VF-34 compared to td05-16g

[magicmike]

found this while looking for a comparison. I dont know how accurate but I could not find compressor maps for the vf34 anywhere. (note, the vf34 has the same flow as the 30 just quicker spool due to the ball bearing vs bushing design)

IHI VF-30 435 CFM at 14.7 PSI <--- estimated
Small 16G 505 CFM at 14.7 PSI

IHI VF-30 460 CFM at 18.0 PSI <--- estimate based on trap speeds of cars running this turbo
Small 16G 490 CFM at 22 PSI

full comparison of much more here

http://forums.nasioc.com/forums/archive ... 98630.html

[vrg3]

I'm not sure those numbers are useful for us. Unless my understanding of turbochargers is all wrong (and it may be!), those numbers are only significant for the motors they were tested on.

I'm assuming those flow numbers are at the compressor inlet.

Flow at the compressor outlet is determined by the engine's displacement, speed, and volumetric efficiency. Flow at the inlet is determined by flow at the outlet and the density ratio across the compressor. The density ratio is determined by the pressure ratio and temperature ratio. And the temperature ratio is determined by the compressor's efficiency at that pressure ratio / airflow site.

Someone correct me if I have that wrong.

So if those numbers are for WRXes, the engines have different displacements and volumetric efficiencies. Our engines wouldn't land on the same pressure ratio / airflow site on the compressor map.

How is trap speed being used to estimate flow? Just making some kind of horsepower estimate and then estimating how much air is required to achieve that power? Seems pretty imprecise.

I think we need to find a compressor map for the VF30/VF34 compressor.

[magicmike]

I'm just trying to figure out if my vf-34 was a bad choice? it seems like it males a ton of boost to me so I think it is ok, but I think everyone else on here with an upgrade has a td05-16g

[vrg3]

It wasn't a bad choice.

The TD05-16G is just an easy choice, since it fits very easily and has been well-proven in gazillions of WRXes worldwide.

In fact, I don't think the numbers you posted there even point to a big difference between the two turbochargers.

Anyway, your build isn't complete yet. You still need better intercooling, and better engine management.

And I still say you should reconsider your compressor inlet piping. I mean, your compressor is sucking through what's basically a restrictor half the size of its inlet, right?

Believe me, when you have it sorted out, your car will be a monster.

[magicmike]

And I still say you should reconsider your compressor inlet piping. I mean, your compressor is sucking through what's basically a restrictor half the size of its inlet, right?

I agree with you that it "looks" really bad, but given the performance wise aspect I dont think its hurting anything as of yet. like I've said before I reach full boost in first gear and hold full boost in every gear which is pretty hard to do from what I understand...

[azn2nr]

that and if you look at the space there there really isnt much of a choice regarding space until you put a new top end on and are capeable of running intake under the mani or raising the turbo up higher.

if i can figure out the "an" fitting sizes for the oil suply line then raising the turbo about 4 inches will allow better intake flow.

one other thing is that (and this is from word of mouth) between the factory affair sti ihi turbos, the ones that suposedly flow more air only flow a little more than the smaller sti turbos.

[vrg3]

Mike - I don't think the fact that you're able to hit full boost in first gear necessarily means the restriction isn't hurting things.

Basically, the restriction causes a slight pressure drop, right? So in order to achieve a certain boost level, the compressor has to produce a higher pressure ratio than without the restriction. Pressure ratio is very roughly proportional to compressor speed. So let's say there's a 1 psi drop because of the restriction. Your turbo might then be spinning at 160,000 RPM instead of 150,000 RPM.

That small difference in rotational speed is not a big deal in terms of spoolup, but it could be important in terms of compressor efficiency. Maybe.

Jason - Well, you could do better if you modified the compressor housing. Even a sharp 90-degree turn would be better, I think.

What do you mean by figuring out the AN sizes for the oil supply line? I believe the oil supply line uses a 10mm banjo on the turbo side and a 12mm banjo on the head side. You could replace the line with some banjo-to-AN adapters and a short piece of braided hose. I'd say -4 AN is probably about the right size. You could probably pick the right pieces out of an Earl's or Aeroquip catalog. Is that what you mean?

Or maybe you could even find a stainless steel braided hose with a 10mm banjo on one end and a 12mm banjo on the other. I bet one of those companies that manufactures custom motorcycle brake lines could do that for you.

