Reducing turbo lag: What should my next step be?
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Things that do not get old: Rear end just a tidbit sideways, tires lightly spinning, while still gripping enough to accelerate, all the way through 2nd gear.
Things that keep me awake at night: A non-turbo M20 would be a lot more fun around a racetrack than this due to turbo lag. And this matters because it is my intention to do the occasional track day.
Currently I am running a T3/T4E .63 A/R hot side .60 A/R cold side journal bearing CX Racing turbo.
I sized it for 350hp at 15psi. I am currently at 12psi and am quite certain I am a little over the 300hp mark right now and extremely pleased with the performance on the top end.under full load, boost begins at 2800 rpm and 12psi is attained from 5000 rpm and up.
The power comes on just a bit too suddenly after a bit of lag. I am very new to the forced induction game so I do not know what to expect from my own car, but I would like to think that it doesn't have too much lag. BUT, its enough lag that I think it would be bothersome for track duty.
I want to reduce lag without hindering the top end pull too much. There are a few different things I have in mind, but I need some input and opinions on what might be the best move to take to achieve the goal.
A) Keep the same size+spec of turbo, but get a brand name version (Garrett/Turbonetics etc) concern: might spend $$$ for little to no difference
B ) Keep the same size+spec of turbo, but get a ball bearing version (Either CX Racing OR Garrett/Turbonetics)
concern: my research indicates that ball-bearing turbos are not rebuildable and are not as durable as journal bearing turbos, id hate to wreck one.
C) Go one size smaller CX Racing T3/T4E .50A/R cold side (has a more modern compressor design as well)
concern: might not reduce lag as much as id like it to, might lose more top end than id like to.
D)Get an adjustable cam gear to help the low end
concern: might not reduce lag as much as id like it to, might lose more top end than id like to.
E) Increase compression ratio to 10.5:1 and run low boost (7-8psi max)
concern: $$$$ + risky
F) Keep the turbo I have and do a stroker bottom end (2.8L), then make a decision after the larger refreshed bottom end.
concern: I love the idea of staying stock bottom end 2.5L so that I can go to any old junkyard and be up and running easily after even the most serious snafu
other small tidbits to try
G) weld a plate in my manifold to make it twin scroll and get a twin scroll turbo
concern: my research indicates 4 cylinders benefit from twin scroll more than a 6 or 8 cyl, may not be worthwhile?? idk
H) Electronic boost controller
concern: According to the Hallman boost controller website (what I have now), this boost controller is the shiz and is capable of outperforming some electronic units..... not sure if that is completely true
I) Get an adjustable BOV to ensure I am not losing any pressure while spooling (I have doubts about my used 1g DSM bov)
concern: might not actually be a problem
In the research I have done (ive said that twice now) the difference in spool time between a journal bearing and ball bearing turbo is ~0.2-0.3 seconds, on the other hand, I have seen a dyno comparing a properly sized journal bearing turbo vs a ball bearing turbo that was too large and the journal bearing turbo trumped it across the entire powerband.
I am currently leaning towards C, and trying the .50 A/R col side CX Racing turbo. It is the cheapest and easiest option to try.
Please share your thoughts and other ideas.
This is the kind of response I am looking for
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I like your plan to try C first. Don't worry about the ballbearing vs journal at this point. A properly sized turbo will go a longer way that just a different center section.
Your thoughts on the twin scroll not benefiting are somewhat correct. You need proper manifold design to completely benefit from a twin scroll. You isolate the engine pulses.
Stroking or changing the CR ratio will be very expensive and not help you in the way you think. Turbo sizing will still be important, probably more so. You can get there with tuning and turbo selection before digging into the bottom end.
The Hallman controller is fine. Very solid and simple. The only thing better would be if your engine management controlled it.
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That is sound advice,
All I have at the moment is a shot of the pressure vs RPM in 2nd gear
How abt a jpg with a mark where it reaches 11psi so we know when that is. Add AFR too.
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Smaller turbine housing == quicker spool == more flow restriction on the top end. The .63 hot side is not all that big, I'm guessing you've got a 4 banger?
My suggestion is to spend a bunch of time driving the car, learn to drive around lag. I had a T66 on my 95 Supra, a 20g on some of my DSMs, a GT3076r on my Legacy GT. You learn the car, where to keep RPMs when you think you may need them, downshift more, etc. Learn the car. If that doesn't do it for you, a smaller turbo is a great idea, start with the hot side.
