OOOLD timer with new school questions regarding boost...

[boostd4]

I'm picking up a 90 GSX that is just about setup the way I want it and am getting back in the DSM game. I had a few 1G's and a 2G about 15 years ago that I played around with and just searching around the forums, it seems like I've missed quite a lot..

"In my day..... " (hah), we used to run 15psi on pump gas and 20-25psi (maybe) on race gas with upgraded turbochargers. I know this question is super vague, but everywhere I look people are running 30+psi and I'm caught off guard. Is there something else going on allowing these levels of boost? I was assuming they were using crazy new turbos with super efficient turbine wheels/housings, but I see people running WAY over 20psi on regular old 16G's, etc...

What kind of boost levels are safe considering my setup?

My setup:
90 GSX
Built 6 bolt (eagle h beams, wiseco pistons, stock compression 160-164psi comp across) no balance shafts
Mitus MLS head gasket
Stock ported/refreshed head with stock valves, cams.
Ported 2G exh manifold
PTE GT3071R with external wastegate rerouted
FIC 650's, AFPR, walbro 255 (plan to run E85, may end up with larger injectors)

Is everyone just cranking boost until power plateaus? We used to freak out about backpressure and EGT's, has something changed?

Thanks!

-Adam

 

[Pipnorcali]

Well back in the day most people had a safc n 650cc now we have dsmlink n aem so they can control fuel n spark and use larger injectors. E85 is new on the scene since you've been gone

 

[boostd4]

I was leaving the scene when link was coming in, sure. But AEM was around and bigger injectors.. We weren't limited by fuel or engine management (though things are way better now), but it was "assumed" that there was some mechanical limit to how much boost you could run.. what I mean is... 30+psi through a TD05h or through a stock exhaust manifold would just back up air into the combustion chambers... or lift the head and blow a head gasket... or cook valves due to super high EGTs. I guess what I'm getting at is... I'm guessing through experience the community has learned that these are myths? Or exposed higher limitations?

 

[rough]

Tuning, the cure/fix all! Want to throw more boost? You will need to tune! ECMLink is a favorite here!
Just with what you have now, with a tune, you will squeeze more power and be much safer doing it!

Want to upgrade to that 16g great! If you don't tune you will have all types of issues and the car will run badly!

You got a nice setup!

Get yourself a boost gauge, AFR Gauge, Pyrometer gauge,
A way to control boost, manual or electric boost controller.
Tuning software
Make sure everything is running perfect "standard maintenance"
Then start tuning and learning![DOUBLEPOST=1412609364][/DOUBLEPOST]There is a mechanical limit to how much boost the turbo can provide. The T25 chokes out around 15/16 psi where other turbo's like 16g's can do 25PSI+
A tuned Stage 1 T25 will tear apart a non-tuned 16g .

 

[nytescion]

I wouldn't run higher any than 18psi without a wideband/safc (or some other tuning device) and someway to check injector duty cycles. But thats just me.

 

[oren hughbanks]

Yeah I gotta agree tuning has come a huge way in the last few years. Higher octane fuel is a must for sure pump gas is just limited on potential. I think any turbo can do high levels of boost, but then you start falling out of the efficiency range. Where that little turbo is heating up the air so much, it just can't cool down in time. It also factors into how much air it will flow. Sure it can do 25psi, but that small t25 just Dosent pump the cfm of air to make more power.
Turbos are getting crazy efficient too, with all the help of modern machining to design more efficient compressor wheels, out of better quality material.

 

[jakelandry]

Generally speaking, we just have had more people push things harder over the past 15 years and report their info back here. People quit worrying about post turbine pressure and egt's and just pushed their cars. Whoever diddnt blow up came back here and said I've made x airflow for 3 years now with x mods. People copied and tweaked the info till we worked out what timing the cars liked and what boost levels achieved what. Information is more readily available than it has ever been.

 

[boostd4]

It's been a while since I've read a compressor map - I found this on garrett's website for the GT3071R:

http://www.turbobygarrett.com/turbo...rbogroup/performance_maps/700382-3&20comp.jpg

If I'm reading this correctly, it looks like it's at the end of the most efficient island when it's pushing 25-27psi and moving about 37lbs/min. Can anyone confirm? What does 37lbs/min translate into in terms of horsepower on a 4G63T with stock cams?

