Turbo Help

[csmwiese]

I am new to DSM cars and have done some searching and need some tips with the car.

I purchased a 1998 Eclipse GSX Automatic for my son (I have other turbo cars 1987 Grand National & 1991 Syclone but no expert..), my question is....if we set the boost to 15,16,17 or 18 it will hit that number then drop off to around 13-14 psi. Now I do not have this problem with my other cars, I'm thinking that when the wastegate opens the turbo can not keep up that level of boost. I was thinking that we just get a larger turbo 16g or 20g, but still only set the boost at a safe level for the car?? That way then the wastegate opens, the turbo will be able to maintain the level of boost set. I could be wrong in my thinking and most likely am. Please give me your thoughts. Also you see turbos in all price ranges....$150-$350, what is a good/decent quality turbo that will not brake the bank...below $300

This is what we have done to the car:

Hallman Pro RX MBC

Upgraded Turbo Elbow

3" downpipe w/ cat delete

3" catback

Rear O2 sim

Cold Air Intake

2.25" Intercooler Piping

Vented Blow Off Valve (don't remember brand)

SMIC Rear Vent Mod

VDO Boost Guage

The car is still new to us and we have only driven it less than 20 miles as my son is still only 15 years old. We have done every mod listed above.

Here are a couple of my other cars below

Thanks, Clint

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

 

[JusMX141]

Factory T25's are too small and have too light of a wastegate spring. You can put a stiffer actuator on, but at 18psi the turbo is well out of it's efficiency range so you'll shorten it's life drastically.

Unfortunately you're not going to find any new turbos for under $300 that are worth their own weight in dog shit, so for now you'll just have to live with the problem or set the boost to a level where it doesn't spike so drastically.

 

[2gmitsueclipse]

A larger turbo is also going to be met with the need for more upgrades as well. 16g or 20g will need the install kit as you a 2g and they will not just "bolt on". You will also need more fuel and a way to control that fuel.

One other thing......Recirculate that BOV! that air bypasses the MAS and is already accounted for. You will be running rich.

 

[turbotom]

A 16g or 20g is a huge difference from the hair dryer T25 and guys running 350hp on 16gs, so that's your best bet. You can get a used 16g for $300 or less and worth the money.

 

[csmwiese]

My other turbo cars I use a adjustable wastegate actuator to set the boost, this is my first time with a MBC. Would an adjustable wastgate actuator keep the boost in place and not have the drop off? Or would a larger turbo to the trick?

Clint

Is my thinking wrong.....18psi from a T25, 16g or 20g is still just 18psi (I know these larger turbos are capable of producing even more) but the 16g and 20g can hold it there once the wastegate opens. unlike the T25 that when the wastgate opens it can't keep up.

Thoughts?

Clint

 

[Seouljer]

18 psi from a t25 vs 18psi from a 16g is not the same. The 16g flows more air so with 18 pounds on the 16g you have more air and more power potential.

 

[WES_393]

It's not about boost pressure, but about airflow. The stock T25 will max out at around 220 CFM while a 16g can flow over 500 CFM. So a 16g at 20psi is flowing about twice as much air as a T25 at 20psi.

The T25 simply isn't capable of feeding these engines at higher RPM. You can crank up the boost all you want, but the turbo's compressor just isn't very efficient. The turbine housing is also very small which can restrict exhaust flow in the higher RPM ranges. A 16g would hold it's boost much better than a T25. But even a typical 16g won't maintain higher boost pressure at high RPM. With my small 16g, the MBC is set to around 25psi but boost falls off to around 18 by redline.

 

[csmwiese]

OK, So would 20g be to large for my setup then?

Clint

 

[Nicklepage1010]

Without proper fuel management that 20g will be too big. Buy him dsmlink for x mas

Coincidentally, my dad owns a viper (2006) and I also have a 98 gsx

 

[1983gsp]

http://www.dsmtuners.com/forums/fre...tions/113858-venting-your-bov-atmosphere.html
http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/273778-turbo-should-i-get.html
Tech Guide - DSMtuners

 

[csmwiese]

I guess a 16g would be fine for our setup, our goal is to be able to run a 13.99.

There is a guy close to us that is parting out his 1995 GST and has a DSMLinked ECU with no cables (was not sure if it would work in our 1998 GSX) and there is a shop about 1 hour away that tunes these cars and has an all wheel dyno.

Would the 1995 DSMLinked ecu work in the 1998?
Any thoughts on the 13.99 goal?
was also going to chip the TCU for firmer shifts.

Clint

Thank You 1983gsp for the links.

 

[WES_393]

Yes, you will just have to invert the CAS signal (literally one click of the mouse in DSMLink). Maybe some other things I'm forgetting, but it should be very easy.