I'm also a big fan of Hallman MBCs, and used them on all of my cars since around 1993. Except my current E92.
The Hallman will produce full boost at partial throttle, so an EBC may very well address your "boost comes on too fast" comment. Your tuner should be able take care of that.Ball bearing turbos are great, don't worry a thing about them. They can stand the abuse just as a non-bb can.
Take a look at the compressor maps of the various turbos you're interested in, take the time to understand them and they'll provide good information for making a decision, as well as what the CFM flow rate of your head is, etc.
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Smaller turbine housing == quicker spool == more flow restriction on the top end. The .63 hot side is not all that big, I'm guessing you've got a 4 banger?
My suggestion is to spend a bunch of time driving the car, learn to drive around lag. I had a T66 on my 95 Supra, a 20g on some of my DSMs, a GT3076r on my Legacy GT. You learn the car, where to keep RPMs when you think you may need them, downshift more, etc. Learn the car. If that doesn't do it for you, a smaller turbo is a great idea, start with the hot side.
I'm also a big fan of Hallman MBCs, and used them on all of my cars since around 1993. Except my current E92.
The Hallman will produce full boost at partial throttle, so an EBC may very well address your "boost comes on too fast" comment. Your tuner should be able take care of that.Ball bearing turbos are great, don't worry a thing about them. They can stand the abuse just as a non-bb can.
Take a look at the compressor maps of the various turbos you're interested in, take the time to understand them and they'll provide good information for making a decision, as well as what the CFM flow rate of your head is, etc.
he has the m20b25 I6 in his car
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Smaller turbine housing == quicker spool == more flow restriction on the top end. The .63 hot side is not all that big, I'm guessing you've got a 4 banger?
My suggestion is to spend a bunch of time driving the car, learn to drive around lag. I had a T66 on my 95 Supra, a 20g on some of my DSMs, a GT3076r on my Legacy GT. You learn the car, where to keep RPMs when you think you may need them, downshift more, etc. Learn the car. If that doesn't do it for you, a smaller turbo is a great idea, start with the hot side.
I'm also a big fan of Hallman MBCs, and used them on all of my cars since around 1993. Except my current E92.
The Hallman will produce full boost at partial throttle, so an EBC may very well address your "boost comes on too fast" comment. Your tuner should be able take care of that.Ball bearing turbos are great, don't worry a thing about them. They can stand the abuse just as a non-bb can.
Take a look at the compressor maps of the various turbos you're interested in, take the time to understand them and they'll provide good information for making a decision, as well as what the CFM flow rate of your head is, etc.
Thanks for the input! I appreciate your experience.
I will talk with my tuner
EDIT: I just talked with my tuner, he thinks I have Multiple Personality Disorder.
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Smaller turbine housing == quicker spool == more flow restriction on the top end. The .63 hot side is not all that big, I'm guessing you've got a 4 banger?
My suggestion is to spend a bunch of time driving the car, learn to drive around lag. I had a T66 on my 95 Supra, a 20g on some of my DSMs, a GT3076r on my Legacy GT. You learn the car, where to keep RPMs when you think you may need them, downshift more, etc. Learn the car. If that doesn't do it for you, a smaller turbo is a great idea, start with the hot side.
I'm also a big fan of Hallman MBCs, and used them on all of my cars since around 1993. Except my current E92.
The Hallman will produce full boost at partial throttle, so an EBC may very well address your "boost comes on too fast" comment. Your tuner should be able take care of that.Ball bearing turbos are great, don't worry a thing about them. They can stand the abuse just as a non-bb can.
Take a look at the compressor maps of the various turbos you're interested in, take the time to understand them and they'll provide good information for making a decision, as well as what the CFM flow rate of your head is, etc.
Tuner? Who needs a tuner?
THIS IS MEGASQUUUUUUUUUUIRT!!!!!!!!!!!!!
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You should really use the cheap EBC they have for megasquirt.
Anyways
TWIN SCROLL MAKES AN AMAZING AMOUNT OF DIFFERENCE.
Not only on spool up(sometimes between 200-400rpms sooner)
But TRANSIENT response. Which is what matters to me.
I hope you're happy to know that your car spools faster than a stock bugeye wrx...
But anyways I should really get this twincharged project done because you would love the whole no lag thing.
In reality I was hoping to see full boost by 3k, which for me is nothing..
sk8 or die
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