[azn2nr]

something like that. bascily i want to raise the turbo about 4 inches (estimation because i dont want to go out to the garage and measuer) so that the inlet is level to the manifold alowing a stright flow. kinda like a twist but without the complitation. clearence may be an issue but thats easily remidied by a spare hood and a zipsaw.

one more thing. i dont want to modify the turbo itself. i know that if i did i could get it to fit without the "restriction" but without modifying the inlet there is no other way. unless the guy that put a tdo4 on shows what he did and its better and/or something i havent thought of yet.

[BAC5.2]

You still have a downpipe to deal with if you raise the turbo.

[vrg3]

Wouldn't you need a custom uppipe and downpipe then?

mreese basically just cut the inlet pipe off and welded a sharp elbow in its place:

http://bbs.legacycentral.org/viewtopic.php?t=15346

I understand why you guys are unwilling to modify the compressor housing, but I still say it's the best way to make the turbo fit the car.

[azn2nr]

custom dp and up is right.

i would want to do somehting like that but in a different fassion. if i could get a metal pipe to slip over the turbo inlet and seal with a some sort of hose clamp that that is workable. it would alow me to get the elbow close enough to the turbo to clear the manifold. but its still cutting it pretty close when you consider that a 2 1/4 od pipe hits the top of the inlet of the turbo and the manifold while standing stright up.

[vrg3]

I'm not sure I follow what you're saying about a 2-1/4" pipe hitting the top of the inlet of the turbo and the manifold while standing straight up... I'm having trouble visualizing what you're describing.

You can't reasonably get metal pipes to seal against each other unless you make them a press fit. What mreese did was cut off the little bit of pipe sticking out of the middle of the compressor housing and then weld the elbow on, and it looks like he could have made it even tighter if it had been necessary.

It looks like the elbow was constructed by cutting a straight piece of pipe at a 45-degree angle and then welding it back together rotated.

[BAC5.2]

Vikash - Can you check your g-mail?

Send the turbo to Deadbolt, and get a 90 degree elbow installed

[azn2nr]

if all else fails ill have a local turbo shop do that. that and im trying to get a 16g off an old wrx from a dismantler for cheap just to compare power increase charteristics and to upgrade to 18g internals.

[-K-]

I would not try to raise the turbo to get a straight inlet. I would try to rotate it so the inlet is straight and pointed at the airbox.

If you are doing that much work I would change the heads and manifold to 97+ WRX that has the straight inlet.

[vrg3]

-K-, when you put the T-bird compressor on your turbo, you had to swap the T-bird compressor housing on too, right? What is the geometry of the T-bird compressor inlet, and what did you have to do to make it fit right?

[azn2nr]

vrg3 the inlet of the turbo for a stright out turbo sticks out a little. the part that mrreece cut off is the part that the pipe hits while in a vertical position similar to what it will have to be to acomadate the original inlet pipe.

i realize that a tist is a workable option that requires tons of work. it may come into play but not until next year.

as for heads and top end im considering 2.5rs phase 1 doch heads and top end as 97 wrx heads are hard to come by unless thier attached to the rest of the motor in which case id just swap the motor.

[-K-]

When I went to the T-bird compressor I was able to use the stock 90deg inlet. It took some work as the bolt pattern is different (had to drill new holes in the mounting flange) but it just fit once I clocked the outlet to fit the IC piping.

I figured the heads would be hard to come by. What about USDM WRX heads? There should be enough of the in jy's and I see enough v7 and v8 heads sold to swap out the stock ones....

If do the 2.5 head swap I think I'll stay SOHC, just to piss off everyone that thinks DOHC is better.

[vrg3]

Jason - Right, that "sticking out" part is the the "inlet pipe" I've been talking about... Why is it tons of work to just cut that off and weld/epoxy on an elbow?

-K- - Oh, that's cool that the stock inlet worked. So presumably the T-bird turbo had some kind of angled inlet as well?

[-K-]

The T-bird inlet is bigger (but I port matched the 90deg inlet to the new compressor housing) and comes with about a 30deg bend.

[morgie]

Only bad-side of the 16G is it's tendency for boost-creeping.

I've been experiencing some boost creeps on cold weather from 10psi, rising up to 14psi over 5000rpm. Ok that's not a big problem since my setup can handle this no prob... but a friend here with a 95 talon has boost creeps up to 21psi !

so if you get a 16G, maybe a wastegate porting before installing it could be interesting