A discussion about the Turbo

5389 Views 12 Replies 8 Participants Last post by Slammed2014Eco, Jan 19, 2016

Hazlitt777

Discussion Starter · Dec 30, 2015

Is it true that the turbo kicks in only around 1800 rpms?

And what is the highest one wants to rev the engine to keep it running well for many years....Is 4000 rpms now and then to accelerate acceptable?

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_MerF_

· #2 · Dec 30, 2015

No. Turbos don't "kick-in" at a set RPM. It's physics that drives how quickly the turbo can spool. If you are barely applying the throttle at 6k RPM your turbo isn't creating any pressure because there isn't enough HOT air to push the turbine. Likewise, if you have the throttle wide open from 800RPM and up, you will gradually build boost. You will certainly be out of vacuum immediately, and we can be at full boost (stock) well below 2k RPM (which is what I think you mean by "kick-in").

I don't believe in babying the engine to keep it running for years. Regular fluid changes and filter changes as well as properly allowing the engine to warm up before goosing it will do far more than keeping the revs below a certain threshold. That's just my personal opinion though, I have no data to say whether it is "better" for the engine or not.

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obermd

· #3 · Dec 30, 2015

In my ECO MT the turbo starts to spool at 1450 RPM and is completely spooled by 2500 RPM. Once spooled the turbo keeps running but the ECM controls how much boost it provides based on the torque needed to respond to the driver.

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lakemg

· #4 · Dec 30, 2015

obermd said:
In my ECO MT the turbo starts to spool at 1450 RPM and is completely spooled by 2500 RPM. Once spooled the turbo keeps running but the ECM controls how much boost it provides based on the torque needed to respond to the driver.

Do you have a boost gauge? Just curious how you know that it is completely spooled by 2500 RPM?

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obermd

· #5 · Dec 30, 2015

lakemg said:
Do you have a boost gauge? Just curious how you know that it is completely spooled by 2500 RPM?

I've monitored boost with my cell phone (torque light). In addition, several members did boost testing back in 2012 and determined the automatics are fully spooled at 2000 RPM and the manuals at 2500 RPM. I can monitor the start of boost by watching the instantaneous fuel economy drop right at 1400-1450 RPM.

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lakemg

· #6 · Dec 30, 2015

obermd said:
I've monitored boost with my cell phone (torque light). In addition, several members did boost testing back in 2012 and determined the automatics are fully spooled at 2000 RPM and the manuals at 2500 RPM. I can monitor the start of boost by watching the instantaneous fuel economy drop right at 1400-1450 RPM.

Thanks for the added info. I'll have to look into torque light.

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_MerF_

· #7 · Dec 30, 2015

obermd said:
I've monitored boost with my cell phone (torque light). In addition, several members did boost testing back in 2012 and determined the automatics are fully spooled at 2000 RPM and the manuals at 2500 RPM. I can monitor the start of boost by watching the instantaneous fuel economy drop right at 1400-1450 RPM.

Holy crap. That seems way high to me...are the 2015's also that high up to get full boost?

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obermd

· #8 · Dec 30, 2015

_MerF_ said:
Holy crap. That seems way high to me...are the 2015's also that high up to get full boost?

Remember our red line is 6500 and we're running a flat torque curve from 2000 RPM (auto)/2500 RPM (manual) to 4500 RPM. Boost is only called for as needed. Also, there is a lot of unused boost available in the Cruze's turbo as evidenced by my ECO MT basically being oblivious to altitude up to over 11,000 ft as long as I keep the RPMs above that 2500 RPM point.

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Alex V.

· #9 · Dec 31, 2015

I'm with Merf for the most part. My Cruze MT has seen 6,000 RPM many times over its now-57,000 miles and has yet to do anything but, generally, run and perform as well as I ever expected. No oil consumption (I mean *zero* over 5,000 miles), piston slap, fluid leakage, check engine lights, etc. It sees 4 grand a few times a week, 6 maybe a few a month, and I've topped it out through hard, long pulls to 100+MPH (pedal to the floor for a mile or more, 3,000 up to over 6,000 RPM without shifting) half a dozen times.

BUT, I have a list of do's and don'ts. Some people, including lifelong mechanics, will agree, and some people with the same spectrum of experience will disagree, but per its age and mileage my Cruze is running better than many others' and the man I gained a good portion of these habits from (father) is still driving a Suburban that passed 400,000 miles a few months ago on the original (heads have been off once for a bad injector misdiagnosed as a burned valve) 350 V-8 that has yet to burn more than a quart of oil between changes.

Upon start-up, let idle long enough for RPM's to drop before moving.
No more than 3,000 RPM until temp. gauge reaches full-warm.
Fuel of 89 octane or higher, with Seafoam in fuel every 10,000 miles.
First two oil changes (GM Dexos-1 syn.-blend oil) @ 2,000 and 6,000 miles, afterward started doing my own service with Valvoline full syn. @ 5,000 mile intervals. (I just changed to Schaeffer full syn. and plan to run 7,500 mile intervals with it unless something deters me.)
Always idle with as little load as possible (A/C/lights off) for a short time before shutting off.
No mods. Err, okay - if you consider the intake resonator bypass a mod, and I've actually put that back on recently and can't tell the difference. No fancy plugs, no tunes, aftermarket intakes, etc. I may mildly tune it some day, and do a muffler delete, but I'm not in a big hurry.

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Alex V.

· #10 · Dec 31, 2015

Oh, and also, the engine management system (whether it be more through boost, or cam advance, timing, etc.) doesn't bring in the power until 1,600-1,800 RPM, and bleeds off boost gradually after 2,500 or so to maintain the programmed power goal (aka, torque target), even under full acceleration. The engine is certainly still breathing and pulling all the way to redline, but the meat of the power curve is from 2,500-4,500.

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GM Master Tech

· #11 · Jan 9, 2016 (Edited)

Yup its all About keeping and maintaining the TQ power target.The factory target is 148 which is relatively reserved for the engine.And it can be hit under lower boost levels depending on your altitude and weather conditions.In other words enough boost to hit the TQ target.The max target can be raised to about 200 on 93 octane fuel.And there is a little room in the cam tables to play.This can hold the power in to higher RPM levels

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bsb2001ca

· #12 · Jan 19, 2016

What does the 1.4L turbo boost go up to? I thought I read 20 but someone may have said 30???

Sent from my iPhone using Tapatalk

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Slammed2014Eco

· #13 · Jan 19, 2016

bsb2001ca said:
What does the 1.4L turbo boost go up to? I thought I read 20 but someone may have said 30???

Sent from my iPhone using Tapatalk

I saw 20 when I had my boost gauge hooked up, I don't even think these turbos can come close to 30.

Edit: This was with a tune from trifecta btw, a lot of guys with efi live are running around 19 with better HP/Trq numbers

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