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Worthwhile to upgrade turbo with stock boost level?


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#1 kepico

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Posted 08 March 2020 - 03:52 PM

Just wondering what are thoughts on a turbo upgrade from 12a to 14g for "real world" use? I know it will flow a bit more cfm assuming a 10psi?

For example my current 88' Quest is completely stock other than exhaust (2.5 downpipe & 2.5 back to stock muffler - no cats)

It is a weekend cruiser only - no autocross\drags etc.

Back in the mid-nineties on my old quest a move to a 14g made some difference but I had a boost controller on that one and was running something like 15-16psi w\some other mods as well & I was able to get the 14g turbo new from the Mitsu dealer!

Currently I can't easily find a new 14g turbo anywhere - seems like I would have to send my 12a out to be fitted w\14g specs and some of the recommendations when I was looking last year of places to do it seem like they might be inconsistent (I can find both positive reviews and negative) and contacting them was an issue.

So not so sure about pulling my fine working 12a sending it out to be upgraded for who knows how long (and hopefully is done correctly) and what would be my benefit while still keeping stock 10psi boost?

If we are talking about 20hp at stock 10psi increase over the 12a than yeah I could see it being worthwhile but if we are talking little to no benefit at stock boost than I'll just keep what I got.

At any rate - Thanks for the thoughts!





#2 87redcat

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Posted 08 March 2020 - 05:36 PM

Boost control the stock 12A. You'll be surprised.
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#3 markhansenconquest

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Posted 08 March 2020 - 06:34 PM

pm ed u..

#4 BC_99

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Posted 08 March 2020 - 09:24 PM

If upgrading, why not go at least 16g for max gain in the safe real world stock limits of the fuel system? I cant say about the 14, but my 16g is a heck of an upgrade over the stock 12a. Now.. all that being said... you can find rebuildable 12a turbo cores cheap. Send it out for whatever upgrade you decide, and swap it out when you get it back and are ready, and you dont have any downtime between, and then you still have your good condition 12a as a spare...just in case. Turbo labs of America does a nice job for reasonable prices. The turbo exchange did my upgrade, but was a bit more expensive, however they are local to me so I didnt have to pay shipping both ways so the cost evened out.

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#5 Davey!

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Posted 09 March 2020 - 04:59 AM

Let me preface this by saying I run the stock 12a on stock boost, but I"m picking up a  "big" 16g. Most users will recommend the "big" 16g as its the best bolt on turbo for our cars while keeping stock fuel. If youre gonna upgrade the turbo, you might as well UPGRADE the turbo.  Basically mirroring BC_99 here.
To answer your question, with stock psi  might get a difference in spool times, faster or slower depending on your turbo. Why are you dead set on running stock boost? No judgement, just a question!

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#6 TexasQuest

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Posted 09 March 2020 - 11:22 AM

If your going to upgrade your 12a I would suggest going to a super 16g.
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View PostJohnnyWadd, on 04 March 2010 - 10:01 PM, said:

my shaft was big i dont know what your talking about.

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#7 JAinsworth

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Posted 10 March 2020 - 06:59 AM

The 12a is good to 15psi, after that it is not effecient. Going to a bigger turbo will increase the flow so 10 psi on a 12a isn't the same as 10 psi on a 16G.
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#8 importwarrior

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Posted 11 March 2020 - 05:15 AM

if anything go bigger on the exhaust side.
TD06 or TD05H at least...

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#9 kepico

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Posted 14 March 2020 - 08:57 AM

Thank you all for the replies! Guess I should clarify a bit on my OP & answer some of the questions posted.

First Quest I had back in the mid-90's taught me hard-way on limitations etc. on this vehicle, it had a 14G and upped boost and some other mods. At that time the 14G was the largest you could go w\out serious mods, as I said I bought it at the Mitsu dealer and was no big deal to order it and bolt on - at that time the 16G was considered needing fuel mods (pre internet days) so interesting to hear that it is thought you do not need fuel mods for it now days. I don't recall ever a "super" 16G or "regular" 16G, I just recall a "16G".

As for not wanting to increase the boost; well, I really want to keep the car as stock-appearing as possible, IE: I went to 2.5 exhaust all the way back but kept the OEM muffler\tips - so adding a boost gauge is a no-go (even in the stock location) and having owned several Turbo Dodges in the past with heavy mods & boost I know for a fact anything above stock using a boost controller you really should be able to correctly monitor boost levels with a "real" boost gauge at minimum. If they had a sort of upgraded ECM like the Turbo Dodges did with the Mopar Perf, ECM upgrade that had a set boost increase I would be using something like that, but nothing like that for these cars.


I know the larger turbo 14g\16g will flow more CFM even at the set 10psi, but what I was not sure was how that relates to a real world driving experience with a mostly stock car (other than the mentioned 2.5 exhaust) for how I drive it.

So the car is mostly a nice weather cruising \ going to car show vehicle, I don't think I have ever had it above 5k so high RPM breathing is a waste on me, most of the use I get is low-mid range acceleration .

