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How would a vf39 work on a wrx as aposed to like a vf 30 or vf 34? Has anyone done it and what are the pros and cons? Of course i would get the injectors and pump and tune to go with it!
 

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Compared to the VF39, the VF34 would be a better choice.

That said, I'd go with a monster 16G from Deadbolt Enterprise. It's cheaper than a VF34, with less lag and more fun.
 

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Deadbolt should offer a ported big 16g. That would own. I mean it would pretty much put our cars on the same level as the evo almost mod for mod.


i don't know what the heck is up with the td04-18t port they just came out with...
 

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any flow charts of the 16g and the vf39? i think i can find some vf34, but it's hard to compare w/o seeing the flow charts.

dR
 

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not hard. the vf39 is the same thing as the vf34 with a smaller ehxaust housing(from what I know). This basically means less efficiency up top with some better spool.....
 

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I'll probably get flamed for this, but I have no interest in learning the details of flow chart reading and sitting down with a calculator and figuring out operating points on a flow chart. Given the 2.0 engine's flow (which I don't know), can anyone tell me how to look at a chart and figure out at what RPM a turbo will hit 15 lbs of boost?
 

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I'll be adding a vf39 later this week. I know a vf34 has more top end, I am interested more in autox and road course than 1/4 mile, and altitude makes lag suck even more.

I believe it has been asked, but I'll ask again - Anyone got a vf39 compressor map?


As far as how to tell when a turbo will reach 15psi, no. But, you need to start with the pressure ratio. That's the pressure on the high side of the turbo divided by the pressure on the low side. So, basically,

(atmospheric + boost + pressure drop across IC) / (atmospheric - pressure drop across intake)

You want to be in peak efficiency as much as possible. That should give you a start, I think.

Perhaps seeing at what rpm a pressure ratio of 2.3 (for you, maybe) matches up to peak efficiency. That might work, I dunno.
 

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I realize now the stupidity of the earlier post - the point at which a turbo begins making boost as much a function of the hot side as the cold.

Having said that, is there any way to predict the onset of full boost for the above mentioned 16g?
 

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"Having said that, is there any way to predict the onset of full boost for the above mentioned 16g?"

I don't like that question much. I mean ANY turbo will have different results on different setups. Coating the exhaust of a car(before the turbo) can change the spool of any given turbo more then 300rpm. There are many other things you can do to get the boost to build earlier too.... I would think the 16g would be very similar to the vf34 in spool characteristics(if that helps any), but there is no way to tell how it will work on your car till you try it(imo). On another note, I would think that the vf39 would have a similar map to the vf35, but ya never know....

peace
 

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Anyone have some more good info on the 16G vs VF34 scenario? I was planning to buy a VF34 until I saw the TD05 from Deadbolt now...would STi injectors be suitable for both?
 

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SERacing said:
Anyone have some more good info on the 16G vs VF34 scenario? I was planning to buy a VF34 until I saw the TD05 from Deadbolt now...would STi injectors be suitable for both?
I have driven both the JDM Evo 7 (TD05-16G) and a JDM STI (VF30). The Evo's power delivery is strong and linear throughout the rev range, while the STI has a pronounced flat spot between 3000-4000 and kicks hard once full boost is achieved. After driving a VF34-equipped US-spec WRX, my opinion is that the reduction in lag between the VF30 and VF34 is, at best, minimal.

If I were keeping my WRX I'd have a ported and polished TD05 on order. According to Deadbolt, STI injectors are sufficient for the TD05.
 

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AlexWRX said:
I have driven both the JDM Evo 7 (TD05-16G) and a JDM STI (VF30). The Evo's power delivery is strong and linear throughout the rev range, while the STI has a pronounced flat spot between 3000-4000 and kicks hard once full boost is achieved. After driving a VF34-equipped US-spec WRX, my opinion is that the reduction in lag between the VF30 and VF34 is, at best, minimal.

If I were keeping my WRX I'd have a ported and polished TD05 on order. According to Deadbolt, STI injectors are sufficient for the TD05.

If I'm correct the EVO is a different turbo than than the SRT-4 and the deadbolt/FP unit even though all 4 are designated TD05-16G.
 

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verc said:
If I'm correct the EVO is a different turbo than than the SRT-4 and the deadbolt/FP unit even though all 4 are designated TD05-16G.
you are correct- the evo turbo is a twin scroll turbo...
 

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EVO turbo:




Deadbolt 16G:




Deadbolt 18t:





As you can see the EVO large 16g 0wns the small 16g, and it also 0wns the 18t compressor. That being said, I really wish FP would come out with a large 16g. That would be much more versatile and we could have our wrx's run anywhere from 13 to 11 second 1/4 miles on the same turbo depending on gas and boost and how aggressive we tune it.
 

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I don't see the same thing you see. The way it looks to me, the small 16g is more efficient then the big one. This is cause the people who made the big one just put a bigger wheel in the intake side without actually making the housing any bigger. I would much rather have the small16g then the big one. I mean do you see the center where the 18t and the small 16g say 77 and the big 16g says 71. That's tha max efficiency... I mean, if you look at all the turbos while they're above 68%, the other two turbos own the big 16g. The other two turbos will also spool earlier....... I don't see why a few more cfm is worth the loss off efficiency and spool, which is why I would get either of the other turbos over the big16g.

peace
 

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I'd have to agree with hippy here.

Looking at the Deadbolt vs. the Large in the context of need, the Deadbolt seems to own.

Based on some very crude calculations a pressure ratio of ~2.33 and a CFM of ~487 should have a WRX pushing 18lbs at 7,000 rpm.
(assuming a 1.5lb pressure drop from the intercooler and the vehicle is at sea level)

This would make for a pretty hard core WRX in MHO.

Now if we look at the maps where a PR of 2.33 and a CFM of 487 cross I see the EVO turbo at ~62% efficiency and the Deadbolt at ~70.5%.

I would still like the see the Large come out for the wrx though



;)
 
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