 

[rough]

I could be way off, but I've generally thought of 1 PSI = 10 Horses so 25-27 psi + 140hp = 250-270+140 = Approx HP - Drive train/non tuned. = Total output.

I would guess if your pushing 25-27 psi you are about 350whp'ish.

 

[Marchev]

One thing that stands out on your mod list is you don't have upgraded head studs. Anything over 20psi boost and you might lift the head of the block with stock bolts. Look into arp.

 

[Dhan]

I got into the DSM scene four years ago (came from Toyota MR2s and Mazda 323 GTXs) so haven't been around long. First thing I noticed was that anything below 20psi is weak sauce (relatively speaking).
My biggest advice would be to invest in the DSM specific ECMlink (used to be DSMlink, but when the company started supporting the Evo, they changed the name). This streamlines tuning, as you start with the factory tune and build off that. Unlike say AEM, where just getting the car to start and idle is a process. You can literally install ECMlink and a wideband, and start making adjustments. You can even simulate the O2 sensor using a wideband now.

ECMlink seems have been a big step to allowing pretty much anyone with half a brain to install bigger injectors/pump, an AFPR, crank up to 20psi, and go. Then you throw in E-85, eliminate the MAF and go with speed density, front mount intercooler (FMIC) and you've got a drag machine that'll comfortably take you to and from the track.

Jakelanddry's comment seems pretty accurate when you see the dates attached to a lot of the posts in these forums. Through trial and error and other people's wallets, the road has been paved to making a fire-breathing DSM using all sorts of configurations. A fella on here named 99gst_racer even created a compound turbo setup for his DSM. The combinations and various setups are endless. Almost everything's already been done.

Along with ECMlink, I would consider adding a FMIC to your list, along with a wideband (Innovative LC-2 is a tried and true unit) to monitor EGTs. Goes w/o saying, but a larger diameter turbo-back exhaust would probably go a long way to unlocking power. I have the stock exhaust system back on my AWD Talon for emissions (small 16g at about 18psi) and you can definitely feel the difference.

 

[boostd4]

Got everything on the list except a WB02 so far. I bought this car, if you're curious:

http://www.dsmtuners.com/threads/1990-eclipse-gsx-super-clean-built.478928/

 

[Dhan]

Wow. Definitely a well put together unit!

Hope you get the time to use it.

 

[rough]

Incredible 1g!

 

[bryanwheat]

I could be way off, but I've generally thought of 1 PSI = 10 Horses so 25-27 psi + 140hp = 250-270+140 = Approx HP - Drive train/non tuned. = Total output.

I would guess if your pushing 25-27 psi you are about 350whp'ish.

There is no direct correlation between boost pressure and horsepower because different size turbo's produce different amount's of airflow at the same pressure. A smaller turbo will produce a less dense charge, which will equal less power per psi than a larger turbo. One turbo might make 350 horsepower at 25 psi, and one might make 500 horsepower.

 

[boostd4]

From my past experience with MR2's, a 3071R on a 2.0L motor should be good for high 300's at 25psi or less. With the crazy boost everyone seems to run, a few people think I should be able to get 425-450whp, more with cams... I guess we'll find out! I need a set of 1000cc+ injectors and a bigger fuel pump so i can run E85 first.

 

[mitsubishikid]

There is no direct correlation between boost pressure and horsepower because different size turbo's produce different amount's of airflow at the same pressure. A smaller turbo will produce a less dense charge, which will equal less power per psi than a larger turbo. One turbo might make 350 horsepower at 25 psi, and one might make 500 horsepower.

Yeah and you have to take into account exhaust size, inter-cooler size, if any porting was done, compression ratio, IC piping,etc
also weather or not other mods were done in addition to the bigger turbo, it could be contributing to higher... or lesser hp gains.

 

[Kevin Jewer]

Some of the major changes in the last 15 years include better turbos, better intercoolers, better tuning solutions, engine parts, cams, etc, as mentioned. The rest is that all of the old fears are all old news now. Everything has been tried, all of the parts have been broken, the limits have been found, and the myths have been busted. Now you can easily build a setup to do what you want, tune it properly, and go out and turn it up without expecting catastrophic failure every time you go into boost. Though there is a lot that I miss about those days. It was exciting for sure.