A 16g if it adds power but needs more RPM and more boost to do it PLUS it moves the boost curve higher up meaning more lag than I am used to would be worthless for me, I'd likely be selling it off in short-order.

So I would like something that keeps the lag stockish or even spools up faster than stock, is all low-mid range power would be perfect for me.

And thats where I came to my original question if anyone knew; if I could find a 14\16g with stock PSI that spooled faster or the same as the 12a and added some decent torque numbers beyond the 12a that would be just right. I just don't think anyone has really bothered to ask something like that? I mean most people looking to upgrade I would imagine are planning on going further w\mods and or at least increasing PSI.

As for the exhaust side discussion of TD06\TD05H - I know the 12a has the TD05 housing so does the TD05H bolt up fine to the OEM size DP?

If I got a used 12\14g\16g and sent it out to Turbo Labs to be rebuilt would I be asking for a TD05H instead? And if so would that increase the lag\increase spool time because it is larger?

Sorry for all the questions and long post, just find this interesting to discuss!

Edited by kepico, 14 March 2020 - 09:05 AM.


#10 scott87star

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Posted 14 March 2020 - 12:18 PM

Quote

As for the exhaust side discussion of TD06\TD05H - I know the 12a has the TD05 housing so does the TD05H bolt up fine to the OEM size DP?

If I got a used 12\14g\16g and sent it out to Turbo Labs to be rebuilt would I be asking for a TD05H instead? And if so would that increase the lag\increase spool time because it is larger?

My flatty has an 06SL2 turbine in an OEM housing with the factory downpipe bolted to it, gutted of course, so go bigger than O5H.  The flatty still has boost threshold under 2000 rpm but now pulls hard as high as you want to rev it instead of dropping off at 4000 rpm.

In fact I'm tuning a clients Mighty Max with a G54bT in it as we speak, he initially had a stock turbo and was trying to run 20 psi and it was clear in the datalogs the turbine was WAY too small for that.  I talked him into having the turbine bored out for an 06SL2, he was reluctant because he was afraid of lag, first comment to me after he got it all reinstalled was "it doesn't lag at all!".  That and I've had to add over 30% more fuel to the VE table at 5000+ rpm, that means there is 30% more air FLOW and air flow is power.  You might not want to run more boost than stock but it will still flow more air than stock which is more power.
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#11 BC_99

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Posted 18 March 2020 - 06:45 PM

Scott brings up some great info....

Meaning all that extra air requires 30% more fuel in his example.

For your goals... have a stock td05-12a converted to a td05-16g. You will still have stock boost response with a noticeably harder "kick in the @$$".

BC

Edited by BC_99, 18 March 2020 - 06:46 PM.

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#12 kepico

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Posted 20 March 2020 - 03:07 PM

So I finally found the thread I saw last year that caused me to ask this; I'm not sure if it is ok to link other sites here so if it gets deleted search "DSM 14b and 16g horsepower difference"

https://www.dsmtuner...n-boost.324152/

I know it's not our car but in the link (first page really) it is thought that the stock PSI the smaller turbo will actually make more power (or the larger will feel "sluggish") now I know there may be differences between what they are talking as far as turbos but doesn't the same thought apply to us? One poster does bring up a point concerning the turbine side flowing better but unfortunately no one responds to that.

So if all that kind-of applies I am thinking I should maybe look into a 14g - now regarding the 14g is the stock turbine size for that TD05 or TD05"H"?

And if it is TD05, would there be a benefit to moving to a TD05"H" without increasing lag\losing spool due to the larger turbine side?

And finally what would get me there? Could I simply pick up a used 12a and send that out to the turbo re-builder and ask for a 14g\TD05"H"? Or do you have to start with a 14g??

#13 kepico

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Posted 20 March 2020 - 03:10 PM

Concerning that thread link\discussion I really don't want to create some heated debate - I just believe in the "research, research and some more research then do it once and do it right" philosophy so thought that might apply here to my thinking.

Thanks!!

#14 BC_99

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Posted 20 March 2020 - 06:24 PM

Ypur philosophy is right on in my very humble opinion.  

That said... I took a stock worn out sloppy junk 12A and sent it over to the rebuilder for a 16g upgrade.

It spool every bit as quickly as the 12a on the same engine. I kept my good condition 12a as a spare... but the extra punch from the 16g was very noticeable at stock boost. Now, I have moved beyond all of that and have the car running on megasquirt2 with the boost up to 16psi. It is a REALLY FUN car at that level.

I cant speak to the 14 vs 16 or td05 vs td05h. I haven't tried any of those variations. I went with what was suggested by people I trusted. I wasn't disappointed. Easy as that.

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#15 croquest87

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Posted 20 March 2020 - 07:07 PM

16G  is perfect.  Larger intercooler some hard piping larger injectors and perhaps some kind of fuel controler (maft set up).= fast starquest. Or stock about 13 psi max for longevity of things.Some say 15 but l have seen couple of these things blow head gaskets right around 15psi or less.

Note: refreshed motor highly recommended and not some 30+ year old p.o.s  on its last leg.lol

Edited by croquest87, 20 March 2020 - 07:18 PM.





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