13.99 should be very doable with a 16g and DSMLink, given all the supporting mods are correct. I ran 14.37 with horrible tires, very low 5* peak timing, and DA of 8,000ft. With a proper tune, decent tires, and your altitude, you should be able to easily pump out 13's. I would definitely look into programming the TCU to upshift with 100% line pressure and maybe install a shift box.

 

[Black-Out]

I guess a 16g would be fine for our setup, our goal is to be able to run a 13.99.

There is a guy close to us that is parting out his 1995 GST and has a DSMLinked ECU with no cables (was not sure if it would work in our 1998 GSX) and there is a shop about 1 hour away that tunes these cars and has an all wheel dyno.

Would the 1995 DSMLinked ecu work in the 1998?
Any thoughts on the 13.99 goal?
was also going to chip the TCU for firmer shifts.

Clint

Thank You 1983gsp for the links.

13.99 is a pretty low goal- you may be able to get close to that with a good launch, and good supporting mods and a tune on the stock turbo- Correct me if I'm wrong but didn't the autos run high 14's un touched, factory fresh? I know the T25 is tiny but it should get you close if the car is tuned well and the technique is there. All that aside a 16G will flow enough to get you well into the 12's, again, if it's tuned well and all the supporting mods are in place......If you haven't done any fuel supporting mods (atleast a walbro 190, 255lph preffered, 550cc injectors, a tune with some kind of management or atleast a Apexi Super AFC, turbo back exhaust, K&N filter) Then your best bet is not to exceed 14-15psi boost or you will risk running pretty lean on a 16g- Especially if it's an evo 16g- Just proceed with caution, if you arent upgrading with a systematic approach you can easily get into trouble when you can't keep the fingers off the boost control knob.......


William-

 

[95DsManiac]

Hey Clint. as for your 13.99 goal, like black-out stated is pretty of a low goal. usually its like 300hp or 12s.

"This is what we have done to the car:

Hallman Pro RX MBC

Upgraded Turbo Elbow

3" downpipe w/ cat delete

3" catback

Rear O2 sim

Cold Air Intake

2.25" Intercooler Piping

Vented Blow Off Valve (don't remember brand)

SMIC Rear Vent Mod

VDO Boost Guage"

your on a good path. next i would port out the o2 housinf or get an evo 3 o2 housinf to open up the horsepower you already have. i have a 2.5" ss tubular o2housing for sale if you want it pm me. your on the right path though for going 13.99.
http://www.dsmtuners.com/forums/bolt-tech/37389-13-sec.html check that out. some guy wants the same goal.

i honestly believe you could do it with 3" turbo back, mbc, 1g bov, boost gauge, 2.5" o2 housing, good tires, good driver, 3" intake, 16 psi of boost on stock t25, take out unwanted wait, or if you want to get there easily and have room for more power if wanted i would go with, 14b or small 16g, 550-650 cc injectors, dsmlink or saf-c, walbro 190 or 255 if you go 255 you would need afpr (190 would be good), stock smic would be fine but fmic would be better, and walla there you go. Higher octane gas would make it a little easier too.

 

[csmwiese]

I guess we could be there already (13.99), what I was thinking about the turbo was not just more HP but eliminate that boost drop off (hits set boost the drops to 13-14). With my Grand National I use an adjustable wastegate actuator to set the boost and it hits 20psi and holds it until I let off the throttle...that's what I was looking for on this car (not 20psi) but maybe it's normal to drop boost on these cars.

Clint

 

[TurboAnything]

The boost is falling off because the turbo is so small it can not supply enough air at high engine speed. There is no way to get it to hold more no matter what you try. Just pick up a 16g and a install kit and you can hold 20psi to redline.

 

[csmwiese]

Thanks Guys.

Clint

 

[007jimmy]

If you do decide on a 16g make sure you are covered on the fuel supply side and take the proper steps to help prevent boost creep. Common problem on those turbos with such a free flowing exhaust that you have.

 

[n0de]

Yes, a t25 cannot flow enough air at higher rpms. The engine is litterally sucking more air then the turbo can push out to maintain 18psi after a certain rpm.

for 12's/13's Do this.

-evo 3 big 16g turbo
-550cc injectors
-either one of these combos

- 255 walbro fp w/ afpr
- 190lph fp stock fpr

-replace your fuel filter (I do this on any new performance car i buy, its good practice)
-either one of these

-ecmlink (this management system will be tunable all the way to the single digit 1/4 mile times)
-S-AFC2 (This is a cheaper controller but is limited. You can control your injectors up to 680cc injectors)

-Megan downpipe to free up some restriction.

The manual boost controller you have is fine, I know you're used to controlling boost another way but the MBC is just as effective and simple.

Depending on which combination you pick, you can probably source all of the pieces for $700-$1000

Now, if you just upgraded the turbo then you would have to keep boost relatively low

 

[csmwiese]

Thanks Again Guys.

Clint