an analogy there somewhere

 

Well I ordered some turbo parts.
I got garret to4e chra with a 11 blade p trim turbine,1.0 A/R T4 divided turbine housing w/3" v band outlet,billet backplate, and a billet compressor wheel that has these specs

Inducer: 59.05mm
Exducer: 76.07mm (80.42mm at extended tips)
Superback: 4.97mm (standard T04E)
Shaft Bore: 6.35mm (standard T3/T4)
Blades: 11
Extended Tip: 18 degree
THIS WHEEL CAN BE USED TO UPGRADE ANY STANDARD SHAFT T3 OR T4

REPLACES ANY STANDARD SHAFT 60-1 CAST COMPRESSOR WHEEL

THIS 4.97MM SUPERBACK IS PROPER FITTING
TO ALL T04E BASED PERFORMANCE TURBOS (MOST)

So which compressor housing do i need to fit that?
Can i just use a standard T04e housing?

 

I would think that you need an "S" style cover, with the normal 4" inlet. You're not going to machine anything right?

 

Not if I don't have to. I basically am just going to try to assemble it, clock it the way i need it, then take it to get balanced