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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 07-02-2006, 04:57 PM   #1
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Default why my turbo is so laggy!

just wonder wat rpm range would ur turbo kick in?? my turbo kicks in ~4000rpm at 1st gear, ~3600rpm at 2nd and ~3200rpm at 3rd, the high the gear is the lower rpm it kicks in, i wonder if it's programing problem or exhaust problem, also very intersted in ur exhaust setup, pls let me know wat kinda piping u're using:

here is my set-up
1.6L engine
Greddy Exhaust Manifold
Greddy 16G turbine with Garret TD04 Compressor
customized 2.5" downpipe with flexpipe
2.5" in/out high-flow cat.
2.25" exhaust b-pipe with 1 resonator
2.5" single in, dual out dynomax SuperTurbo exhuast
3" intake pipe + 2.5" intercooler piping w/starion FMIC
ACT ProLite flywheel + HD clutch kit (1.8L convertion)
Walbro 255LPH fuel pump
BEGI 2025 RRFPR
305cc Supra injectors
NGK 2 degree cooler spark-plug
Greddy Emanage Ultimate with MAP + intake temp sesor
AFM removed
TurboXS RFL BOV
TurboSmart Boost controller set to 10PSI

so i guess my fuel system is more then enough to handle 10PSI but the turbo is kinda laggy, is it becos my 2.25 exhasut piping + cat + resonator which hold it back, or the IC piping is too big...or smthg else possibly?? look forward to see any subjection or solution, thz alot.
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Old 07-02-2006, 05:23 PM   #2
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hha, no comments to your questions. .. but man that engine bay looks nice!
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Old 07-02-2006, 05:46 PM   #3
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Yeah the greddy downpipe is no good... other than that your muffler is probably the biggest backpressure producer. Try removing your exhaust from the cat-back and see if it makes a difference. If it does, swap your muffler for a magnaflow.
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Old 07-02-2006, 06:01 PM   #4
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i replaced the greddy downpipe with a 2.5" already, but still looking for a replacement for the manifold. and wat rpm range would ur turbo kick-in?? i am not sure if it's da back pressure which holds it back, or just da intake piping and IC piping are too big so there is too much free space for the boost to fill up b4 it goes into the cylinders. anyways, i will try removing my cat and resonator and see if it makes difference, but do u guys use 2.25", 2.5" or 2.75" for exhaust piping??
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Old 07-02-2006, 06:25 PM   #5
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As fas as "~4000rpm at 1st gear, ~3600rpm at 2nd and ~3200rpm at 3rd"

The higher the gear, the more load the turbo sees, thus the reduced rpm spool. This is a perfect example of a turbo that's just a little too big for the engine. (For your desired traits)

As Hounos said, the smallish exhaust is creating backpressure which is not helping spool.
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Old 07-02-2006, 06:27 PM   #6
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Quote:
Originally Posted by OverRev
and IC piping are too big so there is too much free space for the boost to fill up b4 it goes into the cylinders.
If this were the case, the spool point would not change from gear to gear.



As stated above, for a quick and dirty exhaust test, just unbolt the sucka and take it around the block for a "the neighbors hate me test."

When your turbo spools earlier, quicker, and you feel that additional power at high RPM, you'll be

And last, nice underhood!!!

Last edited by UofACATS; 07-02-2006 at 06:36 PM. Reason: addition
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Old 07-02-2006, 06:51 PM   #7
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thz, i'll try it, and if the exhaust is the problem, then how big of piping should i use when making a new exhaust??
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Old 07-02-2006, 07:14 PM   #8
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It's not really the size of the piping that is the problem, except for the 2.25" piece. Your muffler is more restrictive than it needs to be. Get a straight through muffler like a magnaflow, I have one and it doesn't sound bad or too loud at all. Haven't been running the car much though with ECU problems.
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Old 07-02-2006, 07:27 PM   #9
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i see, i would try different muffler with 2.5" all the way, i guess i would keep the resonator but not da cat.
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Old 07-02-2006, 07:50 PM   #10
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exactly.
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Old 07-03-2006, 08:47 AM   #11
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hmm, i just found out the problem with help of my frd, red90 who drives a turbo miata with simular setup as my, the reason it's laggy is very very stupid, on the ultimate there is an option for u to update ur injector size, so i set it to 305cc instead of the origianl 210cc, and the result is that the ultimate pulls the ign. timing back crazily, it's almost like 8-10 deg. lower thru-out the entire map, that's y it's laggy and not making pwr. imagine setting ur ign timing to 0 deg on the pully and dat's y it runs like sh*t.
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Old 07-03-2006, 02:21 PM   #12
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well my Greddy when I had one didnt hit full boost in 1st gear until about 4000rpm ( 12psi ) and that was with a 2.5in dp and full 2.5in exhaust. Thats just the nature of that turbo....its got a large turbine a/r and it takes longer than a T25 to get into boost. Thats just how it is....
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Old 07-03-2006, 03:17 PM   #13
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deez and dose.......

good luck man
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Old 07-05-2006, 11:57 PM   #14
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Hmmm...that doesnt make sense.If you put in a bigger injector size, it will LESSEN the airflow value the ecu sees to trim back the fuel. The less the load, the more advanced the timing. not sure how a low load would retard timing...
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