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Is a Hahn 20G right for me?

3K views 12 replies 7 participants last post by  oldguydb 
#1 ·
Hello All,

I'm new to these cars, but not turbochargers. '07 GXP manual trans, 3,500 miles. Stock at present. I'm not looking to go near the edge, I'd rather stay conservative. This is really Wifie's toy, but I really like these cars too.

I have a Hahn 20G kit that looks to be complete sans a few small items. Uses the stock flange on turbine outlet. Not a V-band like on earlier? versions.
Has the silicon hose ass'y that uses a Turbosmart "plumb back" bov. https://www.hahnracecraft.com/collections/charge-air-piping-solstice-gxp
I don't see the Mitsu turbochargers on Hahn's site, perhaps that don't uses them any longer. I have had no response to an e-mailed request to Hahn asking to buy installation instructions. If anyone has instructions, I'd gladly pay a few bucks for a copy.

A tune, of course. 93 octane. Chopped stock air box [extra one coming]. Any options besides an oiled K-N? Will do a full 3" exhaust of some sort. I have a 5" body high flow cat, looks to be a Solo [sold by Hahn too? - bought used with the turbo kit].

If the stock IC and piping is only going to give up say 15-20 rw horse max, I doubt that I'll fool with that area. Is the 20G worth a bunch on a safe boost level with such a combo? I understand that lag will be an issue, but I should see full boost by say 3500-3800? At similar boost levels [stock or raised but safe level], is the 20G more efficient [cooler discharge temps] compared to the stocker?

Thanks for any advice.
Dave
 
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#2 · (Edited)
Stay away from K&N oiled filters your MAF will be severely compromise. The stock GM filter is excellent.
The stock IC piping is fine and will not give up anything, on the other hand if you put that 20G turbo you will need a better IC.
 
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#5 · (Edited)
Thanks, Gents.

This is NOT a bash Hahn thread. Please note that I understand that the std 20G is "old tech". This is also not a compare a 20g W/std wheel to the latest and greatest.

Let's assume a better IC, proper exh with highflow cat, and an ideal tune.

Two part question:

Is the 20G "safe" [or safer] at a higher boost level than the stock turbo, due to the stocker getting unhappy [and hot] at the higher boost levels? I'd love to see a map for each.

How much power is the 20G worth over the stock turbo at a given boost level that would be typical for 93 octane?

Thanks.
Dave
 
#7 ·
Is the 20G "safe" [or safer] at a higher boost level than the stock turbo, due to the stocker getting unhappy [and hot] at the higher boost levels? I'd love to see a map for each.
Dave, you may not be subject to the common misperception that boost pressure equates to power, but just to restate it, you can get more power at lower boost out of a more efficient (i.e. less back pressure in the flow tract due to better, improved flow) engine. For instance, we've seen engines that produce more power using 20 psi than engines boosted to 25 psi with more restrictive intakes and/or exhaust tracts.

Stock EFR is a great turbo as the twin scroll minimizes lag - the single scroll 20G will have more both due to being single scroll and being larger. But they are out of breath at top end and although some people claim to have run them up to 30 psi, I personally doubt their usefulness and longevity there, so a larger unit is in order if you want to go higher.

For maps on the 20G, look up the Subaru WRX STI sites as they often use that one. were you looking at one with a TD05, or TD06 (larger) wheel? Note that many of the Subie crowd have complained about the 20G being too laggy.....
 
#8 ·
Hello Bill,

I understand that higher boost levels do not always equal more power. I think that I'm looking at it from a different angle than you, but I believe that I'm looking at the same thing, so to speak. Ask two different compressors to give say 350 horse worth of air, one is happy, the other maxed out. Much different results [discharge temp]. I trust that the 20G compressor is much happier at 300-350 than the stocker.


I had to take a crash coarse on the still confusing Mitsu nomenclature. I believe that the turbine wheel in the Hahn 20G that I have is a TD05H. The exducer looks to be the same as the wheel in a small 16G DSM turbo that I have here. [1.93" vs 2.17" for a TD06H]. What the turbine housing is is another question. I remember from my DSM days, Hahn used a 10 CM2 hsg on dsm 20G kits, which was said to be pretty slow.

Thanks.
Dave
 
#10 ·
After more thought, I think that Ill sell the Hahn 20G, and just do the Solo cat, some sort of catback, chopped stock air filter box, and maybe look for a better IC. And a tune, or course.

If it were my toy, I'd try it, but it's primarily Wifie's. I have my own money pits. I'm afraid that she'll gripe about the lag.

Thanks, all.
Dave
 
#11 ·
No need to do anything to the air box, it provides more than the car needs. Might make a little more noise, but that is it. I think you are making a wise decision. It is bad enough when you have to deal with any problems, but when the better half does, it becomes a nightmare. lol
 
#12 ·
Similarly, the stock exhaust is more than capable of serving the stock or mildly tuned engine - don't bother changing it unless your wife wants a louder car. Same with the IC.

A mild tune would give you significant improvement, though, without causing issues or lag. Suggest the basic Trifecta tune.
 
#13 ·
She'll be 64 soon, but even she thinks the car is too quiet. Even her stock '16 Jeep Renegade sounds better. LOL. We come from turbo'd DSMs, she liked the sound with aftermarket exh. [her 34K mile '99 Eclipse Spyder GST is for sale].

I like to keep all of the stock parts. I have a spare air box that already has the snouts cut off, so no harm done there. I am looking at the Trifecta budget tune, but I'd kinda like to have NLS.


Thanks, All.
Dave
 
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